Synthesis and reactivity of ruthenium tetrazolate complexes containing a tris(pyrazolyl)borato (Tp) ligand

Facile ligand substitutions are observed when the neutral ruthenium cyclopropenyl complex (PPh₃)[Ru]-CC(Ph)CHCN (1, [Ru] = Tp(PPh₃)Ru) is treated with MeCN and pyrazole yielding the nitrile substituted ruthenium cyclopropenyl complex (MeCN)[Ru]-CC(Ph)CHCN (4a) and the ruthenium metallacyclic pyrazole complex (C₃H₃NN)[Ru]-CC(Ph)CH₂CN (7a), respectively. The reactions of Me₃SiN₃ with 1, 4a and 7a are investigated. Treatment of 1 with Me₃SiN₃ affords in high yield the cationic N-coordinated nitrile complex {(PPh₃)[Ru]NCCH(Ph)CH₂CN}N₃ (3). Interestingly, the reaction of 4a with Me₃SiN₃ in CH₂Cl₂ in the presence of NH₄PF₆ results in an insertion of four nitrogen atoms into the Ru-C_α bond to form a diastereomeric mixture of the bright yellow zwitterionic tetrazolate complex (MeCN)[Ru]-N₄CCH(Ph)CH₂CN (6a) in a 3:2 ratio. The reaction of 7a with Me₃SiN₃ gives the zwitterionic tetrazolate complex (C₃H₃NNH)[Ru]-N₄CCH(Ph)CH₂CN (9a). The two cationic tetrazolate complexes {(C₃H₃NNH)[Ru]-N₄(R)CCH(Ph)CH₂CN}⁺ (12a, R = CH₃, 12b, R = C₆H₅CH₂) are prepared by electrophilic addition of organic halides to 9a. All of the complexes are identified by spectroscopic methods as well as elemental analysis. Pathways for the synthesis of these compounds are proposed.     

Ligand to ligand charge transfer in (hydrotris(pyrazolyl)borato)(triphenylarsine)copper(I)

Emission and UV-vis absorption spectra of (hydrotris(pyrazolyl)borato)(triphenylarsine)copper(I), (CuTpAsPh3), (hydrotris(pyrazolyl)borato)(triethylamine)copper(I), (CuTpNEt3), and (hydrotris(pyrazolyl)borato)(triphenylphosphine)copper(I), (CuTpPPh3), are reported. The spectra of the arsine complex contain low-energy bands (with a band maximum at 16,500 cm(-1) in emission and a weak shoulder centered at about 25,000 cm(-1) in absorption) that are not present in the corresponding spectra of the amine or phosphine complexes. The lowest energy electronic transition is assigned to ligand to ligand charge transfer (LLCT) with some contribution from the metal. This assignment is consistent with PM3(tm) molecular orbital calculations that show the HOMO to consist primarily of pi orbitals on the Tp ligand (with some metal orbital character) and the LUMO to be primarily antibonding orbitals on the AsPh3 ligand (also with some metal orbital character). The absorption shoulder shows a strong negative solvatochromism, indicative of a reversal or rotation of electric dipole upon excitation, and consistent with a LLCT. The trends in the energies of the electronic transitions and the role of the metal on the LLCT are discussed.     

A family of four-coordinate iron(II) complexes bearing the sterically hindered tris(pyrazolyl)borato ligand Tp(tBu,Me)

A new family of 14‐electron, four‐coordinate iron(II) complexes of the general formula [Tp^tBu,MeFeX] (Tp^tBu,Me is the sterically hindered hydrotris(3‐tert‐butyl‐5‐methyl‐pyrazolyl) borate ligand and X=Cl ( 1 ), Br, I) were synthesized by salt metathesis of FeX₂ with Tp^tBu,MeK. The related fluoride complex was prepared by reaction of 1 with AgBF₄. Chloride 1 proved to be a good precursor for ligand substitution reactions, generating a series of four‐coordinate iron(II) complexes with carbon, oxygen, and sulphur ligands. All of these complexes were fully characterized by conventional spectroscopic methods and most were characterized by single‐crystal X‐ray crystallographic analysis. Magnetic measurements for all complexes agreed with a high‐spin (d⁶, S=2) electronic configuration. The halide series enabled the estimation of the covalent radius of iron in these complexes as 1.24 Å.     

