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Updated: Jul 12, 2025
Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
A [CoSiH2] Silylene Synthon Provides Modular Access to Homo- and Heterobimetallic [Co═Si═M] (M = Co, Fe) Silicide
Rex C Handford1, T Don Tilley1
1Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.
Abstract:
Base-stabilized [BP3](H)2CoSiH2(DMAP) (1, [BP3] = PhB(CH2PPr2)3-; DMAP = 4-dimethylaminopyridine) is a rare instance of a synthon for the simplest "parent" silylene complex (LM═SiH2). Complex 1 was accessed in high yields via double Si-H bond activation in SiH4 by [BP3]Co(DMAP), and in solution, it undergoes rapid exchange between bound and free DMAP by an associative mechanism (as determined by variable-temperature 1H NMR dynamic studies). The DMAP ligand of 1 is readily displaced by metal-based fragments that bind silicon and cleave the Si-H bonds of the SiH2 moiety to produce bimetallic [Co═Si═M] (M = Co, Fe) molecular silicides. Thus, treatment of 1 with 0.5 equiv of (LCoI)2(μ-N2) (L = a tripodal ligand) resulted in the spontaneous formation of [BP3](H)2Co═Si═Co(H)2L (L = [BP2Pz], PhB(CH2PBu2)2(pyrazolyl)- (3); Tp″, HB(3,5-diisopropylpyrazolyl)3- (4)) with the concomitant release of DMAP. The symmetrical silicide [BP3](H)2Co═Si═Co(H)2[BP3] (5) was prepared by treatment of a mixture of 1 and [BP3]Co(DMAP) with 2 equiv of Ph3B, which in this case is required to sequester DMAP as the elimination product Ph3B-DMAP. A heterobimetallic silicide, [BP3](H)2Co═Si═Fe(H)2[SiP3] (7; [SiP3] = PhSi(CH2PPr2)3), was obtained via in situ KC8 reduction of [SiP3]FeCl and subsequent addition of 1 and Ph3B. These transformations involving a metal-SiH2 derivative demonstrate a fundamentally new type of reactivity for silylene complexes and provide a unique synthetic method for construction of molecular silicide complexes.
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