The preparation and properties of cationic dicarbonylcyclopentadienyliron complexes of organic carbonyl compounds: molecular structure of dicarbonylcyclopentadienyliron(3-methylcyclohexenone) hexafluorophosphate

A number of complexes CpFe(CO)₂(L) (L = aldehyde, ketone, ester, amide) have been prepared either by treatment of [CpFe(CO)₂]₂ or CpFe(Co)₂Br with AgPF₆ in the presence of L or by a ligand exchange reaction employing CpFe(CO)₂(isobutylene)BF₄. NMR spectral data suggest that these complexes involve iron—oxygen σ-bonding rather than π-bonding to the carbonyl group. This is confirmed by an X-ray structure determination of the 3-methylcyclohexenone complex. The exchange stability of these complexes parallels their basicity.     

Synthesis and cleavage reactions of thiocarbonyl-bridged Cp2Fe2(CO)3CS,and preparation of the carbene complexes CpFe(CO)C(N2C2H6)SnPh3 and [CpFe(CO)2C(OMe)2]PF6

The thiocarbonyl-bridged complex Cp₂Fe₂(CO)₃CS is obtained by the reaction of CpFe(CO)₂^? and (PhO)₂CS in THF. Infrared and NMR spectra show that the compound exists in solution in interconverting cis and trans forms, but that the isomerization occurs more slowly than for the carbonyl analog [CpFe(CO)₂]₂. Most reagents which cleave [CpFe(CO)₂]₂, such as Br₂, HgCl₂, and O₂/HBF₄, do not give simple cleavage reactions with Cp₂Fe₂(CO)₃CS. Reductive cleavage of Cp₂Fe₂(CO)₃CS with Na(Hg) gives the thiocarbonyl anion CpFe(CO)(CS)^?, which reacts with Ph₃SnCl to form CpFe(CO)(CS)SnPh₃. Methylamine reacts with CpFe(CO)(CS)SnPh₃ to give CpFe(CO)(CNMe)SnPh₃, while ethylenediamine gives the carbene complexes CpFe(CO)C(N₂C₂H₆)SnPh₃. The preparation of another new carbene complex, [CpFe(CO)₂C(OMe)₂]PF₆, is also described.     

Mono- and bi-iron chalcogenocarboxylate complexes

A series of thiocarboxylato and selenocarboxylato monomeric CpFe(CO)₂ECORCOCl and dimeric [CpFe(CO)₂ECO]₂R iron complexes have been synthesized and characterized. The interaction of (μ-E_x)[CpFe(CO)₂]₂ (E = S; x = 2–4. E = Se; x = 1) with di-acid chlorides (ClCORCOCl) in a 1:1 molar ratio gave the monomeric complexes CpFe(CO)₂ECORCOCl for R = 1,3-C₆H₄, 2,6-C₅H₃N, 1,2-C₆H₄. However, the dimeric complexes [CpFe(CO)₂ECO]₂R were obtained from the same reactants in a 2:1 metal-to-ligand molar ratio in which R is 1,3-C₆H₄, 2,6-C₅H₃N or C₂H₄. The monomer versus dimer production mainly depends on the electronic and steric factors of the R-moiety. The new monomeric and dimeric thio- and selenocarboxylato iron complexes have been characterized by spectroscopic techniques (¹H- and ¹³C-NMR, IR) and by elemental analysis. The structures of [CpFe(CO)₂SCO]₂(1,3-C₆H₄) and its seleno analogue [CpFe(CO)₂SeCO]₂(1,3-C₆H₄) were determined by X-ray structure determination.     

