Iron(III) hetero-ligand complexes containing 1,10-phenanthroline derivatives, chloride and dimethyl sulfoxide: synthesis, characterization, crystal structure determination and luminescent properties

[Fe(Me-phen)Cl₄][Me-phen·H] (1) and [Fe(Cl-phen)Cl₄][Cl-phen·H] (2) complexes were prepared from the reactions of FeCl₃·6H₂O with 5-methyl-1,10-phenanthroline (Me-phen) and 5-chloro-1,10-phenanthroline (Cl-phen), respectively, in a 0.1 M aqueous solution of HCl. Stepwise addition of dimethyl sulfoxide to the solution of 1 in methanol results in a mixed ligand complex, [Fe(Me-phen)Cl₃(DMSO)] (3). Complex 3 was also prepared by two other methods. The reaction of a methanol solution of [Fe(Me-phen)Cl₄][Me-phen·H] (1) with [Fe(DMSO)₄Cl₂][FeCl₄] in 1:6 ratio led to 3. Complex 3 was also prepared from the reaction of 5-methyl-1,10-phenanthroline with [Fe(DMSO)₄Cl₂][FeCl₄] in 1:1 ratio in methanol. The three complexes were characterized by IR, UV–Vis, ¹H NMR and luminescence spectroscopy and their structures were studied by the single-crystal diffraction method. Calculation methods were employed to study the isomerization of (3) in solution.     

Mixed-ligand complexes of iron(II), iron(III), copper(II), and cobalt(II) with pyrazolonic and 2,2′-bipyridine ligands

New mixed-ligand complexes, [M₂(BAMP)(bipy)₂][MCl₄]₂, M=Co⁺²(1), Cu⁺²(2), [M₂(TAMEN)(bipy)₂][MCl₄]₂, M=Fe⁺²(3), Co²⁺(4), and [Fe₂(TAMEN)(bipy)₂][FeCl₆]₂ (5), where BAMP and TAMEN stand for the Mannich bases N,N′-bis(antipyryl-4-methylene)-piperazine and N,N′-tetra(antipyryl-4-methylene)-1,2-ethane-diamine, respectively, have been obtained and characterized by elemental analyses, conductometric and magnetic susceptibility measurements at room temperature, mass spectrometry, UV-Vis, infrared, and mass spectroscopy, and ¹H NMR spectra for the ligands.     

The Coordination Chemistry of Iron with the 1,4‐Bis(2‐pyridyl‐methyl)piperazine Ligand

The behaviour of Fe^II and Fe^III ions in combination with the potential ligand 1,4‐bis(2‐pyridyl‐methyl)piperazine (BPMP) under anhydrous conditions has been investigated. BPMP has been reacted with FeCl₂, FeCl₃ and [Fe(OTf)₂(MeCN)₂]. This led to the isolation of four new complexes, which were fully characterized and structurally investigated by single crystal X‐ray diffraction. It turned out that in the presence of chloride co‐ligands Fe^III favours the tetradentate coordination mode of BPMP with the piperazine unit in a boat configuration, like for instance in [BPMP(Cl)Fe(μ‐O)FeCl₃] or [BPMP‐FeCl₂][FeCl₄], ( 1 ). However, the employment of FeCl₂ leads to the formation of a coordination polymer [BPMP‐FeCl₂]_n, ( 2 ), containing the piperazine ring in a chair configuration binding to two iron centres each. 2 can only be dissolved in very polar solvents like dmf which is capable of breaking up the polymeric structure under formation of [Cl₂(dmf)Fe(μ‐BPMP‐1κ²N,N:2κ²N,N))Fe(dmf)Cl₂]·2 dmf, ( 3 ). In contrast, using [Fe(OTf)₂(MeCN)₂] instead of FeCl₂ as the starting material leads to a mononuclear Fe^II complex with BPMP bound in the desirable tetradentate fashion: [BPMP‐Fe(OTf)₂], ( 4 ). Unlike other complexes with tetradentate N/py ligands the two residual ligands in 4 are bound almost trans to each other with the potential to adopt a cis orientation under oxidising conditions, and it will be interesting to exploit its catalytic properties in future.     

