- Large effects of ion pairing and protonic-hydridic bonding on the stereochemistry and basicity of crown-, azacrown-, and cryptand-222-potassium salts of anionic tetrahydride complexes of iridium(III)
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The compounds [K(Q)][IrH4(PR3)2] (Q = 18-crown-6, R = Ph, iPr, Cy; Q = aza-18-crown-6, R = iPr; Q = 1,10-diaza-18-crown-6, R = Ph, iPr, Cy; Q = cryptand-222, R = iPr, Cy) were formed in the reactions of IrH5-(PR3)2 with KH and Q. In solution, the stereochemistry of the salts of [IrH4(PR3)2]- is surprisingly sensitive to the countercation: either trans as the potassium cryptand-222 salts (R = Cy, iPr) or exclusively cis (R = Cy, Ph) as the crown- and azacrown-potassium salts or a mixture of cis and trans (R = iPr). There is IR evidence for protonichydridic bonding between the NH of the aza salts and the iridium hydride in solution. In single crystals of [K(18-crown-6)][cis-IrH4(PR3)2] (R = Ph, iPr) and [K(aza-18-crown-6)][cis-IrH4(Pi Pr3)2], the potassium bonds to three hydrides on a face of the iridium octahedron according to X-ray diffraction studies. Significantly, [K(1,10-diaza-18-crown-6)][transIrH4(Pi Pr3)2] crystallizes in a chain structure held together by protonic-hydridic bonds. In [K(1,10-diaza-18-crown-6)][cis-IrH4(PPh3)2], the potassium bonds to two hydrides so that one NH can form an intra-ion-pair protonichydridic hydrogen bond while the other forms an inter-ion-pair NH···Hlr hydrogen bond to form chains through the lattice. Thus, there is a competition between the potassium and NH groups in forming bonds with the hydrides on iridium. The more basic PiP3 complex has the lower N-H stretch in the IR spectrum because of stronger N-H···HIr hydrogen bonding. The trans complexes have very low Ir-H wavenumbers (1670-1680) due to the trans hydride ligands. The [K(cryptand)]+ salt of [trans-IrH4(PiPr3)2]- reacts with WH6(PMe2Ph)3 (pKαTHF 42) to give an equilibrium (Keq = 1.6) with IrH5(PiPr3)2 and [WH5(PMe2Ph)3]- while the same reaction of WH6(PMe2Ph)3 with the [K(18-crown-6)]+ salt of [cis-IrH4(PiPr3)2]- has a much larger equilibrium constant (Keq = 150) to give IrH5(Pi-Pr3)2 and [WH5(PMe2Ph)3]-; therefore, the tetrahydride anion displays an unprecedented increase (about 100-fold) in basicity with a change from [K(crypt)]+ to [K(crown)]+ countercation and a change from trans to cis stereochemistry. The acidity of the pentahydrides decrease in THF as IrH5(PiPr3)2/[K(crypt)] [trans-IrH4(PiPr3)2] (pKαTHF = 42) > IrH5-(PCy3)2/[K(crypt)][trans- IrH4(PCy3)2] (pKαTHF = 43) > IrH5(PiPr3)2/[K(crown)] [cis-IrH4(PiPr3)2] (pKαTHF = 44) > IrH5-(PCy3)2/[K(crown)][cis H4(PCy3)2]. The loss of PCy3 from IrH5(PCy3)2 can result in mixed ligand complexes and H/D exchange with deuterated solvents. Reductive cleavage of P-Ph bonds is observed in some preparations of the PPh3 complexes.
- Landau, Shaun E.,Groh, Kai E.,Lough, Alan J.,Morris, Robert H.
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p. 2995 - 3007
(2008/10/08)
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- Synthesis and reactivity of alkoxy(η4-cycloocta-1,5-diene)iridium(I) and -rhodium(I) M(OR)(cod)(PCy3) Compounds. X-ray crystal structure of the alkynyl Ir(C≡CPh)(cod)(PCy3) complex
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The synthesis and reactivity of the alkoxy(η4-cycloocta-1,5-diene)iridium(I) Ir(OR)(cod)(PCy3) (R = Me, Et, or Ph; Cy = cyclohexyl; cod = cycloocta-1,5-diene) complexes are described. They are prepared by reaction of [Ir(μ-OR)(cod)]2 with PCy3. The synthesis of Rh(OPh)(cod)(PCy3) by reaction of [Rh(μ-OMe)(cod)]2 with PCy3 and PhOH is also reported. Treatment of [Ir(μ-OMe)(cod)]2 with PCy3 in methanol for 24 h gives a mixture of the hydrido IrH5(PCy3)2 and mer-IrH3(CO)(PCy3)2 complexes. Ir(OEt)(cod)(PCy3) reacts with HSiR3 (SiR3 = SiEt3 or SiMe2Ph) leading to the formation of IrH2(SiR3)(cod)(PCy3). Ir(OR)(COd)(PCy3) undergoes alkoxy exchange with phenol. Alkoxy exchange is also observed in the reaction of Ir(OEt)(COd)(PCy3) with phenylacetylene (HC≡CPh); the resulting Ir(C≡CPh)(cod)(PCy3) complex has been characterized by X-ray diffraction. Ir(C≡CPh)(cod)(PCy3): triclinic, space group P1, Z = 2, a = 12.3726 (6) A?, b = 11.1529 (4) A?, c = 12.4738 (5) A?, α = 105.307 (4)°, β = 101.845 (3)°, and γ = 107.607 (4)°. The structure was solved by Patterson and difference direct methods and refined to a conventional agreement factor of 0.034. The coordination around iridium is slightly distorted square planar, with a Ir-C(1) distance of 1.998 (6) A? and a C(1)-C(2) (C≡C) bond length and C(1)-C(2)-C(3) angle of 1.200 (10) A? and 176.5 (8)°, respectively.
- Fernández, María J.,Esteruelas, Miguel A.,Covarrubias, Macarena,Oro, Luis A.,Apreda, María-Carmen,Foces-Foces, Concepción,Cano, Felix H.
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p. 1158 - 1162
(2008/10/08)
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- Cationic molybdenum (IV)- and tungsten(IV)-iridium(III) complexes with hydride and η5:η1-cyclopentadienyl bridging ligands. Syntheses and X-ray crystal structure of [(η5-C5H5)M(μ-H) 2(μ-(η<
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Full title: Cationic molybdenum (IV)- and tungsten(IV)-iridium(III) complexes with hydride and η5:η1-cyclopentadienyl bridging ligands. Syntheses and X-ray crystal structure of [(η5-C5H5)M(μ-H) 2
- Albinati, Alberto,Togni, Antonio,Venanzi, Luigi M.
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p. 1785 - 1791
(2008/10/08)
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- (1+) : A Non-classical Polyhydride Complex
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(Cy = cyclohexyl) is shown by n.m.r. evidence, including T1 measurements, to undergo protonation to give the title complex, a bis(dihydrogen) dihydride, the first example of a non-classical polyhydride complex.
- Crabtree, Robert H.,Lavin, Maryellen
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p. 1661 - 1662
(2007/10/02)
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