Trinuclear silver(I) complexes of fluorinated pyrazolates

Silver pyrazolates [[3-(CF3)Pz]Ag]3, [[3-(CF3),5-(CH3)Pz]Ag]3, [[3-(CF3),5-(Ph)Pz]Ag]3, [[3-(CF3),5-(But)Pz]Ag]3, and [[3-(C3F7),5-(But)Pz]Ag]3 have been synthesized by treatment of the corresponding pyrazole with a slight molar excess of silver(I) oxide. This economical and convenient route gives silver pyrazolates in high (>80%) yields. X-ray crystal structures of [[3-(CF3),5-(CH3)Pz]Ag]3, [[3-(CF3),5-(But)Pz]Ag]3, and [[3-(C3F7),5-(But)Pz]Ag]3 show that these molecules have trinuclear structures with essentially planar to highly distorted Ag3N6 metallacycles. [[3-(CF3),5-(CH3)Pz]Ag]3 forms extended columns via intertrimer argentophilic contacts (the closest Ag...Ag separation between the neighboring trimers are 3.355 and 3.426 A). The trinuclear [[3-(CF3),5-(But)Pz]Ag]3 units crystallize in pairs, basically forming "dimers of trimers", with the six silver atom core of the adjacent trimers adopting a chair conformation. However, in these dimers of trimers, even the shortest intertrimer Ag...Ag distance (3.480 A) is slightly longer than the van der Waals contact of silver (3.44 A). [[3-(C3F7),5-(But)Pz]Ag]3, which has two bulky groups on each pyrazolyl ring, shows no close intertrimer Ag...Ag contacts (closest intertrimer Ag...Ag distance = 5.376 A). The Ag-N bond distances and the intratrimer Ag...Ag separations of the silver pyrazolates do not show much variation. However, their N-Ag-N angles are sensitive to the nature (especially, the size) of substituents on the pyrazolyl rings. The pi-acidic [[3,5-(CF3)2Pz]Ag]3 and [[3-(C3F7),5-(But)Pz]Ag]3 form adducts with the pi-base toluene. X-ray data show that they adopt extended columnar structures of the type [[Ag3]2.[toluene]]infinity and [[Ag3]'.[toluene]]infinity ([[3,5-(CF3)2Pz]Ag]3 = [Ag3],[[3-(C3F7),5-(But)Pz]Ag]3 = [Ag3]'), in which toluene interleaves and makes face-to-face contacts with [[3-(C3F7),5-(But)Pz]Ag]3 or dimers of [[3,5-(CF3)2Pz]Ag]3.     

Intertrimer and intratrimer metallophilic and excimeric bonding in the ground and phosphorescent States of trinuclear coinage metal pyrazolates: a computational study

The interactions present in cyclic trinuclear coinage metal pyrazolates were studied computationally. Cuprophilic interaction was found to bind the singlet ground state of the dimer of trimers [[Cu(Pz)](3)](2), overcoming electrostatic repulsion. The large variation in intertrimer separations found in the literature for coinage metal pyrazolates is consistent with the relatively weak metallophilic interaction. The emissive triplet excited-state geometry of [[M(Pz)](3)](2) is predicted by density functional calculations to show major geometric distortion caused by Jahn-Teller instability and excimeric M-M bonding. Large calculated Stokes' shifts, which are also observed for experimental models, are consistent with significant excited-state distortions for these materials. The major finding derived from the present study is that the intertrimer M...M contraction in the emissive T(1) state is much more than the intratrimer contraction in all [[M(Pz)](3)](2) models, giving rise to a lower T(1) --> S(0) phosphorescence energy in these models than in analogous monomer-of-trimer models. The observations made here point to a great potential for rationally tuning the emission properties of trinuclear coinage metal complexes through choice of the metal and ligands.     

