Nikolay A. Pushkarevsky

[{(η5-C5Me5)2Sm}4P8]: A Molecular Polyphosphide of the Rare-Earth Elements

[{(eta(5)-C(5)Me(5))(2)Sm}(4)P(8)], a molecular polyphosphide of the rare-earth elements having a realgar core structure, was synthesized by a one-electron redox reaction of divalent samarocen and white phosphorus.

Mixed‐Metal Lanthanide–Iron Triple‐Decker Complexes with a cyclo‐P5 Building Block

Tripleand multidecker sandwich complexes have been discussed in the last decades for their unique electrical and magnetic properties. The organic spacer between the metals may facilitate intermetallic electronic communication, which has a high potential for molecular electronics. A number of one-dimensional organometallic sandwich molecular wires (SMWs) have been extensively studied. Thus, the multilayer vanadium–arene (Ar) organometallic complexes [Vn(Ar)m], which can be produced in a molecular beam by laser vaporization, are a class of one-dimensional molecular magnets. Ferrocene-based molecular wires have been synthesized in the gas phase and characterized by mass spectroscopy. It was calculated that these compounds have half-metallic properties with 100 % negative spin polarization near the Fermi level in the ground state. In contrast to this investigation in the gas phase, studies on related organometallic tripleand multidecker sandwich complexes containing f-block elements (lanthanides or actinides) in condensed phase remain rare; studies were mostly on the cyclooctatetraene ligand and its derivatives. The only rare-earth-element triple-decker complex with heterocycles is the low-valent scandium 1,3,5-triphosphabenzene complex [{(hP3C2tBu2)Sc}2(m-h 6 :h-P3C3tBu3)], which was obtained by cocondensation of scandium vaporized in an electron beam with an excess of the phosphaalkyne tBuC P. Apart from organometallic compounds, tripleand multidecker sandwich complexes of the 4f elements consisting of “salen” type Schiff base ligands, phthalocyanines, and porphyrins have been extensively studied because these compounds exhibit tunable spectroscopic, electronic, and redox properties, and different extents of intramolecular p–p interactions. Despite these promising physical properties further investigations on 4f elements based tripleand multidecker sandwich complexes are obviously hampered by the limited variety of ligands that have been attached to the metal centers to date. Based on these considerations, we present herein mixed d/f-block-metal triple-decker complexes with a purely inorganic all-phosphorus middle deck. In contrast to d-block chemistry, where purely inorganic ring systems of Group 15 elements such as P5 and P6, [9] As5, [9c] and Sb5 [10] are well-established, there is no analogy with the fblock elements to date. On the other hand, it was shown only recently that rare-earth elements can stabilize highly reactive main-group species such as N2 3 . Although some heavier Group 15–lanthanide compounds, such as phosphides (Ln PR2), [12] arsenides (Ln AsR2), 13] stibides (Ln Sb3), and bismutides (Ln Bi Bi Ln) are known, the first molecular polyphosphide of the rare-earth elements, [(Cp*2Sm)4P8] (Cp* = h-C5Me5), was recently synthesized. [16] The structure of the complex is very rare and can be described as a realgartype P8 4 ligand trapped in a cage of four samarocenes. As no triple-decker sandwich complex of the rare-earth elements with a polyphosphide middle-deck bridging the metal centers is known, we focused our interest on the cyclo-P5 ligand. The structure and properties of this ligand are very similar to the well-known cyclopentadienyl anion (Scheme 1) and could therefore have many possible coordination modes.

Heterospin π-Heterocyclic Radical-Anion Salt: Synthesis, Structure, and Magnetic Properties of Decamethylchromocenium [1,2,5]Thiadiazolo[3,4-c][1,2,5]thiadiazolidyl

Decamethylchromocene, Cr(II)(eta(5)-C(5)(CH(3))(5))(2) (2), readily reduced [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) in a tetrahydrofuran solvent at ambient temperature with the formation of radical-anion salt [2](+)[1](-) (3) isolated in 97% yield. The heterospin salt 3 ([2](+), S = 3/2; [1](-), S = 1/2) was characterized by single-crystal X-ray diffraction as well as magnetic susceptibility measurements in the temperature range 2-300 K. The experimental data together with theoretical analysis of the salts magnetic structure within the CASSCF and spin-unrestricted broken-symmetry (BS) density functional theory (DFT) approaches revealed antiferromagnetic (AF) interactions in the crystalline 3: significant between anions [1](-), weak between cations [2](+), and very weak between [1](-) and [2](+). Experimental temperature dependences of the magnetic susceptibility and the effective magnetic moment of 3 were very well reproduced in the assumption of the AF-coupled [1](-)...[1](-) (J(1) = -40 +/- 9 cm(-1)) and [2](+)...[2](+) (J(2) = -0.58 +/- 0.03 cm(-1)) pairs. The experimental J(1) value is in reasonable agreement with the value calculated using BS UB3LYP/6-31+G(d) (-61 cm(-1)) and CASSCF(10,10)/6-31+G(d) (-15.3 cm(-1)) approaches. The experimental J(2) value is also in agreement with that calculated using the BS DFT approach (-0.33 cm(-1)).

