Abstract
Abstract The cyclopalladation of 1,3-bis(2-thioazobenzene)propane (L 1 H 2 ) and its methyl substituted derivative L 2 H 2 affords complexes of the type LPd 2 Cl 2 (where L represents L 1 or L 2 which have been characterised by spectroscopy and X-ray crystallography. The crystal structure of L 1 Pd 2 C 2 has revealed that each azobenzene fragment along with its thioether sulphur acts in the tridentate (C,N,S) fashion and the fourth coordination position is occupied by a chloride ion. The complexes are thus of type [Pd(C,N,S)Cl] 2 , with a Pd ⋯ Pd contact of 5.420(1) A. The metallated carbon atom exerts a strong trans influence on the PdS bond. The reaction of LPd 2 Cl 2 with am -chloroperbenzoic acid leads to smooth oxygen insertion into both the PdC bonds to give excellent yields of dinuclear azophenolato complexes o -LPd 2 Cl 2 having the coordination sphere [Pd(O,N,S)Cl] 2 . The crystal structure of o -L 1 Pd 2 Cl 2 is similar to that of L 1 Pd 2 Cl 2 but with a somewhat longer Pd ⋯ Pd distance of 5.890(1) A. The insertion reaction has a negative entropy of activation, in keeping with an associative transition state for the electrophilic incorporation of oxygen. Reduction of the azophenolato complexes with hydrazine hydrate affords the free azophenols ( o -LH 2 ) in high yields. Thus organometallic route to o -LH 2 from LH 2 is provided.
Published Version
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