Complexes of rhenium with benzoylazo and related ligands. Crystal and molecular structures of...

Terence Nicholson, Jon Zubieta

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Title full: Complexes of rhenium with benzoylazo and related ligands. Crystal and molecular structures of the "green chelate" benzoylazo complex [ReCl2(PPh3)2(NNCOC6H4 -p-Cl)](Nα,O), of the analogous 1-azophthalazine chelate complex [ReCl2(PPh3)2(NNC8H5 N2)](Nα,N1), and of the cis-dichloro organodiazenido complexes of the type [ReCl2(PPh3)2(NNR)L] (L = NCCH3, NH3 and C5H5N). A comparison to the structure of the trans- dichloro dimethylformamide derivative [ReCl2(PPh3)2(NNCO2CH3 )(Me2NCHO)]. The structural characterization of the mixed hydrazido(1-) hydrazido(2-) complexes [ReCl2(PPh3)2(NNHR)(NHNHR′)], (R = R′ = -COC6H5; R = -COC6H5, R′ = -CO2CH3) Reaction of [ReOCl3(PPh3)2] with potentially chelating organohydrazines in ethanol-HCl solutions gives six coordinate chelate complexes of the general formulation [ReCl2(PPh3)2(NNR)]; [R = COC6H4-p-Cl, (1); R = C8H5N2, (phthalazine), (2)]. Complexes (1) and (2) display octahedral geometries with mutually trans phosphine groups minimizing steric congestion and cis-chloride ligands. The chelated hydrazido(3-) ligand occupies the remaining two coordination sites. The weakly coordinated carbonyl group in complex (1) can be displaced by two ligand types. Neutral two electron donating ligands give organodiazenido adducts such as [ReCl2(PPh3)2(NCCH3)(NNCOC 6H5)], (3). Ligands with exchangeable protons such as organohydrazines give the mixed hydrazido(2-), hydrazido (1-) complexes [ReCl2(PPh3)2(NNHR)(NHNHR′)], [R = R′= -COC6H5, (7); R = -COC6H5, R′ = -CO2Me, (8)]. Reaction of [ReOCl3(PPh3)2] with orthobromophenylhydrazine hydrochloride gives the ammonia diazenido complex [ReCl2(PPh3)(NNC6H4- o-Br)], (4), with the ammonia generated from decomposition of excess hydrazine. Methylhydrazinocarboxylate fails to give the chelate complex analogous to (1) and (2). When dimethylformamide is added to the reaction medium, two products are isolated. The insoluble, cis-chloro N-bonded DMF adduct, [ReCl2(PPh3)2(Me2NCHO)(NNCO 2Me)], (5a), which readily substitutes neutral donor ligands for the weakly coordinated dimethylformamide giving complexes such as [ReCl2(PPh3)2(C5H5 N)(NNCO2Me)], (5). From the filtrate, the trans-chloro, O-bonded dimethylformamide isomer [ReCl2(PPh3)2 (Me2NCHO)(NNCO2Me)], (6) is isolated. Complexes (3), (4) and (5) each display cis- chloro, trans-phosphine coordination, with the diazenido unit -NNR and neutral donor ligand (NH3, C5H5N and NCCH3) occupying the remaining two sites. Complexes (7) and (8) are geometrically similar to (3)-(5) with hydrazido(2-) and hydrazido(1-) ligands in a cis-arrangement. The UV-Visible spectra appear to distinguish between the metal- organodiazenido and metal-hydrazido(2-) coordination modes.

Original languageEnglish (US)
Pages (from-to)171-185
Number of pages15
Issue number3
StatePublished - 1988
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry


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