CARBONYL EXCHANGE WITH CO-13 OF RH6(CO)16 AND ITS BIDENTATE PHOSPHORUS LIGAND SUBSTITUTION PRODUCTS

Reactions of Rh6(CO)16 with bidentate ligands, Ph2P(CH2)nPPh2(n = 2: diphosE = 1,2-bis(diphenylphosphino)ethane; n = 4: diphosB =1,4-bis(diphenylphosphino)butane) gave RH6(CO)12(diphosB)2, Rh6(CO)15(diphosE) and Rh6(CO)13(diphosE)3. In these clusters, each phosphorus donor site of diphosB is coordinated to adjacent rhodium atom, while only one donor site of diphosE is coordinated to a rhodium atom. The other site is believed to be bound to a face-bridging carbonyl group. Carbonyl exchange with carbon monoxide in these diphos-substituted clusters is affected by the mode of coordination of the ligands. In the diphosB-substituted cluster, both terminal and face bridging carbonyl groups readily exchanged with 13CO at 20°C, while in both diphosE mono- and tri-substituted clusters only a few percent of the terminal carbonyls exchanged and the face-bridging carbonyls were not observed to undergo exchange at all under similar conditions. © 1979.