The structures of 1:1 and 1:2 adducts of phosphanetricarbonitrile with 1,4-diazabicyclo[2.2.2]octane
Abstract
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)3unit lies on a crystallographic mirror plane while the C6H12N2unit lies on a crystallographic twofold axis passing through one of the C—C bonds. The P(CN)3moiety has close toC3vsymmetry and is stabilized by forming adducts with two symmetry-related C6H12N2units. The phosphorus atom is in a five-coordinate environment. As a result of the symmetry, the twotransangles 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 thetransangles 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/mwith two formula units in the asymmetric unit (i.e. Z' = 1/2). The P(CN)3moiety 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)3unit is close toC3v.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[triple-bond] N moiety, forming chains in thea-axis direction. In addition there are weak C—H...N interactions between a terminal nitrogen atoms from the C[triple-bond]N moiety and the C6H12N2molecules, which form sheets perpendicular to theaaxis.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 16, 2021
- Source ID
- 10.1107/s2056989021011464
Entities
People
- Andrew P Purdy
- Christopher A. Klug
- Ray J Butcher
Organizations
- Office of Naval Research