A dimer of bis­(N-heterocyclic carbene)rhodium(I) centres spanned by a dibenzo-18-crown-6 bridge from synchrotron radiation

The compound (μ-3,3',3'',3'''-{[2,5,8,15,18,21-hexa-oxatricyclo-[20.4.0.0(9,14)]hexa-cosa-1(22),9,11,13,23,25-hexa-ene-11,12,24,25-tetra-yl]tetra-kis-(methyl-ene)}tetra-kis-(1-methyl-1H-imidazol-2-yl))bis-[(η(4)-cyclo-octa-1,4-diene)rhodium(I)] bis-(hexa-fluoridophosphate) acetonitrile sesquisolvate dihydrate, [Rh2(C8H12)2(C40H42N8O6)](PF6)2·1.5CH3CN·2H2O, crystallized from acetonitrile under an atmosphere of diethyl ether. In the crystal structure, the complex cation exhibits two square-planar Rh(I) centres, each bound by a cyclo-octa-diene (COD) ligand and by two adjacent imidazolyl-idene N-heterocyclic carbene (NHC) donors from the same phen-oxy ring of the {[dibenzo-18-crown-6-11,12,24,25-tetra-yl]tetra-kis-(methyl-ene)}tetra-kis-(1-methyl-1H-imidazol-2-yl) (L) ligand. The dibenzo-crown ether bridge of L spans the Rh centres and forms hydrogen bonds with water mol-ecules. One water mol-ecule with half occupancy bridges adjacent macrocycles in the lattice. Another water with full occupancy forms weak hydrogen bonds to the crown ether O atoms and is, in turn, part hydrogen bonded by a lattice water with half occupancy. The latter water is within hydrogen-bonding distance of a fourth water also with partial occupancy. The result of these inter-actions is the formation of a layer in the ab plane. Two PF6(-) ions, one of which is twofold disordered, and one ordered and one twofold disordered (with 0.5 occupancy) lattice acetonitrile mol-ecules complete the crystal structure.