REACTION OF ACETYLENE WITH A DIRUTHENIUM(0) COMPLEX - EASY INTERCONVERSION OF DIMETALLACYCLOBUTENE AND DIMETALLACYCLOPENTENONE COMPLEXES

[Ru2(mu-CO)(CO)4(mu-dppm)2], 1, reacts with excess HC=CH to give the d imetallacyclobutene [RU2(mu-CH=CH)(CO)4(mu-dppm)2], 2, and CO as the p roducts of kinetic control. If the reaction is carried out in a closed flask, a further reaction occurs by addition of CO to 2 to give the d imetallacyclopentenone [Ru2(mu-CH=CHCO)(CO)4(mu-dppm)2], 3. Complex 3 decomposes on heating to give 2 and CO. The nature of these reactions has been elucidated by using C-13 labeled reagents and monitoring the reactions by NMR. Complex 3 has been characterized by an X-ray structu re determination [3.2CH2CI2, Monoclinic, space group Cc, a = 19.500(2) angstrom, b = 17.146(3) angstrom, c = 17.349(2) angstrom, V = 101.21( 1)-degrees, V = 5690(1) angstrom3, Z = 4, R = 0.0499, R2 = 0.0520].