Bis(organoimido)-complexes of tungsten(IV): the crystal and molecular structures of tetrachlorobis(t-butylamine)bis(t-butylimido)bis(µ-p-tolylimido)-ditungsten(VI) and tetrachlorobis(µ-phenylimido)-bis(t-butylamine) bis(t-butylimido)ditungsten(VI)
Abstract
The tungsten(VI) organoimido complexes [{WCl4(NR)}2](R = Ph, C6H4Me-p, Pri, or Me) were treated with the silylamines Me3SiNHR″(R″= Ph, But, Pri, or Et) to form the dimeric complexes [{WCl2(NR)(NR″)(NH2R″)}2], containing terminal and bridging organoimido ligands, cis-oriented chloro ligands, and co-ordinated amine. [{WCl2(NPh)(NBut)(NH2But)}2] was also obtained from the reaction of [{WCl4(NPh)}2] with NH2But. Spectral studies suggest that these complexes arise from two cis-oriented organoimido groups by an inter-ligand proton-transfer process which proceeds regardless of the size of the group R. The structure of [{WCl2(NC6H4Me-p)(NBut)(NH2But)}2] was determined by X-ray crystallography and shown to have distorted edge-shared bioctahedral geometry with terminal t-butylimido groups and bridging unsymmetrical arylimido groups and with the longer W–N bridge bonds trans to the terminal t-butylimido group. The t-butylamine ligands are involved in intramolecular N–H ⋯ Cl bridging within the dimeric unit, which explains some striking features found in the 1H n.m.r. spectrum. Full details are also given of the crystal structure of [{WCl2(NPh)(NBut)(NH2But)}2].