Arsine oxides structure

Calcium-binding proteins, 6, 564, 572, 596 intestinal, 6, 576 structure, 6, 573 Calcium carbonate calcium deposition as, 6, 597 Calcium complexes acetylacetone, 2, 372 amides, 2,164 amino acids, 3, 33 arsine oxides, 3, 9 biology, 6, 549 bipyridyl, 3, 13 crown ethers, 3, 39 dimethylphthalate, 3, 16 enzyme stabilization, 6, 549 hydrates, 3, 7 ionophores, 3, 66 malonic acid, 2, 444 peptides, 3, 33 phosphines, 3, 9 phthalocyanines, 2,863 porphyrins, 2, 820 proteins, 2, 770 pyridine oxide, 3,9 Schiff bases, 3, 29 urea, 3, 9... 

Numerous nickel(II) complexes with a variety of phosphine and arsine oxides have been reported, but only a few X-ray crystal structures have been determined. In some cases the structures assigned to the complexes are not completely certain.1800 A selection of nickel(II) complexes is reported in Table 86. 

The arsine oxide 2-Ph2As(0)CgH4C00H provides interesting further information on these species, as there is evidence that in chloroform solution it exists unexpectedly as a monocyclic acyloxyhydroxyarsorane 79, while in the solid state it has the novel resonance hybrid structure 8(). Here arsenic has five-coordinate trigonal bipyramidal geometry with equatorial carbon atoms (C—As—C 116.4,118.8 and 119.4 A) and axial oxygens. 

The pyrolysis of organoarsenic compounds containing the arsenyl moiety has some limited preparative applications [arsenyl (As=0) by analogy with phosphoryl (P=0)]. The compounds are based on the arsonic acid RAs(0)(0H)2, the arsinic acid R2As(0)0H and the arsine oxide R3As=0 structures. The acids are in interesting contrast with the phosphorus series. The phosphonic and phosphinic esters are prepared from the phosphorus(III) precursors via the Arbuzov synthesis. This synthetic route fails with the arsenic analogues, and further, if an alkyl halide or a salt is added in the pyrolysis of arsonic or arsinic acid esters a retro-Arbuzov reaction takes place . ... 

The few known arsine oxide complexes are very similar in behavior to the corresponding phosphine oxide analogues. The only structurally characterized examples of this class are UCI4 (Et3AsO)2 and UBr4(Ph3AsO)2 both are trans octahedral. 

There are many compounds in which As and Sb form tetrahedral bonds (valence group 8) as, for example, GaAs, GaSb, InAs, and InSb which, like the corresponding phosphides, crystallize with the zinc-blende structure. Tetrahedral bonds are formed by As in the ASO4 ion in orthoarsenates (and arsine oxides) but note the quite different behaviour of Sb in its oxy-compounds (see later). 

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