An Na⁺ Complex and a Bis-BH₃ Complex of a [1.1]Cryptahemispherand

The [1.1] cryptahemispherand host 30,31,32-trimethoxy-5,10,15- trimethyl-22,27-dioxa-1,19-diazapentacyclo[17.5.5.1^3,7.1^8,12.1^13,17] 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[17.5.5.1^3,7.1^8,12.1^13,17]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.

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