An Na+Complex and a Bis-BH3Complex of a [1.1]Cryptahemispherand

Abstract

The [1.1] cryptahemispherand host 30,31,32-trimethoxy-5,10,15- trimethyl-22,27-dioxa-1,19-diazapentacyclo[17.5.5.13,7.18,12.113,17] dotriaconta-3,5,7(30),8,10,12 (31),13,15,17 (32)-nonaene forms a crystalline complex, (I), with sodium tetraphenylborate, [Na(C34H44N2O5)] (C24H20B), and also forms a coordination complex, (II), with two molecules of BH3, μ-{30,31,32-trimethoxy-5,10,15- trimethyl-22,27-dioxa-1,19-diazapentacyclo[17.5.5.13,7.18,12.113,17]dotriaconta-3,5,7(30),8,10,12 (31),13,15,17 (32)-nonaene}-N1:N19– bis(trihydroboron), C34H50B2N2O5, which crystallizes as a CH2Cl2 hemisolvate. The host of (I) complexes Na+ more strongly than it does any other alkali metal ion, consistent with the nearly ideal coordination of Na+ reported here. The N atoms, which are only about 2.6 Å from the Na+ ion, are unusually close to each other in (I), being separated by about 4.63 Å. The solvent in the structure of (I) is disordered and unidentifiable. The structure of (II) was determined at 115 K. It contains two independent molecules in the asymmetric unit, each with site symmetry m; they have very similar conformations. The BH3 groups attached to the N atoms are directed outward from the cavity of each molecule, giving the molecules the uncommon exo-exo conformation. The N atoms in (II) are about 1.3 Å farther apart than those in (I). Because the N atoms are tetrasubstituted, (II) is a poor complexer. One –CH2CH2OCH2CH2– bridge in each cryptand moiety in (II) adopts a 'crown' conformation, while the other bridge has trans –CH2CH2– torsion angles. The cavity of the host in (II) is filled, and the conformation is stabilized by typical C—H⋯O interactions.