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)CO
(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)}(CNBut)L](M = Pt or Pd, L = AsPh3 or PPh3). The single-crystal X-ray structure of [[graphic omitted]H(CO2Me)}(CNBut)(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)}(CNBut)(PPh3)] or 2 mole equivalents of CNBut with [[graphic omitted]H(CO2Me)}(PPh3)2] give the ring-expanded zwitterionic complex [[graphic omitted]NHBut}(CNBut)(PPh3)]. Similar complexes [[graphic omitted]
NHBut}(CNBut)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 CNBut. The structure of [[graphic omitted]
NHBut}(CNBut)2] was established by a single-crystal X-ray diffraction study.