Antimony(III) dithiocarbamates: Structural studies and exploration of the rare Sb···Sb interaction

Herein, we report synthesis and spectroscopic characterization of a new piperidine-based homoleptic antimony(III) dithiocarbamate complex Sb[S₂CN(CH₂)₄CH(Bn)]₃) (1) and solid state crystal structure of a piperazine-based complex Sb[S₂CN(CH₂)₄N(Bn)]₃ (2). This study identifies molecular and supramolecular features of the two compounds based on single crystal XRD data. Interestingly, complex 1 features an Sb···Sb (stibophilic) linkage, a rarely observed interaction in this class of compounds. To investigate the rarity of this stibophilic linkage CSD retrieved structures have been scrutinized and DFT studies conducted. XRD data unveiled that the linkage materializes in two possible ways: firstly, when monomers carrying pentagonal pyramidal coordination geometry adopt usual orientations (antiparallel alignment of the monomers attached through four-membered [Sb—S···]₂ ring) and characteristically organized neighboring “anchoring molecules” influence them to substantiate the linkage, and secondly when monomers align in unusual patterns (this is observed in both usual geometries, pentagonal pyramidal and trigonal antiprismatic). Interestingly, trigonal antiprismatic geometry with usual pattern of dimeric aggregation is deprived of the Sb···Sb linkage. Furthermore, DFT data are well consistent with the findings, and convincingly explains the rarity of the linkage.