Unusual Phosphoryl Donor Properties of OP(MeNCH2CH2)3N

The title compound ( 4 ) in which transannular bridgehead−bridgehead bonding is absent, reacts with phosphoryl and silyl chlorides to give the isolable salts [ZOP(MeNCH 2 CH 2 ) 3 N]Cl where Z = Ph 2 P(O), 6 (Cl); PhP(O)Cl, 7 (Cl); 1 / 2 PhP(O), 8 (Cl); MeSiCl 2, 14 (Cl); and SiCl 3, 15 (Cl). Spectroscopic evidence for [ROP(MeNCH 2 CH 2 ) 3 N] + cations, where R = H, 16; Me, 17; Et, 18, and the isolation of the regioisomeric cations [O P(MeNCH 2 CH 2 ) 3 NR] + (R = Me, 19; Et, 20; n -Pr, 21; n -Bu, 22 ) as their iodide salts is also reported. In the presence of Cl 3 PO, PCl 5, or SOCl 2, 4 gives the [ClP(MeNCH 2 CH 2 ) 3 N] + cation ( 26 ) which is also formed when P(MeNCH 2 CH 2 ) 3 N is oxidized with C 2 Cl 6 . The more sterically hindered analogue of 4, namely O P( i -PrNCH 2 CH 2 ) 3 N ( 28 ) (whose synthesis is reported herein), reacts with MeI and EtI to afford the isolable salts [O P( i -PrNCH 2 CH 2 ) 3 NR]I [R = Me, 29 (I); Et, 30 (I)]. Cations 29 and 30 display 1 H and 13 C NMR spectra at room temperature that are consistent with a quaternization-induced rigidity of the cage that renders the (CH 3 ) 2 CH methyl groups inequivalent on the NMR time scale. Acyclic O P(NMe 2 ) 3 reacts with [R 3 O]BF 4 (R = Me, Et) giving the corresponding isolated salts [MeOP(NMe 2 ) 3 ]BF 4 and [EtOP(NMe 2 ) 3 ]BF 4 . Reaction of HCl with O P(NMe 2 ) 3 afforded sublimable (Me 2 N) 3 P O·HCl which represents the first protonated phosphoryl species structured by X-ray crystallography. The transannular bond lengths in 6 (Cl) and 26 (PCl 6 ) [1.948(5) Å and 1.934(8) Å, respectively] are within experimental error of the corresponding link in the [HP(MeNCH 2 CH 2 ) 3 N] + cation [1.967(8) Å].