56 NMR Characterization of Homologous Cyclic Phosphoramides 1
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J A C K E. R I C H M A N , R O B E R T B. F L A Y , and O. D. G U P T A Department of Chemistry, University of Idaho, Moscow, ID 83843
2
In 1974 a DuPont patent disclosed the synthesis of cyclen phosphine oxide, 2, by hydrolysis of cyclen fluorophosphorane, 1. 3
In this paper we wish to report the synthesis of a series of compounds (structure 4) that are higher homologues of 2. Oxides 4 have been synthesized by hydrolysis of the corresponding ionic chloride s a l t s , 3, which we previously reported. 4
(Curved lines i n structures 3 and 4 represent ethylene or methylene bridges.)
tri-
Oxides 4 i n each case are v o l a t i l e compounds that have an intense molecular ion i n their mass spectra. P NMR studies have been useful i n characterizing these compounds as phosphine oxides. Physical and NMR properties of structures 4 are collected in the Table. 31
0097-6156/81/0171-0271$05.00/0 © 1981 American Chemical Society In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
represent
(2) (8) (7) (5) (2) (6)
150-160/0.1 120/0.03 140-150/0.05 125-135/0.05 140/0.07 145/0.07
b.p./pressure (°C/Torr)
bridge sequence i n s t r u c t u r e 4.
12 13 14 14 15 16
Peripheral Ring S i z e β 215-lT 37.5-40 132-136 144-147 100-103 136-139
m.p. (°C) d e
+23.8 24.5 25.8 25.9
12.2 11.7
15.2
P Chemical S h i f t 5,5 5,6 6,6
+40.5 /
3 1
hygroscopic.
The hydrate melts ca. 180° with p a r t i a l decomposi
fA minor peak a t +40 ppm my represent a small amount of the 5,5-fused isomer i n a d d i t i o n to the5,6and 6,6-fused isomers.
s h i f t s obtained a t -52°, see text.
footnote 3.
^Chemical
^See
tion.
^Cyclen phosphine oxide i s extremely
3 1
P chemical s h i f t s i n CDCl^ a r e p o s i t i v e i n downfield d i r e c t i o n from the r e f e r e n c e , e x t e r n a l 85% H^PO^. Numbers represent the s m a l l e r r i n g s s i z e s w i t h i n which phosphorus i s fused.
Numbers
^
a
2.2.2.2 2.2.2.3 2,2,3,3 2,3,2,3 2,3,3,3 3,3,3,3
a
P h y s i c a l and Spectroscopic Data f o r 4.
structure
Table:
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X
H
00
§
X m
Π
oo
C
ta
X ο
oo
Ο
*3
K>
to -J
56.
RiCHMAN E T AL.
Homologous
Cyclic
Phosphoramides
273
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Two of the oxides, 5 and 6, shown i n the Table can exist i n only one structural form.
Both 5 and 6 show only one phosphorus NMR signal at +25.8 and +11.7 ppm, respectively, similar to the shift of hexamethylphosphoric triamide, δ +23.4. The higher f i e l d chemical s h i f t of 6 compared to 5 i s consistent with the effect of bond angle changes at phosphorus which for 5 and 6 are located at bridgehead p o s i tions of fused 5,6- and 6,6-membered rings. The other members of the series of oxides shown i n the Table exhibit structural isomers and i n each case show two or more P NMR signals. The assignments of chemical shifts i n the Table to the various i s o meric forms are analogous to the shifts of 5 and 6 and are consis tent with the expected effects of angle changes at phosphorus fused i n rings of different s i z e s . The chemical shifts change about 15 ppm to higher f i e l d on expansion from fused 5,5- to 5,6and 5,6- to 6,6-membered rings. This is comparable to the trends observed previously for analogous polycyclic compounds containing tetravalent and pentavalent phosphorus atoms. 5
6
31
4
7
The assignments for the 2,2,3,3 isomer, 7, are shown below.
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
PHOSPHORUS CHEMISTRY
274
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The s t a t i s t i c a l d i s t r i b u t i o n o f isomers la> b and c would be 1:2:1. The near absence o f isomer ^7a i n d i c a t e s unfavorable thermodynamic s t a b i l i t y f o r the phosphorus fused i n two f i v e membered r i n g s compared to 5,6- and 6,6-fusion. Greater s t a b i l i t y f o r the l a r g e r r i n g f u s i o n i s a l s o e x h i b i t e d f o r compounds
