A series of cyanide-bridged binuclear complexes

A series of cyanide-bridged binuclear complexes, (‘S₃’)Ni-CN-M[Tp^tBu] (‘S₃’ = bis(2-mercaptophenyl)sulfide, Tp^tBu = hydrotris(3-tert-butylpyrazolyl)borate, M = Fe (2-Fe), Co (2-Co), Ni (2-Ni), Zn (2-Zn)) was prepared by the coupling of K[(‘S₃’)Ni(CN)] with [Tp^tBu]MX. The isostructural series of complexes was structurally and spectroscopically characterized. A similar coupling strategy was used to synthesize the anionic copper(I) analogue, Et₄N{(‘S₃’)Ni-CN-Cu[Tp^tBu]}, 2-Cu.An alternative synthesis was devised for the preparation of the linkage isomers of 2-Zn, i.e. of cyanide-bridged linkage isomers. X-ray diffraction, ¹³C NMR and IR spectral studies established that isomerization to the more stable Ni-CN-Zn isomer occurs. DFT computational results buttressed the experimental observations indicating that the cyanide-bridged isomer is ca. 5 kcal/mol more stable than its linkage isomer.     

Synthesis and redox properties of dinuclear rhodium(II) carboxylates with 2,6-di-tert-butylphenol moieties

By exploiting the peculiar reactivity of [Rh₂(μ-O₂CBu^t)₄(H₂O)₂] (1) the examples of dinuclear rhodium(II) carboxylates containing N-donor axial ligands (2, 3) [Rh₂(μ-O₂CBu^t)₄L₂] [where L = benzonitrile (2), 3,5-di-tert-butyl-4-hydroxybenzonitrile (3)] were synthesized and characterized by elemental analysis, IR, multinuclear NMR spectroscopy, MALDI-TOF mass spectrometry. It was found by X-ray diffraction that pairs of 3 in crystals are associated through H atoms of phenol groups to produce a dimer of dimers. The chemical oxidation of dirhodium complexes with 2,6-di-tert-butyl-4-cyanоphenol pendants studied by means of ESR method in solutions leads to the formation of phenoxyl radicals 3′ in dirhodium system. The ESR data show the interaction of the unpaired electron with ligand nuclei (¹H, ¹⁴N) and ¹⁰³Rh. The stability of radical complexes with phenoxyl fragments in axial position is influenced by the temperature. The enthalpy of the 3′ decomposition followed by the formation of cyanophenoxyl radical as 20 ± 1 kJ/mol was estimated. Redox transformations in dirhodium system including both metal and axial ligands were investigated by electrochemistry. CV experiments confirm the assumption of the metal oxidation (Rh^II→Rh^III) as the first step following by the oxidation of the ligand.     

Spectro-electrochemical and DFT studies of a planar Cu(II)-phenolate complex active in the aerobic oxidation of primary alcohols

A square-planar compound [Cu(pyrimol)Cl] (pyrimol = 4-methyl-2-N-(2-pyridylmethylene)aminophenolate) abbreviated as CuL-Cl) is described as a biomimetic model of the enzyme galactose oxidase (GOase). This copper(II) compound is capable of stoichiometric aerobic oxidation of activated primary alcohols in acetonitrile/water to the corresponding aldehydes. It can be obtained either from Hpyrimol (HL) or its reduced/hydrogenated form Hpyramol (4-methyl-2-N-(2-pyridylmethyl)aminophenol; H₂L) readily converting to pyrimol (L⁻) on coordination to the copper(II) ion. Crystalline CuL-Cl and its bromide derivative exhibit a perfect square-planar geometry with Cu-O(phenolate) bond lengths of 1.944(2) and 1.938(2) Å. The cyclic voltammogram of CuL-Cl exhibits an irreversible anodic wave at +0.50 and +0.57 V versus ferrocene/ferrocenium (Fc/Fc⁺) in dry dichloromethane and acetonitrile, respectively, corresponding to oxidation of the phenolate ligand to the corresponding phenoxyl radical. In the strongly donating acetonitrile the oxidation path involves reversible solvent coordination at the Cu(II) centre. The presence of the dominant Cu^II-L chromophore in the electrochemically and chemically oxidised species is evident from a new fairly intense electronic absorption at 400-480 nm ascribed to a several electronic transitions having a mixed π → π^∗(L) intraligand and Cu-Cl → L charge transfer character. The EPR signal of CuL-Cl disappears on oxidation due to strong intramolecular antiferromagnetic exchange coupling between the phenoxyl radical ligand (L) and the copper(II) centre, giving rise to a singlet ground state (S = 0). The key step in the mechanism of the primary alcohol oxidation by CuL-Cl is probably the α-hydrogen abstraction from the equatorially bound alcoholate by the phenoxyl moiety in the oxidised pyrimol ligand, Cu-L, through a five-membered cyclic transition state.     