Boron Cluster Anions [BnHn]2– (n = 10, 12) in Reactions of Iron(II) and Iron(III) Complexation with 2, 2′‐Bipyridyl and 1, 10‐Phenanthroline

Complexation of Fe^II and Fe^III with azaheterocyclic ligands L (L = phen or bipy) were studied in the presence and in the absence of boron cluster anions [B_nH_n]^2– (n = 10, 12). The reactions were carried out in air at room temperature in organic solvents and/or water. In all the solvents used, well known [FeL₃]An (An = 2Cl^– or SO₄^2–) ferrous complexes were formed from Fe^II salts. Composition of ferric complexes with L ligands depends on the nature of solvent: either dinuclear oxo‐iron(III) chlorides [L₂ClFe^III–O–Fe^IIIL₂Cl]Cl₂ or ferric ferrates(III) [Fe^IIIL₂Cl₂][Fe^IIICl₄], or [Fe^IIIL₂Cl₂][Fe^IIICl₄L] were isolated from Fe^III salts. Introduction of the closo‐borate anions to a Fe³⁺(or Fe²⁺)/L/solv. mixture stabilizes ferrous cationic complexes [FeL₃]²⁺ in all the solvents used: only ferrous [FeL₃][B_nH_n] (n = 10, 12) complexes were isolated from all the reaction mixtures in the presence of boron cluster anions.     

Unknown cis-[(DMSO)2ClCuII(μ-Cl)2CuIICl(DMSO)2] isomer obtained via new [Cu4Cl8(DMSO)8(hmta)] template complex

A missed cis isomeric form of a well-known trans-[CuCl₂(DMSO)₂]_n complex has been prepared via the tetranuclear [Cu₄Cl₈(DMSO)₈(hmta)] complex. Structurally, both complexes were found to be molecular i.e. [Cu₄Cl₈(DMSO)₈(hmta)] consists of isolated tetracoordinated hexamethylenetetramine molecules, whereas the cis-complex consists of isolated [(DMSO)₂ClCu^II(μ-Cl)₂Cu^IICl(DMSO)₂] clusters. It should also be noted that the cis-configuration of DMSO molecules in [(DMSO)₂ClCu^II(μ-Cl)₂Cu^IICl(DMSO)₂] was directly transferred from that of [Cu₄Cl₈(DMSO)₈(hmta)], while the trans-[CuCl₂(DMSO)₂]_n isomer was always formed as a final stable product.     

Influence of Central Metalloligand Geometry on Electronic Communication between Metals: Syntheses,Crystal Structures,MMCT Properties of Isomeric Cyanido‐Bridged Fe2Ru Complexes,and TDDFT Calculations

To investigate how the central metalloligand geometry influences distant or vicinal metal‐to‐metal charge‐transfer (MMCT) properties of polynuclear complexes, cis‐ and trans‐isomeric heterotrimetallic complexes, and their one‐ and two‐electron oxidation products, cis/trans‐ [Cp(dppe)Fe^IINCRu^II(phen)₂CN‐Fe^II(dppe)Cp][PF₆]₂ (cis/trans‐ 1 [PF₆]₂), cis/trans‐[Cp(dppe)Fe^IINCRu^II(phen)₂CNFe^III‐(dppe)Cp][PF₆]₃ (cis/trans‐ 1 [PF₆]₃) and cis/trans‐[Cp(dppe)Fe^IIINCRu^II(phen)₂CN‐Fe^III(dppe)Cp][PF₆]₄ (cis/trans‐ 1 [PF₆]₄) have been synthesized and characterized. Electrochemical measurements show the presence of electronic interactions between the two external Fe^II atoms of the cis‐ and trans‐isomeric complexes cis/trans‐ 1 [PF₆]₂. The electronic properties of all these complexes were studied and compared by spectroscopic techniques and TDDFT//DFT calculations. As expected, both mixed valence complexes cis/trans‐ 1 [PF₆]₃ exhibited different strong absorption signals in the NIR region, which should mainly be attributed to a transition from an MO that is delocalized over the Ru^II‐CN‐Fe^II subunit to a Fe^III d orbital with some contributions from the co‐ligands. Moreover, the NIR transition energy in trans‐ 1 [PF₆]₃ is lower than that in cis‐ 1 [PF₆]₃, which is related to the symmetry of their molecular orbitals on the basis of the molecular orbital analysis. Also, the electronic spectra of the two‐electron oxidized complexes show that trans‐ 1 [PF₆]₄ possesses lower vicinal Ru^II→Fe^III MMCT transition energy than cis‐ 1 [PF₆]₄. Moreover, the assignment of MMCT transition of the oxidized products and the differences of the electronic properties between the cis and trans complexes can be well rationalized using TDDFT//DFT calculations.     

