Tungsten complexes derived from o-phenylenediamine: methoxo and dialkylhydroxylaminato species

Abstract

The interaction of WCl₆ and o-phenylenediamine (1,2-diaminobenzene, H₂pda) in PrⁱOH affords the binuclear compound {WCl₃[1-(HN),2-(H₂N)C₆H₄]}₂[µ-1,2-(N)C₆H₄]1. A similar reaction in methanol gives only a methoxide complex, W₂Cl₃(OMe)₅(µ-OMe)₂2. Interaction of WCl₄(PMe₃)₃ with H₂pda in PrⁱOH gives WCl₂[1,2-(HN)₂C₆H₄](PMe₃)₃3. Interaction of WOCl₄ and H₂pda in tetrahydrofuran (thf) with a solution of LiNMe₂ prepared in situ from Me₂NH and commercial LiBuⁿ in hexanes (which contain 2-methylpentane) gives rise to a remarkable compound 4 that has a 1,5-benzodiazepinium cation (made independently as its chloride) and an anion [W₂Cl₄O(ONMe₂)₅]^– that provides the first examples of unidentate and bridging dimethylhydroxylaminate(1–) ligands (both through O). Interaction of WOCl₄ and LiONR₂(R = Et or PhCH₂) in thf forms WO₂(ONR₂)₂5 and 6. In complex 1 the metal centres, which are related by symmetry, have octahedral co-ordination with a mer arrangement of the three chlorides. The link to the bridging µ-C₆H₄(N)₂ ligand involves a WN double bond [1.75(2)Å]. The chelating 1-(HN),2-(H₂N)C₆H₄ gives W–N bond lengths of 1.92(2)(amido) and 2.29(2)Å(amino); the latter bond is trans to the multiply bonded imine function. In the methoxide 2 the metal centres are inequivalent: W(1) has two terminal chlorides and two terminal methoxides (mutually trans) whilst W(2) has one terminal chloride and three methoxides. The methoxides. The methoxide bridges show slight asymmetry. The metal–metal distance [2.733(3)Å] is consistent with the presumed W–W single bond. In compound 4 the dinuclear anion contains two structurally equivalent metal atoms, each with two terminal chlorides and two terminal dimethylhydroxylaminato groups. The hydroxylaminato and oxo bridges are symmetrical. The organic cation, evidently formed by reactions of WOCl₄ with 2-methylpentane in the solvent, has also been structurally characterised as the chloride salt. In compound 5 the W–O bonds of the η²-diethylhydroxylaminato groups are slightly shorter than the W–N bonds: 1.97(1)(av.)vs. 2.14(1)Å(av.).