Solvatochromism of Mono- and Dimolybdenum Coordination Compounds of Dipyridyloctatetraene and Linear Solvation Energy Relationship Models Based on the Kamlet-Taft and Drago Scales of Solvent Polarity

The heteroleptic molybdenum complexes [{Mo(NO)TpX}(n)()(L-L)] [Tp = HB(3,5-Me(2)C(3)HN(2))(3); X = Cl, I; L-L = 4-NC(5)H(4)(CH=CH)(4)C(5)H(4)N-4', n = 1, 2; X = Cl; L-L = {4,4'-NC(5)H(4)CH=CHC(Me)=CHCH=}(2), n = 2] have a low energy absorbance in their electronic spectra which exhibits solvatochromic shifts. These have been analyzed quantitatively by means of linear solvation energy relationships based on Kamlet-Taft solvatochromism parameters, as well as on Drago's "unified scale of solvent polarity". Each of these approaches leads to satisfactory linear models, in qualitative agreement with one another. The solvatochromism is due to a combination of increased solvent dipolarity/polarizability and solvent-to-solute hydrogen bonding, each preferentially stabilizing polar ground states compared with less polar excited states. The latter originate from metal-to-ligand charge transfer. Quantitatively, the Drago and Kamlet-Taft models differ somewhat. The former are statistically slightly better than those based on Kamlet-Taft parameters.     

Formation of a layered framework structure based upon 4-methyl-2,6-bis(methylphosphonic acid) phenol

The trifunctional ligands, [(HO)2P(O)CH2]2C6H2(R)OH, (5-H4)(R = CH3, Br) were prepared in good yield via an Arbusov reaction between P(OEt)3 and the respective 4-R-2,6-bis(chloromethyl)phenols followed by acidic aqueous hydrolysis and they were spectroscopically characterized by IR and NMR techniques. The ligand 5-H4-CH3 readily dissolves lanthanide hydroxide residues and it forms a crystalline complex from aqueous LaCl3 solutions. This complex was characterized by single crystal X-ray diffraction methods and found to adopt a complex 2-D lamellar network in the bc plane. The La(III) inner coordination sphere is seven coordinate formed by oxygen atoms from two water molecules and five phosphonate oxygen atoms from three different ligands. The phenolic oxygen atom is not involved in the ligand binding to La(III).     

Desoxo molybdenum(IV) and tungsten(IV) bis(dithiolene) complexes: monomer-dimer interconversion involving reversible thiol bridge formation

Two series of thiol-bridged dimeric desoxo molybdenum(IV) and tungsten(IV) bis(dithiolene) complexes, [Et(4)N](2)[M(IV)(2)(SR)(2)(mnt)(4)] [M = Mo, R = (1) -Ph, (2) -CH(2)Ph, (3) -CH(2)CH(3), (4) -CH(2)CH(2)OH; M = W, R = (1a) -Ph, (2a) -CH(2)Ph, (3a) -CH(2)CH(3), (4a) -CH(2)CH(2)OH] and one monomeric desoxo complex, [Et(4)N](2)[WIV(SPh)(2)(mnt)(2)] (5a) are reported. These complexes are diamagnetic, and crystal structures of each of the complex (except 5a) exhibits a dimeric {M(IV)(2)(SR)(2)} core without any metal-metal bond where each metal atom possesses hexa coordination. The M-SR distance ranges from 2.437 to 2.484 Angstrom in molybdenum complexes and from 2.418 to 2.469 Angstrom in tungsten complexes. These complexes display Mo-S(R)-Mo angles ranging from 92.84 degrees to 96.20 degrees in the case of 1-4 and W-S(R)-W angles ranging from 91.20 degrees to 96.25 degrees in the case of 1a-4a. Interestingly, both the series of Mo(IV) and W(IV) dimeric complexes respond to an unprecedented interconversion between the dimer and the corresponding hexacoordinated monomer upon change of pH. This pH-dependent interconversion establishes the fact that even the pentacoordinated Mo(IV) and W(IV) bis(dithiolene) moieties are forced to dimerize; these can easily be reverted back to the corresponding monomeric complex, reflecting the utility of dithiolene ligand in stabilizing the Mo(IV)/W(IV) moiety in synthesized complexes similar to the active sites present in native proteins.     

