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

Tungsten(O) carbene complexes of the type (OC)(5)W=C(NMeCH2CH=CHCH2OH)R 2 (R = Me: 2a; R = Ph: 2b) were generated by aminolysis Of (OC)(5)W=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)(4)W=C(eta(2)- NMeCH2CH=CHCH2OH)R (4) were obtained in good yields upon photo-decarbonylation of 2. Deprotonation/silylation of the complexes (OC)(4)M=C(eta(2) -NMeCH2CH=CHCH2OH)Me (M = Cr: 3a; M = W: 4a) with one equivalent of "BuLi/Me3SiCl gave (OC4 M=C(eta(2) -NMeCH2CH=CHCH2OSiMe3)CH3 (M=Cr: 5; M=W: 6), whereas with two equivalents of "BuLi/Me3SiCl complexes (OC)(4)M=C(eta(2)-NMeCH2CH=CHCH2OSiMe3)CH2SiMe3 (M = Cr: 7; M = W: 8) were formed. Hydrolysis of the latter yielded selectively (OC)(4)M=C(eta(2) -NMeCH2CH=CHCH2OH)CHSiMe3 (M = Cr: 9; M = W: 10). The complexes 1-10 were analyzed in solution by one- and two-dimensional NMR spectroscopy (H-1, C-13, Si-29, H-1/H-1 COSY, H-1/H-1 NOESY, C-13/H-1 HET-COR). (C) 2004 Elsevier B.V. All rights reserved.