Synthesis and characterization of six-coordinate "3 + 2" mixed-ligand oxorhenium complexes with the o-diphenylphosphinophenolato ligand and tridentate coligands of different N and S donor atom combinations

A series of octahedral six-coordinate oxorhenium(V) mixed ligand complexes containing the common [ReO(L)]2+ fragment (L = o-OC6H4P(C6H5)2] have been synthesized and characterized. Hence, it was shown that the [ReO(L)]2+ moiety can accommodate a variety of tridentate ligands containing a central amine group amenable to deprotonation and different combinations of lateral groups, such as ethylamine, substituted ethylamine, ethylthiol, and ethylthioether arms. In particular, by reaction of equimolar amounts of the pertinent HLn ligands with the [(n-C4H9)4N][ReOCl3(L)] precursor in refluxing acetonitrile/methanol or dichloromethane/methanol mixtures, the following series of [ReO(Ln)(L)]+/0 oxorhenium(V) complexes has been generated: ReO[[N(CH2CH2NH2)2][o-OC6H4P(C6H5)2]]Cl (1); ReO[[C2H5)2NCH2CH2NCH2CH2S][o-OC6H4P5)2]] (2); ReO[[(CH2)4NCH2CH2NCH2CH2S][o-OC6H4P(C6H4P(C6H5)2]] (3); and ReO[[C2H5SCH2CH2NCH2CH2S][o-OC6H4P(C6H5)2]] (4). The complexes are closed-shell 18-electron oxorhenium species, which adopt octahedral geometries both in solution and in the solid state, as established by conventional physicochemical techniques including multinuclear NMR and single-crystal X-ray diffraction analyses.     

Synthesis and characterization of mixed-ligand oxorhenium complexes with the SNN type of ligand. Isolation of a novel ReO[SN][S][S] complex

A new series of mixed-ligand oxorhenium complexes 4-9, with ligands 1-3 (L1H2) containing the SNN donor set and monodentate thiols as coligands (L2H), is reported. All complexes were synthesized using ReOCl3(PPh3)2 as precursor. They were isolated as crystalline products and characterized by elemental analysis and IR and NMR spectroscopy. The ligands 1 and 2 (general formula RCH2CH2NHCH2CH2SH, where R = N(C2H5)2 in 1 and pyrrolidin-1-yl in 2) act as tridentate SNN chelates to the ReO3+ core, leaving one open coordination site cis to the oxo group. The fourth coordination site is occupied by a monodentate aromatic thiol which acts as a coligand. Thus, three new "3 + 1" [SNN][S] oxorhenium complexes 4-6 (general formula ReO[RCH2CH2NCH2CH2S][SX], where R = N(C2H5)2 and X = phenyl in 4, R = N(C2H5)2 and X = p-methylphenyl in 5, and R = pyrrolidinlyl and X = p-methylphenyl in 6) were prepared in high yield. Complex 4 adopts an almost perfect square pyramidal geometry (tau = 0.07), while 6 forms a distorted square pyramidal geometry (tau = 0.24). In both complexes 4 and 6, the basal plane is formed by the SNN donor set of the tridentate ligand and the S of the monodentate thiol. On the other hand, the ligand 3, [(CH3)2CH]2NCH2CH2NHCH2CH2SH, acts as a bidentate ligand, probably due to steric hindrance, and it coordinates to the ReO3+ core through the SN atoms, leaving two open coordination sites cis to the oxo group. These two vacant positions are occupied by two molecules of the monodentate thiol coligand, producing a novel type of "2 + 1 + 1" [SN][S][S] oxorhenium mixed-ligand complexes 7-9 (general formula ReO[[(CH3)2CH]2NCH2CH2NHCH2CH2S][SX][SX], where X = phenyl in 7, p-methylphenyl in 8, and benzyl in 9). The coordination sphere about rhenium in 7 and 8 consists of the SN donor set of ligand 3, two sulfurs of the two monodentate thiols, and the doubly bonded oxygen atom in a trigonally distorted square pyramidal geometry (tau = 0.44 and 0.45 for 7 and 8, respectively). Detailed NMR assignments were determined for complexes 5 and 8.     

