FcTp(R) (R = i Pr or t Bu): 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 [FcTpR ; R = isopropyl (i Pr) or tert-butyl (t Bu)] have been synthesized in order to expand the range of redox-active third-generation scorpionates. These are [ferrocenyltris(3-tert-butylpyrazol-1-yl-κN2 )borato]thallium(I), [FeTl(C5 H5 )(C26 H37 BN6 )], [ferrocenyltris(3-isopropylpyrazol-1-yl-κN2 )borato]thallium(I), [FeTl(C5 H5 )(C23 H31 BN6 )], chlorido[ferrocenyltris(3-tert-butylpyrazol-1-yl-κN2 )borato]cobalt(II), [CoFe(C5 H5 )(C26 H37 BN6 )Cl], [ferrocenyltris(3-tert-butylpyrazol-1-yl-κN2 )borato]iodidocobalt(II) benzene disolvate, [CoFe(C5 H5 )(C26 H37 BN6 )I]·2C6 H6 , and [ferrocenyltris(3-isopropylpyrazol-1-yl-κN2 )borato]iodidocobalt(II), [CoFe(C5 H5 )(C23 H31 BN6 )I]. The structures demonstrate that the metal coordination site can easily be modified by using bulkier substituents at the pz 3-position.