M.M. Labes

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.

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.

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.

New complexes of triphenylphosphine oxide with metal perchlorates

Abstract New metal perchlorate complexes of triphenylphosphine oxide (TPPO) were synthesized and characterized by means of spectral, magnetic, conductance and X-ray powder diffraction studies. Of particular interest is a pentacoordinated Cr(III) complex, which involves a trinuclear cation. Each Cr(III) ion is in a low symmetry trigonal bipyramidal ligand field, consisting of terminal and bridging TPPO molecules and one coordinated monodentate perchlorato group. The possibility of a polynuclear complex cation is also discussed for the Mg(II) complex on the basis of far i.r. evidence. This complex was formulated as [Mg(TPPO)4]n(ClO4)2n(n = 1,2, …). The rest of the complexes reported were formulated as follows: [M(TPPO)4(OClO3)2](ClO4) (M = Cr, Ce, In); [Fe(TPPO)4] (ClO4)2; [UO2(TPPO)4](ClO4)2; [Ca(TPPO)4(O2ClO2)]; [Th(TPPO)4(O2ClO2)](ClO4)3. In the case of the Th(IV) complex, its formulation as [Th(TPPO)4(O2ClO2)2](ClO4)2 can not be ruled out.

Penta-, hexa-, and hepta- coordinated cationic metal complexes of trimethyl phosphate

Abstract Interaction of trimethyl phosphate (TMP) with metal perchlorates in triethyl orthoformate leads to the formation of cationic complexes of the types: [M(TMP)6]n+ (M = Mg(II), Ca(II), Al(III), Cr(III), Fe(III), [Ce(TMP)6(OClO3]2+, [M(TMP)5]2+ (M = Mn, Fe, Co, Cu, Zn) and [Ni(TMP)5 (H2O)]2+. The pentacoordinated Mn(II), Fe(II), Co(II) and Cu(II) complexes are of the high-spin type. The new complexes were characterized by means of spectral, magnetic, conductance and X-ray powder diffraction studies. A distorted Oh symmetry was assigned to the hexacoordinated cationic complexes, and a symmetry closer to C4v than D3h to the pentacoordinated complex cations. Solid-state and solution electronic spectra are discussed and compared to those reported for complexes of neutral organophosphoryl esters. Steric effects influencing the stabilization of higher-coordinated cationic metal complexes become more favorable as the number of methoxy substituents in ligands of the type RR′2PO(R,R′ = CH3 or CH3O) increases.

Tetra- to hepta- coordination in dimethyl methylphosphonate cationic metal complexes☆

Abstract Dimethyl methylphosphonate (DMMP) cationic complexes with metal perchlorates of the types [M(DMMP) 4 ] 2+ (M  Ni, Cu), [M(DMMP) 5 ] 2+ (M  Mg, Fe), [M(DMMP) 6 ] 2,3+ (M  Al(III), Cr(III), Mn(II), Fe(III)), [M(DMMP) 4 (H 2 O) 2 ] 2+ (M  Co, Zn) and [Ce(DMMP) 6 (ClO 4 )] 2+ have been prepared and characterized by means of spectral, magnetic conductance and, in certain cases, X-ray powder diffraction studies. Infrared evidence indicates that coordination occurs through the phosphoryl oxygen and conductance measurements justify the formulations given above. Ligand-field symmetries assigned to the complex cations are as follows: tetracoordinated, intermediate between distorted T d and D 4 h ; pentacoordinated, close to square pyramidal; hexacoordinated, lower than O h . The ability of DMMP to form higher-coordinated complexes than other organophosphoryl compounds is discussed in terms of the favorable steric characteristics arising from the presence of methyl and methoxy groups in this molecule.

Tris-(isopropoxy methylphosphonato) complexes of trivalent rare-earth metal ions

Tris-(isopropoxy methylphosphonato) rare earth complexes were obtained by interaction of diisopropyl methylphosphonate with trivalent rare-earth chlorides at 50 °–100 °C. The complexes were characterized by means of infrared, magnetic and X-ray powder diffraction studies. A distorted Oh symmetry is assigned to the metal ions. Far infrared evidence indicates the presence of strong lanthanide (III)-oxygen bonds, possibly having partially covalent character. Possible structures of the new complexes, including monomeric chelates and oligomers or polymers, involving eight-membered phosphonate bridges and four-membered chelate rings, are discussed.

Uranium(IV) and thorium(IV) Tetrakis-(dialkoxyphosphato) and Tetrakis-(alkoxy alkylphosphonato) Polynuclear complexes☆

Abstract Reaction of UCl4and ThCl4 with neutral phosphate and phosphonate esters at elevated temperatures leads to the precipitation of tetrakis-(dialkoxyphosphato) and tetrakis-(alkoxy alkylphosphonato) MIV complexes. Characterization of these complexes by means of spectral, magnetic and X-ray studies led to the assignment of polymeric configurations involving octacoordinated metal ions, to these compounds. Solubility characteristics and magnetic moments, which are low for octacoordinated UIV compounds, are in favor of polynuclear structures. Significant differences in the positions of the νM-Obands of the complexes of various phosphato and phosphonato ligands are suggestive of formation of two types of polymers. The ethyl ethylphosphonato, dimethylphosphato and di-n-butylphosphato complexes were tentatively assigned a cross-linked double-bridged configuration, and the methyl methylphosphonato and isopropyl methylphosponato analogs a structure involving four-membered chelate rings and single phosphonato bridges. The n-butyl n-butyl-phosphonato complexes appear to be mixtures of these two types of polymers.