Chemistry of re with N,N'-bis(2-pyridylmethyl)ethylenediamine (H2pmen): hydrolysis, dehydrogenation, and ternary complexes

A number of Re complexes with N,N'-bis(2-pyridylmethyl)ethylenediamine (H2pmen) have been made from [NH4][ReO4]. [ReOCl2(H2pmen)]Cl, [ReOCl(Hpmen)][ReO4], and [ReO2(H2pmen)][ReO4] are related by hydrolysis/HCl substitution. [ReOCl(Hpmen)][ReO4] was structurally characterized and found to contain a water-stable amido-Re bond. Dehydrogenation of the N-donor ligand from each amine to imine with concomitant two-electron reduction of the Re center occurs readily in these systems. With suitable 3-hydroxy-4-pyrones, ternary complexes such as [ReIIICl(ma)(C14H14N4)][ReO4].CH3OH, 5, were made from [NH4][ReO4], H2pmen.4HCl and pyrones in one-pot syntheses. 5, a seven-coordinate ReIII complex, was structurally characterized.     

Synthesis,Characteristic Spectral Studies and in Vitro Antimicrobial Activity of Organosilicon(IV) Complexes of N-(2-Hydroxynaphthalidene)-Amino Acid Schiff Bases

Fifteen new organosilicon(IV) complexes formulated as R 3 Si[2-HOC 10 H 6 CH=NCH(X)COO] and Me 2 Si[2-OC 10 H 6 CH=NCH(X)COO] (where X = H[H 2 L 1 ], --CH 2 CH(CH 3 ) 2 [H 2 L 2 ], --CH 2 CH 2 -SCH 3 [H 2 L 3 ], --CH 3 [H 2 L 4 ] and --CH(CH 3 ) 2 [H 2 L 5 ] were prepared and characterized by 1 H and 13 C NMR, IR, electronic spectral studies, and elemental analysis. All of the complexes are nonelectrolytes. The spectral studies suggested a distroted trigonal-bipyramidal geometry around the silicon atom. Antimicrobial activity screening for all of the complexes was carried out against various bacteria [ Escherichia coli, Aeromonas formicans, Pseudomonas putida-2252, and Staphylococcus aureus-740 ] and fungi [ Aureobasidium pullulans-1991, Penicillium chrysogenum-1348, Verticillium dahliae-2063, and Aspergillus niger ORS-4 ]. The complexes showed good activity.     

Oxidation-promoted synthesis of ferrocenyl planar chiral rhodium(iii) complexes for C–H functionalization catalysis

The chemical oxidation of rhodium(i) complexes [Rh(L)(COD)][BF4], where L is a ferrocenyl phosphine/N-heterocyclic carbene ligand, with 2 equiv. of a triaryl-aminium salt [(4-BrC6H4)3N][BF4] in acetonitrile gave planar chiral, air-stable [Rh(L–H)(MeCN)3][BF4]2 complexes where the ferrocene (C5H4CH2ImR or C5H4CH2BImCH2Mes) ring has been C–H activated at the position 2 in good to excellent yields. An important reactivity difference between our complexes and the ubiquitous [Cp*Rh(MeCN)3]X2 complex has been observed in the Grignard-type arylation of 4-nitrobenzaldehyde.     

Syn-Anti Isomerism in a Mixed-Ligand Oxorhenium Complex, ReO[SN(R)S][S

The simultaneous action of the tridentate ligand (C(2)H(5))(2)NCH(2)CH(2)N(CH(2)CH(2)SH)(2) and the monodentate coligand HSC(6)H(4)OCH(3) on a suitable ReO(3+) precursor results in a mixture of syn- and anti-oxorhenium complexes, ReO[(C(2)H(5))(2)NCH(2)CH(2)N(CH(2)CH(2)S)(2)] [SC(6)H(4)OCH(3)], in a ratio of 25/1. The complexes are prepared by a ligand exchange reaction using ReO(eg)(2) (eg = ethylene glycol), ReOCl(3)(PPh(3))(2), or Re(V)-citrate as precursor. Both complexes have been characterized by elemental analysis, FT-IR, UV-vis, X-ray crystallography, and NMR spectroscopy. The syn isomer C(17)H(29)N(2)O(2)S(3)Re crystallizes in the monoclinic space group P2(1)/n, a = 14.109(4) ?, b = 7.518(2) ?, c = 20.900(5) ?, beta = 103.07(1) degrees, V = 2159.4(9) ?(3), Z = 4. The anti isomer C(17)H(29)N(2)O(2)S(3)Re crystallizes in P2(1)/n, a = 9.3850(7) ?, b = 27.979(2) ?, c = 8.3648(6) ?, beta = 99.86(1) degrees, V = 2163.9(3) ?(3), Z = 4. Complete NMR studies show that the orientation of the N substituent chain with respect to the Re=O core greatly influences the observed chemical shifts. Complexes were also prepared at the tracer ((186)Re) level by using (186)Re-citrate as precursor. Corroboration of the structure at tracer level was achieved by comparative HPLC studies.     

