Geminal 119Sn13C and 119Sn119Sn indirect nuclear spin-spin coupling constants

JOURNAL

OF MAGNETIC

RESONANCE

59, 14 1- 145 ( 1984)

Geminal ‘19Sn-13C and ’ 19Sn-’ 19Sn Indirect Nuclear Spin-Spin Coupling Constants

Institut fir Anorganische Chemie, Universitiit Miinchen, Meiserstrasse 1. D-8000 Munich 2, Federal Republic of Germany Received

January

3 I, 1984

The study of organotin compounds by means of 13C and ‘19Sn NMR provides numerous data on coupling constants and chemical shifts which can be extremely useful for structure assignments. However, the geminal coupling constants 2J(“9Sn’3C) and ‘J( ’ 19Sn’19Sn)have attracted little attention in this respect, although a considerable number of data are available (Z-12). The variation in the magnitude of both types of values of ‘J appears to be unsystematic and, therefore, their use as a structural criterion seems to be questionable. In our own work on trimethyltin compounds (J3, 11, 12) and in the literature (4-20) the values 12J(“9Sn’3C)I and j2J(“9Sn”9Sn)l range from close to zero to ca. 70 Hz and to ca. 1000 Hz, respectively. Of course, a meaningful discussion of these data requires the knowledge of the sign of 2J which, however, has been determined only for a few examples (2, 9-12). We have now determined the sign of 2J(“9Sn’3C) and of 2J(“9Sn”9Sn) in corresponding trimethyl tin compounds (a trimethyl tin group replaces a methyl group and vice versa) which have extreme and intermediate values of ‘J by appropriate heteronuclear double-resonance experiments (13) (Table 1). From these results it appears that the magnitude and sign of both geminal coupling constants are controlled basically by proportionate contributions. Further data for comparison are given in Table 2 and the relationship between 2J(’ 19Sn13C) and 2J(“9Sn”9Sn) is graphically depicted in Fig. 1. As can be seen a linear relationship emerges when one Me$n group is replaced by an alkyl group (usually a methyl group, but in some cases an ethyl or tert-butyl group) in order to compare 2J(“9Sn”9Sn) with 2J(1’9Sn’3C). This correlation rests upon the known signs of 2J(“9Sn’3C) (1, 3, 5, 7, 9, 11, 29) and of 2J(“9Sn”9Sn) (2,10,14). The other signs have been deduced from the correlation in Fig. 1 and in general these assumptions are supported by the known sign of 2J in a similar compound. If the coupling constants are numerically small the sign given in Table 2 represents the best fit with the other data. It is readily seen that knowledge of the sign explains the apparently irregular changes in the magnitude of ‘J, e.g., in the series of (Me3Sn)+,ER,: 141

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142

NOTES TABLE Signs”

No.

of 2J(“9Sn’3C)

and 2J(“9Sn”9Sn)

Me&-SnMe2-CH,

3

Me’Sn. H3C,c’C~Et

in Corresponding

Compounds

Preparation and other NMR data

Compound

1

I

.BEt*

Compound +763d

-56.5’

k

I

-70.0’

112

M

(+)943’

;$~;c=c:;Et 3

+12.2s

n

n

(-)195.4

(Me3Sn)2N-SnMe3

6

Me&. Me 3Sn,N--N(SnMe3)2

8

5

(M~J~)zN--CHI

7

Me,Sfl, H 3C,N--N(SnMed2

+57.0h

0

0

-972’

9

Me,Sn.N-N-CH, H,C’

+47.0’

0

0

-833”

‘SnMe,

No.

MeIS-SnMe2-SnMe3

2 4

2

3

10

a Signs in parentheses are deduced from the relationship in Fig. I, see text. ‘Obtained by multiplication of *J(“%“‘Sn) with &‘gSn)/-y(“7Sn) = 1.0465. ’ In agreement with Ref. (IO); observation of “%.n satellites in the “C spectrum and selective irradiation of ‘H related the signs of *J(“%n’H) (+) and ‘J(“%“C) (-) as well as ?I(“%n’H) (-) and 2J(“PSn’3C) (-); the sign of ‘J(‘%“H) (-) (relative to ‘J(“C’H) (+) was confirmed by ‘H{“%n) experiments, observing differential effects for the “C satellites of the “‘Sn satellites. dAppropriate ‘H{ ‘%n} experiments gave the signs (relative to ‘J(“C’H) (+)) of ‘J(“9Sn”9Sn) (+), 2J(“9Sn”9Sn) (+), *J(‘%n’H) (+) (in both SnMe groups), sJ(SnH) (-). e Selective “C{ ‘H} (“?Sa satellites of the =C”CHs resonance) and ‘H{‘%n} experiments (“C satellites of “%n satellites) gave the signs (relative to ‘J(‘%‘H) (+) of ‘J(“%n’H) (-) and *J(“%n”C) (-). f’J(“9Sn’3C=): 346.1 , 298 .0 Hz. s Selective “C{‘H) (‘%n satellites of the N”CHs resonance) and ‘H{ “%n) experiments (“C satellites of ‘%n satellites) gave the signs (relative to ‘J(‘C’H) (+)) of ‘J(“?%‘H) (-), *J(“%“C) (+), and of 2J(“9Sn”7Sn) (-). hSelective “C{‘H} experiments (“%n satellites of the N”CH* resonance) related the sign of ‘J(“%n’H) (-) and *J(‘%n”C) (+), confirmed by ‘H{ “‘Sn) experiments: observing the “C satellites of the “%n satellites in the fragment “?Sn. N‘H-“CN enabled to correlate

