J. prakt. Chem. 337 (1995) 242-244

Journal fur praktische Chemie Chemiker-Zeitung 0 Johann Ambrosius Barth 1995

Solution 13C and 119Sn NMR Spectroscopic Investigations on Triorganotin Deriva- tives of Isothiazol-3(2H)-one 1,l-dioxides and Their Adducts with 0-Donor Ligands

Jens Klein, Barbel Schulze and Rolf Borsdorf Leipzig, Department of Chemistry, University

Seik Weng Ng Kuala Lumpur, Institute of Advanced Studies, University of Malaya

Received August 29th, 1994 respectively October loth, 1994

Organotin derivatives containing acid hydrogen atoms such as carboxylic acids, alcohols or thiols are easily available accor- ding to the following equation using toluene or benzene as solvents [2].

2 R - X - H + R $ h - O - S n R 3 -2R-X-SnR3fHzO x = o , s , o - C ( 0 )

Triorganotin derivatives containing Sn-N bonds such as tri- organotin amides are not typically synthesized by condensing the triorganotin hydroxide or the bis(triorgan0tin)oxide with an amine, but we have been able to synthesize serveral 2- triorganostannyl derivatives of the imino acid saccharine (1,2- benzisothiazol-3(2H)-onel ,l-dioxide) and related compounds [l, 2, 31. The synthesis arise from the acidity of the imino acids [4].

The use of %n NMR spectroscopy for structural and coordination state studies of organotin compounds is well es- tablished [l, 2, 31. '19Sn NMR chemical shifts are effected by a number of parameters. The main factor appear to be the coordination number of tin and the electronegativity of the groups attached to it. Changes in coordination number can often lead to shifts in 6(119Sn) of several hundred ppm. Approximate ranges are [5]:

+200 to -60 pprn -90 to -330 pprn -125 to -515 ppm

for four coordination, for five coordination and for six coordination.

Apart from chemical shifts, '19Sn-13C coupling constants in- crease distinctly with coordination number [l]. Changes in the coordination number of organotin compounds containing polar substituents can arise from complexation with donor molecules, such as solvent molecules, or from self-association 12, 61.

'19Sn NMR spectra

l19Sn chemical shifts of compounds la-le, 2 and 4 were found between -90.0 and -107.0 ppm (Table 1). Replacement of the phenyl groups by n-butyl substituents in compound 3 causes

Table 1 lI9Sn chemical shifts and "J (Sn, C) coupling con- stants for 4,s-substituted 2-triphenylstannyl, isothiazol-3(2H)- one 1,l-dioxides (l), for triphenylstannyl 1,2-benzisothiazol- 3(2H)-onyl-2-acetate 1,l-dioxide (Z), for 2-tributylstannyl 1,2-benzisothiazol-3(2H)-one 1,l-dioxide (3) and for 2-tri- phenylstannyl 1,2-benzisothiazol-3 (2H)-one 1,l-dioxide (4), 6 (l19Sn) relative to tetramethylstannan, solvent: CDC13

indi- concen- 8(ll9Sn) 'J(Sn,C) 'J(Sn,C) 3J(Sn,C) 4J(Sn,C) ces tration [ppm] [Hz] [Hz] [Hz] [Hz]

[mol/i]

l a 0.2 l b 0.2 l c 0.1 Id 0.1 l e 0.05 2 0.2 3 0.2 4 0.12

-105.9 -102.8 -103.8 -107.0 -106.8 -90.0

100.6 -102.9

48.5 640.1 48.6 642.4 47.8

47.3 640.9 48.1 643.8 38.8 343.3 18.3 640.1 49.6

64.1 13.7 65.1 13.2 64.3 13.2 65.6 12.2 64.1 13.0 64.1 12.2 68.7 65.5 13.7

the l19Sn NMR chemical shift to move markedly downfield to 100.6 ppm. This is well known from literature and can be explained by a p,d,-interaction of sp2 hybrid orbitals of the ipso-C-atom of the phenyl group and the d-orbitals of tin

Triorganotin compounds containing electronegative sub- stituents have a strong tendency to autoassociate in the solid state and in concentrated solution [2,6]. This is exemplified by chemical shift - concentratiyn studies of several triorganotin compounds in CDC13 solufion. Higher concentrations lead to upfield changes in chemical shift due to self association of monomeric organotin molecules forming five coordinate oligomers or polymers that are known to exist in the solid state [2]. The resulting equilibrium between four and higher coordinate species makes it possible only to determine an average value for 6(119Sn) which is shifted in the direc- tion of the four coordinate species for dilute solutions in non - coordinating solvents such as CDC13. This behaviour was observed for compounds 1, 2, 3 and 4. Therefore we

17, 81.