Brightly phosphorescent trinuclear copper(I) complexes of pyrazolates: substituent effects on the supramolecular structure and photophysics

Synthetic details, solid-state structures, and photophysical properties of a group of trimeric copper(I) complexes containing pyrazolate ligands are described. The reaction of copper(I) oxide and the fluorinated pyrazoles [3-(CF(3))Pz]H, [3-(CF(3)),5-(Me)Pz]H, and [3-(CF(3)),5-(Ph)Pz]H leads to the corresponding trinuclear copper(I) pyrazolates, {[3-(CF(3))Pz]Cu}(3), {[3-(CF(3)),5-(Me)Pz]Cu}(3), and {[3-(CF(3)),5-(Ph)Pz]Cu}(3), respectively, in high yield. The {[3,5-(i-Pr)(2)Pz]Cu}(3) compound was obtained by a reaction between [Cu(CH(3)CN)(4)][BF(4)], [3,5-(i-Pr)(2)Pz]H, and NEt(3). These compounds as well as {[3,5-(Me)(2)Pz]Cu}(3) and {[3,5-(CF(3))(2)Pz]Cu}(3) adopt trimeric structures with nine-membered Cu(3)N(6) metallacycles. There are varying degrees and types of intertrimer Cu...Cu interactions. These contacts give rise to zigzag chains in the fluorinated complexes, {[3-(CF(3))Pz]Cu}(3), {[3-(CF(3)),5-(Me)Pz]Cu}(3), {[3-(CF(3)),5-(Ph)Pz]Cu}(3), and {[3,5-(CF(3))(2)Pz]Cu}(3), whereas the nonfluorinated complexes, {[3,5-(Me)(2)Pz]Cu}(3) and {[3,5-(i-Pr)(2)Pz]Cu}(3) form dimers of trimers. Out of all the compounds examined in this study, {[3-(CF(3)),5-(Ph)Pz]Cu}(3) has the longest (3.848 Angstroms) and {[3,5-(Me)(2)Pz]Cu}(3) has the shortest (2.946 Angstroms) next-neighbor intertrimer Cu...Cu distance. The Cu...Cu separations within the trimer units do not vary significantly (typically 3.20-3.26 Angstroms). All of these trinuclear copper(I) pyrazolates show bright luminescence upon exposure to UV radiation. The luminescence bands are hugely red-shifted from the corresponding lowest-energy excitations, rather broad, and unstructured even at low temperatures, suggesting metal-centered emissions owing to intertrimer Cu...Cu interactions that are strengthened in the phosphorescent state. The {[3-(CF(3)),5-(Ph)Pz]Cu}(3) compound exhibits an additional highly structured phosphorescence with a vibronic structure corresponding to the pyrazolyl (Pz) ring. The luminescence properties of solids and solutions of the trimeric compounds in this study show fascinating trends with dramatic sensitivities to temperature, solvent, concentration, and excitation wavelengths.     

Blue phosphors of dinuclear and mononuclear copper(I) and silver(I) complexes of 3,5-bis(trifluoromethyl)pyrazolate and the related bis(pyrazolyl)borate

The synthesis, structure, and photoluminescence properties are described for the three-coordinate mononuclear and dinuclear complexes [H(2)B(3,5-(CF(3))(2)Pz)(2)]M(2,4,6-collidine), M(1)(), and [[3,5-(CF(3))(2)Pz]M(2,4,6-collidine)](2), M(2)(), respectively (M = Cu; Ag). The solids exhibit bright blue phosphorescence, at room temperature for the copper compounds and at 77 K for all compounds. Ag(1)(), Cu(1)(), and Cu(2)() exhibit blue pyrazole-based structured emissions with short phosphorescence lifetimes, 10(1)-10(2) micros, due to an internal heavy-metal effect. Meanwhile, Ag(2)() exhibits curious multiple excitation-dependent emissions.     

Bright phosphorescence of a trinuclear copper(I) complex: luminescence thermochromism, solvatochromism, and "concentration luminochromism"

A photophysical study is reported for the trinuclear copper(I) complex {[3,5-(CF3)2Pz]Cu}3. The neutral compound exhibits multicolor bright phosphorescent emissions both in the solid state and in solution. The emission can be tuned to multiple visible colors by controlling the temperature, solvent, and {[3,5-(CF3)2Pz]Cu}3 concentration, giving rise to luminescence thermochromism, luminescence solvatochromism, and a new optical phenomenon called "concentration luminochromism", respectively.     

Neutral Cu4N12 and Ag4N12 metallacycles with a para-cyclophane framework assembled from copper(I) and silver(I) pyrazolates and pyridazine

Trinuclear copper(I) and silver(I) pyrazolates {[3,5-(CF3)2Pz]M}3 (M = Cu and Ag) react with pyridazine to give neutral, tetranuclear metallacycles with a para-cyclophane core whereas benzo[c]cinnoline fails to break the cyclic pyrazolate trimers under similar conditions, and affords a metalla-propellane featuring both two- and three-coordinate metal sites.     

