Palladium Coordination Compounds of σ3λ5-Phosphoranes: First Examples of Phosphonio−Methylene(imino)metallophosphorane [(R3P)(Me3Si)CP(MLn)NSiMe3] and Phosphonio−Methylene(oxo)phosphorane [(R3P)(Me3Si)CP(O)NSiMe3] Ligands
摘要:
The oxidative addition reaction of Pd(PPh3)(4) with Cl2C=PN(SiMe3)(2) forms the phosphavinyl phosphonium complex Cl(Ph3P)Pd[eta(2)-C(Cl)(PPh3)=PN(SiMe3)(2)] (IIIa), which results from PPh3 migration from Pd to carbon in the eta(1)-phosphavinyl intermediate trans-Cl(Ph3P)(2)Pd-[C(Cl)=PN(SiMe3)(2)] (IIa). The reaction of Pd(dba)(dppe) with Cl2C=PN(SiMe3)(2) forms the eta(1)-phosphavinyl complex cis-Cl(dppe)Pd[C(Cl)=PN(SiMe3)(2)] (VI), which does not undergo phosphine migration. Compound IIIa undergoes substitution of the chloride ligand by PPh3 or MeCN in the presence of KPF6 to generate [(Ph3P)(2)Pd(eta(2)-C(Cl)(PPh3)=PN(SiMe3)(2))] (PF6) (IV) or [(Ph3P)(MeCN)Pd(eta(2)-C(Cl)(PPh3)=PN(SiMe3)(2))](PF6) (V), respectively; the structure of V was determined by X-ray diffraction studies. The reaction of Pd(PEt3)(4) with Cl2C= PN(SiMe3)(2) forms the eta(1)-phosphavinyl complex trans-Cl(Et3P)(2)Pd[C(Cl)=PN(SiMe3)(2)] (IIb), which does not undergo PEt3 migration. When 2 equiv of Pd(PEt3)(4) are reacted with Cl2C= PN(SiMe3)(2) the phosphonio-methylene(imino)metallophosphorane complex Pd(PEt3)(Cl)[mu-eta(1):eta(2)-C(SiMe3)(PEt3)=P=N(SiMe3)]Pd(PEt3)Cl (VIIa-b) forms as a 1:1 isomeric mixture. Compound VIIa-b reacts with MeI or NaI to generate Pd(PEt3)(I)[mu-eta(1):eta(2)-C(SiMe3)(PEt3)= P=N(SiMe3)]Pd(PEt3)I (VIIIa-b) and reacts with traces of water to generate Cl(Et3P)Pd-[eta(2)-C(SiMe3)(PEt3)=P(=O)NH(SiMe3)] (IX). The structure of VIIIb was partially determined, and the structure of IX was determined by X-ray diffraction studies. Compounds VIIa-b, VIIIa-b, and IX exhibit the first examples of coordinated methylene(imino, oxo)phosphorane ligands.