Synthesis and selective silylation of ω-hydroxy functionalized (η 2-alkenyl)carbene complexes of chromium(0) and tungsten(0) Part 11. The chemistry of metallacyclic alkenylcarbene complexes

Abstract

Tungsten(0) carbene complexes of the type (OC) 5WC(NMeCH 2CHCHCH 2OH)R 2 (R=Me: 2a; R=Ph: 2b) were generated by aminolysis of (OC) 5WC(OMe)R with cis-NHMeCH 2CHCHCH 2OH. Like their Cr-congeners 1, complexes 2 exist at room temperature as mixtures of Z- and E-isomers with regard to the C–N bond. The metallacyclic complexes (OC) 4WC(η 2-NMeCH 2CHCHCH 2OH)R ( 4) were obtained in good yields upon photo-decarbonylation of 2. Deprotonation/silylation of the complexes (OC) 4MC(η 2-NMeCH 2CHCHCH 2OH)Me (M=Cr: 3a; M=W: 4a) with one equivalent of n BuLi/Me 3SiCl gave (OC) 4MC(η 2-NMeCH 2CHCHCH 2OSiMe 3)CH 3 (M=Cr: 5; M=W: 6), whereas with two equivalents of n BuLi/Me 3SiCl complexes (OC) 4MC(η 2-NMeCH 2CHCHCH 2OSiMe 3)CH 2SiMe 3 (M=Cr: 7; M=W: 8) were formed. Hydrolysis of the latter yielded selectively (OC) 4MC(η 2-NMeCH 2CHCHCH 2OH)CH 2SiMe 3 (M=Cr: 9; M=W: 10). The complexes 1– 10 were analyzed in solution by one- and two-dimensional NMR spectroscopy ( 1H, 13C, 29Si, 1H/ 1H COSY, 1H/ 1H NOESY, 13C/ 1H HETCOR).