Imine-assisted C-F bond activation by electron-rich iron complexes supported by trimethylphosphine

C-F bond activation of ortho-fluorinated benzalimines 2,6-F(2)C(6)R1R2R3-CH=N-R (1-3) using the electron-rich complex Fe(PMe(3))(4) is reported. With the assistance of the imine group as the anchoring group, bis-chelated iron(II) complexes (C(6)FR1R2R3-CH=N-R)(2)Fe(PMe(3))(2) (4-6) were formed. The reaction of 2,6-difluorobenzylidenenaphthalen-1-amine 2,6-F(2)C(6)H(3)-CH=N-C(10)H(7) (9) with Fe(PMe(3))(4) affords [CNC]-pincer iron(II) complex (C(6)H(3)F-CH=N-C(10)H(6))Fe(PMe(3))(3) (10) through both C-F and C-H bond activation and π-(C=N) coordinate iron(0) complex (C(6)H(3)F-CH=N-C(10)H(7))(2)Fe(PMe(3))(2) (11) with C,C-coupling, while a similar reaction with perfluorobenzylidenenaphthalen-1-amine C(6)F(5)-CH=N-C(10)H(7) (14) gave rise to only [CNC]-pincer iron(II) complex (C(6)F(4)-CH=N-C(10)H(6))Fe(PMe(3))(3) (15). The proposed formation mechanisms of these complexes are discussed. The structures of complexes 5, 6, 10 and 11 were confirmed by X-ray single crystal diffraction.     

二茂铁衍生物光学特性的氧化还原开关效应

设计合成了三种具有推拉电子取代基的二茂铁衍生物D-Fc-R(1), D-Fe-A1(2), [D-Fc-A2(3)N-C6H4-CH=CH, R :CH2OH, A1 : CHO, A2 : CH=C(CN)2], 并对其循环伏安及光谱电化学行为进行了研究。三种衍生物均出现两个氧化还原电时,1的两个电对均可逆, 单扫第一电对, 2的第一电对是可逆, 3的第一电对是准可逆, D-Fc^+-R在613nm, D-Fc^+-A1在705nm有强LMCT带, 具有良好的光学特性氧化还原开关效应。     

New iridacyclohexadienes and iridabenzenes by [2+2+1] cyclotrimerization of alkynes and facile interconversion between iridacyclohexadienes and iridabenzenes

Iridabenzenes [Ir[=CHCH=CHCH=C(CH2R)](CH3CN)2(PPh3)2]2+ (R=Ph 4 a, R=p-C6H4CH3 4 b) are obtained from the reactions of H+ with iridacyclohexadienes [Ir[-CH=CHCH=CHC(=CH-p-C6H4R')](CO)(PPh3)2]+ (R'=H 3 a, R'=CH3 3 b), which are prepared from [2+2+1] cyclotrimerization of alkynes in the reactions of [Ir(CH3CN)(CO)(PPh3)2]+ with HC[triple chemical bond]CH and HC[triple chemical bond]CR. Iridabenzenes 4 react with CO and CH3CN in the presence of NEt3 to give iridacyclohexadienes [Ir[-CH=CHCH=CHC(=CHR)](CO)2(PPh3)2]+ (6) and [Ir[-CH=CHCH=CHC(=CHR)](CH3CN)2(PPh3)2]+ (7), respectively. Iridacyclohexadienes 6 and 7 also convert to iridabenzenes 4 by the reactions with H+ in the presence of CH3CN. Alkynyl iridacyclohexadienes [Ir[-CH=CHCH=CHC(=CH-p-C6H4R')](-C[triple chemical bond]CH)(PPh3)2] (8) undergo a cleavage of C[triple chemical bond]C bond by H+/H2O to produce [Ir[-CH=CHCH=CHC(=CH-p-C6H4R')](-CH3)(CO)(PPh3)2] (10) via facile inter-conversion between iridacyclohexadienes and iridabenzenes.     

