Ligand substitution processes on carbonylmetal derivatives. 2. Reaction of tetracarbonylhydridoferrates with phosphites

Article abstract of DOI:10.1021/om00045a015

Ligand substitution processes on KHFe(CO)₄ (1) have been evidenced by reaction with various phosphites. The nature of the reaction products strongly depends on (i) the nature of the solvent, (ii) the Tolman cone angle of the phosphite, and (iii) the reaction conditions. In protic media (H₂O-THF), phosphites with small cone angles, such as P(OMe)₃, P(OEt)₃, and P(OPh)₃, react (2 equiv) with 1 at room temperature to give the corresponding complexes H₂Fe(CO)₂[P(OR)₃]₂ in >90% yield, whereas a phosphite with a larger cone angle (P[O-o-C₆H₄Ph]₃) reacts only at a higher temperature to afford the disubstituted Fe(CO)₃[P{O-o-C₆H₄Ph}₃]₂ derivative in 94% yield. When the reaction with phosphites having small cone angles is conducted with a 3-fold excess of phosphite at 65°C, the trisubtituted derivatives Fe(CO)₂[P(OR)₃]₃ are formed in 75-96% yield. In aprotic medium (THF), 1 reacts with phosphites (2 equiv) at room temperature to yield the monosubstituted anionic hydrides K⁺[HFe(CO)₃{P(OR)₃}]^-, which can be isolated in >90% yield. In refluxing THF the reaction of 1 with P(OMe)₃ (3 equiv) demonstrates the first synthesis of the hydridoferrate K⁺[HFe(CO)₂{P(OMe)₃}₂]^-. Protonation of K⁺[HFe(CO)₃{P(OR)₃}]^- with trifluoroacetic acid in THF at -10°C provides an excellent route for the high-yield synthesis of the monosubstituted dihydrides H₂Fe(CO)₃[P(OR)₃]. In situ reaction of the latter with another phosphane PZ₃ (Z = Ph, OPh) leads to the mixed dihydrides H₂Fe(CO)₂[P(OR)₃][PZ₃] (R = Me, Et; Z = Ph, OPh), which are reported for the first time. Finally, reaction of H₂Fe(CO)₂[P(OEt)₃]₂ with KH under sonication allows the generation of the highly reduced derivative K₂[Fe(CO)₂{P(OEt)₃}₂], the first disubstituted analogue of the Collman reagent.