Reactions of Triphenylphosphinimines with Boron ... - ACS Publications

2 Reactions of Triphenylphosphinimines with Boron Compounds, Certain Organometals, and Lewis Acids HANSZIMMERandGURDIALSINGH

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on January 9, 2017 | http://pubs.acs.org Publication Date: January 1, 1964 | doi: 10.1021/ba-1964-0042.ch002

Department

of Chemistry, University of Cincinnati, Cincinnati 21, Ohio

When triphenylphosphinalkylimines reacted with BF , BPh , Me SnCl , and Ph SnCl , a new class of complexes containing a B - N or Sn-N bond was obtained. The boron complexes have the general structure θ P h Ρ = Ν - R, where 3

3

2

2

2

2

3

θ'BX Χ = F and Ph; R = Me, Et, iso-Pr, and tert -Bu. Their stability depended upon R. The com position of the corresponding Sn compounds corresponded to a 1 to 1 addition complex. The exact structure of these compounds is still under investigation. 3

Ρ ecently Zimmer and Singh reported ontheR'X addition to triphenylphosphinalkylimines (2). This reaction proceeded according to the following scheme: φ

[Ph P=N-R3

θ

•PhgP-N-R]

+ R'X

• [PhgP-NRR'^X

8

where R'=Me and Et; R=Me, Et, η - P r , iso-Pr, iso-Bu, and ter*-Bu

In all other cases investigated (R =w-Pr, iso-Pr, and tert-Bu) an elimination reaction occurred and alkylaminotriphenylphosphonium salts were obtained: 1

[Ph P-NRH] ® Χ 3

Θ

This reaction pointed to the fact that these triphenylphosphinalkyl imines are strongly basic in nature. A s a consequence a program was initiated to investigate their reactivity toward different Lewis acids. The results obtained so far are reported here. While this work was in progress, a paper (1) appeared in which the preparation and some reactions with B F and B P h of the parent compound, Ph P=NH,were reported. These results are in agreement with our findings. 3

Reactions

with BF

3

3

3

and BPh

z

These reactions involving B F and B P h are extremely sensitive toward moisture. In the case of B F the reaction proceeded as follows: 3

3

3

17

Niedenzu; Boron-Nitrogen Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1964.

18

ADVANCES

IN

C H E M I S T R Y SERIES

Ph P=N-R 3

BF, 3/ anhydrous

V~3 moisturex

? 3 Ph P=N-R 9

F

3

[Ph PNHR]

e


3

BF

4

G

The compounds prepared are compiled in Tables I and Π. T A B L E I.

Triphenylphos-

Ph — Ρ = Ν - R Ph'" Μ. P., °C.

2 5 CH(CH ) C

Yield,

a

R

H

3

C(CH ) 3

2

3

Formula

%

224-26

b

100

242-43

b

100

C

19 18 H

B F

3

N P

C

H

20 20

B F

3

N P

B F

3

N P

240&

93.8

C

181-82

21 22

64.0

C

22 24

H

H

B F

3

N P C

Uncorrected. ^ Recrystallized from acetone. If suction was applied, this compound dissociated into Ph -P=N-ter£-Bu

0

3

and BFg.

It decomposed slowly under atmospheric pressure,

con

sequently no analysis was made.

T A B L E Π.

AlkylaminotriphenylphosPh Ph—Ρ p

R

M.

P.,

h

"

ά

Yield

Formula

°C. CH

3

2 5 CH(CH ) C

H

3

C(CH ) 3

a

3

2

BF θ

- Ν

125-26

a

88.0

C

19 19 H

B F

4

N P

129-31

a

92.3

C

20 21 H

B F

4

N P

151-52

a

85.5

C

H

21 23

B F

4

N P

74.7

C

22 25

B F

4

N P

169

a

H

Recrystallized from chloroform-ethyl acetate mixture. Niedenzu; Boron-Nitrogen Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1964.


2

ZIMMER AND

SINGH

Triphenyl Phosphinimine

Reactions

19

The methyl and ethyl homologs of type A compounds proved to be very stable toward air. The isopropyl homolog decomposes slowly, but is stable enough to be analyzed. However, the tert -butyl homolog is extremely unstable toward moisture. On exposure to air it decom poses within a few minutes to yield the corresponding type Β compound (see Table Π). Obviously because of steric hindrance the N-B bond is very weak in this case, because upon application of suction to triphenylphosphine-ieri-butyliminitrifluoroboronBFg disappeared and the parent triphenylphosphinalkylimine remained. Type A and Β compounds were identified by checking C, H, and Ν analyses. Infrared spectroscopy could also be used advantageously for this purpose. A l l type Β com pounds exhibited a sharp absorption peak between 3240 and 3260 cm." , corresponding to a N-H stretching frequency. This absorption was distinctly absent from the type A compounds. 1

phinalkyliminetrifluoroboron

Carbon,

%

Hydrogen,

%

Nitrogen,

%

Calcd.

Found

Calcd.

Found

Calcd.

Found

62.75

62.75

5.02

5.01

3.90

3.91

64.40

64.34

5.38

5.38

3.75

3.59

65.17

64.47

5.13

5.13

phonium Tetrafluoroborate

Carbon, % Calcd. Found

Hydrogen, % Calcd. Found

Nitrogen, % Calcd. Found

60.19

60.10

5.02

5.38

3.70

3.90

61.12

60.54

5.34

5.36

3.56

3 91

61.96

61.43

5.65

5.61

3.44

3.74

62.74

62.85

5.94

6.23

3.33

3.39


ADVANCES

20

IN


T A B L E m.

