592-77-8Relevant articles and documents
Directing the Rate-Enhancement for Hydronium Ion Catalyzed Dehydration via Organization of Alkanols in Nanoscopic Confinements
Shetty, Manish,Wang, Huamin,Chen, Feng,Jaegers, Nicholas,Liu, Yue,Camaioni, Donald M.,Gutiérrez, Oliver Y.,Lercher, Johannes A.
supporting information, p. 2304 - 2311 (2020/12/01)
Alkanol dehydration rates catalyzed by hydronium ions are enhanced by the dimensions of steric confinements of zeolite pores as well as by intraporous intermolecular interactions with other alkanols. The higher rates with zeolite MFI having pores smaller than those of zeolite BEA for dehydration of secondary alkanols, 3-heptanol and 2-methyl-3-hexanol, is caused by the lower activation enthalpy in the tighter confinements of MFI that offsets a less positive activation entropy. The higher activity in BEA than in MFI for dehydration of a tertiary alkanol, 2-methyl-2-hexanol, is primarily attributed to the reduction of the activation enthalpy by stabilizing intraporous interactions of the Cβ-H transition state with surrounding alcohol molecules. Overall, we show that the positive impact of zeolite confinements results from the stabilization of transition state provided by the confinement and intermolecular interaction of alkanols with the transition state, which is impacted by both the size of confinements and the structure of alkanols in the E1 pathway of dehydration.
Olefin Dimerization and Isomerization Catalyzed by Pyridylidene Amide Palladium Complexes
Navarro, Miquel,Rosar, Vera,Montini, Tiziano,Milani, Barbara,Albrecht, Martin
, p. 3619 - 3630 (2018/10/05)
A series of cationic palladium complexes [Pd(N^N′)Me(NCMe)]+ was synthesized, comprising three different N^N′-bidentate coordinating pyridyl-pyridylidene amide (PYA) ligands with different electronic and structural properties depending on the PYA position (o-, m-, and p-PYA). Structural investigation in solution revealed cis/trans isomeric ratios that correlate with the donor properties of the PYA ligand, with the highest cis ratios for the complex having the most donating o-PYA ligand and lowest ratios for that with the weakest donor p-PYA system. The catalytic activity of the cationic complexes [Pd(N^N′)Me(NCMe)]+ in alkene insertion and dimerization showed a strong correlation with the ligand setting. While complexes bearing more electron donating m- and o-PYA ligands produced butenes within 60 and 30 min, respectively, the p-PYA complex was much slower and only reached 50% conversion of ethylene within 2 h. Likewise, insertion of methyl acrylate as a polar monomer was more efficient with stronger donor PYA units, reaching a 32% ratio of methyl acrylate vs ethylene insertion. Mechanistic investigations about the ethylene insertion allowed detection, for the first time, by NMR spectroscopy both cis- and trans-Pd-ethyl intermediates and, furthermore, revealed a trans to cis isomerization of the Pd-ethyl resting state as the rate-limiting step for inducing ethylene conversion. These PYA palladium complexes induce rapid double-bond isomerization of terminal to internal alkenes through a chain-walking process, which prevents both polymerization and also the conversion of higher olefins, leading selectively to ethylene dimerization.
Synthesis, structure and thermolysis of cis-dialkylplatinum(II) complexes - Experimental and theoretical perceptions
Venkatesh, Sadhana,Sravani, Chinduluri,Janardan, Sannapaneni,Suman, Pothini,Goud, E. Veerashekhara,Pavankumar,Leninkumar, Vardi,Bhat, Haamid R.,Sivaramakrishna, Akella,Vijayakrishna, Kari,Jha, Prakash C.,Smith, Gregory S.
, p. 72 - 81 (2016/07/06)
The formation of new C-C bonds by metal complexes always stimulates great interest because these fundamental reaction types possess numerous potential applications in organic synthesis. These reactions are well documented for a variety of transition metal complexes. Herein we report synthesis and characterization of a series of platinum-dialkyl complexes (1-10) of the type [Pt(L2)R2], (where L2 = dppp (1,3-bis(diphenylphosphino)propane or L = PPh3; R = n-butyl to n-nonyl) with a view to understand the organic product distribution patterns on thermolysis. The single crystal X-ray structures of the complexes [Pt(dppp){CH2(CH2)3CH3}2] (1) and [Pt(dppp){CH2(CH2)6CH3}2] (7) are reported. Thermal decomposition studies of these complexes show interesting behaviour; the longer chain dialkyls i.e. C7-C9 complexes undergo reductive elimination whereas the shorter chain dialkyl complexes and C3-C6 prefer only the β-hydride elimination reaction. Possible mechanistic aspects are discussed. Theoretical calculations reveal the strongest delocalizations in both complexes involve the interaction of Pt-C bond pair electron density with the trans positioned Pt-P antibonding orbital and vice-versa.
