Reactions of lithium bis(trimethylsilyl)amide with some phosphoryl chlorides

INORG. NUCL. CHEM. LETTERS Vol.14, pp. 497-499 © P e r g a m o n Press Ltd. 1978. Printed in Great Britain

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REACTIONS OF LITHIUM BIS(TRIMETHYLSILYL)AMIDE WITH SOME PHOSPHORYL CHLORIDES Jeffery Butvinik and Robert H. Neilson*(1) Paul M. Gross Chemical Laboratory Duke University Durham, North Carolina 27706

(Received 7 August 1978; received for publication 2 October 1978) Introduction Recent work in our laboratory (2) and elsewhere (3) has shown that suitably constructed N-silylphosphinimines

(eq i) are useful precursors to both cyclic and polymeric phosphazenes.

Other compounds of this type where X=OSiMe 3 are readily accessible via the reaction (eq 2) of lithium bis(trimethylsilyl)amide with phosphoryl chlorides (4). Me3SiN=PXRR'

(Me3Si)2NLi

+

--

A

~

Me3SiX

R2P(O)C1

-LiCI

--

+

I/n(NPRR') n

(i)

~ Me3SiN=PR2OSiMe 3

(2)

As part of a systematic investigation of the potential utility of these N,O-bis(trimethylsilyl)phosphinimines

in phosphazene synthesis, we report here our attempts to prepare additional

compounds with a wider variety of phosphorus substituents. Results and Discussion In several attempts to repeat the synthesis of Me3SiNPCI2OSiMe 3 (4,5) according to eq 2, a second higher-boiling product was obtained in low yield. under somewhat different reaction conditions, isolable in 50% yield.

Further investigation revealed that,

this "by-product" became the major product

Analytical and spectroscopic data confirm the structure to be that of

the tetrasilylated compound ~ resulting from a 2:1 rather than a i:i reaction stoichiometry (eq 3).

SiMe 2(Me3Si)2NLi

+

p(O)Cl 3

-2LiCl

(Me3Si)2N_~=NSiMe3

(3)

C1 %1 In contrast, the reactions of LiN(SiMe3) 2 with phosphoryl chlorides containing Ph and/or NMe 2 substituents were found to follow a i:I stoichiometry

(eq 4) but purification and complete

characterization was prevented by their thermal instability.

These compounds were obtained

only in crude form as yellow liquids and were identified by their NMR spectra (TABLE).

Two

trimethylsilyl signals are observed for each compound indicating that they exist as the phosphinimine isomers (4) rather than as the bis(trimethylsilyl)aminophosphine

oxides.

Upon standing at room temperature for several hours or upon attempted distillation, compounds ~-~ underwent thermal decomposition yielding volatile products and orange-brown solid residues.

Infrared and IH NMR analysis showed that the volatile products consisted of

Me3SiOSiMe 3 (from ~, 4' and ~), Me3SiCI

(from ~ and 4), and a third unidentified Me3Si497

498

Reactions of Bis(trimethylsilyl)amide

containing compound (not Me3SiNMe2, from 4). NMR spectra.

The residual solids gave uninterpretably complex

Clearly, since they cannot be purified and since their decomposition reactions

proceed with elimination of more than one silyl compound, the phosphinimines 2-4 are not useful phosphazene precursors.

The fact that these materials do eliminate Me3SiOSiMe 3,

however, indicates that the thermolysis of other N,O-bis(trimethylsilyl)phosphinimines merits further investigation. X (Me3Si)2NLi

+

CIP(O)XY

-LiCI

l Me3SiN=~-OS~Me 3 Y ~:

X=Ph,

t:

X=NNe2, Y=C1

(4)

Y=CI

4 : X=NMe 2, Y=Ph

TABLE Some NMR Spectroscopic Data for Silylphosphinimines, Me3SINP(OSiMe3)XY X

(Me3Si)2N

Y

Signal Obsvd

~(IH)' JPH

~(13C)' JPC

CI

Me3SiN

O.12

3.31, 5.13

Me3SiO

0.37

1.59, 1.83

0.37

4.47, 2.81

(Me3Si)2N Ph

NMe 2

NMe 2

CI

CI

Ph

Me3SiN

0.27

2.97, 5.13

Me3SiO

O.41

1.16, 1.71

Me3SiN

0.16

Me3SiO

0.33

Me2N

2.59, 12

Me3SiN

0.20

Me3SiO

0.47

Me2N

2.37, 15

The preparation of the dimethylamino-substituted compounds ~ and ~ was also complicated by an apparent complex formation between (Me3Si)2NLi and Me2NP(O)XCI (X=CI, Ph).

