FcTp(R) (R = iPr or tBu): third-generation ferrocenyl scorpionates

Scorpionate (or trispyrazolylborate) ligands have seen much structural variation due to the relative ease of modifying their electronic and steric effects. Second-generation scorpionates were created by increasing the bulk in the 3-position of the pyrazole (pz) ring. A new class of third-generation scorpionates was obtained by modifying the remaining boron substituent. A series of thallium(I) and cobalt(II) complexes of the ferrocenyltris(3-R-pyrazolyl) borate ligand [FcTp(R); R = isopropyl (Pr-i) or tert-butyl (Bu-t)] have been synthesized in order to expand the range of redox-active third-generation scorpionates. These are [ferrocenyltris(3-tert-butylpyrazol-1-yl-kappa N-2)borato] thallium(I), [FeTl(C5H5)(C26H37BN6)], [ferrocenyltris(3-isopropylpyrazol-1-yl-kappa N-2)borato] thallium(I), [FeTl(C5H5)(C23H31BN6)], chlorido[ferrocenyltris(3-tert-butylpyrazol-1-yl-kappa N-2)borato] cobalt(II), [CoFe(C5H5)(C26H37BN6) Cl], [ferrocenyltris(3-tert-butylpyrazol-1-yl-kappa N-2) borato] iodidocobalt(II) benzene disolvate, [CoFe(C5H5)(C26H37BN6) I]center dot 2C(6)H(6), and [ferrocenyltris(3-isopropylpyrazol-1-yl-kappa N-2) borato] iodidocobalt(II), [CoFe(C5H5)(C23H31BN6) I]. The structures demonstrate that the metal coordination site can easily be modified by using bulkier substituents at the pz 3-position.