Phosphites transition metal complexes

Among transition metal complexes used as catalysts for reactions of the above-mentioned types b and c, the most versatile are nickel complexes. The characteristic reactions of butadiene catalyzed by nickel complexes are cyclizations. Formations of 1,5-cyclooctadiene (COD) (1) and 1,5,9-cyclododecatriene (CDT) (2) are typical reactions (2-9). In addition, other cyclic compounds (3-6) shown below are formed by nickel catalysts. Considerable selectivity to form one of these cyclic oligomers as a main product by modification of the catalytic species with different phosphine or phosphite as ligands has been observed (3, 4). 

Pobedimskii and coworkers [84-92] studied hydroperoxide decomposition under the combined action of a transition metal complex and phosphite. He found that this binary system induces three parallel catalytic reactions of hydroperoxide decomposition. 

Alkoxide anion abstraction by a Lewis acid from phosphorus ligand on a transition metal is one of the most useful methods to prepare cationic phosphenium complexes. It has been reported that OR anion abstraction from an alkoxyalkyl ligand, C(OR)R2, on a transition metal complex leads to the formation of a cationic carbene complex.39-42 It is similarly expected that OR anion abstraction from an alkoxysilyl ligand, Si(OR)R2, would cause the formation of a cationic silylene complex. Therefore, increased attention has been focused on the reaction with a Lewis acid of transition metal complexes bearing both alkoxyalkyl and phosphite ligands and of complexes bearing both alkoxysilyl and phosphite ligands. 

These Arbuzov-like reactions see Arbuzov Rearrangement) of phosphite ester transition metal complexes have been reviewed by Brill and Landon. ... 

Metal carbon insertions of C02 occur in both main group and transition metal complexes.5,19 The reactions result in a strong M—O bond at the expense of a weak M—C bond (together with a C C a bond at the expense of a C O n bond). Insertion into t/weo-W(CO)5 CHDCHDPh gave the threo carboxylate, indicating retention of configuration at the o-carbon, as with CO insertion.29 Cis- RW(CO)4L (R = Me, Et or Ph) showed second-order kinetics toward C02 insertion, first order in anion and in C02. Replacement of CO by a phosphine or phosphite increased the insertion rate.30 Palladium catalysis of C02 insertion into unreactive Sn C bonds in allyl stannanes provided three isomeric tetra-carboxylates from tetraallyl tin. Attempted reactions of tetraalkyl, vinyl or aryl tin complexes did not proceed. Insertion into an intermediate rf -allyl palladium complex was suggested to lead to carboxylate products.31,32... 

Dias, P. B. Minas da Piedade, M. E. Martinho Simoes, J. A. Bonding and Energetics of Phosphorus (III) Ligands in Transition Metal Complexes, Coord. Chem. Rev. 1994, 1351136, 737-807. Thermochemistry of transition metal-phosphorus bond. It also includes critically evaluated standard enthalpies of formation of phosphines and phosphites. 

Reactions of three-co-ordinate phosphorus(v) include hydrogen exchange in hypophosphites and condensation of phosphite with chromate. This latter is not a redox reaction, in contrast to such apparently similar systems as chromate plus thiosulphate, which is an 5/j-oxoanion analogue of the classical inner-sphere redox mechanism of transition-metal complex chemistry. Several associative mechanisms are feasible for reactions of phosphites with thionyl chloride. The phosphorus lone-pair can approach either the sulphur, the oxygen, or perhaps even one of the chlorines, which are rendered slightly positive by electron withdrawal to other sites in the thionyl chloride molecule. ... 

Dialkyl H-phosphonates exhibit a number of complexation modes with transition metals depending on their type. In complexes of dialkyl H-phosphonates with some early transition metals (Zr, H) in their higher oxidation states, the phosphonate ligands act as lone-pair a-donors and are coordinated to the metal center through the phosphoryl oxygen atom. In contrast to this, the late transition metals (Ni, Pd, Pt, Co, Ir, Rh, and Ru) exhibit a well-expressed preference to the more soft phosphorus donor of the phosphite tautomeric form. The late transition metal complexes of dialkyl H-phosphonates are additionally stabilized by the electron back donation from the electron-rich metal center to the empty and 3a orbitals at the phosphorus donor. 

TRANSITION METAL COMPLEXES OF CAGED PHOSPHITE ESTERS. 

Alternatively, the addition of homogeneous late-transition-metal complexes other than rhodium, such as Ru3(CO)j 2> Pt(acac)2, Pd(acac)2, Os3(CO)j 2> Co2(CO)g in combination with sterically hindered groups at the phosphite ligand, has been patented for the stabilization of hydroformylation catalysts [176]. 

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