## Abstract

The one-dimensional chain materials K_{2}CuNbSe_{4} and K_{3}CuNb_{2}Se_{12} have been synthesized at 800 and 870 °C, respectively, through the use of molten alkali-metal selenides as reactive fluxes. K_{2}CuNbSe_{4} crystallizes in space group [formula omited]-Fddd of the orthorhombic system with eight formula units in a cell of dimensions a = 5.745 (1), b = 13.444 (1), and c = 23.907 (3) Å. The structure consists of infinite linear chains separated from the K^{+} ions. These chains, which are along the c axis, consist of edge sharing of alternating NbSe_{4} and CuSe_{4} tetrahedra. The structural motif thus represents an elaboration of that in KFeS_{2}. There are no short Se⋯Se interactions and so formal oxidation states of K(I), Cu(I), Nb(V), and Se(-II) are assigned. The compound is a poor conductor, having a resistance greater than 10 MΩ cm at room temperature. K_{3}CuNb_{2}Se_{12} crystallizes in space group [formula omited]-P2_{1}/n of the monoclinic system with four formula units in a cell with dimensions a = 9.510 (6), b = 13.390 (9), and c = 15.334 (10) Å and β = 96.09 (4)°. The structure consists of an infinite Cu/Nb/Se chain separated from K^{+} cations. The infinite chain can be formulated as [formula omited][CuNb_{2}(Se)_{2}(Se_{2})_{3}(Se_{4})^{3-}] or alternatively as [formula omited][CuNb_{2}(Se)_{3}(Se_{2})_{3}(Se_{3})^{3-}] depending upon the choice of a cutoff for the length of an Se-Se bond. In the former instance the chain contains Cu(I) and Nb(IV) centers while in the latter instance it contains Cu(I) and Nb(V) centers. The two crystallographically distinct Nb atoms are seven-coordinate and the Cu atom is tetrahedral.

Original language | English (US) |
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Pages (from-to) | 3317-3320 |

Number of pages | 4 |

Journal | Inorganic Chemistry |

Volume | 30 |

Issue number | 17 |

DOIs | |

State | Published - Aug 1 1991 |

## ASJC Scopus subject areas

- Physical and Theoretical Chemistry
- Inorganic Chemistry

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