First-principles estimates of equilibrium magnesium isotope fractionation in silicate, oxide, carbonate and hexaaquamagnesium(2+) crystals

Four-membered pnictogen-nitrogen heterocycles of the type [XE(m-NR)]2 (E = element of Group 15, X = halogen) are known as 1,3-dihalogeno-cyclo-1,3-dipnicta(III)-2,4-diazanes (Scheme 1, species A). The phosphorus species in particular play a major role in preparative phosphorus–nitrogen chemistry, for example in the preparation of macrocycles, polymers, main-group complexes, and ring transformation reactions or the generation of cyclic binary PN cations. In recent years, new examples for cyclo-1,3-dipnicta(III)-2,4diazanes were prepared by introduction of bulky R substituents and characterized, with the focus on kinetic stabilization. Only recently, the synthesis of salts bearing the highly reactive cyclo-1,3-dipnicta(III)-2,4-diazenium cations [ClE(mNTer)2E] + (E = P and As; Ter = terphenyl = 2,6-bis(2,4,6trimethylphenyl)phenyl; Scheme 1, species B) was reported. The generation of such cations was achieved by halide abstraction upon addition of strong Lewis acids, such as GaCl3. [9] Utilization of the bulky terphenyl group leads to the formation of separated ion pairs in the crystal with large interionic distances.

Cyclic distiba- and dibismadiazenium cations.

Data on the known-to-date copper(II) complexes with neutral nitrogen-containing ligands (2,2'-bipyridyl, 1,10-phenanthroline, 2,2'-bipyridylamine, aminoguanidine, ammonia, pyridine derivatives, etc.) with boron cluster anions, including those containing bridging OH– and $${\text{CO}}_{3}^{{2 - }}$$ groups, are generalized. Mono-, di-, tri-, tetranuclear, and polymer copper(II) complexes are considered; the geometry of copper(II) coordination polyhedra, structural features of complex compounds, and methods for their preparation are discussed. The boron cluster anions [B10H10]2–, [B12H12]2–, [B10Cl10]2–, [B20H18]2– and their derivatives (substituted derivatives, carboranes, and metallacarboranes) have been chosen as counterions.

Structural Diversity of Cationic Copper(II) Complexes with Neutral Nitrogen-Containing Organic Ligands in Compounds with Boron Cluster Anions and Their Derivatives (Review)

Four mononuclear cobalt(II) complexes with pseudo tetrahedral geometry were isolated with different counteranions; their structure solution reveals the molecular formula as [Co(L1)4]X2 [where L1 = thiourea (NH2CSNH2) and X = NO3 (1), Br (2), and I (3)] and [Co(L1)4](SiF6) (4). The detailed analysis of direct-current (dc) magnetic data reveals a zero-field splitting (ZFS; D) with mS = ±3/2 as the ground levels (D < 0) for the four complexes. The magnitude of the ZFS parameter is larger, in absolute value, for 1 (D = -61.7 cm-1) than the other three complexes (-5.4, -5.1, and -12.2 cm-1 for 2-4, respectively). The sign of D for 1, 2, and 4 was unambiguously determined by X-band electron paramagnetic resonance (EPR) spectroscopy of the diluted samples (10%) at 5 K. For 3, the sign of D was naturally endorsed from the frequency-dependent out-of-phase signal (χM″) observed in the absence of an external dc magnetic field and confirmed by high-frequency EPR (70-600 GHz) experiments performed on a representative pure polycrystalline 3, which gave a quantitative D value of -5.10(7) cm-1. Further, the drastic changes in the spin Hamiltonian parameters and their related relaxation dynamics phenomena (of 2-4 compared to 1) were rationalized using ab initio complete-active-space self-consistent field/n-electron valence perturbation theory calculations. Calculations disclose that the anion-induced structural distortion observed in 2-4 leads to a nonfavorable overlap between the π orbital of cobalt(II) and the π* orbital of the sulfur atom that reduces the overall |D| value in these complexes compared to 1. The present study demonstrates that not only the first but also the second coordination sphere significantly influences the magnitude of the ZFS parameters. Particularly, a reduction of D of up to ∼90% occurs (in 2-4 compared to 1) upon a simple variation of the counteranions and offers a viable approach to modulate ZFS in transition-metal-containing single-molecule magnets.

