Triphenylphosphine, phosphorus-palladium

Nucleophilic attack. Current literature underestimates the importance of nucleophilic attack as a mechanism for the catalytic decomposition of phosphines, especially with nucleophiles such as acetate, methoxy, hydroxy and hydride. For examples of nucleophihc attack at coordinated phosphorus see references [20-25]. A very facile decomposition of alkylphosphines and triphenylphosphine (using palladium acetate, one bar of hydrogen and room temperature) has been reported [20] using acetate or hydride as the nucleophile. 

Tertiary phosphine groups with long alkyl chains bound directly to phosphorus or substituted at the para position of triphenylphosphine give rise to a range of interesting and potentially useful complexes. In particular these may be used to prepare polyolefin hydrogenation catalysts based on platinum(II) and palladium(II) complexes that are both more active and more selective towards reduction to monoolefins than previous catalysts based on these systems. The platinum(II) complexes are better than the palladium(II) complexes. Additionally the new phosphines are more effective than triphenylphosphine in promoting the oxidative addition of methyl iodide to trans- [Rh(PR3)2Cl(CO)]. 

In the first example, nitration of the benzoate (140) with nitric acid affords the nitro derivative. Hydrogenation converts this to the anthranilate (141). In one of the standard conditions for forming quinazolones, that intermediate is then treated with ammonium formate to yield the heterocycle (142). Reaction of 142 with phosphorus oxychloride leads to the corresponding enol chloride (143). Condensation of 143 with m-iodoaniline (144) leads to displacement of chlorine and consequent formation of the aminoquinazoline (145). Reaction with the trimethylsilyl derivative of acetylene in the presence of tetrakis-triphenylphosphine palladium leads to replacement of iodine by the acetylide. Tributylammonium fluoride then removes the silyl protecting group to afford the kinase inhibitor erlotinib (146). ... 

The structures of acetylene 7r-complexes (eq. (20.8)) are shown in Figure 20.2 [150]. Two carbons of the acetylene, two phosphorus atoms, and one palladium are approximately planar. It looks like three coordination structure. Each substituent upon acetylene is bent away from the methyl by about 35° from the C=C bond axis by the effect of bulk triphenylphosphine group. 

An active and selective catalyst proved to be ( / -methallyl) (77 -cycloocta-l,5-diene)palladium tetrafluoroborate activated by a phosphorus ligand. It can be seen from Table V that the nature of the phosphorus ligand and the P Pd ratio strongly affect catalytic activity and product selectivity. The best results are observed for tributylphosphine and a P Pd ratio of 0.5 1 to 1 1. Noteworthy is the inhibition of the reaction for P Pd ratio of 2 or more. The main dimer obtained is dimethyl raAW-hex-2-enedioate when tributylphosphine was used. In this instance, practically no change in selectivity is observed by varying the P Pd ratio. Lower selectivities are observed for less basic phosphorus ligands such as triphenylphosphine or -phosphite. 

Isoprene is treated with diethyl phosphonate in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium and l,2-bis(diphenylphosphino) ethane (DIPHOS) to give diethyl 3-methyl-2-butenylphosphonate (24) selectively (Scheme 2.14) [24], This protocol is used in various carbon-phosphorus bond forming reactions [38 2],... 

The Suzuki catalyst has the rather forbidding name tetrakis(triphenylphosphine)paUadi-um(0). This looks a bit less complex when we write its condensed formula Pd[P(C6H5)3l4. Since Ph is a common abbreviation for the phenyl group, C Hg, we can condense the formula even more as Pd(PPh3)4. The palladium atom sits at the center of a tetrahedron and has an oxidation number of zero (Figure 17.4). The phosphorus atom of the triphenylphosphine donates an electron pair to a vacant 4d orbital of Pd(0) without altering its oxidation state. 

Related Reagents. Aluminum Chloride Diphenylsilane-Tetrakis(triphenylphosphine)palladium(0)-Zinc Chloride Phos-phorus(in) Chloride-Zinc(II) Chloride Phosphorus Oxychlo-ride-Zinc(II) Chloride Tin(rV) Chloride Tin(IV) Chloride-Zinc Chloride Titanium(IV) Chloride Zinc Bromide. 

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