Preparation and Reactivity of Organometallic Complexes with Phosphorus Compounds as Covalent Ligands

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1. Preparation and Reactivity of Transition-metal Complexes Having a Multiple Bond to the PhosphorusTreatment of Cr, Mo, and W complexes of various amino-substituted phosphites with BX_3 led to the formation of the cationic complexes with an M=P double bond, which are stabilized with increase in the amino-substitution and in chelation of the phosphite ligands and with the atomic number of the central metals.2. Preparation of Transition-metal Phosphonate Complexes and the MechanismThe Arbuzov-like dealkylation reaction of [Cp(CO)_2FeCl] with amino-substituted phosphites gave a cationic complex [Cp(CO)_2Fe[P(NR_2)Y(OR)]^+ (Y=OR,NR_2), which is regarded as an intermediate. The reaction of it with Cl^- yielded usual dealkylation products[Cp(CO)_2Fe[P(O)(NR_2)Y]], While the treatment with OR^- afforded a phosphonate complex [Cp(CO)_2Fe[P(0)Y(OR)]] where the NR_2 group is selectively eliminated. A plausible reaction mechanism is proposed in which a pentacoordinate metallaphosphorane is once formed with the NR_2 and incoming OR groups in axial positions, and then the OR group is attacked by another OR^- to release to release the NR_2^- group and the ether R_2O.3. Migration of the Phosphonate Ligand from the Central to the Cp RingThe phosphonate ligand P(0)RR' is found to migrate quantitatively to the Cp ring in [Cp(CO)LFe[P(O)RR']] when the complex is treated with LDA. The reaction mechanism was examined by use of some chiral phosphonate complexes.4. Photo-chemical Reaction of Transition-metal Phosphonate ComplexesWhen the [Cp(CO)_2Fe[P(O)(OR)_2]] is irradiated with UV in the presence of L (L=PPh_3 or P(OR)_3), [Cp(CO)LFe[P(O)(OR)_2]] is formed with one CO group replaced by L, whereas a dimeric complex is formed in the absence of L, in which the P=0 group is coordinated in place of CO. The reaction was proved useful for synthetic purposes.