Multifunctional iron thiocarboxylate complexes: synthesis,reactivity and structure of CpFe(CO)<Subscript>2</Subscript>SCO-3,5-C<Subscript>6</Subscript>H<Subscript>4</Subscript>(COCl)<Subscript>2</Subscript>

A controlled substitution reaction of the chlorine atoms of 1,3,5-benzenetricarbonyl trichloride by the organoiron fragment (CpFe(CO)₂S) has been achieved. The complexes CpFe(CO)₂SCO-3,5-C₆H₃(COCl)₂ (1), 1,3-[CpFe(CO)₂SCO]₂-5-C₆H₃COCl (2) and 1,3,5-[CpFe(CO)₂SCO]₃C₆H₃ (3) were prepared from the reaction of (μ-S _x )[CpFe(CO)₂]₂ (x = 3, 4) with 1,3,5-C₆H₃(COCl)₃ in a 1:1, 2:1, or 3:1 metal to ligand molar ratio. The reactions of (1) with amines, thiols, and carboxylic acids produce the trifunctional mono-iron complexes CpFe(CO)₂SCO-3,5-C₆H₃(COY)₂ [Y = NR₂ (4), SR (5), OCOR (4)]. The X-ray structure determination of (1) is reported.     

Austauschreaktionen an komplexgebundenen liganden von elementen der IV. Hauptgruppe : III. Darstellung von halogen-, pseudohalogen- und hydridokomplexen des typs π-C5H5Fe(CO)2SiX3

The complexes CpFe(CO)₂SiBr₃, CpFe(CO)₂SiI₃, CpFe(CO)₂SiBr₂(OMe), and CpFe(CO)₂SiI(NH-cyclo-C₆H₁₁)₂ are prepared by the reaction of CpFe(CO)₂SiR₃ (R = OMe, NH-cyclo-C₆H₁₁) with HBr, HI and CH₃I. Treating CpFe(CO)₂SiCl₃ with a large excess of NaN₃, KOCN or KSCN yields the first tri-pseudohalogensilyl—transition-metal-complexes. The compounds are characterized by IR and mass spectra. A new method of preparation of the already known complex CpFe(CO)₂SiH₃ is described starting from CpFe(CO)₂SiCl₃ and LiAlH₄.     

Synthesis and Reactivity of Mono‐, Di‐, and,Triiron Selenocarboxylate Complexes

Treatment of the iron selenide (μ‐Se)[CpFe(CO)₂]₂ with one equivalent of 1, 3, 5‐C₆H₃(COCl)₃ gave the organoiron selenocarboxylate complex CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COCl)₂ ( 1 ), which contains two free acid chloride groups. Complex 1 reacted with amines, thiols, and phenols to produce the corresponding amides CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CONR₂)₂ ( 2 ), thioesters CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COSR)₂( 3 ), and aromatic esters CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CO₂Ar)₂ ( 4 ), respectively. Complex 1 was converted into the diacid CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COOH)₂ ( 5 ) or the diamide CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CONH₂)₂ ( 6 ) complexes by reactions with NaOH or NaNH₂, respectively. The bis(seleno)‐1, 3‐(CpFe(CO)₂SeCO)₂‐5‐C₆H₃(COCl) ( 7 ) and tris(seleno)‐carboxylate 1, 3, 5‐(CpFe(CO)₂SeCO)₃C₆H₃ ( 8 ) complexes were also prepared by controlled reaction of 1, 3, 5‐C₆H₃(COCl)₃ with the iron selenide (μ‐Se)[CpFe(CO)₂]₂. Complexes 1 – 8 were characterized by spectroscopic techniques (IR, ¹H‐NMR) and by elemental analysis as well. The X‐ray structures of CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COCl)₂ ( 1 ) and CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COSCH₂Ph)₂ ( 3b ) were determined.     

[M(CO)2(NO)], a new core in bioorganometallic chemistry: model complexes of [Re(CO)2(NO)] and [Tc(CO)2(NO)]

