Arsenic planar compounds

The corresponding palladium compound (157) must be formulated as [Pd(TA)Br]+Br. The cation is essentially square-planar, but the bromine atom is displaced 10° out of the arsenic-palladium plane. Such a distortion is very unusual for palladium, and may be due to a steric effect of the alkyl chains in the arsine ligand. This might similarly account for the distortion of the nickel complex from a square pyramidal shape. 

The anion derived from 1,2-phenylenephosphorochloridite is one of the rare examples of a radiogenic radical anion produced by electron capture by a phosphine. In the case of arsenic compounds, AsCls" and AsFj" were produced by y-irradiation of polycrystalline trihalogenoarsines at 77 This last species exhibits hyperfine coupling with As (T// = 666MHz), two of one kind (r y = 240MHz) and one F of another kind (T// = 78MHz). These arsenic radical anions adopt an approximate planar T-shape structure with the unpaired electron located in an orbital perpendicular to the molecular plane. 

Rather surprising, however, are the monomeric structures of PhAsB(mesityl)2 Li(THF)3 and PhAsB(mesityl)2-Li(TMEDA)2, ascribed to stabilization by the sterically demanding mesityl groups . In agreement with multiple As—B bonding, the separations are short (1.93 A) and these compounds represent the first examples of bonds between sp arsenic centres and planar boron atoms. 

The aluminium compound, (Et2AlAsBu2)2, obtained from triethylaluminium and dibutylarsine by loss of ethane contains a four-membered ring (As—A12.57 A) and, as shown in Table 3, four-membered, often planar and centrosymmetric rings dominate the related arsenic-gallium species 62. The geometry at each of the ring atoms is distorted tetrahedral. 

The compounds with the autunite-type sheet and monovalent interlayer cations are listed in Table 10 (phosphates) and in Table 11 (arsenates). In the two isostructural Li-bearing uranyl compounds [110, 119], Li is in fourfold coordination by H2O groups in the interlayer region. Hydrogen bonds link the H2O groups into square-planar sets, which are connected via the Li-0 bonds (Fig. 29). Hydrogen bonds extend from these sets to the anions at the equatorial vertices of uranyl square bipyramids, which are also shared with tetrahedra. 

Diverse chemicals have been reported to affect measured endpoints of fish thyroidal status. These chemicals include aromatic hydrocarbons, planar halogenated aromatic hydrocarbons (dioxans, furans, coplanar PCBs), organochlorine, organophosphorus and carbamate pesticides, chlorinated paraffins, cyanide compounds, methyl bromide, phenol, ammonia, metals (aluminum, arsenic, cadmium, lead and mercury), low pH conditions, environmental steroids and a variety of pharmaceutical agents. For the following reasons their modes of action appear complex and are poorly understood16. 

The barrier to pyramidal inversion at arsenic has been calculated for a variety of compounds, and where experimental data are available there is satisfactory agreement. The low barrier to inversion in the 6ir-clectron arsoles (117) is noteworthy, pointing to extensive delocalization in the planar transition state and lending support to the contention that cyclic delocalization also occurs in the pyramidal ground state. The six-membered arsabenzene molecule (118 R = H) is... 

---