Cyano-linked structures in polymeric cadmium cyanide–pyridine (py) and –isoquinoline (iquin) complexes: crystal structures of [Cd(py)2][Cd(CN)4], [{Cd(CN)(py)2}3][Cd2(CN)7] and [Cd(iquin)2][Cd(CN)3(iquin)2]2

Abstract

Crystal structures of two pyridine (py)- and one isoquinoline (iquin)-ligated cadmium(II) poly(cyano)-cadmate(II) complexes, [Cd(py)₂][Cd(CN)₄]1, [{Cd(CN)(py)₂}₃][Cd₂(CN)₇]2 and [Cd(iquin)₂][Cd(CN)₃(iquin)₂]₂3 have been determined from single-crystal X-ray diffraction data; 1: orthorhombic Cccm, a= 9.386(2), b= 14.358(2), c= 14.439(2)Å, Z= 4; 2: trigonal Rc, a=b= 13.987(2) and c= 43.769(8)Å(hexagonal setting), Z= 6; and 3: (L) monoclinic P2₁/c, a= 8.178(2), b= 20.557(2), c= 16.244(3)Å, β= 97.20(2)°, Z= 2. Although they all have the composition of a base adduct of Cd(CN)₂, the structures are completely different from one another. Complex 1[i.e. Cd(CN)₂·L] has a three-dimensional framework built of an alternate array of tetrahedral [Cd(CN)₄]^2– and octahedral Cd²⁺ to which a pair of pyridine ligands ligate at the trans positions. The three-dimensional structure of complex 2[i.e. 5Cd(CN)₂·6L] is comprised of a trimeric assembly [{Cd(CN)(py)₂}₃]³⁺ and a dimeric condensate [(NC)₃Cd(CN)Cd(CN)₃]^3– linked alternately by cyano bridges extending from the latter. A one-dimensional extension of the meshed chain is seen in the structure of complex 3[i.e. Cd(CN)₂·2L], where two kinds of trans-[Cd(iquin)₂] moieties, one in an octahedral (Cd_oct) and the other in a trigonal-bipyramidal (Cd_tbpy) co-ordination, are combined with the equatorial CN groups in a 1 : 2 ratio Cd_oct:Cd_tbpy. The bulkiness of the aromatic base appears to affect the mode of cyanide linkage in these structures.