Directed Ortho Calciation of 1,3-Bis(3-isopropylimidazol-2-ylidene)benzene

The deprotonation of 1,3-bis(3-isopropylimidazol-2-ylidene)benzene with Me3SiCH2CaX (X = Br, I) in tetrahydrofuran (THF) yields the ether adducts of the corresponding 2,6-bis(3-isopropylimidazol-2-ylidene)phenylcalcium halides (X = Br (1·2thf), I (2·2thf)). The crystallization behavior of 2 can be improved via substitution of ligated thf molecules by tetrahydropyran (thp) ligands, leading to 2·2thp. These heteroleptic complexes 1·2thf and 2·2thp show very small Ca–Cipso bond lengths to the ipso-carbon atoms of the aryl groups. Calciation of 1,3-bis(3-isopropylimidazol-2-ylidene)benzene with Ca(CH2SiMe3)2 in THP leads to the formation of ether-free homoleptic bis[2,6-bis(3-isopropylimidazol-2-ylidene)phenyl]calcium (3). Intramolecular steric strain causes an elongation of the Ca–Cipso bonds to the aryl groups. In all of these complexes, the Ca–Ccarbene distances are significantly larger than those to the ipso-carbon atoms of the aryl groups.