Carbonyl complexes of manganese(I) with pyridazine: Synthesis and1H n.m.r. study

Summary Three new pyridazine complexes of manganese(I): [MnBr(pyr)₂(CO)₃] (1), [Mn(pyr)(CO)₅][ClO₄] (2) and [Mn(pyr)₃(CO)₃][ClO₄] (3) (pyr=pyridazine) have been prepared and their i.r. and variable-temperature¹H n.m.r. spectra investigated.     

Divalent Lanthanide Tetraisobutylaluminates: Reactivity and Living Isoprene Polymerization

Lanthanide (Ln) tetraisobutylaluminates constitute key components in commercial 1,3-diene polymerization catalysts, and likewise are the homogeneous rare-earth-metal catalysts of prime industrial importance. Discrete divalent rare-earth-metal complexes [Ln(AliBu₄)₂] (Ln=Sm, Eu, Yb) reported here display the first structurally characterized homoleptic metal tetraisobutylaluminates. Treatment of [Ln(AliBu₄)₂] with C₂Cl₆ gives access to Sm^II/Sm^III mixed-valence cluster [Sm₆Cl₈(AliBu₄)₆] and the Yb^II cluster [Yb₄Cl₄(AliBu₄)₄], respectively. Reaction with B(C₆F₅)₃ leads to hydride abstraction and formation of arene-coordinated hydroborates such as [Sm{HB(C₆F₅)₃}₂(toluene)₂]. Complexes [Ln(AliBu₄)₂] engage in single-component isoprene polymerization, affording high cis-1,4 polyisoprenes with narrow molecular weight distributions. Binary [Yb(AliBu₄)₂]/[HNPhMe₂][B(C₆F₅)₄] fabricates polyisoprene in a perfectly living manner. The catalytically active species are scrutinized by NMR spectroscopy.     

Chemistry of iron complexes. Part V. Electron spin resonance spectra of some iron(III) complexes and X-Ray diffraction (powder) data of iron(II) complexes employing tertiary phosphine/arsine oxides

Summary Electron spin resonance spectra (X-band, 9.3 GHz) of iron(III) chloride complexes with tri-p-tolylarsine oxide (T₃AO), methylenebis(diphenylphosphine oxide) (mdpo) and 1,4-tetramethylenebis(diphenylphosphine oxide) (tmdpo) support their structures as [Fe(L-L)₂Cl₂][FeCl₄] (L-L=mdpo or tmdpo) and [Fe(T₃AO)₂Cl₂(OH₂)₂][FeCl₄]2H₂O. The x-ray powder diffraction patterns of some iron(II) iodide complexes with mdpo, tmdpo, dmdpo, dmdao and tmdao [dmdpo-1,2-dimethylenebis(diphenylphosphine oxide); dmdao and tmdao are the arsine analogs of dmdpo and tmdpo] show that the complexes are crystalline but not isomorphous.     

Reactivity of Ammonium Halides: Action of Ammonium Chloride and Bromide on Iron and Iron(III) Chloride and Bromide

Ammonium chloride and bromide, (NH₄)Cl and (NH₄)Br, act on elemental iron producing divalent iron in [Fe(NH₃)₂]Cl₂ and [Fe(NH₃)₂]Br₂, respectively, as single crystals at temperatures around 450 °C. Iron(III) chloride and bromide, FeCl₃ and FeBr₃, react with (NH₄)Cl and (NH₄)Br producing the erythrosiderites (NH₄)₂[Fe(NH₃)Cl₅] and (NH₄)₂[Fe(NH₃)Br₅], respectively, at fairly low temperatures (350 °C). At higher temperatures, 400 °C, iron(III) in (NH₄)₂[Fe(NH₃)Cl₅] is reduced to iron(II) forming (NH₄)FeCl₃ and, further, [Fe(NH₃)₂]Cl₂ in an ammonia atmosphere. The reaction (NH₄)Br + Fe (4:1) leads at 500 °C to the unexpected hitherto unknown [Fe(NH₃)₆]₃[Fe₈Br₁₄], a mixed‐valent Fe^II/Fe^I compound. Thermal analysis under ammonia and the conditions of DTA/TG and powder X‐ray diffractometry shows that, for example, FeCl₂ reacts with ammonia yielding in a strongly exothermic reaction [Fe(NH₃)₆]Cl₂ that at higher temperatures produces [Fe(NH₃)]Cl₂, FeCl₂ and, finally, Fe₃N.     

