- [Fe4] and [Fe6] Hydride Clusters Supported by Phosphines: Synthesis, Characterization, and Application in N2 Reduction
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Multiple iron atoms bridged by hydrides is a common structural feature of the active species that have been postulated in the biological and industrial reduction of N2. In this study, the reactions of an Fe(II) amide complex with pinacolborane in the presence/absence of phosphines afforded a series of hydride-supported [Fe4] and [Fe6] clusters Fe4(μ-H)4(μ3-H)2{N(SiMe3)2}2(PR3)4 (PR3 = PMe3 (2a), PMe2Ph (2b), PEt3 (2c)), Fe6(μ-H)10(μ3-H)2(PMe3)10 (3), and (η6-C7H8)Fe4(μ-H)2{μ-N(SiMe3)2}2{N(SiMe3)2}2 (4), which were characterized crystallographically and spectroscopically. Under ambient conditions, these clusters catalyzed the silylation of N2 to furnish up to 160 ± 13 equiv of N(SiMe3)3 per 2c (40 equiv per Fe atom) and 183 ± 18 equiv per 3 (31 equiv per Fe atom). With regard to the generation of the reactive species, dissociation of phosphine and hydride ligands from the [Fe4] and [Fe6] clusters was indicated, based on the results of the mass spectrometric analysis on the [Fe6] cluster, as well as the formation of a diphenylsilane adduct of the [Fe4] cluster.
- Araake, Ryoichi,Sakadani, Kazuki,Tada, Mizuki,Sakai, Yoichi,Ohki, Yasuhiro
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- Synthesis and Characterization of Bioinspired [Mo2Fe2]–Hydride Cluster Complexes and Their Application in the Catalytic Silylation of N2
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The hydride-supported [Mo2Fe2] cluster complex {Cp*Mo(PMe3)}2{FeN(SiMe3)2}2(H)8 (2 a; Cp=η5-C5Me5) and its [Mo2Mn2] congener 2 b were synthesized from the reactions of Cp*Mo(PMe3)(H)5 (1) with M{N(SiMe3)2}2 (M=Fe, Mn). The amide-to-thiolate ligand-exchange reactions of complex 2 a with bulky thiol reagents (HSR; R=2,4,6-iPr3C6H2 (Tip), 2,6-(SiMe3)2C6H3 (Btp)) furnished the corresponding hydride-supported [Mo2Fe2](SR)2 cluster complexes. The [Mo2Fe2] clusters served as catalyst precursors for the reductive silylation of N2 and yielded ≈65–69 equivalents of N(SiMe3)3 relative to the [Mo2Fe2] clusters. Treatment of complexes 2 a and b with an excess of CNtBu resulted in the formation of dinuclear Mo?Fe and Mo?Mn complexes, which indicated that the [Mo2M2] cores (M=Fe, Mn) split into two dinuclear species upon accommodation of substrates.
- Ohki, Yasuhiro,Araki, Yuna,Tada, Mizuki,Sakai, Yoichi
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- Conversion of dinitrogen to tris(trimethylsilyl)amine catalyzed by titanium triamido-amine complexes
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By using a triaryl-Tren ligated titanium dinitrogen complex, K2[{(Xy-N3N)Ti}2(μ2-N2)] (3), prepared by two-electron reduction of [TiCl(Xy-N3N)] (1-Cl) under N2 atmosphere, catalytic fixation of molecular nitrogen to form tris(trimethylsilyl)amine was achieved under ambient conditions with a turnover number (TON) of up to 16.5 per titanium atom.
- Ghana, Priyabrata,Van Krüchten, Franziska D.,Spaniol, Thomas P.,Van Leusen, Jan,K?gerler, Paul,Okuda, Jun
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- Evaluating Metal Ion Identity on Catalytic Silylation of Dinitrogen Using a Series of Trimetallic Complexes
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We report catalytic silylation of dinitrogen to tris(trimethylsilyl)amine by a series of trinuclear first row transition metal complexes (M = Cr, Mn, Fe, Co, Ni) housed in our tris(β-diketiminate) cyclophane (L3–). Yields are expectedly dependent on metal ion type ranging from 14 to 199 equiv. NH4 +/complex after protonolysis for the Mn to Co congeners, respectively. For the series of complexes, the observed trend for the number of turnovers as a function of metal ion type is Co > Fe > Cr > Ni > Mn, consistent with prior reports of greater efficacy of Co over Fe in other ligand systems for this reaction.
- Eaton, Mary C.,Knight, Brian J.,Catalano, Vincent J.,Murray, Leslie J.
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- Synthesis of Dinuclear Mo?Fe Hydride Complexes and Catalytic Silylation of N2
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Two transition-metal atoms bridged by hydrides may represent a useful structural motif for N2 activation by molecular complexes and the enzyme active site. In this study, dinuclear MoIV-FeII complexes with bridging hydrides, CpRMo(PMe3)(H)(μ-H)3FeCp* (2 a; CpR=Cp=C5Me5, 2 b; CpR=C5Me4H), were synthesized via deprotonation of CpRMo(PMe3)H5 (1 a; CpR=Cp*, 1 b; CpR=C5Me4H) by Cp*FeN(SiMe3)2, and they were characterized by spectroscopy and crystallography. These Mo?Fe complexes reveal the shortest Mo?Fe distances ever reported (2.4005(3) ? for 2 a and 2.3952(3) ? for 2 b), and the Mo?Fe interactions were analyzed by computational studies. Removal of the terminal Mo?H hydride in 2 a–2 b by [Ph3C]+ in THF led to the formation of cationic THF adducts [CpRMo(PMe3)(THF)(μ-H)3FeCp*]+ (3 a; CpR=Cp*, 3 b; CpR=C5Me4H). Further reaction of 3 a with LiPPh2 gave rise to a phosphido-bridged complex Cp*Mo(PMe3)(μ-H)(μ-PPh2)FeCp* (4). A series of Mo?Fe complexes were subjected to catalytic silylation of N2 in the presence of Na and Me3SiCl, furnishing up to 129±20 equiv of N(SiMe3)3 per molecule of 2 b. Mechanism of the catalytic cycle was analyzed by DFT calculations.