Building blocks for coordination polymers: self-assembled cleft-like and planar discrete metallo-macrocyclic complexes

Discrete dinuclear metallo-macrocyclic complexes have been prepared from the flexible amide ligand N-6-[(3-pyridylmethylamino)carbonyl]pyridine-2-carboxylic acid (L1-CH(3)), and its more rigid analogue, N-6-[(3-pyridylamino)carbonyl]pyridine-2-carboxylic acid (L3-CH(3)). With ligands L1-CH(3) and L3-CH(3), discrete dinuclear metallo-macrocyclic complexes with the generic formula [Cu(2)(L1-CH(3))(2)(X)(2)(Y)(2)] (7, X = NO(3); 8, X = Cl, Y = H(2)O; 9, X = ClO(4), Y = CH(3)OH) and [Cu(2)(L3-CH(3))(2)(X)(2)(Y)(2)] (10, X = NO(3), Y = H(2)O; 11, X = ClO(4), Y = CH(3)OH) are obtained. For complexes 7-9, containing the more flexible link L1-CH(3), these complexes are cleft-shaped and hinged at the methylene spacer, which allows the cleft to widen and contract to accommodate different packing modes in the solid-state. In contrast, the rigid link L3-CH(3) gives near planar metallo-macrocyclic structures. These metallo-macrocyclic compounds may be useful building blocks for coordination polymers.     

Thermal activation of hydrocarbon C-H bonds initiated by a tungsten allyl complex

Gentle thermolysis of the allyl complex, CpW(NO)(CH(2)CMe(3))(eta(3)-H(2)CCHCMe(2)) (1), at 50 degrees C in neat hydrocarbon solutions results in the loss of neopentane and the generation of transient intermediates that subsequently activate solvent C-H bonds. Thus, thermal reactions of 1 with tetramethylsilane, mesitylene, and benzene effect single C-H activations and lead to the exclusive formation of CpW(NO)(CH(2)SiMe(3))(eta(3)-H(2)CCHCMe(2)) (2), CpW(NO)(CH(2)C(6)H(3)-3,5-Me(2))(eta(3)-H(2)CCHCMe(2)) (3), and CpW(NO)(C(6)H(5))(eta(3)-H(2)CCHCMe(2)) (4), respectively. The products of reactions of 1 with other methyl-substituted arenes indicate an inherent preference of the system for the activation of stronger arene sp(2) C-H bonds. For example, C-H bond activation of p-xylene leads to the formation of CpW(NO)(CH(2)C(6)H(4)-4-Me)(eta(3)-H(2)CCHCMe(2)) (5) (26%) and CpW(NO)(C(6)H(3)-2,5-Me(2))(eta(3)-H(2)CCHCMe(2)) (6) (74%). Mechanistic and labeling studies indicate that the transient C-H-activating intermediates are the allene complex, CpW(NO)(eta(2)-H(2)C=C=CMe(2)) (A), and the eta(2)-diene complex, CpW(NO)(eta(2)-H(2)C=CHC(Me)=CH(2)) (B). Intermediates A and B react with cyclohexene to form CpW(NO)(eta(3)-CH(2)C(2-cyclohexenyl)CMe(2))(H) (18) and CpW(NO)(eta(3)-CH(2)CHC)(Me)CH(2)C(beta)H(C(4)H(8))C(alpha)H (19), respectively, and intermediate A can be isolated as its PMe(3) adduct, CpW(NO)(PMe(3))(eta(2)-H(2)C=C=CMe(2)) (20). Interestingly, thermal reaction of 1 with 2,3-dimethylbut-2-ene results in the formation of a species that undergoes eta(3) --> eta(1) isomerization of the dimethylallyl ligand following the initial C-H bond-activating step to yield CpW(NO)(eta(3)-CMe(2)CMeCH(2))(eta(1)-CH(2)CHCMe(2)) (21). Thermolyses of 1 in alkane solvents afford allyl hydride complexes resulting from three successive C-H bond-activation reactions. For instance, 1 in cyclohexane converts to CpW(NO)(eta(3)-C(6)H(9))(H) (22) with dimethylpropylcyclohexane being formed as a byproduct, and in methylcyclohexane it forms the two isomeric complexes, CpW(NO)(eta(3)-C(7)H(11))(H) (23a,b). All new complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 2, 3, 4, 18, 19, 20, and 21 have been established by X-ray crystallographic analyses.     

Preparation and characterization of an isometallabenzene with the structure of a 1,2,4-cyclohexatriene

The elongated dihydrogen complex [Os{C6H4C(O) CH3}(eta2-H2)(H2O)(PiPr3)2]BF4 reacts with phenylacetylene and HBF4.OEt2 to give the unsaturated compound [Os{(E)-CH=CHPh}(CCPh)(CCH2Ph)(PiPr3)2]BF4 containing alkenyl, alkynyl, and carbyne ligands. The addition of sodium chloride to this compound leads to the cyclic allene Os{=C=C(Ph)CH(Ph)CH=C(CH2Ph)}Cl(PiPr3)2, which is the first isometallabenzene with the structure of a 1,2,4-cyclohexatriene.     

