Evaluation of the 2,6-diisopropylphenylimido ligand as a steric force in d1 and d2 monomeric octahedral complexes of tungsten

Reduction of [{WCl4(NC6H3Pri2-2,6)}2] with 2 equivalents of Na–Hg amalgam in the presence of phosphines gave the d1 complexes [WCl3(NC6H3Pri2-2,6)L2](L = PMe3, PMe2Ph or PMePh2). The crystal structure of [WCl3(NC6H3Pri2-2,6)(PMe3)2]1 shows the 2,6-diisopropylphenylimido ligand exerts a greater trans influence than a phenylimido ligand but only slightly more steric pressure. Solutions of complex 1 react with air to give [WCl3(NC6H3Pri2-2,6)(PMe3)(OPMe3)]2 for which the crystal structure shows the OPMe3 ligand lying trans to the imido ligand. Reduction of [{WCl4(NC6H3Pri2-2,6)}2] with 4 equivalents of Na–Hg amalgam in the presence of phosphines gave the d2 complexes [WCl2(NC6H3Pri2-2,6) L3](L = PMe3 or PMe2Ph). Complex [WCl2(NC6H3Pri2-2,6)(PMe3)3]3 reacts with alkynes L′ to give the complexes [WCl2(NC6H3Pri2-2,6) L′(PMe3)2](L′= PhC2Ph, MeC2Me or PhC2H) for which 1H and 13C-{1H} NMR spectral data were obtained. The crystal structure of [WCl2(NC6H3Pri2-2,6)(PhC2H)(PMe3)2]6 shows cis-chloro ligands, trans-phosphines and mutually cis-imido and alkyne ligands. The C(6) isopropyl group rotates to minimise the isopropyl group and PhC2H interaction. The complex [WCl2(NC6H3Pri2-2,6)(PhC2Ph)(PMe2Ph)2] can be prepared but not [WCl2(NC6H3Pri2-2,6)(PhC2Ph)(PMePh2)2]. Reduction of [WCl3(NC6H3Pri2-2,6)(PMe3)2](L′= CH2CH2 or CH2CHMe). A more bulky organoimido ligand or a large phosphine is needed to exert steric pressure in all the complexes prepared.