Phosphine tertiary derivatives, complexes

The derivatives of cyclic boryloxyalkyl phosphines readily undergo complexation with tertiary amines and especially pyridine with the participation of the boron atom [Eq. (113)] (83IZV2545 86IZV643). 

A second important class of complexes contains both thiolate and tertiary phosphine ligands. These are prepared by reactions such as those of equations (28) or (29).187,228,233-236 Bridged complexes (9) and (10) may be prepared either from dithiols or from tertiary phosphine thiol derivatives, respectively.187,237 The structure of the large ring complex (10) has been determined.238... 

The reaction of tertiary phosphines with aikyne complexes to give a-me-tallated vinylphosphonium derivatives has been taken to indicate the intermediacy of vinylidene complexes (48) ... 

From the up-to-date literature and patent review of catalysts used In anhydride and phenolic cured epoxy molding compounds, It Is evident that Imidazoles and their derivatives predominate (Table I). Metal complex, trialkyl or triaryl phosphines and their complexes, Lewis acids such as zinc or stannous octoate are used to a much lesser extent (Table II). There are a few examples of tertiary amines and urea derivatives used. 

Primary and secondary phosphines can oxidatively add to low-valent transition metal complexes to form phosphido complexes. In contrast to phosphines, metal phosphido complexes are known to undergo fast pyramidal inversion, often on the NMR timescale. Inversion barriers for some platinum complexes, determined by NMR spectroscopy, range from 42 to 67kJmol. As a consequence, phosphido complexes containing other chiral ligands are mixtures of interconverting diastereomers. Reaction of these complexes with electrophiles yields tertiary phosphines and derivatives (Scheme 6.1). 

The a-keto amides are less susceptible to hydrolysis and preparation of a-keto esters and acids are preferable for synthesizing various derivatives thereof. Various aryl iodides and bromides can be converted into a-keto esters on reactions with alcohols and carbon monoxide in the presence of a base such as tertiary amines or potassium acetate with catalytic amounts of tertiary phosphine-coordinated palladium complexes (Eq. 11).[42]-[46] jjjgjj yields of a-keto esters can be achieved only when iodide substrates are used. Double carbonylation of aryl bromides to a-keto esters can be accomplished with difficulty at much slower rates. Alkyl and benzyl iodides give no double carbonylation products. 

The coordination chemistry of tertiary phosphine-functionalized calix[4]arenes have been described.279 Treatment of a bis(diphenylphosphino) or bis(dimethylphosphino) derivative of calix[4]arene with [PtCl2(COD)] leads to the formation of the corresponding dichloroplatinum(II) complex. The related diplatinum(II) species has also been reported with the tetrafunctionalized calix[4]arene.280 The mononuclear derivative is susceptible to oligomerization if the two free phosphine ligands are not oxidized or complexed to another metal center such as gold(I).279 The platinum(II) coordination chemistry of a mono-281 and diphosphite282 derived calix[ ]arene (n = 4 and 6, respectively) has also been described. 

Dimeric zinc complexes of tertiary phosphines, [Zn(PR3)I2]2, are also formed from zinc powder and R3PI2, (R = Me, Et, n-Pr, ra-Bu). The crystal structure of the ethyl derivative demonstrates the dimeric nature of the complexes.295 Metallation of diphenylphosphine with ZnEt2 results in a trimeric species with a Zn3P3 core and bridging diphenyl phosphide ligands. Two protic (HPPh2)... 

The current interest in cluster complexes as possible catalysts has made desirable a method of synthesis of selectively substituted derivatives, which does not suffer the disadvantages just outlined. Cluster-bound molecules have high and often unique reactivity, and the introduction of tertiary phosphines containing functional groups is often difficult. 

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