Structures of silver pyrazolates in hydrocarbon solutions via vapor-pressure osmometry

Molecular weights of {[3,5-(CF 3) 2Pz]Ag} 3, {[3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, and {[3,5-( i-Pr) 2Pz]Ag} 3 at various solution concentrations have been investigated using vapor-pressure osmometry. Depending on the concentration, the trinuclear {[3,5-(CF 3) 2Pz]Ag} 3 either dissociates into mono- and dinuclear moieties or remains trinuclear or aggregates to hexanuclear species in toluene. In contrast, {[3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, which has a bulky and relatively electron-rich pyrazolate, retains the trinuclear form even at low concentrations in toluene. Both {[3,5-(CF 3) 2Pz]Ag} 3 and {[3,5-( i-Pr) 2Pz]Ag} 3 adopt trinuclear structures in heptane at low concentrations. At higher concentrations, {[3,5-( i-Pr) 2Pz]Ag} 3 forms hexanuclear species. The aggregation-segregation points are rather sharp and are reminiscent of the all-or-none character of phase transitions. Remarkably, at higher concentrations, the aggregation states of these silver pyrazolates are similar to those expected based on solid-state data.     

Coinage metal complexes of tris(pyrazolyl)methanide [C(3,5-Me2pz)3]-: kappa3-coordination vs. backbone functionalisation

Tris(pyrazolyl)methanides, [C(3,5-R2pz)3]-, contain an unassociated tetrahedral carbanionic centre in the bridgehead position. In addition to nitrogen donor centres for transition metal coordination, an accessible reactive site for further manipulations is available in the backbone of the ligand. The coordination variability of the ambidental C-/N ligand [C(3,5-Me2pz)3]- was elucidated by investigating its coinage metal complexes. Two principle coordination modes were found for complexes of general formula [LMPR3] (with M = Cu(I), Ag(I), Au(I); L =[C(3,5-Me2pz)3]-; R = Ph, OMe). While for Cu(I) (2,3) and Ag(I) (4) complexes the anionic ligand acts as a face-capping, six electron N3-donor, gold(I) (5) is coordinated by the bridging carbanion yielding a two coordinate Au(I) complex comprising a covalent Au-C bond. The complexes featuring the kappa3-coordinated N3-donor ligand were investigated by 31P CP (MAS) NMR in the solid state.     

Copper and silver complexes containing organic azide ligands: syntheses, structures, and theoretical investigation of [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) and [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN (where Pz = pyrazolyl and 1-Ad = 1-adamantyl)

Treatment of [HB(3,5-(CF3)2Pz)3]Na(THF) with CF3SO3Cu followed by 1-azidoadamantane affords [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) in 65% yield. The solid state structure shows that the copper atom is coordinated to the terminal nitrogen atom (NT) of the azidoadamantane ligand. The related silver(I) adduct can be prepared in 80% yield by the treatment of [HB(3,5-(CF3)2Pz)3]Ag(THF) with 1-azidoadamantane. However, [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN shows a different bonding mode where the silver atom coordinates to the alkylated nitrogen atom (NA) of the azidoadamantane ligand. Asymmetric stretching bands of the azido group for copper and silver adducts appear at 2143 and 2120 cm-1, respectively. Theoretical investigation shows that steric effects do not play a dominant role in determining the bonding mode of the azide ligand in these two metal complexes. Although the copper(I) ion affinity for the two coordinating sites NT and NA is nearly identical, copper-azide back-bonding interactions favor the copper-NT mode of bonding over the copper-NA mode. Silver (a very poor back-bonding metal) prefers the NA site for coordination. The NA site has a significantly higher proton affinity and slightly higher sodium ion affinity. Important structural parameters for [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) and [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN are as follows: Cu-NT 1.861(3) A, NT-N 1.136(4) A, N-NA 1.219(4) A, NT-N-NA 173.1(3) degrees; Ag-NA 2.220(5) A, NT-N 1.143(12) A, N-NA 1.227(10) A, NT-N-NA 176.8(12) degrees. Overall, the azidoadamantane ligand does not undergo any significant changes upon coordination to Cu(I) or Ag(I) ions.     

