Phosphorus hydrides double

Of course, the gas-phase thermochemistry of ions is not solely restricted to the measurement of the quantities described above a wide range of other ion affinities have been measured, including methyl cation affinities, hydride affinities and halide affinities . Further, such measurements can often be related to unknown neutral thermochemistry via the appropriate thermochemistry cycle. For example, the phosphorus-carbon double bond strength (the sum of the a and n bond contributions) in HP=CH2 was recently estimated via mass spectrometric measurements to be 101 7 kcaF (ref. 43). 

The basicity of phosphorus-containing ligands and their ability to dissociate to give sites for attachment of the double bonds of the substrate play an important role in determining the type of product formed. Another mechanism, based on formation of nickel hydrides, is available, however, for oligomerization and polymerization, as we shall see later. 

During studies on the total synthesis of Aspidosperma type alkaloids, unexpected difficulty was encountered in attempts to reduce the amide carbonyl group of the intermediate 1. Thus, many attempts to reduce 1 with lithium aluminium hydride resulted in reduction of both the amide carbonyl group and the C=C double bond. In an effort to circumvent this problem 1 was reacted with hot phosphorus oxychloride and the intermediate thus obtained treated with sodium borohydride in anhydrous methanol. The product which was isolated, however, was the pentacyclic compound 2, which was obtained in 50% yield. 

Reduction of triazolinones with phosphorus sulhde has been one of the early routes to triazoles (o5JCS625). Milder reactions may differentiate between conjugation of the ring double bond with C=0 (139) or the lack of it (140) as in Scheme 48 (71bsf3296). The formation of triazole in the reduction of the triazolinone (140) with lithium aluminum hydride (7ibsf3296) is explicable through the formation of a hydroxytriazoline intermediate. 

The synthesis of polyphosphines containing combinations of primary, secondary, and tertiary phosphorus atoms by the base-catalysed addition of P—H across the carbon-carbon double bond of vinyl phosphonates, followed by reduetion with lithium aluminium hydride, has again been described. The preparation of I,2-bis(phosphino)ethane from the bis-phosphonate (17) by reduction with lithium aluminium hydride has been reported in detail. ... 

The chemistry of phosphorus and the heavier congeners is dominated by element to element (E-E) single bonds and, particularly in the case of phosphorus, the availability of l>d orbitals to form dir—pir double bonds with a variety of other atoms such as oxygen, nitrogen, and even sulfur. Orbital participation results in expanded octets as found in compounds such as PF5, SbCl5, X3P=0 (where X=F, Cl, Br, I), the phosphorus oxoadds and oxoanions, and a class of compounds called the phosphazenes. We will take up many of these cases as we encounter them in the appropriate sections under our usual survey of the hydrides, oxides and oxoacids, and halides. For now, however, let s take a quick look at the phosphazenes, formerly called the phosphonitriles, that contain both N and P atoms in the same molecule. 

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