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Conformational Versatility of Open‐Chain Polyethers: Crystal and Molecular Structures of the Ba(SCN) 2 Complexes of Two Heptaethyleneglycol Diaryl Ethers
Author(s) -
Hilgenfeld R.,
Hirayama F.,
Bhagwat V.,
Saenger W.,
Weber G.,
Sheldrick G. M.,
Sieger H.,
Vögtle F.
Publication year - 1984
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198400053
Subject(s) - chemistry , crystallography , molecule , thiocyanate , crystal structure , ion , hydrogen bond , metal , ether , metal ions in aqueous solution , stereochemistry , inorganic chemistry , organic chemistry
The crystal structures of the Ba(SCN) 2 complexes of two linear octaethers, heptaethyleneglycol diphenylether (HGPE; 1,20‐bis(phenyloxy)‐3,6,9,12,15,18‐hexaoxaicosane) and heptaethyleneglycol dinaphthylether (HGNE; 1,20‐bis(naphthyloxy)‐3,6,9,12,15,18‐hexaoxaicosane), are reported. In spite of their close similarity, the ligands adopt quite different conformations in their Ba(SCN) 2 complexes. HGPE wraps around the metal ion in a discontinuous helix providing seven of its eight ether oxygens for coordination. 10‐fold coordination of Ba 2+ is completed by the nitrogens of the SCN − ions and by a water molecule for which an occupancy of 0.37(5) was determined. In contrast, HGNE behaves as a hexadentate only. The barium ion is 9‐fold coordinated to six ether oxygens, to a water molecule, to one SCN − ion via its nitrogen atom and to a symmetry‐related thiocyanate ion via its sulphur atom. The second SCN − ion does not contact the metal ion but is hydrogen‐bonded to two symmetry‐generated water molecules. HGNE displays some unusual conformational features never found before for open‐chain polyethers.