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

In the structures of 1:1 and 1:2 adducts of phosphanetricarbo­nitrile (C(3)N(3)P) with 1,4-di­aza­bicyclo­[2.2.2]octane (C(6)H(12)N(2)), 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 C(6)H(12)N(2) 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 C(6)H(12)N(2) units. The phospho­rus atom is in a five-coordinate environment. As a result of the symmetry, the two trans angles are equal so τ(5) = 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, P2(1)/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 C(6)H(12)N(2) (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 C(6)H(12)N(2) mol­ecules, which form sheets perpendicular to the a axis.