Variation of some microscopic properties with composition in 2-methoxyethanol and 1,2-ethanediol mixtures

Selected microscopic properties, namely E_T(30) polarity, Kamlet-Taft solvatochromic parameters and dissociation constant of picric acid, have been correlated with solvent composition in 2-methoxyethanol/1,2-ethanediol mixtures. Theoretical and semi-empirical equations which embody preferential solvation of the solute and show standard deviations lower than 0.01 for solvatochromic parameters and 0.03 for pK values have been proposed.     

Syntheses and Structural Characterization of Dimethyltin Complexs of N-（3-Methoxysalicylidene）-α-amino Acid

Three new dimethyltin complexes of N-(3-methoxysalicylidene)-α-amino acid,(CH3)2Sn(3-CH3O-2-OC6H3CH=NCHRCOO)(R = H,1;CH3,2;(CH3)2CH,3),have been synthe-sized by treating dimethyltin dichloride with the potassium salt of the ligand and characterized by elemental analysis,IR and 1H NMR spectra.The crystal structure of [(CH3)2Sn(3-CH3O-2-OC6H3CH=NCH2COO)(CH3OH)]2 H2O(1a),formed from methanol solution of 1,has been deter-mined.The crystal belongs to the monoclinic system,space group C/2c with a = 20.636(3),b = 7.8854(9),c = 20.668(2) ,β= 113.265(2)°,V = 3089.7(6) 3,Z = 4,Dc = 1.707 g/cm3,= 1.675 mm-1,F(000) = 1592,R = 0.0301 and wR = 0.0841.In complex 1a,the tin atom is six-coordinate and possesses a distorted [SnC2NO3] octahedral geometry with the two methyl groups occupying the trans positions.The weak Sn O interactions and intermolecular hydrogen bonds connected the molecules into an infinite chain.     

Determination of Kamlet-Taft solvent parameters pi* of high pressure and supercritical water by the UV-Vis absorption spectral shift of 4-nitroanisole

Kamlet-Taft solvent parameters, pi*, of high pressure and supercritical water were determined from 16-420 degrees C based on solvatochromic measurements of 4-nitroanisole. For the measurements, an optical cell that could be used at high temperatures and pressures was developed with the specification of minimal dead space. The low dead space cell allowed us to measure the absorption spectra of 4-nitroanisole at high temperature conditions before appreciable decomposition occurred. The behavior of pi* in terms of water density (pi* = 1.77rho- 0.71) was found to be linear, except in the near critical region, in which deviations were observed that could be attributed to local density augmentation. Excess density, which was defined as the difference between local density and bulk density, showed a maximum near the critical density of water. The frequencies of UV-Vis spectra of 4-(dimethylamino)benzonitrile and N,N-dimethyl-4-nitroaniline were correlated with pi* based on a linear solvation energy relationship (LSER) theory. Local density augmentation around 4-nitroanisole and that around 4-(dimethylamino)benzonitrile were similar but the augmentation observed around N,N-dimethyl-4-nitroaniline was larger.     

Structural diversity of the oxovanadium organodiphosphonate system: a platform for the design of void channels

