The crystal and molecular structure of bis(2,3-butanedione dioximato)chloro-(hydroxodiphenylarsine)cobalt(III): assignment of the nature of the arsenic-based ligand

The Co(II) cobaloximes, (B)Co(dmgH) 2 (where B = phosphine or phosphite; dmgH = dimethylglyoximato monoanion) react with (C 6 H 5 ) 2 AsCl to form ClCo(dmgH) 2 B and a compound of formula C 20 H 25 AsClCoN 4 O 5 . A crystal structure analysis of the arsenic compound indicated it to be bis(2,3-butanedione dioximato)chloro(diphenylhydroxoarsine)cobalt(III), [(C 6 H 5 ) 2 As(OH)Co(dmgH) 2 Cl]. The crystals are orthorhombic, space group Pna2 1 , a = 15.334(2), b = 11.173(2), c = 13.745(4) Å at 19(2) °C with Z = 4. The structure has been refined by the least-squares method to a weighted residual of 0.071 using 2345 independent reflections. The Co atom is bonded equatorially to two dmgH ligands (average [CoN] = 1.89(1) Å) with a Cl atom above this plane ([CoCl] = 2.252(2) Å) and the As atom of the (C 6 H 5 ) 2 As(OH) group below it ([CoAs] = 2.322(1) Å). The [AsO] bond length is 1.781(7) Å, corresponding to a single bond and is consistent with the observed H atom on the oxygen atom.