These

reactions gave unstable, sparingly soluble solid products whose IH NMR spectra contained (Me3Si)2N singlets and Me2N doublets in approximately 3:1 intensity ratios.

Alternatively,

when carried out in the presence of the complexing agent TMEDA (tetramethylethylenediamine)

to

enhance the reactivity of the amide anion, the reactions proceeded as described above affording compounds ~ and ~. Experimental Materials and General Procedures. and used without further purification:

The following were obtained from commercial sources P(O)CI3, PI~(O)CI2, (Me3Si)2NH, TMEDA, and n-BuLi

Reactions of Bis(trimethylsilyl)amide

(hexane solution).

499

The dimethylamino derivatives Me2NP(O)CI 2 and Me2NP(O)PhCI,

identified by

IH NMR data (6), were prepared in yields of 69 and 89%, respectively, by the addition of Me3SiNMe 2 to an equimolar amount of the appropriate phosphoryl chloride at O°C folilowed by fractional distillation. All reactions and other manipulations were carried out under an atmosphere of dry nitrogen.

Proton NMR spectra (of CH2CI 2 solutions) and 13C N-MR spectra (of CDCI 3 solutions)

were recorded on JEOL MH-IO0 and FX-60 spectrometers. a Perkin-Elmer 297 spectrophotometer.

Infrared sFectra were recorded on

Elemental analyses were performed by the Schwarzkopf

Microanalytical Laboratory, Woodside, N. Y. Preparation of P-Bis (trimethylsilyl)amino-P-chloro-N-trimethylsil~l-P-trimethvlsiloxvp_hosphinimine (i).

In a typical preparation, P(O)CI 3 (50 mmol) wss added via syringe to a

stirred solution of LiN(SiMe3)2, prepared f om (Me3Si)2NH (I00 mm¢.l) and n-BuLl (i]O retool), in Et20 (225 ml) at O°C. for several hours.

The mixture was then allowed to warm to room temperature and was stirred

After filtration and solvent removal, distillation afforded 1 as a color-

less liquid ([O.ig, 50% yield, bp 82-86°C/O.O3 Tort). mol wt, 399 (cryoscopic, C6H6). (neat liquid): 655m, 645w cm

Calcd:

Found:

C, 35.98; H, 9.04; C[, 8.50;

C, 35.75; H, 9.00; CI, 8.79; mol wt, 403.

IR spectrum

295Om, 29OOm, 134Ovs, 1255s, 103Os, 98Os, 89Os, 840vs, 76Om, 75Om, 69Om, 670m,

--1

Preparation of N,O-Bis(trimethylsilyl>phosphinimines

(2, 3, and 4).

Using the same

procedure as that described for the synthesis of compound i, PhP(O)CI 2 (50 mmol) was allowed to react with LiN(SiMe3) 2 (50 mmol) in Et20 (200 ml) at O°C.

Filtration and solvent removal left

2 as a yellow liquid which decomposed on attempted distillation. Similarly, ~ and 4 were obtained as unstable yellow liquids but, as described above, in these cases it was necessary to add an equimolar quantity of TMEDA to the LiN(SiMe3) 2 solution prior to addition of the phosphoryl halide. Acknowledgment The authors thank the United States Army Research Office, the Duke University Research Council, and the donors of the Petroleum Research Fund, administered by the American Chemical Society, for generous financial support. References and Notes (i)

Present address:

(2)

P. Wisian-Neilson, R. H. Neilson, and A. H. Cowley, Inor$. Chem., 16, 1460 (1977).

Texas

Department of Chemistry, Texas Christian University, Fort Worth,

76129.

(3)

Von E.-P. Flindt and H. Rose, Z. Anorg. AIIg. Chem., 428, 204 (1977).

(4)

R. H. Neilson, R. D. Jacobs, R. W. Scheirman, and J. C. Wilburn, Inorg. Chem., 17,

(5)

G. Czieslik, G. Flaskerud, R. HSfer, and O. Glemser, Chem. Ber., 106, 399 (1973).

(6)

J. F. Nixon and R. Schmutzler, Spectrochim. Acta, 22, 565 (1966).

1880 (1978).