Benz–amidinato Stabilized a Monomeric Calcium Iodide and a Lithium Calciate(II) Cluster featuring Group 1and Group 2 Elements

摘要

Soluble calcium halides reported so far are mostly dimeric in nature. The halides occupy the bridging position and thus provide additional coordination to the metal. We obtained a monomeric calcium iodide [{PhC(NiPr)2}CaI(thf)3] (1) from the reaction of [PhC(NiPr)2]Li with CaI2 in THF. The compound has been stabilized by electronic donation and steric shielding from the amidinate ligand as well as coordination of three THF molecules. 1 does not show any propensity towards ligand exchange reaction. When the same reaction is carried out in diethyl ether instead of THF, it led to the formation of a Li calciate(II) cluster of composition L2Ca4I8Li4O (L=PhC(NiPr)2) (2) with an encapsulated O~(2-) in the middle of a tetrahedron spanned by four Ca~(2+) ions. 2 represents a metal-rich halide comprising of both alkali and alkaline earth metals which is quite unprecedented. Another notable aspect is that the amidinate ligand binds to the calcium atom in chelating bidentate mode in 1, whereas in 2 each N atom of the amidinate ligands binds to two Ca atoms leading to bridging bis-chelating coordination mode.