Ligand structures tridentate ligands

The cationic aqua complexes prepared from traws-chelating tridentate ligand, R,R-DBFOX/Ph, and various transition metal(II) perchlorates induce absolute enantio-selectivity in the Diels-Alder reactions of cyclopentadiene with 3-alkenoyl-2-oxazoli-dinone dienophiles. Unlike other bisoxazoline type complex catalysts [38, 43-54], the J ,J -DBFOX/Ph complex of Ni(C104)2-6H20, which has an octahedral structure with three aqua ligands, is isolable and can be stored in air for months without loss of catalytic activity. Iron(II), cobalt(II), copper(II), and zinc(II) complexes are similarly active. 

The crystal structure of a mono(cyclopentadienyl)zirconium complex containing a novel Me2Si-linked bis(amidinate) ligand was reported (Scheme 203). In this compound the central Zr atom is octahedrally coordinated with the bis(amidi-nate) acting as a tridentate ligand. ... 

Bulk electrochemical reduction of the platinum(IV) complex of the tridentate ligand l,l,l-tris(aminomethyl)ethane(tame), [Pt(tame)2]4+, leads to the quantitative formation of [Pt(tame)2]2+ (28), in which one of the amine donor groups in tame remains noncoordinated.141 The X-ray structure of the diprotonated complex [Pt(Htame)2]4+, as its tetrachlorozincate(II) salt, is also reported. 

A A -coordi nation was found in the zinc complex of 2,2 -dipyridyl diselenide, [ZnLCl2].214 The tridentate ligand 6-(2-aminophenyl)-2,2 -bipyridine contains two pyridyl and one aniline donor ligand to form a complex of the form [ZnL2]2+. The X-ray structure shows a distorted octahedral metal center with each ligand twisting from planar to accommodate the meridional binding.215... 

We were recently able to isolate and structurally characterize a series of [CuI(PMDETA)(7i-M][BPh4] complexes (M = styrene, methyl acrylate, methyl methacrylate, and 1-octene) [110,111]. Molecular structures of [Cu PMDETA) (71-methyl acrylate)] [BPhJ and [CuI(PMDETA)(7i-styrene)][BPh4] are shown in Fig. 5. In all complexes, PMDETA acted as a tridentate ligand, while the... 

Owing to the 7tCc-ocrc CT interactions, the usual equivalence between the two Kekule structures of benzene is broken and the ring distorts strongly to D3h symmetry, with pronounced alternation (by 0.02 A) of C=C bond lengths. Complexes of this type are evidently closely related to the metallocene sandwich compounds discussed elsewhere in this book (Section 4.9.5), with the benzene molecule described as a tridentate ligand in the language of metal coordination chemistry. 

The crystal structures of [Fe(2,6-bis(triazol-3-yl)pyridine)2](N03)2.4H20 and [Ni(2,6-bis(triazol-3-yl)pyridine)2]Cl2.3H20 revealed that the tridentate ligand coordinates to the metal(II) ion using both N-4 atoms of the two... 

In a similar investigation of the tautomeric tridentate ligand 2 -hydroxyphenylazo-2-naphthol (5.65 in Scheme 5.17), the first and second acidic dissociation constants (pKa) related to the two hydroxy groups in the parent structure (X = H) were found to be 11.0 and 13.75 respectively. On introduction of an electron-withdrawing substituent (X) the first dissociation constant decreased from 11.0 to 10.55 (X = Cl) or 7.67 (X = N02). The stability constants (log K1 1) of the derived 1 1 complexes were dependent on the metal ion introduced [46], being particularly high for nickel(n) at 19.6 and copper(II) at 23.3. 

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