Crystal Structures of (PPh3)2Pd(N3)2, (AsPh3)2Pd(N3)2, (2‐Chloropyridine)2Pd(N3)2, [(AsPh4)2][Pd2(N3)4Cl2], [(PNP)2][Pd(N3)4], [(AsPh4)2][Pt(N3)4] · 2 H2O,and [(AsPh4)2][Pt(N3)6]

The crystal structures of the monomeric palladium(II) azide complexes of the type L₂Pd(N₃)₂ (L = PPh₃ ( 1 ), AsPh₃ ( 2 ), and 2‐chloropyridine ( 3 )), the dimeric [(AsPh₄)₂][Pd₂(N₃)₄Cl₂] ( 4 ), the homoleptic azido palladate [(PNP)₂][Pd(N₃)₄] ( 5 ) and the homoleptic azido platinates [(AsPh₄)₂][Pt(N₃)₄] · 2 H₂O ( 6 ) and [(AsPh₄)₂][Pt(N₃)₆] ( 7 ) were determined by X‐ray diffraction at single crystals. 1 and 2 are isotypic and crystallize in the triclinic space group P1. 1 , 2 and 3 show terminal azide ligands in trans position. In 4 the [Pd₂(N₃)₄Cl₂]^2– anions show end‐on bridging azide groups as well as terminal chlorine atoms and azide ligands. The anions in 5 and 6 show azide ligands in equal positions with almost local C_4h symmetry at the platinum and palladium atom respectively. The metal atoms show a planar surrounding. The [Pt(N₃)₆]^2– anions in 7 are centrosymmetric (idealized S₆ symmetry) with an octahedral surrounding of six nitrogen atoms at the platinum centers.     

Synthesis and characterization of new paramagnetic tetraaryl derivatives of chromium and molybdenum

The low-temperature reaction of [CrCl₃(thf)₃] with LiC₆H₃Cl₂-2,6 yields the organochromium(III) compound [Li(thf)₄][Cr^III(C₆H₃Cl₂-2,6)₄] (1) in 48% yield. The homoleptic, anionic species [Cr^III(C₆H₃Cl₂-2,6)₄]⁻ is electrochemically related to the neutral one [Cr^IV(C₆H₃Cl₂-2,6)₄] (2) through a reversible one-electron exchange process (E_1/2 = 0.16 V, ΔE_p = 0.09 V, i_pa/i_pc = 1.18). Compound 2 was isolated in 74% yield by chemical oxidation of 1 with [N(C₆H₄Br-4)₃][SbCl₆]. Attempts to prepare the salt [NBu₄][Cr^III(C₆Cl₅)₄] (4) by direct arylation of [CrCl₃(thf)₃] with LiC₆Cl₅ in the presence of [NBu₄]Br gave the organochromium(II) salt [NBu₄]₂[Cr^II(C₆Cl₅)₄] (3) instead, as the result of a reduction process. The salt [NBu₄][Cr^III(C₆Cl₅)₄] (4) was cleanly prepared by comproportionation of 3 and [Cr^IV(C₆Cl₅)₄]. The reaction of [MoCl₄(dme)] with LiC₆Cl₅ in Et₂O solution proceeded with oxidation of the metal center to give the paramagnetic (S = 1/2), five-coordinate salt [Li(thf)₄][Mo^VO(C₆Cl₅)₄] (5). The crystal and molecular structures of 1 and 2 have been established by X-ray diffraction methods. The magnetic properties of 1 and 4 (S = 3/2) as well as those of 2 (S = 1) have been established by EPR spectroscopy as well as by ac and dc magnetization measurements.     

RuII and RuIII Chloronitrile Complexes: Synthesis,Reaction Chemistry,Solid State Structure,and (Spectro)Electrochemical Behavior

The synthesis of [Ti₆O₄(OiPr)₈(O₂CPh)₈] ( 3 ) and [RuCl(N≡CR)₅][RuCl₄(N≡CR)₂] ( 4a , R = Me; 4b , R = Ph), [Ru(N≡CPh)₆][RuCl₄(N≡CPh)₂] ( 5 ) and [H₃O][RuCl₄(N≡CMe)₂] ( 7a ) is discussed. Crystallization of 5 from CH₂Cl₂ gave trans-[RuCl₂(N≡CPh)₄] ( 6 ). The solid-state structures of 3 , 4a , b , 5 , 6 and 7a are reported. Complex 4b forms a 3D network, while 6 displays a 2D structure, due to π-interactions between the benzonitrile ligands. The (spectro)electrochemical behavior of 4a , b and 6 was studied at 25 and –72 °C and the results thereof are compared with [NEt₄][RuCl₄(N≡CMe)₂] ( 7b ) and [RuCl(N≡CPh)₅][PF₆] ( 8 ). The electrochemical response of the cation and the anion in 4a , b are independent from each other. [RuCl(N≡CR)₅]⁺ possesses one reversible Ru^II/Ru^III process. However, [RuCl₄(N≡CMe)₂]^– was shown to be prone to ligand exchange and disproportionation upon formation of either a Ru^IV and Ru^II species at 25 °C, while at –72 °C the rapid conversion of the electrochemically formed species is hindered. In situ IR and UV/Vis/NIR studies confirmed the respective disproportionation reaction products of the aforementioned oxidation and reduction, respectively.     