Seven-coordinate [ReVON4X2]+ complexes (X = O and Cl)

The oxorhenium(V) complexes with ligands containing N4 (H2pmen) and N4O2 (H2bbpen, H2Clbbpen, and H2bped) donor atom sets have been synthesized. X-ray crystallographic analyses of the [ReO(H2pmen)Cl2]+, [ReO(bbpen)]+, and [ReO(bped)]+ complexes showed that all three cations share a rare seven-coordinate structure with a distorted pentagonal bipyramidal geometry, which represents a novel and potentially general structural motif in ReV = O complexes. 1H NMR spectroscopy shows that the structures of the complexes are retained in the solution.     

Substituted N-picolylethylenediamines of the type (ArNHCH2CH2){(2-C5H4N)CH2}NR [R = Me, 4-CH2=CH(C6H4)CH2, (2-C5H4N)CH2] and their transition metal(II) halide complexes

Alkylation of (ArNHCH2CH2){(2-C5H4N)CH2}NH with RX [RX = MeI, 4-CH2=CH(C6H4)CH2Cl) and (2-C5H5N)CH2Cl] in the presence of base has allowed access to the sterically demanding multidentate nitrogen donor ligands, {(2,4,6-Me3C6H2)NHCH2CH2}{(2-C5H4N)CH2}NMe (L1), {(2,6-Me3C6H3)NHCH2CH2}{(2-C5H4N)CH2}NCH2(C6H4)-4-CH=CH2 (L2) and (ArNHCH2CH2){(2-C5H4N)CH2}2N (Ar = 2,4-Me2C6H3 L3a, 2,6-Me2C6H3 L3b) in moderate yield. L3 can also be prepared in higher yield by the reaction of (NH2CH2CH2){(2-C5H4N)CH2}2N with the corresponding aryl bromide in the presence of base and a palladium(0) catalyst. Treatment of L1 or L2 with MCl2 [MCl2 = CoCl2.6H2O or FeCl2(THF)1.5] in THF affords the high spin complexes [(L1)MCl2](M = Co 1a, Fe 1b) and [(L2)MCl2](M = Co 2a, Fe 2b) in good yield, respectively; the molecular structure of reveals a five-coordinate metal centre with bound in a facial fashion. The six-coordinate complexes, [(L3a)MCl2](M = Co 3a, Fe 3b, Mn 3c) are accessible on treatment of tripodal L3a with MCl2. In contrast, the reaction with the more sterically encumbered leads to the pseudo-five-coordinate species [(L3b)MCl2](M = Co 4a, Fe 4b) and, in the case of manganese, dimeric [(L3b)MnCl(mu-Cl)]2 (4c); in 4a and 4b the aryl-substituted amine arm forms a partial interaction with the metal centre while in 4c the arm is pendant. The single crystal X-ray structures of , 1a, 3b.MeCN, 3c.MeCN, 4b.MeCN and 4c are described as are the solution state properties of 3b and 4b.     

Physicochemical properties and structures of room-temperature ionic liquids. 3. Variation of cationic structures

