Metal-assisted cleavage of a C-O bond of a P-bound bifunctional phosphine ligand

Article abstract of DOI:10.1021/om00019a025

Treatment of [IrCl(C₂H₄)₂]₂ (1) with the phosphino ester iPr₂PCH₂CO₂Me affords the mononuclear complex trans-[IrCl(C₂H₄)(iPr₂PCH₂CO ₂Me-κP)₂] (2), which reacts with CO to give trans-[IrCl(CO)(iPr₂PCH₂CO₂Me-κP) ₂] (3) and with HC≡CR to give [IrH(C≡CR)Cl-(iPr₂PCH₂CO ₂Me-κP)(iPr₂PCH₂CO ₂Me-κ²P,O)] (R = Ph (4), CO₂Me (5)). Upon heating, the alkynylhydridoiridium compounds 4 and 5 rearrange to yield the isomeric vinylidenemetal derivatives trans-[IrCl(=C=CHR) (iPr₂PCH₂CO₂Me-κP)₂] (R = Ph (6), CO₂Me (7)). Reaction of 3,6, and 7 with Al₂O₃/H₂O leads to cleavage of a CH₃-O bond of one phosphino ester ligand and gives the chelate complexes [Ir(L)(iPr₂PCH₂CO₂Me-κP)(iPr ₂PCH₂CO₂-κ²P,O)] (L = CO (8), C=CHPh (9), C=CHCO₂Me (10)) in 80-90% yield. Compound 8 reacts with methyl iodide by oxidative addition to form the octahedral complex [IrI(CH₃)(CO)(iPr₂PCH₂CO ₂Me-κP)-(iPr₂PCH₂CO ₂-κ²P,O)] (11). The X-ray crystal structure of 8 has been determined (triclinic, space group P1 (No. 2), with a = 9.124(5) A?, b = 11.301(7) A?, c = 12.126(6) A?, α = 79.34(4)°, β = 78.92(4)°, γ = 71.56(5)°, and Z = 2).