Designing ionic liquids with boron cluster anions: alkylpyridinium and imidazolium [nido-C(2)B(9)H(11)] and [closo-CB(11)H(12)] carborane salts

A range of new alkylpyridinium and imidazolium carborane salts with [nido-C(2)B(9)H(12)](-), [closo-CB(11)H(12)](-), and [RC(2)B(11)H(11)](-) (R = methyl or butyl) anions have been prepared and characterized by physical and thermal methods, including the solid state structures of five of the salts determined by single crystal X-ray diffraction. The tendency of the salts to form low-melting ionic liquids has been assessed; all the salts studied with [nido-C(2)B(9)H(12)](-) anions melted below 100 degrees C and, significantly, have melting points that are 25-85 degrees C lower than those of the corresponding [closo-CB(11)H(12)](-) analogs, demonstrating that a wider range of boron-rich ionic liquid materials can be readily accessed.     

Microwave-assisted Kumada-type cross-coupling reactions of iodinated carba-closo-dodecaborate anions

The microwave-assisted Pd-catalyzed Kumada-type cross-coupling reaction of iodinated carba-closo-dodecaborate anions requires smaller amounts of Grignard reagent and catalyst and results in higher yields in much shorter reaction times in comparison to a reaction with conventional heat transfer. 12-Ph(3)P-closo-1-CB(11)H(11) was identified as the side product of the cross-coupling reactions that use [PdCl(2)(PPh(3))(2)]. The inner salt, which is the first example for a {closo-1-CB(11)} cluster with a B-P bond, was selectively synthesized via a related microwave-assisted cross-coupling protocol and characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. In addition, the crystal structures of the tetraethyl ammonium salts of [12-Ph-closo-1-CB(11)H(11)](-), [12-(4-MeOC(6)H(4))-closo-1-CB(11)H(11)](-), and [12-(H(2)C═(Me)CC≡C)-closo-1-CB(11)H(11)](-) are described.     

A novel zirconium polyoxometalate complex that contains both a coordinated saturated anion, [PMo12O40]3-, and a coordinated unsaturated anion, [PMo11O39]7-

The novel 8-coordinate zirconium compound (NH(4))(6)[Zr(PMo(12)O(40))(PMo(11)O(39))].26H(2)O (1) has been synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, and vibrational and (31)P NMR spectroscopy. It is the first example of a metal complex containing both parent, [PMo(12)O(40)](3)(-), and monovacant lacunary, [PMo(11)O(39)](7)(-), anions. Furthermore, this is the first crystallographic determination of the [PMo(11)O(39)](7)(-) anion.     

Silver phosphanes partnered with carborane monoanions: synthesis, structures and use as highly active Lewis acid catalysts in a hetero-Diels-Alder reaction

Four Lewis acidic silver phosphane complexes partnered with [1-closo-CB(11)H(12)](-) and [1-closo-CB(11)H(6)Br(6)](-) have been synthesised and studied by solution NMR and solid-state X-ray diffraction techniques. In the complex [Ag(PPh(3))(CB(11)H(12))] (1), the silver is coordinated with the carborane by two stronger 3c-2e B-H-Ag bonds, one weaker B-H-Ag interaction and a very weak Ag.C(arene) contact in the solid state. In solution, the carborane remains closely connected with the [Ag(PPh(3))](+) fragment, as evidenced by (11)B chemical shifts. Complex 2 [Ag(PPh(3))(2)(CB(11)H(12))](2) adopts a dimeric motif in the solid state, each carborane bridging two Ag centres. In solution at low temperature, two distinct complexes are observed that are suggested to be monomeric [Ag(PPh(3))(2)][CB(11)H(12)] and dimeric [Ag(PPh(3))(2)(CB(11)H(12))](2). With the more weakly coordinating anion [CB(11)H(6)Br(6)](-) and one phosphane, complex 3 [Ag(PPh(3))(CB(11)H(6)Br(6))] is isolated. Complex 4, [Ag(PPh(3))(2)(CB(11)H(6)Br(6))], has been characterised spectroscopically. All of the complexes have been assessed as Lewis acids in the hetero-Diels-Alder reaction of N-benzylideneaniline with Danishefsky's diene. Exceptionally low catalyst loadings for this Lewis acid catalysed reaction are required (0.1 mol %) coupled with turnover frequencies of 4000 h(-1) (quantitative conversion to product after 15 minutes using 3 at room temperature). Moreover, the reaction does not occur in rigorously dry solvent as addition of a substoichiometric amount of water (50 mol %) is necessary for turnover of the catalyst. It is suggested that a Lewis assisted Br?nsted acid is formed between the water and the silver. The effect of changing the counterion to [BF(4)](-), [OTf](-) and [ClO(4)](-) has also been studied. Significant decreases in reaction rate and final product yield are observed on changing the anion from [CB(11)H(6)Br(6)](-), thus demonstrating the utility of weakly coordinating carborane anions in organic synthesis.     

