Probing the Salt‐Metathesis Route to Bis­(aryl)calcium Compounds: Structure of an Arylcalcate Complex

Abstract

Abstract1,3‐Diisopropoxybenzene can be selectively metalated by nBuLi or by the superbase mixtures nBuLi/NaOC(Me)2Et or nBuLi/KOC(Me)2Et to give 2,6‐diisopropoxyphenyllithium (71 %), 2,6‐diisopropoxyphenylsodium (61 %), or 2,6‐diisopropoxyphenylpotassium (59 %) as isolated products. The attempted synthesis of bis(2,6‐diisopropoxyphenyl)calcium by the salt metathesis route using 2,6‐diisopropoxyphenylsodium and CaI2 gave an undefined mixture of products, whereas the attempted synthesis of bis(2,6‐diisopropoxyphenyl)calcium by the same approach using 2,6‐diisopropoxyphenylpotassium and CaI2 gave the calcate complex [{(iPrO)2C6H3}3Ca]–K+, which is the first arylcalcate complex to have been structurally characterized. The trend in the 13C NMR chemical shifts of the aryl Cipso atoms shows that the calcate complex displays an aryl–metal bond polarity (nucleophilicity/basicity) similar to that in arylsodium compounds.