Tricyclohexylphosphine complexes

The structures of the complexes [PdL ] (L = P(C6Hn)3, PBu Ph) have been confirmed by X-ray studies on single crystals.33,34 Although these compounds both exhibit C2 symmetry, the tricyclohexylphosphine complex is bent (P—Pd—P=158°), whereas the di-r-... 

Tris (triphenylphosphine) nickel, tris (tri-p-tolylphosphine) nickel, and bis (1,3-diphenylphosphinepropane) nickel proved to be good catalysts, the first being slightly more effective. The tricyclohexylphosphine complex was a very poor catalyst, and bis (cyclooctadiene) nickel did not catalyze cyanation. Cyanation of several substituted aromatic halides in the presence of Ni[P(C6H5)3]3 prepared by reducing dichlorobis (triphenylphosphine) nickel (II) 2 with a powdered manganese iron (80 20) alloy (Reaction 3) is reported in Table II. 

Tricyclohexylphosphine Complexes of Ruthenium, Rhodium, and Iridium and Their Reactivity Toward Gas Molecules... 

Pyrones are prepared by insertion at the C=0 bond of CO2. The pyrone 188 is prepared by the Ni-catalysed reaction of 1,6-diyne 185 with CO2 [77], However, this reaction is explained by the carbonickelation of one of the triple bonds with CO2 to form 186, followed by insertion of another triple bond to give the seven-membered intermediate 187, rather than insertion of CO2 to nickelacyclopentadiene. In this reaction the Ni(0)-tricyclohexylphosphine complex is an active catalyst. 

The bis(tricyclohexylphosphine) complexes are 14-electron species and are highly reactive. They are easily oxidized by air,48 and even decompose when stored in an inert atmosphere. However, they will readily coordinate an additional small ligand. Many of these small ligands bind through carbon and are, therefore, outside the scope of this review. Both dinitrogen48,49 and sulfur dioxide form adducts (equations 9 and 10).so... 

The five-coordinate monohydrido complexes shown in Table 63 are less reactive and less important catalytically than their dihydrido analogs. One of the few reactions noted is the addition of pyridine to the tricyclohexylphosphine complexes to form six-coordinate products (equation 188).924 Six-coordinate complexes can also be obtained if the preparation of [RhH2Cl(PPh3)2] is carried out in coordinating solvents.10... 

Ishiyama, T., Ishida, K., Miyaura, N. Synthesis of pinacol arylboronates via cross-coupling reaction of bis(pinacolato)diboron with chloroarenes catalyzed by palladium(0)-tricyclohexylphosphine complexes. Tetrahedron 2001, 57, 9813-9816. 

Aresta and coworkers have provided a very interesting example of C-N and N-H bond activation by use of low-valent nickel tricyclohexylphosphine complexes [86], Alkyl-ammonium or -imminium tetraphenylborate salts readily undergo oxidative addition to (Cy3P)2Ni(Tl -CO2) or (Cy3P)2Ni(p-N2)Ni(PCy3)j at or below room temperature, to yield the corresponding Ni(II) derivatives shown in Fig. 6.8. 

Scheme 2. The synthesis of tricyclohexylphosphine complexes of Ir(III) that contain hydridic-protonic bonds involving the p3aidinethione ligand.

A similar procedure for the two-step synthesis of the first-generation ruthenium indenylidene catalysts has been patented by Umicore (Scheme 14.11) [38]. The main differences from the previously reported route lie in the utilization of diox-ane as the reaction solvent at 90 C in the first step, followed by the addition of HCl for the acid-promoted formation ofthe indenylidene ligand via the alkenyl carbyne [19]. The preparation of the tricyclohexylphosphine complex was carried out in one pot without isolating the intermediate triphenylphosphine complex 5 [38]. 

The most widely employed heteroatom ligands are the phosphines. Although they are largely spectators and do not participate directly in bond formation (and when they do, the result is often highly undesirable), they are not innocent bystanders. The size and electronic nature of the three groups attached to phosphorus have a profound effect on the course of the reaction and may make the difference between success and failure. An example is with the Grubbs catalyst (Chapter 8). The bis(triphenylphosphine) complex is of little use. The bis(tricyclohexylphosphine) complex is Nobel-prize winning. 

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