Polyhedral monocarbaborane chemistry. Some C-phenylated seven, eight, nine, ten, eleven and twelve-vertex species

Some synthetic and structural systematics for monocarbaboranes, using the C-phenylated motif as the example, are investigated. The 10-vertex [6-Ph-nido-6-CB(9)H(11)](-) anion 1, from reaction of PhCHO with B(10)H(14) in KOH/H(2)O, is a useful entry synthon into C-phenyl monocarbaborane chemistry. Treatment of anion 1 with Na/thf yields the 10-vertex [1-Ph-closo-1-CB(9)H(9)](-) anion 2a, whereas treatment of anion 1 with iodine in alkaline solution yields the isomeric 10-vertex [2-Ph-closo-2-CB(9)H(9)](-) anion 2b, which isomerises quantitatively to 2a on heating under reflux in DME. Thermolysis of anion 1 yields the 9-vertex [4-Ph-closo-4-CB(8)H(8)](-) anion 5, whereas treatment of anion 1 with FeCl(3)/HCl gives neutral 9-vertex [4-Ph-arachno-4-CB(8)H(13)] 3. Compound 3 gives neutral 9-vertex [1-Ph-nido-1-CB(8)H(11)] 4 in refluxing toluene, and gives the 7-vertex [2-Ph-closo-2-CB(6)H(6)](-) anion 7 and the 8-vertex [1-Ph-closo-1-CB(7)H(7)](-) anion 6 in refluxing toluene with NEt(3). Reaction of 1 with [BH(3)(thf)] yields the 11-vertex [7-Ph-nido-7-CB(10)H(12)](-) anion 8 which can be converted to the 12-vertex [1-Ph-closo-1-CB(11)H(11)](-) anion 10 using [BH(3)(SMe(2))]; alternatively, anion 1 yields anion 10 directly on treatment with [BH(3)(NEt(3))]. Treatment of anion 8 with I(2)/KOH yields the 11-vertex [2-Ph-closo-2-CB(10)H(10)](-) anion 9. The structures of anions 1, 2a, 2b, 5, 6, 7, 8, 9 and 10 have been established by single-crystal X-ray diffraction analyses of their [NEt(4)](+) salts, and those of neutral 3 and 4 estimated by DFT calculations at the B3LYP/6-31G* level; similar calculations have also been applied to the new anionic closo species 2a, 2b, 5, 6, 7, 9 and 10. Crystals of the [NEt(4)](+) salt of the [2-Ph-closo-2-CB(6)H(6)](-) anion 7 required synchrotron X-radiation for sufficient diffraction intensity for molecular-structure elucidation. The syntheses are in principle generally applicable to give extensive derivative C-aryl and C-alkyl chemistries.     

