Reactions of 1,4-diphenylbut-1-en-3-yne and 1,4-diferrocenylbuta-1,3-diynewith Ru-3(CO)(10)(mu-dppm). Unusual structures of the clusters Ru-3(CO)(5)(mu-CO)(mu-dppm){mu(3)-C4Ph2(CH=CHPh)(2)} (two isomers) and Ru-3(CO)(5)(mu-CO)(mu-dppm)(mu(3)-C(4)Fc(2)(C equivalent to CFc)(2)}