Cobalt(II) and (I) Complexes of Diphosphine‐Ketone Ligands: Catalytic Activity in Hydrosilylation Reactions

Abstract

The hydrosilylation of unsaturated compounds homogeneously catalyzed by cobalt complexes has gained considerable attention in the last years, aiming at substituting precious metal‐based catalysts. In this study, the catalytic activity of well‐characterized CoII and CoI complexes of the pToldpbp ligand is demonstrated in the hydrosilylation of 1‐octene with phenylsilane. The CoI complex is the better precatalyst for the mentioned reaction under mild conditions, at 1 mol‐% catalyst, 1 h, room temperature, and without solvent, yielding 84 % of octylphenylsilane. Investigation of the substrate scope shows lower performance of the catalyst in styrene hydrosilylation, but excellent results with allylbenzene (84 %) and acetophenone (> 99 %). This catalytic study contributes to the field of cobalt‐catalyzed hydrosilylation reactions and shows the first example of catalysis employing the dpbp ligand in combination with a base metal.

Cobalt Complexes Supported by Phosphinoquinoline Ligands for the Catalyzed Hydrosilylation of Carbonyl Compounds

“…The experiments conducted are in favor of a classical mechanism involving a cobalt‐hydride as the active catalyst. In our case as for others [26c,27a,f,i,j] the hydrosilylation catalytic reaction works without any hydride additive, therefore the formation of the active Co−H species may result from σ‐bonds interchange at the metal center by the so‐called sigma‐bond metathesis [34] . Coordination of the ketone and its insertion into the Co−H bond leads to an alkoxo complex which upon reaction with the silane regenerates the active Co−H complex and releases the silyl ether (Scheme 5).…”

Mesoionic Carbene Cobalt Complexes as Multipurpose Catalyst Precursors for Hydrosilylation and Dihydropyrimidinone Synthesis

“…Reduction of carbonyl compounds by hydrosilylation is a fundamental process in organic chemistry, however, to date most reported catalysts are based on precious metal such as iridium, [45] ruthenium, [46] platinum, [47] or gold [48] . As an alternative, systems based on Earth‐abundant metals including Cu, [49] Ni, [50] and Fe [51] have recently been explored in carbonyl hydrosilylation and showed promising results. Remarkably, processes based on well‐defined cobalt systems for selective hydrosilylation remain quite scarce [52,53] …”

Cooperative Si–H Addition to Side-On Ni(0)-Imine Complexes Forms Reactive Hydrosilazane Complexes

“…In the frame of our studies of phosphine-tethered CO and CN π-ligands, − we recently reported the Ni(0) coordination of a series of ligands consisting of an imine functionality bridged by two o -phenylene linkers with phosphine substituents (PCNP) (Scheme ). The less bulky ligands afforded tetrahedral Ni(0) complexes Ni­(P Ph CNP Ph )­PPh 3 ( 2 ) and Ni­(P Ph CNP o Tol )­PPh 3 ( 3 ) with the PCNP ligand bound via both phosphine arms and an η 2 ( C , N )-coordination of the imine moiety.…”