Transformation and structural discrimination between the neutral {Fe(NO)2}10 dinitrosyliron complexes (DNICs) and the anionic/cationic {Fe(NO)2}9 DNICs

Reaction of Fe(CO)2(NO)2 and sparteine/tetramethylethylenediamine (TMEDA) in tetrahydrofuran afforded the electron paramagnetic resonance (EPR)-silent, neutral {Fe(NO)2}10 dinitrosyliron complexes (DNICs) [(sparteine)Fe(NO)2] (1) and [(TMEDA)Fe(NO)2] (2), respectively. The stable and isolable anionic {Fe(NO)2}9 DNIC [(S(CH2)3S)Fe(NO)2]- (4), with a bidentate alkylthiolate coordinated to a {Fe(NO)(2)} motif, was prepared by the reaction of [S(CH2)3S]2- and the cationic {Fe(NO)2}9 [(sparteine)Fe(NO)2]+ (3) obtained from the reaction of complex 1 and [NO][BF4] in CH(3)CN. Transformation from the neutral complex 1 to the anionic complex 4 was verified via the cationic complex 3. Here complex 3 acts as an {Fe(NO)2}-donor reagent in the presence of thiolates. The EPR spectra of complexes 3 and 4 exhibit an isotropic signal with g = 2.032 and 2.031 at 298 K, respectively, the characteristic g value of {Fe(NO)2}9 DNICs. On the basis of N-O/Fe-N(O) bond lengths of the single-crystal X-ray structures of the {Fe(NO)2}9/{Fe(NO)2}10 DNICs, the oxidation level of the {Fe(NO)2} core of DNICs can be unambiguously assigned. The mean N-O distances falling in the range of 1.214(6)-1.189(4) A and the Fe-N(O) bond distances in the range of 1.650(7)-1.638(3) A are assigned as the neutral {Fe(NO)(2)}(10) DNICs. In contrast, the mean N-O bond distances ranging from 1.178(3) to 1.160(6) A and the mean Fe-N(O) bond distances ranging from 1.695(3) to 1.661(4) A are assigned as the anionic/neutral/cationic {Fe(NO)2}9 DNICs. In addition, an EPR spectrum in combination with the IR nu(NO) (the relative position of the nu(NO) stretching frequencies and their difference Deltanu(NO)) spectrum may serve as an efficient tool for discrimination of the existence of the anionic/cationic/neutral {Fe(NO)2}9 DNICs and the neutral {Fe(NO)2}10 DNICs.     

Structural characterization of [Fe(NO)(mnt)2] salts

The iron dithiolene compounds [Fe₂(mnt)₄]²⁻ [1]²⁻ and [Fe(NO)(mnt)₂]ⁿ (n = 1−, [2]¹⁻; n = 2−, [2]²⁻) ([mnt]²⁻ = maleonitriledithiolate = [(NC)₂C₂S₂]²⁻) have been characterized structurally by X-ray diffraction as their [Et₄N]⁺ salts at 100 K. Dianion [2]²⁻ is prepared from [2]¹⁻ by reduction with Na[Et₃BH] and is observed to have a bent Fe-NO angle at 149.9(5)° in contrast to the linear configuration of Fe-NO in [2]¹⁻ (180.0°). The change from linear to bent binding mode for NO, an increase of more than 0.1 Å in the Fe-N bond length, and the relative invariance of the Fe-S distances for [2]²⁻ versus [2]¹⁻ indicate that the NO ligand is the site of reduction. The [Et₃NH]⁺ complex of [2]¹⁻ was also identified by crystallography and found to have hydrogen bonding contacts between [Et₃NH]⁺ and the cyano nitrogen atom of an [mnt]²⁻ ligand. Furthermore, relatively close S?S contacts (3.602-3.615 Å) occur between [2]¹⁻ anions, which pack together in an offset, head-to-head fashion. These S?S contacts are absent in the structure of [Et₄N][2]. Infrared spectra show an energy decrease for, and a significant broadening of, the NO bond stretching absorption peak in [2]²⁻, which is consistent with a bent NO ligand sampling a range of conformations both by facile pivoting about the Fe-N axis and by a breathing of the Fe-NO angle.     

