Iron Dicarbonyl Research Articles

Iron‐Catalyzed Oppenauer‐Type Oxidation of Alcohols

AbstractA (hydroxycyclopentadienyl)iron dicarbonyl hydride catalyzes the Oppenauer‐type oxidation of alcohols with acetone as the hydrogen acceptor. Many functional groups are tolerant to the oxidation conditions. The same complex also catalyzes the dehydrogenation of diols to lactones. A mechanism involving the formation of iron‐alcohol complexes and their rapid ligand exchange with free alcohols is proposed. The trimethylsilyl groups on the cyclopentadienyl ligand of the catalyst play a critical role in stabilizing the iron hydride and increasing the catalyst lifetime.

Combination of transition metal carbonyls and silanes: New photoinitiating systems

AbstractThe recently developed silyl radical chemistry is used in combination with transition metal carbonyls MC (dimanganese(0) decacarbonyl; dirhenium decacarbonyl; cyclopentadienyl iron(II) dicarbonyl dimer) for both free radical promoted cationic photopolymerization (FRPCP) and free radical photopolymerization (FRP). The newly developed photoinitiating systems (MC/silane and MC/silane/iodonium salt) are highly efficient under air. Photopolymerization profiles obtained upon a visible light irradiation delivered by a xenon lamp show that high conversion can be easily achieved after a 400 s exposure. Sunlight irradiations under air can also lead to tack free coatings. The processes associated with the metal carbonyl radical/silane interactions are investigated by Laser Flash Photolysis (LFP) and ESR‐Spin Trapping (ESR‐ST) experiments. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1830–1837, 2010

Bond Activation in Iron(II) and Nickel(II) Complexes of Polypodal Phosphanes

A pyridine-derived tetraphosphane ligand (donor set: NP4) has been found to undergo remarkably specific C-P bond cleavage reactions, thereby producing a ligand with an NP3 donor set. The reaction may be reversed under suitable conditions, with regeneration of the original NP4 ligand. In order to investigate the mechanism of this reaction, the NP3 donor ligand C5H3N[CMe(CH2PMe2)2][CMe2(CH2PMe2)] (11) was prepared, and its iron(II) complex 4 generated from Fe(BF4)2 ・6H2O, with methyl diethylphosphinite (7) as an additional monodentate ligand. Ligand 11 has, in addition to the NP3 donor set, one methyl group in close contact with the iron center, reminiscent of an agostic M・ ・ ・H-C interaction. Depending on the stoichiometric amount of iron(II) salt, a side product 15 is formed, which has a diethylphosphane ligand instead of the phosphinite 7 coordinated to iron(II). While attempts to deprotonate the metal-coordinated methyl group in 4 were unsuccessful, the reaction was shown to occur in an alternative complex (18), which is similar to 4 but has a trimethylphosphane ligand instead of the phosphinite 7. The reaction of complex 15 with CO gave two different products, which were both characterized by single-crystal X-ray diffraction. One (19) is the dicarbonyl iron(II) complex of the triphosphane ligand 11, the other (3) is the carbonyl iron(II) complex of the tetraphosphane C5H3N[CMe(CH2PMe2)2]2 (1). This suggests an intermolecular mechanism for the C-P bond formation in question.

Analysis of a Pentacoordinate Iron Dicarbonyl as Synthetic Analogue of the Hmd or Mono‐Iron Hydrogenase Active Site

Pentacoordinate iron dicarbonyls, (NS)Fe(CO)(2)P (NS=2-amidothiophenylate, P=PCy(3) (4), PPh(3), (5), and P(OEt)(3) (6)) were prepared as potential biomimetics of the active site of the mono-iron hydrogenase, [Fe]-H(2)ase. Full characterization including X-ray diffraction, density functional theory (DFT) computations, and Mössbauer studies for complexes 5 and 6 find that, despite similar infrared v(CO) pattern and absorption frequencies as the active site of the [Fe]-H(2)ase, the geometrical distortions towards trigonal bipyramidal, the negative isomer shift parameters, and the differences in CO-uptake reactivity are due to the "non-innocence" of the NS ligand. Ligand-based protonation with a strong acid, HBF(4).Et(2)O, interrupted the extensive pi-delocalization over Fe and NS ligand of complex 4 and switched on CO uptake (1 bar) to form a CO adduct, mer-[(H-NS)Fe(CO)(3)(PCy(3))](+) or 4(CO)-H(+). The extrinsic CO is reversibly removed on deprotonation with Et(3)N to regenerate complex 4. In a (13)CO atmosphere, concomitant CO uptake by 4-H(+) and exchange with intrinsic CO groups provide a facile route to (13)C-labeled 4(CO)-H(+) and, upon deprotonation, (13)C-labeled complex 4. DFT calculations show substantial Fe character in the LUMO of 4-H(+) typical of the d(6) Fe(II) in a regular square-pyramidal geometry. Thus, the Lewis acidity of 4-H(+) makes it amenable for CO binding, whereas the dianionic NS ligand renders the iron center of 4 insufficiently electrophilic and largely of Fe(I) character.

