The treatment of MCl(2).nH(2)O (M = Ca, Sr, or Ba) with 2-mercaptobenzoic acid (H-2-MBA) in a 1:2 ratio in an EtOH/H(2)O/NH(3) mixture leads to the formation of extended polymeric solids [[Ca(OOCC(6)H(4)SSC(6)H(4)COO)(H(2)O)(2)].0.5(C(2)H(5)OH)](n)(1), [[Sr(OOCC(6)H(4)SSC(6)H(4)COO)(H(2)O)(2)].0.5(C(2)H(5)OH)](n)(2), and [[Ba(2)(OOCC(6)H(4)SSC(6)H(4)COO)(2)(H(2)O)(2)].0.5H(2)O](n)(3), respectively. In all of the cases, under the reaction conditions employed, the H-2-MBA ligand undergoes thiol oxidation to form 2,2'-dithiobis(benzoic acid) (H(2)-DTBB). While the DTBB forms a 1:1 complex with heavier alkaline earth metals (1-3), only an ammonium salt, [(HOOCC(6)H(4)SSC(6)H(4)COOH)(HOOCC(6)H(4)SSC(6)H(4)COONH(4))] (4), was obtained as the final product in the reaction of H-2-MBA with MgCl(2).6H(2)O. Compounds 1-4 have been characterized with the aid of elemental analysis, thermal analysis, and infrared spectroscopic studies. All of the products are found to be thermally stable and do not melt on heating to 250 degrees C. Thermogravimetry on complexes 1-3 indicates the loss of coordinated and lattice water/solvent molecules below 200 degrees C (for complex 2) or 350 degrees C (for complexes 1 and 3). The solid-state structures of all of the derivatives 1-4 have been established by single-crystal X-ray diffraction studies. The calcium and strontium coordination polymers 1 and 2 are isomorphous. The DTBB ligands in 1 and 2 are hexadentate, and the compounds have a channel structure in which solvent ethanol molecules are included. In compound 3, barium ion forms a complex 3-dimensional coordination polymer where both the carboxylate and the sulfur centers of the DTBB ligands (which are hepta- and octadentate) coordinate to the metal.

Lipophilic N-bonded silanetriol RSi(OH)(3) (R=(2,6-iPr(2)C(6)H(3))N(SiMe(3))) can be utilized as an effective synthon for building a variety of multimetallic assemblies containing the Si-O-M motif. The type of metallosiloxane synthesized-its nuclearity and its molecular topology-can be readily modulated by the choice of the metal substrate, reaction stoichiometry, and reaction conditions. It is anticipated that the synthetic principles elaborated here will allow the design of many other multifunctional synthons.

A sterically hindered aryl phosphonic acid ArP(O)(OH)2 (2) (Ar = 2,4,6-isopropylphenyl) was synthesized and structurally characterized. ArP(O)(OH)2 forms an interesting hydrogen-bonded corrugated sheet-type supramolecular structure in the solid-state. A three-component reaction involving ArP(O)(OH)2, 3,5-dimethylpyrazole(DMPZH), and Cu(CH3COO)2.H2O produces the tetranuclear Cu(II) compound [Cu4(mu3-OH)2{ArPO2(OH)}2(CH3CO2)2(DMPZH)4][CH3COO]2.CH2Cl2 (3). A similar three-component reaction involving ArP(O)(OH)2, 3,5-dimethylpyrazole, and Zn(CH3COO)2.2H2O yields the tetranuclear Zn(II) compound [Zn4{ArPO3}2{ArPO2(OH)}2{DMPZH}4(DMPZ)2].5MeOH (4). While 3 has been found to have an asymmetric cage structure where two dinuclear copper cores are bridged by bidentate [ArPO2(OH)]- ligands, 4 possesses an open-book tricyclic structure composed of three fused metallophosphonate rings. Magnetic studies on 3 revealed antiferromagnetic behavior.

Reactions of alkaline earth metal chlorides with 2-aminobenzoic acid (2-abaH) have been investigated. The treatment of MCl2.nH2O (M = Mg, Ca, Sr or Ba) with 2-abaH in a 1:2 ratio in a MeOH/H2O/NH3 mixture leads to the formation of anthranilate complexes [Mg(2-aba)2] (1), [Ca(2-aba)2(OH2)3]infinity (2), [[Sr(2-aba)2(OH2)2].H2O)]infinity (3), and [Ba(2-aba)2(OH2)]infinity (4) respectively. Alternatively, these products can also be obtained starting from the corresponding metal acetates. Anthranilate complexes 1-4 have been characterized with the aid of elemental analysis, pH measurements, thermal analysis, and infrared, ultraviolet, and NMR (1H and 13C) spectroscopic studies. All the products are found to be thermally very stable and do not melt on heating to 250 degrees C. Thermal studies of complexes 2-4, however, indicate the loss of coordinated and lattice water molecules below 200 degrees C. In the case of the magnesium complex, the analytical and thermogravimetric studies indicate the absence of any coordinated or uncoordinated water molecules. Further, the solid-state structures of metal anthranilates 2-4 have been established by single-crystal X-ray diffraction studies. While the calcium ions in 2 are heptacoordinated, the strontium and barium ions in 3 and 4 reveal a coordination number of 9 apart from an additional weak metal-metal interaction along the polymeric chains. The carboxylate groups show different chelating and bridging modes of coordination behavior in the three complexes. Interestingly, apart from the carboxylate functionality, the amino group also binds to the metal centers in the case of strontium and barium complexes 3 and 4. However, the coordination sphere of 2 contains only O donors. All three compounds form polymeric networks in the solid state with the aid of different coordinating capabilities of the carboxylate anions and O-H...O and N-H...O hydrogen bonding interactions.

