Dipicolinato(hydroxylamido‐O,N)(nitrosyl)aquavanadate—A Nitrosyl Complex of Vanadium with “side on” Coordinated Hydroxylamine

Abstract

coordinated dipicolinato ligand (dipi~)'~] and a strong band at 1530cm-' which we assign to a v(N=O) vibration. Vanadium(v) undergoes reduction with hydroxylamine in alkaline or acidic aqueous solution; depending upon the reaction conditions N2, N20, and NO (as well as NH3) may be formed [']. A vanadium(v)-hydroxylamine 1 : 1 complex has been shown to exist in acidic solution[21 but so far has not been isolated. Dipicolinato(h ydrox ylamido-O,N)(nitrosyl)aquaReaction of five-coordinated cis-dioxo(dipico1inato)vanadate(v) ion with hydroxylammonium chloride in weakly acidic solution (25 "C) affords a colorless neutral complex ( 2 ) , which on the basis of its analytical and IR spectroscopic data can be formulated as p-0x0-bis[oxo(dipicolinato)(hydroxylamine-N)vanadium(v)].In alkaline solution (I) reacts quantitatively with hydroxylamine (1:2) without evolution of gas (!) to give deep-red solutions. Addition of solid KCI or CsCl yields air stable crystalline potassium and cesium salts, respectively. The IR spectra of these salts show the characteristic bands of the The structure of the anion (3) was determined by X-ray spectroscopy (Fig. 1). Cs[V(dipic)(H2NO)(NO)(H20)] '2 H2O crystallizes in the orthorhombic space group DM-Pcmb with a=839.4(3), b=884.3(2), c= 1936.1(6)pm, 2=8. Refinement with structure factors of 1260 observed independent reflections [I > 2.58 o(I)] converged to an unweighted R value of 5.9 %.The positions of the H atoms could not be determined because of the poor quality of the crystals (platelets). The central vanadium atom is surrounded by a distorted pentagonal-bipyramidal array of tridentate dipicolinate ligands, a bidentate hydroxylamido ligand and-in the axial positions-a nitrosyl and an aqua ligand (the formal coordination number is 7) (Fig. 1). The hydroxylamido ligand is most probably coordinated as H2N-O-[51. The nitrosyl group is almost linearly coordinated, and the V-N2 bond length is relatively short. Analogous bonding has been reported for the [V(CN),NO]"-ion ["]. The H2NO-ligand is coordinated "side on" via the 0-and the N-atom, the N3-05 distance corresponds to that of the usual N-0 single bond length.The smooth reaction course in alkaline medium and the lack of formation of gaseous reaction products are considered to be indicative of an intramolecular transfer of two electrons from N-coordinated hydroxylamine to Vv (formally, V"' and NOe are formed). This is supported by the following experiment: Reaction of the V"'-complex ( 4 ) with hydroxylamine in alkaline solution likewise affords (3):351

On the Electronic Structure of NiII Complexes That Feature Chelating Bisguanidine Ligands

“…Nickel-bisA C H T U N G T R E N N U N G (diimine) complexes in particular received growing attention, among others by Wieghardt et al, who shaped the concept of non-innocent ligands. [7] Combined experimental and theoretical investigations on such systems showed that the ligand plays a significant role in the electron transfer inside the complex. [8,9] In particular, the analysis of the different electronic states and their frontier orbitals and spin-density distributions provided valuable insight into the properties of non-innocent diimine ligands.…”

Chemistry of Iron with Dipicolinic Acid. 3. Heptacoordinated Iron in [(dipicH)2FeII(OH2)] and [(dipic)2FeII2(OH2)6].cntdot.2dipicH2

“…3 In the case of dipicH2 (2,6pyridine dicarboxylic acid, dipicolinic acid) or substituted dipicH2 complexes, some cases of heptacoordination are reported in µ-hydroxo dimers of iron(III)4 and of chromium(III)5 in peroxo complexes of titanium,6 7or hydroxylamino-MO complexes of vanadium. 7 During the course of our studies of the dipicolinic acid/iron-(II) system,8 we have explored the compounds obtained by acidic degradation of [(dipic)2Fen]2~o r deriving formally from this species. We thus obtained two new complexes [(dipicH)2Fen(OH2)] (1) and [(dipic)2Fen2(OH2)6]'2dipicH2 (2), which were shown to be heptacoordinated by X-ray crystallography.…”

Studies of V(III) complexes with selected α-N-heterocyclic carboxylato NO donor ligands: structure of a new seven-coordinated pentagonal bipyramidal complex containing picolinato ligands

“…12 DPAH 2 is found to be present in many gram-positive eubacteria during their sporulation and as its calcium salt is thought to be responsible for the heat-resistant property of the spores. 13 Though the ligational behaviour of DPAH 2 towards oxovanadium() 14 and vanadium() 15 has been examined earlier, complexation of DPAH 2 with V() has not been studied. This work explores the ligational behaviour of the biologically important and chemically interesting ONO donor dipicolinic acid towards vanadium().…”