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

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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.).

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