Electrochemical Generation of Fp-Silanes

Electrolysis of Fp2 (cyclopentadienyl iron(II) dicarbonyl dimer) in the presence of different chlorosilanes led to the formation of substances of the type FpSiR3 (R = H, Me, Ph) containing iron-silicon bonds. These compounds could be isolated and crystallized. Due to this success the reaction was also performed in the presence of germanium and tin chlorides.

Enantiopure Pyridine Bis(oxazoline) “Pybox” and Bis(oxazoline) “Box” Iron Dialkyl Complexes: Comparison to Bis(imino)pyridine Compounds and Application to Catalytic Hydrosilylation of Ketones

The chemistry of enantiopure pyridine bis(oxazoline) iron compounds has been explored. The electronic properties of this ligand class have been evaluated relative to aryl- and alkyl-substituted bis(imino)pyridines using cyclic voltammetry and CO stretching frequencies of iron dicarbonyl compounds. Attempts to prepare a pyridine bis(oxazoline) iron dinitrogen complex by sodium amalgam reduction of the corresponding dichloride precursor yielded a catalytically inactive S = 1 bis(chelate) iron complex. Dialkyl derivatives of the general formula (RPybox)Fe(CH2SiMe3)2 were prepared either by pyridine displacement from (py)2Fe(CH2SiMe3)2 or by direct dialkylation of the appropriate iron dichloride. Two examples of the S = 2 complexes were characterized by single-crystal X-ray diffraction. Each enantiopure Pybox iron dialkyl was evaluated in the catalytic hydrosilylation of various ketones. Efficient turnover was observed at 23 °C with 0.3% of the iron precatalyst using PhSiH3 as the stoichiometric reductant. Fo...

Multi-Walled Carbon Nanotube Paper Anodes for Lithium Ion Batteries

The lithium ion capacity has been measured for multi-walled carbon nanotubes (MWCNTs) synthesized by injection chemical vapor deposition (CVD) using a cyclopentadienyl iron dicarbonyl dimer catalyst. The high quality of the as-synthesized MWCNTs has enabled free-standing electrodes to be fabricated independent of polymeric binder or copper support. Galvanostatic cycling of these electrodes demonstrates excellent reversibility and coulombic efficiency (> 97% after cycle 3) using propylene carbonate based electrolytes, with no evidence for material degradation. A reversible capacity exceeding 225 mAh/g was measured after 20 cycles when using the electrolyte combination of (1:1:1 v/v) ethylene carbonate (EC):propylene carbonate (PC):diethyl carbonate (DEC) at a constant current of 74 mA/g (equivalent of C/5 for LiC6). Modification of the catalyst solvent during synthesis from xylenes to pyridine improved the lithium ion capacity in the resulting MWCNT paper to 340 mAh/g. In addition, this MWCNT paper showed a stable reversible capacity after 10 cycles, exceeding 225 mAh/g when cycled at an equivalent 1C rate. Therefore, the use of a nitrogen source during synthesis can lead to improved lithium ion capacity in novel MWCNT anodes.

Reduction of CO2 to CO Using Low-Coordinate Iron: Formation of a Four-Coordinate Iron Dicarbonyl Complex and a Bridging Carbonate Complex

A reduced diiron(I) complex reacts with CO(2) to give two iron-containing products. One product has a carbonate bridge, which isomerizes rapidly at -70 degrees C and may be derived from an oxodiiron intermediate. The formation of this product releases free CO, which leads to a four-coordinate iron dicarbonyl complex. This product is the first crystallographically characterized example of a four-coordinate iron dicarbonyl species, a moiety that may be present in the active site of Hmd ("iron-sulfur cluster free") hydrogenase.

