Poly(imidazolyliden-yl)borato Complexes of Tungsten: Mapping Steric vs. Electronic Features of Facially Coordinating Ligands.

A convenient synthesis of [HB(HImMe) 3 ](PF 6 ) 2 (ImMe = N -methylimidazolyl) is decribed. This salt serves in situ as a precursor to the tris(imidazolylidenyl)borate Li[HB(ImMe) 3 ] pro-ligand upon deprotonation with n BuLi. Reaction with [W(≡CC 6 H 4 Me-4)(CO) 2 (pic) 2 (Br)] (pic = 4-picoline) affords the carbyne complex [W(≡CC 6 H 4 Me-4)(CO) 2 {HB(ImMe) 3 }]. Interrogation of experimental and computational data for this compound allow a ranking of familiar tripodal and facially coordinating ligands according to steric (percentage buried volume) and electronic (ν CO ) properties. The reaction of [W(≡CC 6 H 4 Me-4)(CO) 2 {HB(ImMe) 3 }] with [AuCl(SMe 2 )] affords the heterobimetallic semi-bridging carbyne complex [WAu(μ-CC 6 H 4 Me-4)(CO) 2 (Cl){HB(ImMe) 3 }].