Abstract:

The synthesis, NMR spectroscopy, single-crystal X-ray structure, and solution electrochemistry of the new compound [2,6-\CH(CH3)\(2)C6H3](3) As, abbreviated as Dipp(3)As, is reported. The molecule, prepared by reaction of AsCl3 with a preformed aryl copper reagent, Dipp(4)Cu(4), crystallizes in the hexagonal space group R3 as a racemic twin. The sum of angles around As, Sigma angle\CAsC\, is 329.13(3)degrees in the X-ray structure and 329.17 degrees from an R-B3LYP/6-31G(d,p) hybrid density functional theory calculation. The aromatic rings are quite distorted with both the ipso carbon and especially the As atom significantly out of plane by 0.503(3) angstrom . The ambient temperature NMR spectrum fits for C-3 symmetry implying that inversion is slow on the NMR timescale. Cyclic voltammetry on a glassy carbon electrode in CH2Cl2 with 0.4 M [(Bu4N)-Bu-n][PF6] over scan rates of 0.05-0.8V s(-1) and temperatures of 22 +/- 28 degrees C produced one quasi-reversible process with E-m1 = +0.43V at a scan rate of 0.20 V s(-1) and a second irreversible process with a peak potential of +1.45 V (v. Fc(+/0)). The diffusion coefficient has been measured as 3.3 +/- 0.1 x 10(-6) cm(2) s(-1) in CH2Cl2 solution containing 0.4 M [(Bu4N)-Bu-n][PF6]. Chemical oxidation with AgPF6 in CH2Cl2 in degassed solutions in sealed vessels allowed for recording of characteristic EPR spectra; at 293 K, a (As-75) = 26.1 mT and g = 2.021. In frozen solution, an almost isotropic spectrum is obtained (g(parallel to) - 2.000 mT and g(perpendicular to) - 2.003 mT) and the hyperfine splitting constants are a(parallel to) - 47.9 and a(perpendicular to) - 19.0 mT, leading to an estimate for the structure being slightly pyramidal with Sigma angle\CAsC\ approximate to 351 degrees.