Diphosphane derivatives

Bromomagncsium 4-methylbenzenetellurolate and t-butyldichlorophosphane reacted in diethyl ether to give t-hutylphosphanidene his[4-methylphenyl tellurium] and l,2-bis[4 -methylphenyltelluro)-l,2-di(t-butyl)diphosphane. Only the diphosphane derivative was obtained in pure form. The t-butylphosphanidene bis[4-methylphenyl tellurium] was detected in solution by 3 P-NMR spectroscopy3. 

A new type of diphosphane derivative (5) has been obtained recently during the reduction of the borane adduct (MeO)3P,BH3 with sodium naphthalide in 1,2-dimethoxyethane/ ° The product isolated as the sodium salt is thermally and hydrolytically stable, and, although the n.m.r. data are not wholly definitive, the trigonal-bipyramidal structure with an axial P—P bond (5) has been suggested. 

Complexes with a derivative of oxazolylphosphane (Figure 4.34, left) [91], or a diphosphane derived from 2,2 diphenylmethane (Figure 4.34, right) [92], have boat structures in the solid state, and show no boat inversion at room temperature. 

Nitrogen, phosphorus and arsenic form more than one hydride. Nitrogen forms several but of these only ammonia, NHj, hydrazine, N2H4 and hydrogen azide N3H (and the ammonia derivative hydroxylamine) will be considered. Phosphorus and arsenic form the hydrides diphosphane P2H4 and diarsane AS2H4 respectively, but both of these hydrides are very unstable. 

With diphosphanes recently Stephan et al. reported an intriguing Al and P based macrocyclic structure [37]. A zirconium based catalyst precursor first was employed in the catalytic dehydrocoupling of the primary bidentate phosphane to give the tetraphosphane 6, (Scheme 4). The function of 6 as a molecular building block has been demonstrated by its reaction with MMe3(M = Al, Ga). Although, the gallium derivative 7 has not been... 

These phosphinous amide anions are presumably responsible for the formation of the by-products AT-phosphino phosphinous amides 11 and mono-phosphazenes derived from diphosphanes 12 in the sequential treatment of primary amines with n-BuLi and chlorophosphanes for preparing NH phosphinous amides [75,88] (Scheme 14). Compounds 11 and 12 are presumably derived from anions 9 and 10, respectively, generated by deprotonation of the newly formed phosphinous amide with the lithiated amine R NHLi. In solution, 9 can establish a metallotropic equilibrium with 10. 

Occasionally, attempts at introducing a new PR2 group on the nitrogen atom of an NH phosphinous amide, with the aim of preparing Ar,AT-bis(phosphino) phosphinous amides, result in the generation of monophosphazenes derived from diphosphanes, as seen in the preparation of 20 which occurs by P-P bond formation [74] (Scheme 20). The authors of this work claimed that the electron-... 

Hydrogenation of a series of /Z-isomeric mixtures of a-arylenamides with a MOM-protected /3-hydroxyl group catalyzed by a BICP-Rh complex or an Me-DuPhos complex leads to the formation of chiral /3-amino alcohol derivatives with excellent enantioselectivities.70b A 1,4-diphosphane 26 with a rigid 1,4-dioxane backbone is also very effective for this transformation (Equation (28)).76 DIOP -Rh72a and Me-DuPhos-Rh219 catalysts are also effective for this transformation. 

Synthesis of triphosphanes by Si—P bond cleavage with PCI3 and further reaction of the triphosphane formed with LiP(SiMe3)2 is described in Section IV. Starting with the lithium derivative of a suitably substituted diphosphane and linking it to the phosphorus atom... 

Fig. 16.29. Two-component variant (upper example) and three-component variant (lower example) of Stille reactions to be used for the preparation of unsaturated ketones. The phosphane ligand in the lower example is dppf [for bis(diphenylphosphino)fer-rocene], a diphosphane the structure of this ligand can be derived from the Formulas B-D.

Both observed the monoaddition products 30, but the phosphanediols 31 have been found only by Roschenthaler (227). While the methylated compound 31b decomposes above 45°C, the phosphane derivative 31a has been found to be air-stable. Dimethylphosphane was claimed by Bruker and co-workers (43) to yield the alcohol 32a, which could not be confirmed (227). Instead, the oxidation product 33a has been found together with a diphosphane 34 and fluorophosphorane 35 (227). 

P. Knochel and co-workers used diphosphines as ligands in the rhodium-catalyzed asymmetric hydroboration of styrene derivatives." The best results were obtained with the very electron rich diphosphane, and (S)-1-phenylethanol was obtained in 92% ee at -35 °C, with a regioselectivity greater than 99 1 (Markovnikoff product). A lower reaction temperature resulted in no reaction, while a higher temperature resulted in lower enantioselectivity and regioselectivity. The regioselectivity was excellent in all cases. Irrespective of the electronic nature of the substituents, their position and size had a profound effect on the enantioselectivity. 

Demay, S., Volant, F., Knochel, P. New C2-symmetrical 1,2-diphosphanes for the efficient rhodium-catalyzed asymmetric hydroboration of styrene derivatives. Angew. Chem., tnt. Ed. Engl. 2001,40,1235-1238. 

A novel chiral ligand type for asymmetric hydroformylation with rhodium and platinum complexes11 125,1 54,156 is the hydroxyproline derived (2S,4>S)-l-(/err-butoxycarbonyl)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]pyrrolidine [(-)-BPPM]2-6. As with other diphosphane systems, modifications of BPPM by exchange of either one or both of the different diphenylphosphane groups with dibenzophosphole (DBP) units [BPPM-2DBP, BPPM-4DBP and BPPM-(DBP)2] have been studied158. 

The steroidal 1,4-diphosphanes 3x- and 3/ -(diphenylphosphino)-2a-[2-diphenylphosphi-no)ethyl]-5a-cholestane and their 5//-benzo[h]phosphindole derivatives are also used as chiral ligands in hydrocyanation. While the diphenylphosphane ligands lead to moderate optical yields in the hydrocyanation of norbornene in the presence of Pd(BDA)2 (21% yield, 98% product selectivity, up to 39 % ee), the phosphole ligands only give trace amounts of product with no asymmetric induction detectable38. 

Oxidation of the hydrolysed Grignard mixture with hydrogen peroxide or bromine provides phosphinic acids 383,398,423 however, the methyl and ethyl derivatives are difficult to isolate because of their great solubility in water, and these are better obtained by way of the diphosphane disulfides.409 Thio-phosphinic acids are obtained analogously in good yield by addition of sulfur 424... 

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