SYNTHESIS AND REACTIVITIES OF TUNGSTEN COMPLEXES WITH DISUBSTITUTED TRIMETHYLENEMETHANE LIGANDS

Treatment of the tungsten carbonyl beta-(chlorocarbonyl)allyl complex CP(CO)2W(eta3-CH2C-(COCl)CH2) with 2 equiv of organolithium reagent followed by hydrolysis affords the allyl complex CP(CO)2W(eta3-CH2C(CR2OH)CH2) (2a, R = Me; 2b, R = C6H5). Treatment of complex 2 with HBF4 causes dehydration and produces the cationic tungsten disubstituted-trimethylenemethane complexes [Cp(CO)2W(eta4-CH2C(CR2)CH2)]BF4 (3a, R=Me; 3b, R=C6H5). Hydride regiospecifically attacks the disubstituted peripheral carbon atom of 3a, producing Cp(CO)2W-(eta3-CH2C(C(H)Me2)CH2) (4). The methyl protons of complex 3a, being acidic, are readily exchanged by deuterium in the presence of NaBr and acetone-d6. Thus, the stable beta-isopropenylallyl complex Cp(CO)2W(eta3-CH2C(C(=CH2)CH3)CH2) (5) is prepared from deprotonation of 3a by a number of bases, including CP(CO)3W-. Reaction of 5 with tetracyanoethylene proceeds via a [4 + 2] cycloaddition to yield a complex with a cyclohexyl moiety. Complexes 3a and 3b have been characterized by single-crystal X-ray diffraction analysis. Crystal data for 3a: space group P2(1)/n, a = 7.465(4) angstrom, b = 14.177(5) angstrom, c = 14.242(7) angstrom, beta = 96.99(4)-degrees, V = 1496(1) angstrom3, Z = 4, R = 0.043, R(w) = 0.039 based on 2109 reflections with I > 3sigma(I). Crystal data for 3b: space group Pna2(1), a = 10.000(3) angstrom, b = 14.306(3) angstrom, c = 14.747(6) angstrom, V = 2110(1) angstrom3, Z = 4, R = 0.036, R(w) = 0.028 based on 1433 reflections with I > 2sigma(I).