Carba-closo-dodecaborates with one or two alkynyl substituents bonded to boron

Salts of the carba-closo-dodecaborate anion with one or two phenyl- or trimethylsilylalkynyl substituents were synthesized by Pd-catalyzed Kumada-type cross-coupling reactions of the corresponding iodinated clusters with alkynyl Grignard reagents. Selective monofunctionalization in the 7- and 12-position of the {closo-CB(11)} cluster was achieved, resulting in salts of the anions: [1-R-12-R'C[triple bond]C-closo-CB(11)H(10)](-) (R = H, Ph; R' = Ph, Me(3)Si (1-4)), [12-Hal-7-PhC[triple bond]C-closo-CB(11)H(10)](-) (Hal = F (5), Cl (6), Br (7)), and [12-F-7-Me(3)SiC[triple bond]C-closo-CB(11)H(10)](-) (8). Furthermore, the disubstituted derivatives [7,12-(RC[triple bond]C)(2)-closo-CB(11)H(10)](-) (R = Ph (9), Me(3)Si (10)) are described. All salts were characterized by multi-NMR, IR, and Raman spectroscopy as well as by mass spectrometry (MALDI). The crystal structures of Cs(+)1 and [Et(4)N](+)6 were determined by single-crystal X-ray diffraction. The spectroscopic and structural properties are compared to values derived from DFT calculations and to data of related boron species with alkynyl groups.     

Monocarbaborane anion chemistry. [COOH], [CH2OH] and [CHO] units as functional groups on ten-vertex monocarbaborane anionic compounds

B(10)H(14) reacts with para-C(6)H(4)(CHO)(COOH) in aqueous KOH solution to give the [nido-6-CB(9)H(11)-6-(C(6)H(4)-para-COOH)](-) anion 1, which undergoes cage closure with iodine in alkaline solution to give the [closo-2-CB(9)H(9)-2-(C(6)H(4)-para-COOH)](-) anion 2. Upon heating, anion 2 rearranges to form the [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-COOH)](-) anion 3. Similarly, B(10)H(14) with glyoxylic acid OHCCOOH in aqueous KOH gives the [arachno-6-CB(9)H(13)-6-(COOH)](-) anion 4, which undergoes cage closure with iodine in alkaline solution to give the [closo-2-CB(9)H(9)-2-(COOH)](-) anion 5. Upon heating, anion 5 rearranges to give the [closo-1-CB(9)H(9)-1-(COOH)](-) anion 6. Reduction of the [COOH] anions 3 and 6 with diisobutylaluminium hydride gives the [CH(2)OH] hydroxy anions [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CH(2)OH)](-) and [closo-1-CB(9)H(9)-1-(CH(2)OH)](-) 8 respectively. The [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CH(2)OH)](-) anion 7 can also be made via isomerisation of the [closo-2-CB(9)H(9)-2-(C(6)H(4)-para-CH(2)OH)](-) anion 9, in turn obtained from the [nido-6-CB(9)H(11)-6-(C(6)H(4)-para-CH(2)OH)](-) anion 10, which is obtained from the reaction of B(10)H(14) with terephthaldicarboxaldehyde, C(6)H(4)-para-(CHO)(2), in aqueous KOH solution. Oxidation of the hydroxy anions 7 and 8 with pyridinium dichromate gives the aldehydic [closo-1-CB(9)H(9)-1-(C(6)H(4)-para-CHO)](-) anion 11 and the aldehydic [closo-1-CB(9)H(9)-1-(CHO)](-) anion 12 respectively, characterised as their 2,4-dinitrophenylhydrazone derivatives, the [closo-1-CB(9)H(9)-1-C(6)H(4)-para-CH=N-NHC(6)H(3)(NO(2))(2)](-) anion 13 and the [closo-1-CB(9)H(9)-1-CH=N-NHC(6)H(3)(NO(2))(2)](-) anion respectively.     

