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

The synthesis of a series of (ethynylferrocenyl)phosphino ruthenium compounds of type (FcC C)R 2 P(RuCl 2 ( η 6 - p -cymene)) ( 3a , R = C 6 H 5 ; 3b , R = 2-CH 3 C 6 H 4 ; 3c , R = c C 4 H 3 O; 3d , R = t -Bu; 3e , R = c C 6 H 11 ; p -cymene = 1- i C 3 H 7 -4-CH 3 -C 6 H 4 ; Fc = Fe( η 5 -C 5 H 4 )( η 5 -C 5 H 5 )) and (RuCl 2 ( η 6 - p -cymene))(FcC C)P(C CPPh 2 (RuCl 2 ( η 6 - p -cymene))) 2 ( 10 ) resulting from the addition of ferrocenylphosphines P(C CFc)R 2 ( 1a – 1e ) or P(C CFc)(C CPPh 2 ) 2 ( 9 ) to [RuCl 2 ( η 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 [RuCl 2 (PR 3 )( η 6 - p -cymene)] catalysts is presented.