Transformation of the {Fe(NO)2}9 dinitrosyl iron complexes (DNICs) into S-nitrosothiols (RSNOs) triggered by acid-base pairs

S‐Nitrosation of the coordinated thiolate of dinitrosyl iron complexes (DNICs) to generate S‐nitrosothiols (RSNOs) was demonstrated. Transformation of [{(NO)₂Fe(μ‐StBu)}₂] ( 1‐tBuS ) into the {Fe(NO)₂}⁹ DNIC [(NO)₂Fe(StBu)(MeIm)] ( 2‐MeIm ) occurs under addition of 20 equiv of 1‐methylimidazole (MeIm) into a solution of 1‐tBuS in THF. The dynamic interconversion between {Fe(NO)₂}⁹ [(NO)₂Fe(S‐NAP)(dmso)] ( 2‐dmso ) (NAP=N‐acetyl‐D ‐penicillamine) and [{(NO)₂Fe(μ‐S‐NAP)}₂] ( 1‐NAP ) was also observed in a solution of complex 1‐NAP in DMSO. In contrast to the reaction of complex 2‐MeIm and bis(dimethylthiocarbamoyl) disulfide ((DTC)₂) to yield {Fe(NO)}⁷ [(NO)Fe(DTC)₂] ( 3 ) (DTC=S₂CNMe₂) accompanied by (tBuS)₂ and NO_(g), transformation of {Fe(NO)₂}⁹ 2‐MeIm ( 2‐dmso ) into RSNOs (RS=tBuS, NAP‐S) along with complex 3 induced by the Brønsted acid solution of (DTC)₂ demonstrated that Brønsted acid may play a critical role in triggering S‐nitrosation of the coordinated thiolate of DNICs 2‐MeIm (or 2‐dmso ) to produce RSNOs. That is, DNIC‐mediated S‐nitrosation requires a Brønsted acid–Lewis base pair to produce RSNO. Transformation of DNICs into RSNOs may only occur on the one‐thiolate‐containing {Fe(NO)₂}⁹ DNICs, in contrast to protonation of the two‐thiolate‐containing DNICs [(NO)₂Fe(SR)₂]^? by Brønsted acid to yield [{(NO)₂Fe(μ‐SR)}₂]. These results might rationalize that the known protein‐Cys‐SNO sites derived from DNICs were located adjacent to acid and base motifs, and no protein‐bound SNO characterized to date has been directly derived from [protein–(cysteine)₂Fe(NO)₂] in biology.     

[(TMEDA)Co(NO)2][BPh4]: A versatile synthetic entry point to four and five coordinate {Co(NO)2} complexes

[(TMEDA)Co(NO)₂][BPh₄] reacts with Group 1 salts of various monoanionic ligands to yield four and five coordinate {Co(NO)₂}¹⁰ complexes. The synthesis of the four coordinate complex of the form [{LX}Co(NO)₂] via salt-metathesis reactions of [(TMEDA)Co(NO)₂][BPh₄] with [{ArNC(Me)CHC(Me)NAr}Li(OEt₂)] (Ar = 2,6-di-iso-propylphenyl) is reported. In addition [(TMEDA)Co(NO)₂][BPh₄] reacts with either KTp^∗ or a suite of cyclopentadienyllithium and cyclopentadienylsodium reagents, to generate the corresponding five coordinate [{L₂X}Co(NO)₂] complexes ({L₂X = C₅H₅, MeC₅H₄, Cp^∗, ^tBuC₅H₄, Ph₂CHC₅H₄, Me₃SiC₅H₄, ^tBuMe₂SiC₅H₄, ⁱPr₃SiC₅H₄, 1,3-(ⁱPr₃Si)₂C₅H₃ and Tp^∗). In support of existing precedent, the four coordinate complex is a thermally robust and readily isolable species while five coordinate complexes are thermally unstable transient intermediates that may either undergo dissociation of an NO ligand or be trapped by alkenes to form the corresponding metal dinitrosoalkane complexes. These reactions demonstrate that [(TMEDA)Co(NO)₂][BPh₄] provides a versatile synthetic entry point to cobalt dinitrosyl complexes and obviates the need for the repeated use of nitric oxide in the preparation of dinitrosoalkane complexes of cobalt.     

