The Interplay of Bis(tricarbido) and Dimetallaoctatetrayne Complexes of Platinum

Non-interconvertible platinum bis(tricarbidotungsten) and dimetallaoctatetrayne π-complexes arise from the reactions of bis(tricarbidotungsten)mercurials and aurates with complexes of platinum(0) and platinum(II). Thus [PtCl2(PPh3)2] with either [Hg{C3W(CO)2(Tp*)}2] or PPN[Au{C3W(CO)2(Tp*)}] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) affords both cis-[Pt{C3W(CO)2(Tp*)}2(PPh3)2] and [(Tp*)(CO)2WC6W(CO)2(Tp*)], while the latter with [Pt(C2H4)(PPh3)2] affords the π-complex [Pt{η2-(Tp*)(CO)2WC6W(CO)2(Tp*)}(PPh3)2], which does not convert to the bis(tricarbido) isomer. Although an intermediate bis(tricarbidotungsten) complex [Pt{C3W(CO)2(Tp*)}2(dppe)] (dppe = 1,2-bis(diphenylphosphine)ethane) may be spectroscopically observed to form in the related reaction employing [PtCl2(dppe)], this is unstable, ultimately and exclusively evolving to the free dimetallaoctatetrayne. The reaction of [Pt(C2H4)(PPh3)2] with [Hg{C3W(CO)2(Tp*)}2] provides a ca 3:2 mixture of cis-[Pt{C3W(CO)2(Tp*)}2(PPh3)2] and [Pt{η2-(Tp*)(CO)2WC6W(CO)2(Tp*)}(PPh3)2] in addition to traces of [(Tp*)(CO)2WC6W(CO)2(Tp*)]. Circumstantial evidence is presented to suggest that the mercuric chloride liberated in the transmetalation reaction plays a role in subsequent transformations.