A series of room-temperature ionic liquids (RTILs) were prepared with different cationic structures, 1-butyl-3-methylimidazolium ([bmim]), 1-butylpyridinium ([bpy]), N-butyl-N-methylpyrrolidinium, ([bmpro]), and N-butyl-N,N,N-trimethylammonium ([(n-C(4)H(9))(CH(3))(3)N]) combined with an anion, bis(trifluoromethane sulfonyl)imide ([(CF(3)SO(2))(2)N]), and the thermal property, density, self-diffusion coefficients of the cation and anion, viscosity, and ionic conductivity were measured over a wide temperature range. The self-diffusion coefficient, viscosity, ionic conductivity, and molar conductivity follow the Vogel-Fulcher-Tamman equation for temperature dependencies, and the best-fit parameters have been estimated, together with the linear fitting parameters for the density. The relative cationic and anionic self-diffusion coefficients for the RTILs, independently determined by the pulsed-field-gradient spin-echo NMR method, appear to be influenced by the shape of the cationic structure. A definite order of the summation of the cationic and anionic diffusion coefficients for the RTILs: [bmim][(CF(3)SO(2))(2)N] > [bpy][(CF(3)SO(2))(2)N] > [bmpro][(CF(3)SO(2))(2)N] > [(n-C(4)H(9))(CH(3))(3)N][(CF(3)SO(2))(2)N], has been observed, which coincides with the reverse order to the viscosity data. The ratio of molar conductivity obtained from the impedance measurements to that calculated by the ionic diffusivity using the Nernst-Einstein equation quantifies the active ions contributing to ionic conduction in the diffusion components and follows the order: [bmpro][(CF(3)SO(2))(2)N] > [(n-C(4)H(9))(CH(3))(3)N][(CF(3)SO(2))(2)N] > [bpy][(CF(3)SO(2))(2)N] > [bmim][(CF(3)SO(2))(2)N] at 30 degrees C.     

Synthesis, chemistry and structures of complexes of the dioxovanadium(V) halides VO2F and VO2Cl

[VO2F(L-L)] (L-L = 2,2'-bipyridyl, 1,10-phenanthroline, Me2N(CH2)2NMe2) and [VO2F(py)2] (py = pyridine) have been prepared from the corresponding [VOF3(L-L)] or [VOF3(py)2] and O(SiMe3)2 in MeCN solution. VO2F (itself made from VOF3 and O(SiMe3)2 in MeCN) forms [Me4N][VO2F2] with [Me4N]F, but does not react with neutral N- or O-donor ligands. VO2Cl, prepared from VOCl3 and ozone, reacts with 2,2'-bipyridyl or 1,10-phenanthroline to form [VO2Cl(L-L)], with pyridine or pyridine-N-oxide (L) to produce [VO2Cl(L)2], and with OPPh3 or OAsPh3 (L') gives [VO2Cl(L')]. A second product from the OPPh3 system is the ionic [VO2(OPPh3)3][VO2Cl2] containing a trigonal bipyramidal cation. Neither VO2F nor VO2Cl form isolable complexes with MeCN, thf or MeO(CH2)2OMe, and both are reduced by P-, As-, S- or Se-donor ligands. [Ph4As][VO2X2] (X = F or Cl) react with 2,2'-bipyridyl to form [VO2X(2,2'-bipyridyl)], but similar reactions with weaker O-donor ligands fail. The complexes have been characterised by IR, multinuclear NMR (1H, 19F, 51V or 31P) and UV-visible spectroscopy. X-ray crystal structures are reported for [VO2F(py)2], [VO2Cl(L)2] (L = py or pyNO) and [VO2(OPPh3)3][VO2Cl2].     

Ligating properties of a potentially tetradentate Schiff base [(CH3)2NCH2CH2N=CHC6H3(OH)(OMe)] with zinc(II), cadmium(II), cobalt(II), cobalt(III) and manganese(III) ions: synthesis and structural studies

A series of Zn(II), Cd(II), Co(II), Co(III) and Mn(III) complexes with the Schiff base [(CH3)2NCH2CH2N=CHC6H3(OH)(OMe)], LH, derived from 2-dimethylaminoethylamine and o-vanillin, has been synthesised and structures of all the products have been established by X-ray crystallography. In the cases of zinc and cadmium, dimeric complexes [Zn(LH)2(NCS)] [Zn2(L)(mu(1,1)-CH3COO)(NCS)3] (1), [Cd2(L)2(Cl)2] (2) and [Cd2(L)2(NCS)2] (3), and for cobalt and manganese, monomeric complexes [Co(LH)2(NCS)]2 [Co(NCS)4] (4), [Co(LH)2(NCS)]ClO4 (5), [Co(L)(N3)(o-vanillinate)] x 0.5 MeOH (6) and [Mn(LH)2(MeOH)2](ClO4)3 (7), are formed with various terminal ligands. All the complexes have been characterised by elemental analysis and IR spectra. UV-Vis and NMR spectroscopy, magnetic, and electrochemical studies, were also carried out where feasible. The Schiff base functions as a bi-, tri- or tetra-dentate chelating agent and coordinates via the protonated or deprotonated phenolic oxygen, amine and imine nitrogens, and only in case of 1 with the methoxy oxygen atoms, to the metal ion leading to the formation of mono- or bi-metallic complexes.     

