Cobalt complexes pyrazole

Ring-opening silylformylation has been observed by Murai and coworkers in reactions of cyclic ethers. When the cobalt complex Co2(CO)8 is used as the catalyst in reactions of epoxides, an excess of substrate is required to prevent further reaction of the product siloxy aldehyde.1192 Further investigation led to the discovery of [RhCl(CO)2]2/l-methyl-pyrazole as an effective catalyst combination for the reaction of oxi-ranes119b and oxetanes.J19c For example, oxetane undergoes silylformylation to give 4-(dimethylphenylsiloxy)butanal in 81% yield [Eq. (45)]. 

Due to the low solubility of cobalt(II) fluoride in most solvents, formation of cobalt fluoro N-donor complexes (which are the only low-valent cobalt fluorides which are reliably reported) features a variety of starting materials. A common theme that runs throughout this work has been the use of [Co(BF4)2] as the fluoride source, and the subsequent controlled decomposition to obtain a metal-bound fluoride. This has been done, for example, with tris- (3,5-dimethyl-pyrazol-l-yl)methyl amine (amtd) to give [M2(amtd)2F(BF4)3(EtOH)Y(H20)] (M = Co, Cu, Zn x = 0-1.5, y = 1-2). The cobalt complex has been structurally characterised by X-ray diffraction [Fig. 3] [57]. Similarly, the combination of [M(BF4)2] (M = Mn, Co, Ni), [M(N03)2], NH4(NCS) and 3,5-diethyl-1,2,4-triazole (detrH) produces... 

N2C2H1, 1,2-Ethanediamine, cobalt complexes, 21 19, 21, 120-126 N2C3H4, lH-Pyrazole, boron-copper complex, 21 108, 110... 

A single report documents the study of perfluoroalkyl poly(pyrazolyl)borate cobalt complexes however, their breadth and significance is appreciable. The compounds H B(pz)4 CpCo(Rf) (x = 0, 1,2) were prepared by the interaction of the respective K[H B(pz)4 J salt with CpCo(Rf)(CO)I, and in each case exhibit bidentate coordination of the poly(pyrazolyl)borate ligand, regardless of the number of pyrazole donors potentially available. 

Despite the weak basicity of isoxazoles, complexes of the parent methyl and phenyl derivatives with numerous metal ions such as copper, zinc, cobalt, etc. have been described (79AHC(25) 147). Many transition metal cations form complexes with Imidazoles the coordination number is four to six (70AHC(12)103). The chemistry of pyrazole complexes has been especially well studied and coordination compounds are known with thlazoles and 1,2,4-triazoles. Tetrazole anions also form good ligands for heavy metals (77AHC(21)323). 

Cyclooctane-l,5-diyl-bis(pyrazol-l-yl)borate (L) with cobalt(II), nickel(II), and zinc(II) nitrates gives [(j -L)M] (M = Co, Ni, Zn) strongly stabilized by the C—H M agostic interactions, which justifies their inclusion in the class of organometallic complexes [89AGE205, 91ICA(183)203, 92IC974]. 

When n = 2 or 3, such structurally characterized ICC, in the majority of cases, have slightly tetrahedrizated c/.v-planar conformations [100]. The effect of the factor examined is so high that even zinc chelates 882 (M = Zn, R = Me, X = S, n — 2) show a considerably planar-distorted structure [209]. An analogous structural situation is observed for cobalt, nickel, and copper complexes containing R — cyclo-(C 12)3, annelated aromatic, and pyrazol fragments [100]. When n increases, for example n = 4 in the complexes capable of tetrahedrizating a structure, the influence of the examined factor decreases. This is observed in the ICC not only with X = S [100,210 212], but also for X = NH 222 [187]. 

Cobalt, cyclopentadienyl complexes with thioformaldehyde, 55, 14 Cocaine analogs, isoxazolines, 60, 297 Coenzyme factor 420, synthesis, 55, 192 Colloidal media, iodination of pyrazoles in. 57, 344... 

The NIR emission intensity of the lanthanide porphyrinate complexes follows the trend Yb > Nd > Er. This agrees with observations on other luminescent lanthanide complexes and reflects the fact that the efficiency of nonradiative decay increases as the energy of the luminescent state decreases. The emission yields of the ternary lan-thanide(III) monoporphyrinate complexes with hydridotris(pyrazol-l-yl)borate or (cyclopen-tadienyl)tris(diethylphosphito)cobaltate as a co-ligand are generally higher than those of other Yb(III), Nd(III), and Er(III) complexes because the coordination environment provided by the porphyrinate in combination with the tripodal anion effectively shields the Ln + ion from interacting with solvent (C-H) vibrational modes that enhance the rate of nonradiative decay. 

In complex 23, each copper atom is roughly square planar, with apical contacts involving some of the cartoonylic oxygen atoms of the dcmpz ligands for the external copper(II) centers. The synthesis, characterization, and magnetic properties of a series of Cobalt(II) complexes containing the pyrazolate anion... 

A detailed study of the effect of coordination to a [Rh(NH3)5] center of a range of imidazoles and pyrazoles has been reported. The relative o and tt components controlling the pK of the coordinated heterocycle are discussed and compared with related cobalt(III) and ruthenium(III) complexes. The addition of hydroxide to the ligand in a range of 5-nitro-1,10-phenanthroline complexes has been described. It is proposed that attack upon [Ru(bipy) (5-nitrophen)3 ] can occur at the 4- or 7-positions in addition to the expected 6-position of the Meisenheimer adduct. The spectroscopic data supporting this proposal do not appear to be unambiguous. Finally, the displacement of halide from coordinated 4-halo substituted pyridines has been developed into a new synthetic method. 

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