Viswanathan Baskar

Organotin assemblies containing SnO bonds

Abstract This review deals with the recent progress in the area of organotin assemblies that contain SnO bonds. Various kinds of tri-, di- and monoorganotin compounds are described in terms of their preparation by methods such as hydrolysis of organotin halides, reactions of suitable oragnotin compounds with various kinds of substrates such as carboxylic acids, sulfonic acids, oxide transfer reagents etc. The structural characterization of these compounds by the use of 119 Sn-NMR, 119 Sn Mossbauer and X-ray crystallography is presented in considerable detail. The amazing structural diversity present in this family of compounds is discussed.

3d–4f Clusters with large spin ground states and SMM behaviour

Three new Cu-Ln cage complexes bridged by phosphonates and acetates are reported; one--a Cu(24)Dy(8) cage--is a new single molecule magnet (SMM).

Metal cages using a bulky phosphonate as a ligand

The synthesis, structure, magnetic and electronic properties of soluble transition metal phosphonate cages utilizing tritylphosphonic acid (TPA) as ligand are reported.

New structural form of a tetranuclear lanthanide hydroxo cluster: Dy4 analogue display slow magnetic relaxation.

A series of tetranuclear lanthanide (Ln = Tb, Dy, Ho) hydroxo clusters has been synthesized by reaction of LnCl3·6H2O (Ln = Tb (1), Dy (2), Ho (3)) with o-vanilin based schiff base ligand 2-(2,3 dihydroxpropyl imino methyl) 6-methoxy phenol (H3L) in methanol and in the presence of triethylamine as base. The solid state structures of all the products were established by single crystal X-ray diffraction technique. Magnetism studies reveal that Dy4 analogue exhibits slow magnetic relaxation at low temperatures.

Mixed antimonate-phosphonate ligands as polydentate bridging oxygen donors

A new class of oxygen donor ligands is described and preliminary results using these ligands are given which show they can be used to make polymetallic cages.

A new structural form for a decanuclear copper(II) assembly

The synthesis and structure of a novel decanuclear copper(II) cage is reported. The assembly of the cage is facilitated by the cumulative coordinative interaction of tert-butyl phosphonate, 2-pyridylpyrazole and hydroxide ligands with copper(II) ions. Magnetic studies of this decanuclear copper(II) cage indicate complex antiferromagnetic behaviour.

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

Depolymerization reactions of organostibonic acids with protic ligands have been investigated. Reaction of arylstibonic acids with 8-hydroxyquinoline (8-HQ), or {2-[1H-pyrazol-5(3)-yl]naphthalene-1-ol} (H(2)naphpz) in a 1 : 1 stoichiometry in refluxing toluene affords adamantane-like L(4)(RSb)(4)O(6) clusters [(p-XC(6)H(4)Sb)(4)(O)(6)(Q)(4)] (where X = Cl (1), Br (2), QH = 8-hydroxyquinoline), [(p-ClC(6)H(4)Sb)(4)(O)(6)(Hnaphpz)(4)]·H(2)naphpz (3) and [(p-Br-C(6)H(4)Sb)(4)(O)(6)(Hnaphpz)(4)](2)·H(2)naphpz (4). Further a tetrameric organoantimony oxo cluster, L(4)(RSb)(4)O(4) [(p-ClC(6)H(4)Sb)(4)(O)(4)(naphpz)(4)] (5) has also been isolated as a side product in the reaction of arylstibonic acid with naphthylphenolic pyrazole. Interestingly 1-4 structurally resemble the dimeric form of the antimony oxide Sb(2)O(3) and its mineral senarmontite.

Hexa- and trinuclear organoantimony oxo clusters stabilized by organosilanols.

Reactions of Ph2SbCl3 with RSi(OH)3 [where R = tert-Bu, cyclo-C6H11] and Ph2Si(OH)2 in toluene in the presence of triethylamine as a base were performed. Single-crystal X-ray structural elucidation of the products revealed the formation of hexanuclear antimony(V) and mixed-valent antimony (III/V) oxo-hydroxo clusters built up of an incomplete cubane subunit. Interestingly, in all the reactions, at least one Sb-C bond cleavage has been observed, leading to the formation of novel cluster assemblies [(Ph2Sb)4(PhSb)2(C4H9SiO3)2(O)6(OH)2] (1), [(Ph2Sb)4(PhSb)2(C6H11SiO3)2(O)6(OH)2] (2), [(Ph2Sb)(PhSb)2(Ph2SiO2)2(O)3(OH)2](-)Et3NH(+) (3), and [(Ph2Sb)4(Sb)2(Ph2SiO2)2(O)6(OH)2] (4), respectively.

ORGANOSTANNOXANE MOTIFS IN CAGES AND SUPRAMOLECULAR ARCHITECTURES

The reactions of n-butyl stannonic acid with(PhO) 2 P(O)H leads to the formation of a hexameric tin cage [{(n-BuSn) 3 (PhO) 3 O} 2 {HPO 3 } 4 ].This reaction involves an in situ P─O bond cleavage and the generation of a [HPO 3 ] 2− ion. A direct reaction of six equivalents of n-BuSnO(OH) acid with six equivalents of C 6 H 5 OH and four equivalents of H 3 PO 3 also leads to the formation of same cage structure. A tetranuclear organooxotin cage[(PhCH 2 ) 2 Sn 2 O(O 2 P(OH)-t-Bu) 4 ] 2 has been assembled by debenzylation involving the reaction of (PhCH 2 ) 2 SnCl 2 ,(PhCH 2 ) 2 SnO·H 2 O or (PhCH 2 ) 3 SnCl with two equivalents of t-BuP(O)OH 2 . A half-cage intermediate [(PhCH 2 ) 2 Sn 2 O(O 2 P(OH)-t-Bu) 4 ] has been detected. New organotin cations of the type [n-Bu 2 Sn(H 2 O) 4 ] 2+[2,5-Me 2 -C 6 H 3 SO 3 ]− 2 and {[n-Bu 2 Sn(H 2 O) 3 LSn(H 2 O) 3 (n-Bu) 2 ] 2+[1,5-(SO 3 ) 2 -C 10 H 6 ] 2−} have been obtained in the reactions of n-Bu 2 SnO or (n-Bu 3 Sn) 3 O with 2,5-dimethyl sulfonic acid and 1,5-naphthalene disulfonic acid respectively. These organotin cations form interesting supramolecular structures in the solid state as a result of O─H─···O hydrogen bonding.

First characterisation of weak hydrogen bonds in organoantimony compounds: C–H⋯Cl–Sb-mediated, zig-zag, supramolecular polymeric architecture in [Ph2Sb(Cl){S2C2(CN)2}]

The design and solid-state structure of an organoantimony compound containing several weak secondary interactions is described.