Zinc(II)-phenoxyl radical complexes: Dependence on complexation properties of Zn-phenolate species

Zinc(II) complexes of N₃O-donor tripodal ligands, 2,4-di(tert-butyl)-6-{[bis(2-pyridyl)methyl]aminomethyl}phenol (HtbuL), 2,4-di(tert-butyl)-6-{[(6-methyl-2-pyridyl)methyl]-(2-pyridyl)methylaminomethyl}phenol (HtbuLMepy), and 2,4-di(tert-butyl)-6-{[bis(6-methyl-2-pyridyl)methyl]aminomethyl}phenol (HtbuL(Mepy)₂), [Zn(tbuL)Cl] · CH₃OH (1), [Zn(tbuLMepy)Cl] (2), and [Zn(tbuL(Mepy)₂)Cl] (3), respectively, were prepared and structurally characterized by the X-ray diffraction method. All the complexes were found to have a mononuclear structure with a coordinated phenolate moiety, the geometry of the Zn(II) center being 5-coordinate trigonal-bipyramidal. The Zn(II) binding ability of the ligands with and without 6-methyl-2-pyridylmethyl moieties was evaluated for similar ligands, which lacked the t-butyl groups at the 2- and 4-positions of the phenol moiety, by the stability constants determined by potentiometric titration at 25 °C (I = 0.1 M (KNO₃)). The stability of the complexes was found to be in the order L > LMepy > L(Mepy)₂, reflecting the steric hindrance of the 6-methyl group of the pyridine ring. Complexes 1, 2, and 3 were converted to the phenoxyl radicals upon oxidation with Ce(IV), giving a phenoxyl radical π-π∗ transition band at 394-407 nm. ESR and resonance Raman spectra established that the radical species had a Zn(II)-phenoxyl radical bond. The cyclic voltammograms showed similar quasi-reversible redox waves with E_1/2 = 0.68, 0.67, and 0.63 V (versus Ag/AgCl) for 1, 2, and 3, respectively, corresponding to the formation of the phenoxyl radical, which displayed a first-order decay. The half-lives, 58.6, 25.8, and 15.6 min at −40 °C for 1, 2, and 3, respectively, follow the order of the stability constants of the complexes, indicating that the metal(II)-phenoxyl radical stability is in close relationship with the complexation properties of the present series of N₃O-donor ligands.     

Synthesis, characterization and structure of a new zinc(II) complex containing the hexadentate N,N′,N,N′-bis[(2-hydroxy-3,5-di-tert-butylbenzyl)(2-pyridylmethyl)]-ethylenediamine ligand: Generation of phenoxyl radical species