‘J(“C’H)

(+) with *J(“?Sn”C)

(+); furthermore “?$n. ‘H-C,N-N

gave the signs of ‘J(“?Sn’H) fragment

(-),

‘J(“?Sn”‘%n)

experiments

in the fragment

,“%n

(+) and ‘J(‘%n’H)

‘H-C-N-N

‘H{ “%n}

(-);

finally

‘H(“9Sn}

experiments

considering

the

.f”?h .l17Sn

related the signs of ‘J(‘%n’H) (-) and *J(‘%n”‘Sn) (-). ’ Since 2J(““Sn”9Sn) (-) in 10 (833 Hz) is of similar magnitude a negative sign *J(“%n’%n) can be assumed with certainty for 8, furthermore, a negative sign for *J(“9Sn”9Sn) (486 Hz) has been determined for (Me*Sn)*NNMe*. ‘Selective “C( ‘H) experiments (‘%$n satellites ofthe N”CH* resonance) give the signsof’J(“%‘H)(-) and*J(“%“C) (+); ‘H{ ‘%n} experiments in the fragment “%n\ ‘H-C,N-N gave the signs of ‘J(‘%n’H) (-) and ‘J(‘%“‘Sn) * Ref. (IO) and references cited therein. ’ Ref. (4). m G. Menz and B. Wrackmeyer, Z. Naturforsch. ” Ref. (2). o Ref. (3).

,“‘Sn

(+).

B 32. 1400 (1977).

143

NOTES TABLE

Geminal

NO. 11 13 15 17 19 21

23

Compound Me&-CHz-CHs (Me,Sn)2CH-CH,

Me&-CH(Me)-CHs MelSn-CH(Et)-CHs Me&-CMq-CHS Me*Sn(Et)-CHS-CHs /Et

29 31 33 35

(Me,Sn)2Sn(Me)-CH3 (Mes.Sn),Sn-CH,

+2x6< (+)25.0d (+)13.4’ (+)13.2’

(-)287d -309’ (-)162” (-)157d (-)19’ (--)285’

Compound M~&-CHI--S~M~,

(Me&M--CWM,

Me&-S-CHXH,

12 14 16 18 20 22

Me&-CH(Me)-SnMeS Me&-CH(Et)-&Me, Me&-CMe2-SnMq

Me&(CHZ-SnMe&

(-)460.3h

(Me,Sn)zC=C=C,C,BEt,

/Et

Me&’ (-)24.

I’

No.

(MeJ.Sn)2CH--SnMes

‘CHJ

/Et --CH$nMeJ

MeJSn --

(CH,),C’c=c=c

and *J(“%I”~S~)

2J(“9Sn”9Sn)b (Hz)

(+)29.0h

--H

27

*J(“%I’~C)

*J(“9Sn’3C) (Hz)

+O’

(Me,Sn)zC=C=C,C,BEtz

Me& L H,C ,c=c=eMe

Constants’

+24. I 8

Me,&’ 25

Coupling

2

24

‘SnMe

(+)238.0’

(-)31.9h.k

(+)432.4h

-25.0’ (-)9.2” (+)15.3< (+)15.6”

(+)287.0”’ (+)20.0’ (-)195.4< (-)218.2’

3 26

Me,.%.

MeZin’C=C=C’Ef

‘CH2SnMe3

28

(Me&)2Sn(Me)-SnMe,

30

(Me,Sn),Sn-&Me, (Me,Sn)2N-SnMe, Me&--S-&Me3

32 34 36

as See Table 1. ‘Ref. (8); the sign of 2J(“9Sn13C) in 9, 11, 13, 15, 19, 21 is assumed to be the same as in Et&, Ref. (9). ‘Ref. (6). e Ref. (2). ‘Ref. (7). BB. Wrackmeyer, Specfr. Int. J. 1, 201 (1982); the same sign is assumed in Et.,Sn, Ref. (9). ‘Ref. (12). ’ H. G. Kuivila, J. L. Considine, R. J. Mynott, and R. Sarma, J. Organomer. Chem. 55, Cl 1 (1973). ’ Ref. (I). ‘This work; ‘J(“%‘“C=): 452.2. ’ Ref. (4); the sign has been determined in this work. m Ref. (5). “M. E. Bishop, C. D. Schaeffer, Jr., and J. J. Zuckerman, J. Organomet. Chem. 101, Cl9 (1975). o This work, in C,D,.

