The reactions of dicarbonylbis(phosphorus donor) iron fragments with tertiary propargyl alcohols

Article abstract of DOI:10.1016/S0022-328X(97)00012-0

The reaction of the mixture of Fe(CO)₂(PEt₃)₂N₂ (1a) and [Fe(CO)₂(PEt₃)₂]₂N₂ (1b) with propargyl alcohols HC ≡ C-CR₁R₂OH (R₁=R₂=Me; R₁=Me, R₂=Et; R₁=Me, R₂=iPr; R₁=Me; R₂=tBu; R₁=R₂=tBu; R₁=R₂=Ph) in THF affords isolable Fe(CO)₂(PEt₃)₂(H)(C≡C-CR₁R₂OH) complexes (R₁=R₂=Me 2a; R₁=Me, R₂=Et 2b; R₁=Me, R₂=iPr 2c; R₁=Me, R₂=tBu 2d; R₁=R₂=tBu 2e; R₁=R₂=Ph 2f). Complexes 2a-d underwent dehydration in hexane in the presence of silylated silica to yield vinylvinylidene complexes Fe(CO)₂(PEt₃)₂=C=C(H)R′C-CR″R? (R′=Me, R″, R?=H 3a; R′=R″=Me, R?=H 3b; R′=R?=Me, R″=H 3c; R′=R″=R?=Me 3d; R′=tBu, R″=R?=H 3e). 2e and 2f did not eliminate water. However, double deprotonation with n-BuLi and deoxygenation with acetyl chloride ultimately produced then their formal products of dehydration: di(t-butyl) or diphenylallenylidene(dicarbonyl)bis(triethylphosphine)iron compounds 4a or 4b. The reactions of dicarbonylbis(trimethylphosphite)iodoferrate 1b with the same propargyl alcohol derivatives HC=C-CR₁R₂OH as mentioned above resulted in the formation of dicarbonylbistrimethylphosphite(vinylidene)iron derivatives Fe(CO)₂[P(OMe)₃]₂=C=C(H)CR₁R₂OH (R₁=R₂=Me) 7a; R₁=Me; R₂=Et 7b; R₁=Me, R₂=iPr; 7c; R₁=Me, R₂=tBu 7d; R₁=R₂=tBu 7e; R₁=R₂=Ph 7f). Dehydration processes of 7a-f in the presence of Al₂O₃ or SiO₂ led to allenylidene or vinylvinylidene complexes Fe(CO)₂[P(OMe)₃]₂ =C=C=CR₁R₂ (R₁=Me, R₂=tBu 8a; R₁R₂=tBu 8b; R₁=R₂=Ph 8c) or Fe(CO)₂[P(OMe)₃]₂=C=C(H)CR′=CR″R? (R′=Me, R″=R?=H 9a; R′=Et, R″=R?=H 9b; R′=R″=Me, R?=H 9c; R′=R?=Me, R″=H 9d; R′=iPr, R″=R?=H 9e; R′=R″=R?=Me 9f; R′=tBu, R″=R?=H 9g). 8c was also prepared by an alternative route starting from 1c and HC≡C-CPh₂OAc which provided a higher yield. 7e and 8b were characterized by single crystal X-ray diffraction studies.