Phosphine hgands

Figure 15 shows the phosphine hgands in frans-Co2(CO)6(phosphine)2 investigated with the static solubihty measurement setup. They were synthesized or are commercially available. 

Maddaford reported the diastereoselective synthesis of C-glycosides 29 using conjugate addition catalyzed by cationic rhodium catalysts such as [Rh(COD)2]BF4 (Eq. 1) [24]. Addition of phosphine hgands to the reaction system inhibited the conjugate addition. It is likely that the enone 28 derived from the pyranose is less reactive toward the conjugate addition. 

Cationic phosphine Hgands containing guanidiniumphenyl moieties were originally developed in order to make use of their pronounced solubility in water [72, 73]. 

The bis-phosphine complex must live long enough to capture a further phosphine Hgand or else nickel metal precipitates.) It is predicted that other metals should be effective in such physical mixtures, in which case the idea has greater potential. 

Figure 5.6 Some examples of sulfonated phosphine hgands widely used in aqueous-organic biphasic catalysis [19]...

Figure 8.4 The structure of the chiral bis-phosphine hgands RDuPHOS...

In this double catalytic cycle the olefin is first transformed into aldehyde and then into alcohol. Owing to the increased sieric crowding of the bulky tertiary phosphine Hgand, all the stcric factors discussed in the previous section, which favour the production of normal aldehydes, are much favoured here. 

The measure of basicity of phosphine hgands most widely quoted in the hterature is p/fa (aqueous), which is a measure of Bronsted basicity or proton affinity. A selection of pA a values for various phosphines is given in Table 4. AngeUci and coworkers have established a method for determining proton affinities from enthalpies of protonation using the extremely powerful acid CF3SO3H. The enthalpy values (A//hp) and pATa values are related by the empirical equation (3) ... 

Associative attack by two-electron donors can occur under mild conditions if the addition is accompanied by metal-metal bond cleavage. An example is addition of phosphine hgands at 5°C to CoFeW(/u,3-PMe)(CO)gCp, which forms CoFeW(/u.3-PMe)(CO)g(PR3)2 via cleavage of the Fe-Co and W o bonds. 

Scheme 14 Influence of phosphine hgand in the synthesis of stericaUy hindered NHC-Pd complexes...

The coordination chemistry of phosphinoenolato complexes has been reviewed. In certain cases the phosphinoenolate complex acts as a plain phosphine hgand for example. 

Fig. 2.4 Hydrogenase model by Schwartz (2009). As compared to the natural cyanide, tiimethyl phosphine hgands in the model complex will increase redox potentials of the Fe(ll) centers while reducing M-H acidity of hydride (cp. Franzle 1992). This diminishes...

The results of fhe phosphine dissociation experiments for the various ruthenium complexes were surprising in fhat fhe second-generation catalysts exchange phosphine hgands slower fhan the first-generation analogs (Tab. 6.2). 

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