In this study selected bidentate (L²) and tridentate (L³) ligands were coordinated to the Re(I) or Tc(I) core [M(CO)₂(NO)]²⁺ resulting in complexes of the general formula fac-[MX(L²)(CO)₂(NO)] and fac-[M(L³)(CO)₂(NO)] (M = Re or Tc; X = Br or Cl). The complexes were obtained directly from the reaction of [M(CO)₂(NO)]²⁺ with the ligand or indirectly by first reacting the ligand with [M(CO)₃]⁺ and subsequent nitrosylation with [NO][BF₄] or [NO][HSO₄]. Most of the reactions were performed with cold rhenium on a macroscopic level before the conditions were adapted to the n.c.a. level with technetium (^99mTc). Chloride, bromide and nitrate were used as monodentate ligands, picolinic acid (PIC) as a bidentate ligand and histidine (HIS), iminodiacetic acid (IDA) and nitrilotriacetic acid (NTA) as tridentate ligands. We synthesised and describe the dinuclear complex [ReCl(μ-Cl)(CO)₂(NO)]₂ and the mononuclear complexes [NEt₄][ReCl₃(CO)₂(NO)], [NEt₄][ReBr₃(CO)₂(NO)], [ReBr(PIC)(CO)₂(NO)], [NMe₄][Re(NO₃)₃(CO)₂(NO)], [Re(HIS)(CO)₂(NO)][BF₄], [⁹⁹Tc(HIS)(CO)₂(NO)][BF₄], [^99mTc(IDA)(CO)₂ (NO)] and [^99mTc(NTA)(CO)₂(NO)]. The chemical and physical characteristics of the Re and Tc-dicarbonyl-nitrosyl complexes differ significantly from those of the corresponding tricarbonyl compounds.     

Insertion of CS2 and CSe2 into metal—amido bonds. Mono- versus bi-dentate dithiocarbamates formed by reactions of CS2 + NHR2 with {CpMo(CO)n}2 (M  Fe, n  2; m  Mo, n  3)

The reaction of Cp₂Fe₂(CO)₄ with NHEt₂ and CS₂ gives the monodentate dithiocarbamate CpFe(CO)₂-η¹-SC(S)NEt₂ (Ia), whereas the same reaction with CP₂Mo₂(CO)₆ gives the chelate CPMo(CO)₂-η₂-S₂CNEt₂ (II). New complexes of amines CpFe(CO)₂(NHR₂)⁺PF₆- (III, R  Me, Et, SiMe₃) have been synthesized by treating CpFe(CO)₂Cl with NHR₂. They do not react with CS₂ and give only [CpFe(CO)₂]₂ upon refluxing with bases such as t-BuOK or NEt(i-Pr)₂, but concerted CS₂ insertion in the presence of a base immediately gives I at 20°C. This clean route is used to synthesize the monodentate diselenocarbamate CpFe(CO)₂-η¹-SeC(Se)NMe₂ (IV) by reaction of CSe₂ with III (R  Me) in the presence of t-BuOK. Whereas the known reaction of CpFe(CO)₂Cl with Na⁺S₂CNMe₂^? gives Ib (R  Me), the analogous reaction of C₅Me₅Me(CO)₂Br gives specifically the thermally stable chelate C₅Me₅Fe(CO)-η²-S₂CNMe₂ (Vb′).     

Substituted iron selenocarboxylate complexes CpFe(CO)(EPh3)SeCOR (E = P,As, Sb)

Photolytic substitutions of iron selenocarboxylate complexes CpFe(CO)₂SeCOR with triphenylphosphine, triphenylarsine or triphenylantimony (EPh₃) gave exclusively the monosubstituted complexes CpFe(CO)(EPh₃)SeCOR [R = 3,5-C₆H₃(NO₂)₂ (1), 4-C₆H₄NO₂ (2), Ph (3), 2-C₆H₄Me (4), and E = P (a), As (b), Sb (c)] in high yields.     

Hydrogen evolution catalyzed by {CpFe(CO)2}-based complexes

[CpFe^II(CO)₂(thf)](BF₄) may be considered as a bio-inspired model of hydrogenases. Its electrocatalytic properties for the reduction of trichloroacetic acid into dihydrogen are presented. A catalytic mechanism is proposed. This catalyst exhibits interesting properties, in particular low overvoltage (350 mV) for H₂ evolution, but it is inactivated through dimerization. Comparison with [CpFe(CO)₂]₂ is provided.     

