1,2,4,5-Tetramethyl-3,6-diphenyl-1,2,4,5-tetraaza-3,6-diphosphinane

The title compound, C16H22N4P2, crystallizes about a centre of symmetry, leading to a chair conformation of the heterocyclic ring as is commonly found for this type of compound.

The title compound, C 16 H 22 N 4 P 2 , crystallizes about a centre of symmetry, leading to a chair conformation of the heterocyclic ring as is commonly found for this type of compound.

S1. Comment
Compound (I) has a centre of symmetry and the six-membered ring adopts a chair conformation with the phenyl groups on the phosphorous atoms being trans to each other. Reddy et al. (1994) have observed in related compounds, e.g.

S2. Experimental
In an attempt to crystallize bis(diphenylphosphino)dimethylhydrazine (II) (for synthesis see Reddy et al., 1995), the worked-up diethylether reaction mixture was concentrated and kept at -20 °C for two days. Two small crystals were formed and on analysis of one of the crystals, (I) was identified. Analysis of the 31 P NMR spectrum of (II) showed (I) to be present in less than 5%. Further analysis of (I) was not attempted due to the small amount of material available.

S3. Refinement
The H atoms were positioned geometrically and allowed to ride on their respective parent atoms, with C-H = 0.93 (Ar -H) or 0.96 (CH 3 ) Å, and with U eq = 1.2 (Ar-H) or 1.5 (CH 3 ) U eq (C).

Figure 1
Molecular structure of (I) drawn with displacement ellipsoids at the 50% probability level. Hydrogen atoms have been omitted for clarity.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.