Heteropolynuclear complexes with the ligand Ph2PCH2SPh: theoretical evidence for metallophilic Au-M attractions

Addition of two equivalents of diphenylthiomethylphosphine (PPh2-CH2SPh) to the starting materials [Au(tht)2]A (tht = tetrahydrothiophene), AgCF3SO3, or [Cu(CH3CN)4]CF3SO3 produces the mononuclear derivatives [M(PPh2CH2SPh)2]A (M = Au, A = CF3SO3 (1a); M = Au, A = ClO4 (1b); M = Ag, A = CF3SO3 (4); M = Cu, A = CF3SO3 (5)) which are able to form the heterodinuclear complexes [AuM'(PPh2CH2SPh)2](CF3SO3)2 (M' = Ag (2), Cu (3)) with a P-Au-P environment. If the starting gold complex is [Au(C6F5)(tht)], reaction with the phosphine produces [Au(C6F5)-(PPh2CH2SPh)] (6) from which, by reaction with AgCF3SO3 or [Cu(CH3CN)4]CF3SO3, the "snake"-type linear complexes [Au2M(C6F5)2-(PPh2CH2SPh)2]CF3SO3 (M = Ag (7), Cu (8)) are obtained. If the silver starting complex is AgCF3CO2, reaction in a 1:1 ratio gives the tetranuclear complex [Au2Ag2(C6F5)2(PPh2CH2SPh)2-(CF3CO2)2] (9). When the molar ratio is 1:2 the trinuclear complex [AuAg2(C6F5) (CF3CO2)2(PPh2CH2SPh)] (10) is obtained. According to ab initio calculations, the presence of only one gold atom is enough to induce metallophilic attractions in the group congeners, and this effect can be modulated depending on the gold ligand.     

Low-valent gallium, indium, and tin compounds that contain a highly fluorinated tris(pyrazolyl)borate ligand: syntheses and characterization of

Syntheses and characterization of gallium(I), indium(I), and tin(II) complexes of the [HB(3,5-(CF3)2Pz)3]- ligand (where [HB(3,5-(CF3)2Pz)3]- = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate)) are reported. X-ray crystal structures of [HB(3,5-(CF3)2Pz)3]In and [HB(3,5-(CF3)2Pz)3]Sn(CF3SO3) show monomeric structures in the solid state. The In-N and Sn-N bond distances are longer than the corresponding bond distances of nonfluorinated analogues. NMR data of the gallium(I) adduct [HB(3,5-(CF3)2Pz)3]Ga are very similar to those of the indium(I) analogue suggesting similar solution structures.     

Peculiarities of the complexation of copper and silver adducts of a 3,5-bis(trifluoromethyl)pyrazolate ligand with organoiron compounds

Interaction of the copper, {[3,5-(CF(3))(2)Pz]Cu}(3), and silver, {[3,5-(CF(3))(2)Pz]Ag}(3), macrocycles [3,5-(CF(3))(2)Pz = 3,5-bis(trifluoromethyl)pyrazolate] with cyclooctatetraeneiron tricarbonyl, (cot)Fe(CO)(3), was investigated by IR and NMR spectroscopy for the first time. The formation of 1:1 complexes was observed at low temperatures in hexane. The composition of the complexes (1:1) and their thermodynamic characteristics in hexane and dichloromethane were determined. The π-electron system of (cot)Fe(CO)(3) was proven to be the sole site of coordination in solution and in the solid state. However, according to the single-crystal X-ray data, the complex has a different (2:1) composition featuring the sandwich structure. The complexes of ferrocene with copper and silver macrocycles have a columnar structure (X-ray data).     

Investigation of silver salt metathesis: preparation of cationic germanium(II) and Tin(II) complexes,and silver adducts containing unsupported silver-germanium and silver-tin bonds

