(1–3-η-allyl)dicarbonylnitrosyliron complexes and their σ-, 1-σ,2–3-η-, and 1–3,η-allyl and but-3-enoyl derivatives with phosphine ligands

Abstract

The 1–3-η-allyl complexes [(η-C₃H₄X)Fe(CO)₂NO][I; X = H, 1-Me, -Cl, -CN, -Ph, or -(Cl, Me), and 2-Me, -Cl, or -Br] react with phosphine ligands [L = PBuⁿ₃, PPh₂Et, PPh₃, P(OMe)₃, P(OEt)₃, P{(OCH₂)₃CMe}, or P{(OCH₂)₃CEt}] to give five-co-ordinate complexes, [(σ-C₃H₄X)Fe(CO)₂(NO)L], (III), which then undergo chelation to [(σ,η-C₃H₄X)Fe(CO)(NO)L], (IV). When X = H, Me, or Ph, the intermediate complex (III) has not been detected, possibly due to the subsequent process of chelation being too fast. The symmetry of complexes (IV), between 1–3-η- and 1-σ,2–3-η-structures, depends on the substituent X and on the steric hindrance due to the entering ligand L. When L = P(OR)₃(R = Me or Et) and X = Cl or Br, a side process to that of chelation is operative which leads to but-3-enoyl complexes, (V), with insertion of CO between the metal atom and the σ-allyl group. With L = Ph₂PCH₂CH₂PPh₂and X = Cl, Br, or CN, insertion of CO is the predominant reaction.