Pyridinium tetrakis(1,1,1-trifluoropentane-2,4-dionato)dysprosate

In the anion of the title compound, (C5H6N)[Dy(C5H4F3O2)4], the central metal ion, Dy3+, is coordinated by four bidentate 1,1,1-trifluoropentane-2,4-dionate (TAA) ligands, forming an approximate square-antiprismatic configuration. The pyridinium cation is connected to the complex ion by an N—H⋯O hydrogen bond and electrostatic interactions in the crystal. There are two kinds of disorder in the structure, one involving rotational disorder of a CF3 group [occupancy ratio 0.560 (15):0.440 (15)] and the other involving an exchange between a CF3 group and CH3 group within a given bidentate ligand (occupancy ratio 0.64:0.36).

In the anion of the title compound, (C 5 H 6 N)[Dy(C 5 H 4 F 3 O 2 ) 4 ], the central metal ion, Dy 3+ , is coordinated by four bidentate 1,1,1-trifluoropentane-2,4-dionate (TAA) ligands, forming an approximate square-antiprismatic configuration. The pyridinium cation is connected to the complex ion by an N-HÁ Á ÁO hydrogen bond and electrostatic interactions in the crystal. There are two kinds of disorder in the structure, one involving rotational disorder of a CF 3 group [occupancy ratio 0.560 (15):0.440 (15)] and the other involving an exchange between a CF 3 group and CH 3 group within a given bidentate ligand (occupancy ratio 0.64:0.36).

Comment
Rare earth-β-diketone complexes have attracted considerable attention in the past decades owing to their important applications as laser (Iwamuro et al., 1997), fluorescent probe (Tsukube & Shinoda, 2002) and NMR reagents (Chu & Elgavish, 1995). As part of our interest in this field, we have been engaged in a major effort directed toward the development of syntheses of new lanthanide-β-diketon complexes.
The structure of the title Dy 3+ complex is shown in

Experimental
A mixture of Dy 2 O 3 (0.186 g) and concentrated hydrochloric (5 mL) was heated and distilled to slight dryness, yielding a crystalline precipitate (DyCl 3 ). Then, the DyCl 3 solid was redissolved in 5 mL absolute ethanol, and heated with 10 mL of absolute ethanol solution containing HTAA (0.50 mL) and pyridine (0.32 mL) at about 363 K. The reaction mixture was maintained at ambient temperature for one month until yellow crystals formed.

Refinement
All F atoms were found to be disordered. There is disorder of the two different types: 1) disorder due to rotational disorder of the CF 3 group bonded to a single carbon. F4, F5, and F6 atoms was split into to two sets of positions using restraints on their anisotropic displacement parameters. The major and minor disorder components had refined occupancies of 0.56 (2) and 0.44 (2), respectively; 2) disorder due to exchange of CH 3 and CF 3 groups on the same ligand. Namely, F10, F11, and F12 as well as related H atoms were modelled over two sets of positions using restraint on their anisotropic displacement parameters. The major and minor disorder components had refined occupancies of 0.64 (1) and 0.36 (1), respectively. In the final refinement, the occupancies of these disordered atoms were fixed to aid convergence. Atoms F11B, F4, F5, F6, F4B, F5B, and F6B were refined anisotropically using 42 restraints (ISOR) and the geometrical parameters of CF 3 group were refined using 36 restraints (DFIX and DANG) because of the unacceptable parameters of their ellipsoids and distances  Fig. 1. A view of the structure of the complex with displacement ellipsoids drawn at the 30% probability level. H atoms without H-bond (dotting line) and minor disorder components were omitted for clarity.