The formation of dimetallocycles from reactions of alkynes with (η-C 5Me 5) 2Rh 2(CO) 2; X-ray structure of [(η-C 5Me 5) 2Rh 2(η-CO) {μ-η 2,η 2-C(O)C 2-(CF 3) 2}

Abstract

The complexes (η-C 5Me 5) 2Rh 2(μ-CO) {μ-η 2,η 2-C(O)CRCR} are obtained from reactions between (η-C 5Me 5) 2Rh 2(CO) 2 and the alkynes RCCR (R  CF 3, CO 2Me, or Ph) at 25°C. The molecular geometry of the complex with R  CF 3 has been established by X-ray diffraction; the bridging 'ene-one' unit adopts a μ-η 2,η 2 conformation. Other complexes isolated from these reactions include (η-C 5Me 5)Rh(C 6R 6) (R  CF 3, CO 2Me), (η-C 5Me) 2Rh 2(C 4R 4) (R  CO 2Me) and (η-C 5Me 5) 2Rh 2(CO 2C 2R 2) (R  Ph). The reaction between (η-C 5Me 5) 2Rh 2(CO) 2 and C 6F 5CCC 6F 5 gives (η-C 5Me 5) 2Rh 2(CO) 2(C 6F 5C 2C 6F 5). Mononuclear complexes such as (η-C 5Me 5)Co(C 4R 4CO) are the major products isolated from reactions between (η-C 5Me 5) 2CO 2(CO) 2 and alkynes at 25°C.