Functionalised Alkaline Earth Iodides from Grignard Synthons “PhAeI(thf)n” (Ae = Mg‐Ba)

Abstract

Derivatisation of Grignard synthons “PhAeI(thf)n” (Ae = Mg‐Ba) prepared in situ from reactions of metal filings and iodobenzene provides a one‐pot synthesis of heteroleptic N donor alkaline earth iodide complexes. Protolysis of “PhAeI(thf)n” with 3,5‐diphenylpyrazole (Ph2pzH) yields pyrazolate complexes [Mg2(µ‐Ph2pz)2(I)2(thf)3] (1), [Ae(Ph2pz)(I)(thf)4] (Ae = Ca (2), Sr (3)), and [Ba2(Ph2pz)2(µ‐I)2(thf)8] (4). Addition of the Ae‐Ph moiety to carbodiimide MesN=C=NMes (Mes = 2,4,6‐(CH3)3C6H2) gave a series of benzamidinate iodide complexes [Ca2{(MesN)2CPh}2(µ‐I)2(thf)4] (6), [Sr{(MesN)2CPh}(I)(thf)4] (7), and [{Ba{(MesN)2CPh}(µ‐I)(thf)3}∞] (8). By contrast a symmetrical magnesium complex [Mg{(MesN)2CPh}2(thf)] (5) was obtained by Schlenk redistribution. These syntheses proceed without pre‐activation of the metal for strontium and barium, and after activation with 2 mol‐% iodine for calcium. The heavy alkaline earth metal complexes are the first examples of heteroleptic halide pyrazolate or amidinate complexes for strontium and barium. Complexes 1, 3, 4 and 6–8 were characterised crystallographically, revealing diverse structural chemistry of heteroleptic amidinate and pyrazolate iodide complexes across the alkaline earth series. A highlight is [Ba{(MesN)2CPh}(µ‐I)(thf)3]∞ (8) – an iodide bridged infinite 1‐D polymer.