Isolation of Tetranuclear Organoantimony Oxo Clusters and Hexa-decanuclear Polyoxostibonates

Abstract

Reaction of phenolic pyrazolyl ligands with arylstibonic acids afforded two novel tetranuclear clusters [(p-X-C6H4Sb)4(O)5(OH)2(HPhPzR1)4] (where X = Cl, R1 = Ph (1); X = Br, R1 = Ph (2); X = Br, R1 = t-Bu (3)) and [(p-Br-C6H4Sb)4(PhPz)4(O)4] (4). Depending on the steric bulk of the group present on the pyrazole ring, either one (1−3) or two (4) of the ring nitrogens have been found to coordinate to the metal atoms. Remarkably, when 3,5-DMPz is reacted with arylstibonic acid, hexa-decanuclear polyoxostibonates [(p-X-C6H4Sb)16(O)28(OH)8](3,5-DMPz)6 (X = Cl (5), Br (6)) have been isolated.

Investigations on the reactivity of arylboronic acid with phenolic pyrazole

“…Recently, we have investigated the reactions of phenolic pyrazoles with organostibonic acids wherein the presence of phenyl or tert-butyl groups on the 5-position of the pyrazole ring led to the formation of isostructural tetranuclear organoantimony oxo clusters wherein the pyrazoles chelated to the metal atoms through the O,N-end while the other N atom of the pyrazole is noncoordinating [52]. But when arylstibonic acids were reacted with phenolic pyrazoles with hydrogen on the 5-position of the pyrazole ring the ligand bound to the Sb atoms through both chelating (O,N-) and bridging (N,N-) mode.…”

“…But the ligating ability of phenolic pyrazoles (O,N,N-donors) towards main group metals were not known. Recently we have shown the utility of phenolic pyrazoles as ligands for synthesizing organoantimony oxo clusters by carrying out reactions with organostibonic acids [52]. Depending on the steric bulk of the group present in the pyrazole ring, either one or two nitrogen atoms coordinate to the antimony metal leading to the formation of novel tetranuclear clusters.…”

Tetranuclear stiboxanes (RSb)4O6, exhibiting an adamantane-type structure

“…10 Another interesting report in the chemistry of organostibonic acids is their ability to act as inorganic cryptands incorporating transition metals in their cavity. 11 Further, depolymerization reactions of organostibonic acids with protic ligands like organosilanediols, 12 phenolic pyrazoles 13 and the utility of mixed antimonate-phosphonate clusters as pro-ligands for synthesizing 3d clusters have also been reported. 14 Self-condensation reactions of organostibonic acids in the presence of bases have been investigated leading to the isolation of novel nonanuclear, 15 dodecanuclear 16,17 and hexadecanuclear isopolyoxostibonates.…”

“…14 Self-condensation reactions of organostibonic acids in the presence of bases have been investigated leading to the isolation of novel nonanuclear, 15 dodecanuclear 16,17 and hexadecanuclear isopolyoxostibonates. 13 It should also be mentioned here that though chemistry of monoorganostibonic acids is less investigated, several di-and triorganoantimony oxo clusters have been synthesized and structurally characterized by Sowerby and Breunig et al 18 In our continued effort to understand the reactivity of organostibonic acids with various protic ligands and to have a better insight in to the basic structural units involved in organoantimony oxo clusters, reactions of organostibonic acids with 8-hydroxyquinoline and naphthylphenolic pyrazole has been studied. Details of the synthesis along with the single crystal X-ray structural characterization of the products obtained are presented in this manuscript.…”

Preparation and molecular structure of the dimeric arylstibonic monoethylester [2,6-Mes2C6H3Sb(O)(OEt)(OH)]2

“…However, recently, the research groups of Winpenny (Baskar et al, 2007;Ali et al, 2008), Nicholson (Clark et al, 2009;Nicholson et al, 2010Nicholson et al, , 2011Nicholson et al, , 2012, Kortz (Piedra-Garza et al, 2009), and Baskar (Prabhu et al, 2009;Jami et al, 2010;Jami and Baskar, 2012) developed powerful strategies to build up discrete clusters and well-defined polyoxometalates based on arylstibonic acids by breaking down the random polymeric structures into smaller aggregates or by generating mononuclear arylantimony oxo moieties in situ using aryl cleavage reactions. Our strategy to avoid extensive aggregation in arylstibonic acids involved the kinetic stabilization provided by a bulky m -terphenyl substituent.…”