O-H Activation and Addition to Unsaturated Systems

Transition Metal Complexes Resulting from the Activation of O-H Bonds and Reaction with Related Complexes 

Oxidative addition of the O-H bond to transition metal complexes gives hydrido(hy-droxo), hydrido(alkoxo) or hydrido(carboxylato) complexes (Eq. 6.1), but web-characterized complexes obtained as primary products from the reaction of the compound, XO-H (XO-H = water, alcohol, and carboxylic acid) with late transition metals are quite rare [1]. Furthermore, the crystal stractures of very few complexes of this type have been reported. In this section we will survey late transition metal complexes resulting from activation of water, alcohol, and carboxylic acid. 

Preparation of Hydrido(hydroxo), Hydrido(alkoxo), and Hydrido(carboxylato) Complexes by Metathesis 

Before discussing the preparation of late transition metal complexes resulting from the activation of O-H bonds by late transition metal complexes, we wbl describe metathesis methods for the preparation of hydrido(hydroxo), hydrido(alkoxo), and hydrido(carboxylato) complexes. Though many methods of preparation of transition metal hydroxides, alkoxides, etc. by a metathesis reaction have been reported [1], only a limited number of examples of the preparation of hydrido(hydroxo), hydri-do(alkoxo) complexes etc. by metathesis are available. 

The hydrido(ethoxo) complex carrying an electron-donating q -CsMes (= Cp ) ligand, [Cp IrH(OEt)(PPh3)] (4), was prepared by a metathesis reaction between [Cp Ir Cl2(PR3)] (3) and NaOEt followed by P-H elimination from the intermediate diethox-ide complex (Eq. 6.4) [7]. Several other iridium alkoxide analogs [Cp IrH(OR) 

Severalhydrido(phenoxo) complexes ofnickel, trans-[NiH(OPh)L2] (6) (su L= P Prs b L = PCyj c L = PBns), have been prepared by the metathesis reaction of NaOPh with trans-[NiHClL2] (Eq. 6.6). The complex 6c was obtained as the phenol-solvated complex whose structure was determined by X-ray analysis [9]. An analogous platinum complex traws-[PtH(OPh)(PEt3)2] (7) was prepared by the reaction of trans-[PtH(N03)(PEt3)2] with NaOPh (Eq. 6.7). The complex 7 is air-stable but thermally sensitive and decomposes at room temperature. The structure was elucidated by X-ray analysis [10]. 

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