title: Pt-Mo and Pt-W mixed-metal clusters with chelating or bridging diphosphine short-bite ligands (Ph2P)2NH and (Ph2P)2N(CH2)9CH3: a combined synthetic and theoretical study.
abstract: The reactivity of the complexes [PtCl(2){Ph(2)PN(R)PPh(2)-P,P}] (R = -H, 3; R = -(CH(2))(9)CH(3), 8) toward group 6 carbonylmetalates Na[MCp(CO)(3)] (M = W or Mo, Cp = cyclopentadienyl) was explored. When R = H, the triangular clusters [PtM(2)Cp(2)(CO)(5)(μ-dppa)] (M = W, 4; M = Mo, 5), in which the diphosphane ligand bridges a Pt-M bond, were obtained as the only products. When R = -(CH(2))(9)CH(3), isomeric mixtures of the triangular clusters [PtM(2)Cp(2)(CO)(5){Ph(2)PN(R)PPh(2)-P,P}], in which the diphosphane ligand chelates the Pt center (M = W, 11; M = Mo, 13) or bridges a Pt-M bond (M = W, 12; M = Mo, 14), were obtained. Irrespective of the M/Pt ratio used when R = -(CH(2))(9)CH(3), the reaction of [PtCl(2){Ph(2)PN(R)PPh(2)-P,P}] with Na[MCp(CO)(3)] in acetonitrile stopped at the monosubstitution stage with the formation of [PtCl{MCp(CO)(3)}{Ph(2)PN(R)PPh(2)-P,P}] (R = -(CH(2))(9)CH(3), M = W, 9; M = Mo, 10), which are the precursors to the trinuclear clusters formed in THF when excess carbonylmetalate was used. The dynamic behavior of the dppa derivatives 4 and 5 in solution as well as that of their carbonylation products 6 and 7, respectively, is discussed. Density functional calculations were performed to study the thermodynamics of formation of 4 and 5 and 11-14, to evaluate the relative stabilities of the chelated and bridged forms and to trace a possible pathway for the formation of the trinuclear clusters.
authors.affiliation: Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica, Politecnico di Bari, via Orabona 4, I-70125 Bari, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Todisco
authors.forename: Vito
authors.initials: V
authors.lastname: Gallo
authors.forename: Piero
authors.initials: P
authors.lastname: Mastrorilli
authors.forename: Mario
authors.initials: M
authors.lastname: Latronico
authors.forename: Nazzareno
authors.initials: N
authors.lastname: Re
authors.forename: Francesco
authors.initials: F
authors.lastname: Creati
authors.forename: Pierre
authors.initials: P
authors.lastname: Braunstein
mesh_terms: D002614:Chelating Agents / Q000138:chemical synthesis / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008982:Molybdenum / Q000737:chemistry*; D010720:Phosphines / Q000138:chemical synthesis / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D013816:Thermodynamics; D014414:Tungsten / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D056831:Coordination Complexes; D008024:Ligands; D010720:Phosphines; D010984:Platinum; D008982:Molybdenum; D014414:Tungsten