Tetra­aqua­(4,4'-dimethyl-2,2'-bipyridine-[kappa]²N,N')nickel(II) sulfate monohydrate: a simple molecule with an extremely complex hydrogen-bonding scheme

The title ionic compound, [Ni(C₁₂H₁₂N₂)(H₂O)₄]SO₄·H₂O, is composed of an Ni^II cation coordinated by a chelating 4,4'-di­methyl-2,2'-bipyridine ligand via its two N atoms [mean Ni-N = 2.056 (2) Å] and by four aqua ligands [mean Ni-O = 2.073 (9) Å], the net charge being balanced by an external sulfate anion. The whole structure is stabilized by a solvent water mol­ecule. Even though the individual constituents are rather featureless, they generate an extremely complex supra­molecular structure consisting of a central hydrogen-bonded two-dimensional hydro­philic nucleus made up of complex cations, sulfate anions and coordinated and solvent water mol­ecules, with pendant hydro­phobic 4,4'-dimethyl-2,2'-bipyridine ligands which inter­act laterally with their neighbours via [pi]-[pi] inter­actions. The structure is compared with closely related analogues in the literature.

Two complexes derived from the reaction of M₃(CO)₁₂ clusters (M = Ru, Os) with the 9-(triphenyl­phosphonio)­fluoren­ide ylide: tricarbonyl[9-(tri­phenyl­phosphonio)fluorenyl­idene]­ruthenium and nona­carbonyl-μ₃-fluorenyl­idene-μ₂-hydrido-triangulo-triosmium(III)

Tricarbon­yl[9-(triphenyl­phospho­nio)fluorenyl­idene]ruthenium, [Ru(C₃₁H₂₁P)(CO)₃], (I), is mononuclear, consisting of a single Ru centre, to which three carbonyl units and a chelating μ₃-9-(triphenyl­phospho­nio)fluorenide ylide bind to generate a distorted octa­hedral RuC₆ core. Nonacarbonyl-μ₃-fluorenyl­idene-μ₂-hydrido-triangulo-triosmium(III), [Os₃H(C₁₃H₇)(CO)₉], (II), is trinuclear and presents a triangular triosmium core, nine carbonyl ligands and one fluorenyl­idene ligand. Two of the Os^III centres present a highly distorted hexa­coordinated Os(Os₂C₄) core and are in turn bridged by a hydride ligand. The remaining Os^III cation is octa­coordinated, with an Os(Os₂C₆) nucleus. The crystal structures of both compounds are the result of nondirectional forces, much resembling the packing of weakly inter­acting quasi-spherical units, viz. the mol­ecules themselves in (I) and centrosymmetric π–π-bonded dimers in (II).