Syntheses,crystal structures and magnetic properties of two cyano-bridged two-dimensional assemblies [Fe(salpn)]2 [Fe(CN)5NO] and [Fe(salpn)]2[Ni(CN)4]

Two cyano-bridged assemblies, [Fe^III(salpn)]₂[Fe^II(CN)₅NO] (1) and [Fe^III (salpn)]₂[Ni^II(CN)₄] (2) [salpn = N, N-1,2-propylenebis(salicylideneiminato)dianion], have been prepared and structurally and magnetically characterized. In each complex, [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– coordinates with four [Fe(salpn)]⁺ cations using four co-planar CN^– ligands, whereas each [Fe(salpn)]⁺ links two [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– ions in the trans form, which results in a two-dimensional (2D) network consisting of pillow-like octanuclear [—M^II—CN—Fe^III—NC—]₄ units (M = Fe or Ni). In complex (1), the NO group of [Fe(CN)₅NO]^2– remains monodentate and the bond angle of Fe^II—N—O is 180.0°. The variable temperature magnetic susceptibilities, measured in the 5–300 K range, show weak intralayer antiferromagnetic interactions in both complexes with the intramolecular iron(III)iron(III) exchange integrals of –0.017 cm^–1 for (1) and –0.020 cm^–1 for (2), respectively.     

NO donors cis-[Ru(bpy)2(L)NO] and [Fe(CN)4(L)NO] complexes immobilized on modified mesoporous silica spheres

The reaction of [Ru(bpy)₂Cl₂] and Na₂[Fe(CN)₄(dmso)₂] complexes with isonicotinic acid immobilized on silica spheres (Si-ATPS-ISN) followed by a NO bubbling produced Si-ATPS-ISN-[Ru(bpy)₂(NO)] (system I) and Si-ATPS-ISN-[Fe(CN)₄(NO)] (system II). The characterization of these systems was carried out by UV–Vis, FTIR spectroscopy and electrochemical techniques. As judged by the FTIR data, the nitric oxide ligand has an NO⁺ character in both systems (ν(NO⁺): 1938 cm⁻¹). The NO release, which was monitored by means of FTIR, electrochemistry, and NO sensor electrode, was observed for both systems upon white light irradiation and chemical reduction by cysteine. These results indicated that the system (II) presents a higher potential for controlled NO release. The characterization (FTIR and UV–Vis) of the systems after the NO release suggested the formation of the aqua systems ATPS-ISN-[Ru(bpy)₂(OH₂)] and ATPS-ISN-[Ru(bpy)₂(OH₂)].     

Chelate structures of 5-(H/Br)-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazones (H2L): Synthesis and structural characterizations of [Ni(L)(PPh3)] and [Ru(HL)2(PPh3)2]

The reactions of 5-R-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazone {R: H (L¹); Br (L²)} with [M^II(PPh₃)nCl₂] (M = Ni, n = 2 and M = Ru, n = 3) in a 1:1 molar ratio have given stable solid complexes corresponding to the general formula [Ni(L)(PPh₃)] and [Ru(HL)₂(PPh₃)₂]. While the 1:1 nickel complexes are formed from an ONS donor set of the thiosemicarbazone and the P atom of triphenylphosphine in a square planar structure, the 1:2 ruthenium complexes consist of a couple from each of N, S and P donor atoms in a distorted octahedral geometry. These mixed-ligand complexes have been characterized by elemental analysis, IR, UV–Vis, APCI-MS, ¹H and ³¹P NMR spectroscopies. The structures of [Ni(L²)(PPh₃)] (II) and [Ru(L¹H)₂(PPh₃)₂] (III) were determined by single crystal X-ray diffraction.     

