Transition-Metal-Substituted Arsaalkenes. 7. Coupling of Transition Metal Carbynes with a Methylene Arsane Moiety:  Structure of Tp‘(CO)₂W⋮C−AsC(NMe₂)₂ [Tp‘ = HB(3,5-Me₂HC₃N₂)₃]

Condensation of Tp‘(CO)₂M⋮CCl [1a, M = Mo; 1b, W; Tp‘ = HB(3,5-Me₂HC₃N₂)₃] with the arsaalkene Me₃SiAsC(NMe₂)₂ afforded the novel arsaalkenyl carbyne complexes Tp‘(CO)₂M⋮C−AsC(NMe₂)₂ (2a) (M = Mo) and 2b (M = W). Methylation of 2a and 2b occurred at the arsenic atom to give the complexes [Tp‘(CO)₂M⋮CAs(Me)C(NMe₂)₂](SO₃CF₃) 3a (M = Mo) and 3b (M = W). Compounds 2a,b and 3a,b have been characterized by IR and ¹H and ¹³C NMR spectroscopy. In addition, the molecular structure of 2b has been determined by a single-crystal X-ray structural analysis.