Synthesis and Structures of Tungsten (1-Pyridinio)imido Complexes and Their Facile N−N Bond Cleavage<sup>1</sup>
作者:Hiroshige Ishino、Shin'ichi Tokunaga、Hidetake Seino、Youichi Ishii、Masanobu Hidai
DOI:10.1021/ic981116n
日期:1999.5.1
The tungsten (1-pyridinio)imido complexes [WX(2)(NNC(5)H(4)OMe)(L)(PMe(2)Ph)(2)](+), [WX(2)(NNC(5)H(2)Me(3))(L)(PMe(2)Ph)(2)](+), and [WCl(2)NNC(5)H(2)(COOEt)(2)Ph}(L)(PMe(2)Ph)(2)](+) (X = Cl, Br; L = CO, C(2)H(4), PMe(2)Ph) were synthesized by the reaction of the salts of pyrylium cations with the hydrazido complexes [WX(2)(NNH(2))(L)(PMe(2)Ph)(2)], which were derived from the dinitrogen complex cis-[W(N(2))(2)(PMe(2)Ph)(4)]. The complexes obtained were characterized by spectroscopic measurements as well as crystallographic studies of cis,mer-[WBr(2)(NNC(5)H(4)OMe-4)(PMe(2)Ph)(3)][PF(6)], cis, trans-[WCl(2)(NNC(5)H(4)OMe-4)(CO)(PMe(2)Ph)(2)][ClO(4)], cis, trans- [WCl(2)(NNC(5)H(2)Me(3)-2,4,6)(CO)(PMe(2)Ph)(2)][OTf] (OTf = OSO(2)CF(3)), and cis,trans-[WCl(2)(NNC(5)H(4)OMe-4)(C(2)H(4))(PMe(2)Ph)(2)][ClO(4)], which revealed that the N-N bond distances of these (1-pyridinio)imido complexes are shorter than those of the trialkyl- or unsubstituted hydrazidium complexes so far reported. The (1-pyridinio)imido complexes with a pi-acidic ligand (CO or C(2)H(4)) undervent smooth N-N bond cleavage on reaction with cobaltocene under ambient conditions to liberate the pyridines in moderate to high yields. In some reactions that were conducted in the presence of HNEt(3)-Cl, the corresponding imido (NH) complexes were recovered as the metal products. The (1-pyridinio)imido complexes also reacted with KOH in MeOH to give the pyridines and ammonia in high yields. These reactions provide the first examples of N-N bond cleavage of well-defined hydrazidium complexes and accomplish the synthesis of pyridines from molecular nitrogen under mild conditions.