Synthesis, structure and reactivity of novel pyridazine-coordinated diiron bridging carbene complexes

Abstract

[{µ-(Pyridazine-N¹:N²)}Fe₂(µ-CO)(CO)₆] (1) reacts with aryllithium reagents, ArLi (Ar = C₆H₅, m-CH₃C₆H₄) followed by treatment with Me₃SiCl to give the novel pyridazine-coordinated diiron bridging siloxycarbene complexes [(C₄H₄N₂)Fe₂{µ-C(OSiMe₃)Ar}(CO)₆] (2, Ar = C₆H₅; 3, Ar = m-CH₃C₆H₄). Complex 2 reacts with HBF₄·Et₂O at low temperature to yield a cationic bridging carbyne complex [(C₄H₄N₂)Fe₂(µ-CC₆H₅)(CO)₆]BF₄ (4). Cationic 4 reacts with NaBH₄ in THF at low temperature to afford the diiron bridging arylcarbene complex [(C₄H₄N₂)Fe₂{µ-C(H)C₆H₅}(CO)₆] (5). Unexpectedly, the reaction of 4 with NaSCH₃ under similar conditions gave the bridging arylcarbene complex 5 and a carbonyl-coordinated diiron bridging carbene complex [Fe₂{µ-C(SCH₃)C₆H₅}(CO)₇] (6), while the reaction of NaSC₆H₄CH₃-p with 4 affords the expected bridging arylthiocarbene complex [(C₄H₄N₂)Fe₂{µ-C(SC₆H₄CH₃-p)C₆H₅}(CO)₆] (7), which can be converted into a novel diiron bridging carbyne complex with a thiolato-bridged ligand, [Fe₂(µ-CC₆H₅)(µ-SC₆H₄CH₃-p)(CO)₆] (8). Cationic 4 can also react with the carbonylmetal anionic compound Na₂[Fe(CO)₄] to yield complex 5, while the reactions of 4 with carbonylmetal anionic compounds Na[M(CO)₅(CN)] (M = Cr, Mo, W) produce the diiron bridging aryl(pentacarbonylcyanometal)carbene complexes [(C₄H₄N₂)Fe₂-{µ-C(C₆H₅)NCM(CO)₅}(CO)₆] (9, M = Cr; 10, M = Mo; 11, M = W). The structures of complexes 2, 5, 6, 8, and 9 have been established by X-ray diffraction studies.