The Way into the Bridge:A New Bonding Mode of Tertiary Phosphanes,Arsanes,and Stibanes

摘要

Until recently,tertiary phosphanes,arsanes,and stibanes were considered to bind to transition-metal centers only in a terminal coordiantion model.Investigations on the reactivity of square-planar trans-[RhCl(=CRR')(L)_2] compounds revealed that compounds in which L=SbiPr_3 can be converted upon heating into dinculearcomplexes [Rh_2Cl_2(mu-CRR')_2(mu-SbiPr_3)]with the carbene and stibane ligands in bridging positions.Although attempts to replace the stibne in these complexes with a tertiary arsane or phosphane failed,substitution of the chloro ligands ofr acetylacetonates followed by bridge-ligand excahnge allowed the preapration of the chloro ligands for acetylacetonates follwed by bridge-ligand exchange allowed the preparation of the phosphane-and arsane-bridged compounds [Rh_2(acac)_2(mu-CRR')_2(mu-PR_3)]and [Rh_2(acac)_2(mu-CRR')_2(mu-AsMe_3)].The acac ligands can be replaced by anionic Lewis bases to give either monomeric [Rh_2X_2(mu-CRR')_2(mu-ER_3)] or dimeric chain-like [XRh(mu-CRR')_2(mu-ER_3)Rh(mu-X)_2Rh(mu-CRR')_2(mu-ER_3)RhX] molecules.