Hydroformylation of 2,4,4-trimethyl-1-pentene catalyzed by the high nuclearity carbonyl cluster [Rh 12(CO) 30] 2−

Abstract

The salt Na 2[Rh 12(CO) 30] was used for the hydroformylation of 2,4,4-trimethyl-1-pentene in tetrahydrofuran under high pressures of CO H 2 (20–120 atm) in the temperature range 300–400 K. The reaction is highly chemioselective, approaching 100% selectivity to 3,5,5-trimethylhexanal, and only traces of 2,4,4-trimethylpentane and 3,5,5-trimethyl-1-hexanol are produced. Typical turnover numbers are 100–1000 mol olefin/mol cluster. The cluster precursor was transformed into derivatives of lower nuclearity, [Rh 6(RCO)(CO) 15] − (R = (CH 3) 3CCH 2CH(CH 3)CH 2) or [Rh 5(CO) 15] −, as shown by infrared spectroscopy. The turnover numbers increase on lowering the catalyst to olefin ratio, and the order of the reaction with CO is positive. The dependencies of the rates versus CO and catalyst concentrations suggest that, irrespective of the actual species present in solution, all the clusters behave in the same way, probably through a CO-driven equilibrium of fragmentation.