Phosphorus Chemistry - American Chemical Society

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119 19

31

13

1H, F, P, and C NMR Investigation of Diphosphanes and Triphosphanes

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J. P. ALBRAND and C. TAÏEB Laboratoire de Chimie LA CNRS N° 321, Département de Recherche Fondamentale, Centre d'Études Nucléaires de Grenoble, 85 X, F.38041 Grenoble Cédex, France

Despite recent progress in the study of the stereochemistry of tetraalkyl or aryl diphosphanes ( 1 , 2 , 3 ) , there is much uncer­ tainty in the definition of the preferred torsional angle, Φbet­ ween the lone pairs on phosphorus atoms and there is l i t t l e exper­ imental evidence to assert the presence or absence of the trans conformation in the liquid phase (4,5). We present here N.M.R. re­ sults obtained from two particular classes of diphosphanes, 1,2disubstituted diphosphanes (RPH) (R = CH3, CH3CH2, c-C6H11, C6H5, CF3) and CF3 substituted diphosphanes (CF3PX) (X = CH3, CN, Br, I) for which very few data are available in the literature (11). 1,2 dialkyl or diaryldiphosphanes, easily accessible through the equilibrium nRPH2 + (RP)n n(RPH)2 (6), are interesting for stereochemical studies because they exist under both themesoand d,l modifications. The variation in the steric requirement of hy­ drogen and the R groups can result in changes in the rotamer popu­ lation, detectable by their influence on the N.M.R. parameters 1J(PP), 2J(PH), 3J(HH) and Ν(PC) = 1J(PC) + J(PC). Compounds of the type (CF3PX) can be obtained through a cou­ pling reaction between Hg and CFQPXI or through the equilibrium nCFoPXo + (CFaP)n n(CF^PX)o (8,9) formally analogous to the one used to obtain the (RPH) derivatives. They also exist under the mdMO and d,t modifications and can provide information on the influence of electronegative groups on the conformation, through the measurement of 1J(PP) and 3j(P,CF3). 2

2

2

2

2

Results With decoupling of the nuclei in the R groups, the *H and ~**P spectra of (RPH) diphosphanes are simple AA'XX* patterns which give readily access to J ( P H ) , j(PH) (with their relative signs), J ( P P ) and ^J(HH). The signs of lj(PP) and J ( H H ) were related to the positive sign of ^J(PH) by double resonance experiments in the cases of ( C ^ P H ^ and (CF3PH) (40. In all the other compounds of Table 1, J ( P P ) and 3J(HH) can be reasonably assumed negative and positive respectively. In the cases of ( C ^ ^ P H ^ and (C-C5H1 ]PH) 2

1

2

1

3

2

1

2

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© 1981 American Chemical Society Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

578

PHOSPHORUS CHEMISTRY

where a s e l e c t i v e d e c o u p l i n g o f t h e a l k y l p r o t o n s i s n o t p o s s i b l e , J ( P H ) , 2 J ( P H ) and J ( Ρ Ρ ) were o b t a i n e d f r o m t h e s p a c i n g s b e t w e e n the c e n t e r o f the w e l l separated m u l t i p l e t s i n the l p spectrum and J ( Η Η ) was o b t a i n e d f r o m t h e p r o t o n s p e c t r u m . 1

1

3

3

Table I :

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R

δ

„ „ ( a ) mUO b

S

d,l

3

3 1

Ρ

6

6

CF C F

b

+ 12.6

-191.5

+4.8

.3.»

+ 10.0

-190.8

+ 11.7

15.0

+189.4

+ 11.2

167.1

5.6

6.9

+ 191.

+8.5

167.1

10.4

6.5

+192.9

+ 1 1.2

185.1

3.5

4.4

+192.9

+6.5

179.1

+192.5

+ 12.2

181.7

2.9

+191.3

+4.3

182.2

9.3

+205.6

+3.2

-135.2

+9.2

3

+213.9

+ 15.2

-183.7

+3.0

9

a) D a t a

Ν (PC)

+206.0

8 6

1 1

J(HH)

+208.2

" -89.7

n

3

*J(PP)

-67.6

-99.6

c-C H

J(PH)

-71.2

"«-β

5

2

*J(PH)

-117.

C H 2

Ρ C h e m i c a l s h i f t s (ppm f r o m Η3ΡΟ4) and s p i n c o u ­ p l i n g p a r a m e t e r s (Hz) i n R ( H ) P P ( H ) R d i p h o s p h a n e s .

" °* -92.

3

0 i s o m e r f o r t h e &iavtt> c o n f o r m a t i o n ( 4 ) . Similar differences exist l u s t r a t e d i n Table I I . Table I I :

X

CH

Br

3 1

!

J(PP)

5

J(FF)

δ Ρ

-45.9

-90.3

54.

-46.3

-92.

55.5

7.3

-184

-53. 1

-22.

58.

13.5

173

2

-54.7

-29.9

59.

19.5

226

2

-47.

-57. 1

68.

12.5

163.

2

-48.1

-52.9

68.5

17.

192.5

2.3

178+5

-

—

—

3 1

2

J(PCF )

J(PCF )

and

6 F

-

-53.4 -55. 1 -47.9

I

3

as i l ­

3

3

17.

