The photochemistry of some quadrate Cr(III) complexes
Date
1970
Authors
Valentin, John Gwynfryn
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Abstract
The aquation quantum yields of [Cr(en)₂ox]⁺, [Cr(en)₂ox]⁻, cis-[Cr(en)₂Cl₂]⁺ and trans-[Cr(en)₂Cl₂]⁺ were measured in the visible region at pH 3.0 and at various wavelengths and temperatures. The results are interpreted in terms of empirical rules proposed by earlier workers.
Both [Cr(en)₂ox]⁺ and [Cr(en)₂ox]⁻ were found to give protonated monodentate ethylenediamine complexes as primary photolysis products. The φₐ(en) were found to be (1.6 ± .2) x 10⁻¹ and (2.0 ± .9) x 10⁻² respectively. No oxalate photoaquation was observed for either complex.
Cis-[Cr(en)₂Cl₂]⁺ was found to undergo both ethylenediamine and Cl⁻ photoaquation with φₐ(en) = (1.3 ± .2) x 10⁻¹ and φₐ(Cl⁻) = (1.5 ± 1.0) x 10⁻². Trans-[Cr(en)₂Cl₂]⁺ showed only Cl⁻ aquation φₐ(Cl⁻) = (3.2 ± .2) x 10⁻¹.
It was found that photoaquation of [Cr en(ox)₂]⁻ and trans-[CR(en)₂Cl₂]⁺ was accompanied by stereochemical changes, requiring water attack trans to the leaving group.