Four-bond phosphorus-phosphorus coupling constants have been measured from the 31P NMR spectra of phosphazenylcyclophosphazenes. Their magnitude appears to be related to the conformation adopted by the phosphazenyl-group relative to the phosphazene ring

Biddlestone, Malcolm

Keat, Rodney

Rose, Hans

Rycroft, David S.

Shaw, Robert A.

Chemischer Informationsdienst

English

Enlighten: Publications

N O T I Z E N 1001 
Stereospecific 
Four-Bond Phosphorus-Phosphorus Spin 
Couplings in Phosphazenyl-Phosphazenes 
M. BIDDLESTONE*, R . KEAT**, H . ROSE***, 
D . S. RYCROFT**, a n d R . A . SHAW**** 
* Department of Chemistry, University of Khartoum, 
P. O. Box 321, Khartoum, Sudan. 
** Department of Chemistry, University of Glasgow, 
Glasgow, G12 8 QQ, U. K. 
*** Lehrstuhl für Anorganische Chemie I der Ruhr-
Universität Bochum, D-463 Bochum-Querenburg, 
Postfach 2148, BRD. 
**** Department of Chemistry, Birkbeck College, 
(University of London), Malet Street, London 
WC IE 7HX, U. K. 
(Z. Naturforsch. 31 b, 1001-1002 [1976]; received March 4, 1976) 
31P NMR Spectra, 
Four-Bond Phosphorus-Phosphorus Coupling, 
Conformation, Phosphazenylcyclophosphazenes 
Four-bond phosphorus-phosphorus cou-
pling constants have been measured from the 
31P NMR spectra of phosphazenylcy clophos-
phazenes. Their magnitude appears to be 
related to the conformation adopted by the 
phosphazenyl-group relative to the phos-
phazene ring. 
The two-bond spin-spin coupling constant, 2JPNP 
is well documented1 in both cychc and acyclic 
phosphazenes. However, very few four-bond cou-
pling constants, VP-N-P-N-P, have been reported2. 
Examination of the 3 1P NMR spectra of a series 
of phosphazenyl-derivatives of cyclotriphosphaza-
trienes (1) revealed the presence of 4JP-N-P-N-P. 
Cl\ ^L /N_P0 R3 
ck-|A *KX 
Nsp» 
CK sNy 
The largest coupling (7.5 Hz) was in the trimethyl-
phosphazenyl-derivative ( la) 3 (for numbering see 
Table) and double and triple resonance experiments 
were carried out to estabhsh its relative sign. The 
results are shown in the Figure, where a homo-
nuclear 3 1P{ 3 1P} experiment (carried out under 
conditions of proton noise decoupling) showed that 
«/PA-N-PC and JPA-X-PC-N-PD have the same sign. 
In principle, the same experiment gives the relative 
Requests for reprints should be sent to Dr. R. KEAT, 
Department of Chemistry, University of Glasgow, 
Glasgow, G12 8 QQ, U. K. , or 
Professor R. A. SHAW, Department of Chemistry, 
Birkbeck College, (University of London), Malet 
Street, London, W C 1 E 7HX, U. K . 
lOOHz. 
i l A a . 
J f l l 
Figure. 31P NMR spectra of 1 a (R = Me, X = Y = Cl), 
(a) normal spectrum with complete JH decoupling, 
(b) and (c) as in (a), but with irradiation of Pc signals 
(see text). 
signs of JPC-N-PD a n d ^PA-N-PC-N-PD, hut the PA 
resonance is broad (presumably because of quadru-
polar relaxation of adjoining nitrogen and/or 
chlorine nuclei) and this combined with intensity 
changes, caused by population transfer effects, and 
the weakness of the available phosphorus irradiation 
field 
Y ( 3 1 P)B 2 
2 71 < 4 Hz j meant that interpretable 
effects could not be observed. However, selective 
irradiation of PA and observation of PD showed that 
JPA-N-PC and JPC-N-PD had the same sign. There is 
good reason to believe that JP-N-P will be positive1'4, 
so that the four bond coupling is also positive. This 
was confirmed by examination of the XH spectrum 
of this compound which consists of a doublet of 
doublets: 1H{ 3 1P} double resonance showed that 
JPQ-N-PD and JPC-N-PD-C-H have the same sign and 
that JPC-N-PD and JPD-C-H are of opposite sign, the 
latter generally being found to be negative in 
phosphorus(V) compounds5. Homonuclear 3 1P{ 3 1P} 
experiments on the compounds3-6 listed in the 
Table showed that the four-bond couplings are 
positive, with the exception of that for 1 e where 
«/PA-N-PC-N-PD i s — 0 . 4 H z . 
The hitherto reported P - N - P couplings in cyclo-
phosphazenes are not simply related to the electro-
negativity of the substituents on the phosphorus 
atoms1 and the same generahsation may be made 
for JP a_X-PC and JPA-N-PC-N-PD (Table). For 
example, the four-bond coupling becomes less 
positive in the order X = Cl > OEt > NMe2 > Ph. 
However, there is evidence to suggest that this 
coupling constant is related to the preferred 
conformation adopted by the phosphazenyl-group 
