L.L. Pytlewski

Metal complexes of aromatic amine n-oxides

Darstellung, Eigenschaften, Substituenteneffekte und Donoreigenschaften aromatischer Amin-N-oxide werden zusammenfassend behandelt.

Spin-free and spin-paired transition metal perchlorate complexes of 2,6-lutidine N-oxide

Abstract Cationic transition metal complexes of 2,6-lutidine N-oxide (2,6-LNO) were synthesized and studied. For the monomeric tetra-cordinated cations of the type [M(2,6-LNO) 4 ] 2+ (M = Fe, Co, Ni, Cu, Zn), stabilization of an essentially planar configuration is interpreted in terms of a combination of steric and electronic effects. The MO 4 grouping in the high-spin Cu II and the low-spin Ni II complex is assigned a D 4h symmetry. Evidence is presented in favor of a monomeric structure, with essentially planar MO 4 groupings for the high-spin Co II and the partially spin-paired Fe II complex. Coordination of one monodentate OClO 3 group in [Mn(2,6-LNO) 4 (OClO 3 )] + is attributed to the anticipated instability of a planar configuration for the Mn II ion. Cr III forms a hexacoordinated cationic complex. Finally, the formation of tetracoordinated Ni II complexes with pyridine N-oxide and its monosubstituted derivatives is favored in triethyl orthoformate solution.

Chromium(III) and iron(III) perchlorate with the mono-N-oxides of 2,2′-bipyridine and 1,10-phenanthroline

Abstract 2,2′-bipyridine- and 1,10-phenanthroline-mono-N-oxide (bipyNO and phenNO, respectively) chelates with Cr(III) and Fe(III) perchloratws were synthesized and characterized by means of spectral, magnetic and conductance studies. The new complexes are of the types [M(bipyNO)3](CIO4)3 2H2O and [M(phenNO03] (CIO4)3 (M = Cr, Fe). the mono-N-oxides act as bidentate O,N-chelating agents. The bipyNO complexes contain lattice water. The UV bands of bipyNO exhibit larger shifts and splittings tahn those of phenNO, upon metal complex formation. BipyNO exisrs in the trans-form in the crystal and assumes a configuration close to the cis-form in its metal chelates, whereas free phenNO is rigidly held in the cis-form in the crystal, and has the same conformation in its chelates. The electronic spectra of the complexes are characterized by stron metal-to-ligand charge-transfer bands. Approximate Dq parameter calculations for the Cr(III) complexes indicate that bioyNO and phenNO are weaker ligands than the parent bases and stronger ligands than the corresponding N,N-dioxides. The Cr(III) complexes are magnetically normal, but the Fe(III) compounds ehibit temperature-dependent magnetic moments (3.02-3.67 BM for the bioyNO acid, 1.98-2.52 BM for the phenNO complex, over the temperature range 80-313°K), wgich were attributed to the existence of spin-free-spin-paired equilibria.

Nicotinic and isonicotinic acid n-oxide interactions with 3d metal perchlorates[1]

Interactions of nicotinic or isonicotinic acid N-oxides (N-nicOH and N-inicOH, respectively) with 3d metal (II) perchlorates in ethanol-triethyl orthoformate lead, in most cases, to partial substitution of perchlorate with nicotinate (N-nicO) or isonicotinate(N-inicO) N-oxide anionic groups. These reactions led to the isolation of the following new metal complexes: Ni(N-inicOH)3(ClO4)2·3H2O: the only true adduct of the series, apparently polynuclear, with both unidentate terminal and bidentate bridging N-inicOH, bridging O2ClO2 ligands, ionic ClO4− and lattice water. Complexes with exclusively anionic ligands of the type (ClO4) (MMn, Cu for LN-nicO; MCu for LN-inicO), with both terminal and bridging L, ionic and unidentate coordinated perchlorate, and aqua ligands. The rest of the complexes are of the mixed ligand type, i.e.: [H2O)2(O3ClO)M(N-nic)2M(N-nicOH)(OH2)2] (ClO4) (MCo, Ni), with bridging N-nicO, terminal N-nicOH,-OClO3 and aqua ligands, and ionic ClO4−; M4(N-inicOH) (N-inicO)5 (ClO4)3. 4H2O (MMn, Co, Zn), polynuclear with exclusively bridging organic ligands, terminal aqua and bidentate perchlorato groups, and ionic ClO4−; and, Zn4(N-nicOH)N-nicO)5(ClO4)3. 10H2O, probably tetrameric, with four bridging and one terminal N-nicO groups, and terminal N-nicOH, aqua and =O2ClO2 ligands, as well as ionic ClO4−. With the exception of the latter complex, which is hexacoordinated, the new metal complexes appear to be pentacoordinated. The likely structural types proposed for these compounds were based on the overall spectral and magnetic evidence obtained.