Cp2Ti{[OC(O)C5H4]Cr(CO)2NO]}2 and Cp2Ti{[(OC(O)C5H4]Cr(NO)2X}2 syntheses and spectra of chromium-titanium complexes bridged by carboxylate substituted cyclopentadienyl group

Complete demethylation of Cp₂Ti(CH₃)₂ in dichloromethane with 2 M equivalent of [η⁵-(C₅H₄COOH)]Cr(CO)₂NO (5), [η⁵-(C₅H₄COOH)]Cr(NO)₂X] (X = Cl 6, X = I 7), and [η⁵-(C₅H₄COOH)]W(CO)₃CH₃ (8); gives Cp₂Ti{[OC(O)C₅H₄]Cr(CO)₂NO}₂ (13), Cp₂Ti{[OC(O)C₅H₄]Cr(NO)₂Cl}₂ (14), Cp₂Ti{[OC(O)C₅H₄]Cr(NO)₂I}₂ (15),and Cp₂Ti{[OC(O)C₅H₄]W(CO)₃CH₃}₂ (16), respectively. The chemical shifts of C(2)-C(5) carbon atoms of compounds 13-15 have been assigned using two-dimensional HetCOR NMR spectroscopy. The assigned chemical shifts were compared with the NMR data of their analogues of ferrocene, and the opposite correlation on the assignments was observed for cynichrodenoyl moieties.     

Syntheses and X-ray structural studies of the novel complexes [Ni(en)2(3-pyt)2] and [Cu(en)2](3-pyt)2 based on 5-(3-pyridyl)-1,3,4-oxadiazole-2-thione

Two novel mononuclear mixed-ligand complexes [Ni(en)₂(3-pyt)₂] (1) and [Cu(en)₂](3-pyt)₂ (2), derived from potassium [N′-(pyridine-3-carbonyl)-hydrazinecarbodithioate [K⁺(H₂L)⁻] and containing en as a co-ligand, have been synthesized. The [K⁺(H₂L)⁻] undergoes cyclization in the presence of ethylenediamine (en) and is converted to 5-(3-pyridyl)-1,3,4-oxadiazole-2-thione (3-pyt)⁻. [Ni(en)₂(3-pyt)₂] and [Cu(en)₂](3-pyt)₂ have been characterized with the aid of elemental analyses, IR, UV–Vis, magnetic susceptibility and single crystal X-ray studies. The complexes 1 and 2 crystallize in the orthorhombic and monoclinic systems with space groups Pca2(1) and C2/c, respectively. The single crystal X-ray diffraction studies of both complexes indicate that (3-pyt)⁻ adopts a thione form in 1 but is present as a thiolato form in 2.     

Charge density studies on [(NO)Fe(S2C6H4)2][PPN] and [(NO)3Fe(S2C6H4)3] complexes

Charge density studies of chemical bonds for two iron complexes, [(NO)Fe(S,S-C₆H₄)₂] [PPN] (1), where PPN = N(Pph₃)₂ and Fe₃(NO)₃(S,S-C₆H₄)₃ (2) are investigated in terms of the topological properties at bond critical points based on the ‘atoms in molecule’ theory. The one electron reduction form (1R) of complex 1 and the one electron oxidation form (2O) of complex 2 are also included for comparison. The X-ray absorption spectroscopy of Fe K- and L_III,II-edges, as well as the N/S K-edge are applied to verify the illustration in the variation of the electronic structures. Based on the ρ_c, ?²ρ_c, and H_b values among the compound studied, Fe-S/N can be regarded as polarized covalent bond, and Fe-N bonds show stronger covalent character than that of the Fe–S bond, which is believed to be a highly polarized covalent bond.     

Neutral {Fe(NO)2}9 dinitrosyliron complex (DNIC) [(SC6H4-o-NHCOPh)(Im)Fe(NO)2] (Im = imidazole): interconversion among the anionic/neutral {Fe(NO)2}9 DNICs and Roussin's red ester

A neutral {Fe(NO)2}9 dinitrosyliron complex (DNIC) [(SC6H4-o-NHCOPh)(Im)Fe(NO)2] (Im = imidazole; 2) was prepared by the reaction of [Fe(mu-SC6H4-o-NHCOPh)(NO)2]2 (1) and 2 equiv of imidazole. In the synthesis of the anionic {Fe(NO)2}9 DNIC [(SC6H4-o-NHCOPh)2Fe(NO)2]- (3), thiolate [SC6H4-o-NHCOPh]- triggers ligand substitution of DNIC 2 to yield DNIC 3. At 298 K, complexes 2 and 3 exhibit well-resolved nine- and five-line electron paramagnetic resonance (EPR) signals at g = 2.031 and 2.029, respectively, the characteristic g value of DNICs. The facile interconversions among the neutral {Fe(NO)2}9 complex 2, the anionic {Fe(NO)2}9 complex 3, and Roussin's red ester 1 were demonstrated. The EPR spectrum (the pattern of hyperfine splitting) in combination with the IR nu(NO) (the relative position of the nu(NO) stretching frequencies) spectrum may serve as an efficient tool for the discrimination of the anionic {Fe(NO)2}9 DNICs, the neutral {Fe(NO)2}9 DNICs, and Roussin's red ester.     