The hydrothermal reactions of a vanadium source, an appropriate diphosphonate ligand, and water in the presence of HF provide a series of compounds with neutral V-P-O networks as the recurring structural motif. When the {O3P(CH2)(n)PO3}4- diphosphonate tether length n is 2-5, metal-oxide hybrids of type 1, [V2O2(H2O){O3P(CH2)(n)PO3}] x xH2O, are isolated. The type 1 oxides exhibit the prototypical three-dimensional (3-D) "pillared" layer architecture. When n is increased to 6-8, the two-dimensional (2-D) "pillared" slab structure of the type 2 oxides [V2O2(H2O)4{O3P(CH2)6PO3}] is encountered. Further lengthening of the spacer to n = 9 provides another 3-D structure, type 3, constructed from the condensation of pillared slabs to give V-P-O double layers as the network substructure. When organic cations are introduced to provide charge balance for anionic V-P-O networks, oxides of types 4-7 are observed. For spacer length n = 3, a range of organodiammonium cations are accommodated by the same 3-D "pillared" layer oxovanadium diphosphonate framework in the type 4 materials [H3N(CH2)(n)NH3][V4O4(OH)2 {O3P(CH)3PO3}2] x xH2O [n = 2, x = 6 (4a); n = 3, x = 3 (4b); n = 4, x = 2 (4c); n = 5, x = 1 (4d); n = 6, x = 0.5 (4e); n = 7, x = 0 (4f)] and [H3NR]y[V4O4(OH)2 {O3P(CH)3PO3}2] x xH2O [R = -CH2(NH3)CH2CH3, y = 1, x = 0 (4g); R = -CH3, n = 2, x = 3 (4h); R = -CH2CH3, y = 2, x = 1 (4i); R = -CH2CH2CH3, y = 2, x = 0 (4j); cation = [H2N(CH2CH3)2], y = 2, x = 0 (4k)]. These oxides exhibit two distinct interlamellar domains, one occupied by the cations and the second by water of crystallization. Furthermore, as the length of the cation increases, the organodiammonium component spills over into the hydrophilic domain to displace the water of crystallization. When the diphosphonate tether length is increased to n = 5, structure type 5, [H3N(CH2)2NH3][V4O4(OH)2(H2O){O3P(CH2)5PO3}2] x H2O, is obtained. This oxide possesses a 2-D "pillared" network or slab structure, similar in gross profile to that of type 2 oxides and with the cations occupying the interlamellar domain. In contrast, shortening the diphosphonate tether length to n = 2 results in the 3-D oxovanadium organophosphonate structure of the type 7 oxide [H3N(CH2)5NH3][V3O3{O3P(CH2)2PO3}2]. The ethylenediphosphonate ligand does not pillar V-P-O networks in this instance but rather chelates to a vanadium center in the construction of complex polyhedral connectivity of 7. Substitution of piperazinium cations for the simple alkyl chains of types 4, 5, and 7 provides the 2-D pillared layer structure of the type 6 oxides, [H2N(CH2CH2)NH2][V2O2{O3P(CH)(n)PO3H}2] [n = 2 (6a); n = 4 (6b); n = 6 (6c)]. The structural diversity of the system is reflected in the magnetic properties and thermal behavior of the oxides, which are also discussed.     

Synthesis and structures of the C5Me4SiMe3-supported polyhydride complexes over the full size range of the rare earth series

The acid-base reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] with Cp'H gave the corresponding half-sandwich rare earth dialkyl complexes [(Cp')Ln(CH(2)SiMe(3))(2)(thf)] (1-Ln: Ln=Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; Cp'=C(5)Me(4)SiMe(3)) in 62-90% isolated yields. X-ray crystallographic studies revealed that all of these complexes adopt a similar overall structure, in spite of large difference in metal-ion size. In most cases, the hydrogenolysis of the dialkyl complexes in toluene gave the tetranuclear octahydride complexes [{(Cp')Ln(μ-H)(2)}(4)(thf)(x)] (2-Ln: Ln=Sc, x=0; Y, x=1; Er, x=1; Tm, x=1; Gd, x=1; Dy, x=1; Ho, x=1) as the only isolable product. However, in the case of Lu, a trinuclear pentahydride [(Cp')(2)Lu(3)(μ-H)(5)(μ-CH(2)SiMe(2)C(5)Me(4))(thf)(2)] (3), in which the C-H activation of a methyl group of the Me(3)Si unit on a Cp' ligand took place, was obtained as a major product (66% yield), in addition to the tetranuclear octahydride [{(Cp')Lu(μ-H)(2)}(4)(thf)] (2-Lu, 34%). The use of hexane instead of toluene as a solvent for the hydrogenolysis of 1-Lu led to formation of 2-Lu as a major product (85%), while a similar reaction in THF yielded 3 predominantly (90%). The tetranuclear octahydride complexes of early (larger) lanthanide metals [{Cp'Ln(μ-H)(2)}(4)(thf)(2)] (2, Ln=La, Ce, Pr, Nd, Sm) were obtained in 38-57% isolated yields by hydrogenolysis of the bis(aminobenzyl) species [Cp'Ln(CH(2)C(6)H(4)NMe(2)-o)(2)], which were generated in-situ by reaction of [Ln(CH(2)C(6)H(4)NMe(2)-o)(3)] with one equivalent of Cp'H. X-ray crystallographic studies showed that the fine structures of these hydride clusters are dependent on the size of the metal ions.     

