2,8,9-Tris(2-methylpropyl)-2,5,8,9-tetraaza-1λ⁵-phosphatricyclo[3.3.3.0^1,5]undecan-5-ium chloride dihydrate

Abstract

The asymmetric unit of the title hydrated salt, C18H40N4P+·Cl−·2H2O, consists of two ionic mol­ecules and four water mol­ecules. The mol­ecular geometry around the penta­coordinate P atom is trigonal–bipyramidal, with a H atom and an apical N atom in axial positions and three N atoms with isobutyl substituents in equatorial positions. The Cl− ions and water mol­ecules are connected via O—H⋯Cl hydrogen bonds, forming chains along [100]. The ethyl­ene bridging groups are disordered with refined site-occupancy ratios of 0.578 (9):0.422 (9).

On Transannulation in Azaphosphatranes: Synthesis and Theoretical Analysis

“…Additionally, the average N eq –P–N ax –C dihedral angle (Table ) for 1-F + is 27.9°, while that of the other complexes in the series does not exceed 3°. Similar compression is seen in [HP­( i -BuNCH 2 CH 2 ) 3 N] + . Taken together, these data suggest that decreasing pyramidalization at phosphorus, inward pyramidalization at N ax , and torsion of the ethylene linkers permit increasing transannulation with the most electronegative substituents at phosphorus.…”

“… a B3LYP level of theory with dispersion corrections (B3LYP-D3). b Isobutyl groups are omitted for visual clarity. c See ref . …”

“…The P–N ax interaction in (pro)­azaphosphatranes may be considered a form of pnictogen bond, distinct from the extensively investigated interaction between PR 3 or PR 4 + compounds and ammonia. − We examined four systems of increasing complexity that model the interactions between (X)­PR 3 (+) and an amine (Figure ) to gain a qualitative understanding of the importance of the ethylene linker in promoting donation from N ax to phosphorus in azaphosphatranes.…”