Phosphines, reactions

Examples of the intermolecular C-P bond formation by means of radical phosphonation and phosphination have been achieved by reaction of aryl halides with trialkyl phosphites and chlorodiphenylphosphine, respectively, in the presence of (TMSlsSiH under standard radical conditions. The phosphonation reaction (Reaction 71) worked well either under UV irradiation at room temperature or in refluxing toluene. The radical phosphina-tion (Reaction 72) required pyridine in boiling benzene for 20 h. Phosphinated products were handled as phosphine sulfides. Scheme 15 shows the reaction mechanism for the phosphination procedure that involves in situ formation of tetraphenylbiphosphine. This approach has also been extended to the phosphination of alkyl halides and sequential radical cyclization/phosphination reaction. ... 

The reactions 2 and 3 in Table 5 set the limits for the proton affinity of phosphine. Reaction 2 shows that it is smaller than that of acetone (186 3 kcal/mol) and reaction 3 indicates that it is larger than the proton affinity of acetaldehyde (185 3 kcal/mol). Thus a value of 185 ... 

Thioacetalized formylphosphonium salts, which are excellent precursors for tetra-thiafulvalene and analogous derivatives, are obtained in high yields directly from tertiary phosphines (reaction 71). 

For a-halo ketones, bisphosphonium salt formation can also take place by vinylation or arylation of the phosphine (reaction 90). Bisphosphonium salts can also be obtained, in moderate yield, by the introduction of two phosphines on the same aromatic or heterocyclic ring, at high temperature358 (reaction 91). For pyridine, activation by triflic anhydride allows successive additions of two phosphonio groups in the 2,4-positions247 (reaction 92). 

Complexes in the 0 oxidation state may be obtained either by reduction of halides such as RuCl2(PPh3)3 with Na or Zn in the presence of CO or other ligands such as RNC, or by reaction of metal carbonyls with phosphines. Reactions of polynuclear carbonyls such as Ru3(CO)12 (Section 18-F-13) with phosphines tend to preserve the cluster structure. 

Bisulfite, phosphite,and phosphine " reactions in MeCN/H20 (1 1), DMF and MeCN respectively. Measured at 298 K. in kcalmoCL inen. from... 

In the case of L = CO, CO insertion into the Zr-R bond competes with reduction however, for R = C-C6H11CH2, the reduction just shown [reaction (h)] is the predominant reaction . If L is a tertiary phosphine, reaction (h) does not work well if L is too bulky. Further, pure a donors such as THF and NEts will not effect reduction presumably, L must be able to stabilize the Zr(II) oxidation state . Pyridine-induced reductive elimination has also been utilized as a route to the preparation of aryloxide Ti(II) and Ti(III) complexes from Ti(IV) precursors . 

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