Selective synthesis of the missing tiara-like Ni 10 , Ni 5 and Ni 6 thiolates by the C-S bond cleavage of bis(thioether) molecules with a DFT study.

A series of new bis(phenylthioether) and bis(benzylthioether) compounds (L1-L5) having hexahydropyrimidine, imidazolidine and dihydroperimidine backbones were synthesized. Instead of giving NHC complexes, these compounds undergo facile C-S bond cleavages upon treatment with Ni(II) salts to selectively give new toroidal Ni(II) thiolates: [Ni 10 (SPh) 20 ] (1) and [Ni 5 (SCH 2 Ph) 10 ] (5), and the known [Ni 6 (SCH 2 Ph) 12 ] (8), as confirmed by single crystal X-ray diffraction studies. By-products such as RSSR (R = Ph and CH 2 Ph) and partially C-S bond cleaved starting compounds were isolated or detected as well from these reactions. The C-S bond cleavage does not take place with L5 having the dihydroperimidine backbone and a plausible mechanism is proposed based on by-products isolated or detected. DFT calculations give insights into the electronic structures of these ring systems and the nature of bonding with which a dichloromethane is present inside the cavity of 1. Experimentally observed absorption spectra of 1, 5 and 8 match with the calculated spectra.