Poly methane ligands

Although the poly(pyrazolyl)borate complexes of iron(II) have been well known for many years, [1] it is only recently that the complexes with the tris(l-pyrazolylmethane ligand, HC(pz)3, [45-48] have been studied in detail. It should be noted that poly(pyrazolyl)methane ligands, such as the tris(l-pyrazolylmethane ligand, are neutral, whereas the poly(pyrazolyl)bo-rate ligands, such as the tris(l-pyrazolyl)borate ligand, HB(pz)3", are monoanions. As a consequence, the metal(II) poly(pyrazolyl)methane complexes are dications and often have quite different properties from those of the analogous metal(II) poly(pyrazolyl)borate molecular complexes. But, in spite of these differences there are often very close structural similarities between the dicationic complexes and the neutral complexes. Therefore the study of the pyrazolylmethane complexes will parallel that of the borate complexes discussed above. 

The bis(pyrazolyl)silanes Bps (Scheme 24) were readily prepared from the reaction of Me2SiCl2 and two molar equivalents of the corresponding alkali metal pyrazolates.262 Both Bps and BpsMe2 ligands were isolated in excellent yield. They are stable in dry air for at least six months and soluble in aliphatic and aromatic hydrocarbons, acetonitrile, dichloromethane and ethers. However, they slowly decompose in acetone or in the presence of solvents with acidic protons such as water and alcohols, an important difference with respect to the analogous poly(pyrazolyl)methane ligands. Both bidentate ligands have been used to prepare zinc(II) derivatives. 

Figure 2.42 Luminescent mesomorphic tetrahedral zinc(II) complexes with poly-catenar pyrazole ligands (a) or bis(pyrazolyl)methane ligands (b)...

Metallacyclic complexes 116 and 117 have been obtained starting from nitro- and nitrosobenzene " and an intermediate of the type 118 was detected. Novel olefin palladium(ii) complexes 119 containing poly(pyrazol-l-yl)borate and -methane ligands were obtained. ... 

A series of complexes (Chart 5) have been reported that comprise both a poly(pyrazolyl)borate ligand and an intramolecularly chelating, monoanionic coligand. These are typically obtained via halide displacement and dimer cleavage by the respective sodium or potassium poly(pyrazo-lyl)borate salt, a means by which 462—466,45 467—469,143 and 470 479144 145 were each prepared in good yield, while the related poly (pyrazolyl)methane complexes 480+— 483+ were isolated as their perchlorate salts in the presence of NaClO 145... 

TCNE = Tetracyanoethylene Dipdba = 4,4 -diisopropyl(di-benzylideneacetone) TMM = Trimethylenemethane dppm = (Diphenylphosphino)methane MMLCT = Metal-metal bond to ligand charge-transfer Tp = Hydrido(trispy-razolyl)borate Tp = Hydridotris(3,5-dimethyl-pyrazolyl)bo-rate BAr = (3,5-triflnoromethylphenyl)borate ttab = l,2,4,5-tetrakis(l-iV-7-azaindolyl)benzene tmeda = Tetra-methylethylenediamine bpma = Bis(pyridyhnethyl)amine TFE = Triflnoroethanol dtbpm = Bis(di-terr-butylphosphi-no)methane dmpe = Bis(dimethylphosphino)ethane dcpe = Bis(dicyclohexylphosphino)ethane triphos = Bis(2-diphe-nylphosphinoethyl)phenylphosphine COD = 1,5-cycloocta-diene dppbts = (Diphenylphosphinobutane)tosylate sodium PPE = Poly(jo-phenylene ethylene). 

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