Paramagnetic bis(amidinate) iron(II) complexes and their diamagnetic dicarbonyl derivatives

Reactions of two equivalents of the lithium amidinate salts Li[tBuC(NR)(2)] (R = iPr, cyclohexyl) with FeCl2 have been found to yield paramagnetic bis (amidinate) iron(II) compounds of the type [tBuC(NR)(2)](2)Fe. In the case of R = cyclohexyl, the product has been characterized by single-crystal X-r ay diffraction analysis as having a distorted tetrahedral geometry. The der ivative with R = iPr is an oil, but its H-1 and C-13 NMR spectra indicate a similar monomeric structure. Both species have been found to react readily with CO to give the new diamagnetic Fe-II dicarbonyls [tBuC(NR)(2)](2)Fe(C O)(2). The compound with R = iPr has been structurally characterized, which showed it to have a strongly distorted octahedral structure with the carbo nyls in a cis arrangement.