Synthesis and Structure Determinations of Complexes Containing a Five-Membered Lactam Structure Based on Organohydrazido(2−) Ligands¹

Acid-catalyzed reactions of the hydrazido(2−) complexes cis, mer -[WX 2 (NNH 2 )(PMe 2 Ph) 3 ] (X = Cl, Br) with phthalaldehyde gave the (phthalimidin-2-yl)imido complexes cis, mer -[WX 2 (NNCH 2 C 6 H 4 CO)(PMe 2 Ph) 3 ], via the condensation of the terminal NH 2 group with one of the formyl groups and the following cyclization to form a phthalimidine ring. Crystal structure of the chloro complex 3a was unambiguously determined by X-ray analysis. Reaction of 3a with HBr liberated the (phthalimidin-2-yl)imido ligand as 2-aminophthalimidine in moderate yield, while treatment of 3a with KOH in THF selectively cleaved the N−N bond to give phthalimidine. A similar condensation of the hydrazido(2−) complex trans -[WF(NNH 2 )(dppe) 2 ] + ( 8a +; dppe = Ph 2 PCH 2 CH 2 PPh 2 ) with phthalaldehyde resulted in the formation of the diazoalkane complex trans -[WF(NN CHC 6 H 4 CHO)(dppe) 2 ] + . However, further treatment of the latter complex with AlCl 3 afforded the corresponding (phthalimidin-2-yl)imido complex trans -[WF(NNCH 2 C 6 H 4 CO)(dppe) 2 ] + . When 8a + and its molybdenum analogue were reacted with 2,5-dimethoxy-2,5-dihydrofuran in the presence of a catalytic amount of acid, trans -[MF(NNCH CHCH 2 CO)(dppe) 2 ] + ( 11 +; M = Mo, W) was formed as the kinetic product, which gradually isomerized to the thermodynamically more stable compound trans -[MF(NNCH 2 CH CHCO)(dppe) 2 ] + ( 12 + ). Both 11 + and 12 + (M = W) were crystallographically characterized, and the mechanism for the isomerization of 11 + to 12 + was proposed based on the results of the 1 H NMR measurements.