TRANSITION METAL-SUBSTITUTED PHOSPHANES, ARSANES AND STIBANES - 65 - CHIRAL MODIFICATION OF DICARBONYL(CYCLOPENTADIENYL)FERRIO-PHOSPHANES -SYNTHESIS AND DETERMINATION OF THE INVERSION BARRIER IN PHOSPHIDO-PHOSPHORUS

The inversion barriers of dicarbonyl(cyclopentadienyl)ferrio-phosphane s are determined using chirally modified cyclopentadienyl-ligands. Syn thesis is achieved by deprotonation of the cationic primary or seconda ry phosphane iron complexes {RC5Hn(OC)(2)[H(R)(Mes)P]Fe}BF4 (R = H, P h; R = NM = Neomenthyl; n = 4; R = H; R* = Pi = Pinen-fused; n = 3) ( 4a-c) with (KOBu)-Bu-t to give RC5Hn(OC)(2)Fe-P(Mes)R (R* = NM, Pi; R = H, Ph) (6a-c). Reaction of 6a with MeI yields {NMC5H4(OC)(2)[H(Me)( Mes)P]Fe}I (8), which is converted with (KOBu)-Bu-t to NMC5H4(OC)(2)Fe -P(Mes)Me (9). The inversion barrier of the ferrio-phosphanes is deter mined by NMR-spectroscopy to be 17.3 (6a), 16.4 (6b), 18.0 (6c) and > 16.8 (9) kcal mol(-1). (C) 1998 Elsevier Science S.A. All rights reser ved.