Characterization studies of adenine complexes with 3d metal perchlorates

A series of adenine (LH) complexes with 3d metal perchlorates were prepared by refluxing solutions of the metal salts in ethanol-triethyl orthoformate with the ligand for 2–5 days. Our studies indicate that, depending on the ligand to metal molar ratio employed and the duration of the refluxing step, complexes with either neutral LH or anionic L− can be obtained. Among the new complexes, Cu(LH)2(ClO4)2·C2H5OH appears to be of the familiar dimeric type with quadruple bridges of N(3), N(9)-bonded LH, one terminal -OClO3 ligand per Cu2+ ion and lattice ethanol (μeff = 1.66 μB at 298K.). The Fe3+ complex (μeff = 2.39 μB) seems to be also a dimer of the [(O2ClO2)(LH)2FeL2Fe(LH)2(O2ClO2)] type, with N(9)-bonded terminal and N(y), N(9)-bonded (y = 1, 3 or 7) bridging adenine. A similar type of bridging (N(y), N(9)-bonded) adenine is also present in the probably double-bridged dimeric FeL(ClO4)·C2H5OH·2H2O complex (μeff = 4.86 μB), and a number of presumably linear, single-bridged polymers of the M(LH)2(ClO4)2·χC2H5OH (x=2 for M = Mn; x=3 for M = Co) and ZnL(ClO4)·C2H5OH·3H2O types. However, the two remaining complexes of the ML(ClO4)·C2H5OH·2H2O (M = Co, Ni) type, involve adenine apparently coordinated through the NH2 nitrogen. For these compounds, linear polymeric single-bridged structures with N(6), N(z)-bonded (z is most probably 9) bridging L, were considered as likely. The ambient temperature magnetic moments of the complexes considered as linear polymers range from slightly below normal to normal, but it is anticipated that studies at 300-80K. will reveal magnetic exchange interactions in general, in view of the established spin-spin coupling in the corresponding purine complexes.

Further characterization of some metal perchlorate complexes with organophosphoryl ligands

Abstract Supplementary characterization studies of some phosphonate and phosphate ester metal complexes and Fe(TPPO)4(ClO4)3 (TPPO = triphenylphosphine oxide) led to the following conclusions. M(DIMP)4 (ClO4)2 (DIMP = diisopropyl methylphosphonate) complexes involves coordinated perchlorate and were formulated as [M(DIMP)4(OClO3)](ClO4). Dimethyl methylphosphonate (DMMP) complexes of the above type and Fe(TPPO)4(ClO4)3 dot not exhibit any evidence favoring the presence of coordinated perchlorate. For these compounds the presence of a bi- or poly-nuclear complex cation of the type [ML4]nx+, involving both terminal and bridging ligand groups and coordination number five for the metal ions, is proposed. Far infrared studies of the above complexes and a number of [ML5](ClO4)2, [ML6](ClO4)2,3 and [ML4(H2O](ClO4)2 complexes with DMMP and trimethyl phosphate and tentative assignments of vM−O are also reported.

