Tris(2-pyridyl)phosphine oxide: how C—H...O and C—H...N interactions can affect crystal packing efficiency

Abstract

Tris(2-pyridyl)phosphine oxide, (I), C(15)H(12)N(3)OP, is isomorphous with tris(2-pyridyl)phosphine. Because of a combination of C-H.O and C-H.N interactions, the crystal packing is denser in the title compound than in the related compounds triphenylphosphine oxide and tris(2-pyridyl)phosphine.

Dipole moments and conformational analysis of tris(2-pyridyl)phosphine and tris(2-pyridyl)phosphine chalcogenides. Experimental and theoretical study

“…The obtained results are in a good agreement with the data of [19] where the structure of tris(2-pyridyl)phosphine oxide in crystal was studied by the X-ray diffraction. It was established that phosphine oxide 2 has pyramid configuration with propeller arrangement of three pyridyl rings, one of the nitrogen atoms is directed to the oxygen atom of the P = O group, and another two nitrogen atoms are directed to the opposite side that is the conformation of the molecules in the crystal 2 is practically identical to the geometry of conformer 2b.…”

“…Concurrence of the experimental and theoretical values of the bond distances and angles for tris(2-pyridyl)phosphine oxide 2 is very good, especially taking into account the difference between the crystal [19] and gaseous phase. The main conclusion on its conformation is also consistent between the experimental and theoretical values: namely, it is a pyramid with propeller arrangement of the pyridyl cycles, where one of the pyridyl cycles is directed by the nitrogen atom towards the oxygen atom of P = O group, and another two pyridyl cycles are directed to the opposite side.…”

“…According to [21], the structures 3 and 4 are analogous to the tris(2-pyridyl)phosphine oxide [19], they have distorted tetrahedral configuration around the phosphorus atom. In crystal of phosphine sulfide 3 one nitrogen atom is directed towards the sulfur atom, and another two nitrogen atoms are directed to the opposite side.…”

“…5) with too great a dipole moment. The molecules of 3 and 4 in the crystal cells [21] are bonded by the weak hydrogen intermolecular interactions as well as the molecules of 1 and 2 in the crystal state [19]. Structures of 1-4 as generally crystal structures, first of all, are determined by the requirements of crystalline packing.…”

“…It was established that phosphine oxide 2 has pyramid configuration with propeller arrangement of three pyridyl rings, one of the nitrogen atoms is directed to the oxygen atom of the P = O group, and another two nitrogen atoms are directed to the opposite side that is the conformation of the molecules in the crystal 2 is practically identical to the geometry of conformer 2b. The molecules of 2 in crystal are bonded by the weak C-HÁ Á ÁO and C-HÁ Á ÁN intermolecular interactions, and the same C-HÁ Á ÁN interactions exist in tris(2-pyridyl)phosphine 1 [19]. Most likely, these intermolecular interactions in 1 define the high value of its polarity in comparison with the majority of compounds of three-valence phosphorus [12].…”