relative to the phosphazene ring. The crystal 
structure of l e 7 shows that the plane containing 
the exocychc P - N - P unit hes perpendicular to the 
plane containing the phosphazene ring (type I I 
conformation8), but in 1 (R = Ph, X = Cl, Y = Cl)9, 
and in 2-fra^-6-N4P4Cl6 (N = PPh3)2 10 , the P h 3 P = 
N-group is rotated by approximately 90° (type I 
Brought to you by | University of Glasgow Library
Authenticated
Download Date | 5/10/17 5:40 PM
1002 N O T I Z E N 
Table. 31P NMR data3, for phosphazenylcyclophosphazenes. 
Compound R X Y <5P*> J P - N - P (Hz)« Jys ' - P - N - P ( H Z ) D 
l a Me Cl Cl A ( = 
C 
D 
B) 20.9 
1.1 
25.4 
P A -
P C -
P C 
• P D 
44.5 
16.0 
P A - • P D ± 7.5e 
lb Ph Cl Cl A ( = 
C 
D 
B) 20.3 
0.2 
15.4 
P A . . . 
P C -
P C 
• P D 
47.5 
27.8 
P A - • P D ± 3.4 
lc Ph OEt Cl A ( = 
C 
D 
B) 18.5 
— 1.6 
13.5 
P A - . 
P C -
• P C 
• P D 
49.5 
39.0 
PA- . . P D + 0.9 
ld Ph NMe2 Cl A ( = 
C 
D 
B) 17.1 
4.3 
13.6 
P A - . 
P C -
• Pc 
• P D 
36.8 
28.4 
I P A - -PDI < 0.1 
le Ph Ph Cl A ( = 
C 
D 
= B) 16.1 
2.9 
14.4 
P A . . 
P C -
• P C 
• P D 
21.9 
5.8 
P A - ..PD — 0 . 4 
1 ! Ph Cl NMe2 A 
B 
C 
D 
21.4 
26.4 
4.4 
14.6 
P A - . 
P A -
P B -
P C 
• P B 
• Pc 
• Pc 
• P D 
42.8 
57.4 
57.0 
26.2 
PA-
PB-
. .PD ± 5.5 
..PD ± 3.3 
2-*r<ms-6-N4P4Cl6(N = PDPh3)2 D 13.8 |Pd-N-P-N-P| 4.6f 
a Obtained on a Varian XL-100 in the C. W . mode at 40.5 MHz in CDCI3 solution at ca. 25°. 
b Relative to 85% H3PO4; low field shifts are positive. 
0 All couplings are positive, ± 0.5 Hz. 
d ± 0 . 1 Hz. 
E < { P D - C - H = — 1 3 . 0 2 H z , J P C - N - P D - ^ H = + 0 . 6 5 H z . 
f Apparent coupling. 
conformation8; see ref.9). Furthermore, basicity 
measurements on a series of phosphazenyl-
cyclophosphazenes indicate that electron supply 
from the Ph3P=N-group to the cyclophosphazene 
ring is more effective in lb and l f than in ld, 1 e or 
l c (at least on protonation). The smaller, or least 
positive, four bond couplings may therefore be 
correllated with a preferred conformation in which 
the plane containing the exocychc P-N-P unit is 
approximately perpendicular to the plane contain-
ing the phosphazene ring. The relatively inefficient 
electron supply to the cyclophosphazene ring in this 
conformation would be consistent with a reduced 
Fermi contact contribution to J P A - N - P C - N - P D - The 
reduction in this coupling is paralleled by a progres-
sive high-field shift for the PA signals. This trend 
in 31P shifts is often obseived with increasing 
chlorine content of aminochlorocyclophosphazenes, 
where the phosphorus atoms become progressively 
more electron deficient. 
It is interesting, but perhaps surprising, in view 
of the observations on JPa_N-PC> to find that the 
positive two bond coupling, JPC-N-PD> 1S linearly 
related to electronegativity parameters for the 
X-substituents in lb - l e . 
R. K . and D. S. R. thank the S. R. C. (U. K.) for 
assistance in the purchase of NMR equipment. 
1 E . G . F I N E R a n d R . K . H A R R I S , P r o g r e s s in N M R 
S p e c t r o s c o p y 6 , 8 6 [ 1 9 7 0 ] ; R . K E A T , R . A . S H A W , 
and M. WOODS, J. Chem. Soc. Dalton, in press. 
2 G . R . F E I S T E L a n d T . M O E L L E R , J . I n o r g . N u c l . 
Chem. 29, 2731 [1967]; M. BIDDLESTONE and R . A. 
S H A W , J . C h e m . Soc . ( A ) 1 9 7 1 , 2 7 1 5 ; H . W . R O E S K Y , 
Chem. Ber. 105, 1439 [1972]. 
3 H . R O S E a n d R . A . S H A W , u n p u b l i s h e d resul ts . 
4 P . C L A R E , D . B . S O W E R B Y , R . K . H A R R I S , a n d 
M. M. WAZEER, J. Chem. Soc. Dalton 1975, 625. 
5 W . McFARLANE, Proc. Rov. Soc. (London) A 306, 
185 [1968]. 
6 M . B I D D L E S T O N E a n d R . A . SHAW , J . C h e m . Soc . 
Dalton 1973, 2740. 
7 M . B I D D L E S T O N E , G . J . B U L L E N , P . E . D A N N , a n d 
R. A. SHAW, Chem. Commun. 1974. 56. 
8 R. A. SHAW, Pure Appl. Chem. 44, 317 [1975]; 
Z . N a t u r f o r s c h . 3 1 b , 6 4 1 [ 1 9 7 6 ] . 
9 Y . S . B A B U , T . S . C A M E R O N , S . S . K R I S H N A M U R T H Y , 
H . M A N O H A R , a n d R . A . S H A W , Z . N a t u r f o r s c h . 3 1 b , 
999 [1976]. 
1 0 G . J . B U L L E N a n d P . E . D A N N , u n p u b l i s h e d results . 
1 1 M . B I D D L E S T O N E , S . N . N A B I , a n d R . A . S H A W , 
J. Chem. Soc. Dalton 1975, 2634. 
Brought to you by | University of Glasgow Library
Authenticated
Download Date | 5/10/17 5:40 PM