Influence of a Counteranion on the Zero-Field Splitting of Tetrahedral Cobalt(II) Thiourea Complexes.

Cyclische Distiba‐ und Dibismadiazenium‐Kationen

A novel complex, tris(ɛ-caprolactamium) hexa(isothiocyanato)chromate(III) tricaprolactam (C6H12NO)3[Cr(NCS)6] · 3(C6H11NO), has been synthesized and characterized by X-ray diffraction. The structure can be referred to the discrete ionic type. The coordination polyhedron of the chromium atom is a nearly regular octahedron. The crystals of the complex (C42H69CrN12O6S6, FW = 1082.45) are triclinic, space group P$\overline 1 $, Z = 1, V = 1359.3(2) A3, dcalcd = 1.322 g/cm3. Unit cell parameters: a = 11.1784(9) A, b = 11.3196(7) A, c = 12.580(2) A, α = 109.347(5)°, β = 106.304(5)°, γ = 102.025(4)°. The unit cell contains three caprolactamium cations and three caprolactam molecules related by the inversion center of the space group, which leads to random occupancy of the positions of the cations and solvation molecules.

Synthesis and crystal structure of tris(ɛ-caprolactamium) hexa(isothiocyanato)chromate(III) tricaprolactam (C6H14NO)3[Cr(NCS)6] · 3(C6H13NO)

Thermal decomposition of the complexes [LnL8][Cr(NCS)6] (Ln = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+; L = ɛ-C6H11NO) in air and in inert atmosphere was studied by thermogravimetry, X-ray phase analysis, IR spectroscopy, and mass spectrometry. The compositions of gaseous and solid thermolysis products were established. A reversible thermochromic effect was found on heating to 200–210°C.

Thermal analysis of rare-earth metal(III) hexa(isothiocyanato)chromate(III) complexes with ɛ-caprolactam

Adducts of bismuth(III) salts with dimethyl sulphoxide and dimethylformamide

New double complexes [Co(DMSO)6][SiF6] ⋅ 2H2O (I) and [Co(DMF)3(H2O)3][SiF6] ⋅ DMF (II) have been synthesized and studied by IR spectroscopy and X-ray diffraction. Crystals of complex I belong to the tetragonal symmetry system, space group R3, Z = 3, a = 11.8232(3) A, c = 18.4699(5) A, V = 2235.97(10) A3, ρcalc = 1.573 g/cm3. Crystals of complex II are triclinic, space group P1, Z = 2, a = 8.6264(4) A, b = 10.1419(4) A, c = 13.9657(6) A, α = 100.847(2)°, β = 98.549(2)°, γ = 93.479(2)°, V = 1181.71(9) A3, ρcalc = 1.539 g/cm3.

Hexafluorosilicates of cobalt(II) complexes with dimethylsulfoxide and dimethylformamide

A new complex [{Cd(ɛ-Cpl)5}2Cr(NCS)6][Cd(ɛ-Cpl)4Cr(NCS)6] was synthesized, and its crystal structure was solved. The complex was studied by chemical analysis and IR spectroscopy.

E. S. Tatarinova

Papers

Synthesis and crystal structure of tris(ɛ-caprolactamium) hexa(isothiocyanato)chromate(III) tricaprolactam (C6H14NO)3[Cr(NCS)6] · 3(C6H13NO)

Thermal analysis of rare-earth metal(III) hexa(isothiocyanato)chromate(III) complexes with ɛ-caprolactam

Adducts of bismuth(III) salts with dimethyl sulphoxide and dimethylformamide

Hexafluorosilicates of cobalt(II) complexes with dimethylsulfoxide and dimethylformamide

Synthesis and physicochemical properties of [{Cd(ɛ-C6H11NO)5}2Cr(NCS)6][Cd(ɛ-C6H11NO)4Cr(NCS)6]