Single-crystal X-ray studies have defined the structures of a number of novel adducts of the form CuX:dpex (2:1), X = (pseudo-)halide, dpex = bis(diphenylpnicogeno)alkane, Ph2E(CH2)xEPh2, E = P, As, of diverse types, solvated with acetonitrile. CuBr:dpem (2:1)2. 2MeCN (E = both P, As) are tetranuclear, derivative of the familiar ‘step’ structure, while CuCl:dpph (MeCN solvate) and CuBr:dppe (MeCN solvate) yield one-dimensional polymers (i.e., x = 1, 2, 6 for dppx, x = m, e, h), as also does CuSCN:dpam (MeCN solvate). In CuI:dpsm:MeCN (3:1:2) (‘dpsm’ = Ph2Sb(CH2)SbPh2), CuI:dpsm (2:1)2 ‘step’ units are connected into an infinite ‘stair’ polymer by interspersed (MeCN)CuI linkers.