Coupling constants of triphenyltin compounds

Coupling constants of triphenyltin compounds

Spectrochimica ACID. Vol. 40A. No. 7. pp. 607-8, Prmted in Great Britain. 1984 0 Coupling constants of triphenyltin 0584&8539/84 $3.00 + 0.00 1984...

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Spectrochimica ACID. Vol. 40A. No. 7. pp. 607-8, Prmted in Great Britain.

1984 0

Coupling constants

of triphenyltin

0584&8539/84 $3.00 + 0.00 1984 Pergamon Press Ltd.

compounds

P. C. SRIVASTAVA and S. K. SRIVASTAVA Department of Chemistry, Lucknow University, Lucknow-226007, India (Received 2

Nouember

1983)

(orfho)for Ph,SnX (X = Cl, I, NCO, NCS, N,) have been theoreticallycalculated and it is found that they are in close agreement with the corresponding observed values of the coupling constants. There exists a linear correlation between the theoretical and experimental coupling constants and electronegativity on the Pauling scale (x,) of X and xx,,,, -xpx. Abstract-3JSnCCH

VERDNOCK

and VAN DER KELEN [l] were the first to report the experimental values of coupling constants of three phenyltin compounds. Since then no attempt has been made in this direction because of the appearance of the two multiplets in the aromatic region; the lower field multiplet corresponding to the ortho phenyl protons and the higher field multiplet corresponding to meta and para phenyl protons [2] and poor resolution of the spectra, often offering less resolved Sn satellite bands corresponding to 3JSnCCH (ortho) (three bond coupling between Sn metal and ortho protons of the phenyl ring), half of which is masked by m-and p- protons multiplet, and sometimes precluding the overall appearance. In the present study 3JSn119CCH(o) of Ph,SnX (X = Cl, I, NCO, NCS and N3) have been theoretically calculated on the basis of the relationship of SCHERR and OLWER[~] with minor modification; and it is seen that there is reasonable agreement between theoretical and experimental values of 3JSn1 19CCH(o). Further, there exists a linear correlation between 3JSn1 19CCH(o) and electronegativity on the Pauling scale (xp) of X and Cxp,,, - xp,. EXPERIMENTAL

Ph,SnX (X = Cl, I, NCO, NCS, N3) [47] were prepared by the reported methods and ‘H NMR spectra were run in CDCI, using TMS as internal standard on a Varian A60D NMR spcctrophotometer. RESULTS AND

DISCUSSION

Theoretical treatment

same hybridization by including the electronegativity term (Ax) where Ax = cxA - cxB; cxA = sum of the electronegativities of the groups attached to the metal in the corresponding derivatives (R3 MX) whose J is to be calculated, cxB = sum of the electronegativities of the groups attached to the metal in the parent compound (R4 M). The theoretical calculation of 3JSnCCH(o) for Ph4Sn and Ph,SnX (X = Cl, I, NCO, NCS and N3) is done as follows. Calculation of3JSnCCH(o)for

coupling between the atoms Sn and H) of Ph,Sn has been calculated knowing that J$,, Sn and J$!$Sn are - 90.34 and - 182.62 Hz [9], respectively (the electronegativities of Ph (2.49)[10] and vinyl (2.41)[10] are very close and data of tetravinyltin and tetraphenyltin are comparable). The calculations are based on J&, Hg and J$z Hg and Jvic Hg corresponding to 159.5, 29.64 and 126.57 Hz, respectively [ 111. Since the values are small, the values of A and B constants are calculated in the following manner without using the least squares method Jam’-Sn -

SCHERR and OLIVER[~] developed the empirical relationship for calculating the J of several organometals of type R,M from the data of RkM’

Sn

‘4 = J;“n”ys VInYIHg - J:l;s,,, J$S,,, Hg = -92.18 = ~ 136.9

J XH= AJ,,+B where J,, is the coupling constant between proton and metal atom X in question, in the present study Sn, J,, is the corresponding coupling constant obtained where Y is any other metal substituted for X and A and B are empirical constants. We believe that since J depends mainly upon (i) hybridization and (ii) electronegativity of the groups attached to the metal [8a], this relationship could be exploited to calculate the coupling constants of other derivatives having the

Ph4Sn

-

182.62 + 90.34 296.4 - 159.5

= 0.6733.

