Bis(μ-N-nitroso-N-phenylhydroxylaminato)-κ3 O,O′:O′;κ3 O′:O,O′-bis[(N-nitroso-N-phenylhydroxylaminato-κ2 O,O′)lead(II)]

The four cupferronate ions in the dinuclear title compound, [Pb2(C6H5N2O2)4], O,O′-chelate to the two PbII atoms; two of the four nitroso O atoms are also involved in bridging. The geometry of both five-coordinate PbIIatoms is distorted Ψ-octahedral; if another two longer intermolecular Pb⋯O interactions [at 2.955 (1) and 3.099 (1) Å] are considered, the geometry is a distorted Ψ-square antiprism.

The four cupferronate ions in the dinuclear title compound, [Pb 2 (C 6 H 5 N 2 O 2 ) 4 ], O,O 0 -chelate to the two Pb II atoms; two of the four nitroso O atoms are also involved in bridging. The geometry of both five-coordinate Pb II atoms is distorted Éoctahedral; if another two longer intermolecular PbÁ Á ÁO interactions [at 2.955 (1) and 3.099 (1) Å ] are considered, the geometry is a distorted É-square antiprism.

Related literature
For the spectrospic assigment of the structure of the lead derivative, see: Bottei & Schneggenburger (1970). For the structure of the organic ligand, see: Hickmann et al. (1979).

Comment
The cupferronate ion is a common ion used for the complexation of metals; the crystal structure of the chelate has been reported (Hickmann et al., 1979). The synthesis of the lead(II) derivative has been known for a long time (Bottei & Schneggenburger, 1970), and the compound was assumed to exist as a mononuclear compound. The compound is, in fact, a dinuclear compound (Scheme I). The four cupferronate ions in dinuclear [Pb(C 6 H 5 N 2 O 2 ) 2 ] 2 O,O'-chelate to the lead(II) atom; two of the four nitroso O atoms are also involved in bridging (Fig. 1). The geometry of both five-coordinate lead atoms is Ψ-octahedral; if another longer intermolecular Pb···O interactions (approx. 3.0 Å) are considered, the geometry is a Ψsquare-antiprism (Fig. 2).

Experimental
Lead(II) nitrate (0.33 g, 1 mmol) dissolved in ethanol (20 ml) was added to the cupferron ligand (0.31 g, 2 mmol) dissolved in ethanol (20 ml). The mixture was stirred and then set aside for the growth of brown colored crystals.

Refinement
Hydrogen atoms were placed in calculated positions (C-H 0.95 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C).