Catalytic Conversion of Isocyanates to Carbodiimides by Cyclopentadienyl Manganese Tricarbonyl and Cyclopentadienyl Iron Dicarbonyl Dimer.

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Design of a New Multifunctionalized PAMAM Dendrimer with Hydrazide-Terminated Spacer Arm Suitable for Metal−Carbonyl Multilabeling of Aldehyde-Containing Molecules

We describe herein the synthesis of generation 4 (G4) poly(amidoamine) (PAMAM) dendrimers bearing (1) a nitroaniline derivative as an NMR probe, (2) (η5-cyclopentadienyl)iron dicarbonyl succinimidato complexes as infrared probes for carbonyl metallo immunoassay, (3) acetamide groups for increased solubility, and (4) hydrazide functions at the extremity of five-carbon atom spacer arms for the labeling of aldehyde-containing molecules. The step-by-step building of these multifunctionalized dendrimers was monitored by 1H NMR spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Substitution of terminal amine groups of PAMAM dendrimers with appropriate functional groups provides complex dendrimeric structures with a wide range of applications. The final goal of this study is the development of new reagents suitable for the metal−carbonyl multilabeling of immunological reagents such as antibodies.

Catalytic conversion of isocyanates to carbodiimides by cyclopentadienyl manganese tricarbonyl and cyclopentadienyl iron dicarbonyl dimer

Isocyanates are catalytically converted to the corresponding carbodiimides in the presence of low valent transition metal complexes. The best conversions and yields were accomplished using [(C 5R 5)Fe(CO) 2] 2 (R = H or Me) or MeCpMn(CO) 3 as catalysts.

Adducts of NaOSiMePh2 Oligomers with THF and Cyclopentadienyl Iron Dicarbonyl Dimer

AbstractThe sodium siloxide NaOSiMePh2 is accessible from the reaction of Ph2MeSiOH with sodium. The crystal structures of three hexameric double heterocubane compounds containing NaOSiMePh2, one without additional donors and one each supported by THF and [CpFe(CO)2]2 are described. Using an excess of THF results in the formation of tetrameric sodium siloxide NaOSiMePh2. The structures of (NaOSiMePh2)4·(THF)4 (Aba2) and (NaOSiMePh2)4·2[CpFe(CO)2]2 (I41/acd) feature a heterocubane structure.

Investigation of the Reaction of Allyl(cyclopentadienyl)iron(II) Dicarbonyl with Iminium Salts: Synthesis of Ammonium Salts of Substituted Five-Membered-Ring Iron Complexes

Series of quaternary ammonium salts of substituted five-membered-ring iron complexes were prepared by reaction of allyl(cyclopentadienyl)iron(II) dicarbonyl with iminium salts. Also, reactions of allyl(cyclopentadienyl)iron(II) dicarbonyl with in situ prepared iminium salts afford the same products in good to excellent isolated yields.

Functionalization of linear and cyclic siloxanes and a dendritic carbosilane with (η 5-C 5H 5)Fe(CO) 2Si(CH 3) 2CH [dbnd]CH 2 via hydrosilylation reaction

A series of multimetallic systems containing silicon-linked cyclopentadienyl dicarbonyl iron moieties including carbosilane dendrimers and cyclic and polymeric siloxanes have been prepared using hydrosilylation reactions. For this purpose the vinyl-substituted silyliron complex (η 5-C 5H 5)Fe(CO) 2Si(CH 3) 2 CH CH 2 ( 1) was prepared by salt elimination reaction between Na[(η 5-C 5H 5)Fe(CO) 2] and ClSi(CH 3) 2CH CH 2 and fully characterized. Hydrosilylation reaction of 1 with the appropriate Si–H functionalized molecules in the presence of Karstedt catalyst afforded the novel silyl carbonyl iron-functionalized cyclotetrasiloxane 2, dendrimer 3 and copolymer 4, in which the organometallic units are attached to the silicon-based frameworks through a two-methylene flexible spacer. The electrochemical behaviour of compounds 1– 4 has been examined in dichloromethane, tetrahydrofuran and acetonitrile solutions using cyclic voltammetry.