Iron(III) mixed-ligand complexes: Synthesis,characterization and crystal structure determination of iron(III) hetero-ligand complexes containing 1,10-phenanthroline, 2,2′-bipyridine,chloride and dimethyl sulfoxide, [Fe(phen)Cl3(DMSO)] and [Fe(bipy)Cl3(DMSO)]

Treatment of [Fe(bipy)Cl₄][bipy · H] (1) and [Fe(phen)Cl₄][phen · H] (3) (where bipy is 2,2′-bipyridine and phen is 1,10-phenanthroline) with dimethyl sulfoxide in methanolic solution produced [Fe(bipy)Cl₃(DMSO)] (2) and [Fe(phen)Cl₃(DMSO)] (4) (where DMSO is dimethyl sulfoxide), respectively. The resulting complexes were characterized by elemental analysis, IR, UV–Vis and ¹H NMR spectroscopies and by the X-ray diffraction method. These complexes are high spin with a spin multiplicity of 6.     

Reactions of cationic rhodium(I) carbonyl compounds with nucleophiles to form alkoxo,carboalkoxy and carboxylato complexes. Part II

Summary The rhodium(I) carbonyl compounds [Rh(CO)L₂2] [BF₄]. 1/2CH₂Cl_nn2 (L = PPh₂ or AsPh₃) react with the nucleophiles OMe⁻, RCOO⁻ (R = Me, Et) under nitrogen to form [Rh(OR)(CO)L₂] (1)–(2) and [Rh(OOCR)(CO)L₂] (7)–(₁₀), respectively. Addition of [Rh(CO)₂(PPh₃)₂]-[BF ₄] to OMe⁻ under nitrogen produces [Rh(COOMe)-(CO) (PPh₃)₂]-MeOH (3), whilst reactions of [Rh(CO)-(PPh₃)₂] [BF₄]·1/2CH₂Cl₂ and [Rh(CO)₂(PPh₃)₂] [BF₄] with OR_- (R = Me, Et or n-Pr) in the presence of CO produce [Rh(COOR)(CO)₂(PPh₃)₂] (4)–(6). The products have been characterised by i.r., ¹H, ³¹P, ¹³Cn.m.r. spectroscopy and elemental analysis.     

Synthesis and some properties of anionic chloranilate complexes of iron(iii). Crystal and molecular structure of rubidium and cesium chloranilatoferrates

New anionic chloranilate complexes of iron(iii) Cs[Fe(C₆O₄Cl₂)₂(H₂O)₂]·4H₂O (1), Rb[Fe(C₆O₄Cl₂)₂(H₂O)₂]·4H₂O (2), Rb₂[Fe(C₆O₄Cl₂)₂(H₂O)₂]₂·5H₂O (3), Cs₃Fe(C₆O₄Cl₂)₃ (4), (Bu₄N)Fe(C₆O₄Cl₂)₂ (5), (Bu₄N)₄Fe₂(C₆O₄Cl₂)₅ (6), and (R₄N)₃Fe(C₆O₄Cl₂)₃ (R = Pr (7), Bu (8), C₅H₁₁ (9)) were synthesized in an aqueous medium. The Mössbauer spectra of the synthesized chloranilatoferrates are characteristic of the high-spin state of Fe^III in an octahedral oxygen coordination. The crystal and molecular structures of compounds 1–3 were determined by X-ray diffraction. The complex anions [Fe(C₆O₄Cl₂)₂(H₂O)₂]^2? involved in these compounds are composed of two chelate chloranilate ions and two water molecules trans-(1,2) or cis-coordinated (3) to the iron atom. Since tetraalkylammonium tris(chloranilato)ferrates 7–9 and binuclear complex 6 are soluble in many organic solvents, they are promising precursors for the synthesis of metal-organic coordination polymers. Tetrabutylammonium bis(chloranilato)ferrate (Bu₄N)Fe(C₆O₄Cl₂)₂ (5) is the first example of the preparation of an anionic chloranilate complex of iron(iii) with a plausible chain structure in an aqueous medium.     