Metal nitrate and thiocyanate complexes with 2,6-lutidine n-oxide

Abstract Complexes formed by interaction of excess 2,6-lutidine N-oxide (LNO) with various metal nitrates and thiocyanates were prepared and characterized by means of spectral, magnetic and conductance studies, as follows: [M(LNO) 6 ](NO 3 ) 3 (M = Cr, Fe), involving distorted octahedral complex cations and ionic nitrate; [M(LNO) 2 (ONO 2 )(O 2 NO)] (MMn, Co, Ni, Zn), pentaco-ordinated neutral complexes, containing one mono- and one bi-dentate nitrato groups; [Cu(LNO) 2 (ONO 2 ) 2 ], planar, and [Cd(LNO) 4 (ONO 2 ) 2 ], hexaco-ordinated, with monodentate nitrato ligands; [(LNO)(SCN) 2− Mg(LNO) 2 Mg(NCS) 2 (LNO)], dimeric, pentaco-ordinated, LNO-bridged, with N-bonded thiocyanate; [(NCS) 2 Hg(LNO) 2 Hg(SCN) 2 ], dimeric, tetrahedral, LNO-bridged, with S-bonded thiocyanate; [(LNO) 2 (SCN)M(NCS) 2 M(NCS)(LNO) 2 ] (M  Co, Ni), pentaco-ordinated dimers with terminal isothiocyanato as well as bridging NCS groups; and [Cu(LNO) 2 (NCS) 2 ] x , hexaco-ordinated polymeric complex with bridging NCS ligands. [Fe(LNO) 6 ](NO 3 ) 3 is the first example of a compound characterized by the Fe III O 6 moiety and exhibiting spin-free-spin-paired equilibria; the polymeric [Cu(LNO) 2 (NCS) 2 ] x exhibits a subnormal magnetic moment. The influence of the steric effects of LNO on the types of complexes formed is discussed.

Purine complexes with divalent 3d metal chlorides

Abstract A series of purine (puH) complexes with 3d metal(II) chlorides were prepared by interaction of ligand and metal salt in ethanoltriethyl orthoformate. 1:1 complexes of the general type M(puH)Cl 2 ·nH 2 O (n = O for M = Zn; n = 1 for M = Fe, Co, Cu; n = 2 for M = Mn, Ni) were isolated. Spectral evidence favors a tetrahedral configuration for Zn(puH)Cl 2 , and coordination numbers five for M(puH)Cl 2 ·H 2 O (M = Fe, Co, Cu) and six for M(puH)Cl 2 ·2H 2 O (M = Mn, Ni). The new paramagnetic metal ion complexes are characterized by normal ambient temperature magnetic moments for high-spin 3d 5 –3d 8 compounds or the 3d 9 configuration. A linear oligomeric structural type, involving single-bridged MpuHMpuHsequences and exclusively terminal chloro, and wherever applicable, aqua ligands was considered as most likely for the new complexes. Probable bonding sites of the bidentate bridging puH ligands are the N(3) and N(9) nitrogens.

Diisopropyl methylphosphonate complexes of metal perchlorates

Abstract A number of crystalline metal perchlorate complexes with diisopropyl methylphosphonate (DIMP) were synthesized and found to be of the general type [M(DIMP) 4 ]ClO 4 ) 2 for divalent metal ions. Conductance measurements indicate the existence of the cation [M(DIMP) 4 ] 2+ in polar solvents. Higher-coordinated cationic complexes of DIMP with M(II) do not seem to exist because of steric hindrance from the bulky ligand molecules. I.R. data indicate that coordination to the metal ion occurs through the phosphoryl oxygen. I.R. evidence is also presented for the lowering of the symmetry of the perchlorate ion in the crystal lattice. The transition metal cationic complexes are assigned an intermediate between distorted tetrahedral and planar configuration, on the basis of magnetic and spectral evidence.

Interactions of neutral phosphonate esters with metal halides

Abstract Interaction of diisopropyl methylphosphonate with trivalent metal chlorides at 50–200°C leads to the formation of tris-(isopropoxy methylphosphonato) metal complexes. Tetravalent metal chlorides yield under similar conditions bis-(methylphosphonato) complexes. During these reactions isopropyl chloride is evolved, which is partially decomposed to hydrogen chloride and propene by the catalytic action of the complex metal chloride residue. The general insolubility and the magnetic properties of the new complexes are suggestive of polynuclear configurations, involving eight-membered phosphonate bridges and, possibly, four-membered chelate rings. A distorted O h ligand-field symmetry is assigned to the metal ions.