Post‐Grignard Reagents: Influence of the Coligands <i>L</i> on the Molecular Structures of Phenylcalcium Iodides [(<i>L</i>)<i>_n</i>Ca(<i>R</i>)I] and Calcium Diiodides [(<i>L</i>)<i>_n</i>CaI₂]

Abstract

Abstract Iodide 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 ) n CaI 2 ] and [( L ) n Ca( 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 CaI 2 or from the Schlenk equilibrium after the direct synthesis of calcium powder with aryl iodides. As L the ethers diethyl ether (Et 2 O), 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) 4 Ca(Ph)I] ( 1a ), [(thf) 4 Ca(Ph)I] ( 1b ), [(dme) 2 (thf)Ca(Ph)I] ( 1c ), [(18C6)Ca(Ph)I] ( 1d ), and [(tmeda) 2 Ca(Ph)I] ( 1e ), as well as [(thp) 4 CaI 2 ] ( 2a ), [(thf) 4 CaI 2 ] ( 2b ), [(Et 2 O) 4 CaI 2 ] ( 2c ), [(diglyme)(thf) 2 CaI 2 ] ( 2d ), [(diglyme)(dme)CaI 2 ] ( 2e ), [(dme) 2 (thf)CaI 2 ] ( 2f ), [(18C6)CaI 2 ] ( 2g ), [(tmeda) 2 CaI 2 ] ( 2h ), and [(hmteta)CaI 2 ] ( 2i ). For comparison reasons, [(thf) 4 Ca(Ph)Br] ( 3a ), [(thp) 4 CaBr 2 ] ( 4a ), [(thf) 4 CaBr 2 ] ( 4b ), and [(dme) 2 (AcOH)CaBr 2 ] ( 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.