Synthesis, characterization, and stereochemistry of oxorhenium(V) complexes with 2-aminoethanethiolate

A series of oxorhenium(V) complexes with 2-aminoethanethiolate (aet), [ReO(aet-N,S)(D-pen-N,O,S)] (2), [[ReO(aet-N,S)(2)](2)O] (3), [ReO(Cl)(aet-N,S)(2)] (4), and [ReO(aet-N,S)(Haet-S)(2)]Cl(2) ([5]Cl(2)) was newly prepared starting from ReO(4)(-). The reaction of NH(4)ReO(4) with a 1:1 mixture of Haet.HCl and D-H(2)pen (D-penicillamine) in the presence of SnCl(2).2H(2)O in water gave 2, 3, and the known complex [ReO(D-Hpen-N,S)(D-pen-N,O,S)] (1). These complexes were fractionally precipitated by controlling the pH of the reaction solution. The complex 2 was also prepared in a higher yield by a similar reaction using methanol as a solvent. The crystal structure of 2 was determined by X-ray crystallography; 2 crystallizes in the tetragonal space group P4(3) with a = 9.621(1), c = 12.911(1) A, V = 1195.0(3) A(3), and Z = 4. The oxorhenium(V) core in 2 is coordinated by a bidentate-N,S aet ligand and a tridentate-N,O,S D-pen ligand, having a distorted octahedral geometry with a cis-N cis-S configuration in the equatorial plane perpendicular to the O-Re-O axis. The 1:2 reaction of NH(4)ReO(4) with Haet.HCl in the presence of SnCl(2).2H(2)O in methanol produced 4, which is interconvertible with 3, while the corresponding 1:3 reaction resulted in the isolation of [5]Cl(2). The complexes 4 and 5 were also structurally characterized; 4 crystallizes in the monoclinic space group P2(1)/c with a = 6.839(1), b = 10.0704(6), c = 14.1075(8) A, beta = 91.729(8) degrees, V = 971.2(2) A(3), and Z = 4, while [5]Cl(2) crystallizes in the triclinic space group P1 with a = 11.938(3), b = 12.366(3), c = 5.819(1) A, alpha = 102.71(2), beta = 101.28(2), gamma = 75.41(2) degrees, V = 802.0(3) A(3), and Z = 2. In 4, the oxorhenium(V) core is octahedrally coordinated by two bidentate-N,S aet ligands, which form a cis-N cis-S configurational equatorial plane with a Cl(-) ion trans to the oxo ligand. On the other hand, the oxorhenium(V) core in [5](2+) is coordinated by one bidenate-N,S aet and two monodentate-S Haet ligands, having a distorted trigonal-bipyramidal geometry with S and N donors at the apical positions.     

Synthesis and characterization of novel 99gTc(V) and Re(V) complexes with water-soluble tetraaza diamido dipyridino ligands: single-crystal X-ray structural investigations of mono- and dinuclear complexes

Rhenium and technetium are known for their useful applications in nuclear medicine with similar properties. In this study, new diamido dipyridino (N(4)) water-soluble ligands (2-C(5)H(4)NCH(2)NHCO)(2)CH(2), 1 (L(1)H2), (2-C(5)H(4)NNHNHCO)(2)CH(2), 2, and [2-C(5)H(4)N(+)(O)(-)CH(2)NHCO](2)CH(2), 3, were synthesized. Reaction of L(1)H2 with ReOCl(3)(PPh(3))(2) resulted in the novel six-coordinated rhenium(V) complex, trans-ReO(L(1))(OEt), 4. The complex was characterized by spectroscopic methods, and its X-ray crystallographic analysis revealed that rhenium is coordinated to four nitrogen atoms of the ligand and to two oxygen atoms from the deprotonated ethanol and the oxo group respectively in a distorted octahedral geometry. In solution, complex 4 was transformed to a new complex 5, which was proved to be the dinuclear complex mu-oxo [ReO(L(1))](2)O. Reaction of 1 with [n-Bu(4)N][ReOCl(4)] resulted in the neutral complex 6, trans-[ReO(L(1))]Cl. Similarly, when ligand 1 was reacted with [n-Bu(4)N][(99g)TcOCl(4)], the neutral trans-[(99)TcO(L(1))]Cl complex 7 was formed, which upon dissolution transformed into a cationic complex 8, trans-[(99)TcO(L(1))(OH(2))](+)Cl(-). The single-crystal X-ray structure of 8 reveals that the coordination sphere about technetium is a distorted octahedron with four nitrogen atoms in the equitorial plane, while doubly bonded oxygen and coordinated water occupy the apical positions. Further dissolution of 8 resulted in the formation of dinuclear mu-oxo [TcO(L(1))](2)O, 9. This study shows that Tc and Re have similar metal core structures in solution for diamido dipyridino systems, besides similarity in geometrical structure, proved by the X-ray structures on the same ligands.     