- Ishihara, Kodai,Araki, Yuna,Tada, Mizuki,Takayama, Tsutomu,Sakai, Yoichi,Sameera,Ohki, Yasuhiro
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- N2 Silylation Catalyzed by a Bis(silylene)-Based [SiCSi] Pincer Hydrido Iron(II) Dinitrogen Complex
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The bis(silylene)-based SiC(sp3)Si pincer ligand N,N′-bis(LSi:)dipyrromethane [SiCH2Si] (L1; L = PhC(NtBu)2) with a C(sp3) atom anchor was synthesized, and its coordination chemistry to iron was studied. Two novel iron hydride complexes, [SiCHSi]Fe(H)(N2)(PMe3) (1) and [SiCHSi]Fe(H)(PMe3)2 (2), were synthesized in the reaction of L1 with Fe(PMe3)4 via C(sp3)-H bond activation under different inert atmospheres (N2 and argon). To the best of our knowledge, 1 and 2 are the first examples of a bis(silylene)-based hydrido pincer iron complex produced through activation of a C(sp3)-H bond. At the same time 1 is also the first example of a TM dinitrogen complex supported by a bis(silylene) ligand. The interconversion between 1 and 2 was achieved and monitored by operando IR and 31P NMR spectra to understand the transformation from 1 to 2 from the viewpoint of kinetics. To our delight, 1 could effectively catalyze silylation of dinitrogen and gave the highest turnover number so far among all the Fe-catalyzed N2 silylation systems at room temperature and under atmospheric dinitrogen.
- Li, Shengyong,Wang, Yajie,Yang, Wenjing,Li, Kai,Sun, Hongjian,Li, Xiaoyan,Fuhr, Olaf,Fenske, Dieter
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- Merging Pincer Motifs and Potential Metal–Metal Cooperativity in Cobalt Dinitrogen Chemistry: Efficient Catalytic Silylation of N2 to N(SiMe3)3
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Using a pyrazolate-bridged dinucleating ligand that provides two proximate pincer-type PNN binding sites (“two-in-one pincer”), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end-on μ1,2-bridging N2; in THF 4 is labile and undergoes temperature-dependent N2/triflate ligand exchange. These pyrazolate-based systems combine the potential of exhibiting both metal–metal and metal–ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N2 into N(SiMe3)3 (using KC8 and Me3SiCl), yielding up to 240 equiv N(SiMe3)3 per catalyst.
- Dechert, Sebastian,Demeshko, Serhiy,Gupta, Sandeep K.,Li, Ming,Meyer, Franc
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- N-Substituted hexamethyldisilazanes as new substances for the synthesis of functional films in the system Si-Ge-C-N-H
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N-Organylbis(trimethylsilyl)amines of the general formula RN(SiMe 3)2 (R = Me3Si, Et3Ge) were synthesized by reaction of sodium bis(trimethylsilyl)amide with the corresponding trialkylsilyl(germyl) halide. Their IR, UV, and 1H, 13C, and 29Si NMR spectra were studied, and saturated vapor pressures and thermal stabilities were determined. The possibility of using the RN(SiMe3)2 compounds as precursors in chemical vapor deposition of films with specified composition was estimated by thermodynamic modeling. Pleiades Publishing, Ltd., 2011.
- Sysoev,Nikulina,Kolontaeva,Kosinova,Titov,Rakhlin,Tsyrendorzhieva,Lis,Voronkov
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- Synthesis and Reactivity of Iron– and Cobalt–Dinitrogen Complexes Bearing PSiP-Type Pincer Ligands toward Nitrogen Fixation
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Iron– and cobalt–dinitrogen complexes bearing PSiP-type pincer ligands are newly designed and prepared, on the basis of our previous proposal that iron– and cobalt–dinitrogen complexes bearing trimethylsilyl ligands are key reactive intermediates in the c
- Imayoshi, Ryuji,Nakajima, Kazunari,Takaya, Jun,Iwasawa, Nobuharu,Nishibayashi, Yoshiaki
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- New P-S-N containing ring systems. Reaction of 2,4-(naphthalene-1,8-diyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide and its 4-methoxynaphthalene derivative with hexamethyldisilazane
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Reaction of 2,4-(naphthalene-1,8-diyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide 1 with hexamethyldisilazane (hmds) in acetonitrile gave the N,N′-bis(trimethylsilyl)acetamidinium salt of the [(C10H6)P(S)(NHSiMe3)SP(S)2] - anion 2, a product of P2S2 ring cleavage, together with the new thiazaphosphetidine (C10H6)P(S)SN(SiMe3)P(S) 3. Analogous (methoxy derived) products to 2 (2a, 2b) and 3 (3a) were obtained when 2,4-(4-methoxynaphthalene-1,8-diyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide 1a was used instead of 1. When the reaction of 1 with hmds was performed in dichloromethane a mixture of the products was obtained, from which the hexamethyldisilazan-2-ium salt of the anion of identical structure to that in 2 has been isolated. No reaction occurred when a solventless system was used. The new compounds were studied spectroscopically (one- and two-dimensional NMR, IR spectroscopy) and by X-ray crystallography (3, 3a and 4).
- Kilian, Petr,Marek, Jaromir,Marek, Radek,Tou-In, Jioi,Humpa, Otakar,Novosad, Josef,Woollins, J. Derek
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- Dinitrogen Functionalization Affording Chromium Hydrazido Complex
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A series of trinuclear and dinuclear Cr(I)-N2 complexes bearing cyclopentadienyl-phosphine ligands were synthesized and characterized. Further reduction of the Cr(I)-N2 complexes generated anionic Cr(0)-N2 complexes, which could react with Me3SiCl to afford the first chromium hydrazido complex from N2 functionalization. These complexes were found to be effective catalysts for the transformation of N2 into N(SiMe3)3.