Cation-directed synthesis of tungstosilicates. 1. Syntheses and structures of K10A-alpha-[SiW9O34].24H2O,of the sandwich-type complex K10.75[Co(H2O)6]0.5[Co(H2O)4Cl]0.25A-alpha-[K2(Co(H2O)2)3(SiW9O34)2].32H2O and of Cs15[K(SiW11O39)2].39H2O

The influence of the nature of alkali metal cations on the structure of the species obtained from the trivacant precursor A-alpha-[SiW(9)O(34)](10-) has been studied. Starting from the potassium salt 1, K(10)A-alpha-[SiW(9)O(34)].24H(2)O, the sandwich-type complex 2, K(10.75)[Co(H(2)O)(6)](0.5)[Co(H(2)O)(4)Cl](0.25)A-alpha-[K(2)(Co(H(2)O)(2))(3)(SiW(9)O(34) )(2)].32H(2)O, has been obtained. The crystal structures of these two compounds consist of two A-alpha-[SiW(9)O(34)](10-) anions linked by a set of potassium (1) or cobalt plus potassium cations (2), and the relative orientation of the two half-anions is the same. Attempts to link two A-alpha-[SiW(9)O(34)](10-) anions by tungsten atoms instead of cobalt failed whatever the alkali metal cation. Moreover, the nondisordered structure of Cs(15)[K(SiW(11)O(39))(2)].39H(2)O is described. Two [SiW(11)O(39)](8-) anions are linked through a potassium cation with a "trans-oid" conformation, and the potassium occupies a cubic coordination site.     

Syntheses and crystal structures of the closo-borates M2[B7H7] and M[B7H8] (M = PPh4, PNP, and N(n-Bu4)): the missing crystal structure in the series [B(n)H(n)]2- (n = 6-12)

Oxidation of [N(n-Bu(4))](2)[B(9)H(9)] with oxygen in a mixture of dimethoxyethane and CH(2)Cl(2) leads to salts of the [B(7)H(7)](2-) dianion. This is the first convenient synthesis for a seven-vertex hydro-closo-borate anion. Protonation with NEt(3)·HCl resulted in salts of the [B(7)H(8)](-) monoanion. Both closo-borate anions were isolated and characterized by (1)H, (1)H{(11)B}, (11)B, and (11)B{(1)H} NMR spectroscopy. The temperature-dependent (1)H{(11)B}, (11)B, and (11)B{(1)H} NMR spectra of [B(7)H(8)](-) were also measured. The structure of [B(7)H(7)](2-) as well as of [B(7)H(8)](-) were determined by single-crystal X-ray diffraction.     

HCB11(CF3)(n)F(11-n)-: inert anions with high anodic oxidation potentials

Cs salts of four of the title anions were prepared by fluorination of salts of partly methylated (n = 11, 10) or partly methylated and partly iodinated (n = 6, 5) CB(11)H(12)(-) anions. The CH vertex is acidic, and in the unhindered anion with n = 6 it has been alkylated. Neat Cs(+)[1-H-CB(11)(CF(3))(11)](-) is as treacherously explosive as Cs(+)[CB(11)(CF(3))(12)](-), but no explosions occurred with the salts of the other three anions. BL3YP/6-31G* gas-phase electron detachment energies of the title anions are remarkably high, 5-8 eV. Treated with NiF(3)(+) in anhydrous liquid HF at -60 °C, anions with n = 11 or 10 resist oxidation, whereas anions with n = 6 or 5 are converted to colored EPR-active species, presumably the neutral radicals [HCB(11)(CF(3))(n)F(11-n)](?). These are stable for hours at -60 °C after extraction into cold perfluorohexane or perfluorotri-n-butylamine solutions. On warming to -20 °C in a Teflon or quartz tube, the color and EPR activity disappear, and the original anions are recovered nearly quantitatively, suggesting that the radicals oxidize the solvent.     