M. P., °C.

Yield %

155-56(dec.)

92.9

147-48(dec.)

88.0

170-72 (dec.)

82.8

149-51(dec.)

81.0

R C H

2 5 CH(CH ) C


3 H

3

C(CH ) 3

a

2

3

Triphenylphos

Formula C

37 33 H

B N P

C

38 35 H

B N P

C

H

39 37

B N P

C

40 39

B N P

H

These compounds gave low (about 1 to 2%) C and H analyses, indicating oxygen uptake. The nature of these oxidation products is being investigated.

The reaction between triphenylboron and triphenylphosphinalkylimines also is sensitive toward moisture. If the reaction was not carried out under strictly anhydrous conditions, oils and sticky materials which defied work-up were isolated. Under anhydrous con ditions the desired 1 to 1 complexes were obtained (Table m). These compounds could not be recrystallized. They were purified by tritur ation with anhydrous ether. Reactions

with

R SnCl 2

2

Triphenylphosphinemethylimine reacted with dimethyltin dichloride and triphenylphosphinethylimine reacted with diphenyltin dichloride. After refluxing for a few hours in ether the resulting precipitate was collected. In either case analyses showed the compound to be a 1 to 1 addition compound. Two structures satisfy the analytical data of these compounds: Φ

Ph P 0

-

3

R

f

Ν -

ι

SnCl

R

Ph P

ft

Q

CI

and

C 1

8 1 1 ( 1

R = R = Me R = Et; R = Ph

= Ν - R

3

1

R 2 !

θ S n C 1

2

f

f

D

At present no experimental evidence to support either structure is available. However, since tin compounds with a coordination number of 5, as required by structure D, are very rare, structure C is the most likely one. The same argument can be applied for the structure of the second compound of this series. Further work on these and similar compounds is in progress. Experimental Melting points are uncorrected. Microanalyses were done by A . Bernhardt, Mikroanalytisches Laboratorium, Max Planck-Institut, Mulheim/Ruhr, Germany, and Galbraith Laboratories, Knoxville21, Tenn. Niedenzu; Boron-Nitrogen Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1964.

2

ZIMMER

AND

SINGH

Triphenyl Phosphinimine

Reactions

21

phinalkylimintriphenylboron p

h

^

θ Ρη Β

3

Ph — Ρ = Ν - R Ph^ ©


Carbon,

%

Hydrogen,

6.62

2.63

2.68

-

-

2.56

2.15

2.50

1.99

_

_

2.44

2,29

Calcd.

83.33

83.37

6.20

_

-

a

% Found

Found

a

Nitrogen, Calcd.

Calcd. a

% Found

Triphenylphosphinalkylimine-Trifluoroboron Complexes. The ap propriate triphenylphosphinalkylimine (0.01 mole) was dissolved in Nadried ether (300 ml.) and B F gas (after drying over P 0 ) was passed through at a rate of two to three bubbles per second at - 7 2 C . A N atmosphere was maintained throughout and the reaction mixture was slowly stirred. When the precipitation stopped, passage of B F was terminated and the mixture was stirred vigorously for half an hour. The precipitate was collected through suction filtration under a nitrogen atmosphere, then dried in vacuum over P 0 . Analytical samples were prepared by dissolving the compound in acetone. A small amount of insoluble residue was filtered off; the compound was recovered by precipitating it by adding dry ether. Triphenylphosphinalkylimine-Triphenylboron Complexes. In a three-necked flask, thoroughly flushed with dry nitrogen and fitted with a stirrer and a dropping funnel, a solution of triphenylboron (1. 21 grams, 0.005 mole) in Na-dried ether (200 ml.) was cooled to ice bath temperature and a solution of the corresponding phosphinimine (slightly more than the equivalent amount) was added dropwise, while being stirred. After the addition was complete (£ hour), the reaction mixture was refluxed and stirred for 5 more hours. A grayish pre cipitate which separated out was collected by suction filtration. It was triturated thoroughly with dry ether (containing a few drops of dry ethanol) to obtain the analytical samples. Triphenylphosphinemethylimine-Dimethyltin Dichloride Adduct. Dimethyltin dichloride (2.197 grams, 0.01 mole) was suspended in 20 ml. of Na-dried ether. A small excess of triphenylphosphinemethylimine in 50 ml. of ether was added and it was refluxed for 2 hours. The resulting white precipitate was filtered, dried, and recrystallized from a mixture of chloroform and ether (m.p. 156-57°; yield 98%). Analysis. Calculated for C H Cl NPSn: C, 49.34; H, 4. 70; CI, 13.90. Found: C, 48.82; H, 4.96; CI, 13.41. Triphenylphosphinethylimine-Dlphenyltin Dichloride Adduct This compound was analogously obtained from diphenyltin dichloride (1. 72 3

2

5

e

2

3

2

2 1

2 4

5

2


22

ADVANCES

IN


grams; 0.0005 mole) and triphenylphosphinethylimine [yield 88%; m.p. 127-29 (from chloroform-ether)]. Analysis.Calculated for C 3 2 H C l N P S n : CI, 10.95. Found: CI, 11.26 30

Literature

2

Cited


(1) Appel, R., Vogt, F., Ber. 95, 2225 (1962). (2) Zimmer, Hans, Singh, Gurdial, J. Org. Chem. 28, 483 (1963); and earlier literature references. Received May 16, 1963. Work supported by financial aid of the U.S. Army through grant DAARO-D-31124-C122.


Reactions of Triphenylphosphinimines with Boron ... - ACS Publications

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