Antimony centre in three different roles: does donor strength or acceptor ability determine the bonding pattern?

• Published in: Dalton transactions : an international journal of inorganic chemistry 2024-11, Vol.53 (43), p.17721-17726
• Main Authors: Chlebík, Richard, Fekete, Csilla, Jambor, Roman, R i ka, Aleš, Benk, Zoltán, Dostál, Libor
• Format: Article
• Language: English
• Subjects: Antimony; Antimony compounds; Bonding strength; Chemical bonds; Coordination; Ligands; NMR spectroscopy; Palladium; Platinum; Single crystals; X-ray diffraction
• ISSN: 1477-9226; 1477-9234; 1477-9234
• DOI: 10.1039/d4dt02787f

A set of antimony( iii ) compounds containing a ligand (Ar) with a pendant guanidine function (where Ar = 2-[(Me 2 N) 2 C&z.dbd;N]C 6 H 4 ) was prepared and characterized. This includes triorgano- Ar 3 Sb , diorgano- Ar 2 SbCl and monoorgano- ArSbCl 2 compounds and they were characterized by 1 H and 13 C NMR spectroscopy and by single-crystal X-ray diffraction analysis (sc-XRD). The coordination capability of Ar 3 Sb and Ar 2 SbCl was examined in the reactions with either cis -[PdCl 2 (CH 3 CN) 2 ] or PtCl 2 and complexes cis -[(κ 2 -Sb,N- Ar 3 Sb )MCl 2 ] (M = Pd 1 , Pt 2 ) and [(κ 3 -N,Sb,N- Ar 2 SbCl )MCl 2 ] (M = Pd 3 , Pt 4 ) were isolated, while their structures were determined by sc-XRD. Notably, the ligands Ar 3 Sb and Ar 2 SbCl exhibit different coordination modes - bidentate and tridentate, respectively - and the antimony exhibits three distinct bonding modes in complexes 1-4 , which were also subjected to theoretical studies. The guanidine substituted organostibines allowed remarkable coordination variability including three distinct modes of M Sb bonding (M = Pd or Pt), i.e. Sb → M L-type and Z-type interactions involving M ← Sb donation and M → Sb backdonation.