Structural polarity induced by cooperative hydrogen bonding and lone-pair alignment in the molecular uranyl iodate Na2[UO2(IO3)4(H2O)

Na2[UO2(IO3)4(H2O)] has been synthesized under mild hydrothermal conditions. Its structure consists of Na+ cations and [UO2(IO3)4(H2O)](2-) anions. The [UO2(IO3)4(H2O)](2-) anions are formed from the coordination of a nearly linear uranyl, UO2(2+), cation by four monodentate IO(3-) anions and a coordinating water molecule to yield a pentagonal bipyramidal environment around the uranium center. The water molecules form intermolecular hydrogen bonds with the terminal oxo atoms of neighboring [UO2(IO3)4(H2O)](2-) anions to yield one-dimensional chains that extend down the b axis. There are two crystallographically unique iodate anions in the structure of Na2[UO2(IO3)4(H2O)]. One of these anions is aligned so that the lone-pair of electrons is also directed along the b axis. The overall structure is therefore polar, owing to the cooperative alignment of both the hydrogen bonds and the lone-pair of electrons on iodate. The polarity of the monoclinic space group C2 (a = 11.3810(12) A, b = 8.0547(8) A, c = 7.6515(8) A, beta = 90.102(2) degrees , Z = 2, T = 193 K) found for this compound is consistent with the structure. Second-harmonic generation of 532 nm light from a 1064 nm laser source yields a response of approximately 16x alpha-SiO2.     

Metal complexes of tetrapodal ligands: synthesis, spectroscopic and thermal studies, and X-ray crystal structure studies of Na(I), Ca(II), Sr(II), and Ba(II) complexes of tetrapodal ligands N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine and N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine

Twelve complexes 1-12 of general category [M(ligand)(anion)(x)(water)(y)], where ligand = N,N,N',N'-tetrakis(2-hydroxypropyl/ethyl)ethylenediamine (HPEN/HEEN), anion = anions of picric acid (PIC), 3,5-dinitrobenzoic acid (DNB), 2,4-dinitrophenol (DNP), and o-nitrobenzoic acid (ONB), M = Ca(2+), Sr(2+), Ba(2+), or Na(+), x = 1 and 2, and y = 0-4, were synthesized. All of these complexes were characterized by elemental analysis, IR, (1)H and (13)C NMR, and thermal studies. X-ray crystal studies of these complexes 1-12, [Ca(HPEN)(H(2)O)(2)](PIC)(2).H(2)O (1), [Ca(HEEN)(PIC)](PIC) (2), Ba(HPEN)(PIC)(2) (3), [Na(HPEN)(PIC)](2) (4), Ca(HPEN)(H(2)O)(2)](DNB)(2).H(2)O (5),Ca(HEEN)(H(2)O)](DNB)(2).H(2)O (6), [Sr(HPEN)(H(2)O)(3)](DNB)(2) (7), [Ba(HPEN)(H(2)O)(2)](DNB)(2).H(2)O](2) (8), [[Ba(HEEN)(H(2)O)(2)](ONB)(2)](2) (9), [[Sr(HPEN)(H(2)O)(2)](DNP)(2)](2) (10), [[Ba(HPEN)(H(2)O)(2)](DNP)(2)](2) (11), and [Ca(HEEN)(DNP)](DNP) (H(2)O) (12), have been carried out at room temperature. Factors which influence the stability and the type of complex formed have been recognized as H-bonding interactions, presence/absence of solvent, nature of the anion, and nature of the cation. Both the ligands coordinate the metal ion through all the six available donor atoms. The complexes 1 and 5-11 have water molecules in the coordination sphere, and their crystal structures show that water is playing a dual character. It coordinates to the metal ion on one hand and strongly hydrogen bonds to the anion on the other. These strong hydrogen bonds stabilize the anion and decrease the cation-anion interactions by many times to an extent that the anions are completely excluded out of the coordination sphere and produce totally charge-separated complexes. In the absence of water molecules as in 2 and 3 the number of hydrogen bonds is reduced considerably. In both the complexes the anions case interact more strongly with the metal ion to give rise to a partially charge-separated 2 or tightly ion-paired 3 complex. High charge density Ca(2+) forms only monomeric complexes. It has more affinity toward stronger nucleophiles such as DNP and PIC with which it gives partially charge-separated eight-coordinated complexes. But with relatively weaker nucleophile like DNB, water replaces the anion and produces a seven coordinated totally charge-separated complex. Sr(2+) with lesser charge/radius ratio forms only charge-separated monomeric as well as dimeric complexes. Higher coordination number of Sr(2+) is achieved with coordinated water molecules which may be bridging or nonbridging in nature. All charge-separated complexes of the largest Ba(2+) are dimeric with bridging water molecules. Only one monomeric ion-paired complex was obtained with Ba(PIC)(2). Na(+) forms a unique dinuclear cryptand-like complex with HPEN behaving as a heptadentate chelating-cum-bridging ligand.     

