Ferrocenylalkynes as ligands in transition metal complexes

Abstract

Several ferrocenylalkynes have been prepared and their reaction with dicobalt octacarbonyl led to the formation of [Co₂(CO)₆(μ-η² ∶ η²-ethynylferrocene)] 1, [Co₂(CO)₆(μ-η² ∶ η²-1,4-bis(ferrocenyl)butadiyne)] 2, [(Co₂(CO)₆)₂(μ-η² ∶ η²,μ-η² ∶ η²-1,4-bis(ferrocenyl)butadiyne)] 3, [Co₂(CO)₆(μ-η² ∶ η²-1-ferrocenylethynyl-2-hydro-1,2-dihydro-[60]fullerene)] 4, [Co₂(CO)₆(μ-η² ∶ η²-1,1’-bis(phenylethynyl)ferrocene)] 5 and [(Co₂(CO)₆)₂(μ-η² ∶ η²,μ-η² ∶ η²-1,1′-bis(phenylethynyl)ferrocene)] 6. The [Mo–Co]-alkyne adducts [MoCo(CO)₅(η⁵-C₅H₅)(μ-η² ∶ η²-ethynylferrocene)] 7 and [MoCo(CO)₅(η⁵-C₅H₅)(μ-η² ∶ η²-1,4-bis(ferrocenyl)butadiyne)] 8 were obtained from complexes 1, 2 and 3. The molecular structures of compounds 2, 3, 6 and 7 were determined by X-ray diffraction, only 6 has the cyclopentadienyl rings of the ferrocene unit eclipsed. The reaction of 1 with bis(diphenylphosphino)methane (dppm) and 1,1′-bis(diphenylphosphino)ferrocene (dppf) resulted in the formation of [Co₂(CO)₄(μ-η¹ ∶ η¹-dppm)(μ-η² ∶ η²-ethynylferrocene)] 9 and [(Co₂(CO)₄)₂(μ-η¹ ∶ η¹-dppf)₂(η¹-μ-η¹-dppf)(μ-η² ∶ η²-ethynylferrocene)₂] 10, respectively. The reaction of HPPh₂ with 7 gave the monosubstituted product [MoCo(CO)₄(η⁵-C₅H₅)(PHPh₂)(μ-η²,η²-ethynylferrocene)] 11. The bis(phosphido)-bridged complex [Co₂(CO)₆(μ-PPh₂)₂] undergoes regiospecific insertion with ethynylferrocene to give [Co₂(CO)₄{(μ-η⁴-PPh₂CHCRC(O)}(μ-PPh₂)] (R = ferrocene) 12, which was characterized by X-Ray diffraction and contains a five-membered metallacyclic ring.