Systematic Structural Coordination Chemistry ofp‐tert‐Butyltetrathiacalix[4]arene: Main Group Metal Complexes Other Than Those of Group 1

Abstract

In extension of previous work involving structural characterisation of complex salts formed between main group 1 metal ions and p‐tert‐butyltetrathiacalixarene, LH4, the present study encompasses complexes with a wider array of main group 2, 13, 14 metal ions. For group 2, single‐crystal X‐ray structural characterisation of Ca(LH3)2·3dmf (1a), {Ca(LH2)·3dmf}2 (1b), Ba(LH3)2·6dmf (2a) and BaCO3·3Ba(LH3)2·3H2O·3CH3CN·12.25CH2Cl2 (2b) provides models for various coordination units. For group 13, this applies to {Ga(OH)(LH2)·3.5dmf}2 (3), {In(LH)·4EtOH·2CH2Cl2}2 (4a) and {In(OH)(LH2)·3CH2Cl2}4 (4b), and for group 14, to OPb4(LH)2·6dmf·dmso·2H2O (5). Overall, these define mononuclear (1a, 2a), binuclear (1b, 3, 4b) and tetranuclear (2b, 4b, 5) species. The calixarene cavities frequently include solvent molecules, though this capacity is clearly influenced by the nature of the bound metal ion(s) and their binding, as well as the associated impact on the conformation of the calixarene ligand(s).

Systematic Structural Coordination Chemistry of p‐tert‐Butyltetrathiacalix[4]arene: Further Complexes of Lanthanide Metal Ions

“…[10,11] A remarkable aspect of the coordination chemistry of tetrasulfonylcalix [4]arene, in particular, is the formation, aided by carboxylate coligands, of octanuclear and dodecanuclear "wheel" complexes of the lanthanides [11][12][13] and, in the present work, we show that the formation of oligonuclear lanthanide complexes is characteristic of the interaction of LH 4 with the complete lanthanide series and that our previous characterisation of the tetranuclear sandwich species Nd 4 L 2 [5] provides but one example of the several structures which appear to be possible. A feature of this structure which is repeated in most of the present cases is the stoichiometric complexity of the asymmetric unit and, as we have found in our earlier studies, [1][2][3][4][5][6][7][8] there appears to be a complicated kinetic control of the species deposited from the various reaction mixtures, involving solvents such as dimethylformamide (dmf), dimethyl sulfoxide (dmso), acetonitrile and pyridine (py), having a wide range of polarity and basicity, used for synthesis. The lanthanide(III) complexes provide the first instance of an extended set of M III derivatives of LH 4 , previous examples involving only the smaller cations Fe III , Ga III and In III .…”

“…A simple method of synthesis which does provide microcrystalline samples for all Ln III is to react dmso solvates of the metal nitrates with the deprotonated ligand in dmso but the products are exceedingly insoluble in most solvents and, although they can be recrystallised from pyridine by vapour-diffusion addition of acetonitrile, this has not in all cases provided crystals suitable for structure determination, and it is clearly associated with changes in the chemical composition of the solids. Various related procedures have proved successful in particular cases, though the consequences of varying reagent concentration, for example, have proved somewhat erratic; more general aspects of the synthesis of thiacalixarene complexes have been discussed earlier, [1,2] including the fact that, despite the use of formally anhydrous reagents, many isolated materials proved to be hydrolysis products from water present in the solvents. Many of the problems associated with attempted single-crystal studies of calixarene complexes, such as their facile efflorescence and disorder associated with tert-butyl groups, are well known (see, for example, references [16][17][18] ) and other particular problems in the structure analysis, such as ambiguity in proton locations and the identification of remarkable mixtures of solvent components, have been of considerable importance in the present work.…”

“…In the immediately preceding [1,2] and some earlier publications, [3][4][5][6][7][8] we have described the results of our efforts to characterise, through structural studies, the solid-state coordination chemistry of the macrocyclic ligand p-tert-butyltetrathiacalix [4]arene, LH 4 , in its "parent", unfunctionalised form. Broader aspects of this chemistry concerning various derivatives and homologues of this thiacalixarene have been recently reviewed, [9] as has the specific function…”

“…The lanthanide(III) complexes provide the first instance of an extended set of M III derivatives of LH 4 , previous examples involving only the smaller cations Fe III , Ga III and In III . [1,2] For complexes of water-soluble thiacalix [4]arene derivatives, with Tb III specifically, however, considerable structural information is available. [11,14,15] …”

Functionalization reactions of calixarenes

“…Pillarenes, [62][63][64] in which benzene rings are linked by para, and not by meta positions as in calixarenes should also be included. A special group are the thia, oxa and azacalixarenes, in which the linking methylene groups of calixarenes are formally replaced by sulfur, [65][66][67] oxygen, [68][69][70] or nitrogen, [71][72][73] atoms, respectively.…”