Structural and energetic aspects of hydrogen bonding and proton transfer to ReH2(CO)(NO)(PR3)2 and ReHCl(CO)(NO)(PMe3)2 by IR and X-ray studies

The interaction of rhenium hydrides ReHX(CO)(NO)(PR₃)₂ 1 (X=H, R=Me (a), Et (b), iPr (c); X=Cl, R=Me (d)) with a series of proton donors (indole, phenols, fluorinated alcohols, trifluoroacetic acid) was studied by variable temperature IR spectroscopy. The conditions governing the hydrogen bonding ReHHX in solution and in the solid state (IR, X-ray) were elucidated. Spectroscopic and thermodynamic characteristics (−ΔH=2.3–6.1 kcal mol⁻¹) of these hydrogen bonded complexes were obtained. IR spectral evidence that hydrogen bonding with hydride atom precedes proton transfer and the dihydrogen complex formation was found. Hydrogen bonded complex of ReH₂(CO)(NO)(PMe₃)₂ with indole (2a–indole) and organyloxy-complex ReH(OC₆H₄NO₂)(CO)(NO)(PMe₃)₂ (5a) were characterized by single-crystal X-ray diffraction. A short NHHRe (1.79(5) Å) distance was found in the 2a–indole complex, where the indole molecule lies in the plane of the Re(NO)(CO) fragment (with dihedral angle between the planes 0.01°).     

Phenol nitration induced by an {Fe(NO)2}(10) dinitrosyl iron complex

Cellular dinitrosyl iron complexes (DNICs) have long been considered NO carriers. Although other physiological roles of DNICs have been postulated, their chemical functionality outside of NO transfer has not been demonstrated thus far. Here we report the unprecedented dioxygen reactivity of a N-bound {Fe(NO)(2)}(10) DNIC, [Fe(TMEDA)(NO)(2)] (1). In the presence of O(2), 1 becomes a nitrating agent that converts 2,4,-di-tert-butylphenol to 2,4-di-tert-butyl-6-nitrophenol via formation of a putative iron-peroxynitrite [Fe(TMEDA)(NO)(ONOO)] (2) that is stable below -80 °C. Iron K-edge X-ray absorption spectroscopy on 2 supports a five-coordinated metal center with a bound peroxynitrite in a cyclic bidentate fashion. The peroxynitrite ligand of 2 readily decays at increased temperature or under illumination. These results suggest that DNICs could have multiple physiological or deleterious roles, including that of cellular nitrating agents.     

Mononitrosyl tris(thiolate) iron complex [Fe(NO)(SPh)3]- and dinitrosyl iron complex [(EtS)2Fe(NO)2]-: formation pathway of dinitrosyl iron complexes (DNICs) from nitrosylation of biomimetic rubredoxin [Fe(SR)4]2-/1- (R = Ph, Et)