Diketo compounds with (trifluoromethyl)trimethylsilane: double nucleophilic trifluoromethylation reactions

Reactions of various diketo compounds with (trifluoromethyl)trimethylsilane (Me3SiCF3) in the presence of catalytic amounts of cesium fluoride have been studied. gamma-Ketoesters, CH3COCH2CH2CO2R (R = Et, Bu), were reacted with 2 equiv of Me3SiCF3 at room temperature to give CH3C(OH)(CF3)CH2CH2COCF3 in good yield after hydrolysis. alpha-Diketones, R1COCOR2 (R1 = R2 = Ph; R1 = Ph, R2 = Me; R1 = R2 = Me; R1 = Me, R2 = Et), when reacted with Me3SiCF3, formed 1:1 or 1:2 addition products depending on the reaction conditions and stoichiometry used. Reactions of diones CH3COXCOCH3 (X = -CH2CH2-, -C6H4C6H4-, -CH2-) with Me3SiCF3 also led to the formation of the mono- or diaddition products depending on reaction conditions. With various kinds of substituted arylglyoxals, 2 equiv of Me3SiCF3 produced monoaddition products in 70-75% yield and diaddition products in 5-10% yield. One of the monoalcohols and two of the diols have been characterized by single-crystal X-ray analysis, and the presence of inter- and intramolecular hydrogen bonding has been confirmed.     

Synthesis, characterization and ethylene reactivity of 2-diphenylphosphanylbenzamido nickel complexes

Addition of primary amines to N-[2-(diphenylphosphanyl)benzoyloxy]succinimide affords 2-diphenylphosphanylbenzamides, Ph2PC6H4C(O)NHR (R = C(CH3)3, 3; R = H, 4; R = CH2CH2CH3, 5; R = CH(CH3)2, 6). Addition of NiCl(eta3-CH2C6H5)(PMe3) to the deprotonated potassium salts of the amides and subsequent treatment of two equivalents of B(C6F5)3 to the resulting products furnishes eta3-benzyl zwitterionic nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta3-CH2C6H5) (R = C6H5, 9; R = C(CH3)3, 10; R = H, 11; R = CH2CH2CH3, 12; R = CH(CH3)2, 13). Solid structures of 9, 11, 13 and the intermediate eta1-benzyl nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta1-CH2C6H5)(PMe3) (R = C6H5, 7; R = C(CH3)3, 8) were determined by X-ray crystallography. When ethylene is added to the eta3-benzyl zwitterionic nickel(II) complexes, butene is obtained by the complexes 9-12 but complex 13 provides very high molecular-weight branched polyethylene (Mw, approximately 1300000) with excellent activity (up to 5200 kg mol-1 h-1 at 100 psi gauge).     

Trans influence of boryl ligands and comparison with C, SI, and SN ligands

In this paper, the trans influence of boryl ligands, together with that of other ligands commonly believed to have a strong trans influence, has been investigated theoretically via density functional theory (DFT) calculations on a series of square-planar platinum(II) complexes of the form trans-[PtL(Cl)(PMe3)2]. The following order of trans influence has been obtained: -BMe2>-SiMe3>-BH2>-SnMe3 approximately >-Bpin> approximately -Bcat approximately -BCl2 approximately -BBr2 approximately -SiH3>-CH2CH3>-CH=CH2>-H approximately -Me>-C6H5>-SiCl3>-SnCl3>-CCH. Natural bond order analyses have been used to understand how the substituents at the boron center affect the trans-influence properties of the boryl ligands. The major factor is the sigma-donor strength of the boryl ligand. However, surprisingly, very strong pi acceptors also enhance the trans influence.     