Homotrinuclear lanthanide(III) arrays: assembly of and conversion from mononuclear and dinuclear units

The reactions of potentially hexadentate H2bbpen (N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-pyridylmethyl)-ethylenediamine, H2L1), H2(Cl)bbpen (N,N'-bis(5-chloro-2-hydroxybenzyl)-N,N'-bis(2-pyridylmethyl)ethylenediamine, H2L2), and H2(Br)bbpen (N,N'-bis(5-bromo-2-hydroxybenzyl)-N,N'-bis(2-pyridylmethyl)ethylenediamine, H2L3) with Ln(III) ions in the presence of a base in methanol resulted in three types of complexes: neutral mononuclear ([LnL(NO3)]), monocationic dinuclear ([Ln2L2(NO3)]+), and monocationic trinuclear ([Ln3L2(X)n(CH3OH)]+), where X = bridging (CH3COO-) and bidentate ligands (NO3-, CH3COO-, ClO4-) and n is 4. The formation of a complex depends on the base (hydroxide or acetate) and the size of the respective Ln(III) ion. All complexes were characterized by infrared spectroscopy, mass spectrometry, and elemental analyses; in some cases, X-ray diffraction studies were also performed. The structures of the neutral mononuclear [Yb(L1)(NO3)], dinuclear [Pr2(L1)2(NO3)(H2O)]NO3.CH3OH and [Gd2(L1)2(NO3)]NO3.CH3OH.3H2O, and trinuclear [Gd3(L3)2(CH3COO)4(CH3OH)]ClO4.5CH3OH and [Sm3(L1)2(CH3COO)2(NO3)2(CH3OH)]NO3.CH3OH.3.65H2O were solved by X-ray crystallography. The [LnL(NO3)] or [Ln2L2(NO3)]+ complexes could be converted to [Ln3L2(X)n(CH3OH)]+ complexes by the addition of 1 equiv of a Ln(III) salt and 2-3 equiv of sodium acetate in methanol. The trinuclear complexes were found to be the most stable of the three types, which was evident from the presence of the intact monocationic high molecular weight parent peaks ([Ln3L2(X)n]+) in the mass spectra of all the trinuclear complexes and from the ease of conversion from the mononuclear or dinuclear to the trinuclear species. The incompatibility of the ligand denticity with the coordination requirements of the Ln(III) ions was proven to be a useful tool in the construction of multinuclear Ln(III) metal ion arrays.     

Synthesis and structural characterization of mono- and bisfunctional o-carboranes

Functionalized o-carboranes are interesting ligands for transition metals. Reaction of LiC2B10H11 with Me2NCH2CH2Cl in toluene afforded 1-Me2NCH2CH2-1,2-C2B10H11 (1). Treatment of 1 with 1 equiv. of n-BuLi gave [(Me2NCH2CH2)C2B10H10]Li ([1]Li), which was a very useful synthon for the production of bisfunctional o-carboranes. Reaction of [1]Li with RCH2CH2Cl afforded 1-Me2NCH2CH2-2-RCH2CH2-1,2-C2B10H10 (R = Me2N (2), MeO (3)). 1 and 2 were also prepared from the reaction of Li2C2B10H10 with excess Me2NCH2CH2Cl. Treatment of [1]Li with excess MeI or allyl bromide gave the ionic salts, [1-Me3NCH2CH2-2-Me-1,2-C2B10H10][I] (4) and [1-Me2N(CH2=CHCH2)CH2CH2-2-(CH2=CHCH2)-1,2-C2B10H10][Br] (6), respectively. Interaction of [1]Li with 1 equiv. of allyl bromide afforded 1-Me2NCH2CH2-2-(CH2=CHCH2)-1,2-C2B10H10 (5). Treatment of [1]Li with excess dimethylfulvene afforded 1-Me2NCH2CH2-2-C5H5CMe2-1,2-C2B10H10 (7). Interaction of [1]Li with excess ethylene oxide afforded an unexpected product 1-HOCH2CH2-2-(CH2=CH)-1,2-C2B10H10 (8). 1 and 3 were conveniently converted into the corresponding deborated compounds, 7-Me2NHCH2CH2-7,8-C2B9H11 (9) and 7-Me2NHCH2CH2-8-MeOCH2CH2-7,8-C2B9H10 (10), respectively, in MeOH-MeOK solution. All of these compounds were characterized by various spectroscopic techniques and elemental analyses. The solid-state structures of 4 and 6-10 were confirmed by single-crystal X-ray analyses.     

