Reduction of the five-coordinate iron(II) dihalide complexes (iPrPDI)FeX2 (iPrPDI = ((2,6-CHMe2)2C6H3NCMe)2C5H3N; X = Cl, Br) with sodium amalgam under 1 atm of dinitrogen afforded the square pyramidal, high spin iron(0) bis(dinitrogen) complex (iPrPDI)Fe(N2)2. In solution, (iPrPDI)Fe(N2)2 loses 1 equiv of N2 to afford the mono(dinitrogen) adduct (iPrPDI)Fe(N2). Both dinitrogen compounds serve as effective precatalysts for the hydrogenation and hydrosilation of olefins and alkynes. Effecient catalytic reactions are observed with low catalyst loadings (≤0.3 mol %) at ambient temperature in nonpolar media. The catalytic hydrosilations are selective in forming the anti-Markovnikov product. Structural characterization of a high spin iron(0) alkyne and a bis(silane) σ-complex has also been accomplished and in combination with isotopic labeling studies provides insight into the mechanism of both catalytic C−H and catalytic C−Si bond formation.

Preparation and molecular and electronic structures of iron(0) dinitrogen and silane complexes and their application to catalytic hydrogenation and hydrosilation.

The electronic structure of a family of bis(imino)pyridine iron dihalide, monohalide, and neutral ligand compounds has been investigated by spectroscopic and computational methods. The metrical parameters combined with Mossbauer spectroscopic and magnetic data for (iPrPDI)FeCl2 (iPrPDI = 2,6-(2,6-iPr2C6H3NCMe)2C5H3N) established a high-spin ferrous center ligated by a neutral bis(imino)pyridine ligand. Comparing these data to those for the single electron reduction product, (iPrPDI)FeCl, again demonstrated a high-spin ferrous ion, but in this case the SFe = 2 metal center is antiferromagnetically coupled to a ligand-centered radical (SL = 1/2), accounting for the experimentally observed S = 3/2 ground state. Continued reduction to (iPrPDI)FeLn (L = N2, n = 1,2; CO, n = 2; 4-(N,N-dimethylamino)pyridine, n = 1) resulted in a doubly reduced bis(imino)pyridine diradical, preserving the ferrous ion. Both the computational and the experimental data for the N,N-(dimethylamino)pyridine compound demonstrate nearly...

Electronic structure of bis(imino)pyridine iron dichloride, monochloride, and neutral ligand complexes: a combined structural, spectroscopic, and computational study.

The synthesis and characterization of the complexes Mo[N(R)Ar]3 (R = C(CD3)2CH3, Ar = 3,5-C6H3Me2), (μ-N2){Mo[N(R)Ar]3}2, (μ-15N2){Mo[N(R)Ar]3}2, NMo[N(R)Ar]3, 15NMo[N(R)Ar]3, Mo[N(t-Bu)Ph]3, (μ-N2){Mo[N(t-Bu)Ph]3}2, and NMo[N(t-Bu)Ph]3 are described. Temperature-dependent magnetic susceptibility data indicate a quartet ground state for Mo[N(R)Ar]3. Single-crystal X-ray diffraction studies for Mo[N(R)Ar]3 and NMo[N(t-Bu)Ph]3 are described. Extended X-ray absorption fine structure (EXAFS) structural studies for Mo[N(R)Ar]3, (μ-N2){Mo[N(R)Ar]3}2, and NMo[N(R)Ar]3 are reported. Temperature-dependent kinetic data are given for the unimolecular fragmentation of (μ-N2){Mo[N(R)Ar]3}2 to 2 equiv of NMo[N(R)Ar]3 and for the fragmentation of (μ-15N2){Mo[N(R)Ar]3}2 to 2 equiv of 15NMo[N(R)Ar]3. The temperature dependence of the 15N2 isotope effect for the latter N2 cleavage process was fitted to a simple harmonic model, leading to a prediction for the difference in NN stretching frequencies for the two isotopomers. ...

