Hexakis(dimethylformamide)bis(hexaphenylcyclohexasiloxanehexaolato)hexacopper(II) Dimethylformamide Solvate

The sandwich-like title complex, hexakis(dimethylformamide)-1κO,2κO,3κO,4κO,5κO,6κO–bis[2,4,6,8,10,12-hexaphenylsiloxane-2,4,6,8,10,12-hexaolato(6−)-1:2κ²O¹,2:3κ²O²,3:4κ²O³,- 4:5κ²O⁴,5:6κ²O⁵,1:6κ²O⁶]hexacopper(II) tetrakis(dimethylformamide) solvate, [Cu₆(C₃H₇NO)₆{(C₆H₅)₆O₁₂Si₆}₂].4C₃H₇NO, is comprised of two regular crown-shaped macrocyclic hexadentate organosiloxanolate ligands chelating a flat Cu₆ hexagon, as in the ethanol-solvated analogue investigated previously. The title complex has a more distorted shape than the trigonal ethanol-solvated analogue, being slightly side-oblated, but still contains a large empty inner channel accessible by small molecules (the diameter of the free cross-section being about 2.5 Å). Each Cu^II ion has square-pyramidal coordination with four basal siloxanolate O atoms and an apical dimethylformamide (DMFA) molecule (coordinated through its carbonyl group). The average bond lengths are: Cu—O(Si) 1.964 (11) Å and Cu—O(DMFA) 2.215 (10) Å. The structure contains four additional DMFA molecules per complex unit, linked by weak C—H...O hydrogen bonds. Unexpectedly, the C=O bond length is longer [1.248 (10) and 1.255 (9) Å] in the uncoordinated DMFA molecules than in the coordinated [1.214–1.227 (7) Å].

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