Nitrosylation of the biomimetic reduced- and oxidized-form rubredoxin [Fe(SR)4]2-/1- (R = Ph, Et) in a 1:1 stoichiometry led to the formation of the extremely air- and light-sensitive mononitrosyl tris(thiolate) iron complexes (MNICs) [Fe(NO)(SR)3]- along with byproducts [SR]- or (RS)2. Transformation of [Fe(NO)(SR)3]- into dinitrosyl iron complexes (DNICs) [(RS)2Fe(NO)2]- and Roussin's red ester [Fe2(mu-SR)2(NO)4] occurs rapidly under addition of 1 equiv of NO(g) and [NO]+, respectively. Obviously, the mononitrosyl tris(thiolate) complex [Fe(NO)(SR)3]- acts as an intermediate when the biomimetic oxidized- and reduced-form rubredoxin [Fe(SR)4]2-/1- exposed to NO(g) were modified to form dinitrosyl iron complexes [(RS)2Fe(NO)2]-. Presumably, NO binding to the electron-deficient [Fe(III)(SR)4]- and [Fe(III)(NO)(SR)3]- complexes triggers reductive elimination of dialkyl/diphenyl disulfide, while binding of NO radical to the reduced-form [Fe(II)(SR)4]2- induces the thiolate-ligand elimination. Protonation of [Fe(NO)(SEt)3]- yielding [Fe(NO)(SPh)3]- by adding 3 equiv of thiophenol and transformation of [Fe(NO)(SPh)3]- to [Fe(NO)(SEt)3]- in the presence of 3 equiv of [SEt]-, respectively, demonstrated that complexes [Fe(NO)(SPh)3]- and [Fe(NO)(SEt)3]- are chemically interconvertible. Mononitrosyl tris(thiolate) iron complex [Fe(NO)(SPh)3]- and dinitrosyl iron complex [(EtS)2Fe(NO)2]- were isolated and characterized by X-ray diffraction. The mean NO bond distances of 1.181(7) A (or 1.191(7) A) in complex [(EtS)2Fe(NO)2]- are nearly at the upper end of the 1.178(3)-1.160(6) A for the anionic {Fe(NO)2}9 DNICs, while the mean FeN(O) distances of 1.674(6) A (or 1.679(6) A) exactly fall in the range of 1.695(3)-1.661(4) A for the anionic {Fe(NO)2}9 DNICs.     

Diamine incorporated compounds derived from polymeric nickel(II) fumarates and oxalates: Crystal structure, spectral and thermal properties of [Ni(en)3](O2CCHCHCO2)·3H2O and [Ni(en)3](O2CCO2)

Lewis-base mediated fragmentation of polymeric nickel(II) fumarate and oxalate are attempted using chelating σ-donor diamines like ethylenediamine (en) and 1,3-diaminopropane (dap) in various conditions which yielded [Ni(en)₃](fum)·3H₂O (1), [Ni(en)₃](ox) (2), [Ni(dap)₂(fum)] (3) and [Ni(dap)(ox)]·2H₂O (4). While 1 and 2 are molecular products each containing octahedral [Ni(en)₃]²⁺ moieties and the anionic dicarboxylate species, 3 and 4 are dap-incorporated polymeric products. The fumarate derivative 1 containing [Ni(en)₃]²⁺ moieties crystallizes in the monoclinic space group C2/c with a = 17.899(4) Å, b = 11.747(2) Å, c = 10.748(2) Å, β = 125.59(3)°, V = 1837.7(6) ų, Z = 4, while the oxalate analogue 2 is seen to be in the trigonal space group P−31c with a = 8.8770(13) Å, b = 8.8770(13) Å, c = 10.482(2) Å, γ = 120°, V = 715.3(2) ų, Z = 2. The octahedral [Ni(en)₃] units in both 1 and 2 are seen to be strongly H-bonded to the dicarboxylate moieties through the coordinated en units leading to a three-dimensional network. However, in 1 the water molecules also take part in the H-bonding and contribute to the overall 3D structure. In both 1 and 2 the crystal packing is done with the [Ni(en)₃]²⁺ units with absolute configuration Λ(δδδ) and its mirror conformer with Δ configuration in exactly equal numbers. Spectral (IR and UV–Visible) and magnetic measurements were carried out and some of the ligand-field parameters like D_q, B and β were evaluated for all the four compounds. These values suggest the presence of octahedrally coordinated nickel(II) in all the four complexes. Spectral data suggest that 3 has the two chelating dap moieties and the fumarate coordinated in η¹ form through both its carboxylate moieties while 4 has one chelating dap and the oxalate moiety coordinated in η⁴-bis-chelating form. Though both 1 and 2 are made of the same type of [Ni(en)₃]²⁺ units their thermograms give entirely different thermal features; 1 showing three clearly successive and step-wise dissociation of each en unit while 2 having a combined loss of two en units in the first thermal step. The relevant thermodynamic and kinetic parameters like E_a and ΔS also could be evaluated for various thermal steps for the compounds 1–4 using Coats–Redfern equation.     