J. Klein et al., 13C and ‘19Sn NMR Spectroscopic Investigations 243

L = Lisand 3 4

interprete the values of the chemical shifts in Table 1 in terms of the equilibrium described above.

Structure of the autoassociated complexes

The structure of the autoassociated complexes was investi- gated for several organotin compounds. In the case of tri-

organotin carboxylates, the association occurs through car- boxylate bridging. Triorganotin fluorides and chlorides asso- ciate via halogen bridges [2, 61. In N-(trimethylstannyl) suc- cinimide, which is a compound very similar to our ones, co- ordination of the carbonyl group of the succinimid to the trimethyltin moiety could be demonstrated [9].

Attachment of the tin atom to the carbonyl oxygen should move the carbonyl resonances to lower field. This effect was observed for the carbonyl carbon C(3) in la-le, 3 and 4 (Ta- ble 2 and 3). 6(13C) shows a significant downfield shift of 4.5-5.9 ppm in comparison with the underivated isothiazol- 3(2H)-one-l,l-dioxide [lo, 111. On the other hand, an in- tramolecular coordination of the tin atom with oxygen from the carbonyl group in the same molecule should be ruled out due to the strain effect of the four - membered rings [12]. Therefore we conclude from this 13C NMR data that there is an intermolecular coordination between the tin atom and the carbonyl oxygen of the adjacent molecule in the asso- ciates. A further coordination of tin to the S02-group, as it was pointed out by crystal structure analysis of la, cannot be excluded [13].

Adducts with 0-donor ligands

The formation of 1 : 1 adducts of triphenylstannyl 1,2- benzisothiazol-3(2H)-one 1,l-dioxide (4) with 0-donor lig- ands and the investigation of the solution of these organo- tin adducts 4a4f in a non - coordinating solvent leads to the results given in Table 4. In comparison with S(l19Sn) of 2-triphenylstannyl 1,2-benzisothiazol-3(2H)-one 1,l-dioxide

Table 2 13C chemical shifts of 4,s-substituted 2-triphenylstannyl isothiazol-3 (2H)-one 1,l-dioxides (la-le), 6 (13C) relative to tetramethylsilane, solvent: CDC13

~ ~ ~

indices C(3) C(4) C(5) CH3, CH2 and aromatic C ~ ~ ~ ~

C(i)’ C(o)’ C(m)’ C(p)’

la 168.7 133.0 147.5 8.3(R1)/9.0(R2) 134.8 137.2 129.2 130.8 l b 166.8 119.2 156.0 125.3(Ci)/128.2(C~)/129.4(C~)/132.2(Cp) 134.9 137.2 129.5 130.8 l c 168.6 132.3 148.6 126.2(C~)/129.0(C~)/129.1(C,)/130.9(Cp)/10.3(R1) 134.9 137.3 129.3 130.8 Id 168.0 134.9 150.9 19.2/20.3/20.7120.8 135.3 137.2 129.1 130.7 l e 168.4 135.0 152.3 23.9/24.5/25.6/26.4/9.7 138.1 137.1 129.1 130.6

Table 3 13C chemical shifts for triphenyltin 1,2-benzisothiazol-3(2H)-onyl-2-acetate 1,l-dioxid (2), 2-tributylstannyl benzisothia- zol-3(2H)-one 1,l-dioxide (3), 2-triphenylstannyl benzisothiazol-3(2H)-one 1,l-dioxide (4) and its adducts with 0-donor ligands (4a-4f), S(13C) relative to tetramethylsilane, solvent: CDC13

indices C(3) C(3a) C(7a) C(4) C(5) C(6) C(7) other C(i)’ C(o)’ c(m)’ C(p)’

2 158.5 127.3 137.8 125.3 134.3 134.9 121.1 39.6(CH2)/170.9(C= 3 166.3 129.6 142.3 124.6 134.0 134.0 120.7 4 166.3 129.5 142.6 124.9 133.5 134.3 120.8 4a 166.5 129.3 142.8 ) 124.8 133.4 134.1 120.7 4b 168.6 128.7 144.1 123.8 132.0 132.3 120.1 4c 167.2 130.2 143.2 124.4 132.9 133.4 120.5 4d 166.5 129.4 142.8 124.8 133.3 134.1 120.7 4e 167.2 131.2 143.2 124.3 132.8 133.3 120.4 4f-4 166.4 129.3 142.8 124.8 133.4 134.1 120.7

