The solid state reaction between hexaamminechromium(III) complexes and L-α-alanine

Abstract

The solid reaction between [Cr(NH 3) 6]X 3(X − = Cl, I, SCN and NO 3) and L-α-alanine was studied under continuous rise in temperature and isothermal heating. Under continuous rise in temperature, the main products were [Cr(NCS) 3-(NH 3) 3] (X − = NCS) and [Cr(L-ala) 3] (X − = NO 3), when [Cr(NH 3) 6]Cl 3 and [Cr(NH 3) 6]I 3 as starting complexes were used; in both cases only the decomposition proceeds. Under isothermal heating at 150°C the main products were [CrCl(NH 3) 5]-Cl 2 (X − = Cl), [Cr(NH 3) 6]I 2 (X − = I), [Cr(NCS) 3(NH 3) 3] (X − = SCN) and [Cr(L-ala) 3] (X − = NO 3). In those matrix reactions, the ease of anion coordination was: SCN − > Cl − > I − > alanine. For the synthesis of tris(alaninato)chromium(III) complex the most desirable starting complex was [Cr(NH 3) 6](NO 3) 3. The solid state reaction between [Cr(en) 3]X 3 type complexes and NH 4X (X − = F, Cl, Br, I and SCN), KX (X − = Cl, Br and I), and NaSCN have been reported by Wendlandt and Stembridge 1. They reported that the reaction product in most cases, was cis-[Cr(en) 2Y 2]X, where Y and X are the same or different anions, depending upon the matrix material employed and the thermal matrix method appears to be a useful new route for the synthesis of bis(ethylendiamine(chromium(III) complexes. In the previous paper 2, the solid state reaction between [Cr(NH 3) 6](NO 3) 3 and L-amino acids has been utilized in the preparation of tris(amino acidato)chromium(III) complexes. The preparation of [Cr(L-ala) 3] by the solid state reaction between [Cr(NH 3) 6](NO 3) 3 and L-alanine have been reported. No studies on the effect of the counter-ion have been reported. In this paper, various hexaamminechromium(III) complexes, [Cr(NH 3) 6]X 3 (X − = Cl, I, SCN and NO 3), were heated with L-α-alanine under continuous rise in temperature and under isothermal heating at 150°C for studies on the ease of anion coordination. It will seen that the anion which replaces the ammonia in the hexaamminechromium(III) complex comes from either the alanine or counter-ion.