- Yin, Jianhao,Li, Jiapeng,Wang, Gao-Xiang,Yin, Zhu-Bao,Zhang, Wen-Xiong,Xi, Zhenfeng
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- N2 Reduction into Silylamine at Tridentate Phosphine/Mo Center: Catalysis and Mechanistic Study
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Transition-metal-catalyzed formation of silylamine from N2 (i.e., dinitrogen reduction) is achieved here using a tridentate phosphine/Mo system. Starting from the Mo(0) dinitrogen complex, stepwise reactions with chlorosilanes allowed the synthesis of the Mo(IV) hydrazido complex. Further reaction with two electrons resulted in the N-N bond splitting and formation of bis-silylamide and Mo(IV) nitrido complex. Facile addition of chlorosilane on the nitrido complex was observed to lead to the Mo(IV) imido complex. The four complexes (i.e., Mo(0) dinitrogen, Mo(IV) hydrazido, nitrido, and imido) perform equally well in the catalytic process between stoichiometric amounts of K and chlorosilane under N2 and are thus likely catalytic intermediates.
- Liao, Qian,Saffon-Merceron, Nathalie,Mézailles, Nicolas
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- Fe-Catalyzed Conversion of N2 to N(SiMe3)3 via an Fe-Hydrazido Resting State
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The catalytic conversion of N2 to N(SiMe3)3 by homogeneous transition metal compounds is a rapidly developing field, yet few mechanistic details have been experimentally elucidated for 3d element catalysts. Herein we show that Fe(PP)2(N2) (PP = R2PCH2CH2PR2; R = Me, 1Me R = Et, 1Et) are highly effective for the catalytic production of N(SiMe3)3 from N2 (using KC8/Me3SiCl), with the yields being the highest reported to date for Fe-based catalysts. We propose that N2 fixation proceeds via electrophilic Nβ silylation and 1e- reduction to form unstable FeI(NN-SiMe3) intermediates, which disproportionate to 1Me/Et and hydrazido FeII[N-N(SiMe3)2] species (3Me/Et); the latter act as resting states on the catalytic cycle. Subsequent 2e- reduction of 3Me/Et leads to N-N scission and formation of [N(SiMe3)2]- and putative anionic Fe imido products. These mechanistic results are supported by both experiment and DFT calculations.
- Piascik, Adam D.,Li, Ruohao,Wilkinson, Harry J.,Green, Jennifer C.,Ashley, Andrew E.
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- Triphos-Fe dinitrogen and dinitrogen-hydride complexes: Relevance to catalytic N2 reduction
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The two electron reduction of iron complexes [(PRP2Cy)Fe(Cl)2] (R = Ph or tBu) 2a-b afforded complexes [(PRP2Cy)Fe(N2)2] 4a-b. Protonation of 4a at the metal center and subsequent reduction to Fe(i)-H species lead to complex [(PPhP2Cy)Fe(N2)(H)2] 6avia a spontaneous disproportionation reaction. Complex 4a behaves as one of the most efficient monometallic Fe-catalysts reported to date for N2-to-N(SiMe3)3 functionalization under atmospheric pressure.
- Cavaillé, Anthony,Joyeux, Benjamin,Saffon-Merceron, Nathalie,Nebra, Noel,Fustier-Boutignon, Marie,Mézailles, Nicolas
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- Cobalt-catalyzed transformation of molecular dinitrogen into silylamine under ambient reaction conditions
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The first successful example of cobalt-catalyzed reduction of N2 with Me3SiCl and Na as a reductant, under ambient reaction conditions, gives N(SiMe3)3, which can be readily converted into NH3. In this reaction system, 2,2′-bipyridine (bpy) is found to work as an effective additive to improve substantially the catalytic activity. Co-N2 complexes bearing three Me3Si groups as ancillary ligands are considered to work as key reactive species based on DFT calculations. The DFT results also allow the proposal of a detailed reaction pathway for the transformation of N2 into N(SiMe3)3.
- Imayoshi, Ryuji,Tanaka, Hiromasa,Matsuo, Yuki,Yuki, Masahiro,Nakajima, Kazunari,Yoshizawa, Kazunari,Nishibayashi, Yoshiaki
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- Coupling dinitrogen and hydrocarbons through aryl migration
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The activation of abundant molecules such as hydrocarbons and atmospheric nitrogen (N2) remains a challenge because these molecules are often inert. The formation of carbon–nitrogen bonds from N2 typically has required reactive organic precursors that are incompatible with the?reducing conditions that promote N2 reactivity1,?which has prevented catalysis. Here we report a diketiminate-supported iron system that sequentially activates benzene and N2 to form aniline derivatives. The key to this coupling reaction is the partial silylation of a reduced iron–dinitrogen complex, followed by migration?of a benzene-derived aryl group to the nitrogen. Further reduction releases N2-derived aniline, and the resulting iron species can re-enter the cyclic pathway. Specifically, we show that?an easily prepared diketiminate iron bromide complex2 mediates the one-pot conversion of several petroleum-derived arenes into the corresponding silylated aniline derivatives, by using a mixture of sodium powder, crown ether, trimethylsilyl bromide?and N2 as the nitrogen source. Numerous compounds along the cyclic pathway are isolated and crystallographically characterized, and their reactivity supports?a mechanism for sequential?hydrocarbon activation and N2 functionalization. This strategy couples?nitrogen atoms from N2 with abundant hydrocarbons, and maps a route towards future catalytic systems.
- McWilliams, Sean F.,Broere, Dani?l L. J.,Halliday, Connor J. V.,Bhutto, Samuel M.,Mercado, Brandon Q.,Holland, Patrick L.