Syntheses of halide derivatives of germanium(II) and tin(II) aminotroponiminate (ATI) complexes and their silver salt metathesis reactions have been investigated. The treatment of GeCl(2) x (1,4-dioxane), SnCl(2), or SnI(2) with [(n-Pr)(2)ATI]Li in a 1:1 molar ratio affords the corresponding germanium(II) or tin(II) halide complex [(n-Pr)(2)ATI]MX (where [(n-Pr)(2)ATI](-) = N-(n-propyl)-2-(n-propylamino)troponiminate; M = Ge or Sn; X = Cl or I). As usually expected, [(n-Pr)(2)ATI]GeCl and [(n-Pr)(2)ATI]SnCl undergo rapid metathesis with CF(3)SO(3)Ag, leading to trifluoromethanesulfonate salts, [[(n-Pr)(2)ATI]Ge][SO(3)CF(3)] and [[(n-Pr)(2)ATI]Sn][SO(3)CF(3)], and silver chloride. However, when the silver source [HB(3,5-(CF(3))(2)Pz)(3)]Ag(eta(2)-toluene) is used, rather than undergoing metathesis, very stable 1:1 adducts [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Ge(Cl)[(n-Pr)(2)ATI] and [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(Cl)[(n-Pr)(2)ATI] are formed (where [HB(3,5-(CF(3))(2)Pz)(3)](-) = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate). The use of the iodide derivative [(n-Pr)(2)ATI]SnI did not change the outcome either. All new compounds have been characterized by multinuclear NMR spectroscopy and X-ray crystallography. The Ag-Ge and Ag-Sn bond distances of [HB(3,5-(CF(3))(2)Pz)(3)]Ag<-- Ge(Cl)[(n-Pr)(2)ATI], [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(Cl)[(n-Pr)(2)ATI], and [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(I)[(n-Pr)(2)ATI] are 2.4142(6), 2.5863(6), and 2.5880(10) A, respectively. A convenient route to [(n-Pr)(2)ATI]H is also reported.     

Synthesis, characterization and olefin/CO exchange reactions of pyrazolylborato complexes of copper(I)

New bis(pyrazolyl)borato olefin complexes of copper(I) of general formula Cu[BH2(3,5-(CF3)2Pz)2](olefin) have been prepared (olefins: coe = cyclooctene, van = 4-vinylanisole, clsty = 4-chlorostyrene, tevs = triethylvinylsilane, fn = fumaronitrile). The structures of Cu[BH2(3,5-(CF3)2Pz)2](L), L = coe, van, tevs, fn, have been determined by X-ray diffraction methods. Considering the two N atoms of the bis(pyrazolyl)borate ligand and the midpoint of the C-C double bond of the coordinated olefin, the compounds with L = coe, van and tevs contain a copper atom in a trigonal planar coordination. A coordination polymer with N-coordinated fumaronitrile and tetrahedral coordination of copper atoms is obtained in the case of L = fn. The carbonylation reactions of Cu[BH(2)(3,5-(CF3)2Pz)2](olefin) (olefin = coe, clsty, van, tevs), Cu[BH2(3,5-(CF3)2Pz)2](olefin) + CO<==>Cu[BH2(3,5-(CF3)2Pz)2](CO) + olefin, have been studied gas volumetrically and the thermodynamical parameters of the equilibria for the displacement of the coordinated olefin by carbon monoxide have been determined. These data for copper(I) are compared with those reported in the literature.     

Gold derivatives of scorpionates: comparison with the other coinage metal poly(pyrazolyl)borate analogues

Gold derivatives [Au(Tpx)(PR3)](Tpx = Tp, hydrotris(pyrazol-1-yl)borate or Tp*, hydrotris(3,5-dimethylpyrazol-1-yl)borate; R = Ph or tBu) and [Au(pzTp)(PR3)x](pzTp = tetrakis(pyrazol-1-yl)borate, x = 1 or 2, R = Ph or tBu) have been synthesised and characterized both in solution (1H- and 31P[1H]-NMR) and in the solid state (IR, single crystal X-ray structure analysis, 31P CPMAS). 31P [1H] NMR solution data suggest greater stability of the tetrakis(pyrazolyl)borate relative to those of tris(pyrazolyl)borate. All compounds are fluxional at room temperature. In order to compare [Au(Tp*)(PPh3)] with analogous coinage metal adducts we have synthesized and structurally characterized [Cu(Tp*)(PPh3)] x PPh3 and [Ag(Tp*)(PPh3)] x 2MeCN. In [Au(Tp*)(PPh3)] the gold atom adopts a distorted tetrahedral geometry with 2.181(5) and 2.37(2) angstroms (cf. 2.166(6), 2.098(1) in [Cu(Tp*)PPh3], 2.156(2), 2.075(7) in [Cu(Tp*)(PPh3)] x PPh3; and in [Ag(Tp*)PPh3] x MeCN 2.347(12), 2.35(5) angstroms). There are three independent [Au(Tp*)(PPh3)] molecules in the asymmetric unit of the structure with their PAu...B axes lying on the cell diagonal of a cubic P213 cell, two with the same chirality aligned opposed in direction to the third which is of opposite chirality. A number of Cu, Ag and Au complexes containing scorpionate ligands have also been investigated by 31P cross-polarization magic-angle-spinning (CPMAS) NMR spectroscopy.     

