ORGANOMETALLIC NITROSYL CHEMISTRY .53. SYNTHESIS, CHARACTERIZATION, AND PROPERTIES OF 16-ELECTRON CP-ASTERISK-M(NO)(ARYL)2 (M = MO, W) COMPLEXES

Treatment of Cp*M(NO)Cl2 (Cp* = eta-5-C5Me5; M = Mo, W) in THF at low temperatures with equimolar amounts of diarylmagnesium reagents, (aryl)2Mg.x(dioxane), affords the diaryl complexes Cp*M(NO)(aryl)2 (aryl = Ph, o-tolyl, or p-tolyl), which are isolable in moderate yields and have been fully characterized by conventional spectroscopic methods. In addition, single-crystal X-ray crystallographic analyses have been performed on both o-tolyl complexes. Crystal data for Cp*Mo(NO)(o-tolyl)2 (3): a = 11.570 (2) angstrom, b = 10.128 (3) angstrom, c = 18.439 (4) angstrom, beta = 92.50 (2)-degrees, Z = 4, space group P2(1)/a (No. 14), R(F) = 0.030, R(wF) = 0.033 for 3387 reflections with I greater-than-or-equal-to 3-sigma(I). Crystal data for Cp*W(NO)(o-tolyl)2 (6): a = 11.612 (3) angstrom, b = 10.168 (5) angstrom, c = 18.250 (3) angstrom, beta = 91.87 (2)-degrees, Z = 4, space group P2(1)/a (No. 14), R(F) = 0.037, R(wF) = 0.040 for 3019 reflections with I greater-than-or-equal-to 3-sigma(I). Complexes 3 and 6 are isostructural and isomorphous and possess three-legged piano-stool molecular structures. Their intramolecular metrical parameters are comparable to those exhibited by the related dialkyl complex CpW(NO)(CH2SiMe3)2, the most notable difference being the C(aryl)-M-C(aryl) angle in both 3 and 6, which is significantly greater than the C(alkyl)-M-C(alkyl) angle in the dialkyl species. The IR and electrochemical properties of the Cp*M(NO)(aryl)2 complexes indicate that their metal centers are more electron deficient than those in comparable Cp*M(NO)(alkyl)2 (CP' = CP (eta-5-C5H5), CP*; M = Mo, W) complexes. This greater Lewis acidity is also manifested by the increased stability of the 1:1 adducts formed between the diaryl complexes and typical Lewis bases.