Synthesis and crystal structure of bis(μ-2-methylbenzenethiolato-κ2 S:S)bis[methyl(2-methylbenzenethiolato-κS)indium(III)]

The dinuclear compound, [Me(2-MeC6H4S)In-μ-(2-MeC6H4S)2InMe(2-MeC6H4S)], was prepared from the 1:2 reaction of Me3In and 2-MeC6H4SH in toluene. Its crystal structure exhibits a four-membered In2S2 ring core via bridging (2-MeC6H4S) groups. The dimeric units are further associated into a one-dimensional polymeric structure via intermolecular In⋯S contacts.

The dinuclear title compound, [In 2 (CH 3 ) 2 (C 7 H 7 S) 4 ] or [Me(2-MeC 6 H 4 S)In--(2-MeC 6 H 4 S) 2 InMe(2-MeC 6 H 4 S)], was prepared from the 1:2 reaction of Me 3 In and 2-MeC 6 H 4 SH in toluene. Its crystal structure exhibits a four-membered In 2 S 2 ring core via bridging (2-MeC 6 H 4 S) groups. The dimeric units are further associated into a one-dimensional polymeric structure extending parallel to the a axis via intermolecular InÁ Á ÁS contacts. The In atoms are then in distorted trigonal-bipyramidal CS 4 bonding environments.

Chemical context
Methylindium dithiolates [MeIn(S 2 R)] have been shown to be useful compounds for the ring-opening polymerization (ROP) of cyclic esters to produce biodegradable polymers (Allan et al., 2013;Briand et al., 2016). These compounds are prepared from the stoichiometric reaction of InMe 3 with polydentate amino/oxo-dithiols. However, the 1:2 reaction of triorganylindium (R 3 In) with simple monothiols (R 0 SH) often results in isolation of the diorganylindium thiolate R 2 In(SR 0 ) (Hoffmann, 1988;Nomura et al., 1989). The favourable formation of the organylindium dithiolate RIn(SR 0 ) 2 was reported to be determined by the steric bulk of the thiolate ligand and the R-In group, and the acidity of the thiol reactant. The 1:2 reaction of nBu 3 In or iBu 3 In and PhSH afforded the dithiolate RIn(SPh) 2 (R = nBu, iBu) as solids, although the compounds were poorly soluble in organic solvents, precluding crystallization. All compounds in these studies were primarily characterized by NMR. The only structurally characterized example of such a compound is [(Me 3 Si) 3 C](PhS)In--(PhS) 2 In[C(Me 3 Si) 3 ](SPh), which is prepared from the redox reaction of the indium(I) compound [(Me 3 Si) 3 CIn] 4 and the disulfide (SPh) 2 (Peppe et al., 2009

Database survey
The dinuclear structure of (I) is similar to that of [Me(MeO 2 CCH 2 CH 2 S)In--(MeO 2 CCH 2 CH 2 S) 2 InMe-(MeO 2 CCH 2 CH 2 S)] (Allan et al., 2013). However, the ester carbonyl oxygen atoms of the terminal MeO 2 CCH 2 CH 2 S groups occupy the coordination site trans to the axial bridging thiolate sulfur atom. This precludes intermolecular InÁ Á ÁS bonding and yields discrete dimeric units. The structure of (I) is also similar to that of the structure of dimeric (Peppe et al., 2009). However, the steric bulk of the (Me 3 Si) 3 C precludes further intermolecular InÁ Á ÁS bonding and the indium atoms are restricted to a four-coordinate distorted tetrahedral bonding environment. Other reported methylindium dithiolates employ polydentate dithiolate ligands, some of which possess dimeric and trimeric structures (Briand et al., 2016).

Synthesis and crystallization
2-Methylbenzenethiol (0.300 g, 2.42 mmol) in toluene (2 ml) was added dropwise to a stirred solution of InMe 3 (0.193 g, 1.21 mmol) in toluene (5 ml). The solution was stirred for 18 h and concentrated in vacuo to 4 ml. After sitting at 296 K for 1 d, the solution was filtered to yield colourless, needle-like Part of the crystal structure of (I), with displacement ellipsoids drawn at the 50% probability level. H atoms have been omitted for clarity. [Symmetry codes: (i) À1 + x, y, z; (ii) 1 + x, y, z.]

Special details
Experimental. Crystal decay was monitored by repeating the initial 50 frames at the end of the data collection and analyzing duplicate reflections. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.