Tris 2,2,6,6-tetramethyl-3,5-heptanedionato chromium III

This procedure is a modification of the method reported previously for the preparation of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)chromium(III) and is based on the technique developed for the preparation of tris(2,4-pentanedionato)chromium(III).  

Skibmitted by DANNY T. FAGAN, JOANN S. FRIGERIO, and JOE W. VAUGHN Checked by ANI HYSLOPt and JAMES E. FINHOLTf 

The complex m-[Cr(en)2F2]I is a useful starting material for the preparation of compounds of the type m-(Cr(en)2FX]I (X = CP, Br, NCS, HjO, and NHs). The initial preparation of m-[Cr(en)2F2]I involved the reaction of anhydrous 1,2-ethanediamine with CrFj-xHjO that was suspended in a dry diethyl ether solution of hydrogen fluoride. Workup of the crude product from hydroiodic acid gave the desired compound. The present method, which is similar to that reported previously, utilizes the direct reaction of chromium(lll) fluoride-water (1/3.5) with excess dry 1,2-ethanediamine to yield m-[Cr(en)2F2](Cr(en)F4)-xH20, from which the desired cation can be easily isolated. This method avoids the difficulty of preparing easily oxidized Cr(II) compounds and working in an atmosphere of nitrogen. 

Powdered chromium(III) fluoride-water (1/3.5) [Alfa Products], 43.0 g (0.250 mole), is added to 52.5 g (0.875 mole) of previously dried 1,2-ethanediamine contained in a 500-mL polyethylene beaker. The 1,2-ethanediamine is dried by distillation from solid sodium hydroxide pellets. The fraction that boils from 116-118 is collected. 

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