Bis(toluene)chromium(I) [1,2,5]Thiadiazolo[3,4-c][1,2,5]thiadiazolidyl and [1,2,5]Thiadiazolo[3,4-b]pyrazinidyl: New Heterospin (S1 = S2 = 1/2) Radical-Ion Salts

Bis(toluene)chromium(0), Cr(0)(η(6)-C7H8)2 (3), readily reduced [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) and [1,2,5]thiadiazolo[3,4-b]pyrazine (2) in a tetrahydrofuran solvent with the formation of heterospin, S1 = S2 = ½, radical-ion salts [3](+)[1](-) (4) and [3](+)[2](-) (5) isolated in high yields. The salts 4 and 5 were characterized by single-crystal X-ray diffraction (XRD), solution and solid-state electron paramagnetic resonance, and magnetic susceptibility measurements in the temperature range 2-300 K. Despite the formal similarity of the salts, their crystal structures were very different and, in contrast to 4, in 5 anions were disordered. For the XRD structures of the salts, parameters of the Heisenberg spin Hamiltonian were calculated using the CASSCF/NEVPT2 and broken-symmetry density functional theory approaches, and the complex magnetic motifs featuring the dominance of antiferromagnetic (AF) interactions were revealed. The experimental χT temperature dependences of the salts were simulated using the Van Vleck formula and a diagonalization of the matrix of the Heisenberg spin Hamiltonian for the clusters of 12 paramagnetic species with periodic boundary conditions. According to the calculations and χT temperature dependence simulation, a simplified magnetic model can be suggested for the salt 4 with AF interactions between the anions ([1](-)···[1](-), J1 = -5.77 cm(-1)) and anions and cations ([1](-)···[3](+), J2 = -0.84 cm(-1)). The magnetic structure of the salt 5 is much more complex and can be characterized by AF interactions between the anions, [2](-)···[2](-), and by both AF and ferromagnetic (FM) interactions between the anions and cations, [2](-)···[3](+). The contribution from FM interactions to the magnetic properties of the salt 5 is in qualitative agreement with the positive value of the Weiss constant Θ (0.4 K), whereas for salt 4, the constant is negative (-7.1 K).

Hunting for the Magnesium(I) Species: Formation, Structure, and Reactivity of some Donor‐Free Grignard Compounds

Magnesium bromide radicals have to be prepared as high-temperature molecules and trapped as a metastable solution because a seemingly simple reduction of donor-free Grignard compounds failed. However, the essential role of magnesium(I) species during the formation of Grignard compounds could be demonstrated experimentally.

Synthesis and properties of the heterospin (S1 = S2 = 1/2) radical-ion salt bis(mesitylene)molybdenum(I) [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl

Low-temperature interaction of [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) with MoMes2 (Mes = mesitylene/1,3,5-trimethylbenzene) in tetrahydrofuran gave the heterospin (S1 = S2 = (1)/2) radical-ion salt [MoMes2](+)[1](-) (2) whose structure was confirmed by single-crystal X-ray diffraction (XRD). The structure revealed alternating layers of the cations and anions with the Mes ligands perpendicular, and the anions tilted by 45°, to the layer plane. At 300 K the effective magnetic moment of 2 is equal to 2.40 μB (theoretically expected 2.45 μB) and monotonically decreases with lowering of the temperature. In the temperature range 2-300 K, the molar magnetic susceptibility of 2 is well-described by the Curie-Weiss law with parameters C and θ equal to 0.78 cm(3) K mol(-1) and -31.2 K, respectively. Overall, the magnetic behavior of 2 is similar to that of [CrTol2](+)[1](-) and [CrCp*2](+)[1](-), i.e., changing the cation [MAr2](+) 3d atom M = Cr (Z = 24) with weak spin-orbit coupling (SOC) to a 4d atom M = Mo (Z = 42) with stronger SOC does not affect macroscopic magnetic properties of the salts. For the XRD structure of salt 2, parameters of the Heisenberg spin-Hamiltonian were calculated using the broken-symmetry DFT and CASSCF approaches, and the complex 3D magnetic structure with both the ferromagnetic (FM) and antiferromagnetic (AF) exchange interactions was revealed with the latter as dominating. Salt 2 is thermally unstable and slowly loses the Mes ligands upon storage at ambient temperature. Under the same reaction conditions, interaction of 1 with MoTol2 (Tol = toluene) proceeded with partial loss of the Tol ligands to afford diamagnetic product.

