Tetraethylammonium fluoride as a convenient source of hydroxide ions in acetonitrile solution. Its reaction with [Fe(η-C5H5)(CO)2(L)]+ salts and [Fe(η-C5H5)(CO)2X] complexes

In acetonitrile solution, [Et 4 N]F·2.5H 2 O acts as a convenient source of hydroxide ions for use in organometallic chemistry. Within 20 min, at room temperature, it converts [Fe(η-C 5 H 5 )(CO) 2 (L)] + salts (molar ratio 1:1) to [Fe 2 (η-C 5 H 5 ) 2 (CO) 3 (L)] (L=CO, CNMe and PPh 3 ) complexes in good yields with the evolution of CO 2 and, when L=CO, CO. Under the same conditions it converts [Fe(η-C 5 H 5 )(CO) 2 Cl] (molar ratio 1:2 or, better, 1:3) to [Fe 2 (η-C 5 H 5 ) 2 (CO) 3 (NCMe)]. Other [Fe(η-C 5 H 5 )(CO) 2 X] (X=Br or I) react only slowly to give [Fe 2 (η-C 5 H 5 ) 2 (CO) 4 ]. Other routes to [Fe 2 (η-C 5 H 5 ) 2 (CO) 3 (PPh 3 )] and [Fe 2 (η-C 5 H 5 ) 2 (CO) 3 (NCMe)] involve prolonged photolysis and give impure or non-isolable products. This route gives them as analytically pure solids in high yields. It is proposed that in acetonitrile solutions, the F − ions react with H 2 O to give HF and OH − in a reaction driven by the strength of the HF bond and the lack of anion solvation in acetonitrile. The OH − ions then attack the [Fe(η-C 5 H 5 )(CO) 2 (L)] + cations at CO with the evolution of CO 2 to give the [Fe(η-C 5 H 5 )(CO)(L)] − which subsequently displaces L from the cations.