Evaluation of the 2,6-diisopropylphenylimido ligand as a steric force in d1 and d2 monomeric octahedral complexes of tungsten
作者:George R. Clark、Alastair J. Nielson、Clifton E. F. Rickard
DOI:10.1039/dt9950001907
日期:——
Reduction of [WCl4(NC6H3Pr2i-2,6)}(2)] with 2 equivalents of Na-Hg amalgam in the presence of phosphines gave the d(1) complexes [WCl3(NC6H3Pr2i-2,6)L(2)] (L = PMe(3), PMe(2)Ph or PMePh(2)). The crystal structure of [WCl3(NC6H3Pr2i-2,6)(PMe(3))(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(NC(6)H(3)Pr(2)(-)2,6)(PMe(3))(OPMe(3))] 2 for which the crystal structure shows the OPMe(3) ligand lying trans to the imido ligand. Reduction of [WCl4(NC6H3Pr2i-2,6)}(2)] with 4 equivalents of Na-Hg amalgam in the presence of phosphines gave the d(2) complexes [WCl2(NC(6)H(3)Pr(2)(-)2,6)L(3)] (L = PMe(3) or PMe(2)Ph). Complex [WCl2(NC6H3Pr2i-2,6)(PMe(3))(3)] 3 reacts with alkynes L' to give the complexes [WCl2(NC6H3Pr2i-2,6)L'(PMe(3))(2)] (L' = PhC(2)Ph, MeC(2)Me or PhC(2)H) for which H-1 and C-13-H-1} NMR spectral data were obtained. The crystal structure of [WCl2(NC6H3Pr2i-2.6)(PhC(2)H)(PMe(3))(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 PhC(2)H interaction. The complex [WCl2(NC6H3Pr2i-2.6)(PhC(2)Ph)(PMe(2)Ph)(2)] can be prepared but not [WCl2(NC6H3Pr2i-2,6)(PhC(2)Ph)(PMePh(2))(2)]. Reduction of [WCl3(NC6H3Pr2i-2.6)(PMe(3))(2)] by Na-Hg amalgam in the presence of olefins gave the complexes [WCl2(NC6H3Pr2i-2,6)L'(PMe(3))(2)] (L' = CH2CH2 or CH(2)CHMe). A more bulky organoimido ligand or a large phosphine is needed to exert steric pressure in all the complexes prepared.