Allylic C-H bond activation and functionalization mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) compounds

Allylic C-H bond oxidative addition reactions, mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) species, provide the first step in a hydrocarbon functionalization sequence. The bond activation products To(M)MH(η(3)-C(8)H(13)) (M = Rh (1), Ir (2)), To(M)MH(η(3)-C(3)H(5)) (M = Rh (3), Ir (4)), and To(M)RhH(η(3)-C(3)H(4)Ph) (5) (To(M) = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) are synthesized by reaction of Tl[To(M)] and the corresponding metal olefin chloride dimers. Characterization of these group 9 allyl hydride complexes includes (1)H-(15)N heteronuclear correlation NMR experiments that reveal through-metal magnetization transfer between metal hydride and the trans-coordinated oxazoline nitrogen. Furthermore, the oxazoline (15)N NMR chemical shifts are affected by the trans ligand, with the resonances for the group trans to hydride typically downfield of those trans to η(3)-allyl and tosylamide. These group 9 oxazolinylborate compounds have been studied to develop approaches for allylic functionalization. However, this possibility is generally limited by the tendency of the allyl hydride compounds to undergo olefin reductive elimination. Reductive elimination products are formed upon addition of ligands such as CO and CN(t)Bu. Also, To(M)RhH(η(3)-C(8)H(13)) and acetic acid react to give To(M)RhH(κ(2)-O(2)CMe) (8) and cyclooctene. In contrast, treatment of To(M)RhH(η(3)-C(3)H(5)) with TsN(3) (Ts = SO(2)C(6)H(4)Me) gives the complex To(M)Rh(η(3)-C(3)H(5))NHTs (10). Interestingly, the reaction of To(M)RhH(η(3)-C(8)H(13)) and TsN(3) yields To(M)Rh(NHTs)(H)OH(2) (11) and 1,3-cyclooctadiene viaβ-hydride elimination and Rh-H bond amination. Ligand-induced reductive elimination of To(M)Rh(η(3)-C(3)H(5))NHTs provides HN(CH(2)CH=CH(2))Ts; these steps combine to give a propene C-H activation/functionalization sequence.     

Reversible binding of dioxygen by the copper(I) complex with tris(2-dimethylaminoethyl)amine (Me6tren) ligand

At low temperatures, the mononuclear copper(I) complex of the tetradentate tripodal aliphatic amine Me(6)tren (Me(6)tren = tris(2-dimethylaminoethyl)amine) [Cu(I)(Me(6)tren)(RCN)](+) first reversibly binds dioxygen to form a 1:1 Cu-O(2) species which further reacts reversibly with a second [Cu(I)(Me(6)tren)(RCN)](+) ion to form the dinuclear 2:1 Cu(2)O(2) adduct. The reaction can be observed using low temperature stopped-flow techniques. The copper superoxo complex as well as the peroxo complex were characterized by resonance Raman spectroscopy. The spectral characteristics and full kinetic and thermodynamic results for the reaction of [Cu(I)(Me(6)tren)(RCN)](+) with dioxygen are reported.     