This work summarizes the results of our studies on the structural, spectral and redox properties of a mononuclear zinc(II) complex with the new H₂L ligand (H₂L = N,N′,N,N′-bis[(2-hydroxy-3,5-di-tert-butylbenzyl)(2-pyridylmethyl)]-ethylene diamine). The crystal structure of the complex [Zn^II(HL)] · ClO₄ (1) was determined by X-ray crystallographic analysis. The structure of this complex consists of a discrete mononuclear cation [Zn^II(HL)]⁺, in a strongly distorted geometry with a slight tendency toward a distorted square pyramidal geometry, as reflected by the structural index parameter τ of 0.44. The zinc(II) cation is coordinated to one oxygen and four nitrogen atoms: the pyridine nitrogen atoms (N22 and N32), tertiary amine nitrogen atoms (N1 and N4) and phenolate oxygen atom (O10). ¹H and ¹³C NMR spectral data show a rigid solution structure for 1 in agreement with X-ray structure. Potentiometric studies of complex 1 were also performed and revealed three titratable protons which are attributed to the protonation/deprotonation of two phenol groups (p[K]_a1 = 4.04 and p[K]_a3 = 11.34) and dissociation of a metal-bound water molecule (p[K]_a2 = 7.8). The phenolate groups in complex 1 are suitably protected by bulky substituents (tert-butyl) in the ortho- and para-positions, which through electrochemical oxidation generate a one-electron oxidized phenoxyl species in solution. This radical species was characterized by UV-Vis, EPR and electrochemical studies. The Zn(II)-phenoxyl radical species is of bioinorganic relevance, since its spectroscopic, redox and reactivity properties can be used to establish the role of phenoxyl radicals in biological and catalytical systems.     

Magnesium (II) poly(pyrazolyl)borate derivatives - Synthesis, spectral and structural studies

A series of magnesium complexes of general formula [Mg(Tp^x)₂] (Tp^x = Tp, Tp^∗, Tp^∗Cl, pzTp) and [Mg(Tp^x)X] (X = Cl, Tp^x = Tp^tBu or pz⁰Tp^p-Tol; X = acetate, Tp^x = Tp^tBu) were synthesised from magnesium chloride or acetate and M(Tp^x) (M = K, Na or Tl) in dichloromethane or alcoholic solution. These compounds are air-stable solids, sparingly soluble in most organic solvents; they have been characterized by elemental analysis, IR, ¹H and ¹³C NMR spectra and, in selected cases, also by conductivity and molecular weight measurements. Single crystal X-ray diffraction studies of [Mg(Tp)₂], [Mg(Tp*)₂] and [Mg(Tp*^Cl)₂] show unsolvated neutral bis(tripod ligand)magnesium(II) molecules with six-coordinate magnesium atoms (〈Mg-N〉 2.167(6), 2.19(2), 2.205(4) Å).     

Co and Cu complexes of reduced Schiff bases: Generation of phenoxyl radical species

The three complexes [Co^IIIL¹Cl] (1), [Co^IIIL²]⁺·ClO₄⁻ (2⁺·ClO₄⁻), and [Cu^IIH₂L²]²⁺·2ClO₄⁻ (H₂3²⁺·2ClO₄⁻) [where H₂L¹ = N,N′-dimethyl-N,N′-bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethylenediamine, H₂L² = N,N′-bis(2-pyridylmethyl)-N,N′-bis(2-hydroxy-3,5-di-tert-butylbenzyl)ethylenediamine] have been prepared. The bis-phenolate and bis-phenol complexes, 2⁺ and H₂3²⁺ respectively, have been characterized by X-ray diffraction, showing a metal ion within an elongated octahedral geometry. 1-2 exhibit in their cyclic voltammetry curves two anodic reversible waves attributed to the successive oxidation of the phenolates into phenoxyl radicals. The cobalt radical species (1)⁺, (2)²⁺, and (2)³⁺ have been characterized by combined UV-Vis and EPR spectroscopies. In the presence of one equivalent of base, one phenolic arm of H₂3²⁺ is deprotonated and coordinates the metal. The resulting complex (H3⁺) exhibits a single reversible redox wave at ca. 0.3 V. The electrochemically generated oxidized species is EPR silent and exhibits the typical features of a radical compound, with absorption bands at 411 and 650 nm. The fully deprotonated complex 3 is obtained by addition of two equivalents of nBu₄N⁺OH⁻ to H₂3²⁺. It exhibits a new redox wave at a lower potential (−0.16 V), in addition to the wave at ca. 0.3 V. We assigned the former to the one-electron oxidation of the uncoordinated phenolate into an unstable phenoxyl radical.     