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- Catalytic dinitrogen reduction at the molybdenum center promoted by a bulky tetradentate phosphine ligand
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Stoichiometric reduction of N2 at a Mo center stabilized by a bulky tetradentate phosphine ligand (PP3Cy) allowed isolation of Mo-imidoamine and Mo-imido complexes. Both complexes as well as the MoII precursor are equally suitable catalysts for the synthesis of NTMS3 (TMS= trimethylsilyl) from N2, TMSCl, and electron sources. Mechanistic studies prove the involvement of a TMS radical at least in one of the catalytic steps.
- Liao, Qian,Saffon-Merceron, Nathalie,Mzailles, Nicolas
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- Synthesis of a T-Shaped Cobalt(I) Complex and Its Dinitrogen Adduct
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The coordination chemistry of the new NNP pincer ligand framework (QuiNacNacP) is explored with cobalt. Upon treatment of the cobalt(II) complex Co[QuiNacNacP]Cl with KC8, the formation of cobalt(I) dinitrogen complex Co[QuiNacNacP]N2 was observed. Co[QuiNacNacP]N2 crystallizes as a square planar (S = 0) complex with an essentially unactivated N2 ligand. In solution, the dinitrogen complex is in equilibrium with the paramagnetic T-shaped complex Co[QuiNacNacP] (S = 1). The ability of Co[QuiNacNacP]Cl to act as a catalyst precursor in the reductive silylation of dinitrogen was also briefly explored. Reaction of ≈ 1000 equivalents KC8 with ≈ 1500 equivalents Me3SiCl (relative to Co[QuiNacNacP]Cl) under 1 atm of N2 furnished roughly 40 equivalents of N(SiMe3)3.
- Sanz, Corey A.,Stein, Carolin A. M.,Fryzuk, Michael D.
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- An arene-tethered silylene ligand enabling reversible dinitrogen binding to iron and catalytic silylation
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An arene-tethered silylene ligand, L (L = PhC(tBuN)2SiCH2C(tBu)NAr, Ar = 2,6-iPr2C6H3), allowed the synthesis of three-coordinate Fe(ii) silylamido and piano-stool Fe(
- Bai, Yunping,Zhang, Jianying,Cui, Chunming
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- Latent Nucleophilic Carbenes
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Using DFT and ab initio calculations, we demonstrate that noncyclic formamidines can undergo thermal rearrangement into their isomeric aminocarbenes under rather mild conditions. We synthesized the silylformamidine, for which the lowest activation energy in this process was predicted. Experimental studies proved it to serve as a very reactive nucleophilic carbene. The reactions with acetylenes, benzenes, and trifluoromethane proceeded via insertion into sp, sp2, and spCH bonds. The carbene also reacted with the functional groups, such as CHO, COR, and CN at double or triple bonds, displaying high mobility of the trimethylsilyl group. The obtained silylformamidine can be considered as a latent nucleophilic carbene. It can be prepared in bulk quantities, stored, and used when the need arises. Calculation results predict similar behavior for some other silylated formamidines and related compounds.
- Hurieva, Anastasiya,Koidan, Georgyi,Kostyuk, Aleksandr,Kyrylchuk, Andrii A.,Marchenko, Anatoliy,Rozhenko, Alexander B.,Rusanov, Eduard B.,Shvydenko, Kostiantyn
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- Ketone Enolization with Sodium Hexamethyldisilazide: Solvent- And Substrate-Dependent E- Z Selectivity and Affiliated Mechanisms
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Ketone enolization by sodium hexamethyldisilazide (NaHMDS) shows a marked solvent and substrate dependence. Enolization of 2-methyl-3-pentanone reveals E-Z selectivities in Et3N/toluene (20:1), methyl-t-butyl ether (MTBE, 10:1), N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDTA)/toluene (8:1), TMEDA/toluene (4:1), diglyme (1:1), DME (1:22), and tetrahydrofuran (THF) (1:90). Control experiments show slow or nonexistent stereochemical equilibration in all solvents except THF. Enolate trapping with Me3SiCl/Et3N requires warming to -40 °C whereas Me3SiOTf reacts within seconds. In situ enolate trapping at -78 °C using preformed NaHMDS/Me3SiCl mixtures is effective in Et3N/toluene yet fails in THF by forming (Me3Si)3N. Rate studies show enolization via mono- and disolvated dimers in Et3N/toluene, disolvated dimers in TMEDA, trisolvated monomers in THF/toluene, and free ions with PMDTA. Density functional theory computations explore the selectivities via the E- and Z-based transition structures. Failures of theory-experiment correlations of ionic fragments were considerable even when isodesmic comparisons could have canceled electron correlation errors. Swapping 2-methyl-3-pentanone with a close isostere, 2-methylcyclohexanone, causes a fundamental change in the mechanism to a trisolvated-monomer-based enolization in THF.
- Collum, David B.,Woltornist, Ryan A.
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p. 17452 - 17464
(2021/11/04)
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- Ammonia Formation Catalyzed by a Dinitrogen-Bridged Dirhenium Complex Bearing PNP-Pincer Ligands under Mild Reaction Conditions**
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A series of rhenium complexes bearing a pyridine-based PNP-type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen-bridged dirhenium complex bearing the PNP-type pincer ligands catalytically converts dinitrogen into ammonia during the reaction with KC8 as a reductant and [HPCy3]BArF4 (Cy=cyclohexyl, ArF=3,5-(CF3)2C6H3) as a proton source at ?78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium-dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC8 as a reductant and Me3SiCl as a silylating reagent under ambient reaction conditions to afford 11.7 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions using rhenium-dinitrogen complexes as catalysts.