=O) 137.2 136.7 129.0 130.4 15.5 27.9 27.0 13.6 134.9 137.3 129.2 130.8 136.0 137.2 129.1 130.5 137.3 136.8 128.4 129.1 138.8 137.1 128.8 129.9 136.2 137.1 129.1 130.5 138.5 136.9 128.7 129.8 135.9 137.2 129.2 130.6

a) A second carbonyl resonance (156.1 ppm) can be assigned to the keto group of the diphenylcyclopropenone ligand. Therefore and because of the similaritv of the 6 1l3C113\1 in cnmnariqnn with the nthw rnmnnnndc W P rnnnnt rnnfirm the p y i c t p n r p nf a n

244 J. prakt. Chem. 337 (1995)

Table 4 '19Sn chemical shifts and "J (Sn, C) coupling constants for 2-triphenylstannyl 1,2-benzisothiazol-3 (2H)-one 1,l-dioxide adducts with 0-donor ligands (4a-4f), S (l19Sn) relative to tetramethylstannan, solvent: CDC13

L(indices) concentration S (Il9Sn) 'J (Sn, C) 2J (Sn, C) 3J (Sn, C) 4J (Sn, C) [mol/l] [PPml [Hzl [Hzl [Hzl [Hzl

~

N,N-dimethylformamide (4a) 0.12 -131.1 669.9 48.8 65.6 13.7 triphenylarsine oxide (4b) 0.12 -275.4 47.3 70.2 triphenylphosphine oxide (4c) 0.12 -185.5 744.7 47.3 69.1 14.3 dibenzylsulfoxide (4d) 0.12 -132.4 644.0 47.3 65.6 quinoline N-oxide (4e) 0.12 -198.5 747.7 45.8 67.1 diphenylcyclopropenone (4f) 0.12 -125.4 665.3 47.3 67.1

(4) the Il9Sn chemical shifts of these adducts move approxi- mately 100 ppm upfield, consistent with the formation of a five coordinate trigonal bipyramidal structure at tin that is known from X-ray studies and suggested by 119mSn Mossbauer spec- troscopic investigations to exist in the solid state [13, 141. These upfield shifts depend on the donor ability of the ligand. The largest effects were caused by Lewis bases, triphenyl- arsine oxide 4b, quinoline N-oxide 4e and triphenylphos- phineoxide 4c. Other ligands such as N,N-dimethylformamide 4a, dibenzylsulf oxide 4d and diphenylcyclopropenone 4f showed a weaker 0-donor ability and therefore leaded to smaller changes in S(ll9Sn).

The same can be concluded from ll9Sn-I3C coupling con- stants of the adducts (Table 4). Compared to 4 we observed distinct increase of about 100 Hz in the 'J(l19Sn, 13C) coup- ling constants of the 1:l adducts of the strong Lewis bases. The changes in lJ('19Sn, 13C) are attributed to the respective change in the s-character of the Sn-C bond [15, 161.

Experimental

Il9Sn and 13C NMR spectra were recorded on a "Varian Unity 4 0 0 spectrometer. The measuring temperature was 26°C and CDC13 was used as a non coordinating solvent. Because of the dependence of the l19Sn chemical shift on concentration, '19Sn NMR spectra were measured using de- fined concentrations given in Tables 1 and 4.

Il9Sn NMR spectra were obtained at 149.157 MHz using the following measurement parameters: acquisition time = 0.486 ms, spectral width = 80000 Hz, number of data points = 68032, pulse width (90") = 40 ps. 13C NMR spectra were carried out at 100.577 MHz applying: acquisition time = 0.640 ms, spectral width = 25000 Hz, number of data points = 32000, pulse width (90") = 15 ps.

l19Sn chemical shifts are quoted relative to tetramethyl- stannan (0 ppm). The 13C chemical shifts are given relative to TMS. In order to suppress the reduction in signal intensity due to the negative value of the NOE factor in '19Sn NMR, an inverse gated decoupling technique was used.

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Address for correspondence: Prof. Dr. B. Schulze Fakultat fur Chemie und Mineralogie Institut fur Organische Chemie der Universitat Leipzig Talstralje 35 D-04103 Leipzig, Germany