Reactivity of bulky tris(phenylpyrazolyl)methanesulfonate copper(I) complexes towards small unsaturated molecules

Group 11 tris(pyrazolyl)methane complexes: structural features and catalytic applications

Tris(pyrazolyl)methane ligands (Tpm^x) have been for years a step behind their highly popular boron-anionic analogues, the tris(pyrazolyl)borate ligands (Tp^x).

Monoanionic, Bis(pyrazolyl)methylborate [(Ph3B)CH(3,5-(CH3)2Pz)2)]- as a Supporting Ligand for Copper(I)-ethylene, cis-2-Butene, and Carbonyl Complexes

The monoanionic bidentate ligand [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂)]^- has been prepared from lithium bis(pyrazolyl)methanide and triphenylborane. This useful new ligand is closely related to the well-established bis(pyrazolyl)borate and bis(pyrazolyl)methane ligands but has key differences to both analogues as well. The ethylene, cis-2-butene, and carbon monoxide adducts [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂]Cu(L) (where L = C₂H₄, cis-CH₃HC═CHCH₃, and CO) have been prepared from [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂)]Li(THF), copper(I) triflate, and the corresponding coligand. These complexes have been characterized by NMR spectroscopy and X-ray crystallography. In all cases the bis(pyrazolyl) moiety is bound in κ²N fashion with the BPh₃ group rotated to sit over the metal center, sometimes coordinating to the metal via phenyl carbons as in [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂)]Li(THF) and [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂]Cu(CO) or simply hovering above the metal site as in [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂)]Cu(C₂H₄) and [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂)]Cu(cis-CH₃HC═CHCH₃). The ¹³C and ¹H resonances of the ethylene carbon and protons of [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂)]Cu(C₂H₄) appear at δ 81.0 and 3.71 ppm in CD₂Cl₂, respectively. The characteristic CO frequency for [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂]Cu(CO) has been observed at υ̅ 2092 cm^-1 by infrared spectroscopy and is lower than that of free CO suggesting moderate M → CO π-back-donation. A detailed analysis of these complexes has been presented herein.

V(iv), Fe(ii), Ni(ii) and Cu(ii) complexes bearing 2,2,2-tris(pyrazol-1-yl)ethyl methanesulfonate: application as catalysts for the cyclooctane oxidation

New water-soluble scorpionate complexes were synthesized and applied as selective catalysts for cyclooctane oxidation in presence of basic or acid additives.

NiII, CuII and ZnII complexes with a sterically hindered scorpionate ligand (TpmsPh) and catalytic application in the diasteroselective nitroaldol (Henry) reaction

The bulky (Tpms^Ph)⁻ adapts its coordination mode to the electronic and steric preferences of the Ni^II, Cu^II or Zn^II centre forming complexes which catalyse the nitroaldol reaction.

Oxorhenium complexes bearing the water-soluble tris(pyrazol-1-yl)methanesulfonate, 1,3,5-triaza-7-phosphaadamantane, or related ligands, as catalysts for Baeyer-Villiger oxidation of ketones

New rhenium(VII or III) complexes [ReO3(PTA)2][ReO4] (1) (PTA = 1,3,5-triaza-7-phosphaadamantane), [ReO3(mPTA)][ReO4]I (2) (mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane cation), [ReO3(HMT)2][ReO4] (3) (HMT = hexamethylenetetramine), [ReO3(η(2)-Tpm)(PTA)][ReO4] (4) [Tpm = hydrotris(pyrazol-1-yl)methane, HC(pz)3, pz = pyrazolyl], [ReO3(Hpz)(HMT)][ReO4] (5) (Hpz = pyrazole), [ReO(Tpms)(HMT)] (6) [Tpms = tris(pyrazol-1-yl)methanesulfonate, O3SC(pz)3(-)] and [ReCl2{N2C(O)Ph}(PTA)3] (7) have been prepared from the Re(VII) oxide Re2O7 (1-6) or, in the case of 7, by ligand exchange from the benzoyldiazenido complex [ReCl2{N2C(O)Ph}(Hpz)(PPh3)2], and characterized by IR and NMR spectroscopies, elemental analysis and electrochemical properties. Theoretical calculations at the density functional theory (DFT) level of theory indicated that the coordination of PTA to both Re(III) and Re(VII) centers by the P atom is preferable compared to the coordination by the N atom. This is interpreted in terms of the Re-PTA bond energy and hard-soft acid-base theory. The oxo-rhenium complexes 1-6 act as selective catalysts for the Baeyer-Villiger oxidation of cyclic and linear ketones (e.g., 2-methylcyclohexanone, 2-methylcyclopentanone, cyclohexanone, cyclopentanone, cyclobutanone, and 3,3-dimethyl-2-butanone or pinacolone) to the corresponding lactones or esters, in the presence of aqueous H2O2. The effects of a variety of factors are studied toward the optimization of the process.