A Novel Iodine-bridged Piano-stool Iron Complex: Crystal Structure and Electronic State

Abstract The iodine-bridged iodo(pentamethylcyclopentadienyl)iron dicarbonyl complex, [(η5-C5Me5)Fe(CO)2I–I]2 (1) has been synthesized and characterized by single crystal X-ray diffraction method, IR spectroscopy, and 57Fe Mössbauer spectroscopy.

Iron(0) and ruthenium(0) complexes with tridentate phosphonite ligands and their potential for ketene formation from methyl iodide, CO and a base

An efficient route to the novel tridentate phosphine ligands RP[CH 2CH 2CH 2P(OR′) 2] 2 ( I: R = Ph; R′ = i-Pr; II: R = Cy; R′ = i-Pr; III: R = Ph; R′ = Me and IV: R = Cy; R′ = Me) has been developed. The corresponding ruthenium and iron dicarbonyl complexes M(triphos)(CO) 2 ( 1: M = Ru; triphos = I; 2: M = Ru; triphos = II; 3: M = Ru; triphos = III; 4: M = Ru; triphos = IV; 5: M = Fe; triphos = I; 6: M = Fe; triphos = II; 7: M = Fe; triphos = III and 8: M = Fe; triphos = IV) have been prepared and fully characterized. The structures of 1, 3 and 5 have been established by X-ray diffraction studies. The oxidative addition of MeI to 1– 8 produces a mixture of the corresponding isomeric octahedral cationic complexes mer, trans-( 13a– 20a) and mer, cis-[M(Me)(triphos)(CO) 2]I ( 13b– 20b) (M = Ru, Fe; triphos = I– IV). The structures of 13a and 20a (as the tetraphenylborate salt ( 21)) have been verified by X-ray diffraction studies. The oxidative addition of other alkyl iodides (EtI, i-PrI and n-PrI) to 1– 8 did not afford the corresponding alkyl metal complexes and rather the cationic octahedral iodo complexes mer, cis-[M(I)(triphos)(CO) 2]I ( 22– 29) (M = Ru, Fe; triphos = I– IV) were produced. Complexes 22– 29 could also be obtained by the addition of a stoichiometric amount of I 2 to 1– 8. The structure of 22 has been verified by an X-ray diffraction study. Reaction of 13a/ b– 20a/ b with CO afforded the acetyl complexes mer, trans-[M(COMe)(triphos)(CO) 2]I, 30– 37, respectively (M = Ru, Fe; triphos = I– IV). The ruthenium acetyl complexes 30– 33 reacted slowly with 2- tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) even in boiling acetonitrile. Under the same conditions, the deprotonation reactions of the iron acetyl complexes 34– 37 were completed within 24–40 h to afford the corresponding zero valent complexes 5– 8. It was not possible to observe the intermediate ketene complexes. Tracing of the released ketene was attempted by deprotonation studies on the labelled species mer, trans-[Fe(COCD 3)(triphos)(CO) 2]I ( 38) and mer, trans-[Fe( 13COMe)(triphos)(CO) 2]I ( 39).

Synthesis of metal-carbonyl-dendrimer-antibody immunoconjugates: towards a new format for carbonyl metallo immunoassay.

We report the preparation of metal-carbonyl-dendrimer-antibody conjugates. These metal-carbonyl-multilabeled antibodies are designed to be used in a new solid-phase-format carbonyl metallo immunoassay (CMIA). A fourth-generation polyamidoamine dendrimer was labeled with 10-25 (eta5-cyclopentadienyl)iron dicarbonyl (eta1-N-succinimidyl) entities. An antibody was chemically modified at its carbohydrate chains by a site-directed process used to preserve the antigen-antibody binding site. The antibody was then coupled with the dendrimer labeled with 10 metal carbonyl groups. An average of 1.4 labeled dendrimers were grafted per antibody molecule. These metal-carbonyl-dendrimer-antibody conjugates were used as new universal detection reagents that recognize their specific antigens. The antigens were spotted onto nitrocellulose membranes and detected by using the conjugates in combination with Fourier transform infrared spectroscopy. A detection level in the range 5-200 pmol per membrane was achieved. This approach opens the way to a new CMIA format.

