Syntheses and some reactions of complexes containing carbon chains capped by ferrocenyl and W(CO) 3Cp groups

Abstract

The preparation and some reactions of W{(CC) n }(CO)Cp [ n=1–4 ( 1– 4 )] are described. For n=1 and 2, Cu(I)-catalysed reactions between Fc(CC) n H ( n=1, 2) and WCl(CO) 3Cp gave compounds 1 and 2, respectively, while Cu(I)Pd(0)-catalysed coupling between FcCCI and W(CCCCH)(CO) 3Cp gave 3. Oxidative coupling of FcCCCCH and W(CCCCH)(CO) 3Cp gave 4, together with both homo-coupled products. Electrochemical studies showed that the Fc/Fc + oxidation potential increases by about 50 mV for each CC triple bond added to the carbon chain. Reactions with Co 2(μ-dppm) m (CO) 8−2 m ( m=0, 1) gave complexes 6– 10 in which the Co 2 fragment is attached to the sterically least-hindered CC triple bond. The novel vinylidene cluster Co 2W(μ 3-CCPhFc)(μ 3-PPhCH 2PPh 2)(CO) 5Cp ( 5) was also obtained from 1 and Co 2(μ-dppm)(CO) 6. Reactions of 1 with tetracyanoethene (tcne) gave the cyclobutenyl ( 11) and buta-1,3-dien-2-yl ( 12) complexes by cycloaddition to the CC triple bond and subsequent ring-opening. In the presence of silica gel, 12 reacts with MeOH to give the chelating imino complex W{C[C(CN) 2C(OMe)NH]CFcC(CN) 2}(CO) 2Cp ( 13). With 2 and 3, addition of tcne to the CC triple bond one removed from the tungsten centre gave buta-1,3-dien-2-yl complexes 14 and 15. X-ray crystal structure determinations have been carried out on 2, 5 , 7, 8 and 10– 14.