Stereospecific four-bond phosphorus-phosphorus spin couplings in phosphazenyl-phosphazenes

Four-bond phosphorus-phosphorus coupling constants have been measured from the 31P NMR spectra of phosphazenylcyclophosphazenes. Their magnitude appears to be related to the conformation adopted by the phosphazenyl-group relative to the phosphazene ring.</jats:p

M. Biddlestone

R. Keat

H. Rose

D. S. Rycroft

R. A. Shaw

Crossref

Zeitschrift für Naturforschung B

Notizen: Stereospecific Four-Bond Phosphorus-Phosphorus Spin Couplings in Phosphazenyl-Phosphazenes

Four-bond phosphorus-phosphorus coupling constants have been measured from the &lt;sup&gt;31&lt;/sup&gt;P NMR spectra of phosphazenylcyclophosphazenes. Their magnitude appears to be related to the conformation adopted by the phosphazenyl-group relative to the phosphazene ring

Enlighten

N O T I Z E N 1001 Stereospecific Four-Bond Phosphorus-Phosphorus Spin Couplings in Phosphazenyl-Phosphazenes M. BIDDLESTONE*, R . KEAT**, H . ROSE***, D . S. RYCROFT**, a n d R . A . SHAW**** * Department of Chemistry, University of Khartoum, P. O. Box 321, Khartoum, Sudan. ** Department of Chemistry, University of Glasgow, Glasgow, G12 8 QQ, U. K. *** Lehrstuhl für Anorganische Chemie I der Ruhr-Universität Bochum, D-463 Bochum-Querenburg, Postfach 2148, BRD. **** Department of Chemistry, Birkbeck College, (University of London), Malet Street, London WC IE 7HX, U. K. (Z. Naturforsch. 31 b, 1001-1002 [1976]; received March 4, 1976) 31P NMR Spectra, Four-Bond Phosphorus-Phosphorus Coupling, Conformation, Phosphazenylcyclophosphazenes Four-bond phosphorus-phosphorus cou-pling constants have been measured from the 31P NMR spectra of phosphazenylcy clophos-phazenes. Their magnitude appears to be related to the conformation adopted by the phosphazenyl-group relative to the phos-phazene ring. The two-bond spin-spin coupling constant, 2JPNP is well documented1 in both cychc and acyclic phosphazenes. However, very few four-bond cou-pling constants, VP-N-P-N-P, have been reported2. Examination of the 3 1P NMR spectra of a series of phosphazenyl-derivatives of cyclotriphosphaza-trienes (1) revealed the presence of 4JP-N-P-N-P. Cl\ ^L /N_P0 R3 ck-|A *KX Nsp» CK sNy The largest coupling (7.5 Hz) was in the trimethyl-phosphazenyl-derivative ( la) 3 (for numbering see Table) and double and triple resonance experiments were carried out to estabhsh its relative sign. The results are shown in the Figure, where a homo-nuclear 3 1P{ 3 1P} experiment (carried out under conditions of proton noise decoupling) showed that «/PA-N-PC and JPA-X-PC-N-PD have the same sign. In principle, the same experiment gives the relative Requests for reprints should be sent to Dr. R. KEAT, Department of Chemistry, University of Glasgow, Glasgow, G12 8 QQ, U. K. , or Professor R. A. SHAW, Department of Chemistry, Birkbeck College, (University of London), Malet Street, London, W C 1 E 7HX, U. K . lOOHz. i l A a . J f l l Figure. 