Hydrazido(2–)-complexes of molybdenum and tungsten formed from dinitrogen complexes by protonation and ligand exchange

Abstract

A number of new hydrazido(2–)-complexes [MX₂(NNH₂)(PMe₂Ph)₃](A; M = Mo or W, X = Cl, Br, or I) and trans-[MX(NNH₂)(PMe₂Ph)₄]X (B; M = W) have been prepared by reaction of concentrated HX with cis-[M (N₂)₂(PMe₂Ph)₄] in methanol. The addition of various ligands L to complexes (A) has given a series of complexes of the following types: (B : M = Mo or W), when L = PMe₂Ph; (C), [MX(NNH₂)(PMe₂Ph)₃L]X, when L = various pyridine bases or dimethylformamide; (D), [M(NNH₂)(quin)(PMe₂Ph)₃]X, when L = quinolin 8-olate ion (quin); and specifically [WBr(NNH₂)(S₂CNMe₂)(PMe₂Ph)₂](L = S₂CNMe₂) when M = W and X = Br. The (B)-type complex trans-[WF(NNH₂)(PMe₂Ph)₄][BF₄] is obtained by treatment of cis-[W(N₂)₂-(PMe₂Ph)₄] with H F in methanol in a borosilicate-glass reaction vessel. The salts (E), [WX(NNH₂)(PMe₂Ph)₃L]-[BPh₄](M = W), areobtained by reaction of Na[BPh₄] with (C; M = W) exceptfor L = pyridine-2-thiol (2HS-py) when [W(NNH₂)(2S-py)(PMe₂Ph)₃][BPh₄] results. The complexes trans-[MI(NNH₂)(dppe)₂]I (dppe = Ph₂PCH₂CH₂PPh₂) have been prepared by treatment of trans-[M(N₂)₂(dppe)₂] with aqueous Hl in tetrahydro-furan. Spectroscopic (i.r. and n.m.r.) data for these complexes are discussed in terms of their structures. In dichloromethane solution, complexes (A), (C), and (D) are electrochemically oxidised by one unit, but cannot be reduced.