Rearrangement of Closo-3,3-(PPh3)2-3-H-1-(R)-3,1,2-IrC2B9H10 to Closo-2,2-(PPh3)2-H-8-(R)-2,1,8-IrC2B9H10. Synthesis and X-Ray Structure of Closo-2,2-(PPh3)2-2-H-8-(C6H5)-2,1,8-IrC2B9H10.

摘要

During the continuing investigation of the chemistry of the known alkene hydrogenation and isomerization catalyst, closo-3,3-(PPh3)2-3-H-3,1,2-RhC2B9H111 (Ia), the iridum congener and its derivatives, closo-3,3-(PPH3)2-1-(R)-3-H-3,1,2-IrC2B9H10, R = H (IIa)1, R = C6H5 (IIb)2, R = CH3 (IIc)2 and R = 1'-(closo-1,2-C2B10H11) (IId)2 were prepared and notable differences between the reactivity of the Rh and Ir systems were observed. Syntheses of IIb-d, the exo-nido complexes derived from these compounds, and the dimeric complex derived from IIa will be reported in a future paper. Although thermally induced migration of carbon atoms over the surface of polyhedral cobaltacarboranes is a well-established phenomenon, 3 similar isomerization reactions are not so well known for other metallacarboranes. The formation of 2,1,8 isomers of icosahedral metallocarboranes have been observed previously 3 only during high temperature vapor phase thermal isomerization of (n-C5H5)Co(C2B9H11) isomers. The 2,1,8 isomer of this system was observed as the dominant kinetic product (74%) arising from the 3,1,2 isomer during such reactions at temperatures near 500 degrees C; however, three other isomers were also detected in the reaction mixture. Here we report the ready polytopal rearrangement of IIb and IIc under mild thermolytic conditions in toluene solvent at the reflux temperature.