Dinitrogen cleavage by three-coordinate molybdenum(III) complexes: Mechanistic and structural data

The pursuit of single-molecule magnets (SMMs) with better performance urges new molecular design that can endow SMMs larger magnetic anisotropy. Here we report that two-coordinate cobalt imido complexes featuring highly covalent Co═N cores exhibit slow relaxation of magnetization under zero direct-current field with a high effective relaxation barrier up to 413 cm-1, a new record for transition metal based SMMs. Two theoretical models were carried out to investigate the anisotropy of these complexes: single-ion model and Co-N coupling model. The former indicates that the pseudo linear ligand field helps to preserve the first-order orbital momentum, while the latter suggests that the strong ferromagnetic interaction between Co and N makes the [CoN]+ fragment a pseudo single paramagnetic ion, and that the excellent performance of these cobalt imido SMMs is attributed to the inherent large magnetic anisotropy of the [CoN]+ core with |MJ = ± 7/2⟩ ground Kramers doublet.

Two-Coordinate Co(II) Imido Complexes as Outstanding Single-Molecule Magnets

Entry into “[PhBP3]Fe” chemistry affords a rare, pseudotetrahedral iron(I) complex, [PhBP3]Fe(PPh3), with an S = 3/2 ground state. This precursor undergoes rapid oxidation by aryl azide to produce the d5 imide [PhBP3]Fe⋮NAr (Ar = p-tolyl). The Fe(III) imide is significant in that it is low-spin and represents the first mononuclear imide of iron. Doublet [PhBP3]Fe⋮NAr reacts rapidly and quantitatively with CO at room temperature to release isocyanate and [PhBP3]Fe(CO)2. The [PhBP3]Fe(CO)2 byproduct is also a precursor to [PhBP3]Fe⋮NAr upon addition of aryl azide.

A Low-Spin d5 Iron Imide: Nitrene Capture by Low-Coordinate Iron(I) Provides the 4-Coordinate Fe(III) Complex [PhB(CH2PPh2)3]Fe⋮N-p-tolyl

Measurement of magnetic susceptibility and magnetic moment of paramagnetic molecules in solution by high-field Fourier transform NMR spectroscopy

Chemistry of thienopyridines. XXXVII. Syntheses in the cyclopenta, cyclohexa-, and cycloheptathieno[2,3-b]pyridine series. Three analogs of 9-amino-1,2,3,4-tetrahydroacridine†

Chemistry of Peri‐condensed pyrroles. Synthesis of 4H‐naphtho[1,4‐def]carbazole. A new route to nitrotriphenylenes

Crystals of the olivine minerals, tephroite (Mn2SiO4) and fayalite (Fe2SiO4) containing manganese(II) and iron (II and trace of III), respectively, were synthesized. Glasses were prepared from these crystalline materials by a splat-quench technique. Measurement of electron paramagnetic resonance (EPR) of all these powdered samples at room temperature show that the g-factors of Mn2+ in both glassy and crystalline environments (geff = 2.004) are the same, although the EPR linewidths (for glass, ΔHpp = 200 G; for crystals ΔHpp = 287 G) suggest less clustering of paramagnetic Mn2+ ions in the glass. Mn2+ probably occupies a distorted octahedral site in the tephroite crystal structure, although a four-fold coordination is suggested from other spectroscopic investigation on this glass. The EPR parameters of Fe3+ in synthetic fayalite glass (geff = 2.01 and 6.00; ΔHpp=150 and 1375 G, respectively, for the high and low field resonances) and powdered crystals (geff = 3.31 and ΔHpp = 900 G) indicated that Fe3+ ion in the crystals, is probably located in a distorted tetragonal site M2 and an axial environment has been proposed in the glassy system.

Sandip K. Sur

Papers

Measurement of magnetic susceptibility and magnetic moment of paramagnetic molecules in solution by high-field Fourier transform NMR spectroscopy

Chemistry of thienopyridines. XXXVII. Syntheses in the cyclopenta, cyclohexa-, and cycloheptathieno[2,3-b]pyridine series. Three analogs of 9-amino-1,2,3,4-tetrahydroacridine†

Chemistry of Peri‐condensed pyrroles. Synthesis of 4H‐naphtho[1,4‐def]carbazole. A new route to nitrotriphenylenes

Electron paramagnetic resonance study of iron(III) and manganese(II) in the glassy and crystalline environments of synthetic fayalite and tephroite

Chemistry of thienopyridines. XXXVIII. Diels‐Alder reactions of thienopyridine sulfones. Part 2