Bis- phosphite

Phosphite complexes of platinum(0) have received substantially less attention than have phosphine complexes.44 [Pt P(OC6H4OMe-2)3 3] can be prepared by reduction of the [PtCl2 P-(OC6H4OMe-2)3 2] complex in the presence of the phosphite or by the reaction of the phosphite with Lris(//2-norbornene)platinum(II) 44 Alkene complexes of bis(phosphite)platinum(II) can be prepared in a similar manner to the analogous phosphine complexes. 

It has been suggested that bis(equatorial) (ee) coordination of bidentate P-donor ligands in [HRh(CO)2(diphosphine)] (structure 5) can favor high linear/branched product ratios relative to systems which prefer equatorial-axial (ea) chelation (structure 6). For the bulky bis-phosphite 7 shown in Scheme 3.4, HP IR in conjunction... 

Industrial efforts have been focused on manufacturing of t>r/ 7/-aldehydes ( linear aldehydes) from olefins. Here, we briefly summarize its history on the development of phosphorus ligands, which are classified as monophosphine, monophosphite, bis-phosphite, and bis-phosphine, all useful for the normal-sc cct vc hydroformylation. 

Figure 2 Union Carbide bis-phosphite ligands for normaZ-selective hydroformylation.

Under these circumstances, the third-generation catalysts, Rh(i)-chiral bis-phosphites and Rh(i)-chiral phosphine-phosphites, were developed in 1992-1993. Apart from the asymmetric matter, it was reported in the 1980s that rhodium(i) complexes of phosphites, especially those bearing bulky substituents, showed high activities in... 

Figure 6 Union Carbide chiral bis-phosphite-rhodium complexes used as catalysts for the asymmetric hydroformylation.

A number of papers on asymmetric hydroformylation of olefins using chiral bis-phosphite or bis-phosphine ligand were reported by 2000. Here, we focus on some examples that achieved high enantioselectivities. 

Although bis(phosphite) carbyne complex Cp[P(OMe),]2Mo=C(c-Pr) is incapable of undergoing carbonyl insertion reactions, it adds 1 equivalent of HCl in ether forming the ring-opened -butadiene complex Cp[P(OMe),l(Cl)Mo( 4-butadiene) in 15% yield, and P(OMe)j in equal amounts (equation 108)158. Careful analysis of the reaction using... 

One of the drawbacks of the use of bisphosphines is the elaborate syntheses necessary for their preparation. Many efforts have been directed towards the development of bis-phosphonites and bis-phosphites. However, surprisingly mono-dentate phosphinates, phosphates and phosphoramidates recently emerged as effective alternatives for bidentate phosphines (Fig. 3.29). This constitutes an important breakthrough in this area as these can be synthesized in one or two steps, and the cost of these ligands is an order of magnitude lower Monophos can be made in a single step from BINOL and HMPT. 

Although bis(phosphite) carbyne complex Cp[P(OMe)3]2Mo=C(c-Pr) is incapable of undergoing carbonyl insertion reactions, it adds 1 equivalent of HCl in ether forming the ring-opened f/ -butadiene complex Cp[P(OMe)3](Cl)Mo( / -butadiene) in 15% yield, and P(OMe)3 in equal amounts (equation 108) . Careful analysis of the reaction using two equivalents of HCl reveals the presence of the metal hydride complex Cp[P(OMe)3]2Cl2MoH as the main products (70%), and free butadiene. It was furthermore shown that the two molybdenum complexes are not interconvertible under the reaction conditions and both the yields and products ratio are invariant with temperature in the range of -40 °C to room temperature and the amount of added HCl (1 or 2 equivalents). 

In the presence of higher concentrations of phosphines, di- and trisub-stituted products may be obtained (727), and interesting examples of the stereospecific formation of isomers by electron-transfer catalysis have been reported (123,124). The flyover complex [Co2(CO)4 /u,-C6(CF3)6 ] (53) forms the bis(phosphite) derivative [Co2(CO)2 P(OMe)3 2(/u-C6(CF3)6 ] when reduced in the presence of excess P(OMe)3, but two different isomers can be exclusively produced depending on the applied electrolysis potential. At the potential of the one-electron reduction of 53 (E = -0.1 V vs Ag/AgCl), isomer 54 is formed, but, at a potential appropriate for the reduction of 54 ( = —0.7 V), quantitative conversion to isomer 55 is achieved. The reaction is electrocatalytic in both cases. 

Finally, carbohydrate ligands of enantioselective catalysts have been described for a limited number of reactions. Bis-phosphites of carbohydrates have been reported as ligands of efficient catalysts in enantioselective hydrogenations [182] and hydrocyanations [183], and a bifunctional dihydroglucal-based catalyst was recently found to effect asymmetric cyanosilylations of ketones [184]. Carbohydrate-derived titanocenes have been used in the enantioselective catalysis of reactions of diethyl zinc with carbonyl compounds [113]. Oxazolinones of amino sugars have been shown to be efficient catalysts in enantioselective palladium(0)-catalyzed allylation reactions of C-nucleophiles [185]. 

The chelating bis(phosphite) (176) was synthesized by condensation of PCI3 with HOCMe2-CMe2OH in diethyl ether in the presence of N,A-dimethylaniline.402 Sterically congested bis(pho-sphites) have also been described.403... 

An improved preparation of (61) and of the new (62) has been published.Some new dialkyl trichloromethylphosphonites (63) have been prepared by a simplified method.The new, chelating bis-phosphite (64) has been prepared as shown.Some (methylthiomethyl)phosphonous acid derivatives (65)-(67) have been synthesized from phosphorus trichloride and the (methylthio-methyl)stannane (68). A series of unsymmetrically substituted (thiophosphonomethyl)phosphonous acid derivatives (69) and (70) has been prepared as shown for use as ligands. 

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