Arsinophosphonium cations from arsenium-phosphine and -bisphosphine coordination chemistry

A new 14 pi-electron tricyclic organoarsenium cation (5-hydrophenarsazinium, AN, C12H9AsN+) has been prepared in situ and used as a Lewis acceptor with trimethylphosphine, triphenylphosphine, bis(diphenylphosphino)methane (dppm), bis(dimethylphosphino) methane (dmpm), and 1,4-bis(diphenylphosphino)benzene (dppb) ligands. Solid-state structures and spectroscopic characterization data are reported for complexes of the general formula [AN-PMe3](+), [AN-PPh3](+), [AN-dppm](+), [AN-dppm-AN](2+), [AN-dmpm-AN](2+), and [AN-dppb-AN](2+) as tetrachlorogallate salts. Depending on reaction stoichiometry, dppm forms adducts at one or both of the donor sites. Structural comparisons with analogous complexes of phosphenium cations provide interesting similarities and differences.