The metal complex host catena-[(1,2-diaminopropane)-cadmium(II) tetracyanonickelate(II)] which provides channel cavities for straight- and branched-chain aliphatic guests

Abstract

A number of inclusion compounds [(pn)Cd(CN)₄Ni]·nG (pn = 1,2-diaminopropane; n= 0.3–0.5) have been prepared for various straight-and branched-chain aliphatic guest molecules (G), which are accommodated in the three-dimensional structure of the metal complex host. This structure contains channel cavities surrounded by tetracyanonickelate(II) moieties linked alternately to the Cd which is chelated by the pn. The inclusion compounds are grouped into two types, U- and T-type, according to the shape of the channel revealed by their single-crystal structures. In the monoclinic U-type structure the point-symmetric arrangement of the pn chelate rings provides a snake-like channel, analogous to the spiral ones in urea inclusion compounds, for the straight-chain aliphatic guests pentane, hexane, heptane, diethyl ether, ethane-1,2-diol, 1-bromo-butane and -pentane. In the orthorhombic T-type structure the mirror-symmetric arrangement of the pn chelate rings results in nodal channels, similar to those in thiourea inclusion compounds for 1,1,2,2-tetrachloroethane, 2-chlorobutane, 1,2-dichloropropane, PrⁱOH, 1,2-dichloro- and 1,2-dibromo-ethane and 1,3-dichloropropane. For the straight-line dihalogenoalkane guests the halogen atoms appear to contribute to the preference for the nodal channel by formation of hydrogen bonds with the pn-amino group.