Unusual Phosphoryl Donor Properties of OP(MeNCH2CH2)3N

1998-09-05T00:00:00Z (GMT) by Xiao-Dong Liu John G. Verkade
The title compound (4) in which transannular bridgehead−bridgehead bonding is absent, reacts with phosphoryl and silyl chlorides to give the isolable salts [ZOP(MeNCH2CH2)3N]Cl where Z = Ph2P(O), 6(Cl); PhP(O)Cl, 7(Cl); 1/2PhP(O), 8(Cl); MeSiCl2, 14(Cl); and SiCl3, 15(Cl). Spectroscopic evidence for [ROP(MeNCH2CH2)3N]+ cations, where R = H, 16; Me, 17; Et, 18, and the isolation of the regioisomeric cations [OP(MeNCH2CH2)3NR]+ (R = Me, 19; Et, 20; n-Pr, 21; n-Bu, 22) as their iodide salts is also reported. In the presence of Cl3PO, PCl5, or SOCl2, 4 gives the [ClP(MeNCH2CH2)3N]+ cation (26) which is also formed when P(MeNCH2CH2)3N is oxidized with C2Cl6. The more sterically hindered analogue of 4, namely OP(i-PrNCH2CH2)3N (28) (whose synthesis is reported herein), reacts with MeI and EtI to afford the isolable salts [OP(i-PrNCH2CH2)3NR]I [R = Me, 29(I); Et, 30(I)]. Cations 29 and 30 display 1H and 13C NMR spectra at room temperature that are consistent with a quaternization-induced rigidity of the cage that renders the (CH3)2CH methyl groups inequivalent on the NMR time scale. Acyclic OP(NMe2)3 reacts with [R3O]BF4 (R = Me, Et) giving the corresponding isolated salts [MeOP(NMe2)3]BF4 and [EtOP(NMe2)3]BF4. Reaction of HCl with OP(NMe2)3 afforded sublimable (Me2N)3PO·HCl which represents the first protonated phosphoryl species structured by X-ray crystallography. The transannular bond lengths in 6(Cl) and 26(PCl6) [1.948(5) Å and 1.934(8) Å, respectively] are within experimental error of the corresponding link in the [HP(MeNCH2CH2)3N]+ cation [1.967(8) Å].