Search

Systematic variation of the 1,4‐dioxane (dx) concentration during the precipitation of sparingly soluble [MgBr2(dx)2] from ethereal Grignard solutions of RMgBr has allowed the structural investigation of crystallized [R2Mg(dx)n] (n=1, 1.5, 2, and 3), which form during this dioxane method, depending on the bulkiness of R. The numbering of the complexes explored in this study is based on the number n of dioxane molecules per magnesium atom, followed by the substituent R; an apostrophe denotes coordination polymers. The following derivatives were studied by X‐ray crystal‐structure determination and NMR spectroscopy: n=1: [Me2Mg(μ‐dx)]∞ (1′‐Me) and [nPr2Mg(μ‐dx)]∞ (1′‐nPr); n=1.5: [{iPr2Mg(dx)}2(μ‐dx)] (1.5‐iPr), [{oTol2Mg(dx)}2(μ‐dx)] (1.5‐oTol), and [(Me3Si‐C≡C)2Mg(dx)1.5]∞ (1.5′‐C2SiMe3); n=2: [tBu2Mg(dx)2] (2‐tBu) and [oTol2Mg(dx)2] (2‐oTol); n=3: [Ph2Mg(dx)3] (3‐Ph). In the structure types 1′, 1.5, and 2, the magnesium atom exhibits the coordination number 4, whereas pentacoordinate metal atoms are observed in types 3 and 1.5′. The structure type 2′ is realized for [(Ph‐C≡C)2Mg(dx)2]∞ (2′‐C2Ph), [MgCl2(dx)2]∞ (2′‐Cl), and [MgBr2(dx)2]∞ (2′‐Br) with hexacoordinate metal atoms. The solubility of the dioxane adducts in common organic solvents strongly depends on the degree of aggregation with the solubility decreasing from molecular to strand to layer structures. [ABSTRACT FROM AUTHOR]

α,α′,α″,α′″-meso-Tetrahexyltetramethyl-calix[4]pyrrole is easily obtained as a single diastereomer in a one-pot reaction. It exhibits enhanced solubility in organic solvents, including aliphatic solvents, relative to its parentmeso-octamethylcalix[4]pyrrole (1). Somewhat surprisingly, the tetrahexyl derivative2complexes with tributylmethylammonium chloride in chloroform more strongly than does1as shown by NMR titrations. However,1and2exhibit comparable complexation strength in extraction experiments, the difference between the NMR and extraction results being attributed to the effect of organic-phase water in the extraction systems. Mass-action analysis indicates the formation of the predominant complex TBMA+(1or2)Cl−in both NMR and extraction systems, and equilibrium constants are reported. x-Ray crystal structures were obtained for the free ligand2and its complex with tetramethylammonium chloride. The free ligand crystallises in the 1,3-alt conformation with equatorial hexyl arms. In the chloride complex with2in its cone conformation, the hexyl arms adopt an axial orientation, enveloping the anion. DFT calculations show this binding conformation to be the most stable, mostly owing to destabilising steric interactions involving the pyrrole C–H and alkyl C–H groups positioned equatorially. [ABSTRACT FROM AUTHOR]