A sterically hindered tetrakis(pyrazolyl)borate: Synthesis, characterization and coordinative behaviour

The sterically hindered tetrakis-(3-(p-tolylpyrazolyl)borate [pz⁰Tp^p-Tol] has been prepared and its reaction with CuX₂.nH₂O (X = Cl or acetate (OAc), M(NO₃)₂.6H₂O (M = Ni, or Co) and MCl₂ (M = Zn or Cd) has been investigated. [M(pz⁰Tp^p-Tol)X(Hpz^p-Tol)] (M = Cu, X = Cl or OAc; M = Ni or Co, X = NO₃) and [M(pz⁰Tp^p-Tol)Cl(Hpz^p-Tol)_2-n(H₂O)_n] have been synthesised and their spectroscopic properties described, the five-coordinated Cu species being also structurally characterized. The methyl groups in the para-tolyl fragments of the ligand strongly influences the stoichiometry and structure of the metal complexes.     

A new type of electrochemical oxidation of alcohols mediated with a ruthenium-dioxolene-amine complex in neutral water

Electrochemical oxidation of [Ru^II(terpy)(sq)(NH₃)]⁺ in neutral water (pH 8.0) at +0.8 V (versus SCE) generated [Ru^II(terpy)(q)(NH₂)]²⁺ and/or [Ru^III(terpy)(sq)(NH₂)]²⁺ (terpy = 2,2′:6′,2′′-terpyridine, sq = 3,5-di-tert-butyl-1,2-semiquinonate, q = 3,5-di-tert-butyl-1,2-benzoquinone), which played roles in hydrogen abstraction and one-electron acceptor in the catalytic oxidation of methanol, ethanol, and 2-propanol affording formaldehyde, acetoaldehyde, and acetone, respectively, under the electrolysis conditions.     

Molybdenum doubly bridged and chelate nitrosyl complexes incorporating saturated n-alkanediolate ligands

The redox-active doubly bridged species [{Mo(NO)(Tp^Me2)Q}₂] [Tp^Me2 = tris(3,5-dimethylpyrazol-1-yl)hydroborate, Q = O(CH₂)_nO, n = 3, 5, or OCH₂(CF₂)_n−2CH₂O, n = 5, 6], and a chelate complex [Mo(NO)-(Tp^Me2)O(CH₂)₅O] were prepared and characterised by elemental and mass analyses, ¹H NMR and IR spectroscopy. The bimetallic species with C₃, C₅, and C₅(F) bridges exhibit two well-resolved reduction processes in their cyclic voltammograms (ΔE_1/2 values of 290, 170, and 170 mV, respectively). These results indicate that the presence of the second bridge increases the extent of electrochemical interactions (by ca. 90-130 mV) in comparison with their singly bridged analogues. All non-fluorinated and the chelate species were catalytically active in cathodic reduction of chloroform.     

Pyrazolate-bridged group 11 metal(I) complexes: Substituent effects on the supramolecular structures and physicochemical properties

Polynuclear homoleptic pyrazolate-bridged group 11 metal(I) complexes with three different alkyl substituted pyrazolate anions, 3,5-diisopropylpyrazolate (3,5-iPr₂pz⁻ = L1⁻), 3-tert-butyl-5-isopropylpyrazolate (3-tBu-5-iPrpz⁻ = L3⁻), and 3,5-di-tert-butylpyrazolate (3,5-tBu₂pz⁻ = L4⁻), i.e. [Cu(μ-3,5-iPr₂pz)]₃ (CuL1), [Ag(μ-3,5-iPr₂pz)]₃ (AgL1), [Au(μ-3,5-iPr₂pz)]₃ (AuL1), [Cu(μ-3-tBu-5-iPrpz)]₄ (CuL3), [Ag(μ-3-tBu-5-iPrpz)]₃ (AgL3), [Au(μ-3-tBu-5-iPrpz)]₄ (AuL3), [Cu(μ-3,5-tBu₂pz)]₄ (CuL4), [Ag(μ-3,5-tBu₂pz)]₄ (AgL4), and [Cu(μ-3,5-tBu₂pz)]₄ (AuL4), were systematically synthesized in order to investigate the influence of pyrazole bulkiness on their structures and physicochemical properties. The structural characterization indicates that the geometries are greatly influenced by the steric hindrance exerted by the substituent groups of the pyrazolyl rings and the differences of the central metal (I) ionic radius (Cu⁺ < Au⁺ < Ag⁺). These complexes were also characterized by spectroscopic techniques, namely, UV-Vis, IR/far-IR, Raman, and luminescence spectroscopy.     

