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Studies on Chromium(III) and Vanadium(III) Complexes with Crown Ether and Crown Thioether Coordination – Synthesis, Properties and Structural Systematics
Author(s) -
Beard Charlotte D.,
Carr Loretta,
Davis Martin F.,
Evans John,
Levason William,
Norman Louise D.,
Reid Gillian,
Webster Michael
Publication year - 2006
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200600573
Subject(s) - thioether , chemistry , crown ether , 15 crown 5 , crystallography , stereochemistry , organic chemistry , ion
A series of six‐coordinate chloro Cr III and V III complexes involving crown ether, crown thioether and mixed ether/thioether crowns, [MCl 3 (crown)] (M = Cr or V; crown = 12‐crown‐4,15‐crown‐5,18‐crown‐6, [12]aneS 4 , [15]aneS 5 , [9]aneS 2 O,[15]aneS 2 O 3 , [18]aneS 3 O 3 ) has been prepared by the reaction of [MCl 3 (thf) 3 ] with rigorously dried crown in anhydrous CH 2 Cl 2 . In the presence of small amounts of water the mono‐aquo species [MCl 3 (H 2 O)(15‐crown‐5)] and [MCl 3 (H 2 O)(18‐crown‐6)] are obtained. The products have been characterised by IR and UV/Visible spectroscopy, microanalyses and for [CrCl 3 (H 2 O)(18‐crown‐6)], [VCl 3 (H 2 O)(15‐crown‐5)] and [CrCl 3 ([15]aneS 5 )], by X‐ray crystallography. The unexpected affinity of specifically the 15‐crown‐5 and 18‐crown‐6 complexes to pick up H 2 O is rationalised in terms of the strain within the two adjacent five‐membered chelate rings in the anhydrous (κ 3 ‐coordinated) species, and a wider survey of the structures reported for six‐coordinate M III crown complexes (M = Sc – Cr) with RECH 2 CH 2 ER (E = O or S) reveals that while the S–M–S angles in five‐membered chelate rings are typically around 82°, those involving O–M–O are very substantially more acute at around 75°. Thus, the [MCl 3 (κ 3 ‐crown ether)] complexes are much less stable and can alleviate some of this significant ring strain by switching to κ 2 ‐crown coordination with the H 2 O ligand completing the six coordination. In contrast, the crown thioether complexes have much less tendency to do this and hence appear to be more stable. Furthermore, using the structurally related (dimethylene linkages) mixed thia/oxa crowns to probe the M–O vs. M–S binding competitively, strongly indicates that the Cr III and V III preferentially coordinate to the thioether rather than the ether donor atoms, contrary to normal expectation based upon HSAB theory. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)