Fe–Hg Interactions and P Chemical Shifts in [Fe(CO)3 (PPh2R)2(HgCl2)] (R=pym, fur, py, thi)

In order to study the effects of R group on Fe–Hg interactions and 31P chemical shifts, the structures of mononuclear complexes Fe(CO)₃(PPh₂R)₂ (R=pym:1, fur: 2, py: 3,thi: 4; pym=pyrimidine, fur=furyl, py=pyridine, thi=thiazole) and binuclear complexes [Fe(CO)₃(PPh₂R)₂(HgCl₂)] (R=pym: 5, fur: 6, py: 7, thi: 8) were studied using the density functional theory (DFT) PBE0 method. The 31P chemical shifts were calculated by PBE0-GIAO method. Nature bond orbital (NBO) analyses were also performed to explain the nature of the Fe–Hg interactions. The conclusions can be drawn as follows: (1) The complexes with nitrogen donor atoms are more stable than those with O or S atoms. The more N atoms there are, the higher is the stabilility of the complex. (2) The Fe–Hg interactions play a dominant role in the stabilities of the complexes. In 5 or 6, thereisa σ-bond between Fe and Hg atoms. However, in 7 and 8, the Fe–Hg interactions act as σ_P–Fe→n_Hg and σ_C–Fe→n_Hg delocalization. (3) Through Fe→Hg interactions, there is charge transfer from R groups towards the P, Fe, and Hg atoms, which increases the electron density on P nucleus in binuclear complexes. As a result, compared with their mononuclear complexes, the 31P chemical shifts in binuclear complexes show some reduction.     

Solvothermal synthesis of three new dimeric thiogermanates (enH)4Ge2S6, [Mn(en)3]2Ge2S6 and [Ni(en)3]2Ge2S6 from germanium dioxide and sulfur powder

Three new thiogermanates (enH)₄Ge₂S₆ (1) and [M(en)₃]₂Ge₂S₆ (M=Mn (2), Ni (3); en=ethylenediamine) were synthesized using GeO₂ and S₈ as starting materials in molar ratio of 1:0.5 under solvothermal conditions. These compounds suggest that the dimeric [Ge₂S₆]⁴⁻ anion is likely to be the main germanium-containing species in en system and it also might be preferred as counter anions by the transition metal complex cations in crystallization. The cations of [Mn(en)₃]²⁺ and [Ni(en)₃]²⁺ are even better mineralizers than the protonated amine of [enH]⁺. The crystal systems of [Ge₂S₆]⁴⁻ compounds are related to entities of cations and intermolecular reactions between cations and [Ge₂S₆]⁴⁻ anions. The compounds remove ethylenediamine and H₂S molecules in multi steps when being heated under nitrogen stream.     

Formation of [Cp2TiSbMe2]2, [Cp2TiSb(SiMe3)2]2 and [Cp2TiCl]2·2Mes4Sb2

Reactions of [Cp₂Ti(btmsa)] (btmsa = bis(trimethylsilyl)acetylene) with R₄Sb₂ (R = Me, Me₃Si) give [Cp₂TiSbMe₂]₂ (1) or [Cp₂TiSb(SiMe₃)₂]₂ (2) respectively. [Cp₂TiCl]₂·2Mes₄Sb₂ (3) is serendipitously formed from [Cp₂Ti(btmsa)] and Mes₂SbH containing NH₄Cl traces.     

Reactions of [ReX5(NO)]2− with triphenylstibine. Spectroscopic investigations of [ReX2(NO)(SbPh3)3], X-ray structures of [ReCl2(NO)(SbPh3)3] and [ReBr2Cl(SbPh3)3] and DFT calculations for [ReCl2(NO)(SbPh3)3]

The reactions of [NBu₄]₂[ReX₅(NO)] (X = Cl, Br) with triphenylstibine have been examined and three new rhenium complexes – [ReCl₂(NO)(SbPh₃)₃] (1), [ReBr₂(NO)(SbPh₃)₃] (2) and [ReBr₂Cl(SbPh₃)₃] (3) – have been obtained. The last one has been isolated in a low yield during slow recrystallization of the complex 2 from a mixture of chloroform and ethanol. The stibine rhenium nitrosyls have been characterized by IR and UV–vis spectroscopy. The X-ray structures of 1 and 3 have been determined. The geometric parameters of 1 have been examined using the density functional theory (DFT) method.