The value of B is the additive constant which would bring A times J:‘;s,,, Hg into agreement with J’,‘;“,,,Sn B = J’,i”,,l Sn - A J&,1 Hg

‘JSnCCH(o)

= -90.34+0.6733

x 159.5 = 17.05. (2)

= - 0.6733 x J&

+ B

= - 0.6733 x 126.57 + 17.05 = - 85.22 + 17.05 = - 68.17. 607

P. C.

608

SRIVASTAVAand S.

K.

SRIVASTAVA

Table 1. Theoretical and experimental values of 35SnCCH(o) for Ph,SnX

Ph,SnCI Ph,Snl* Ph,SnNCO* Ph,SnNCS Ph,SnN,

AX

Theoretical

Experimental

0.46 0.03 1.97

61.11 68.14 66.20 66.49 66.24

66.00 66.00 66.00 66.00 66.60

1.68 1.93

XPJW

C%,

2.95 [8b] 2.52[8b] 4.46 4.17 4.42

- XP,

4.52 4.95 3.01 3.30 3.05

(i) Electronegativity on Pauling scale [lo] Ph, 2.49; vinyl, 2.41. *(ii) The spectra of compounds are at 60 MHz, the rest are at 90 MHz. (iii) The position of the peaks is at the approximate centre of the multiplet.

On the basis of the arguments presented by KREBS and DREESKAMP[~] one can safely assume that the absolute signs of all the metal proton coupling constants are positive, hence 3JSn119CCH(o) for Ph,Sn is 68.17 Hz. By the subtraction of Ax (Table 1) from the value of J for Ph,Sn thevalues of 3JSnCCH(o) for Ph,SnX (X = Cl, I, NCO, NCS and N3) are obtained. The theoretical and experimental values are listed in Table 1. A representative spectrogram of Ph,SnNCS is shown in Fig. 1. Further, the plot of theoretical and experimental

-c

vr 64 n’ t

Fig. 3. Exp. (A) and theo. ( o)~ J SnlL9 CCH(o) of Ph,SnX (X = Cl, 1, NCO, NCS, N,) vs X,,, -X, I 3JSn1’9CCH(o) of Ph,SnX (X = Cl, I, NCO, NCS and N3) vs xp of X and xxp,,, - cxp, (Figs 2 and 3) is linear. Although the calculations are crude because the ring current effect which would also affect the values of J has not been taken into account, there is reasonably good agreement between the theoretical and experimental values of J and such calculations have, for the first time, been done on phenyltin compounds and would form the basis of several other such phenyl metal compounds. A~~nowledgemenrs-Thanks are due to the Head of the Chemistry Department for laboratory facilities and to the Director of C.D.R.I. for spectral analyses. S.K.S. is grateful to C.S.I.R. for P.D.F.

I IO

I 9

I 8

I

7

i

6

ppm (8)

Fig. I. ‘H NMR spectrum of Ph3 Sn NCS.

Fig. 2. Exp. (A)and theo. (0) 3jSn”9 CCH(o) of Ph,SnX (X = Cl, I, NCO, NCS, N,) vs xp

REFERENCES [1] L. VERDNOCKand G. P. VAN DER KELEN, Bull. Sot. chim. Be/g. 174, 361 (1965). [2] W. C. SAU, L. A. CARPINOand R. R. HOLMES, J. organomet. Chem. 197, 181 (1980). [3] P. A. SCHERRand J. P. OLIVER,J. Am. them. Sot. 94, 8026 (1972). [4] R. K. INGHAM,S. D. ROSENBERG and H. GILMAN,Chem. Ret;. 60, 459 (1960). [5] A. S. Mu~~~and R. C. Po~~~~,J.chem.Soc. 5055 (1965). [6] J. H. HOLLOWAY, G. P. MCQUILLANand D. S. Ross, J. them. Sot. A 1935 (1971). [7] J. S. THAYERand R. WEST,Inorg. Chem. 3, 406 (1964). [8] J. E. HUHEEY,Inorganic Chemistry, (a) p. 407, (b) pp. 162-163. Harper and Row, London (1978). [9] P. KREBSand H. DREESKAMP,Spectrochim. Acta 25A, 1399 (1969). [lo] J. E. HUHEEY,J. phys. Chem. 70, 2086 (1966). [ll] K. HILDENBRAND and H. DREESKAMP,Z. phys. Chem. Fran/d Ausa. 69. 171 (19701.