由柔性双吡唑配体构筑的两个多酸基化合物

利用水热合成方法合成了两个新的Keggin基有机-无机杂化化合物:[Cu(H2bdpm)2(H2PMo12O40)]·3H2O(1)和[Ag(H2bdpm)2Na2(H2O)3(HSi W12O40)]·3H2O(2),并通过元素分析、红外光谱和X-射线单晶衍射方法确定了两个化合物的晶体结构。结构分析表明化合物1属于三斜晶系,P-1空间群,晶胞参数a=12.827(7)nm,b=12.888(7)nm,c=19.345(11)nm,α=80.414(10)°,β=89.761(10)°,γ=78.477(10)°,V=3088.6(3)nm3。化合物2属于三斜晶系,P-1空间群,晶胞参数a=12.958(5)nm,b=12.965(5)nm,c=19.522(7)nm,α=80.731(6)°,β=89.284(6)°,γ=78.047(7)°,V=3166(2)nm3。化合物1展示了一个由Keggin型多酸和[Cu(H2bdpm)2]+亚单元相互连接而形成的一维链结构;化合物2中包含一个Si W12-Na构筑的无机链,而[Ag(H2bdpm)]+亚单元上下交替共价键连到该无机链上,进一步稳固了一维链的结构。标题化合物的光催化降解亚甲基蓝实验表明,目标化合物具有光催化性能,可作为潜在的无机-有机杂化功能材料。     

Synthesis of a macrobicycle incorporating the tris(pyrazolyl)methane ligand

Steric crowding of the 3-position of tris(pyrazolyl)borate and -methane ligands has produced tetrahedral metal complexes with controlled reactivity. As an alternative, we propose to incorporate the tris(pyrazolyl)methane chelate in a macrobicyclic structure in order to create a cavity with well-defined dimensions and shape. Acid-catalyzed equilibration of excess of the new pyrazole 3-(1H-pyrazol-3-yl)benzenemethanethiol acetate with HC(3,5-Me(2)pz)(3) followed by hydrolysis affords a functionalized tris(pyrazolyl)methane, which reacts with 1,3,5-tris(bromomethyl)benzene in K(2)CO(3)/DMF to give the title compound. [structure: see text]     

A novel tetrakis(pyrazolyl)borate ligand bearing triphenylphosphine oxide substituents

A new tetrakis(pyrazolyl)borate ligand bearing triphenylphosphine oxide moieties appended to the 3-position of the pyrazolyl rings is reported and shown to display varied coordination chemistry from tridentate N(2)O coordination with thallium to hexadentate N(3)O(3) coordination with europium.     

Structural and electronic differences of copper(I) complexes with tris(pyrazolyl)methane and hydrotris(pyrazolyl)borate ligands

Copper(I) complexes with tripodal nitrogen-containing neutral ligands such as tris(3,5-diisopropyl-1-pyrazolyl)methane (L1') and tris(3-tertiary-butyl-5-isopropyl-1-pyrazolyl)methane (L3'), and with corresponding anionic ligands such as hydrotris(3,5-diisopropyl-1-pyrazolyl)borate (L1-) and hydrotris(3-tertiary-butyl-5-isopropyl-1-pyrazolyl)borate (L3-) were synthesized and structurally characterized. Copper(I) complexes [Cu(L1')Cl] (1), [Cu(L1')(OClO3)] (2), [Cu(L1')(NCMe)](PF6) (3a), [Cu(L1')(NCMe)](ClO4) (3b), [Cu(L1')(CO)](PF6) (4a), and [Cu(L1')(CO)](ClO4) (4b) were prepared using the ligand L1'. Copper(I) complexes [Cu(L3')Cl] (5) and [Cu(L3')(NCMe)](PF6) (6) with the ligand L3' were also synthesized. Copper(I) complexes [Cu(L1)(NCMe)] (7) and [Cu(L1)(CO)] (8) were prepared using the anionic ligand L1-. Finally, copper(I) complexes with anionic ligand L3- and acetonitrile (9) and carbon monoxide (10) were synthesized. The complexes obtained were fully characterized by IR, far-IR, 1H NMR, and 13C NMR spectroscopy. The structures of both ligands, L1' and L3', and of complexes 1, 2, 3a, 3b, 4a, 4b, 5, 6, 7, and 10 were determined by X-ray crystallography. The effects of the differences in (a) the fourth ligand and the counteranion, (b) the steric hindrance at the third position of the pyrazolyl rings, and most importantly, (c) the charge of the N3 type ligands, on the structures, spectroscopic properties, and reactivities of the copper(I) complexes are discussed. The observed differences in the reactivities toward O2 of the copper(I) acetonitrile complexes are traced back to differences in the oxidation potentials determined by cyclic voltammetry. A special focus is set on the carbonyl complexes, where the 13C NMR and vibrational data are presented. Density functional theory (DFT) calculations are used to shed light on the differences in CO bonding in the compounds with neutral and anionic N3 ligands. In correlation with the vibrational and electrochemical data of these complexes, it is demonstrated that the C-O stretching vibration is a sensitive probe for the "electron richness" of copper(I) in these compounds.     