A green approach to the preparation of triangular silver(I) 3,5-bis(trifluoromethyl)pyrazolate: crystal structures of two adducts with triethylammonium nitrate or benzoic acid

Transition Metal Chemistry - An improved procedure is described herein for the synthesis of triangular Ag(I) 3,5-bis(trifluoromethyl)pyrazolate ({[3,5-(CF3)2Pz]Ag}3), which involves initial...     

Synthesis and coordination chemistry of an alkyne functionalised bis(pyrazolyl)methane ligand

The alkyne functionalised bidentate N-donor ligand (2-propargyloxyphenyl)bis(pyrazolyl)methane was prepared in high yield from the reaction of (2-hydroxyphenyl)bis(pyrazolyl)methane with propargyl bromide in the presence of base. A series of transition-metal complexes including [MCl2] (M=Cu, Co, Ni, Zn, Pt), [M2](NO3)2 (M=Cu, Co, Ni, Zn), [Ag]NO3 and [Pd(dppe)](OTf)2 were prepared and characterised by spectroscopic techniques. In addition, ligand as well as the Co(II) and Zn(II) complexes [CoCl2]2, [ZnCl2] were structurally characterized by single-crystal X-ray diffraction. The organometallic gold(I) and platinum(II) acetylide complexes [Pz2CH(C6H(4)-2-OCH2C[triple bond, length as m-dash]CAuPPh3)] and trans-[{Pz2CHC6H(4)-2-OCH2C[triple bond, length as m-dash]C}2Pt(PPh3)2] were prepared from and [AuCl(PPh3)] and trans-[PtCl2(PPh3)2], respectively. Treatment of these complexes with [Pd(OTf)2(dppe)] or [Cu(MeCN)4]PF6 results in formation of the cationic, mixed-metal complexes, which were isolated (Pt/Pd, Au/Pt) or detected by electrospray mass spectrometry (Au/Cu, Pt/Cu).     

Adduct formation or metathesis reactions of silver complexes containing the fluorinated ligands [HB(3,5-(CF3)2Pz)3]- and [CF3SO3]-: formation of silver adducts containing unsupported silver-germanium bonds

A mixture of [HB(3,5-(CF3)2Pz)3]Ag(eta 2-toluene) and [(Me)2ATI]GeCl in CH2Cl2, rather than undergoing metathesis, formed a 1:1 adduct [HB(3,5-(CF3)2Pz)3]Ag<--GeCl[(Me)2ATI] (1, where [HB(3,5-(CF3)2Pz)3] = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate and [(Me)2ATI] = N-methyl-2-(methylamino)troponiminate) featuring a silver-germanium bond. Solutions of 1 (in CH2Cl2 or toluene) did not precipitate AgCl even after several days. However, it easily underwent metathesis with CF3SO3Ag, leading to the chloride-free product [HB(3,5-(CF3)2Pz)3]Ag<--Ge(OSO2CF3)[(Me)2ATI] (2). Compounds 1 and 2 were characterized by X-ray crystallography. The Ag-Ge bond distances of 1 and 2 are 2.4215(9) and 2.4116(10) A, respectively.     

Rational design of macrometallocyclic trinuclear complexes with superior pi-acidity and pi-basicity

Density functional theory (DFT) has been used to assess the pi-acidity and pi-basicity of metal-organic trimetallic macromolecular complexes of the type [M(mu-L)]3, where M = Cu, Ag, or Au and L = carbeniate, imidazolate, pyridiniate, pyrazolate, or triazolate. The organic compounds benzene, triazole, imidazole, pyrazole, and pyridine were also modeled, and their substituent effects were compared to those of the coinage metal trimers. Our results, based on molecular electrostatic potential surfaces and positive charge attraction energy curves, indicate that the metal-organic macromolecules show superior pi-acidity and -basicity compared to their organic counterparts. Moreover, the metal-organic cyclic trimers are found to exhibit pi-acidity and -basicity that can be systematically tuned both coarsely and finely by judicious variation of the bridging ligand (relative pi-basicity imidazolate > pyridiniate > carbeniate > pyrazolate > triazolate), metal (relative pi-basicity Au > Cu > Ag), and ligand substituents. These computational findings are thus guiding experimental efforts to rationally design novel [M(mu-L)]3 materials for applications in molecular electronic devices that include metal-organic field-effect transistors and light-emitting diodes.