Synthesis and structure of new homo-and heteroligand carbonyl cluster complexes with [Fe3(μ3-Q)(μ3-X)] core (Q = Se, Te; X = S, As)

New cluster complexes of iron [Fe3Q(AsCp*)(CO)9] (Q = Se, Te, Cp* = C5(CH3)5) are synthesized with the square pyramidal cluster core Fe3QAs. A suitable procedure of the synthesis of known heterochalcogenide [Fe3QS(CO)9] clusters is developed. Monosubstituted [Fe3Q(AsCH3)(CO)8(PPh3)] and disubstituted [Fe3Q(AsCH3)(CO)7(PPh3)2] clusters formed in the reactions of [Fe3Q(AsCH3)(CO)9] with PPh3 are studied. In monosubstituted clusters, the phosphine ligand is coordinated in the axial position to the Fe atom in the base of the Fe3QAs square pyramid, while in disubstituted clusters, both phosphine ligands coordinate the Fe atoms in the pyramid base, one ligand being in the axial and another one in the equatorial position. The NMR data support the possibility of migration of the Fe-Fe bonds in a triangle in the cluster core in the case of disubstituted clusters.

Nature of Bonding in Donor–Acceptor Interactions Exemplified by Complexes of N‐Heterocyclic Carbenes with 1,2,5‐Telluradiazoles

Comprehensive structural, spectroscopic, and quantum chemical analyses of new donor-acceptor complexes between N-heterocyclic carbenes and 1,2,5-telluradiazoles and a comparison with previously known complexes involving tellurenyl cations showed that the dative C-Te bonds cannot be solitarily described with only one Lewis formula. Canonical Lewis formulas that denote covalency and arrows emphasizing ionicity complement each other in varying extents. Evaluation of the relative weights of these resonance forms requires proper bonding description with a well-balanced toolbox of analytical methods. If for conciseness only, one resonance form is used, it must be the most significant one according to the analytical evaluation. If unclear, all significant resonance forms should be displayed.

Chalcogen arsenide clusters of iron with a functional carboxyl group: Synthesis, structures, and thermolysis

The carbonyl clusters [Fe3(μ3-Q)(μ3-AsR)(CO)9] (Q = Se and Te; R = meta- and para-HOOCC6H4) were obtained from the salts K2[Fe3(μ3-Q)(CO)9] and organoarsenic diiodides RAsI2 prepared by reducing iodination of arsonic acids RAsO(OH)2 according to a novel method. The structures of the clusters were identified by X-ray diffraction. The crystal packing motifs of the dimers of the cluster molecules and their relationship with the solubility of the clusters are discussed. The sequential steps of the thermolysis (decarbonylation, decarboxylation, and decomposition of the organic fragment) of the clusters were studied. The presence and location of the carboxyl group does not influence the decarbonylation temperature.

Dimerization of pentanuclear clusters [Fe3Q(AsMe)(CO)9] (Q = Se, Te) as a conversion pathway to novel cubane-like aggregates

The first examples of carbonyl heterocubane-type clusters, [Fe(4)(μ(3)-Q)(2)(μ(3)-AsMe)(2)(CO)(12)] (2, Q = Se (a), Te (b)), which simultaneously contain elements of group 15 and 16, were obtained by thermolysis of [Fe(3)(μ(3)-Q)(μ(3)-AsMe)(CO)(9)] (1) in acetonitrile. The clusters 2 possess a cubic Fe(4)Q(2)As(2) core with alternating Fe and Q/As atoms. The coordination environment of the Fe atoms is close to octahedral, and those of Q or As atoms are tetrahedral, which determines the distorted cubic cluster core geometry. The second main products of thermolysis are the clusters [Fe(6)(μ(3)-Q)(μ(4)-Q)(μ(4)-AsMe)(2)(CO)(12)] (3a,b), whose core contains double the elemental composition of the initial cluster 1. In the case of the Se-containing cluster two other minor products [Fe(4)(μ(4)-Se)(μ(4)-SeAsMe)(CO)(12)] (4) and [Fe(3)(μ(3)-AsMe)(2)(CO)(9)] (5) are formed. Based on the structures and properties of the products, a reaction route for the conversion of 1 into 2 is proposed, which includes the associative formation of the clusters 3 as intermediates, unlike the dissociative pathways previously known for the transformations of similar clusters of the type [Fe(3)Q(2)(CO)(9)].