Oligomeric rare-earth-metal halide clusters. Three structures built of (Y{sub 16}Z{sub 4})Br{sub 36} units (Z = Ru, Ir)
- Iowa State Univ., Ames, IA (United States)
Suitable reactions in sealed Nb tubing at 850-950 {degrees}C gave good yields of a family of oligomeric cluster phases that were characterized by single-crystal X-ray diffraction means. The basic Y{sub 16}Z{sub 4} units ({approximately}{bar 4} symmetry) can be derived from 2+2 condensation of centered Y{sub 6}Br{sub 12}Z-type clusters or as tetracapped truncated tetrahedra Y{sub 16} that are centered by a large tetrahedral Z{sub 4}. These are surrounded by 36 bromine atoms which bridge edges or cap faces of the Y{sub 16}Z{sub 4} nuclei and, in part, bridge to metal atoms in other clusters. The principal bonding appears to be Y-Z and Y-Br, with weaker Y-Y ({bar d} {approximately} 3.70 {angstrom}) and negligible Z-Z interactions. The phase Y{sub 16}Br{sub 20}Ru{sub 4} (P4{sub 2}/nnm, Z = 2; a = 11.662(1) {angstrom}, c = 16.992 (2) {angstrom}) is isostructural with Y{sub 16}I{sub 20}Ru{sub 4} and with the new Sc{sub 16-} Br{sub 20}Z{sub 4} (Z = Fe, Os). Syntheses only in the presence of Ir and ABr-YBr{sub 3} fluxes (A = K-Cs) produce Y{sub 16-} Br{sub 24}Ir{sub 4} (Fddd, Z = 8; a = 11.718(3) {angstrom}, b = 22.361(7) {angstrom}, c = 44.702(2) {angstrom}), in which the electron-richer Ir interstitials are compensated by four additional bromine atoms and altered bridging between macroclusters. Larger amounts of YBr{sub 3} yield a third example, Y{sub 20}Br{sub 36}Ir{sub 4} (Y{sub 16}Br{sub 24}Ir{sub 4}{center_dot}4YBr{sub 3}, I4{sub 1}a, Z = 4; a = 12.699(1) {angstrom}, c = 45.11- (1){angstrom}). Here infinite zigzag chains of YBr{sub 6/2} octahedra that share cis edges lie between and bridge to the Y{sub 16}Ir{sub 4} clusters. All of these phases contain 60-electron, closed-shell macroclusters. Y{sub 16}Br{sub 20}Ru{sub 4} and Y{sub 20}Br{sub 36}ir{sub 4} were found to exhibit temperature-independent (Van Vleck) paramagnetism with values typical of those found for other rare-earth-metal, zirconium, niobium, and tantalum cluster halides.
- OSTI ID:
- 530810
- Journal Information:
- Inorganic Chemistry, Vol. 35, Issue 24; Other Information: PBD: 20 Nov 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Zirconium bromide cluster chemistry. A new tunnel structure in A{sub 5}Zr{sub 6}Br{sub 15}Be (A = Rb, Cs)
{beta}-K{sub 4}La{sub 6}I{sub 14}Os: A new structure type for rare-earth-metal cluster compounds that contains discrete tetrahedral K{sub 4}I{sup 3+} units