Ligand Elaboration Mediated by a Cp*W(NO) Template: Stepwise Incorporation of Small Molecules into a Tungsten Vinyl Fragment

Abstract

Thermolysis of the alkyl vinyl complex Cp*W(NO)(CH2SiMe3)(CPhCH2) (1) in the presence of unsaturated, heteroatom-containing compounds such as esters and nitriles quantitatively affords metallacyclic products of reductive coupling. These are trapped as 18e complexes via either intramolecular rearrangement or intermolecular reaction with added trapping reagents. The nature of these metallacycles is consistent with the intermediacy of the acetylene complex Cp*W(NO)(η2-CPh⋮CH) (A) derived in situ from the reductive elimination of SiMe4 from 1. With esters ROAc (R = Me, Et), reductive coupling and C−O bond cleavage yields the alkoxide-containing oxametallacyclopentadiene complexes Cp*W(NO)(η2-OC(Me)CHCPh)(OR) (2, R = Me; 3, R = Et). Thermolysis of 1 in RCN (R = Me, Et, iPr) containing small excess amounts of R‘OH yields the respective hydroxide or alkoxide compounds Cp*W(NO)(η2-NHC(R)CHCPh)(OR‘) (4, R = Me, R‘ = H; 5, R = Et, R‘ = H; 6, R = iPr, R‘ = H; 7, R = Me, R‘ = C3H5). Utilization of cyclopentadiene (Cp...