Lithium salts of [1,12-dialkyl-CB11Me10]- anions

We report the syntheses of several [1-R-CB(11)-Me(11)](-) and [1-R-12-R'-CB(11)-Me(10)](-) anions (R, R' = alkyl) and the solubilities of their lithium salts in cyclohexane. These solutions are of interest as Lewis acid catalysts. The new anions are not directly accessible by methylation with methyl triflate because of intervening triflyloxy substitution on one or more boron vertices. The difficulty has been circumvented in two ways. Either (i) an iodo substituent is first introduced into position 12, permitting a clean decamethylation, and then replaced with a methyl by reaction with trimethylaluminum or (ii) the offending triflyloxy substituents are replaced with methyls by reaction with trimethylaluminum.     

Two new "onium" fluorosilicates, the products of interaction of fluorosilicic acid with 12-membered macrocycles: structures and spectroscopic properties

Two novel compounds, (L(1)H)(2)[SiF(6)] x 2H(2)O (1) and (L(2)H)(2)[SiF(5)(H(2)O)](2) x 3H(2)O (2), resulting from the reactions of H(2)SiF(6) with 4'-aminobenzo-12-crown-4 (L(1)) and monoaza-12-crown-4 (L(2)), respectively, were studied by X-ray diffraction and characterised by IR and (19)F NMR spectroscopic methods. Both complexes have ionic structures due to the proton transfer from the fluorosilicic acid to the primary amine group in L(1) and secondary amine group incorporated into the macrocycle L(2). The structure of 1 is composed of [SiF(6)](2-) centrosymmetric anions, N-protonated cations (L(1)H)(+), and two water molecules, all components being bound in the layer through a system of NH[...]F, NH[...]O and OH[...]F hydrogen bonds. The [SiF(6)](2-) anions and water molecules are assembled into inorganic negatively-charged layers via OH[dot dot dot]F hydrogen bonds. The structure of 2 is a rare example of stabilisation of the complex anion [SiF(5)(H(2)O)](-), the labile product of hydrolytic transformations of the [SiF(6)](2-) anion in an aqueous solution. The components of 2, i.e., [SiF(5)(H(2)O)](-), (L(2)H)(+), and water molecules, are linked by a system of NH[...]F, NH[...]O, OH[...]F, OH[dot dot dot]O hydrogen bonds. In a way similar to 1, the [SiF(5)(H(2)O)](-) anions and water molecules in 2 are combined into an inorganic negatively-charged layer through OH[...]F and OH[...]O interactions.     

Trinuclear to dinuclear: a radii dependence lanthanide(III) self-assembly coordination behavior of an amide-type tripodal ligand

Lanthanide nitrate complexes with the heptadentate ligand L (6-[2-(2-(diethylamino)-2-oxoethoxy)ethyl]-N,N,12-triethyl-11-oxo-3,9-dioxa-6,12-diazatetradecanamide), [Ln(2)L(NO(3))(6)] (Ln = La, Nd, Sm, Eu, Ho), have been prepared and characterized. The X-ray crystallographic studies show that, in [La(2)L(NO(3))(6)(H(2)O)].H(2)O (1), two complex cations [LaL(H(2)O)](3+) are linked by a hexanitrato anion [La(NO(3))(6)](3)(-) and form a trinuclear cation. In [Nd(2)L(NO(3))(6)(H(2)O)].CHCl(3).1/2CH(3)OH.1/2H(2)O (2), one complex cation [NdL(H(2)O)](3+) and a hexanitrato complex anion [Nd(NO(3))(6)](3)(-) are linked by a bridging NO(3)(-) to form a dinuclear complex. In both complexes, the bridging nitrate is an unusual tetradentate ligand. The metal ions are 12-coordinated in hexanitrato anions and 10-coordinated in complex cations. The chainlike supramolecular structures of La(3+) complex are parallel and have no hydrogen bonds in between, while, in the Nd(3+) complex, a chiral cavity is formed by hydrogen bonds between two adjacent supramolecular chains. These influences are further investigated by assessing the separation efficiency of L and (1)H NMR spectra of its lanthanide nitrate mixtures in solution.     

