Chemistry of metallacyclobutanones (η3-oxodimethylenemethane complexes). Part 5. Ligand substitution reactions of metallacyclobutan-3-ones of platinum(II) and palladium(II) with tertiary phosphines and t-butyl isocyanide; crystal structures of [Pt{CH(CO2Me)COCH(CO2Me)}(CNBut)(AsPh3)] and [Pt{CH(CO2Me)COC̄(CO2Me)C(NHBut)}(CNBut)2]

Abstract

The ligands L displace triphenylarsine from the complexes [[graphic omitted]H(CO₂Me)}(AsPh₃)₂] to give good yields of the complexes [[graphic omitted]H(CO₂Me)}L₂](M = Pt, L = PPh₃, PMePh₂, PMe₂Ph, L₂= Ph₂PCH₂CH₂PPh₂(dppe); M = Pd, L = PPh₃, L₂= 2,2′-bipyridine). Treatment of the complexes [[graphic omitted]H(CO₂Me)}L₂] with one mole equivalent of t-butyl isocyanide gives the monosubstituted complexes [[graphic omitted]H(CO₂Me)}(CNBu^t)L](M = Pt or Pd, L = AsPh₃ or PPh₃). The single-crystal X-ray structure of [[graphic omitted]H(CO₂Me)}(CNBu^t)(AsPh₃)] establishes the presence of a puckered platinacyclobutan-3-one ring [fold angle = 42(1)°] with the triphenylarsine ligand trans to the axial methoxycarbonyl group. The reactions of 1 mole equivalent of t-butyl isocyanide with [[graphic omitted]H(CO₂Me)}(CNBu^t)(PPh₃)] or 2 mole equivalents of CNBu^t with [[graphic omitted]H(CO₂Me)}(PPh₃)₂] give the ring-expanded zwitterionic complex [[graphic omitted]NHBu^t}(CNBu^t)(PPh₃)]. Similar complexes [[graphic omitted]NHBu^t}(CNBu^t)₂] are formed upon treatment of [[graphic omitted]H(COR)L₂](R = OMe, L = AsPh₃ or PPh₃; R = Me, L = PPh₃) with three mole equivalents of CNBu^t. The structure of [[graphic omitted]NHBu^t}(CNBu^t)₂] was established by a single-crystal X-ray diffraction study.