ORGANOMETALLIC NITROSYL CHEMISTRY .43. SYNTHESIS AND CHARACTERIZATION OF CHIRAL MOLYBDENUM AND TUNGSTEN NEUTRAL COMPLEXES CONTAINING ETA-2-BENZYL LIGANDS

Reaction of Cp'M(NO)Cl2 (Cp' = Cp (eta-5-C5H5) or Cp* (eta-5-C5Me5); M = Mo or W) with 2 equiv of p-XylMgCl (p-Xyl = p-MeC6H4CH2) affords the corresponding bis(p-xylyl) complexes in good yields. Subsequent treatment of the Cp'M(NO)(CH2Ar)2 compounds (CH2Ar = CH2Ph or p-Xyl) with HCl produces the new isolable Cp'M(NO)(CH2Ar)Cl species. These, in turn, undergo metathesis reactions with RMgCl or R2Mg(dioxane)2 reagents and convert to Cp'M(NO)(CH2Ar)R (R = CH2SiMe3, CH2CMe3 (Npt), or C6H4CH3 (p-Tol)). All new complexes isolated during this work have been fully characterized by conventional spectroscopic methods. Single-crystal X-ray crystallographic analyses have been performed on two prototypal complexes, namely Cp*Mo(NO)(CH2Ph)Cl and Cp*Mo(NO)(CH2Ph)(CH2SiMe3). Crystal data for Cp*Mo(NO)(CH2Ph)Cl: a = 9.3451 (16) angstrom, b = 11.8954 (9) angstrom, c = 15.6511 (17), beta = 100.176 (9)-degrees, Z = 4, space group P2(1)/n, number of unique reflections 6159, number of variables 218, R(F) = 0.033, R(wF) = 0.047. Crystal data for Cp*Mo(NO)(CH2Ph)(CH2SiMe3): a = 8.3901 (10) angstrom, b = 9.3937 (17) angstrom, c = 14.9556 (19), alpha = 74.017 (11)-degrees, beta = 98.009 (9)-degrees, gamma = 86.849 (12)-degrees, Z = 2, space group P1, number of unique reflections 5092, number of variables 358, R(F) = 0.023, R(wF) = 0.031. Both compounds possess normal three-legged piano-stool molecular geometries, the most chemically interesting features involving their eta-2-benzyl ligands. The intramolecular dimensions of the Mo(eta-2-CH2Ph) groupings in both structures are essentially identical and indicate that the eta-2-benzyl groups in these diamagnetic complexes function as three-electron ligands via C-Mo sigma bonds involving their methylene and ipso carbon atoms. All evidence points to the presence of the eta-2-benzyl ligands as being the principal factor responsible for the stability of the 18-electron Cp'M(NO)(CH2Ar)X (X = Cl or R) complexes. In solutions these complexes are stereochemically nonrigid, and Cp*Mo(NO)(CH2Ph)Cl has been subjected to a variable-temperature H-1 NMR study.