Synthesis and coordination chemistry of a novel phosphinimine phosphine

Article abstract of DOI:10.1021/om00004a060

The incorporation of a phosphinimino moiety into phosphine ligands to form a new bidentate PH₃P=N(CH₂)₃PPh₂ (1) is reported. Compound 1 can act as a σ-N and σ-P donor ligand or react with metal carbonyls to form isocyanide complexes. Complexes of (CO)₄M-(1-P,N) [M = Mo (2), W (3)] were prepared from the reaction of Et₄N[M(CO)₅Br] with 1 in refluxing THF solution, whereas the isocyanide complexes of (CO)₅MCN(CH₂)₃PPh₂ [M = Cr (4), Mo (5), W (6)] are obtained from the reaction of M(CO)₆ with 1 at 25°C. The deoxygenation nature is also shown in the reaction of CpFe(CO)₂I, CpRu(CO)₂I, Re(CO)₅Br, and Re₂(CO)10 with 1 to form the corresponding isocyanide complexes [CpFe(CO){CN(CH₂)₃-PPh₂-C,P}]I (7), CpRu(CO)I{CN(CH₂)₃PPh₂-C} (10), BrRe(CO)_5-n{CN(CH₂)₃PPh₂-C} _n [n = 1 (12), 2 (14)], and Re₂(CO)₉{CN(CH₂)₃PPh₂-C} (15), respectively. The free phosphine of 10 underwent exchange with one triphenylphosphine ligand in CpRu(PPh₃)₂Cl to yield the binuclear species [CpRu(PPh₃)Cl{P(Ph₂)(CH₂) ₃NC}Ru(CO)CpI] (11), whereas intramolecular ligand substitution occurred in both 12 and 15 to give Br(CO)₃Re{CN(CH₂)₃PPh₂-C,P} (13) and {μ-CN(CH₂)₃PPh₂}Re₂(CO) ₈ (16). Reaction of (COD)PdCl₂ with 1 produced the complex (1-P,N)PdCl₂ (18), in which 1 acts as a σ-N, σ-P bidentate ligand. X-ray crystal structural analysis of [CpFe(CO){CN(CH₂)₃PPh₂-C,P}]PF₆ (7a) and 18 confirmed the formulation of both complexes. The C≡N bond distance [1.20(3) A?] of 7a is greater than those in the related iron-isocyanide complexes; the angle C-N-C [141(2)°] deviates from 180°, indicating that the resonance contribution of Fe=C=N- is more important than that of Fe-C≡N-. These observations are consistent with spectral data, the smaller infrared stretching wavenumber (2089 cm^-1), and the greater shift (¹³C NMR δ 183.7 ppm) of the isocyanide moiety of 7.