- Egi, Akihito,Kuriyama, Shogo,Meng, Fanqiang,Nishibayashi, Yoshiaki,Tanaka, Hiromasa,Yoshizawa, Kazunari
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supporting information
p. 13906 - 13912
(2021/05/13)
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- Cluster Supported by Redox-Active o-Phenylenediamide Ligands and Its Application toward Dinitrogen Reduction
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As prevalent cofactors in living organisms, iron-sulfur clusters participate in not only the electron-transfer processes but also the biosynthesis of other cofactors. Many synthetic iron-sulfur clusters have been used in model studies, aiming to mimic their biological functions and to gain mechanistic insight into the related biological systems. The smallest [2Fe-2S] clusters are typically used for one-electron processes because of their limited capacity. Our group is interested in functionalizing small iron-sulfur clusters with redox-active ligands to enhance their electron storage capacity, because such functionalized clusters can potentially mediate multielectron chemical transformations. Herein we report the synthesis, structural characterization, and catalytic activity of a diferric [2Fe-2S] cluster functionalized with two o-phenylenediamide ligands. The electrochemical and chemical reductions of such a cluster revealed rich redox chemistry. The functionalized diferric cluster can store up to four electrons reversibly, where the first two reduction events are ligand-based and the remainder metal-based. The diferric [2Fe-2S] cluster displays catalytic activity toward silylation of dinitrogen, affording up to 88 equiv of the amine product per iron center.
- Liang, Qiuming,Demuth, Joshua C.,Radovi?, Aleksa,Wolford, Nikki J.,Neidig, Michael L.,Song, Datong
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supporting information
p. 13811 - 13820
(2021/06/27)
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- The Effect of Substituents on the Formation of Silyl [PSiP] Pincer Cobalt(I) Complexes and Catalytic Application in Both Nitrogen Silylation and Alkene Hydrosilylation
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Four different [PSiP]-pincer ligands L1-L4 ((2-Ph2PC6H4)2SiHR (R = H (L1) and Ph (L2)) and (2-iPr2PC6H4)2SiHR′ (R′ = Ph (L3) and H (L4)) were used to investigate the effect of substituents at P and/or Si atom of the [PSiP] pincer ligands on the formation of silyl cobalt(I) complexes by the reactions with CoMe(PMe3)4 via Si-H cleavage. Two penta-coordinated silyl cobalt(I) complexes, (2-Ph2PC6H4)2HSiCo(PMe3)2 (1) and (2-Ph2PC6H4)2PhSiCo(PMe3)2 (2), were obtained from the reactions of L1 and L2 with CoMe(PMe3)4, respectively. Under similar reaction conditions, a tetra-coordinated cobalt(I) complex (2-iPr2PC6H4)2PhSiCo(PMe3) (3) was isolated from the interaction of L3 with CoMe(PMe3)4. It was found that, only in the case of ligand L4, silyl dinitrogen cobalt(I) complex 4, [(2-iPr2PC6H4)2HSiCo(N2)(PMe3)], was formed. Our results indicate that the increasing of electron cloud density at the Co center is beneficial for the formation of a dinitrogen cobalt complex because the large electron density at Co center leads to the enhancement of the ?-backbonding from cobalt to the coordinated N2. It was found that silyl dinitrogen cobalt(I) complex 4 is an effective catalyst for catalytic transformation of dinitrogen into silylamine. Among these four silyl cobalt(I) complexes, complex 1 is the best catalyst for hydrosilylation of alkenes with excellent regioselectivity. For aromatic alkenes, catalyst 1 provided Markovnikov products, while for aliphatic alkenes, anti-Markovnikov products could be obtained. Both catalytic reaction mechanisms were proposed and discussed. The molecular structures of complexes 1-4 were confirmed by single-crystal X-ray diffraction.
- Dong, Yanhong,Zhang, Peng,Fan, Qingqing,Du, Xinyu,Xie, Shangqing,Sun, Hongjian,Li, Xiaoyan,Fuhr, Olaf,Fenske, Dieter
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p. 16489 - 16499
(2020/11/13)
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- An isolable iron(ii) bis(supersilyl) complex as an effective catalyst for reduction reactions
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An isolable 14-electron iron bis(supersilyl) complex, Fe[Si(SiMe3)3]2(THF)2, was successfully synthesized from the reaction of FeBr2 with K[Si(SiMe3)3] and its structure was unambiguously determined by single-crystal X-ray diffraction analysis. The complex is coordinatively unsaturated and exhibits high catalytic activity toward the hydrosilylation of carbonyl compounds and the reductive silylation of dinitrogen.
- Arata, Shogo,Sunada, Yusuke
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supporting information
p. 2891 - 2895
(2019/03/06)
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- Catalytic reduction of dinitrogen to tris(trimethylsilyl)amine using rhodium complexes with a pyrrole-based PNP-type pincer ligand
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Rhodium complexes bearing an anionic pyrrole-based PNP-type pincer ligand are synthesised and found to work as effective catalysts for the transformation of molecular dinitrogen into tris(trimethylsilyl)amine under mild reaction conditions. This is the first successful example of rhodium-catalysed dinitrogen reduction under mild reaction conditions.