Nature of urea-fluoride interaction: incipient and definitive proton transfer

1,3-bis(4-nitrophenyl)urea (1) interacts through hydrogen bonding with a variety of oxoanions in an MeCN solution to give bright yellow 1:1 complexes, whose stability decreases with the decreasing basicity of the anion (CH3COO- > C6H5COO- > H2PO4- > NO2- > HSO4- > NO3-). The [Bu4N][1.CH3COO] complex salt has been isolated as a crystalline solid and its molecular structure determined, showing the formation of a discrete adduct held together by two N-H...O hydrogen bonds of moderate strength. On the other hand, the F- ion first establishes a hydrogen-bonding interaction with 1 to give the most stable 1:1 complex, and then on addition of a second equivalent, induces urea deprotonation, due to the formation of HF2-. The orange-red deprotonated urea solution uptakes carbon dioxide from air to give the tetrabutylammonium salt of the hydrogencarbonate H-bond complex, [Bu4N][1.HCO3], whose crystal and molecular structures have been determined.     

Synthesis, structure, and catalytic properties of V(IV), Mn(III), Mo(VI), and U(VI) complexes containing bidentate (N, O) oxazine and oxazoline ligands

Synthesis of seven complexes containing oxazoline ([(L(1))(2)V=O] (4), [(L(1))(2)MoO(2)] (5), [(L(1))(2)UO(2)] (6); HL(1) (1) [HL(1) = 2-(4',4'-dimethyl-3'-4'-dihydroxazol-2'-yl)phenol]), chiral oxazoline ([(L(2))(2)UO(2)] (7); HL(2) (2) [HL(2) = (4'R)-2-(4'-ethyl-3'4'-dihyroxazol-2'-yl)phenol]), and oxazine ([(L(3))(2)V=O] (8), [(L(3))(2)Mn(CH(3)COO(-))] (9), [(L(3))(2)Co] (10); HL(3) (3) [HL(3) = 2-(5,6-dihydro-4H-1,3-oxazolinyl)phenol]) and their characterization by various techniques such as UV-vis, IR, and EPR spectroscopy, mass spectrometry, cyclic voltammetry, and elemental analysis are reported. The novel oxazine (3) and complexes 4, 5, 8 and 9 were also characterized by X-ray crystallography. Oxazine 3 crystallizes in the monoclinic system with the P2(1)/n space group, complexes 4 and 9 crystallize in the monoclinic system with the P2(1)/c space group, and complexes 5 and 8 crystallize in the orthorhombic system with the C222(1) space group and the P2(1)2(1)2(1) chiral space group, respectively. The representative synthetic procedure involves the reaction of metal acetate or acetylacetonate derivatives with corresponding ligand in ethanol. Addition of Mn(OAc)(2).4H(2)O to an ethanol solution of 3 gave the unexpected complex Mn(L(3))(2).(CH(3)COO(-)) (9) where the acetate group is coordinated with the metal center in a bidentate fashion. The catalytic activity of complexes 4-9 for oxidation of styrene with tert-butyl hydroperoxide was tested. In all cases, benzaldehyde formed exclusively as the oxidation product.     

Trithiacyclononane as a ligand for potential technetium and rhenium radiopharmaceuticals: synthesis of [M(9S3)(SC2H4SC2H4S)][BF4] (M = 99Tc, Re, 188Re) via C-S bond cleavage

