Chelate angle

A] bond distances. The restricted bite distances of the xanthate ligands [the S—M—S chelate angles are 73.50(6) and 69.77(4)°, respectively] are most the likely source for the deviations from the ideal octahedral geometries. The distortions are best seen in the twists of the triangular faces, that is, 40.27(7) and 46.43(5)° for the gallium and indium structures, respectively, compared to the ideal octahedral angle of 60°. Enantiomeric pairs associate in their respective crystal lattices via S- -S contacts of 3.598(4) and 3.592(2) A, respectively. 

Table 1-3. Metal-phosphorus bond lengths and chelate angles of metal chelates of dppf... 

The main parameters describing such a coordination polyhedron are the distortion angle (p (0° and 60° correspond to the TP and TAP, respectively), bite angle a (half the chelate angle), distance h between the coordination polyhedron bases, and the metal-donor atom distance a. 

Bite angle (half the chelate angle). The average of the main structural parameters of capping fragments. 

A suitable entry into titanium and zirconium complex chemistry is the use of group IV amides and alkoxides. For example, when Ti(OEt)4 reacted with 2 equiv. of (roc)-2 in heptane, the titanium bis(disiloxide) 3 could be isolated in 91 % yield as a yellow microcrystalline material. Tbe results of the X-ray analysis (Fig. 1) of 3 confirm the expected extensive shielding of the titanium atom by the two sterically demanding disiloxide ligands. The geometry around the titanium atom is described best as distorted tetrahedral, with an 02-Til-02 chelate angle of 99° and an 02-T11-01 angle of 115.5°. 

Bite angle, natural The preferred chelation angle of a bidentate ligand determined through molecular mechanics calculations for the ligand and a positive charge occupying the position of the metal. 

As shown in structure 231, bite angle is defined as the preferred chelation angle determined only by ligand backbone constraints. In other words, bite angle is assumed to be solely based on steric factors, and any electronic preference imposed by the metal center is ignored. The natural bite angles of the ligands dppe and BISBI are about 85° and 113°, respectively. 

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