Synthesis and reactivity of new rhenium(I) complexes containing iminophosphorane-phosphine ligands: Application to the catalytic isomerization of propargylic alcohols in ionic liquids

摘要

[ReBr(CO)_5] reacts with the iminophosphorane-phosphine ligands Ph_2PCH_2P(=NR)Ph_2 (R = P(=O)(OEt)_2 (1a), P(=O)(OPh)_2 (1b), P(=S)(OEt)_2 (1c), P(=S)(OPh) _2 (1d), 4-C_6F_4CHO (1e), 4-C_6F _4CN (1f), 4-C_5F_4N (1g)) affording the neutral complexes [ReBr(κ~2-P,X-Ph_2PCH_2P{=NP(=X) (OR)_2}Ph_2)(CO)_3] (X = O, R = Et (2a), Ph (2b); X = S, R = Et (2c), Ph (2d)) and [ReBr{κ~2-P,N-Ph _2PCH_2P(=NR)Ph_2}(CO)_3] (R = P(=O)(OEt)_2 (3a), P(=O)(OPh)_2 (3b), 4-C_6F _4CHO (3e), 4-C_6F_4CN (3f), 4-C_5F _4N (3g)). The reactivity of the cationic complex [Re(κ ~3-P,N,S-Ph_2PCH_2P{=NP(=S)(OPh)_2}Ph_2)(CO)_3][SbF_6] (4d) has been explored allowing the synthesis of the cationic [Re(L)(κ~2-P,S- Ph_2PCH_2P{=NP(=S)(OPh)_2}Ph_2)(CO) _3][SbF_6] (L = acetone (5a), CH_3C≡N (5b), pyridine (5c), PPh_3 (5d)) and the neutral [ReY(κ~2-P, S-Ph_2PCH_2P{=NP(=S)(OPh)_2}Ph_2)(CO) _3] (Y = Cl (6a), I (6b), N_3 (6c)) complexes. The catalytic activity of complex 4d in the regioselective isomerization of terminal propargylic alcohols HC≡CCR~1R~2(OH) into α,β-unsaturated aldehydes R~1R'2C=CHCHO or ketones R~3R~4C=CR~1COMe (if R~2 = CHR~3R~4) under neutral conditions in ionic liquids has being studied. Isolation and X-ray characterization of the key intermediate rhenium(I) oxocyclocarbene complex [Re{=C(CH_2)_3O} (κ~2-P,S-Ph_2PCH_2P{=NP(=S)(OPh) _2}Ph_2)(CO)_3][SbF_6] (5e) seems to indicate that the catalytic reaction proceeds through tautomerization of the terminal alkynols to yield vinilydene-type species.