Infrared and computational investigation of vanadium-substituted Keggin [PVnW12-nO40](n+3)- polyoxometallic anions

This study investigates complex salts of [PW(12)O(40)](3-), [PVW(11)O(40)](4-), [PV(2)W(10)O(40)](5-), and [PV(3)W(9)O(40)](6-) Keggin anions using Fourier transform infrared spectroscopy under ambient atmospheric and high-vacuum conditions and by computational methods. A detailed vibrational study suggests that the presence and amount of vanadium in these anions can be tested quickly and reliably with the help of infrared spectroscopy because the salts of these anions exhibit distinctly different infrared absorption signatures (particularly in the 1025-1250 cm(-1) region, where the P-O stretch is surrounded by a set of complex vibrations involving V-O and W-O bonds). Investigation of these salts with different countercations suggests that the overall appearance of the spectra, and thus the ability to use infrared as a diagnostic tool to identify the presence and number of vanadium atoms in Keggin structure anions, is not affected significantly. Last, it is shown that all the structures investigated are extremely stable across a wide range of temperatures.     

Synthesis and structural characterization of a new series of vanadoselenites, [Se(x)V(4-x)O(12-x)](4-x)- (x=1,2)

Two new vanadoselenites, [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-), were synthesized by reacting SeO(2) with VO(3)(-). Single-crystal X-ray structural analyses of [(n-C(4)H(9))(4)N](3)[SeV(3)O(11)].0.5H(2)O [orthorhombic, space group P2(1)2(1)2, a = 22.328(5) A, b = 44.099(9) A, c = 12.287(3) A, Z = 8] and [[(C(6)H(5))(3)P](2)N](2)[Se(2)V(2)O(10)] [monoclinic, space group P2(1)/n, a = 12.2931(3) A, b = 13.5101(3) A, c = 20.9793(5) A, beta = 106.307(1) degrees, Z = 2] revealed that both anions are composed of Se(x)()V(4)(-)(x)()O(4) rings. The (51)V, (77)Se, and (17)O NMR spectra established that both [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-) anions maintain this ring structure in solution.     

S-alkylation and S-amination of methyl thioethers--derivatives of closo-[B(12)H(12)](2-). synthesis of a boronated phosphonate, gem-bisphosphonates, and dodecaborane-ortho-carborane oligomers

A variety of S-alkylated products was prepared by alkylation of methyl thioethers [MeSB(12)H(11)](2-) (5), [1-(MeS)-2(7,12)-(Me(2)S)B(12)H(10)](-) (6-8), and [1,2(7,12)-(MeS)(2)B(12)H(10)](2-) (9-11) with alkyl halides and tosylates in acetonitrile. Since these methyl thioethers can be prepared easily in B-10-enriched form on a large scale and due to their chemical versatility, they are potentially very attractive boron entities for the design and synthesis of therapeutics for boron neutron capture therapy of cancer. It was found that alkylation of 6-8 can be complicated by an equilibrium which establishes between, on the one hand, one of the former species and, on the other hand, 1,2(7,12)-(Me(2)S)(2)B(12)H(10) (2-4) and [1,2(7,12)-(MeS)(2)B(12)H(10)](2-) (9-11). A boronated phosphonate 1-(MeS(CH(2))(4)P(O)(OEt)(2))-7-(Me(2)S)B(12)H(10) (14g) and a gem-bisphosphonate 1-(MeS(CH(2))(3)CH[P(O)(OEt)(2)](2))-7-(Me(2)S)B(12)H(10) (14h) were prepared from thioether 7 and the corresponding iodide and tosylate, respectively, and subsequently converted to their sodium salts. The propargyl sulfonium salts obtained by alkylation of thioethers 7, 8, 10, and 11 with propargyl bromide have been further converted to two- and three-cage oligomers containing both ortho-carborane and dodecaborane moieties. Methyl thioethers derived from closo-[B(12)H(12)](2-) are excellent participants in Michael addition reactions in the presence of a strong acid. The sulfonium salts with tertiary alkyl and vinyl substituents have been prepared by this method. Methyl thioethers 5-11 react with hydroxylamine-O-sulfonate yielding the corresponding aminosulfonium salts, albeit in lower yields as compared to those in the alkylation reactions. Several derivatives of methyl thioethers 5-11 have been characterized by single-crystal X-ray diffraction.     

