Novel tetrahedral cobalt(ii) silanethiolates: structures and magnetism

Three heteroleptic complexes of Co(ii) tri-tert-butoxysilanethiolates have been synthesized with piperidine [Co{SSi(OtBu)(3)}(2)(ppd)(2)] 1, piperazine [Co{SSi(OtBu)(3)}(2)(NH(3))](2)(μ-ppz)·2CH(3)CN 2, and N-ethylimidazole [Co{SSi(OtBu)(3)}(2)(etim)(2)] 3. The complexes have been characterized by a single-crystal X-ray, revealing their tetrahedral geometry on Co(ii) coordinated by two nitrogen and two sulfur atoms. Complexes 1 and 3 are mononuclear, whereas 2 is binuclear. The spectral properties and thermal properties of 1–3 complexes were established by FTIR spectroscopy for solid samples and TGA. The magnetic properties of complexes 1, 2, and 3 have been investigated by static magnetic measurements and X-band EPR spectroscopy. These studies have shown that 1 and 3, regardless of the similarity in structure of CoN(2)S(2) cores, demonstrate different types of local magnetic anisotropy. Magnetic investigations of 2 reveal the presence of weak antiferromagnetic intra-molecular Co(ii)–Co(ii) interactions that are strongly influenced by the local magnetic anisotropy of individual Co(ii) ions.