Isomers of Re(CO)3(CNt-Bu)LX: synthetic strategies starting from MnRe(CO)8(CNt-Bu)L and Re(CO)4LX (X=halogen; L=Group 15 donor ligand)

Article abstract of DOI:10.1016/0022-328X(94)87272-4

Reaction of Re(CO)4LX (L=PMePh2, PMe2Ph, PPh3, P(OMe)3, P(Oi-Pr)3, P(O-o-tol)3; X=Br, I) with t-BuNC in the presence of PdO catalyst gave the new complexes Re(CO)3(CNt-Bu)LX in high yield ( >60percent).The new complexes were shown by spectroscopic techniques (IR, 1H and 31P NMR) to comprise a mixture of mer and fac isomers.The mer/fac ratio decreased with reaction temperatures (e.g.L=P(OMe)3; 10 deg C, ratio=3; 45 deg C, ratio=0.25).At high temperatures (90 deg C) isomerization of the mer to the fac isomers (L=PMe2Ph, P(OMe)3) occurred, suggesting that the mer isomer was the kinetic product of the catalyzed reaction.Reactions induced by Me3NO gave similar effects.Halogen cleavage of MnRe(CO)8(CNt-Bu)L, prepared from MnRe(CO)9(CNt-Bu) and L in the presence of Me3NO, yielded either one or two isomers of Re(CO)3(CNt-Bu)(L)X (X=I, Br; 40percent yield).For large L (e.g.PPh3) a new mer isomer with L trans to X was synthesized, and characterized by IR and NMR spectroscopy.For small L (e.g.P(OMe)3) a mixture of the two different mer products was obtained.The product isomer ratio was determined predominantly by the position of L in the starting dimer. Key words: Rhenium; Carbonyl; Catalysis; Heterobimetallics; Substitution