Insertion of CO and SO2 into the N-N bond of [Fe2(CO)6(μ-Ph2N2)]

The N-N bond of the azobenzene ligand in [Fe-2(CO)(6)(mu-Ph2N2)] (1) is unusually labile. In addition to being cleaved by incorporation of CO or H-2 it also inserts CO resulting from phosphine substitution at the iron atoms. Complexes [Fe-2(CO)(5)(PR3)(mu-PhN-CO-NPh)] (2a,b) and [Fe-2(CO)(4){P(OMe)(3)}(2)(mu-PhN-CO-NPh)] (2c) are formed with PPh3 and P(OMe)(3). Bis(diphenylphosphino)methane produces [Fe-2(CO)(4)(eta(1)-dppm)(2)(mu-PhN-CO-NPh)] (2d). All these complexes also result from [Fe-2(CO)(6)(mu-PhN-CO-NPh)] (2) and the corresponding phosphine. Reaction of 1 with SO2 yields the insertion product [Fe-2(CO)(6)(mu-PhN-SO2-NPh)] (4). Complex 4 does not react with CO at temperatures up to its decomposition point. Its thermal degradation in the absence of CO, however, produces the CO insertion product 2, which involves SO2 elimination with intermediate re-formation of 1. Treatment of 4 with phosphines results only in CO displacement, producing [Fe-2(CO)(5)P(OMe)(3)(mu-PhN-SO2-NPh)] (4b), [Fe-2(CO)(4)(PR3)(2)(mu-PhN-SO2-NPh)] (4a,c, PR3 = PPh3 or P(OMe)(3)), and [Fe-2(CO)(4)(mu-dppm)(mu-PhN-SO2-NPh)] (4d). For comparison with the basic structures of 1, 2 and 4 two CO insertion products and two SO2 insertion products were characterized by crystal structure determinations. (C) 1998 Elsevier Science S.A. All rights reserved.