Chemical or electrochemical reduction of the 1,4,7-trithiacyclononane (9S3) complexes [MII(9S3)2][BF4]2 (M = Re (3a) or Tc (3b)) results in instantaneous C-S bond cleavage to yield ethene and the stable MIII thiolate complexes [MIII(9S3)L][BF4] (M = Re (4a) or Tc (4b), L = SCH2CH2SCH2CH2S). Compounds 4 have been characterized by 1H NMR spectroscopy, and the pseudo-octahedral geometry of 4b has been confirmed by X-ray crystallography. Upon electrochemical reduction 4a loses ethene, while 4b can be reversibly reduced to [TcII(9S3)L], which is then further reduced to Tc(I) with loss of ethene. Successive ethene loss is observed in the mass spectra of compounds 3 and 4. The radiosynthesis of 4a with 188Re can be comfortably completed within 10 min starting with 188ReO4- from a 188W/188Re generator, with a radiochemical yield in excess of 90%, and thus represents a practical approach to the preparation of stable 188Re (and 99mTc) thioether complex derivatives/conjugates for clinical use. Crystal data: 4b, C10H20S6Tc, orthorhombic Pbca, a = 12.233(2) A, b = 14.341(2) A, c = 20.726(3) A, Z = 8.     

Low-melting, low-viscous, hydrophobic ionic liquids: aliphatic quaternary ammonium salts with perfluoroalkyltrifluoroborates

A novel class of low-melting, hydrophobic ionic liquids based on relatively small aliphatic quaternary ammonium cations ([R(1)R(2)R(3)NR](+), wherein R(1), R(2), R(3) = CH(3) or C(2)H(5), R = n-C(3)H(7), n-C(4)H(9), CH(2)CH(2)OCH(3)) and perfluoroalkyltrifluoroborate anions ([R(F)BF(3)](-), R(F) = CF(3), C(2)F(5), n-C(3)F(7), n-C(4)F(9)) have been prepared and characterized. The important physicochemical and electrochemical properties of these salts, including melting point, glass transition, viscosity, density, ionic conductivity, thermal and electrochemical stability, have been determined and comparatively studied with those based on the corresponding [BF(4)](-) and [(CF(3)SO(2))(2)N](-) salts. The influence of the structure variation in the quaternary ammonium cation and perfluoroalkyltrifluoroborate ([R(F)BF(3)](-)) anion on the above physicochemical properties is discussed. Most of these salts are liquids at 25 degrees C and exhibit low viscosities (58-210 cP at 25 degrees C) and moderate conductivities (1.1-3.8 mS cm(-1)). The electrochemical windows of these salts are much larger than those of the corresponding 1,3-dialkyimidazolium salts. Additionally, a number of [R(F)BF(3)](-) salts exhibit plastic crystal behavior.     

Mononuclear and dinuclear palladium and nickel complexes of phosphinimine-based tridentate ligands

The tridentate bis-phosphinimine ligands O(1,2-C(6)H(4)N=PPh(3))(2)1, HN(1,2-C(2)H(4)N=PR(3))(2) (R = Ph 2, iPr 3), MeN(1,2-C(2)H(4)N=PPh(3))(2)4 and HN(1,2-C(6)H(4)N=PPh(3))(2)5 were prepared. Employing these ligands, monometallic Pd and Ni complexes O(1,2-C(6)H(4)N=PPh(3))(2)PdCl(2)6, RN(1,2-CH(2)CH(2)N=PPh(3))(2)PdCl][Cl] (R = H 7, Me 8), [HN(1,2-CH(2)CH(2)N=PiPr(3))(2)PdCl][Cl] 9, [MeN(1,2-CH(2)CH(2)N=PPh(3))(2)PdCl][PF(6)] 10, [HN(1,2-CH(2)CH(2)N=PPh(3))(2)NiCl(2)] 11, [HN(1,2-CH(2)CH(2)N=PR(3))(2)NiCl][X] (X = Cl, R = iPr 12, X = PF(6), R = Ph 13, iPr 14), and [HN(1,2-C(6)H(4)N=PPh(3))(2)Ni(MeCN)(2)][BF(4)]Cl 15 were prepared and characterized. While the ether-bis-phosphinimine ligand 1 acts in a bidentate fashion to Pd, the amine-bis-phosphinimine ligands 2-5 act in a tridentate fashion, yielding monometallic complexes of varying geometries. In contrast, initial reaction of the amine-bis-phosphinimine ligands with base followed by treatment with NiCl(2)(DME), afforded the amide-bridged bimetallic complexes N(1,2-CH(2)CH(2)N=PR(3))(2)Ni(2)Cl(3) (R = Ph 16, iPr 17) and N(1,2-C(6)H(4)N=PPh(3))(2)Ni(2)Cl(3)18. The precise nature of a number of these complexes were crystallographically characterized.