31P NMR spectra of 1 a (R = Me, X = Y = Cl), (a) normal spectrum with complete JH decoupling, (b) and (c) as in (a), but with irradiation of Pc signals (see text). signs of JPC-N-PD a n d ^PA-N-PC-N-PD, hut the PA resonance is broad (presumably because of quadru-polar relaxation of adjoining nitrogen and/or chlorine nuclei) and this combined with intensity changes, caused by population transfer effects, and the weakness of the available phosphorus irradiation field Y ( 3 1 P)B 2 2 71 < 4 Hz j meant that interpretable effects could not be observed. However, selective irradiation of PA and observation of PD showed that JPA-N-PC and JPC-N-PD had the same sign. There is good reason to believe that JP-N-P will be positive1'4, so that the four bond coupling is also positive. This was confirmed by examination of the XH spectrum of this compound which consists of a doublet of doublets: 1H{ 3 1P} double resonance showed that JPQ-N-PD and JPC-N-PD-C-H have the same sign and that JPC-N-PD and JPD-C-H are of opposite sign, the latter generally being found to be negative in phosphorus(V) compounds5. Homonuclear 3 1P{ 3 1P} experiments on the compounds3-6 listed in the Table showed that the four-bond couplings are positive, with the exception of that for 1 e where «/PA-N-PC-N-PD i s — 0 . 4 H z . The hitherto reported P - N - P couplings in cyclo-phosphazenes are not simply related to the electro-negativity of the substituents on the phosphorus atoms1 and the same generahsation may be made for JP a_X-PC and JPA-N-PC-N-PD (Table). For example, the four-bond coupling becomes less positive in the order X = Cl > OEt > NMe2 > Ph. However, there is evidence to suggest that this coupling constant is related to the preferred conformation adopted by the phosphazenyl-group relative to the phosphazene ring. The crystal structure of l e 7 shows that the plane containing the exocychc P - N - P unit hes perpendicular to the plane containing the phosphazene ring (type I I conformation8), but in 1 (R = Ph, X = Cl, Y = Cl)9, and in 2-fra^-6-N4P4Cl6 (N = PPh3)2 10 , the P h 3 P = N-group is rotated by approximately 90° (type I Brought to you by | University of Glasgow LibraryAuthenticatedDownload Date | 5/10/17 5:40 PM1002 N O T I Z E N Table. 31P NMR data3, for phosphazenylcyclophosphazenes. Compound R X Y <5P*> J P - N - P (Hz)« Jys ' - P - N - P ( H Z ) D l a Me Cl Cl A ( = C D B) 20.9 1.1 25.4 P A -P C -P C • P D 44.5 16.0 P A - • P D ± 7.5e lb Ph Cl Cl A ( = C D B) 20.3 0.2 15.4 P A . . . P C -P C • P D 47.5 27.8 P A - • P D ± 3.4 lc Ph OEt Cl A ( = C D B) 18.5 — 1.6 13.5 P A - . P C -• P C • P D 49.5 39.0 PA- . . P D + 0.9 ld Ph NMe2 Cl A ( = C D B) 17.1 4.3 13.6 P A - . P C -• Pc • P D 36.8 28.4 I P A - -PDI < 0.1 le Ph Ph Cl A ( = C D = B) 16.1 2.9 14.4 P A . . P C -• P C • P D 21.9 5.8 P A - ..PD — 0 . 4 1 ! Ph Cl NMe2 A B C D 21.4 26.4 4.4 14.6 P A - . P A -P B -P C • P B • Pc • Pc • P D 42.8 57.4 57.0 26.2 PA-PB-. .PD ± 5.5 ..PD ± 3.3 2-*r<ms-6-N4P4Cl6(N = PDPh3)2 D 13.8 |Pd-N-P-N-P| 4.6f a Obtained on a Varian XL-100 in the C. W . mode at 40.5 MHz in CDCI3 solution at ca. 25°. b Relative to 85% H3PO4; low field shifts are positive. 0 All couplings are positive, ± 0.5 Hz. d ± 0 . 1 Hz. E < { P D - C - H = — 1 3 . 0 2 H z , J P C - N - P D - ^ H = + 0 . 