Spectroscopic and solid state characterization of bimetallic terdentate [C,N,S] thiosemicarbazone Palladium(II) metallacycles with bridging and chelating [P,P] diphosphine ligands

Bimetallic cyclometallated palladium(II) complexes readily react with silver perchlorate and tertiary diphosphines to give dipalladium compounds with terdentate [C,N,S] thiosemicarbazones, and with bridging and chelating [P,P] ligands, of the type [Pd(Ph2PCH2PPh2-P,P){Pd[4-MeOC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHMe](Ph2PCH2PPh2)-P,S}] [ClO4]2, 1a. The crystal structures of complexes [PdCl2{Pd[2-MeOC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHMe](Ph2PC(CH2)2PPh2)-P,S}] and [Pd(Ph2PCH2PPh2-P,P){Pd[3-MeOC6H3C(Me)double bond; length as m-dashNNdouble bond; length as m-dashC(S)NHMe](Ph2PC(CH2)2P-Ph2)-P,S}]-[ClO4]2, 6 and 4a, respectively, are the first reported examples of palladacycles with the diphosphine Ph2PC(CH2)2PPh2, bis(diphenylphosphine)cyclopropane (dcpc), in the bridging mode. The short-bite diphosphines produce strained four-membered rings at the metal; the structures for 1a and 4a show the P–C–P carbon atom puckered away from the metal coordination plane.