Chemie der Isoblausäure. VIII. Protonierung eines ‚mobilen’︁ Cyanoliganden: cis-[(μ-CNH2)Fe2Cp2(CO)3]X (X = Cl,BF4, PF6, I)

Chemistry of Hydrogen Isocyanide. VIII. Protonation of a ‘Mobile’ Cyano Ligand: cis-[μ-CNH₂)Fe₂Cp₂(CO)₃]X (X = Cl, BF₄, PF₆, I) . Protonation of the terminal cyano ligand in the complex cis-Na[Fe₂(CN)Cp₂(CO)₃] affords the N-diprotonated produkt [Fe₂Cp₂(CO)₃(μ-CNH₂)]⁺ X^? (X = Cl, BF₄, PF₆, I) exclusively; the structure of the chloride has been determined by X-ray analysis.     

Molecular Insights into the Ligand-Based Six-Proton- and Six-Electron-Transfer Processes Between Tris-ortho-Phenylenediamines and Tris-ortho-Benzoquinodiimines

The global demand for energy and the concerns over climate issues renders the development of alternative renewable energy sources such as hydrogen (H₂) important. A high-spin (hs) Fe^II complex with o-phenylenediamine (opda) ligands, [Fe^II(opda)₃]²⁺ (hs- [6R] ²⁺), was reported showing photochemical H₂ evolution. In addition, a low-spin (ls) [Fe^II(bqdi)₃]²⁺ (bqdi: o-benzoquinodiimine) (ls- [0R] ²⁺) formation by O₂ oxidation of hs- [6R] ²⁺, accompanied by ligand-based six-proton and six-electron transfer, revealed the potential of the complex with redox-active ligands as a novel multiple-proton and -electron storage material, albeit that the mechanism has not yet been understood. This paper reports that the oxidized ls- [0R] [PF₆]₂ can be reduced by hydrazine giving ls-[Fe^II(opda)(bqdi)₂][PF₆]₂ (ls- [2R] [PF₆]₂) and ls-[Fe^II(opda)₂(bqdi)][PF₆]₂ (ls- [4R] [PF₆]₂) with localized ligand-based proton-coupled mixed-valence (LPMV) states. The first isolation and characterization of the key intermediates with LPMV states offer unprecedented molecular insights into the design of photoresponsive molecule-based hydrogen-storage materials.     

Structural variations in nickel, palladium, and platinum complexes containing pyrimidyl N-heterocyclic carbene ligand

Nickel(II), palladium(II), and platinum(II) complexes of 2-(3-mesitylimidazolylidenyl)pyrimidine (L), [Ni₂(μ-Cl)₂(L)₄][Ag₂Cl₄] (3), [Ni₂(μ-I)₂(L)₄][NiI(L)₂(CH₃CN)]₂[Ag₄I₈] (4), [PdCl₂(L)] (5), [PdI₂(L)] (6), and [PtCl(L)₂][AgCl₂] (7) have been obtained from the carbene transfer reactions of [Ag(L)Cl] (2). These complexes have been fully characterized by spectroscopic methods and single-crystal X-ray structure analyses. The mono(carbene)palladium and bis(carbene)platinum complexes display normal square–planar structures. Nickel complexes 3 and 4 are rare examples of paramagnetic nickel(II) complexes of N-heterocyclic carbenes having octahedral geometry.     

Synthetic and structural studies of the diiron toluenedithiolate carbonyl complexes with monophosphine ligands

Four diiron toluenedithiolate complexes 2–5 with monophosphine ligands are reported. Treatment of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₆ (1) with tris(3-chlorophenyl)phosphine, tris(4-chlorophenyl)phosphine, tris(4-methylphenyl)phosphine or 2-(diphenylphosphino)benzaldehyde, and Me₃NO?2H₂O in MeCN resulted in the formation of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(3-C₆H₄Cl)₃] (2), [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄Cl)₃] (3), [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄CH₃)₃] (4), and [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[Ph₂P(2-C₆H₄CHO)] (5) in 64–82% yields. Complexes 2–5 have been characterized by elemental analysis, IR, ¹H NMR, ³¹P{¹H} NMR, ¹³C{¹H} NMR and further confirmed by single crystal X-ray diffraction analysis. The molecular structures show that 2–5 contain a butterfly diiron toluenedithiolate cluster coordinated by five terminal carbonyls and an apical monophosphine.