A new tris(2-furyl) substituted pyrazolylborate ligand and its zinc complex chemistry

The new ligand hydrotris(3-(2′-furyl)-5-methylpyrazolyl)borate (Tp^Fu,Me) was prepared by the usual procedure. With zinc salts, it forms the Tp^Fu,MeZn-X complexes (X = Cl, Br, I, NCS, CH₃COO, CF₃COO). With zinc perchlorate, the bis-ligand complex Zn(Tp^Fu,Me)₂ is formed preferrably, but by carefully controlling the reaction conditions, the “enzyme model” Tp^Fu,MeZn-OH could be obtained. The latter models carbonic anhydrase by inserting CO₂ and CS₂ in methanol producing Tp^Fu,MeZn-OCOOMe and Tp^Fu,MeZn-SCSOMe. It models hydrolases by the hydrolytic cleavage of tris(p-nitrophenyl)phosphate and γ-thiobutyrolactone. It does not hydrolyse trifluoroacetamide, but instead deprotonates it, yielding Tp^Fu,MeZn-NHCOCF₃.     

The synthesis and characterisation of phenolate complexes of Cu(II) and Ni(II) that are capable of supporting a phenoxyl radical ligand

New Cu^II and Ni^II complexes of potentially tridentate N₂O Schiff base ligands 1 and 2 have been synthesised and characterised. [Cu(2)(OH₂)]⁺ possesses a square planar geometry in the solid state whereas [Ni(1)₂] possesses a distorted octahedral geometry in which the amine donors of 1 coordinate weakly to the Ni^II centre. EPR spectroscopy demonstrates that the N₂O₂ coordination sphere of [Cu(2)(OH₂)]⁺ is retained in CH₂Cl₂ solution. [Cu(2)(OH₂)]⁺ exhibits a reversible one electron oxidation at E_1/2 = 0.54 V versus [Fc]⁺/[Fc], the product of which has been characterised by UV-Vis absorption and EPR spectroscopies. The spectroscopic signature of the oxidised product is consistent with the formation of a stable phenoxyl radical ligand bound to a Cu^II centre. [Ni(1)₂] possesses a reversible metal-based oxidation process at E_1/2 = 0.03 V versus [Fc]⁺/[Fc] and a further oxidation, attributed to the generation of a phenoxyl radical centre, at  = 0.44 V versus [Fc]⁺/[Fc]. UV-Vis absorption and EPR spectroscopic studies indicate that the lower potential process is a formal Ni^III/II couple. In contrast, the pro-ligands 1H and 2H exhibit chemically irreversible oxidation processes at  = 0.42 and 0.40 V versus Fc⁺/Fc, respectively, and do not support the formation of stable phenoxyl radical species.     

