Studies on M eta1Ca rboxyl ates. Part 1V.l Pyr id i ne-2,6-d ica r boxylate Complexes of Cobalt(ii), Nickel(ii), Rhodium(ii), and Rhodium(1ii). Synthesis, Spectral and Magnetic Properties, and a Study of Rhodium 3d

The lanthanide( 111) acetates react with aqueous solutions of pyridine-2.6-dicarboxylic acid (dipicoiinic acid, dpcH,) to afford two series of complexes, Ln(dpc)(dpcH).GH,O (Ln = La, Ce, Pr, Nd, Sm, Gd, and Tb) and Ln(dpcH),,H,O (Ln = Sm, Gd, Tb, Dy, Ho, or Yb). The samarium complex Sm(dpc)(dpcH).GH,O was isolated in a-and @-forms. X-Ray powder data show that within each series the complexes are isostructural. The electronic absorption spectra of the complexes have also been recorded. The X-ray photoelectron spectra of the dehydrated species Ln(dpc)(dpcH) (Ln = Ce or Pr) and Dy(dpcH), have been investigated and the C(ls), N(1s). and O ( l s ) binding energies measured. Attempts to determine the Ce, Pr, and Dy 4s binding energies were unsuccessful. Related measurements of the C ( 1s). N (Is), and O(1s) binding energies of several pyridine carboxylates of manganese(ll), cobalt(i1). nickel(ii), and silver(i1) are also described.PYRIDINE-2,6-DICARBoxYLIc ACID (dipicolinic acid) can co-ordinate as a neutral (dpcH,), monoanionic (dpcH), or dianionic (dpc) terdentate donor. Our interest in this molecule arose from its stabilization of the silver@) oxidation state to form a complex which can be formulated as Ag(dpc)(dpcH,),xH,O (x = 1 or 4).2-4 Subsequently, we found that its complex with nickel(II), bis-(pyridine-2,6-dicarboxylat 0) nickel( 11) trih ydrate, is best represented as Ni(dpcH),,SH,O. The versatile bonding characteristics of this ligand prompted us to investigate its metal complexes in some detail and in the present report we describe our studies on several of the lanthanide (111) derivatives. EXPERIMENTALThe hydrated lanthanide acetates, of general formula Ln(OAc),,xH,O, were obtained from Apache Chemicals, Inc., Illinois or Bradford Scientific, Massachusetts, and pyridine-2,6-dicarboxylic acid was from the Aldrich Chemical Company. These reagents were used without further purification.Complexes of General Formula Ln(dpc) (dpcH), 6H20.-These complexes were prepared for Ln = La, Ce, Pr, Nd,

I d i a n a 47907)Summary An unusual redox reaction of P-rhenium(Iv) we studied its reactivity towards a variety of donor molechloride with triphenylphosphine in acetonitrile is cules using acidified methanol or acetone as reaction solvent. described, and the crystal structure of one of the reduc-Under these conditions, the reaction products were typical tion products, ReC1,,2PPh3,MeCN shows that this moleof those formed by the rhenium(II1) anion [RezC1,I-) ;2 in cule contains o-bonded acetonitrile.no instances did we isolate rhenium(1v) complexes of the type ReC1,,2L. We now find that by using strictly anhydrous conditions, the reactions of this halide are FOLLOWING our chance discovery of the new halide p-ReCl,,l

The reactions of rhenium(III) chloride with pyridine, 0-and -picolines, isoquinoline, quinaldine, and benzimidazole result in the formation of dark green-black rhenium(II) derivatives of stoichiometry [ReCl2-L]". The appropriate amine hydrochloride is in all instances isolated as an organic by-product of these reductions. Related reactions are also observed using -picoline, 2,6-lutidine, 2-vinylpyridine, and quinoline but the dark blue-purple reaction products precipitate before reduction to rhenium(II) is complete. Heterocyclic tertiary amines of low pXa (less than 3), such as pyrazine, 2,6-dimethylpyrazine, and 3-chloropyridine do not undergo redox reactions with rhenium(III) chloride but instead form the simple adducts Re3Cl9-3L. By using very short reaction times, the reaction intermediates Re3Cl9-3py and [ReCl2-5-py]n have been isolated from the pyridine system. All the above products react with methanolic HC1 to afford the rhenium(III) salts ((amine)H) 2 Re3 Cl,,. On the basis of spectral, magnetic, and conductivity studies and the above reactions with methanolic HC1, it is proposed that the phases [ReCl2L]n and [ReCl2iS-py]" are best formulated as polymeric [Re3Cl6'3L]n and [Re3Cl7-s-3py]n. The X-ray photoelectron spectra of Re3Cl9-3L (L = pyrazine, dimethylformamide, and triphenylphosphine) and [Re3Cl6-3L]n (L = pyridine, -picoline, and benzimidazole) have been investigated and a comparison has been made of the rhenium 4fs/2<7/2 and chlorine 2p,/2i3/2 binding energies. These chlorine spectra have enabled chlorine atoms in different environments to be distinguished.

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