The structures of 1:1 and 1:2 adducts of phosphanetricarbonitrile with 1,4-diazabicyclo[2.2.2]octane

The structures of 1:1 and 1:2 adducts of phosphanetricarbo­nitrile with 1,4-di­aza­bicyclo­[2.2.2]octane are reported.
In the structures of 1:1 and 1:2 adducts of phosphanetricarbo­nitrile (C3N3P) with 1,4-di­aza­bicyclo­[2.2.2]octane (C6H12N2), the 1:1 adduct crystallizes in the ortho­rhom­bic space group, Pbcm, with four formula units in the unit cell (Z′ = 0.5). The P(CN)3 unit lies on a crystallographic mirror plane while the C6H12N2 unit lies on a crystallographic twofold axis passing through one of the C—C bonds. The P(CN)3 moiety has close to C 3v symmetry and is stabilized by forming adducts with two symmetry-related C6H12N2 units. The phospho­rus atom is in a five-coordinate environment. As a result of the symmetry, the two trans angles are equal so τ5 = 0.00 and thus the geometrical description could be considered to be square pyramidal. However, the electronic geometry is distorted octa­hedral with the lone pair on the phospho­rous occupying the sixth position. As would be expected from VSEPR considerations, the repulsion of the lone-pair electrons with the equatorial bonding electrons means that the trans angles for the latter are considerably reduced from 180° to 162.01 (4)°, so the best description of the overall geometry for phospho­rus is distorted square pyramidal. The 1:2 adduct crystallizes in the monoclinic space group, P21/m with two formula units in the asymmetric unit (i.e. Z’ = 1/2). The P(CN)3 moiety lies on a mirror plane and one of the two C6H12N2 (dabco) mol­ecules also lies on a mirror plane. The symmetry of the P(CN)3 unit is close to C 3v. There are three P⋯N inter­actions and consequently the mol­ecular geometry of the phospho­rus atom is distorted octa­hedral. This must mean that the lone pair of electrons on the phospho­rus atom is not sterically active. For the 1:1 adduct, there are weak associations between the phospho­rus atom and one of the terminal nitro­gen atoms from the C≡ N moiety, forming chains in the a-axis direction. In addition there are weak C—H⋯N inter­actions between a terminal nitro­gen atoms from the C≡N moiety and the C6H12N2 mol­ecules, which form sheets perpendicular to the a axis.