Redox and catalytic properties of alkoxides based on tris(3,5-dimethylpyrazolyl)borato tungsten nitrosyls

Previously we reported on the catalytic properties of species based on the {Mo(NO)(Tp^Me2)O₂} moiety in the cathodic reduction of chloroform. Here, we have performed cyclic voltammetry and spectroscopic studies of the tungsten bis-alkoxide [W(NO)(Tp^Me2)(OEt)₂], a novel chelate [W(NO)(Tp^Me2)O(CH₂)₄O], and a mono-alkoxide [W(NO)(Tp^Me2)Cl(OEt)] [Tp^Me2 = hydrotris(3,5-dimethylpyrazol-1-yl)borate]. All these complexes efficiently catalyse the cathodic reduction of chloroform which proceeds even at ca. −1.77 V versus Fc⁺/Fc in the presence of the chloro(ethoxy) complex. The chelate complex exhibits a quasi-reversible one-electron reduction at a potential 180 mV more anodic than its bis(ethoxy) counterpart. The UV-Vis spectrum of the former complex shows a red-shifted band (by 70 nm) in the visible region when compared with the latter.     

Luminescent phosphinocrown-containing gold(I) complexes: Their syntheses, spectroscopic studies and host-guest chemistry

A series of phosphinocrown ether-containing gold(I) complexes, [Au(Ph₂P-b15c5)Cl] (1), [Au₂(μ-i-mnt)(Ph₂P-b15c5)₂] (2) and [Au₂(μ-dtc)(Ph₂P-b15c5)₂](PF₆) (3) (b15c5 = benzo-15-crown-5, i-mnt²⁻ = 1,1-dicyanoethylene-2,2-dithiolate, dtc⁻ = diethyldithiocarbamate) have been synthesized. Complexes 2 and 3 · NaPF₆ have also been structurally characterized. The emission bands at ca. 500-515 nm for 2 and 3 upon photo-excitation are tentatively assigned as derived from excited states of S → Au ligand-to-metal charge transfer (LMCT) origin. These complexes have been shown to serve as host for the specific binding of various metal cations.     

Gold acyls and imidoyls prepared from anionic Fischer-type carbene complexes

Reaction of [(CO)₅WC(O)Ph]Li or [(CO)₅WC(O)Ph]NBu₄ with Ph₃PAuCl affords acyl complexes of gold. In the latter conversion, both the crystalline products [(CO)₅WCl]NBu₄ (2) and Ph₃PAuC(O)Ph (3) have been isolated and fully characterised. Similarly, imidoyl gold compounds (4-8) result from deprotonated aminocarbene complexes, [(CO)₅MC(NR²)R¹]Li (M = Cr, W; R¹ = Ph, Me; R² = H, Me) and Ph₃PAuCl. Crystal and molecular structure determinations of dinuclear [Ph₃PAuC(NH)Ph] · Cr(CO)₅ (6) show N-coordination of the chromium carbonyl unit that selectively affords a Z-isomer.     

Rhodium and iridium olefin complexes with bulky cyclopentadienyl and hydrotris(pyrazolyl)borate ligands

The synthesis of a series of rhodium and iridium complexes bearing bulky cyclopentadienyl or hydro(trispyrazolyl)borate ligands is described. The rhodium cyclopentadienyl and hydrotris(pyrazolyl)borate diene compounds, [(η⁵-C₅Me₄Bu^t)Rh(η⁴-2,3-MeRC₄H₄] (R = H, 1; Me, 2) and Tp^MsRh(η⁴-2,3-MeRC₄H₄) (R = H, 3; Me, 4; Tp^Ms is hydrotris(3-mesitylpyrazol-1-yl)borate), respectively, have been prepared from the corresponding Rh(I) diene precursors and Zn(C₅Me₄Bu^t)₂ (for 1 and 2), or TlTp^Ms (for 3 and 4), as effective C₅Me₄Bu^t or Tp^Ms transfer reagents. In contrast with these results, attempts to obtain a bis(ethylene) derivative of the Tp^tolIr(I) unit (Tp^tol stands for hydrotris(3-p-tolylpyrazol-1-yl)borate) have provided instead the Ir(III) complex [(κ⁴-N,N′,N″,C-Tp^tol)-Ir(C₂H₅)(C₂H₄)] (5), whose formation requires C-H bond activation of a molecule of ethylene and of one of the Tp^tolp-tolyl substituents. In refluxing toluene 5 experiences metalation of a second p-tolyl substituent to give [(κ⁵-N,N′,N″,C,C′-Tp^tol)-Ir(C₂H₄)] (6), which features unusual κ⁵-Tp^tol coordination. The latter compound reacts with carbon monoxide to yield the corresponding carbonyl, 7.     