ScorpoPhos: a novel phosphine-nitrogen ligand containing a tris(pyrazolyl)borate ligand core

A new tris(pyrazolyl)borate ligand bearing phosphine donor groups appended to the 3-position of the pyrazolyl rings is reported, and the hemilabile behaviour of this tris-N,P ligand in coordination with K+, Tl+ and Cu+ ions is investigated.     

Influences of changes in multitopic tris(pyrazolyl)methane ligand topology on silver(I) supramolecular structures

The reactions between silver tetrafluoroborate and the ligands 1,2,4,5-C(6)H(2)[CH(2)OCH(2)C(pz)(3)](4) (L1, pz = pyrazolyl ring), o-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2) (L2), and m-C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2) (L3) yield coordination polymers of the formula (C(6)H(6)(-)(n)[CH(2)OCH(2)C(pz)(3)](n)(AgBF4)(m))( infinity ) (n = 4, m = 2, 1; n = 2, ortho substitution, m = 1, 2; meta substitution, m = 2, 3). In the solid state, L2 molecules dimerize by a pair of C-H.pi interactions, forming an arrangement that resembles the tetratopic ligand L1. In the solid-state structure of 1, each silver atom is kappa(2)-bonded to two tris(pyrazolyl)methane units from different ligands with the overall structure a polymer made up from 32-atom macrocyclic rings formed by bonding tris(pyrazolyl)methane groups from nonadjacent positions on the central arene rings to the same two silver atoms. In 2, each silver is bonded to two tris(pyrazolyl)methane units in the same kappa(2)-kappa(2) fashion as with 1, forming a polymer chain. The chains are organized into dimeric units by strong face-to-face pi-pi stacking between the central arene rings making bitopic L2 act as half of tetratopic L1. The chains in both structures are organized by weak C-H.F hydrogen bonds and pi-pi stacking interactions into very similar 3D supramolecular architectures. The structure of 3 contains three types of silvers with the overall 3D supramolecular sinusoidal structure comprised of 32-atom macrocycles. Infrared studies confirm the importance of the noncovalent interactions. Calculations at the DFT (B3LYP/6-31G) level of theory have been carried out on L2 and also support C-H.pi interactions. Electrospray mass spectral data collected from acetone or acetonitrile show the presence of aggregated species such as [(L)Ag(2)(BF(4))](+) and [(L)Ag(2)](2+), despite the fact that (1)H NMR spectra of all compounds show that acetonitrile completely displaces the ligand whereas acetone does not.     

A tris(pyrazolyl) eta6-arene ligand that selects Cu(I) over Cu(II)