The reaction of (NHC)ZnEt2 (1) with 2,6-diisopropylphenol in the molar ratio 1:2 at room temperature resulted in the formation of NHC-stabilized monomeric tricoordinated zinc aryloxide (2), whereas the reaction of (NHC)ZnEt2 (1) with 2,4,6-trimethylphenol either in the presence of moisture or with deliberate addition of an equivalent amount of water in the molar ratio 1:2:1 afforded an unprecedented zinc hydroxyaryloxide (3). In this contribution we describe the syntheses and the structural characterization of 2 and 3 as well as the importance of the sterically encumbered phenols in the isolation of the final products.

No abstract

Dedicated to Dr. Manfred Flad on the occasion of his 90th birthdayPreparing a material that has particles of uniform dimension has been one of the biggest challenges for chemists as well as material scientists. The traditional ways of imparting order at the nanoscopic level have changed since the synthesis of fullerene clusters.[1] The use of techniques such as epitaxy and metal-organic chemical vapor deposition (MOCVD) have been used extensively in this regard. The synthesis of giant inorganic molecules, such as polyoxoanions, [2] Al 77 , [3] and Ga 84 [4] clusters are examples of inorganic counterparts of fullerenes. The synthesis of metal phosphonates using organometallic routes in recent years has led to the realization of a series of oligomeric transition-metal and main-group-metal phosphonates. [5, 6] In all these reports, the size of the oligomeric structure is highly dependent on the substituent on the metal center as well as at the phosphorus center. The metal phosphonates can be synthesized either using metal precursor-phosphonic acid interactions via an acid exchange or by starting from metal alkyls/amides/alcoholates by elimination of alkanes/amines/alcohols. [5][6][7] It has been demonstrated that metals belonging to the same group of the periodic table yield molecular phosphonates of the same topology if the substituents on the metal and phosphorus centers are kept the same. Although examples of zinc phosphonates following both the synthetic methodologies have been reported, there have been no examples of molecular cadmium phospho-

This article describes the recent results obtained in our laboratory on the interaction of polyfunctional ligands with divalent alkaline earth metal ions and a few divalent transition metal ions. Treatment of MCl 2 ⋅nH 2 O (M = Mg, Ca, Sr or Ba) with 2-amino benzoic acid leads to the formation of complexes [Mg(2-aba) 2 ] (1), [Ca(2-aba) 2 (OH 2) 3 ] ∞ (2), [{Sr(2-aba) 2 (OH 2) 2 } 2 ⋅H 2 O)] ∞ (3), [Ba(2-aba) 2 (OH 2)] ∞ (4), respectively. While the calcium ions in 2 are hepta-coordinated, the strontium and barium ions in 3 and 4 reveal a coordination number of nine apart from additional metal-metal interactions. Apart from the carboxylate functionality, the amino group also binds to the metal centres in the case of strontium and barium complexes 3 and 4. Complexes [{Mg(H 2 O) 6 }(4-aba) 2 ⋅2H 2 O] (5), [Ca(4-aba) 2 (H 2 O) 2 ] (6) prepared from 4-aminobenzoic acid reveal more open or layered structures. Interaction of 2-mercaptobenzoic acid with MCl 2 .6H 2 O (M = Mg, Ca), however, leads to the oxidation of the thiol group resulting in the disulphide 2,2′-dithiobis(benzoic acid). New metal-organic framework based hydrogen-bonded porous solids [{M(btec) (OH 2) 4 } n ⋅n(C 4 H 12 N 2)⋅4nH 2 O] (btec = 1,2,4,5-benzene tetracarboxylate) (M = Co 9; Ni 10; Zn 11) have been synthesized from 1,2,4,5-benzene tetracarboxylic acid in the presence of piperazine. These compounds are made up of extensively hydrogenbonded alternating layers of anionic M-btec coordination polymer and piperazinium cations. Compounds 2-11 described herein form polymeric networks in the solidstate with the aid of different coordinating capabilities of the carboxylate anions hydrogen bonding interactions.