REACTIVITY OF THE LEWIS-ACIDS CP-ASTERISK-M(NO)(CH2CME3)CL [M = MO, W] AND RELATED COMPLEXES

Treatments of CpM(NO)Cl2 [Cp* = eta5-C5Me5; M = Mo, W] with 0.5 equiv of (Me3CCH2)2Mg.X(dioxane) in THF at low temperatures affords the mon oalkylated complexes, CpM(NO)(CH2CMe3)Cl (1, 1'). Exposure to a secon d 0.5 equiv of (Me3CCH2)2Mg.X(dioxane) at higher temperatures produces the dialkyl complexes, CpM(NO)(CH2CMe3)2 (2,2'). Utilizing the two s eries of CpM(NO)Cl2, Cp*M(NO)(CH2CMe3)Cl and Cp*M(NO)(CH2CMe3)2 compl exes, the relative electron deficiencies in these 16-electron complexe s can be assessed spectroscopically and electrochemically. Without exc eption, the Mo complexes are the stronger Lewis acids. Also, the monon eopentyl derivatives for both metals are more reactive toward a variet y of substrates than are their bis(neopentyl) analogues. Complexes 1 a nd 1' serve as precursors to mixed alkyl and alkyl aryl complexes (3, 3', 4, 4') and yield metal-centered adducts with PMe3 and pyridine (5, 5', 6, 6'). CO and CNCMe3 readily insert into the M-C bonds of 1 and 1'. The insertion products, CpM(NO)(C{E}CH2CMe3)Cl (7, 7', E = O; 8, 8', E = NCMe3), have eta2-acyl and -iminoacyl ligands, the former bein g confirmed by the solid-state structural analysis of CpMo(NO)(eta2-C {O}CH2CMe3)Cl (7). Crystal data for 7: a = 15.226(2) angstrom, b = 12. 376(2) angstrom, c = 19.641(2) angstrom, beta = 95.921(8)degrees, Z = 8, space group P2(1)/n, R(F) = 0.032, R(wF) = 0.032 for 7215 reflectio ns with I greater-than-or-equal-to 3sigma(I). The chloride ligands in CpM(NO)(CH2CMe3)Cl are easily abstracted by Ag+ in NCMe to form alkyl cations of the type [CpM(NO)(CH2CMe3)(NCMe)x]BF4 (9, x = 1; 9', x = 2). The acyl complex, CpW(NO)(eta2-C{O}CH2CMe3)Cl, reacts with PMe3 t o form the metal-centered eta1-acyl adduct (10'). The other phosphine complexes, CpM(NO)(CH2CMe3)(Cl)(PMe3), are readily dehydrohalogenated by lithium diisopropylamide in THF to afford cyclometalated complexes of the type (eta5,eta1-C5Me4CH2)M(NO)(CH2CMe3)(PMe3) (11,11'). The so lid state structure of the W species (11') has been established. Cryst al data for 11': a = 14.323(1) angstrom, b = 16.861(2) angstrom, c = 8 .511(2) angstrom, Z = 4, space group P2(1)2(1)2(1), R(F) = 0.030, R(wF ) = 0.024 for 2420 reflections with I greater-than-or-equal-to 3sigma( I). The structures of 7 and 11' were solved by conventional heavy atom methods and were refined by full-matrix least-squares procedures.