Synthesis and Reactions of Diphosphinidenecyclobutene Ruthenium Complexes Relevant to Catalytic Hydrosilylation of Terminal Alkynes

Abstract

The complex [RuCl(µ-Cl)(CO)(DPCB-OMe)] 2 (1a), bearing a low-coordinated phosphorus ligand (DPCB-OMe ) 1,2-bis(4-methoxyphenyl)-3,4-bis [(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene), is readily reduced to [RuH(µ-Cl)(CO)(DPCB-OMe)] 2 (2a) by the reaction with water and HSiMe 2 Ph. The reaction proceeds via a [RuCl 2 (CO)(H 2 O)(DPCB-OMe)] intermediate, which is characterized by X-ray diffraction analysis. Complexes 1a and 2a serve as highly efficient catalysts for Z-selective hydrosilylation of phenylacetylene. The reason for the high catalyst efficiency of DPCB-OMe complexes has been investigated by reaction and structure analysis of the presumed intermediate [Ru(CHdCHPh)Cl(CO)(DPCB-OMe)] (3a). It has been found that 3a has ample space to associate with hydrosilane and, therefore, readily undergoes metathesis between Ru-C and H-Si bonds. This structural feature in conjunction with the strong π-accepting ability of the DPCB-OMe ligand leads to highly efficient catalysis for Z-selective hydrosilylation of terminal alkynes.

A Bis(phosphaethenyl)pyridine Complex of Iridium(I): Synthesis and Catalytic Application to N-Alkylation of Amines with Alcohols

“…There has been considerable interest in the coordination chemistry of low-coordinate phosphorus compounds, owing to their unique ligand properties. , Phosphaalkenes having a PC bond are among the central subjects in such chemistry. , They possess an extremely low lying π* orbital around the phosphorus atom and thus exhibit a marked tendency to engage in effective π back-bonding with transition metals. We have demonstrated with bidentate diphosphinidenecyclobutene ligands (DPCB-Y) that this property is useful for catalysis, leading to highly efficient organic transformations in conjunction with group 8–10 metals. , Representative examples include hydroamination of 1,3-dienes (Pd), dehydrative allylation with allylic alcohols (Pd), and Z -selective hydrosilylation of alkynes (Ru) …”

Aqua and Diethyl Ether PNNP Complexes of Ruthenium(II): Structure and Solution Behavior

“…For example, hard co-ligands increase the affinity of ruthenium for oxygen donors, the most striking and elegant example being [Ru(OH 2 ) 6 ] 2+ . In combination with soft or borderline ligands, such as phosphines and chloro, the affinity of ruthenium(II) for oxygen donors is low, and only a few aqua complexes are known when P and Cl donors are simultaneously present in its coordination sphere …”

P,N-type phosphaalkene-based Ir(i) complexes: synthesis, coordination chemistry, and catalytic applications

“…3 This particular ligand property is useful, as it should in principle facilitate the reductive elimination step in a given catalytic cycle, leading to efficient systems for a wide range of catalytic organic transformations in conjunction with group 8–10 metals. 4–6 Representative examples, in which PA-containing metal complexes were utilised, include the hydroamination of 1,3-dienes (Pd), 7 the dehydrative allylation with allylic alcohols (Pd), 8,9 the Z -selective hydrosilylation of alkynes (Ru), 10,11 the hydroamidation of enones (Rh) 12 and the N -alkylation of amines with alcohols (Ir). 13 N -Alkylation of amines with alcohols is an environmentally benign process of preparing amines, which produces water as the sole byproduct.…”