Oxidative addition capability of triphosphine iron and ruthenium complexes with methyl iodide

The ruthenium and iron dicarbonyl complexes Ru(MeP(CH 2CH 2PMe 2) 2)(CO) 2 ( 1), Ru(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2 ( 2) and Fe(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2 ( 3) bearing strong donor tridentate phosphine ligands were prepared and fully characterised. The structures of the complexes have been established by X-ray diffraction studies. Oxidative addition of MeI to 1– 3 proceeds instantaneously at room temperature and affords the corresponding octahedral cationic complexes fac, cis-[RuMe(MeP(CH 2CH 2PMe 2) 2)(CO) 2]I ( 5a) and mer, cis-[RuMe(MeP(CH 2CH 2PMe 2) 2)(CO) 2]I ( 5b), mer, trans-[MMe(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2]I ( 6a (M=Ru); 7a (M=Fe)) and mer, cis-[MMe(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2]I ( 6b (M=Ru); 7b (M=Fe)), respectively. The triphosphine preferentially adopts a facial arrangement in the case of the ethylene bridged tridentate ligand ( 5a) and a meridional arrangement in the case of the trimethylene bridged ligand ( 6a– 7b). mer, cis-[RuMe(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2]I ( 6a) undergoes CO insertion to the acetyl complex mer, trans-[Ru(COMe)(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2]I ( 8). Attempts to produce a ketene complex from the deprotonation of 8 were not successful. The acetyl protons in 8 show very low acidity and no reaction occurred when the complex was reacted with bases such as DBU, BEMP (2-tert-Butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorine) or LDA.

Electronic Control of the Asymmetry in Heteroatom Monosubstituted Olefin Bonding to the Cyclopentadienyl Iron(II) Dicarbonyl Cation. A Hammett Correlation Study

Nucleophilic substitution of CpFe(CO)2(η2-H2CC(H)OEt)+PF6- with para-substituted anilines was used to prepare a series (4−10) of η2-vinyl aniline Fp+ complexes of the general formula CpFe(CO)2[η2-CH2C(H)NH(p-C6H4X)]+PF6-, where X = OMe (4), Me (5), H, (6), Br (7), COMe (8), CN (9), and NO2 (10). Correlation of the Hammett σ para parameters with the 13C NMR shifts of the metal-coordinated vinyl carbons demonstrated the ability to control the position of the Fp+ moiety along the olefin face. As the electron-donating character of the para substituent was increased, the Fp+ moiety was displaced away from the nitrogen-bearing carbon, increasing the asymmetry of the metal−olefin bonding. These conclusions were further supported by determining the X-ray crystal structure of the p-Me (5) and the p-acetyl (8) derivatives.

Characterization of intrazeolitic Fe 3+ prepared by chemical vapor deposition of [(C 5H 5)Fe(CO) 2] 2 inside NaY and FSM-16 zeolites and their catalytic activities towards phenol hydroxylation

Iron-modified mesoporous and microporous zeolite materials, namely FSM-16 and NaY as well as dealuminated NaY (del-NaY), were prepared using cyclopentadienyl iron dicarbonyl diamer [(C 5H 5)Fe(CO) 2] 2 via a chemical vapor deposition (CVD) technique. XRD, FTIR, TG/DSC, N 2 adsorption and Mössbauer measurements were used to characterize the various materials. An isomorphous substitution of Fe 3+ into the framework of NaY zeolite was accomplished as determined from the Mössbauer results (IS≤0.3) as well as from the increase in the unit cell volume. As a further confirmation, some framework IR bands (780 and 574 cm −1) showed a shift towards lower frequencies upon iron incorporation along with the existence of a band at 686 cm −1 ascribed to SiOFe linkages. The latter band was emphasized on the basis of comparison of NaY before and after the CVD treatment with the precursor of the Fe complex. Two types of octahedral Fe 3+ components were revealed in FSM-16 and del-NaY samples specified as intrazeolitic iron oxide clusters and α-Fe 2O 3 species, which were localized on the external surfaces of zeolites and occupied small percentages (18–22%) compared with the former species. The surface area of the support NaY was preserved after the CVD treatment rather than FSM-16 that showed a reduction (24%). The catalytic activities of various samples for the liquid phase hydroxylation of phenol using H 2O 2 were found to be in the order: Fe/NaY>Fe/FSM-16>Fe/del-NaY. The higher activity of the Fe/NaY sample was attributed to the high dispersity of Fe ions that are located in framework positions and to the high crystallinity.