Mono(guanidinate) chromium(II) chloride complexes: Selective synthesis and structural characterization

Reaction of the lithium salts of the two sterically bulky guanidinate ligands, {Li[RC(NAr)2]} (Ar = 2,6-diisopropylphenyl; R = N(CH2)5 (1); R = NCy2 (2)) with one equivalent of CrCl2 in tetrahydrofuran (THF) at room temperature yielded the corresponding chloride-bridged binuclear complexes, [{(CH2)5NC(NAr)2}Cr(mu -Cl)2Cr (THF){(CH2)5NC(NAr)2}] (3) and [{Cy2NC(NAr)2}Cr(mu -Cl)]2 (4). These are rare examples of binuclear mono (guanidinate) chromium(II) chloride complexes without the formation of chromium "ate" complexes. Both complexes were characterized by single crystal X-ray analysis that showed strong boat-like distortions around the chromium centers. In compound 3 the coordination of one THF molecule to one of the Cr leads to two different coordination environments. In 4 both Cr atoms are four coordinated and show distorted square planar geometries around the chromium center. Nearly identical C-N bond lengths show considerable interaction of the lone pair of the non-coordinating N-atom with the conjugated NCN moiety. The three-dimensional Hirshfeld surface analysis and the two-dimensional fingerprint plots showed that H center dot center dot center dot H interactions, H center dot center dot center dot C/C center dot center dot center dot H and H center dot center dot center dot Cl/Cl center dot center dot center dot H H-bonds were the main and at times the strongest contributions for the intermolecular interactions.