Complexes of trivalent phosphorus derivatives. XIV. Metal complexes of diphenylphosphinophenylacetylene

Abstract

The following metal complexes of diphenylphosphinophenylacetylene ((C6H5)2PCCC6H5) were prepared by conventional methods: [(C6H5)2PCCC6H5]3CuCl, [(C6H5)2PCCC6H5]AuCl, [(C6H5)2PCCC6H5]2MCl2 (M = Pd or Pt), [(C6H5)2PCCC6H5]3NiCO, [(C6H5)2PCCC6H5RhCOCl]2, trans-[(C6H5)2PCCC6H5]2Fe(CO)3, trans-[(C6H5)2PCCC6H5]2Cr(CO)4, cis- and trans-[(C6H5)2PCCC6H5]3Cr(CO)3, cis-[(C6H5)2PCCC6H5]3M(CO)3, (M = Mo and W), C5H5Col2[C6H5)2PCCC6H5], C5H5FeCOBr[(C6H5)2PCCC6H5], and C5H5Mo(CO)2(COR)[(C6H5)2PCCC6H5] (R = CH3 or C6H5CH2). The reaction of cycloheptatrienentricarbonylchromium with (C6H5)2PCCC6H5 at room temperature yielded the expected cis-[(C6H5)2PCCC6H5]3Cr(CO)3 but this reaction when carried out at 80° gave some of the corresponding trans-isomer as well as the cis-isomer thereby indicating a thermal rearrangement. Similarly, the reaction of norbornadienetetracarbonylchromium with (C6H5)2PCCC6H5 gave trans-[(C6H5)2PCCC6H5]2Cr(CO)4 rather than the corresponding cis isomer. The infrared-active γ(CC) frequencies in the various metal complexes of diphenylphosphinophenylacetylene can be used as indicators of the relative amounts of retrodative π-bonding from filled metal d orbitals to the empty phosphorus d orbitals of the phosphine ligand. Using this frequency as an indicator, retrodative π-bonding is shown to be weaker in tetrahedral complexes than in octahedral, trigonal bipyramidal, or square planar complexes.