R. M. Golding

Manganese(IV) dithiocarbamato complexes

Several new cationic dithiocarbamato complexes of the type [Mn(dtc)3] X (where dtc refers to the dithiocarbamate ligand and X to the non-coordinating anions, perchlorate and tetrafluoroborate) have been prepared by the reaction of manganous perchlorate and manganous tetrafluoroborate with the appropriate N,N-disubstituted dithiocarbamates. Conductivity, infrared, esr, magnetic susceptibility and a complete structure determination on one of the compounds support a manganese(1V) formulation for the complexes.

Single Crystal ESR Study of Mn2+ in Natural Tremolite

The room temperature 9.5 GHz ESR spectrum of a natural tremolite single crystal containing 0.15% Mn2+ is analysed using both perturbation and numerical solutions to the experimental Hamiltonian. The analysis is in three parts: (i) allowed, Δ MS=± 1, Δ MI=0 transitions, (ii) forbidden, Δ MS=± 1, Δ MI>0 transitions, and (iii) forbidden, | Δ MS | > 1 transitions. Mn2+ occupies only a single site in the tremolite structure.

NMR Studies of a Series of Phenyl Substituted Ferric N‐Ethyl‐N‐Phenyldithiocarbamates

The proton NMR results of a series of phenyl substituted tris(N‐ethyl‐N‐phenyldithiocarbamato)‐iron(III) complexes have been successfully interpreted assuming the iron atom is in an intermediate crystal field of octahedral symmetry. The substituent in the phenyl ring has very little effect on the energy separation of the 6A1 and 2T2 electronic states. However, the substituent substantially influences the methylene proton isotropic hyperfine interaction constants in the 6A1 state. These results have been interpreted as arising from changes in the π character of the N‐phenyl bond due to the degree of hindered rotation with the aromatic substitution.

ESR Studies of Some Manganese(III) Dithiocarbamates Diluted in Cobalt Analogs

Electron spin resonance results at 77°K are presented for a series of manganese(III) dithiocarbamates diluted in the cobalt(III) analogs using both single crystal and powder techniques. The observed spectra are shown to arise only from the addition of manganic dithiocarbamates to the cobalt salt. No fine or hyperfine structure was observed and the paramagnetic species seems unlikely to be due simply to a d4 Mn3+ ion.

N.M.R. studies of some chromium(III) dithiocarbamate complexes

The temperature dependence of the proton N.M.R. spectra of some simple tris(N,N-disubstituted dithiocarbamato)chromium(111) derivatives, [Cr(S2CNR2)3], has been studied in deuterochloroform solution over the range ? 60o to + 60oC. In these spectra, which are very broad, the N-CHn protons in certain cases exhibit a double peak unlike the iron(111) or manganese(111) complexes-probably a consequence of high energy barriers between the Δ and Δ enantiomers, the broadness of the spectra being ascribed to the lack of an appropriate relaxation mechanism. The spectra of a number of further iron(111) and manganese(111) derivatives are reported and the hyperfine coupling constants in the three series of complexes compared.

Temperature dependence of the magnetic moment for d4 ions in an intermediate crystal field of octahedral symmetry

A general expression for the temperature dependence of the effective magnetic moment of d4ions in an intermediate crystal field of octahedral symmetry is derived when the 5E state and the lowest lying 3T1 state have comparable energies. The magnetic susceptibility results for two series of manganic compounds are discussed.

Magnetic susceptibilities and mössbauer spectra of some fluorinated monothio-β-diketonato complexes of iron(III)

SummaryThe magnetic moments of the iron(III) chelates of the fluorinated monothio-β-diketones RC(SH)=CFICOCF3 (R = 2-thienyl, β-naphthyl, Ph, p-McC6H4, p-FC6H4,p-ClC6H4, m-MeC6H4, m-CIC6H4 m-BrC6H4) have been measured over a temperature range. The moments vary from 5.49 to 2.16 B.M. at room temperature and are temperaturedependent, falling to as low as 1.82 B.M. at 83 K. The quadrupole splittings from the Messbauer spectra at room temperature are within the range 0.70 to 1.80 mm/s, whereas at 77 K they lie within the range 1.70 to 1.95 mm/s. These results indicate that the iron atom is in an intermediate effective crystal field, which depends to a small extent on the temperature and the substituent R and increases in the order: C4H3S < β-C10 < p-XC6H4 < Ph < m-XC6H4 (X = Me, F, CI or Br). Also the results indicate the degree of bonding asymmetry of the iron atom.

Salts of the tris(isonitrosomalonamido)ferrate(II) ion : crystal structures and anomalous magnetism of the potassium and caesium salts of the tris(isonitrosomalonamido)ferrate(II) anion

Complexes of the type M[FeL3]·xH2O [M+=alkali-metal cation, L–= NH2·COC(NO)-·CO·NH2] have been prepared. The sodium and rubidium salts are diamagnetic; the potassium and caesium salts are paramagnetic, their room temperature magnetic moments being 2.1 6 and 2.66 B.M. respectively with only a slight temperature dependence. Mossbauer spectra are indicative of the presence of both singlet and quintet states.The crystal structure of the potassium salt, K[FeL3]·2H2O, has been determined from diffractometer data and refined by least squares to R 0.040 for 3 981 observed reflections. Crystals are monoclinic, space group C2/c, a= 29.89(1), b= 9.780(2), c= 13.980(3)A, β= 106.68(2)°,Z= 8. The cell contents comprise infinite zig-zag chains of K+ cations and [FeL3]– anions, the ligands co-ordinating through one of the amide oxygens and the nitrosyl nitrogen in a fac-configuration, interspersed by potassium cations, the co-ordination sphere of the latter being the three nitrosyl oxygens from one anion, and the three remaining amide oxygens from the next; the chains are parallel to c; mean distances: Fe–N 1.882, Fe–O 1.972A.The crystal structure of Cs[FeL3]·2H2O has also been determined byX-ray diffraction and refined by least squares to R 0.12 for 5 126 observed reflections. Crystals are monoclinic, space group Aa, a= 33.312(6), b= 24.792(5), c= 13.323(2)A, β= 91.55(1)°. Z= 20 (for Cs[FeL3]). As with K[FeL3]·2H2O, the cell contents comprise parallel independent chains of [FeL3]–anions alternating with Cs cations, the chains being almost linear in this case; one of the chains is interrupted by a region of considerable disorder which adversely affects the accuracy of determination of the metal-atom geometries. Neither structure determination is helpful in understanding the anomalous magnetism of these two complexes.