Synthesis and solid-state isomerisation reactions of diag- and lat-(η5-C5H4R)Re(CO)(L)X2

Reaction of diag- or lat- (i.e. trans or cis)(eta(5)-C5H4R)Re(CO)(2)X-2 (R = Me, t-Bu, SiMe3; X = Br, I) with isocyanides, phosphites and triphenyl phosphine proceeded rapidly at room temperature (r.t.) in the presence of Me3NO to give (eta(5)-C5H4R)Re(CO)(L)X-2 (L = CNC6H3Me2, P(OMe)(3), P((OPr)-Pr-i)(3), P(OPh)(3), PPH3) in good yields (typically > 75%) with the diagonal isomer as the dominant ( > 90%) product. The diag-(eta(5)-C5H4R)Re(CO)(L)X-2 isomer were readily converted into the lateral isomer in excellent yield (> 70%) by directly heating solid diag-(eta(5)-C5H4R)Re(CO)(L)X-2 under nitrogen below its melting point. Solution phase isomerisation in CHCl3 or C6D6 (r.t., visible light irradiation) also proceeded from the diag to the lat isomer. The solid-state reaction between diag-(eta(5)-C5H4Me)Re(CO)[P(OPh)(3)]Br-2 and excess NaI surprisingly gave diag-(eta(5)-C5H4Me)Re(CO)(2)I-2 in quantitative yield, revealing both Re-P and Re-Br bond cleavage. The new complexes, diag- and lat-(eta(5)-C5H4R)Re(CO)(L)X-2, have been fully characterized by elemental analysis and IR and NMR spectroscopy. (C) 1998 Elsevier Science S.A. All rights reserved.