1,3,5-Tris{2'-[(pyrazol-1-yl)methyl]phenyl}benzene, 4, and its complexes with Cu(I) and Ag(I) have been prepared and characterized. Both CuI4 and AgI4 triflate crystallize in the rhombohedral space group R3, with the cations and anions each exhibiting crystallographically imposed 3-fold (C3) symmetry. In both complexes, 4 behaves as a tris(pyrazolyl) eta6-arene ligand whose arms act as three-pronged tweezers to form chiral, propeller-like cations with pyramidal MN(pyrazole)3 coordination geometries. Centers of symmetry in the space group ensure that the crystals are racemates, with equal numbers of P,P,P and M,M,M enantiomers. In broad outline, each cation is shaped like a three-legged stool, with the metal ion centered at the top and pointed downward from a triangular N(pyrazole) plane toward the center of gravity (Cg) of the central benzene ring (a metal-endo conformation), which constitutes the bottom shelf of the stool. The Cu(I)...Cg and Ag(I)...Cg distances, 3.195(2) and 3.165(2) A, respectively, support the existence of an eta6 bonding interaction with Ag(I) and, to a lesser extent, with Cu(I). NMR data for AgI4 suggest rapid interconversion of this cation in solution between P,P,P and M,M,M enantiomers. Our inability to prepare any Cu(II) complexes with 4 is consistent with cyclovoltammetric results, which suggest that the ligand is more easily oxidized than Cu(I).     

A practical synthesis of tris(pyrazolyl)methylaryls

The preparation of three tris(pyrazolyl)toluidines from trifluoromethylaniline reagents is described that likely takes advantage of (quinoidal) resonance-stabilized activation of the C-F bonds. Subsequent transformations lead to two additional (for a total of five new) tris(pyrazolyl)methylaryls. This simple reaction is remarkable because only one other tris(pyrazolyl)methylaryl has been reported previously, because it is usually very difficult to activate fluoroalkane C-F bonds, and because of the potential scope of the reaction.     

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.     

Structure, magnetism and photomagnetism of mixed-ligand tris(pyrazolyl)methane iron(ii) spin crossover compounds

A range of bis-facial tridentate chelate complexes of type [Fe((R-pz)(3)CH)((3,5-Me(2)pz)(3)CH)](BF(4))(2) has been characterised that contain two different tris-pyrazolylmethane ligands, with variations in R being H (complex crystallised as polymorphs and ) and 4-Me (), as well as R = H with a CH(2)OH arm off the methane carbon (). A tris(pyridyl)methane analogue is also described (). The tris(3,5-dimethylpyrazolyl)methane co-ligand (3,5-Me(2)pz), and the BF(4)(-) counterion, are constant throughout. The spin-crossover properties of these Fe(ii) d(6) compounds have been probed in detail by variable temperature magnetic, M?ssbauer spectral and crystallographic methods. The effects of distortions from octahedral symmetry around the Fe(ii) centres, of crystal solvate molecules (1.5 MeCN in and 2 MeCN in ) and of supramolecular/crystal packing, are discussed. In the case of , subtle twisting of pyrazole rings occurs, as a function of temperature, that has a greater effect upon the relative positions of the Fe(ii) chelate molecules in polymorph than in polymorph ; this is thought to drive the cooperativity differences observed in the magnetism of the polymorphs. Comparisons are also made between to and their homoleptic, parent [Fe(L)(2)] (2+) materials. The complexes were screened for the LIESST (light induced excited spin state trapping) effect by measurements of diffuse absorption spectra on the surface of powder samples, at different temperatures. One example, , showed a 2-step thermal spin crossover transition and it was probed in detail for its photomagnetic features. The T(LIESST) and T(1/2) values for did not obey an empirical relationship, T(LIESST) = 150 - 0.3T(1/2) followed by many Fe(ii)(N-donor)(6) crossover compounds of the bis-tridentate (meridional) type, and possible reasons for this are discussed.     

Silver(I) carbonyl and silver(I) ethylene complexes of a B-protected fluorinated tris(pyrazolyl)borate ligand

B-methylated ligand [MeB(3-(C2F5)Pz)3]-enables the isolation of a lithium adduct [MeB(3-(C2F5)Pz)3]Li with fac-N3F3 coordination, and rare isolable silver carbon monoxide and silver ethylene complexes, [MeB(3-(C2F5)Pz)3]AgCO and [MeB(3-(C2F5)Pz)3]AgC2H4.     

