Condensation of Tp'(CO)2M.tplbond.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.tplbond.C-As:C(NMe2)2 (2a, M = Mo) and (2b, M = W). Methylation of 2a and 2b occurred at the As atom to give [Tp'(CO)2M.tplbond.CAs(Me)C(NMe2)2](SO3CF3) (3a, M = Mo) and (3b, M = W). Compds. 2a,b and 3a,b were characterized by IR and 1H and 13C NMR spectroscopy. The mol. structure of 2b was detd. by a single-crystal x-ray structural anal.