Phosphane diphosphane

Diphosphane, P2H4, is a colourless liquid (mp 174K, bp 329 K), and is toxic and spontaneously inflammable when heated, it forms higher phosphanes. Diphosphane is formed as a minor product in several reactions in which PH3 is prepared (e.g. reaction 14.9) and may be separated from PH3 by condensation in a freezing mixture. It exhibits no basic properties. 

Caminade and Majoral reacted phosphorus-containing dendrimers with various transition metal complexes (Fig. 7) [ 113 ]. Via phosphane, diphosphane, or P=N-P=S ligands, they were able to incorporate several metals (Pd, Pt, Rh, Au, Fe, W, Zr) either in the core or in the periphery of their dendrimers. The dendritic palladium and ruthenium complexes 7 have been introduced in Stille couplings, Knoevenagel condensations and diastereoselective Michael additions. A positive dendritic effect and high stability of dendritic Pd complexes has been observed. Separation occurred by precipitation with ether and reuse was reported. 

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... 

High rates and selectivities are attainable only by the coordination of structurally well-designed catalysts and suitable reaction conditions. The base system employs a [RuCl2(phosphane)2(l,2-diamine)] complex as precatalyst, isopropanol serving both as solvent and hydrogen donor and in the presence of base, typically t-BuOK. Use of chiral diphosphanes, particularly BINAP compounds, and/or chiral diamines... 

The reaction of GeCl2 with phosphane 123 furnished thermally unstable diphosphene 124, which at room temperature underwent cyclization to the bicyclic diphosphane 125 with liberation of Pr PCl (Scheme 42) <2001MGM609, 2004JOM(689)1331>. 

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.

Die Oxidation von Tetraphenyl-diphosphan mit Luftsauerstoff in Toluol fiihrt norma-lerweise zu Tetraphenyl-diphosphan-bis-oxid. Bei Zusatz von katalytischen Mengen Chlor-diphenyl-phosphan erhalt man jedoch direkt Diphenylphosphinsaure-anhydrid... 

The inverted process, however, of transforming 1,6-diphosphahexa-1,5-diene b into 3,4-diphosphahexadiene or divinyl diphosphane proceeds under very mild conditions [Eq. (51)]. The diphosphide, prepared from succinylchloride and phenylbis(trimethylsilyl)phosphane between —70 and — 80°C, rearranges after silyl migration above 0°C, forming the spectroscopically detectable 1,6-diphosphahexadiene intermediate, and finally ending up with the divinyl diphosphane via a [3.3] sigmatropic bond shift (101). 

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). 

Salt 7 was smoothly reduced by tetrakis(dimethylamino)ethene in acetonitrile to the intense green radical 10. Crystals of 10 as well as its hexane solution decompose at ambient temperature. Thereby diphosphirane 9 was generated in ca. 30% yield in addition to diphosphane Ar(Me)PP(H)Ar (43%), diphosphene 6 (ca. 10%) and phosphane ArP(Me)(H) (ca. 17%). The formation of diphosphirane 9 and Ar(Me)PP(H)Ar was explained by the disproportionation of radical 10 (Scheme 3) <2001AGE723>. 

Dichloro-(t-butyl)-phosphane and bromomagnesium 4-methylbenzenetellurolate yielded an aryltelluro-substituted diphosphane". ... 

PHEP-type ligands, since, through activation to the bis(phosphonic dichlorides) they react with a large variety of aryl, heteroaryl or alkyl Grignard reagents to provide the bis(phosphane oxides), which then are reduced to the diphosphanes (cf. [56] and literature cited therein). 

The selectivity of butadiene cyclooligomerization in the presence of bis(l,5-cyclooctadiene)-nickel(0) varies with the phosphane added, e.g., monophosphanes, such as (S)-ter/-butyl(iso-propyl)phenylphosphane and (- )-dimethyl(phenyl)phosphane, or diphosphanes, such as Diop. In all cases, 1,5-cyclooctadiene is preferentially formed, along with 4-vinylcyclohexene, ill a 4.5-6 1 ratio. The optical purity of the 4-vinylcyclohexene reaches 12% at a monophosphane/ nickel ratio of about 8 1 and is much lower with Diop57. The use of various 1,3,2-dioxaphospho-lanes with bulky substituents leads to a significant improvement in product selectivity (favoring 4-vinylcyclohexene over 1,5-cyclooctadiene in a ratio of up to 1 0.3) and in the enantioselectiv-ity. The best Optical yield (35% ee, later corrected to 24% ee58) was obtained with a nickel complex of diethyl 2-toT-butyl-l,3,2-dioxaphospholane-4,5-dicarboxylate (1) at 20 C57. 

There arc two main classes of catalysts neutral chlororhodium(I) diphosphane complexes and cationic rhodium(I) complexes having the general structure [Rh(diphosphane)(olefin)2]+. The cationic complexes are often more active and more selective than the corresponding chloro complexes60. In contrast to heterogeneous hydrogenation catalysts rhodium phosphane complexes are not pyrophoric. However, they are sensitive to oxygen and should be stored and handled under an inert atmosphere. 

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