Rhenium III Bromide

KaReBre + 2AgN03— AgaReBre + 2KNOa SAgaReBre 6AgBr + fBra -f ResBra 

Submitted by RICHARD J. THOMPSON, RONNIE E. FOSTER, and JAMES L. BOOKER  

Trirhenium nonabromide has been made (1) by direct combination of the elements (2) by the thermal decomposition of rhenium(V) bromide, obtained by treating elemental rhenium with bromine at 650° or (3) by the thermal decomposition of silver hexabromorhenate(IV), obtained from the metathesis of silver nitrate with potassium hexabromorhenate(IV). Of these methods, (3) has proven to be the simplest and most efficient route to pure trirhenium nonabromide. The following procedure is superior to that previously given, in that simpler equipment is used and larger quantities can be processed, with a resultant saving in time. 

Ten grams (0.0134 mol) of solid potassium hexabromo-rhenate(IV) is added slowly to a vigorously stirred solution of 5.5 g. (0.032 mol) of silver nitrate in 50 ml. of concentrated nitric acid and 200 ml. of water. The slurry is stirred for 10 minutes after addition of the solid. After standing, the clear supernatant is decanted. The brown solid is transferred onto 

Into a size 6A porcelain boat (88 X 13 X 10 mm.) is placed 10.0 g. (0.0113 mol) of Ag2ReBre (as much as 15 g. may be processed readily), and the boat is positioned near the sealed end of a 25 X 300 mm. Pyrex tube fitted with an inner 29/44 S.T. sleeve joint. The tube is connected to a mechanical vacuum pump (capable of reducing the pressure to ca. 50 n) via either a trap cooled by liquid nitrogen or a trap cooled by a Dry Ice-isopropyl alcohol slush, which is in turn connected to an 11-mm. Vycor combustion tube packed with copper gauze and maintained at 600° by means of a furnace. (Either protective system between the tube and the pump will serve to remove bromine, one of the reaction products.) 

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Rhenium (III) bromide is, as expected, more easily ionized, so that in DMSO the bisarsenate complex Re3Br3(AS04)2(DMS0)3 is readily produced 48). 

Rhenium(III) bromide reacts with silver arsenate in acetone with precipitation of silver bromide (107). Addition of dimethylsulfoxide to the resulting solution gives a red amorphous solid of stoichiometry [ (CH3) 2SO] 2Re3Br3 (AsOi ) 2 f indicated by its electronic spectrum still to contain the rhenium(III) triangle. 

A novel structure 9 has been postulated for this complex on the basis of infrared data. Similar compounds can be obtained from rhenium(III) bromide and... 

Rhenium(iii) bromide ReBrj 13669-49-8 426.919 red-brn monoci cry 600 subi 6.10 s ace, MeOH, EtOH... 

The rhenium(III) halides, with Cl, Br, and I are all well established. All three can be prepared by a variety of methods and all have been shown to have structures built of Re units of D3 symmetry with Re=Re double bonds. The structure of the crystalline bromide was only recently reported.6 Although these halides are often designated as ReX3, especially in older literature, they should be written as ReA, since only on this basis does their chemistry make sense. 

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