Synthesis and selective silylation of ω-hydroxy functionalized (η²-alkenyl)carbene complexes of chromium(0) and tungsten(0). Part 11. The chemistry of metallacyclic alkenylcarbene complexes

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Schobert, Rainer ; Schmalz, Thomas:
Synthesis and selective silylation of ω-hydroxy functionalized (η²-alkenyl)carbene complexes of chromium(0) and tungsten(0). Part 11. The chemistry of metallacyclic alkenylcarbene complexes.
In: Journal of Organometallic Chemistry. Bd. 689 (2004) Heft 10 . - S. 1771-1779.
ISSN 1872-8561
DOI: https://doi.org/10.1016/j.jorganchem.2004.02.032

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Abstract

Tungsten(0) carbene complexes of the type (OC)5WC(NMeCH2CHCHCH2OH)R 2 (R=Me: 2a; R=Ph: 2b) were generated by aminolysis of (OC)5WC(OMe)R with cis-NHMeCH2CHCHCH2OH. 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(η2-NMeCH2CHCHCH2OH)R (4) were obtained in good yields upon photo-decarbonylation of 2. Deprotonation/silylation of the complexes (OC)4MC(η2-NMeCH2CHCHCH2OH)Me (M=Cr: 3a; M=W: 4a) with one equivalent of nBuLi/Me3SiCl gave (OC)4MC(η2-NMeCH2CHCHCH2OSiMe3)CH3 (M=Cr: 5; M=W: 6), whereas with two equivalents of nBuLi/Me3SiCl complexes (OC)4MC(η2-NMeCH2CHCHCH2OSiMe3)CH2SiMe3 (M=Cr: 7; M=W: 8) were formed. Hydrolysis of the latter yielded selectively (OC)4MC(η2-NMeCH2CHCHCH2OH)CH2SiMe3 (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).