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.

Sulfur-Assisted Phenyl Migration from Phosphorus to Platinum in PtW2 and PtMo2 Clusters Containing Thioether-Functionalized Short-Bite Ligands of the Bis(diphenylphosphanyl)amine-Type

“…2.1. Reactivity of the Platinum Complexes 1 and 2 with Na[M(CO) 3 1), were also obtained. These clusters are formula isomers; one phosphorus donor has migrated from Pt to Mo, while a CO ligand has moved from Mo to Pt.…”

“…9 The behavior of thioetherfunctionalized ligands (Ph 2 P) 2 N-R in which R = (CH 2 ) 2 S-(CH 2 ) 5 CH 3 , (CH 2 ) 2 SCH 2 Ph has been reported for platinum− cobalt clusters and parallels that observed with n-decyl-substituted dppa, in that both bridged and chelated isomeric PtCo 2 clusters are formed. 3 In the course of further studies on the reactivity of Pt(II) complexes of the type [PtCl 2 {(Ph 2 P) 2 N(CH 2 ) 2 SR-P,P}] (R = (CH 2 ) 5 CH 3 , CH 2 Ph), bearing a thioether-functionalized dppa chelate, with the Mo-and W-based metalates Na[M(CO) 3 Cp] (M = Mo or W throughout the paper), we unexpectedly isolated trinuclear complexes resulting from the activation of a P−phenyl bond and the migration of this phenyl ring to the platinum atom. Such dramatic molecular rearrangements are relevant to cooperativity effects in heterometallic-induced reactivity.…”

Transition Metal Chain Complexes Supported by Soft Donor Assembling Ligands

“…76 A similar behavior was observed with dppa as bridging ligand. 177 In the dppa-supported W−Pt−W chain complex 20 analogous to 18 and prepared similarly using dppa in place of dppm (Scheme 8), a dynamic process was observed by variabletemperature 31 P{ 1 H} NMR spectroscopy which was suggested to involve exchange between chelating and bridging bonding modes of the dppa ligand. The 31 P{ 1 H} NMR spectra revealed no exchange in the analogous Mo−Pt−Mo chain complex.…”

“…The 31 P{ 1 H} NMR spectra revealed no exchange in the analogous Mo−Pt−Mo chain complex. 177 During attempts to prepare the corresponding Mo−Pt−Mo and W−Pt−W chain complexes of type 20 with thioether Nfunctionalized dppa analogues by ring-opening of the chelating P,P ligand, as described with dppm (Scheme 7), an unprecedented reactivity was observed. An unusual intramolecular phenyl migration from phosphorus to platinum led to 21 and 22, which contain only one Mo−Pt (2.9174(5) Å) and W−Pt (2.9158(4) Å) bond, respectively (Chart 11).…”

“… In the case of M = Mo, W, a triangular metal cluster was first formed, which under CO undergoes reversible opening to the chain complexes 17 and 18 , respectively . A similar behavior was observed with dppa as bridging ligand …”