Theoretical Study of the Solvent Effect on the Electronic and Vibrational Properties of [CpFe(CO)<Subscript>2</Subscript>(NCS)] and [CpFe(CO)<Subscript>2</Subscript>(SCN)] Linkage Isomers

The present study illustrates the stability of [CpFe(CO)₂(NCS)] and [CpFe(CO)₂(SCN)] linkage isomers by the use of MPW1PW91 quantum method in the gas and solution phases. Our results reveal that the [CpFe(CO)₂(NCS)] isomer is more stable than the [CpFe(CO)₂(SCN)] isomer. Based on the polarizable continuum model, the effect of the solvent polarity on the stability, structural parameters, frontier orbital energies, and vibrational modes of carbonyl ligands (ν_CO) of these linkage complexes is explored. The molecular orbital analysis suggests that the major contributions to HOMO and LUMO arise from the ambidentate ligand and Fe in two isomers, respectively. In addition, the bonding interaction between the CpFe(CO)₂ fragment and the ambidentate ligand is studied by means of the energy decomposition analysis. The back-bonding effect in Fe–CO bonds is revealed in the calculation of the quadrupole polarization of the carbon atom by the QTAIM analysis. The character of Fe–N and Fe–S bonds in these complexes is analyzed by the natural bond orbital analysis.     

The reaction of bis[tricarbonyl(triphenylphosphine)iridium],Ir2(CO)6(PPH3)2, with diazonium salts

The reaction of Ir₂(CO)₆(PPh₃)₂ with p-substituted aryldiazoniurn salts gives the o-metalated complexes [Ir(CO)₂(NHNC₆H₃R) (PPh₃)]₂²⁺ 2BF₄^?. These react with KOH in ethanol to give the deprotonated derivatives, and with halogens to give halogenated derivatives by cleavage of the carbonmetal bond.     

Ligand assisted homolytic cleavage of the Ru-Ru single bond in [Ru2(CO)4] core and the chemical consequence

The Ru-Ru single bond in [Ru₂(CO)₄(MeCN)₆][BF₄]₂ remains intact in the reaction with 2-i-propyl-1,8-naphthyridine (ⁱPrNP) and the isolated product is the cis-[Ru₂(ⁱPrNP)₂(CO)₄(OTf)₂] (1) obtained via crystallization in the presence of [n-Bu₄N][OTf]. The 2-t-butyl-1,8-naphthyridine (^tBuNP), on the contrary, leads to the oxidative cleavage of the Ru-Ru single bond resulting in the trans-[Ru(^tBuNP)₂(MeCN)₂][BF₄]₂[NC(Me)C(Me)N] (2). The anti-[NC(Me)C(Me)N]²⁻ is the product of the two-electron reductive coupling of two acetonitrile molecules. The phenoxo appendage in 2-(2-hydroxyphenyl)-1,8-naphthyridine (hpNP) brings the identical effect of the scission of the Ru-Ru bond but the process is non-oxidative and the product obtained is the cis-[Ru(hpNP)₂(CO)₂][BF₄] (3). The bis-(diphenylphosphino)methane (dppm) in dichloromethane oxidatively cleave the Ru-Ru bond leading to chloro bridged [Ru(μ-Cl)(dppm)(CO)(MeCN)]₂[BF₄]₂ (4). All the complexes have been characterized by the spectroscopic and electrochemical measurements and their structures have been established by X-ray diffraction study.     

Cr,Co, and Mn arene π-complexes based on diphenyl- and triphenylmethane

The interaction of Ph₂CH₂ and Ph₃CH with Cr(CO)₆, Co₂(CO)₈, and Mn(CO)₅BF₄ leads to mononuclear LCr(CO)₃, LCo₄(CO)₉, and [LMn(CO)₃]BF₄ π-arene complexes. Similarly, LCr(CO)₃Co₄(CO)₉ and [LCr(CO)₃Mn(CO)₃]BF₄ heteroaromatic derivatives are obtained from LCr(CO)₃ complexes, whereas LCo₄(CO)₉ complexes afford L[Co₄(CO)₉]₂ bicluster derivatives. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1809–1812, October, 1993.     