(Me&r)rE 2J(119Sn119Sn) -325 +20.0 2J(1’9Sn13C) -

(Me3Sn)3EEt

(MeJSn)zEMez

Me$nEMe3

-230 +259 +20 -18.3

-19 +763 +18 -25.0

*0 -56.5

E=C E = Sn E=C E = Sn

In both series of compounds the replacement of Me3Sn groups by alkyl groups gives an increasingly positive contribution to ‘J( ‘19Sn”9Sn) and an increasingly negative contribution to 2J(“9Sn13C). Taking into account the negative sign of ~(r’~Sn) the reduced coupling constants 2K are both affected in the same way.

144

NOTES

+50 t

on0 -5ol

718

.

3%%, ,

-500 FIG. 1. Correlation = -14.2 2J(“9Sn’3C)

0

,

I

I

I

+500

1

I

I

I

.

I

w

+lOOO

between geminal coupling constants 2J(“9Sn’3C) and *J(“%‘%) - 32.0; r = 0.9898); the numbers refer to the compounds in Tables

(2J(“9Sn”9Sn) 1 and 2.

It is noteworthy that regression analysis leads to an improved relationship, omitting the data for the stannyl hydrazines 7 to 10 (2J(“9Sn”9Sn) = -13.2 *2J(“9Sn’3C) - 12.6; r = 0.995). For the hydrazines, the large range of values of 12J(“9Sn”9Sn)l (>500 Hz (3)) indicates strongly that the values of ‘J will be extremely sensitive to the nitrogen lone-pair-lone-pair interactions. These, on the other hand, will depend upon the substituents at the nitrogen atoms. Hence, it follows that the replacement of a methyl group by a trimethyl stannyl group certainly influences these interactions as was shown previously (3). Therefore, we conclude that any large deviation from the linear relationship between 2J(’ 19Sn13C) and 2J(“9Sn”9Sn) in comparable compounds indicates that the introduction of a Me$n group instead of a methyl group creates a markedly differing situation as far as the bond angles at the intervening atom and the distribution of electron density in the remaining part of the molecule is concerned. In this regard we expect further applications of this relationship when more data become available. The compounds studied have been prepared following literature procedures as indicated in Table 1. The NMR spectra at 28 “C were recorded in PFT mode using a Bruker WP 200 spectrometer. Concentrated solution of all compounds in C6Ds (ca. 50-60s v/v) in 5 mm tubes (‘H) and 10 mm tubes (13C, ‘19Sn) were used for the measurements. The ‘H receiver coil was double tuned in order to perform the heteronuclear double-resonance experiments ‘H{ ‘19Sn}. The correct frequencies y(‘H) (for selective 13C{ ‘H} experiments) and v(’ “Sn) (for selective ‘H{ “9Sn) experiments) were accurately determined from ‘H and ‘19Sn spectra, respectively. The correct power level of the ’ 19Sn irradiation frequency was determined in each case for the more

145 abundant species prior to the observation of the differential effects on the r3C satellites of the “9Sn satellites. The latter experiment required ca. 500 to 2000 transients (depending on the number of tin atoms involved) for a reasonable S/N ratio. Since in all cases at least one of the relative signs could be compared with the sign of ‘J(‘3C’H) (which can be regarded as absolutely positive) the signs given in Table 1 are absolute signs. ACKNOWLEDGMENT Support of this work by the Deutsche Forschungsgemeinschaft und by the “Fonds der Chemischen Industrie” is gratefully acknowledged. REFERENCES 1. B. WRACKMEYER, J. Magn. Reson. 39, 359 (1980). 2. W. BIFFAR, T. GASPARIS-EBELING, H. N~TH, W. STORCH, AND B. WRACKMEYER, J. Magn. Reson. 44, 54 (1981). 3. T. GASPARIS-EBELING, H. N~TH, AND B. WRACKMEYER, J. Chem. Sot. Dalton Trans., 97 (1983). 4. T. N. MITCHELL AND G. WALTER, J. Chem. Sot. Perkin Trans. 2, 1842 (1977). 5. T. N. MITCHELL AND M. EL-BEHAIRY, J. Organomet. Chem. 141, 43 (1977). 6. T. N. MITCHELL AND M. EL-BEHAIRY, J. Organomet. Chem. 172,293 (1979). 7. T. N. MITCHELL, A. AMAMRIA, B. FABISCH, H. G. Kum~, T. J. KAROL, AND K. SWAMI, J. Organomet. Chem. 259, 157 (1983). 8. H. G. KUIVILA, J. L. CONSIDINE, R. H. SARMA, AND R. J. MYNOTT, J. Organomet. Chem. 111, 179

(1976). 9. F. 10. W. Il. B. 12. B. 13. W.

J. WEIGERT AND J. D. ROBERTS, J. Am. Chem. Sot. 91, 4940 (1969). MCFARLANE, J. Chem. Sot. A. 1630 (1968). WRACKMEYER, J. Magn. Reson. 42, 287 (1981). WRACKMEYER, J. Organomet. Chem. 205, 1 (1981). MCFARLANE, Ann. Rep. NMR Spectrosc. 1, 135 (1968); 5A, 353 (1972),

and references cited therein.