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

The preparation and some reactions of W{(CC)n}(CO)Cp [n=1–4 ( , , and )] are described. For n=1 and 2, Cu(I)-catalysed reactions between Fc(CC)nH (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 Co2(μ-dppm)m(CO)8−2m (m=0, 1) gave complexes , , , and in which the Co2 fragment is attached to the sterically least-hindered CC triple bond. The novel vinylidene cluster Co2W(μ3-CCPhFc)(μ3-PPhCH2PPh2)(CO)5Cp (5) was also obtained from 1 and Co2(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.