Coordination properties of N2S (1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane) or N2S2 (1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane or 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene) donor ligands toward Rh(I)

The 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane ligand (bdtp) reacts with [Rh(COD)(THF)₂][BF₄] to give [Rh(COD)(bdtp)][BF₄] ([1][BF₄]), which is fluxional in solution on the NMR time scale. Its further treatment with carbon monoxide leads to a displacement of the 1,5-cyclooctadiene ligand, generating a mixture of two complexes, namely, [Rh(CO)₂(bdtp)][BF₄] ([2][BF₄]) and [Rh(CO)(bdtp-κ³N,N,S)][BF₄] ([3][BF₄]). In solution, [2][BF₄] exists as a mixture of two isomers, [Rh(CO)₂(bdtp-κ²N,N)]⁺ ([2a]⁺) and [Rh(CO)₂(bdtp-κ³N,N,S)]⁺ ([2b]⁺; major isomer) rapidly interconverting on the NMR time scale. At room temperature, [2][BF₄] easily loses one molecule of carbon monoxide to give [3][BF₄]. The latter is prone to react with carbon monoxide to partially regenerate [2][BF₄]. The ligands 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene (bddf) and 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) are seen to react with two equivalents of [Rh(COD)(THF)₂][BF₄] to give the dinuclear complexes [Rh₂(bddf)(COD)₂][BF₄]₂ ([4][BF₄]₂) and [Rh₂(bddo)(COD)₂][BF₄]₂ ([5][BF₄]₂), respectively. In such complexes, the ligand acts as a double pincer holding two rhodium atoms through a chelation involving S and N donor atoms. Bubbling carbon monoxide into a solution of [4][BF₄]₂ results in loss of the COD ligand and carbonylation to give [Rh₂(bddf)(CO)₄][BF₄]₂ ([6][BF₄]₂). The single-crystal X-ray structures of [3][CF₃SO₃], [5][BF₄]₂ and [6][BF₄]₂ are reported.     

Heterocyclic thiocarboxylato complexes of iron: synthesis,characterization, electrochemistry,and reactions

Heterocyclic-thiocarboxylato complexes of iron, CpFe(CO)₂SCO-het (het?=?2-C₄H₃O, 2-C₄H₃S, CH₂-2-C₄H₃S), have been synthesized via the reaction of iron sulfides, (μ-S _x )[CpFe(CO)₂]₂ (x?=?3,?4), with heterocyclic acid chlorides het-COCl. Photolytic substitutions of these complexes CpFe(CO)₂SCO-het with triphenylphosphine, triethylphosphite, triphenylarsine, and triphenylantimony [ER₃ (E?=?P, R?=?Ph, OC₂H₅; E?=?As, Sb, R?=?Ph)] exclusively gave the monosubstituted complexes CpFe(CO)(ER₃)SCO-het in good yields. The new complexes have been characterized by elemental analysis, UV-Vis, IR, ¹H, and ³¹P NMR spectroscopies and by cyclic voltammetry for a representative family (1, 4a–d). The solid state structures of CpFe(CO)₂SCO(2-C₄H₃S) (2), CpFe(CO)(PPh₃)SCO(2-C₄H₃S) (5a), CpFe(CO)(AsPh₃)SCO(2-C₄H₃S) (5b), and CpFe(CO)(SbPh₃)SCO(2-C₄H₃S) (5c) were determined by X-ray crystal structure analysis.     