- Kawakami, Ryosuke,Kuriyama, Shogo,Tanaka, Hiromasa,Arashiba, Kazuya,Konomi, Asuka,Nakajima, Kazunari,Yoshizawa, Kazunari,Nishibayashi, Yoshiaki
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supporting information
p. 14886 - 14889
(2019/12/24)
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- Bis(dinitrogen)cobalt(-1) Complexes with NHC Ligation: Synthesis, Characterization, and Their Dinitrogen Functionalization Reactions Affording Side-on Bound Diazene Complexes
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Late-transition-metal-based catalysts are widely used in N2 fixation reactions, but the reactivity of late-transition-metal N2 complexes, besides iron N2 complexes, has remained poorly understood as their N2 complexes were thought to be labile and hard to functionalize. By employing a monodentate N-heterocyclic carbene (NHC), 1,3-dicyclohexylimidazol-2-ylidene (ICy) as ligand, the cobalt(0)- and cobalt(-1)-N2 complexes, [(ICy)3Co(N2)] (1) and [(ICy)2Co(N2)2M]n (M = K, 2a; Rb, 2b; Cs, 2c), respectively, were synthesized from the stepwise reduction of (ICy)3CoCl by the corresponding alkaline metals under a N2 atmosphere. Complexes 2a-c in their solid states adopt polymeric structures. The N-N distances (1.145(6)-1.162(5) ?) and small N-N infrared stretchings (ca. 1800 and 1900 cm-1) suggest the strong N2 activation of the end-on N2 ligands in 2a-c. One electron oxidation of 1 by [Cp2Fe][BF4] gave the cobalt(I) complex devoid of N2 ligand [(ICy)3Co][BF4] (3). The bis(dinitrogen)cobalt(-1) complexes 2a-c undergo protonation reaction with triflic acid to give N2H4 in 24-30% yields (relative to cobalt). Complexes 2a-c could also react with silyl halides to afford diazene complexes [(ICy)2Co(η2-R3SiNNSiR3)] (R = Me, 6a; Et, 6b) that are the first diazene complexes of late transition metals prepared from N2 functionalization. Characterization data, in combination with calculation results, suggest the electronic structures of the diazene complexes as low-spin cobalt(II) complexes containing dianionic ligand [η2-R3SiNNSiR3]2-. Complexes 1, 2a-c, 6a, 6b, and (ICy)2CoCl2 proved to be effective catalysts for the reductive silylation of N2 to afford N(SiMe3)3. These NHC-cobalt catalysts display comparable turnover numbers (ca. 120) that exceed the reported 3d metal catalysts. The fine performance of the NHC-cobalt complexes in the stoichiometric and catalytic N2-functionalization reactions points out the utility of low-valent low-coordinate group 9 metal species for N2 fixation.
- Gao, Yafei,Li, Guangyu,Deng, Liang
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p. 2239 - 2250
(2018/02/19)
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- Catalytic Silylation of N2 and Synthesis of NH3 and N2H4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P4 Macrocycle
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We report the first discrete molecular Cr-based catalysts for the reduction of N2. This study is focused on the reactivity of the Cr-N2 complex, trans-[Cr(N2)2(PPh4NBn4)] (P4Cr(N2)2), bearing a 16-membered tetraphosphine macrocycle. The architecture of the [16]-PPh4NBn4 ligand is critical to preserve the structural integrity of the catalyst. P4Cr(N2)2 was found to mediate the reduction of N2 at room temperature and 1 atm pressure by three complementary reaction pathways: (1) Cr-catalyzed reduction of N2 to N(SiMe3)3 by Na and Me3SiCl, affording up to 34 equiv N(SiMe3)3; (2) stoichiometric reduction of N2 by protons and electrons (for example, the reaction of cobaltocene and collidinium triflate at room temperature afforded 1.9 equiv of NH3, or at -78 °C afforded a mixture of NH3 and N2H4); and (3) the first example of NH3 formation from the reaction of a terminally bound N2 ligand with a traditional H atom source, TEMPOH (2,2,6,6-tetramethylpiperidine-1-ol). We found that trans-[Cr(15N2)2(PPh4NBn4)] reacts with excess TEMPOH to afford 1.4 equiv of 15NH3. Isotopic labeling studies using TEMPOD afforded ND3 as the product of N2 reduction, confirming that the H atoms are provided by TEMPOH.
- Kendall, Alexander J.,Johnson, Samantha I.,Bullock, R. Morris,Mock, Michael T.
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supporting information
p. 2528 - 2536
(2018/02/28)
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- Efficient catalytic conversion of dinitrogen to N(SiMe3)3 Using a homogeneous mononuclear cobalt complex
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Incorporation of the tridentate phosphine-enamidoiminophosphorane onto cobalt(II) produces tetrahedral Co(NpNPiPr)Cl, 1, which upon reduction under dinitrogen generates the T-shaped, paramagnetic Co(I) complex Co(NpNPiPr), 2. This paramagnetic T-shaped derivative is in equilibrium with the paramagnetic dinitrogen derivative Co(NpNPiPr)(N2), 3, which can be detected by IR and low-temperature UV-vis spectroscopy. Both 1 and 2 act as homogeneous catalysts for the conversion of molecular nitrogen into tris(trimethylsilyl)amine (N(SiMe3)3) (～200 equiv, quantified as NH4Cl after hydrolysis) in the presence of excess KC8 and Me3SiCl at low temperatures.
- Suzuki, Tatsuya,Fujimoto, Keisuke,Takemoto, Yoshiyuki,Wasada-Tsutsui, Yuko,Ozawa, Tomohiro,Inomata, Tomohiko,Fryzuk, Michael D.,Masuda, Hideki
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p. 3011 - 3015
(2018/04/14)
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- Catalytic N2 Reduction to Silylamines and Thermodynamics of N2 Binding at Square Planar Fe
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The geometric constraints imposed by a tetradentate P4N2 ligand play an essential role in stabilizing square planar Fe complexes with changes in metal oxidation state. The square pyramidal Fe0(N2)(P4N2) complex catalyzes the conversion of N2 to N(SiR3)3 (R = Me, Et) at room temperature, representing the highest turnover number of any Fe-based N2 silylation catalyst to date (up to 65 equiv N(SiMe3)3 per Fe center). Elevated N2 pressures (>1 atm) have a dramatic effect on catalysis, increasing N2 solubility and the thermodynamic N2 binding affinity at Fe0(N2)(P4N2). A combination of high-pressure electrochemistry and variable-temperature UV-vis spectroscopy were used to obtain thermodynamic measurements of N2 binding. In addition, X-ray crystallography, 57Fe M?ssbauer spectroscopy, and EPR spectroscopy were used to fully characterize these new compounds. Analysis of Fe0, FeI, and FeII complexes reveals that the free energy of N2 binding across three oxidation states spans more than 37 kcal mol-1.
- Prokopchuk, Demyan E.,Wiedner, Eric S.,Walter, Eric D.,Popescu, Codrina V.,Piro, Nicholas A.,Kassel, W. Scott,Bullock, R. Morris,Mock, Michael T.
