Post‐Grignard Reagents: Influence of the Coligands L on the Molecular Structures of Phenylcalcium Iodides [(L)nCa(R)I] and Calcium Diiodides [(L)nCaI2

Abstract

AbstractIodide is a very soft and large anion and as such its extreme ability to be polarized leads to a flat energy surface with respect to the variation of the Ca–I distances in [(L)nCaI2] and [(L)nCa(R)I]. The influence of the donor strength and the bulkiness of the neutral coligands L on the Ca–I distances is studied. The base adducts of calcium diiodide can be isolated after the addition of L to CaI2 or from the Schlenk equilibrium after the direct synthesis of calcium powder with aryl iodides. As L the ethers diethyl ether (Et2O), tetrahydrofuran (thf), tetrahydropyran (thp), 1,2‐dimethoxyethane (dme), 18‐crown‐6 (18C6), bis(methoxyethyl)ether (diglyme), and amines tetramethylethylenediamine (tmeda), and hexamethyltriethylenetetramine (hmteta) are studied yielding the adducts [(thp)4Ca(Ph)I] (1a), [(thf)4Ca(Ph)I] (1b), [(dme)2(thf)Ca(Ph)I] (1c), [(18C6)Ca(Ph)I] (1d), and [(tmeda)2Ca(Ph)I] (1e), as well as [(thp)4CaI2] (2a), [(thf)4CaI2] (2b), [(Et2O)4CaI2] (2c), [(diglyme)(thf)2CaI2] (2d), [(diglyme)(dme)CaI2] (2e), [(dme)2(thf)CaI2] (2f), [(18C6)CaI2] (2g), [(tmeda)2CaI2] (2h), and [(hmteta)CaI2] (2i). For comparison reasons, [(thf)4Ca(Ph)Br] (3a), [(thp)4CaBr2] (4a), [(thf)4CaBr2] (4b), and [(dme)2(AcOH)CaBr2] (4c) with AcOH being acetic acid are included as well. The comparison shows that the coordination number of calcium itself only plays an insignificant role whereas bulkiness and donor strength of L represent the key influences.