New copper (I) cyanide networks: Interpenetration, self-penetration and polymorphism

The structures of four alkali-metal copper (I) cyanides, KCu2(CN)3.H2O-II (I), K2Cu3(CN)5 (II), CsCu3(CN)4 (III) and KCu3(CN)4 (IV) are described. Three of these, ((II)–(IV)), with previously unknown ACN:CuCN ratios have new copper-cyanide frameworks, whilst (I) is a new polymorph of KCu2(CN)3.H2O. These structures are discussed in terms of assembly from the simple building units Cu(CN)2/2, Cu(CN)3/2, Cu(CN)2/2(CN)1/1 and Cu(CN)4/2. Compounds (I), (II) and (III) are layered materials based on (6,3) nets containing (CuCN)6 rings (I) and (CuCN)8 rings ((II) and (III)). In compound (IV), (4,4) nets containing (CuCN)12 rings link to generate a three-dimensional network. Both (III) and (IV) are examples of interpenetrating solids in which two and four identical networks interweave, respectively. These materials illustrate the structural versatility of copper (I) in cyanide frameworks.

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