New silane-induced carbonyl activation in [(.eta.5-H3CC5H4)Mn(CO)2.cntdot.THF]: formation of the cyclic bis(.mu.-carbyne) complex [cyclic] (.eta.5-H3CC5H4)(CO)Mn(.mu.-COSiH(t-Bu)2)2Mn(CO)(.eta.5-H3CC5H4) and the carbon-carbon coupling reaction of the siloxy-carbyne ligands | doi.page