Mononuclear structures tridentate ligands

In an attempt to change the electronics of the chromium atom, we are replacing the carbon based cyclopentadienyl ring with ligands containing harder donor atoms. For example, we have employed the tris(pyrazolyl)borate moiety, an isoclectronic replacement for Cp featuring tridentate N-coordination.[9] Figure 2 shows the molecular structure of Tp SU Cr-Ph, a representative Cr° alkyl. It will be noted, that this complex is mononuclear, due to the steric protection of the extremely bulky tris(pyrazolyl)borate. 

The gold(III) complexes, ]Au(C N C)L ]" and [Au2(C N C)2(P P)[(C104)2 are emissive in acetonitrile at low temperature. The frozen-state (77 K) emission spectra of the mononuclear complexes [Au(C N C )L [" show well-resolved vibronic structures with spacings in the 1100-1300 cm range, which correlate with the skeletal vibrational frequency of the tridentate C N C ligand. By comparing the emission... 

From this perspective they reported the structure (complex (791) Cu-Cu 10.061 A) of a m-xylyl-based TACN ligand.583 Structures of four mononuclear copper(I) complexes ((792)-(795)), supported by tridentate macrocycle, were also reported by this group. They investigated their oxygenation behavior and in each case clean formation of side-on peroxo-dicopper(II) species was demonstrated.416... 

The reactions of mercury(II) salts with oligo-amines afford informative examples for the fact that counterions induce the formation of a distinct complex or select a distinct complex in an equilibrium to crystallize with. Thus, Hg11 acetate with dien under exactly the same reaction conditions, in the presence of C104- or PF6-, yields the dinuclear complex [Hg2(dien)3](C104)4 or the mononuclear species [Hg(dien)(H20)](PF6)2, respectively, both characterized by IR, H, and 13C NMR spectrometries, by fast-atom bombardment (FAB) MS, cyclovoltammetry, and X-ray structure analyses.209 In the first compound Pna2, Z = 4), one Hg adopts five-coordination with one tridentate and one bidentate dien ligand, which with the remaining N-donor binds to the... 

The selective S3mthesis of tri- and dichlorotitanium complexes 140-142 bearing chiral tridentate Schiff base ligands derived from (lf ,25)-( )-l-aminoindanol (Fig. 20) has been recently reported. X-ray structural studies of these complexes revealed a mononuclear feature with an octahedral coordination sphere at the metal center, and a meridional occupation of the Schiff base. Surprisingly, though these complexes lack the typical ROP-initiating units such as aUcoxides or amides, they are effective catalysts for the controlled ROP of L-lactide, as evidenced by the linearity of the molecular weight versus [l-LA] [Ti] ratio as well as the narrow PDIs (1.17-1.33) [127]. 

The oxyanions as ligands may be classified according to (a) the structural type of the oxyanion (X02, X03, X04 or X06) (b) the coordination number of the oxyanion (1-18), i.e. the number of metal atoms to which a single oxyanion may be coordinated (c) the mode of coordination of the oxyanion, i.e. monodentate, bidentate, tridentate, etc. and (d) the number of oxyanions per metal atom, the stoichiometry p, from one to six, i.e. [M(XO ) ]. Table 1 lists the oxyanions that will be considered in this section according to their structural types, with their approximate stereochemistry and point group symmetry. The carbon-containing oxyanions will be described in Chapter 15.6, and the cyanates in Chapter 13.5, For reasons of space this review will be primarily restricted to mononuclear oxyanions. Figures 2-5 illustrate the mode of coordination of the oxyanions as a function of their coordination number 1-18. 

---