PREPARATION AND PROPERTIES OF MOLYBDENUM AND TUNGSTEN DINITROGEN COMPLEXES .39. ALKENYLDIAZENIDO COMPLEXES OF MOLYBDENUM AND TUNGSTEN DERIVED FROM DINITROGEN COMPLEXES - THEIR SYNTHESIS, CHARACTERIZATION, AND NOVEL REACTIVITIES

Alpha-deprotonation of molybdenum or tungsten diazoalkane complexes trans-[MF(NN=CR1CHR2R3)(dpe)2][BF4] (1, M = Mo or W, dpe = Ph2PCH2CH2PPh2) by LDA (lithium diisopropylamide) or NaN(SiMe3)2 provides a general route to alkenyldiazenido complexes trans-[MF(NNCR1=CR2R3)(dpe)2] (2). When 1-diazopropane complexes 1b and 1i were deprotonated, the Z-isomers of alkenyldiazenido complexes were predominantly obtained (Z/E = 6-12). The molecular structure of trans-[WF(NNCH=CMe2)(dpe)2].C6H6 (2f.C6H6) was fully characterized by X-ray analysis: C62H61N2WP4F, space group P1BAR (triclinic); a = 13.398 (8) angstrom, b = 19.051 (13) angstrom, c = 11.950 (8) angstrom, alpha = 98.30 (7)-degrees, beta = 114.54 (5)-degrees, gamma = 81.81 (6)-degrees, Z = 2, R = 0.070, R(w) = 0.082. Relatively long N=N and C=C bond distances (1.29 (3), 1.38 (4) angstrom) and short C-N bond distance (1.26 (3) angstrom) in complex 2f.C6H6 as well as the IR data of complexes 2 indicated considerable contribution of a resonance structure where the terminal carbon of the C=C bond is negatively charged. This has been substantiated by the finding that complexes 2 reacted rapidly with alkyl halides or heterocumulenes such as isocyanates and diphenylketene to give the corresponding C-alkylated or acylated diazoalkane complexes in moderate to high yields, respectively. The deprotonation-alkylation reaction of diazoalkane complexes 1 proceeded regioselectively on the carbon atom cis to the lone pair on the nitrogen of the C=N bond, and the repeated deprotonation-alkylation reactions led to the selective alpha,alpha-dialkylation of the diazoalkane ligand. Acylation with excess aryl isocyanates gave the alpha,alpha-diacylated complexes, whose molecular structure was confirmed by X-ray analysis of trans-[WF{NN=CMeCH(CONHPh)2}(dpe)2][BF4] (7a): formula C69H64O2N4WP4F5B, space group P2(1)2(1)2(1) (orthorhombic); a = 13.764 (4) angstrom, b = 35.917 (7) angstrom, c = 12.986 (4) angstrom, Z = 4, R = 0.064, R(w) = 0.069. Reactions of 2 with aldehydes yielded the Aldol-type condensation products. On the other hand, reactions with I2 or CuCl2 caused the oxidative coupling to give novel mu-bis(diazo)alkane complexes, and their dimeric structure was revealed by the X-ray diffraction study of threo-, trans,trans-[(dpe)2WF(NN=CHCHMeCHMeCH=NN)FW(dpe)2][BF4]2.6(C6H6) (threo-14b.6(C6H6)): formula C146H142N4W2P8F10B2, space group C2/c (monoclinic); a = 32.899 (3) angstrom, b = 13.091 (1) angstrom, c = 32.866 (4) angstrom, beta = 109.782 (7)-degrees, Z = 4, R = 0.077, R(w) = 0.078. Electrochemical study of 2 indicated that the oxidative coupling proceeded by the coupling of a cationic species by the one-electron oxidation of 2.