Redox energetics of hypercloso boron hydrides B(n)H(n) (n = 6-13) and B12X12 (X = F, Cl, OH, and CH3)

The reduction potentials (E°(Red) versus SHE) of hypercloso boron hydrides B(n)H(n) (n = 6-13) and B(12)X(12) (X = F, Cl, OH, and CH(3)) in water have been computed using the Conductor-like Polarizable Continuum Model (CPCM) and the Solvation Model Density (SMD) method for solvation modeling. The B3LYP/aug-cc-pvtz and M06-2X/aug-cc-pvtz as well as G4 level of theory were applied to determine the free energies of the first and second electron attachment (ΔG(E.A.)) to boron clusters. The solvation free energies (ΔG(solv)) greatly depend on the choice of the cavity set (UAKS, Pauling, or SMD) while the dependence on the choice of exchange/correlation functional is modest. The SMD cavity set gives the largest ΔΔG(solv) for B(n)H(n)(0/-) and B(n)H(n)(-/2-) while the UAKS cavity set gives the smallest ΔΔG(solv) value. The E°(Red) of B(n)H(n)(-/2-) (n = 6-12) with the G4/M06-2X(Pauling) (energy/solvation(cavity)) combination agrees within 0.2 V of experimental values. The experimental oxidative stability (E(1/2)) of B(n)X(n)(2-) (X = F, Cl, OH, and CH(3)) is usually located between the values predicted using the B3LYP and M06-2X functionals. The disproportionation free energies (ΔG(dpro)) of 2B(n)H(n)(-) → B(n)H(n) + B(n)H(n)(2-) reveal that the stabilities of B(n)H(n)(-) (n = 6-13) to disproportionation decrease in the order B(8)H(8)(-) > B(9)H(9)(-) > B(11)H(11)(-) > B(10)H(10)(-). The spin densities in B(12)X(12)(-) (X = F, Cl, OH, and CH(3)) tend to delocalize on the boron atoms rather than on the exterior functional groups. The partitioning of ΔG(solv)(B(n)H(n)(2-)) over spheres allows a rationalization of the nonlinear correlation between ΔG(E.A.) and E°(Red) for B(6)H(6)(-/2-), B(11)H(11)(-/2-), and B(13)H(13)(-/2-).     

Temperature-/solvent-dependent low-dimensional compounds based on quinoline-2,3-dicarboxylic acid: Structures and fluorescent properties

A series of 0-D, 1-D, and 2-D metal-organic compounds through reactions of quinoline-2,3-dicarboxylic acid (2,3-H(2)qldc) with transition metal salts MCl(2), namely, M(2,3-Hqldc)(2)(H(2)O)(2) (M = Co(1), Zn(4) and Cd(7)), [M(3-qlc)(2)(H(2)O)(2)](n) (M = Co(2), Zn(5) and Cd(8)), M(2-qldc-3-OCH(3))(2)(CH(3)OH)(2) (M = Co(3) and Zn(6)) and [Cd(2,3-qldc-OCH(3))(μ(2)-Cl)](2n) (9) (where, 3-Hqlc = quinoline-3-carboxylic acid and 2-qldc-3-OCH(3) = 3-(methoxycarbonyl)quinoline-2-carboxylic acid), were synthesized and characterized by elemental analysis, IR, thermogravimetric analysis (TG), and single-crystal X-ray diffraction. When the temperature ranged from room temperature to 70 °C, three isomorphous mononuclear complexes 1, 4 and 7 were obtained in H(2)O/H(2)O + CH(3)OH. As the temperature rose further to above 90 °C, due to the decomposition of 2-position carboxyl group in ligand 2,3-H(2)qldc, the same reactions, respectively, produced three isomorphous 2-D layer-like structures 2, 5 and 8 with 4(4) topology in water. By contrast, when the mixed solvent of H(2)O + CH(3)OH at a 1?:?1 ratio (v/v) was applied, the three above-mentioned reactions respectively gave compounds 3, 6 and 9 with the 3-position esterification of 2,3-H(2)qldc. Compounds 3 and 6 are mononuclear and isomorphous, while complex 9 has a 1-D double-stranded chain-like structure connected by two μ(2)-Cl bridges. Obviously, these results reveal that the reaction temperature and solvent play a critical role in structural direction of these low-dimensional compounds. Meanwhile, the photoluminescent property of the selected compounds is also investigated.     

Generation of fullerenyl cation (EtO)2P+(OH)CH2-C60+ from RC60-H and from RC60-C60R (R = CH2P(O)(OEt)2)

A novel fullerenyl cation (EtO)2P+(OH)CH2-C60+ was generated by simply dissolving the monofunctionalized hydrofullerene RC60-H or singly bonded dimer RC60-C60R (R = CH2P(O)(OEt)2) in oxidizing acids such as H2SO4 and FSO3H. The cation was also formed in CH2Cl2 by one-electron oxidation with aminium radical cation and was used for further functionalization of C60.