A series of oxo-vanadium(IV) complexes containing mixed ligands of poly(pyrazolyl)borate and organic carboxylic acid: Synthesis, structural characterization and primary study of bromination reaction activities

A series of oxo-vanadium(IV) complexes: Tp^∗VO(pzH^∗)(CH₃COO) (1), Tp^∗VO(pzH^∗)(CCl₃COO) (2), Tp^∗VO(pzH^∗)(C₆H₅COO) (3), Tp^∗VO(pzH^∗)(m-NO₂-C₆H₄COO)·CH₃CN (4) and [Tp^∗VO(pzH^∗)(H₂O)]⁺[m-NO₂-C₆H₄-SO₃]⁻·CH₃OH (5) (Tp^∗ = hydrotris(3,5-dimethylpyrazolyl)borate; pzH^∗ = 3,5-dimethylpyrazole) are synthesized in methanol solution under physiological conditions. They are characterized by elemental analysis, IR, UV-Vis and X-ray crystallography. Structural analyses show that the vanadium atoms in complexes 1-5 are all in a distorted-octahedral environment with the N₄O₂ donor set, and intra- or inter-hydrogen bonding linkages have been also observed in each complex. Bromination reaction activity of the complexes has been evaluated by the method with phenol red as organic substrate in the presence of H₂O₂, Br⁻ and phosphate buffer, indicating that they can be considered as potential functional model vanadium-dependent haloperoxidases. In addition, thermal analysis and quantum chemistry calculations were also performed and discussed in detail.     

Heteroleptic lanthanide terphenyl/tris(pyrazolyl)borate compounds of ytterbium

The synthesis and structural characterization of the two novel unsolvated heteroleptic ytterbium compounds DanipYb(Tp^Me,Me)Cl (1) and DanipYb(Tp^Me,Me)CH₂SiMe₃ (2) by simple salt metathesis reaction is reported [Danip = 2,6-di(o-anisol)phenyl); Tp^Me,Me = hydrotris(3,5-dimethyl-pyrazolyl)borate]. In the molecular structure of 2 a flexible bonding mode of the donor-functionalized terphenylic ligand is observed.     

Gallium and indium compounds supported by a [PNP] pincer ligand

The new bis(phosphino)amido ligand, [MePNP^Ph], that incorporates (i) an ortho-tolylene linker between nitrogen and phosphorus and (ii) phenyl substituents on phosphorus, has been synthesized as its protonated derivative, [MePNP^Ph]H, via sequential treatment of (2-Br,4-Me-C₆H₃)₂NH with (i) BuⁿLi, (ii) Ph₂PCl and (iii) HCl. Deprotonation of [MePNP^Ph]H with BuⁿLi in THF affords the lithium derivative which has been isolated as both mono and bis THF adducts, [MePNP^Ph]Li(THF) and [MePNP^Ph]Li(THF)₂. Treatment of [MePNP^Ph]Li(THF)₂ with GaCl₃ and InX₃ (X = Cl, Br, I) gives a series of [MePNP^Ph]MX₂ complexes in which the [PNP] donor binds in a “T”-shaped manner and the metal has a distorted trigonal bipyramidal geometry. The reaction of [MePNP^Ph]Li(THF)₂ with “GaI” yields the Ga-Ga bonded complex [κ²-MePNP^Ph](GaI)(GaI)[κ²-MePNP^Ph] in which the [MePNP^Ph] ligand binds in a κ²-P,N manner. The bis(phosphino)amine [MePNP^Ph]H may also serve as a ligand and treatment of [MePNP^Ph]H with GaBr₃ affords [κ²-{[MePNP^Ph]H}GaBr₂][GaBr₄], in which the [MePNP^Ph]H ligand coordinates in a κ²-P,P manner such that the gallium adopts a tetrahedral geometry.