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p. 9291 - 9301
(2017/07/22)
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- Azaferrocene-Based PNP-Type Pincer Ligand: Synthesis of Molybdenum, Chromium, and Iron Complexes and Reactivity toward Nitrogen Fixation
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A series of azaferrocene-based PNP-type pincer ligands were designed and prepared as new PNP-type pincer ligands. Some transition-metal complexes, including molybdenum, chromium, and iron complexes, bearing these azaferrocene-based PNP-type pincer ligands were also prepared and characterized by X-ray analysis. The stoichiometric and catalytic reactivities of molybdenum–dinitrogen complexes toward nitrogen fixation were investigated in detail.
- Kuriyama, Shogo,Arashiba, Kazuya,Nakajima, Kazunari,Tanaka, Hiromasa,Yoshizawa, Kazunari,Nishibayashi, Yoshiaki
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supporting information
p. 4856 - 4861
(2016/10/31)
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- A method of manufacturing a silylamine and ammonia
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PROBLEM TO BE SOLVED: To provide a novel method for producing a silylamine, which uses a catalyst comprising an iron complex containing no molybdenum.SOLUTION: There is provided the method for producing a silylamine, which includes forming a silylamine represented by formula N(SiRRR)(In the formula, R, R, and Rare each independently selected from the group consisting of hydrogen and a C- Clinear, branched, or cyclic hydrocarbon group) by reacting a nitrogen gas with a silyl halide represented by formula SiRRRX (In the formula, R, R, and Rare each independently selected from the group consisting of a hydrogen atom and a C- Clinear, branched, or cyclic hydrocarbon group, and X is a halogen atom) in the presence of a catalyst which comprises an iron complex containing iron but not containing molybdenum, and a reducing agent.
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Paragraph 0040
(2017/06/08)
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- Catalytic Silylation of Dinitrogen with a Dicobalt Complex
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A dicobalt complex catalyzes N2 silylation with Me3SiCl and KC8 under 1 atm N2 at ambient temperature. Tris(trimethylsilyl)amine is formed with an initial turnover rate of 1 N(TMS)3/min, ultimately reaching a turnover number of ～200. The dicobalt species features a metal-metal interaction, which we postulate is important to its function. Although N2 functionalization occurs at a single cobalt site, the second cobalt center modifies the electronics at the active site. Density functional calculations reveal that the Co-Co interaction evolves during the catalytic cycle: weakening upon N2 binding, breaking with silylation of the metal-bound N2 and reforming with expulsion of [N2(SiMe3)3]-.
- Siedschlag, Randall B.,Bernales, Varinia,Vogiatzis, Konstantinos D.,Planas, Nora,Clouston, Laura J.,Bill, Eckhard,Gagliardi, Laura,Lu, Connie C.
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supporting information
p. 4638 - 4641
(2015/04/27)
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- Synthesis of the first persilylated ammonium ion, [(Me3Si) 3NSi(H)Me2]+, by silylium-catalyzed methyl/hydrogen exchange reactions
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This work describes the unexpected synthesis and characterization of the first persilylated ammonium ion, [(Me3Si)3NSi(H)Me 2]+, in the reaction of (Me3Si)3N with [Me3Si-H-SiMe3][B(C6F5) 4]. NMR and Raman studies revealed a transition-metal-free silylium ion catalyzed substituent redistribution process when [Me3Si-H- SiMe3]+ was used as the silylating reagent. These observations were affirmed in the reaction with [Et3Si-H-SiEt 3][B(C6F5)4]. A Lewis acid catalyzed scrambling process always occurs if an excess of silanes is present in the formation of silylium cations while employing the standard Bartlett-Schneider- Condon type reaction. Additionally, the thermodynamics of this process was accessed by DFT computations at the pbe1pbe/aug-cc-pVDZ level, indicating alkyl substituent exchange equilibria at the silane and preference of the formation of [(Me3Si)3NSi(H)Me2]+ over [(Me 3Si)4N]+.
- Labbow, Rene,Reiss, Fabian,Schulz, Axel,Villinger, Alexander
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supporting information
p. 3223 - 3226
(2014/08/05)
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- Preparation, characterization, and reactivity of dinitrogen molybdenum complexes with bis(diphenylphosphino)amine derivative ligands that form a unique 4-membered P-N-P chelate ring
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Five dinitrogen-molybdenum complexes bearing bis(diphenylphosphino)amine derivative ligands (LR) that form a unique 4-membered P-N-P chelate ring, trans-[Mo(N2)2(LR)2] (2 R: R = Ph, Xy, p-MeOPh, 3,5-iPr2Ph, iPr), were prepared for the purpose of binding a dinitrogen molecule. The corresponding two dichloride-molybdenum complexes, trans-[MoCl2(LR) 2] (1R: R = Ph, Xy), were also prepared as comparisons. FT-IR spectra of 2R were measured and compared the ν(Ni? - N) values. Moreover, X-ray crystal structure determination of 1R (R = Ph, Xy) and 2R (R = Xy, 3,5-iPr2Ph) is performed. These experimental results indicated that the coordinated dinitrogen molecule gets easily influenced by the N-substitutent of diphosphinoamine ligand. In addition, to investigate the effect of the properties of the diphosphinoamine ligand for the dinitrogen molybdenum complexes, we performed DFT calculations that focused on the difference of N-substituent, the dihedral angle between P-N-P plane and N-substituent aryl group, and the P-N-P bite angle. This calculation revealed that the competition between the back-donation from metal to dinitrogen and that from metal to ligand was affected by P-N-P bite angle and the dihedral angle of N-substituent of ligand. In order to examine the reactivity with respect to conversion of dinitrogen to ammonia, protonation and trimethylsilylation reactions of the coordinated dinitrogens were carried out for 2R.
