The paramagnetic complexes (Tm^tBu)CoX (X = Cl, Br, I) have been readily prepared and structurally characterized and provide a convenient entry into cobalt(II) tris(mercaptoimidazolyl)borate chemistry. A number of derivatives, including mononuclear triphenylphosphine adducts [(Tm^tBu)Co(PPh₃)]X and dinuclear compounds [Co₂(Tm^tBu)₂X]Y, have been prepared in order to ascertain whether cobalt is a reliable surrogate for zinc in biological systems, particularly in sulfur-rich coordination environments. The structure of the first cobaltaboratrane is also reported.

The nickel boratrane complexes [κ⁴-B(mim Bu^t )₃]Ni(κ¹-OAc), [κ⁴-B(mim Bu^t )₃]NiNCS and [κ⁴-B(mim Bu^t )₃]NiN₃ are obtained viametathesis of the chloride ligand of [κ⁴-B(mim Bu^t )₃]NiCl with TlOAc, KSCN and NaN₃, respectively; the Ni→B bond in these complexes is a site of reactivity, thereby providing a means of synthesizing nickel complexes that feature B-functionalized tris(mercaptoimidazolyl)borate derivatives, [YTm Bu^t ]NiZ.