-135

-

0

3

CN

diphosphanes

2

F, P C h e m i c a l s h i f t s (ppm f r o m CFCI3 H3PO4) and c o u p l i n g c o n s t a n t s (Hz) i n CF^(X)PP(X)CFo diphosphanes.

1 9

1 9

H

f o r other ( C F 3 P X )

-51.0

N(PF)

=

71.7

N(PF)

=

86.

N(PF)

=

60.3

183+5

N(PF)

=

70.3

211+10

-

The v a l u e s i n T a b l e I I were o b t a i n e d by a n a l y s i s o f t h e A 3 A ' 3 XX s p i n s y s t e m o b s e r v e d i n t h e * P and spectra, using {^F} ^ F h o m o n u c l e a r INDOR e x p e r i m e n t s . The d i s p e r s i o n i n t h e »J(PP) v a l u e s i s p r o b a b l y due t o a more i m p o r t a n t c o n t r i b u t i o n o f t h e t/ιαηΔ c o n f o r m a t i o n t o t h e c o n f o r m a t i o n a l p o p u l a t i o n s i n t h e m&AO and d,t i s o m e r s . The J ( P C F 3 ) v a l u e s show a l s o m a r k e d d i f f e r e n c e s b e t w e e n t h e m£40 and t h e d,t i s o m e r b u t t h e y w i l l be d i f f i c u l t t o u s e as a s t e r e o c h e m i c a l p r o b e as l o n g as t h e r e i s no r e l i a b l e way to i d e n t i f y t h e s e i s o m e r s . 1

3

1

3

Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

580

PHOSPHORUS CHEMISTRY The d e c o m p o s i t i o n o f p u r e ( C H 3 P H )

2

and ( C H 5 P H ) , a s t h a t 2

2

o b s e r v e d f o r ( C f c H c P H ^ (10)» p r o d u c e s t r i p h o s p h a n e s w h i c h c a n be c h a r a c t e r i z e d b y 31 ρ N.M.R. 31 Table I I I :

Ρ C h e m i c a l s h i f t (ppm f r o m H3PO4) and c o u p l i n g c o n s t a n t s (Hz) i n R(H)PP(R)P(H)R t r i p h o s p h a n e s .

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Isomer 1 : ABC CH

-86.6

3: A B

-79

1 : ABC

-71.2

2

C H 2

5

P

2

-93.2

-83.5

2: A B 2

3

δ

6

P

J

3

1

J

2

-102.5

+209.7

+202.3 +198.2 +193.5

-97.2

-97.2

+198.2

-101.2

-101.2

+"193.5

-72.8

-76.8

+"219.3

+205.1

2: A B

-66.9

-81.4

-81.4

+"200.2

+200.2

3: A B

-73.6

-70.4

-70.4

+201.1

+201.1

2

2

J

13

23

±49.9

+42.0

I n t h e t h r e o - e r y t h r o isomer 1 of C H ( H ) P P ( C H 5 ) P ( H ) C H 5 , J ( P P ) v a r i e s b e t w e e n +40 and +20 Hz i n t h e t e m p e r a t u r e r a n g e -40°C/-120°C. T h i s v a r i a t i o n p r o b a b l y r e s u l t s f r o m a change i n t h e r e l a t i o n s h i p o f t h e l o n e p a i r s on t h e 1-3 p h o s p h o r u s atoms. 2

2

5

2

2

A c k n o w l e d g m e n t s : We a r e i n d e b t e d t o D r s . R.C. D o b b i e and P.D. G o s l i n g ( U n i v e r s i t y o f N e w c a s t l e upon T y n e , U.K.) who p r o v i d e d u s w i t h samples o f t h e ( C F P X ) d i p h o s p h a n e s . 3

2

Literature cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Aime, S.; Harris, R.K.; McVicker, E.M. J.C.S. Dalton 1976, 2144. McFarlane, H.C.E.; McFarlane, W.; Nash, J.A. J.C.S. Dalton 1980, 240. Ali, A.A.M.; Bocelli, G.; Harris, R.K. J.C.S. Dalton 1980,638. Albrand, J.P.; Robert, J . B . ; Goldwhite, H. Tetrahedron Letters 1976, 949. Bard, J.R.; Sandoval, A.A.; Wurrey, C . J . ; Durig, J.R. Inorg. Chem. 1978, 17, 286. Albrand, J.P.; Gagnaire, D. J . Am. Chem. Soc. 1972, 94, 8630. Albrand, J.P.; Robert, J.B. J.C.S. Chem. Comm. 1976, 876. Dobbie, R.C.; Gosling, P.D. J.C.S. Chem. Comm. 1975, 585. Dobbie, R.C.; Gosling, P.D.; Straughan, B.P. J.C.S. Dalton 1975, 2369. Baud1er, M.; Koch, D.; Carlsohn, B. Chem. Ber. 1978, 111, 1217. Kang, D.K. ; Servis, K.L. ; Burg, A.B. Org. Mag. Res. 1971, 3, 101.

RECEIVED

June 30, 1981.

Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.