Synthetic, Characterization and Decomposition Studies of Indium Sulfide Precursors
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Me 2 N
MeO
i-Pr i-Pr i-Pr
Ar
Me Ar"A"
RESULTS AND DISCUSSION Indium Compounds The homoleptic indium benzene thiolato compound forms a sulfide bridged polymer[6c] which can be broken up by the addition of a donor solvent such as pyridine. The homoleptic indium thiolate In(SAr')3 (1) was prepared by the reaction of indium metal with the bulky diaryl disulfide (Ar'SSAr') over 3 days in toluene heated to reflux (eq. 1). This method is analogous to that published by Tuck et al.[7] for the reaction of indium metal with diphenyl disulfide with the exception that reaction times are longer for the bulky Ar'SSAr'. By filtering off unreacted metal and removing the solvent under reduced pressure, a yellow oil is obtained that is stable to air and moisture. Selected characterization data is in Table I. The reversible addition of the donor solvents tetrahydrofuran (THF) and acetonitrile (MeCN) allowed the isolation of the compound as a white crystalline solid and its structural determination using X-ray diffraction techniques. The two 97 Mat. Res. Soc. Symp. Proc. Vol. 410 ©1996 Materials Research Society
structures, (Figs. 1 & 2), differ in the number of coordinated solvent molecules and the orientation of the thiolate ligands. The THF adduct can best be described as a three leg pedestal which holds a THF molecule. This structure resembles that of In(SAr*)3 (Ar* = 2,4,6-t-BuC6H 2 ), which has a pseudo propellar shape, whereby the indium atom lies slightly out of the plane described by the three sulfur atoms. One notable difference in this structure and that for compound 1*THF is that, for the latter, the ligands are turned away from the donor solvent molecule. The acetonitrile adduct contains two donor solvent molecules in the apical positions of a trigonal bipyramidal coordination geometry. One aryl ring is close to the plane described by the three sulfur atoms and the other two are on opposite sides of that plane.
3 ArSSAf + 2Ir
Toluene A,3 days
2 In(SAr') 3
Figure 1. ORTEP representation of In(SAr') 3 .THF
98
(1)
Figure 2. ORTEP representation of In(SAM)y2MeCN The thermal decomposition of 1 has been carried out by thermolysis of both solid state and decalin solution samples. The TGA data for 1.2MeCN is shown in Figure 3. The coordinated solvent molecules are removed near the boiling point of the solvent. Once the solvent has been removed, it is expected that intermolecular dative bonds between sulfur and indium form. A clean decomposition occurs to a final weight which corresponds to the calculated weight for In 2 S3. Equation 2 describes the expected decomposition products. The solution decomposition of 1 in boiling decalin over a three hour period was followed by a GC/MS analysis of the solution. The
products found were approximately 80% Ar'SSAr' and 20% Ar'SH.
2 In(SR)3
A
(2)
- In 2 S3 + 3 RSR
Table I: Characterization Data for Compounds 1-3 Compound
Description
In(SAr') 3 (1)
yellow oil
[In(SAr') 3 ]2 (2)
yellow crystals
In(SAr'")3 (3)
yellow crystals
m2. *C
1
H NMR(6)
MS(M+)
1.17(d), 1.2
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