Unprecedented Transformation of Diiron Bridging Vinyliminium Ligands into Carboxyamido- and Alkylphosphonate-Vinylalkylidenes

The vinyliminium complexes [Fe2{mu-?1:?3-C(R')=C(R')C=N(Me)(R)}(mu-CO)(CO)(Cp)2][SO3CF3] (R = Me, R' = CO2Me, 6a; R = R' = Me, 6b; R = Me, R' = Et, 6c; R = Xyl, R' = CO2Me, 6d; R = Xyl, R' = Me, 6e; Xyl = 2,6-Me2C6H3) upon treatment with NaH in thf fragmented to afford the metallacyclopentadienone complexes [Fe(CO)(Cp){CN(Me)(R)C(R')C(R')C(O)}] (7a7e). When the reaction of 6c with NaH was carried with thf direct from the bottle (i.e., not freshly distilled), the product was the vinylalkylidene complex[Fe2{mu-?1:?3-C(Et)C{C(O)NMe2}C(H)(Me)}(mu-CO)(CO)(Cp)2] (8), which contains a carboxyamido group. The formation of 8 implies deprotonation of the bridging ligand and oxygen addition to the iminium carbon of 6c with rearrangement of the bridging coordination. Reaction of the vinyliminium complexes [Fe2{mu-?1:?3-C(R')=C(R?)C=N(Me)(R)}(mu-CO)(CO)(Cp)2][SO3CF3] (R = Me, R' = R? = CO2Me, 6a; R = R' = Me, R? = H, 6f; R = R' = Me, R? = H, 6g; R = Xyl, R = CH2Ph, R' = CO2Me, R? = H, 6h) with NaH and P(OMe)3 afforded the corresponding alkylphosphonate-vinylalkylidene complexes [Fe2{mu-?1:?3-C(R')C(R?)C{P(O)(OMe)2}N(Me)(R)}(mu-CO)(CO)(Cp)2] (9a9d). The reaction can be considered an Arbuzov-like rearrangement involving an iminium group. The crystal structures of 8 and 9c were determined X-ray diffraction.