Molecular structure and dynamical behavior of seven-coordinate Mo(CO)3X2(Ar2POPAr2) complexes

Abstract

Direct reaction of elemental halogens with Mo(CO)4(R2POPR2) yielded seven-coordinate Mo(II) complexes of type Mo(CO)3X2(R2POPR2) (R = phenyl or p-tolyl, X = I or Br). The structures of Mo(CO)3I2(Ph2POPPh2) (I) and Mo(CO)3Br2(tolyl2POPtolyl2) (II) have been determined by X-ray diffraction methods. Crystal data: MoI2P2O4 C27H2O·C2H2Cl4, complexI, triclinic space group P1-; a = 10.019(1), b = 11.876(1), c = 15.342(2)Å; α = 73.96(1)°, β = 79.12(1)°, γ = 78.19(1)°, Zcalc. = 1.88 Mg m−3· The structure was solved by MULTAN on the basis of 5169 reflections to a final R value of 0.035. Crystal data: MoBr2P2O4C31H28, complexII, monoclinic space group P21/c, a = 15.932(2), b = 9.847(1), c = 21.360(2)Å, β = 106.58(1)°, Z = 4, Dcalc. = 1.62 Mg m−3· The structure was solved using MULTAN on the basis of 1588 reflections to a final R value of 0.097. Both structures approximate a pentagonal bipyramidal coordination geometry around the metal center. This stereochemistry is in accord with Kepert's prediction for chelate normalized bites of less than 1.1 (1.03 and 1.05, respectively, for the POP ligands). The equatorial plane contains both halides, the two phosphorus donors, and a carbonyl. The axial carbonyls are distorted from linearity by 8.5(2) and 13(2)°, respectively. Variable-temperature31P NMR studies of these and the related MO(CO)3I2(Ph2PCH2PPh2) Complex confirmed fluxional behavior. Furthermore, for each of the iodo complexes, equilibration with a second solution isomer was observed.