Optically active, bulky tris(oxazolinyl)borato magnesium and calcium compounds for asymmetric hydroamination/cyclization

The synthesis of the new chiral, pseudo C₃-symmetric, monoanionic ligand tris(4S-tert-butyl-2-oxazolinyl)phenylborate [To^T]⁻ is reported. The steric bulk, tridentate coordination, and anionic charge of [To^T]⁻ are suitable for formation of complexes of the type To^TMX, where one valence is available for reactivity. With this point in mind, we prepared magnesium and calcium To^T complexes that resist redistribution to (To^T)₂M compounds. Both To^TMgMe and To^TCaC(SiHMe₂)₃ contain tridentate To^T-coordination to the metal center, as shown by NMR spectroscopy, infrared spectroscopy, and X-ray crystallography. These compounds are active catalysts for the cyclization of three aminoalkenes to pyrrolidines, and provide non-racemic mixtures of pyrrolidines in enantiomeric excesses up to 36%.     

Catalytic dioxygen activation by Co(II) complexes employing a coordinatively versatile ligand scaffold

The ligand bis(2-isobutyrylamidophenyl)amine has been prepared and used to stabilize both mononuclear and dinuclear cobalt(II) complexes. The nuclearity of the cobalt product is regulated by the deprotonation state of the ligand. Both complexes catalytically oxidize triphenylphosphine to triphenylphosphine oxide in the presence of O(2).     

Structural comparison of copper(I) and copper(II) complexes with tris(2-pyridylmethyl)amine ligand

Copper(I) complexes with the tris(2-pyridylmethyl)amine (TPMA) ligand were synthesized and characterized to examine the effect of counteranions (Br(-), ClO(4)(-), and BPh(4)(-)), as well as auxiliary ligands (CH(3)CN, 4,4'-dipyridyl, and PPh(3)) on the molecular structures in both solid state and solution. Partial dissociation of one of the pyridyl arms in TPMA was not observed when small auxiliary ligands such as CH(3)CN or Br(-) were coordinated to copper(I), but was found to occur with larger ones such as PPh(3) or 4,4'-dipyridyl. All complexes were found to adopt a distorted tetrahedral geometry, with the exception of [Cu(I)(TPMA)][BPh(4)], which was found to be trigonal pyramidal because of stabilization via a long cuprophilic interaction with a bond length of 2.8323(12) ?. Copper(II) complexes with the general formula [Cu(II)(TPMA)X][Y] (X = Cl(-), Br(-) and Y = ClO(4)(-), BPh(4)(-)) were also synthesized to examine the effect of different counterions on the geometry of [Cu(II)(TPMA)X](+) cation, and were found to be isostructural with previously reported [Cu(II)(TPMA)X][X] (X = Cl(-) or Br(-)) complexes.     

Photochemistry of tris(pyrazolyl)borate titanium(IV) complexes

The electronic features and photochemistry of TpTiCl₃ (1) (Tp = hydrotris(pyrazol-1-yl)borate) and Tp*TiCl₃ (2) (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) were studied in THF. Reactive decay of the excited states produced either (or ) and metal center Ti(III) radicals via homolytic cleavage of the Tp → Ti (Tp* → Ti) bond. Cleavage of the Tp → Ti and the Tp* → Ti bond as a primary photoprocess is shown to be consistent with LMCT Tp → Ti and Tp* → Ti excitation. TpTiCl₂(THF) (3) and Tp*TiCl₂(THF) (4) were also prepared by stoichiometric reduction of 1 and 2 with Li₃N. The THF ligand in 3 and 4 was replaced by the stable nitroxyl radical TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to provide the new complexes TpTiCl₂(TEMPO) (5) and Tp*TiCl₂(TEMPO) (6) in which the TEMPO ligand is η¹ coordinated to Ti(IV). Photolysis of 5 and 6 generate Ti(III) and the TEMPO radical in the primary photochemical step.