- Ogawa, Takahiko,Kajita, Yuji,Wasada-Tsutsui, Yuko,Wasada, Hiroaki,Masuda, Hideki
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p. 182 - 195
(2013/02/23)
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- Molybdenum-catalyzed transformation of molecular dinitrogen into silylamine: Experimental and DFT study on the remarkable role of ferrocenyldiphosphine ligands
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A molybdenum-dinitrogen complex bearing two ancillary ferrocenyldiphosphine ligands, trans-[Mo(N2)2(depf)2] (depf = 1,1′-bis(diethylphosphino)ferrocene), catalyzes the conversion of molecular dinitrogen (N2) into silylamine (N(SiMe3) 3), which can be readily converted into NH3 by acid treatment. The conversion has been achieved in the presence of Me 3SiCl and Na at room temperature with a turnover number (TON) of 226 for the N(SiMe3)3 generation for 200 h. This TON is significantly improved relative to those ever reported by Hidai's group for mononuclear molybdenum complexes having monophosphine coligands [J. Am. Chem. Soc.1989, 111, 1939]. Density functional theory (DFT) calculations have been performed to figure out the mechanism of the catalytic N2 conversion. On the basis of some pieces of experimental information, SiMe3 radical is assumed to serve as an active species in the catalytic cycle. Calculated results also support that SiMe3 radical is capable of working as an active species. The formation of five-coordinate intermediates, in which one of the N2 ligands or one of the Mo-P bonds is dissociated, is essential in an early stage of the N2 conversion. The SiMe 3 addition to a "hydrazido(2-)" intermediate having the NN(SiMe3)2 group will give a "hydrazido(1-)" intermediate having the (Me3Si)NN(SiMe3)2 group rather than a pair of a nitrido (-N) intermediate and N(SiMe3) 3. The N(SiMe3)3 generation would not occur at the Mo center but proceed after the (Me3Si)NN(SiMe3) 2 group is released from the Mo center. The flexibility of the Mo-P bond between Mo and depf would play a vital role in the high catalysis of the Mo-Fe complex.
- Tanaka, Hiromasa,Sasada, Akira,Kouno, Tomohisa,Yuki, Masahiro,Miyake, Yoshihiro,Nakanishi, Haruyuki,Nishibayashi, Yoshiaki,Yoshizawa, Kazunari
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supporting information; experimental part
p. 3498 - 3506
(2011/05/04)
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- Reaction of nitrogen(I) oxide with nitrogen-fixing systems on the basis of lithium, chlorotrimethylsilane, and transition metal compounds
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Reaction of nitrogen(I) oxide with nitrogen-fixing systems Li/Me3SiCl/MCln (MCln = CrCl3, CoCl2, Cp2TiCl2, FeCl3, CuCl2) was studied. In these systems nitro
- Leont'ev,Mironov,Fomicheva,Proskurnina,Zefirov
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p. 905 - 906
(2007/10/03)
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- Reaction of Bis(trimethylsilyl) Sulfate with Hexamethyldisalazane, Acetamide, and Guanidine Hydrochloride
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Bis(trimethylsilyl) sulfate acts as a donor of trimethylsilyl group in the reaction with hexamethyldisilazane, which results in formation of tris(trimethylsilyl)amine. In the reaction with acetamide it acts as a donor of SO3. The latter inserts into the O-H bond of the imide form of acetamide; the final reaction products are acetonitrile and sulfuric acid. The reaction of bis(trimethylsilyl) sulfate with guanidine hydrochloride leads to trimethylchlorosilane and guanidine sulfate.
- Belousova,Vlasova,Voronkov
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p. 397 - 399
(2007/10/03)
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- Novel Syntheses of Bis(trialkylsilyl)amines by Reductive Trialkylsilylation of Azo Compounds
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Reduction of azo compounds with a system of a trialkylchlorosilane and lithium has been found to afford bis(trialkylsilyl)amines in the presence of a transition metal halide as a catalyst in THF.The reaction course was significantly modified by using t-butyldimethylchlorosilane as a trialkylchlorosilane.
- Kira, Mitsuo,Nagai, Satoshi,Nishimura, Mitsushi,Sakurai, Hideki
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p. 153 - 156
(2007/10/02)
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- New Selenium-Nitrogen Compounds tert-Butyl-seleninylamine, ButNSeO, and Di(tert-butyl)selenium Diimide, Se(NBut)2
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The first seleninylamine, tBuNSeO, was prepared from tert-butylamine, tBuNH2, and SeOCl2 (3:1).The selenium diimide Se(NBut)2 was isolated from the corresponding reaction of tBuNH2 and SeCl4 (6:1); it decomposes at ambient temperature to give cyclic Se3(NBut)2.The new compounds were characterized on the basis of their IR, 1H and 13C NMR and mass spectra. - Keywords: Selenium-Nitrogen Compounds, Selenium Diimides
- Herberhold, Max,Jellen, Wolfgang
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p. 144 - 148
(2007/10/02)
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- A Simple Synthesis pf Primary Amines via their N,N-Bis(trimethylsilyl) Derivatives
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Primary halogen compounds 1 or the corresponding tosylates react with sodium bis(trimethylsilyl)amide (2) in hexamethyldisilazane to form N,N-bis(trimethylsilyl)amines 3, which are converted into the amine hydrochlorides 5 by treatment with aqueous HCl.
- Bestmann, Hans Juergen,Woelfel, Gerhard
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p. 1250 - 1254
(2007/10/02)
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- Darstellung silylierter Lithium-tetrazenide
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Reactions of butyllithium with tris- or bis(trimethylsilyl)tetrazene, (Me3Si)3N4H or (Me3Si)2N4H2, lead to tetrazenides 1 - 3 which are sensitive in hydrolysis and thermolysis as well as against oxygen.Reactions (1) - (6) refer to their modes of thermolysis.
- Wiberg, Nils,Bayer, Heiner,Vasisht, Sham Kumar
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p. 2658 - 2660
(2007/10/02)
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