Reaction of [Tp*(CO) 2 MtC-PdC(NMe 2 ) 2 ] [1a, M ) Mo; 1b, W; Tp* ) HB(3,5-Me 2 pz) 3 ] with 2 molar equiv of [Au(CO)Cl] afforded the trinuclear complexes [Tp*(CO) 2 MtC-P(AuCl) 2 C(NMe 2 ) 2 ] 2a (M ) Mo) and 2b (M ) W). In marked contrast to this the arsenic analogues [Tp*(CO) 2 MtC-AsdC(NMe 2 ) 2 ] (3a, M ) Mo; 3b, M ) W), when treated with the gold complex, give rise to AsdC cleavage with formation of the gold carbene complex [ClAuC-(NMe 2 ) 2 ] (5) and the functionalized cyclotriarsanes [{Tp*(CO) 2 MtC-As} 3 ] 4a (M ) Mo) and 4b (M ) W). Compounds 2a,b and 4a,b have been characterized by IR and 1 H and 13 C NMR spectroscopy. In addition, the molecular structures of 2a, 2b, and 5 have been determined by single-crystal X-ray structural analyses.