Phosphine and Arsine Derivatives of the Group 1(b) Metals: Volatile Derivatives of Gold

Abstract

WE have shown that the trialkyl phosphine and arsine derivatives of cuprous iodide, previously considered to be R₃P(As).CuI, have a fourfold macro-molecule¹, [R₃P(As)CuI]₄, and are therefore tetrakis—[iodo-trialkylphosphine (or arsine)-copper]. A complete X-ray examination of the triethyl-arsine member, [Et₃AsCuI]₄, showed that the four copper atoms occupy the apices of a regular tetrahedron ; the iodine atoms are situated each above the central point of one face of this tetrahedron, so that they also form a tetrahedron external to that of the copper atoms. Beyond each copper atom is an arsenic atom lying on the elongation of the axis joining the centre of the inner tetrahedron to the copper atom. The iodine atoms are thus 3-covalent, each being joined to the three neighbouring copper atoms apparently by one covalent and two co-ordinate links: if this is so, the stereochemistry of the 3-covalent iodine atom must be similar to that of 3-covalent sulphur, and the iodine atom can be regarded as occupying one apex of a tetrahedron with its valencies directed towards the other three apices.