Internal Hindered Rotation of Ketimido Ligands

4 INTERNAL HINDERED ROTATION OF KETIMIDO LIGANDS 2.4.1 Ketimido Complexes of Titanium 

Ketimines HN=CR R can be considered as formal analogs of secondary amines however, the nitrogen atom in ketimines is sp -hybridized, which can impart some specific features in the complexes of Group 4-6 d transition metals. 

the reaction between CpTiX3 and HN=C BuR (or LiN=C BuR) resulted in a new class of monocyclopentadienyl titanium catalysts for olefin polymerization [CpTi(N=C BuR)X2] [37]  

The X-ray crystal structure of the related compound Cp-( Bu BuC=N)TiCl2 [38] showed the complex to be monomeric with a near-linear Ti-N-C linkage of 171.3(4)°. In the solid state, the plane of the ketimide ligand is approximately perpendicular to the Cpcentroid Ti vector. The authors noted that the relatively short Ti-N bond length of 1.872(4) A was consistent with some double bond character in this linkage. 

Ketimines react with tungsten oxotetrafiuoride according to the scheme typical of the secondary amines [39] (see Section 2.1). The final stage of the reaction is the formation of a complex anion [WOp4(N=CR R )] (R = Ph, R = Ph, Et, para- and ortho-Cii%C(,Y i) in which the deprotonated ketimine is coordinated in the cis position with respect to the double-bonded oxygen atom. 

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