A method is described for the simultaneous determination of rhenium and chlorine in complex compounds. By determining atom ratios, it is unnecessary to weigh samples. The advantages of this method when applied to air-unstable compounds are described.

Studies on trans-Re(acac),CI, in the solid state, solution, and gas phases by spectroscopic and classical physical methods show that the compound is a monomer and not a dimer as previously claimed (2). cisRe(acac),CI,, Re(acac),Br,, Re(acac),I,, and Re(dbm),CI, have been prepared for the first time and corresponding physical measurements are reported.Les etudes effectukes sur le (runs-Re(acac),CI,, en phase solide, en solution et en phase gazeuse au moyen des methodes spectroscopiques et physiques classiques, montrent que ce compost est un monomere et non un dimere comme cela avait CtC annonce (2). Les composes nouveaux, cis-Re(acac),CI,, Re(acac),Br,, Re-(acac),I,, et Re(dbm),CI,, ont kt6 prepares et les mesures physiques correspondantes sont rapportees.

Pure samples2 of Re(hfac), and Re(acac), have been prepared and their physical properties studied by ultraviolet-visible and infrared spectroscopy, mass spectrometry, magnetic susceptibility measurements, and X-ray diffraction. The compounds are monomeric and the physical properties may be explained if the rhenium atom sits in an essentially octahedral ligand field. Re(hfac), has a hexagonal unit cell and the acetylacetone complex adopts the monoclinic cell of the a-form of the three typical crystal structure types which Astbury (1) observed for trispentane-2,4-dionatometal(II1) compounds. The properties observed for trispentane-2,4-dionatorhenium(lI1) differ from those reported previously (2, 3). The difficulties experienced in obtaining pure Re(C5H702), were caused by the ease with which the material is oxidized.On a prCparC des Cchantillons purs2 de Re(hfac), et Re(acac), et ttudit leurs proprittts physiques par la spectroscopie ultraviolette-visible et infrarouge, la spectrometric de masse, des mesures de susceptibilitt magnttique et la diffraction de rayons-)<. Les composes sont monomeriques et on peut expliquer ies proprittts physiques si I'atome de rhenium se trouve dans un champ de ligand essentiellement octatdrique. Re(hfac), posstde une maille hexagonale et le complexe acttylacetone adopte la maille monoclinique de forme a des trois genres de structure cristalline typiques que Astbury (I) a observt pour les composts trispentane-2,4-dionatomttalliques. Les proprittts observkes pour le trispentane-2,4-dionatorht.nium(II1) diffirent de celles rapporttes prtctdemment (2, 3). Les difficultts rencontrtes pour obtenir le Re(C5H702), pur furent caustes par la facilitt avec laquelle le matCriel est oxydt.

Die sublimierbaren Titelkomplexe (I) werden durch Erhitzen (1 l0 bzw. 175°C) von Dichloro‐bis‐[acetylacetonato]‐Re(IV) oder Dichloro‐hexafluoracetylacetonato‐bis‐[triphenylphosphin]‐Re(III) mit dem Na‐Salz der Liganden im Vakuum gebildet (Ausbeute 40%).