Structural investigations of phosphorus–nitrogen compounds. 7. Relationships between physical properties, electron densities, reaction mechanisms and hydrogen-bonding motifs of N₃P₃Cl_{(6 − n)}(NHBu ^t ) _n derivatives

Abstract

A series of compounds of the N 3 P 3 Cl (6 À n) (NHBu t ) n family (where n = 0, 1, 2, 4 and 6) are presented, and their molecular parameters are related to trends in physical properties, which provides insight into a potential reaction mechanism for nucleophilic substitution. The crystal structures of N 3 P 3 Cl 5 (NHBu t ) and N 3 P 3 Cl 2 (NHBu t ) 4 have been determined at 120 K, and those of N 3 P 3 Cl 6 and N 3 P 3 Cl 4 (NHBu t ) 2 have been redetermined at 120 K. These are compared with the known structure of N 3 P 3 (NHBu t ) 6 studied at 150 K. Trends in molecular parameters [phosphazene ring, P-Cl and P-N(HBu t ) distances, PCl 2 angles, and endo-and exocyclic phosphazene ring parameters] across the series are observed. Hydrogen-bonding motifs are identified, characterized and compared. Both the molecular and the hydrogen-bonding parameters are related to the electron distribution in bonds and the derived basicities of the cyclophosphazene series of compounds. These findings provide evidence for a proposed mechanism for nucleophilic substitution at a phosphorus site bearing a PCl(NHBu t ) group.

trans-2,6-Dichloro-2,4,4,6-tetrakis[methyl(trimethylsilyl)amino]-1,3,5,2λ5,4λ5,6λ5-triazatriphosphorine

“…Many crystal structures of amido derivatives of chlorophosphazenes have been reported (e.g. Polder & Wagner, 1976;Bartlett et al, 2006;Ahmed & Gabe, 1975, Ahmed & Fortier, 1980. Compound (I) is the first trans non-geminal tetrasubstituted derivative of this class of compounds to be structurally characterized (Fig.…”

Synthesis and spectroscopic properties of geminal-bis(tertbutylamino) phosphazenes obtained by the reaction of spiro and ansa phenoxyphosphazenes with the tert-butylamine and the crystal structure of 2,2-[2,2’-metheylenebis(4-chlorophenoxy)]-4,4-bis(tert-butylamino)-6,6-dichlorocyclo- 2λ5,4λ5,6λ5-triphosphazatriene

“…The organic, inorganic or organometallic side groups are highly effective in determining the specific physical or chemical properties of phosphazene polymers. Although the partial and complete aminolysis reactions of tert-butylamine [NH 2 C(CH 3 ) 3 ] were studied 20 to obtain geminal tert-butylamino products, there have not been sufficient studies yet on the partial and complete aminolysis reactions of tert-butylamine for spiro or ansa phosphazene compounds. In the present study, the reaction of 2,4',4',6',6',10-hexachloro--4',4', 6 IR, 1 H-NMR, 13 C-NMR, 31 …”

Nucleophilic substitution reactions of monofunctional nucleophilic reagents with cyclotriphosphazenes containing 2,2-dioxybiphenyl units

“…When electron donating groups are on the N 3 P 3 ring, the positive charge at the phosphor atoms reduce and monofunctional alcohols react almost exclusively by the nongeminal pathway [14]. Reaction of the cyclotriphosphazene core with secondary amines result in predominantly nongeminal substitution, whereas primary amines, such as t-butylamine and aniline, prefer geminal disubstitution due to steric or polar reasons [10,11,13,15]. The geminal pathway is attributed to a rate-determining ionization step prior to attack by the nucleophile (S N 1), while associative substitution (S N 2) is attributed to nongeminal isomeric product formation [10,13] .…”