Versatile reactions of a para-bromophenylacetylide iron(II) derivative and X-ray structure of the fluoro analogue.: Synthesis of new redox-active organoiron(II) synthons

The synthesis of the new (eta(2)-dppe)(n(5)-C5Me5)Fe-CdropC-1,3-(C6H4X) (m-2a/2b; X = F/Br) and (n(2)-dppe)(eta(5)-C5Me5)Fe-CdropC-1,4-(C6H4F) (2a) (2c) complexes, as well as the solid-state structure of the known (eta(2)-dppe)(eta(5)-C5Me5)Fe-CdropC-1,4-(C6H4F) (2a) complex are described. The catalytic coupling reactions of the bromo complexes with various alkynes were next investigated. Starting from the known (eta(2)-dppe)(eta(5)-C5Me5)Fe-CdropC-1,4-(C6H4Br) complex (2b), the synthesis of the (eta(2)-dppe)(eta(5)-C5Me5)FeCdropC-1,4-(C6H4)-CdropC-H complex (6d) and of the corresponding silyl-protected precursors (eta(2)-dppe)(eta(5)-C5Me5)Fe-CdropC-1,4-(C6H4)CdropC-SiR3 (6b/6c; R = Pr-1/Me) are reported. By use of lithium-bromine exchange reactions on 2b, the silyl-(7a; E = Si; R = Me) and tin- (7b-7d; E = Sn; R = Me, Bu, Ph) substituted analogues (eta(2)-dppe)(eta(5)-C5Me5)Fe-CdropC-1,4-(C6H4)ER3 are also isolated. The spectroscopic and electrochemical characterisations of all these new Fe(II)/Fe(III) redox-active building blocks are presented and the electronic substituent parameters for the ''(eta(2)-dppe)(eta(5)-C5Me5)Fe-CdropC" group are determined by means of F-19-NMR. (C) 2002 Elsevier Science B.V. All rights reserved.