New ionic crystals of oppositely charged cluster ions and their characterization

By reacting Keggin-type polyoxometalate cluster anions H(2)W(12)O(40)(6)(-) (metatungstate) or Co(II)W(12)O(40)(6)(-) (tungstocobaltate) with the large aluminum cluster polycation [Al(30)O(8)(OH)(56)(H(2)O)(26)](18+), Keggin ion based molecular ionic compounds [delta-Al(13)O(4)(OH)(24)(H(2)O)(12)][XW(12)O(40)](OH).nH(2)O (X = H(2) (1) and Co (2); n congruent with 20) and [W(2)Al(28)O(18)(OH)(48)(H(2)O)(24)][H(2)W(12)O(40)](2).55H(2)O (3) were obtained. The polygon-shaped cluster ions are packed alternately through intercluster hydrogen bonds as well as electrostatic interactions, leaving large pores, which result from the packing of large clusters. The clusters are arranged in square pyramidal geometries, showing face-to-face interactions between them. The isolation of metastable [delta-Al(13)O(4)(OH)(24)(H(2)O)(12)](7+) and the formation of a new transition metal substituted aluminum heteropolycation [W(2)Al(28)O(18)(OH)(48)(H(2)O)(24)](12+) in 1-3 result from the slow fragmentation and recombination of Al(30) in the presence of suitable counter cluster anions with similar shape and charge.     

Metal ion-dependent molecular inclusion chemistry: inclusion of aromatic anions by coordinated 1,4,7,10-tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraazacyclododecane

The ability of the pendant donor macrocyclic ligand 1,4,7,10-tetrakis((S)-2-hydroxy-3-phenoxypropyl)-1,4,7,10-tetraaza- cyclododecane((S)-thphpc12) (or [Cd((S)-thphpc12)](2+)) to act as a metal ion-dependent receptor for aromatic anions has been investigated in solution and in the solid state. [Cd((S)-thphpc12)](2+) adopts a stable conical conformation with a large hydrophobic cavity, which has been shown to contain, via complementary multiple hydrogen bonding, p-nitrophenolate, aromatic carboxylates, p-toluenesulfonate, certain aromatic amino acid anions, phenoxyacetate, and acetate. In the case of p-nitrophenolate only, one or two anions can be contained within the receptor cavity. The crystal structure of [Cd((S)-thphpc12)(p-nitrophenolate)(2)] shows a coplanar arrangement of the p-nitrophenolates, where each is retained in the cavity by a pair of hydrogen bonds to cis hydroxyl groups. The crystal structure of the p-aminobenzoate inclusion complex indicates retention of the guest via a pair of hydrogen bonds to each oxygen atom of the carboxylate moiety. The crystal structure of the (L)-phenylalaninate inclusion complex indicates that the amino acid is retained by five hydrogen bonds, two involving the nitrogen atom and three to the oxygen atoms of the carboxylate moiety. Binding constants (10(3)-10(5) M(-1)) for the inclusion of some of the aforementioned anions in [Cd((S)-thphpc12)](2+) and related receptors were measured by (1)H NMR titration in DMSO-d(6) at 298 K.