REACTIVITY OF A TUNGSTEN CARBONYL SIGMA-ALLENYL COMPLEX - REGIOSPECIFIC C-C BOND FORMATION AND STRUCTURE OF AZATUNGSTACYCLOBUTANE AND OXATUNGSTACYCLOPENTENE COMPLEXES

Mild thermolysis of Cp(CO)3WCH2C=CH (1a; Cp = eta5-C5H5) in benzene gives Cp(CO)3-WCH=C=CH2 (2). Reaction of 2 with RNH2 provides the azatungstacyclobutane Cp(CO)2W-[eta2-CH(CONHR)CHCH3(NHR)] (3a, R = CH3; 3b, R = C6H5; 3c, R = CH2C6H5; 3d, R = CHMe2) as the major product. Complex 3 is formed by the additions of one amine to the terminal CO and another amine to the beta-carbon of the allenyl group, along with the coupling of the resulting amido group and the alpha-carbon of the C3 unit. The allylic complex Cp(CO)2W[eta3-CH2CHCH(CONHR)] (4) is also isolated as a minor product. Treatment of 2 with alcohol in benzene affords a mixture of Cp(CO)2W[eta3-CH2CHCH(COOR')] (5a, R' = CH3; 5b, R' = C2H5; 5c, R' = C3H3) and Cp(CO)2W[eta2-C(CH3)=CHC(O)OR'] (6a, R' = CH3; 6b, R' = C2H5; 6c, R' = C3H3). If this reaction is carried out in THF, only 5 is obtained, and in acetonitrile 6 is the only product. In the reactions of 2 leading to 3-6, the regiospecific C-C bond formation occurs at the alpha-carbon. In contrast, the similar coupling reaction of the propargyl complex takes place at the beta-carbon. The structures of 3a and 6c have been confirmed by X-ray diffraction analyses. Crystal data for 3a: space group C2/c, a = 20.551-(8) angstrom, b = 11.100(4) angstrom, c = 12.784(3) angstrom, beta = 94.60(3)-degrees, V = 2907(2) angstrom3, Z = 8, R = 0.031, R(w) = 0.024, based on 1889 reflections with I > 2sigma(I). Crystal data for 6c: space group P2(1)/c, a = 10.7202(9) angstrom, b = 16.0349(14) angstrom, c = 8.4403(12) angstrom, beta = 102.234(9)-degrees, V = 1417.9(3) angstrom3, Z = 4, R = 0.019, R(w) = 0.015, based on 2027 reflections with I > 2sigma(I).