(Ethynylferrocenyl)phosphine ruthenium complexes in catalytic β-oxopropyl benzoate formation

The synthesis of a series of (ethynylferrocenyl)phosphino ruthenium compounds of type (FcC C)R2P(RuCl2(eta(6)-p-cymene)) (3a, R = C6H5; 3b, R = 2-CH3C6H4; 3c, R = (C4H3O)-C-c; 3d, R = t-Bu; 3e, R = (C6H11)-C-c; p-cymene = 1-(C3H7)-C-i-4-CH3-C6H4; Fc = Fe(eta(5)-C5H4)(eta(5)-C5H5)) and (RuCl2(eta(6)-p-cymene))(FcC C)P(C CPPh2(RuCl2(eta(6)-p-cymene)))(2) (10) resulting from the addition of ferrocenylphosphines P(C CFc)R-2 (1a-1e) or P(C CFc)(C CPPh2)(2) (9) to [RuCl2(eta(6)-p-cymene)](2) (2) is described. The structures of 3b, 3c and 10 in the solid state are reported confirming the expected tetrahedral coordination sphere about the phosphorus atom as well as the "piano-stool" arrangement about the ruthenium atom(s). Ruthenium complexes 3 and 10 are catalytically active under mild conditions in the alkyne-to-carboxylic acid coupling as it was shown for the reaction of propargyl alcohol with benzoic acid. A comparison with literature known [RuCl2(PR3)(eta(6)-p-cymene)] catalysts is presented. (C) 2012 Elsevier B.V. All rights reserved.