GENERATION AND REACTIVITY OF CP-ASTERISK-W(NO)(CH(2)SIME(3))H, A 16-VALENCE-ELECTRON ALKYL HYDRIDE COMPLEX

Treatment of solutions of CpW(NO)(CH(2)SiMe(3))(2) with H-2 generates in situ the reactive 16-valence-electron alkyl hydride CpW(NO)(CH(2) SiMe(3))H, formed by hydrogenolysis of one of the W-C sigma-bonds of t he dialkyl reactant. The Lewis-acidic hydride complex has not yet been isolated, but its existence has been inferred on the basis of the var ied chemical reactions that it undergoes when generated in the presenc e of reactive substrates. PPh(3) affords the orthometalated complex Cp W(NO)(H)(PPh(2)C(6)H(4)) as a yellow crystalline solid probably via t he 18-electron adduct CpW(NO)(CH(2)SiMe(3))(PPh(3))H. Consistently, t he same reaction effected with PPh(3)-d(15) results in complete deuter ation of the hydride position in the product. Acyclic, conjugated dien es such as butadiene or 2,3-dimethyl-1,3-butadiene afford CpW(NO)(eta (4)-trans-diene) complexes. The characteristic chemistry of CpW(NO)(C H(2)SiMe(3))H is, however, dominated by the ability of its W-H link to insert unsaturated linkages, the regioselectivity of the insertions i ndicating that the hydride Ligand is hydridic in nature. For instance, insertion of acetonitrile affords the ethylideneamido complex Cp()W( NO)(CH(2)SiMe(3))(N=CHMe), which is isolable as a diastereomeric pair. Similarly, insertions of organic reagents containing carbonyl (O=C) o r imine (HN=C) functional groups produce the corresponding alkyl alkox ide or alkyl amide products, respectively, in virtually quantitative y ields. Phenylacetylene affords the novel alkyl alkenyl compound CpW(N O)(CH(2)SiMe(3))(CPh=CH2), which is thermally unstable and isolable in only low yields. Insertions into the W-H bond by other olefinic subst rates are successful only if the unsaturated hydrocarbon also contains a Lewis-base functional group. Thus, propargylamine and allylamine pr oduce the related metallacyclic complexes CpW(NO)(CH(2)SiMe(3))(NH2CH 2CHCH) and CpW(NO)(CH(2)SiMe(3))(NH2CH2CH2CH2), respectively. Treatme nt of CpW(NO)(CH(2)SiMe(3))(2) with H-2 in the presence of allyl alco hol does not produce an oxometallacycle, but rather affords the allyla lkoxo complex resulting from the alcohol simply functioning as a proto nic acid toward the dialkyl reactant. The solid-state molecular struct ures of CpW(NO)(CH(2)SiMe(3))(N=CHMe) and Cp*W(NO)(CH(2)SiMe(3))(NH2C H2CH2CH2) have been established by single-crystal X-ray crystallograph ic analyses. Crystals of CpW(NO)(CH(2)SiMe(3))(N=CHMe) are monoclinic of space group P2(1)/n: a = 9.515(2) Angstrom; b = 21.946(3) Angstrom ; c = 9.552(2) Angstrom; Z = 4; V = 1946.8 Angstrom(3); T = 200 K; R(f ) = 0.029 for 2035 data (I-0 greater than or equal to 2.5 sigma(I-0)) and 106 variables. Crystals of CpW(NO)(CH(2)SiMe(3))(NH2CH2CH2CH2) ar e orthorhombic of sp ace group P2(1)2(1)2(1): a 11.417(4) Angstrom; b = 13.178(2) Angstrom; c 13.804(4) Angstrom; Z = 4; V = 2076.9 Angstrom (3); T = 200 K; R(f) = 0.020 for 2420 data (I-0 greater than or equal to 2.5 sigma(I-0)) and 208 variables.