Thermal exchange reactions of (eta(5)-C5R5)Mn(CO)(2)(L-W) compounds (L-W = weakly-bound ligand) in supercritical fluid solution and the isolation of (eta(5)-C5R5)Mn(CO)(2)(eta(2)-H-2) using high-pressure flow and semiflow reactors

摘要

Supercritical fluids offer unrivaled opportunities for manipulating compounds with labile ligands, This paper reports a study of ligand-exchange reactions in supercritical solution aimed at evaluating compounds as precursors for the thermal synthesis of CpMn(CO)(2)(eta(2)-H-2) in supercritical CO2 (scCO(2)), A series of (eta(5)-C5R5)Mn(CO)(2)(L-w) compounds have been prepared, where L-w is a weakly-bound ligand (i.e., (PrCN)-Pr-n, eta(2)-H2C=CHOEt (EVE), and eta(2)-H-SiEt3), and their reactions with C2H4, N-2, and H-2 have been studied in supercritical solution, This is the first time that the EVE ligand has been used with the (eta(5)-C5R5)Mn(CO)(2) moiety. We describe flow and semiflow reactors for carrying out these thermal reactions in supercritical solution, Both of these reactors exploit rapid expansion of the supercritical fluid to enable these labile complexes to be isolated from supercritical solution without loss of the labile ligand. The reaction of Cp*Mn(CO)(2)(eta(2)-HSiEt3) with H-2 is found to be the best route for the thermal synthesis of Cp*Mn(CO)(2)(eta(2)-H-2), both in terms of purity and convenience. There are clear opportunities for scale-up, We find that exchange between these ligands is so facile that conditions in supercritical solution can be varied sufficiently to favor the interchange between almost any pair of the labile ligands, This ease of interchange has important implications for homogeneous catalysis in supercritical solution. [References: 31]