Abstract
In the structures of 1:1 and 1:2 adducts of phosphanetricarbo-nitrile (C3N3P) with 1,4-di-aza-bicyclo-[2.2.2]octane (C6H12N2), the 1:1 adduct crystallizes in the ortho-rhom-bic 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 phospho-rus 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 octa-hedral with the lone pair on the phospho-rous 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 phospho-rus 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) mol-ecules also lies on a mirror plane. The symmetry of the P(CN)3 unit is close to C 3v. There are three P⋯N inter-actions and consequently the mol-ecular geometry of the phospho-rus atom is distorted octa-hedral. This must mean that the lone pair of electrons on the phospho-rus atom is not sterically active. For the 1:1 adduct, there are weak associations between the phospho-rus atom and one of the terminal nitro-gen atoms from the C≡ N moiety, forming chains in the a-axis direction. In addition there are weak C-H⋯N inter-actions between a terminal nitro-gen atoms from the C≡N moiety and the C6H12N2 mol-ecules, which form sheets perpendicular to the a axis.
Highlights
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 (Z0 = 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 electronic geometry is distorted octahedral with the lone pair on the phosphorous occupying the sixth position
Summary
Phosphorus tricyanide reacts in solution with nitrogen bases to produce a large mixture of products. This occurs with dicyanamides (Epshteyn et al, 2019), amines, and others. A reaction with CNÀ was reported to produce an unusual dianion, P2C10N10, which was structurally characterized (Schmidpeter et al, 1985). Most of the products from these reactions are unknown. We have followed reactions between tertiary amines and P(CN) by NMR, which shows many different chemical species as the reaction proceeds, but no crystalline compounds were isolated until P(CN) was combined with the bidentate amine 4-diazabicyclo[2.2.2]octane (dabco) From this system we isolated both 1:1 and 1:2 adducts of P(CN) with dabco
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