18666-24-5Relevant articles and documents
Fe and Co Complexes of Rigidly Planar Phosphino-Quinoline-Pyridine Ligands for Catalytic Hydrosilylation and Dehydrogenative Silylation
Basu, Debashis,Gilbert-Wilson, Ryan,Gray, Danielle L.,Rauchfuss, Thomas B.,Dash, Aswini K.
, p. 2760 - 2768 (2018)
Co and Fe dihalide complexes of a new rigidly planar PNN ligand platform are prepared and examined as precatalysts for hydrosilylation of alkenes. Lithiation of Thummel's 8-bromo-2-(pyrid-2′-yl)quinoline followed by treatment with (i-Pr)2PCl and (C6F5)2PCl afforded the phosphine-quinoline-pyridine ligands, abbreviated RPQpy for R = i-Pr and C6F5, respectively. These ligands form 1:1 adducts with the dichlorides and dibromides of iron and cobalt. Crystallographic characterization of FeBr2(iPrPQpy), FeBr2(ArFPQpy), CoCl2(iPrPQpy), CoBr2(iPrPQpy), and CoCl2(ArFPQpy) confirmed that the M-P-C-C-N-C-C-N portion of these complexes is planar within 0.078 ? unlike previous generations of PNN complexes where deviations from planarity were ～0.35 ?. Bond distances as well as magnetism indicate that the Fe complexes are high spin and the cobalt complexes are high spin or participate in spin equilibria. Also investigated were the NNN analogues of the RPQpy ligands, wherein the phosphine group was replaced by the mesityl ketimine. The complexes FeBr2(MesNQpy) and CoCl2(MesNQpy) were characterized crystallographically. Reduction of MX2(RPQpy) complexes with NaBHEt3 generates catalysts active for anti-Markovnikov silylation of simple and complex 1-alkenes with a variety of hydrosilanes. Catalysts derived from MesNQpy exhibited low activity. Fe-RPQpy derived catalysts favor hydrosilylation, whereas Co-RPQpy based catalysts favor dehydrogenative silylation. Catalysts derived from CoX2(iPrPQpy) convert hydrosilanes and ethylene to vinylsilanes. Related experiments were conducted on propylene to give propenylsilanes.
Reaction of a zirconocene-ethylene complex with group 14 metal chlorides or alkoxides
Ura, Yasuyuki,Hara, Ryuichiro,Takahashi, Tamotsu
, p. 195 - 196 (1998)
A zirconocene-ethylene complex C p2Zr(CH2 = CH2)-(PMe3) reacted with R3EX (E= Si, Ge, Sn; R = Ph or Bu; X = Cl, OE1, or OER3) to give R3EEt in high yields after hydrol
Heterolysis of Dihydrogen by Nucleophilic Calcium Alkyls
Wilson, Andrew S. S.,Dinoi, Chiara,Hill, Michael S.,Mahon, Mary F.,Maron, Laurent
supporting information, p. 15500 - 15504 (2018/11/01)
β-Diketiminato (BDI) calcium alkyl derivatives undergo hydrogenolysis with H2 to regenerate [(BDI)CaH]2, allowing the catalytic hydrogenation of a wide range of 1-alkenes and norbornene under very mild conditions (2 bar H2, 298 K). The reactions are deduced to take place with the retention of the dimeric structures of the calcium hydrido-alkyl and alkyl intermediates via a well-defined sequence of Ca?H/C=C insertion and Ca?C hydrogenation events. This latter deduction is strongly supported by DFT calculations (B3PW91) performed on the 1-hexene/H2 system, which also indicates that the hydrogenation transition states display features which discriminate them from a classical σ-bond metathesis mechanism. In particular, NBO analysis identifies a strong second order interaction between the filled α-methylene sp3 orbital of the n-hexyl chain and the σ* orbital of the H2 molecule, signifying that the H?H bond is broken by what is effectively the nucleophilic displacement of hydride by the organic substituent.
Thermolysis reactions of cis-PtR(SiPh3)(PMe2Ph)2 in solution
Hasebe, Koh,Kamite, Jun,Mori, Takuya,Katayama, Hiroyuki,Ozawa, Fumiyuki
, p. 2022 - 2030 (2008/10/08)
A series of trans- and cis-PtR(SiPh3)(PMe2Ph)2 complexes have been prepared and their thermolysis reactions in solution examined. The trans isomers (R = Me, Et) are robust, and only the methyl complex affords MeSiPh3 as the reductive elimination product in 72-82% yields. In contrast, the cis isomers (R = Me, Et, Pr, Bu) form the corresponding alkylsilanes in almost quantitative yields (>97%). Despite the selective formation of the reductive elimination products, the cis-alkyl-silyl complexes bearing β-hydrogens undergo a rapid repetition of the β-hydrogen elimination and insertion processes, as confirmed by a deuterium-labeling experiment using cis-Pt(CH2CD3)(SiPh3)(PMe2Ph) 2. The alkylsilane formation from the cis isomers proceeds via two reaction paths. One is the direct C-Si reductive elimination. On the other path, the cis-PtR(SiPh3)(PMe2Ph)2 complexes are initially isomerized to the corresponding cis-PtPh(SiRPh2)(PMe2Ph)2 complexes by the exchange of the Pt-R group with the Si-Ph group, and the resulting phenyl-silyl complexes reductively eliminate alkylsilanes. The methyl-silyl complex decomposes exclusively by the former path, while the other alkyl-silyl complexes (R = Et, Pr, Bu) follow mainly the latter path. Preparation and thermolysis reaction of the related cis-PtEt(GePh3)(PMe2Ph)2 are also reported.
