Ligands meridional tridentate

The potentially coordinating neutral O or S functions constitute the labile part (2 Y) of the hemilabile chelate ligands, which can thus adopt either a bidentate or a meridional tridentate function (see and Fig. 49.1 [20]). 

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... 

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]. 

An X-ray structure determination of 465b reveals that the central dimetalated aryl ligand system provides tridentate meridional NCN -coordination to both tin centers. The N—Sn distances (2.392 and 2.395 A) and the NSnN angles (152.0°) are close to those found for the triorganotin cation in salt 463. 

Although several examples of complexes containing the [Mn202]"" core type have been studied, only one has been found to catalyze O2 evolution in water. The complex [(terpy)(H20)Mn (/u,-0)2Mn (0H2)(terpy)] + contains the tridentate terpyridine ligand that coordinates to three meridional sites on Mn and thus positions the two terminal aquo ligands trans to the /tr-oxo bridges. The oxidation of this complex by or OCl in water was shown to produce... 

Cyclometallation, which provides multidentate ligands containing carbon donors, has been known as a useful synthetic method for preparing organometallic complexes. A noticeable extension in such a category, which substantially facilitates the recent development of organoplatinum chemistry, is the pincer-type ligands, which allow tridentate meridional chelation with various donor combinations to the metal. ... 

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