Potential inhibitors of DNA topoisomerase II: ruthenium(II) poly-pyridyl and pyridyl-azine complexes

In search of new DNA probes a series of new mono and binuclear cationic complexes [RuH(CO)(PPh₃)₂(L)]⁺ and [RuH(CO)(PPh₃)₂(-μ-L)RuH(CO)(PPh₃)₂]²⁺ [L=pyridine-2-carbaldehyde azine (paa), p-phenylene-bis(picoline)aldimine (pbp) and p-biphenylene-bis(picoline)aldimine (bbp)] have been synthesized. The reaction products were characterized by microanalyses, spectral (IR, UV-Vis, NMR and ESMS and FAB-MS) and electrochemical studies. Structure of the representative mononuclear complex [RuH(CO)(PPh₃)₂(paa)]BF₄ was crystallographically determined. The crystal packing in the complex [RuH(CO)(PPh₃)₂(paa)]BF₄ is stabilized by intermolecular π-π stacking resulting into a spiral network. Topoisomerase II inhibitory activity of the complexes and a few other related complexes [RuH(CO)(PPh₃)₂(L)]⁺ {L=2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) and 2,3-bis(2-pyridyl)-pyrazine (bppz)} have been examined against filarial parasite Setaria cervi. Absorption titration experiments provided good support for DNA interaction and binding constants have also been calculated which were found in the range 1.2 × 10³-4.01 × 10⁴ M⁻¹.     

Some chemical properties of (arene)nonacarbonyltetracobalt complexes and the preparation of (arene)octacarbonyltetracobalt trialkylphosphites

In reactions of Co₄(CO)₉(arene) with carbon monoxide, phosphines and acetylenes, displacement of the arene takes place and known derivatives of Co₄(CO)₁₂ and Co₂(CO)₈ are formed. With phosphites, however, displacement of one carbon monoxide can be achieved, to give Co₄(CO)₈(arene)P(OR)₃. The same type of complexes can also be prepared by treatment of Co₄(CO)₁₁P(OR)₃ with arenes.     

Efficient Direct Nitrosylation of α-Diimine Rhenium Tricarbonyl Complexes to Structurally Nearly Identical Higher Charge Congeners Activable towards Photo-CO Release

The reaction of rhenium α-diimine (N-N) tricarbonyl complexes with nitrosonium tetrafluoroborate yields the corresponding dicarbonyl-nitrosyl [Re(CO)₂(NO)(N-N)X]⁺ species (where X = halide). The complexes, accessible in a single step in good yield, are structurally nearly identical higher charge congeners of the tricarbonyl molecules. Substitution chemistry aimed at the realization of equivalent dicationic species (intended for applications as potential antimicrobial agents), revealed that the reactivity of metal ion in [Re(CO)₂(NO)(N-N)X]⁺ is that of a hard Re acid, probably due to the stronger π-acceptor properties of NO⁺ as compared to those of CO. The metal ion thus shows great affinity for π-basic ligands, which are consequently difficult to replace by, e.g., σ-donor or weak π-acids like pyridine. Attempts of direct nitrosylation of α-diimine fac-[Re(CO)₃]⁺ complexes bearing π-basic OR-type ligands gave the [Re(CO)₂(NO)(N-N)(BF₄)][BF₄] salt as the only product in good yield, featuring a stable Re-FBF₃ bond. The solid state crystal structure of nearly all molecules presented could be elucidated. A fundamental consequence of the chemistry of [Re(CO)₂(NO)(N-N)X]⁺ complexes, it that the same can be photo-activated towards CO release and represent an entirely new class of photoCORMs.     

Synthesis and X-ray investigation of novel Fe and Mn phenyltellurenyl-halide complexes: (CO)3FeBr2(PhTeBr), (η-C5H5)Fe(CO)2(PhTeI2) and CpMn(CO)2(PhTeI)

New complexes of transition metals with organotellurium halide ligands are reported. Iodination of [CpMn(CO)₂]₂(μ-Ph₂Te₂) leads to the Te-Te bond cleavage and formation of CpMn(CO)₂(PhTeI). Oxidative addition of PhTeBr₃ to Fe(CO)₅ gives the monomeric complex (CO)₃FeBr₂(PhTeBr) which is isostructural with the recently reported (CO)₃FeI₂(PhTeI). Insertion of phenyltellurenyl iodide (PhTeI) into the Fe-I bond of CpFe(CO)₂I forms CpFe(CO)₂(TeI₂Ph). Molecular structures of the reported complexes were determined by single-crystal X-ray diffraction analysis (XRD). A considerable shortening of metal-tellurium distances is observed.