6 5 H z . f Apparent coupling. conformation8; see ref.9). Furthermore, basicity measurements on a series of phosphazenyl-cyclophosphazenes indicate that electron supply from the Ph3P=N-group to the cyclophosphazene ring is more effective in lb and l f than in ld, 1 e or l c (at least on protonation). The smaller, or least positive, four bond couplings may therefore be correllated with a preferred conformation in which the plane containing the exocychc P-N-P unit is approximately perpendicular to the plane contain-ing the phosphazene ring. The relatively inefficient electron supply to the cyclophosphazene ring in this conformation would be consistent with a reduced Fermi contact contribution to J P A - N - P C - N - P D - The reduction in this coupling is paralleled by a progres-sive high-field shift for the PA signals. This trend in 31P shifts is often obseived with increasing chlorine content of aminochlorocyclophosphazenes, where the phosphorus atoms become progressively more electron deficient. It is interesting, but perhaps surprising, in view of the observations on JPa_N-PC> to find that the positive two bond coupling, JPC-N-PD> 1S linearly related to electronegativity parameters for the X-substituents in lb - l e . R. K . and D. S. R. thank the S. R. C. (U. K.) for assistance in the purchase of NMR equipment. 1 E . G . F I N E R a n d R . K . H A R R I S , P r o g r e s s in N M R S p e c t r o s c o p y 6 , 8 6 [ 1 9 7 0 ] ; R . K E A T , R . A . S H A W , and M. WOODS, J. Chem. Soc. Dalton, in press. 2 G . R . F E I S T E L a n d T . M O E L L E R , J . I n o r g . N u c l . Chem. 29, 2731 [1967]; M. BIDDLESTONE and R . A. S H A W , J . C h e m . Soc . ( A ) 1 9 7 1 , 2 7 1 5 ; H . W . R O E S K Y , Chem. Ber. 105, 1439 [1972]. 3 H . R O S E a n d R . A . S H A W , u n p u b l i s h e d resul ts . 4 P . C L A R E , D . B . S O W E R B Y , R . K . H A R R I S , a n d M. M. WAZEER, J. Chem. Soc. Dalton 1975, 625. 5 W . McFARLANE, Proc. Rov. Soc. (London) A 306, 185 [1968]. 6 M . B I D D L E S T O N E a n d R . A . SHAW , J . C h e m . Soc . Dalton 1973, 2740. 7 M . B I D D L E S T O N E , G . J . B U L L E N , P . E . D A N N , a n d R. A. SHAW, Chem. Commun. 1974. 56. 8 R. A. SHAW, Pure Appl. Chem. 44, 317 [1975]; Z . N a t u r f o r s c h . 3 1 b , 6 4 1 [ 1 9 7 6 ] . 9 Y . S . B A B U , T . S . C A M E R O N , S . S . K R I S H N A M U R T H Y , H . M A N O H A R , a n d R . A . S H A W , Z . N a t u r f o r s c h . 3 1 b , 999 [1976]. 1 0 G . J . B U L L E N a n d P . E . D A N N , u n p u b l i s h e d results . 1 1 M . B I D D L E S T O N E , S . N . N A B I , a n d R . A . S H A W , J. Chem. Soc. Dalton 1975, 2634. Brought to you by | University of Glasgow LibraryAuthenticatedDownload Date | 5/10/17 5:40 PM

M. BIDDLESTONE

R. KEAT

H. ROSE

D. S. RYCROFT

R. A. SHAW

ChemInform Abstract: Stereospecific Four-Bond Phosphorus-Phosphorus Spin Couplings in Phosphazenyl- Phosphazenes (I) (NMR-Spektren).

http://www.degruyter.com/downloadpdf/j/znb.1976.31.issue-7/znb-1976-0723/znb-1976-0723.xml

Stereospecific four-bond phosphorus-phosphorus spin couplings in phosphazenyl-phosphazenes

Abstract

Similar works

Full text

Available Versions

Enlighten: Publications

Crossref

Enlighten

Crossref