Synthesis of C-substituted imino-derivatives of germanium, tin and lead

IN()R(L

NLI('L.

('III{M.

i.ICI'TI{RS

V,,I.

7.

pp.

181-185.

1971.

I)ctganam I:Jrc~,s. I ' r i n l c d m (;teal IStitain.

SYNTHESIS OF C-SUBSTITUTED IMINO-D~RIVATIVES OF G~ANIUM,

J. Jappy

and

TIN AND LEAD

P.N. Preston

Department of Chemistry, Heriot-Watt University, Edinburgh, Scotland.

( R e c e i v e d 15 Octob~r 1970)

As part of our continuing interest I in the chemistry of imines bearing organometallic substituents we required compounds of the type (I) in which a fourth main group element is attached to the carbon atom of the imine : Ar~

R I ~ .

III

:~ NR 1

RII/-l~Iv~

R3M/

3

II

I

R I, R II, R III = alkyl or aryl

M = Si, Ge, Sn, Pb.

Although N-substituted imines (II) are well authenticated 2, very little has been reported on the desired compounds:

recently Biran et al. 3 suggested

the intermediacy of a disubstituted imine (I, Ar=Ph; R~-Me;

M:Si;

RI=SiMe3) during the reaction of benzonitrile

with trimethylchlorosilane and magnesium; 1;~1

the preparation

182

IMINO-DERIVATIVES O F GERMANIUM, "FIN AND L E A D

of the hydrazone (I,

Ar=R=Fh; RI=NH2) from the reaction

of benzoyltriphenylsilane with hydrazine has also been

reported h. Our work indicates that compounds of type (I) for Ge, Sn, and Pb only] are readily prepared by allowing a C-substituted chlorimine to react with the appropriate organometallic lithium reagent in tetrahydrofurmn (c_~f. refs. 5 and 6): Ph~N C1/

R + R3ML il

~

Ph\ I I R3M

NR + LiC1

R -- Ph or cyclohexyl R~M = Fn3Ge , Ph3Sn , Ph3Pb , Me3Sn. Unfortunately organosilicon derivatives could not be prepared by this method;

reaction of triphenylsilyllithium with

C-chloro-N-benzylideneaniline or C-chloro-N-benzylidenecyclohexylamine produced red materials of relatively high molecular weight, the structures of which are presently under investigation. The spectroscopic data given in the Table is of interest in connection with the effects of organometallic substltuents On chromopharlc groups ?.

It is noteworthy

that the infrared C=N stretching frequency shifts markedly to lower values for all the organometallic compounds as . compared with organic analogues; the situation therefore parallels that for the carbonyl group in analogous ketones 8 ( ~MCO-

-I , M=Si, Ge, Sn) in which shifts of ca. 70 cm.

Directly analogous organic imines could not be prepared by conventional methods and the ensuing discussion is based on a spectral comparison with hydrogen - and methyl-substituted der ivatives.

Vol. 7, No. 2

Vol. 7, No. 2

I M I N O - D E R I V A T I V E S O F GERMANIUM. TIN AND L E A D

occur in the carbonyl stretching frequency.

The absorption

spectra of the N-aryl substituted organotin and -lead compounds show large bathochromic shifts c~. in the n-~

50 nm.)

transition but a much smaller shift (ca. 18 nm.)

is observed for the germanium derivative;

interestingly the

- ~ transition in both the N-aryl and N-cyclohexyl organometallic compounds is unaffected.

These trends are

also similar to those noted 8 for analogous ketones in which large (ca. IOO nm. ) shifts occur in the n -~ but the . - ~ transition is unaffected. The ~ceptional behaviour of the germanium-substituted imine (which shows o~_y a relatively slight bathochromic shift in the n - ~

transition),

however, is noteworthy, and it is tempting to rationalise these trends on the basis of inductive effects from the metal.

It should be borne in mind, however, that the

origin of the shifts in visible spectra of the ketones has caused some controversy 7'9 and extensive physicochemical studies are required before the true role of the metal can be appreciated (cf. the investigations of Bock et al. I0 on the ketones).

EXP~IMENTAL The organometallic imines were prepared by heating equimolar quantities of the organometallic lithium reagent and the chlorimine under reflux in tetrahydrofuran for I hr.

The solvent was evaporated and the residue extracted

with benzene;

the extract was filtered, evaporated, and the

residual yellow oil chromatographed with benzene eluent through neutral alumina.

P~crystallisation of the eluted

yellow oil from benzene/petroleum ether gave an analytically

183

Ph

cyclohexyl

cyclohexyl

cyclohexyl

Ph3Fo

Me

Me3Sn

Ph3Sn

m.p. /

165/3

80 °

92 o

47 ° 147/0" 5

#"

or b.p.

20

38

36

25 20

30

% yield

1580

1578

1632

1580

1570 1575

1592

1625

1625

C = N stretch (cm-1)

I,R,

#High boiling yellow oils which did not crystallise.

370

364 369

338

320

316(sh)

,. n -~

I- 03 x 103

9"15 x 102 1.16 x 103

1.13 x 103

I "73 x 103

6"73 x 103

300(sh)

318

4"76 x 102

1"73 x 102

246

247

241

260

252 256

240(sh)

245

262

1.63 x 104

9"05 x 103

1.16 x IO 4

2.52 x 104

1-78 x 104 2.14 x 104

1"60 x 104

2"22 x 104

I •71 x 104

U.V. and Visible Spectra (nm) ~ t 2 0 3

masked by ~ - ~ *

Satisfactory analytical data were obtained for new compounds /Melting points are uncc~rected

Ph

Ph

Me3Sn Ph3Sn

Ph

Fn

He

~3Ge

Ph

RI

H

R

R~

Compound Phi_ NR I

TABLE:C - SUBSTITUTED I M I N O - D ~ I V A T I V E S ~ OF G~RMANIUM;TIN AND LEAD

o_

Z

.z

|

O

[]

Z

Vol. 7, No, 2

IMINO-DERIVATIVES O F GERMANIUM, TIN AND L E A D

pure product. The organic imines were prepared by a literature method 11.

REF~ENCES

I.

J. JAPPY and P.N. PRESTON, Tetrahedron Letters, 1157, (1970).

2.

LUI-HEUNG CHAN and E.G. ROCHOW, J.(~ganometal.Chem.,9_~231, (1967)

3.

C. BIRAN, R. CALAS, J. D U N ~ ,

and N. DUFFONT, J. Organometal.Chem.,

557, (197o). 4.

K.O. KAUFM

, B. A[~ATH, P. TRAGER, and K. RUHLMANN, Tetrahedron

Letters, 4937, (I 968 ). 5.

M. BUSGH and F. FALCO, Ber.,43,2557,(1910).

6.

M. BUSCH and M. FLEISCHMANN, Ber.,4_~3255~(1910).

7.

R. WEST, J. Organometal.Chem.,3_~314, (1965).

8.

A.G. BROOK, Adv. Organometal. Chem. 7~ 95, (1968 )

9.

F. AGOLINI, S. KLEMENKO, I.G. CSI~ADIA, and K. YATES, Spectrochim. Acta, Part A,2_~ 169,(1968)

10.

H. BOCK, H. ALT and H. SEIDL, J.Amer.Chem.Soc.,9~1 355, (1969 ).

11.

G. REDDELIEN, Ber., ~ 6 2712, (I 913 ).

185