Unusual phosphoryl donor properties of O=P(MeNCH2CH2)3N
Date
1998
Authors
Liu, Xiaodong
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Advisor
Verkade, John G.
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Abstract
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 C13PO, PCl5 or SOCl2, 4 gives the [ClP(MeNCH2CH2)N]+ 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 consistent with a rigidity of the cage induced by quaternization that renders the (CH3)2CH methyl groups inequivalent on the NMR time scale. Acyclic O=P(NMe2)3 also 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].
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thesis