Complexes CpFe Research Articles

Intermolecular hydrogen-bonding in the solid-state structure of CpFe(CN) 2(PTAH) : Structural and spectral comparisons with its [K][CpFe(CN) 2PTA] salt

The salt K[CpFe(CN) 2PTA] ( 1) has been synthesized from the photolysis of K[CpFe(CN) 2CO] and 1,3,5-triaza-7-phosphaadamantane (PTA) in methanol. Protonation of the salt by hydrogen ion exchange employing DOWEX 50 WX8-100 ion exchange resin yielded the complex CpFe(CN) 2PTAH ( 2). The solid-state structures of both compounds have been determined by X-ray crystallography. Protonation was shown via ν(CN) and 31P-NMR to occur at one of the PTA nitrogens. Furthermore, it was found in the solid-state of the protonated structure that intermolecular hydrogen-bonding occurs between the cyanide nitrogen of one molecule and the PTA nitrogen of another molecule. The average FeC CN distance for 1 is 1.877(11) Å. FeC CN distances for complex 2 differ significantly at 1.839(12) and 1.940(12) Å, with the shorter bond length associated with the hydrogen-bonded CN group. Spectral ( ν(CN) and 31P-NMR) characterization of the complexes and their potential use as precursors to double metal cyanide derivatives are reported.

Preparation and organic transformation reactions of CpFe(CO) 2SCO3-C 6H 4SO 2Cl

Treatment of the iron sulfides (μ-S x )[CpFe(CO) 2] 2 with 3-ClCOC 6H 4SO 2Cl gave the novel organoiron thiocarboxylate complex CpFe(CO) 2SCO3-C 6H 4SO 2Cl which contains a free sulfonyl chloride group. This complex reacts with nucleophiles such as R 2NH, ArOH and RSH to give stable complexes CpFe(CO) 2SCO3-C 6H 4SO 2NR 2, CpFe(CO) 2SCO3-C 6H 4SO 2OAr, and CpFe(CO) 2SCO3-C 6H 4SO 2SR, respectively. The crystal structure of CpFe(CO) 2SCO3-C 6H 4SO 2N(CH 3)CH 2Ph has been determined: space group: P2 1/ c, a=17.9594(5), b=9.2395(2), c=13.4341(4) Å, β=95.403(2)°, V=2219.26(10) Å 3 and Z=4.

The first selenosulfonate complexes CpFe(CO) 2SeSO 2R: preparation and structure of CpFe(CO) 2SeSO 2C 6H 5

Treatment of the iron selenide (μ-Se)[CpFe(CO) 2] 2 with sulfonyl chlorides RSO 2Cl (R=C 6H 5 ( 1), 4-C 6H 4Cl ( 2), 4-C 6H 4Br ( 3), 4-C 6H 4 t Bu ( 4), 4-C 6H 4Me ( 5), CH 3 ( 6)) gave the novel iron selenosulfonato complexes CpFe(CO) 2SeSO 2R in good yields. The crystal structure for 1 was determined.

The synthesis and structure of the thiosulfonato iron complexes CpFe(CO) 2SS(O) 2R

Treatment of the iron polysulfanes (μ-S x )[CpFe(CO) 2] 2 ( x=3, 4) with sulfonyl chlorides RSO 2Cl (R=CF 3 ( 1), CCl 3 ( 2), C 6F 5 ( 3)) gave the corresponding iron thiosulfonato complexes CpFe(CO) 2SS(O) 2R in good yields. Crystal structure for 2: P 21/ c, a=6.704(2), b=8.933(2), c=22.603(5) Å, α=90, β=92.82(2), γ=90°, V=1352.0(6) Å 3 and Z=4.

Theoretical Studies of Inorganic and Organometallic Reaction Mechanisms. 16. Oxidative Promotion of the Migratory Insertion of Carbon Monoxide in Cyclopentadienylmethyldicarbonyliron (II)

Density functional methodology has been used to study the mechanistic details of the migratory insertion of CO into the transition metal−alkyl σ bond of the Fe cyclopentadienyl complexes CpFe(CO)2CH3 and [CpFe(CO)2CH3]+ in the presence of phosphine, PH3. Geometries, energies, and vibrational frequencies of reactants, molecular complexes, transition states, intermediates, and products are determined. Methyl migration with little PH3 participation is the rate-determining step for both the neutral system and the cation system. Addition of PH3 stabilizes the metastable intermediates [CpFe(CO)(COCH3)- -PH3]0/+ and the products [CpFe(CO)(COCH3)(PH3)]0/+. The calculated activation energies of the rate-determining steps are 17.8 and 7.5 kcal/mol for the neutral and cation reaction, respectively. The significant difference in these barriers is not due to the oxidatively promoted reaction utilizing a significantly different mechanism, but is interpreted in terms of methyl migration in the cation as having more radi...

Multiple ligand transfer to planar-chiral cyclopentadienylruthenium complexes inducing metal-centered chirality

Multiple ligand transfer reaction between planar-chiral cyclopentadienylruthenium complexes [Cp′Ru(AN)3][PF6] [(Cp′ = 1-(CO2Et)-2-Me-4-RC5H2, R = Me, Ph, But, AN = acetonitrile] and iron complexes CpFe(CO)(L)X (L = PMe3, PPh3; X = I, Br) results in formation of metal-centered chiral ruthenium complexes Cp′Ru(CO)(L)X with a diastereoselectivity (de) up to 68%.

Linking of metal centres through boryl ligands: synthesis, spectroscopic and structural characterisation of a symmetrically bridged boryl complex CpFe(CO)2BO2C6H2O2BFe(CO)2Cp

The synthesis, spectroscopic and structural characterisation of the symmetrically bridged boryl complex CpFe(CO)2- BO2C6H2O2BFe(CO)2Cp are reported, together with analysis of the bonding by structural and DFT methods.

Imide and anhydride bridged organoiron dinuclear homo and hetero dichalcogeno carboxylate complexes [CpFe(CO)2ECO(C6H4)CO]2NH and [CpFe(CO)2ECO(C6H4)CO]2O; E = S, Se

Organoiron thio- and seleno-terephthaloyl chloride complexes CpFe(CO)2ECO(C6H4)COCl (E = S and Se) react with NaOH and NaNH2 to give quantitative yields of the acid Cp(CO)2ECO(C6H4)CO2H and the amide CpFe(CO)2ECO(C6H4)CONH2 respectively. These amide and acid derivatives react with the terephthaloyl chloride complexes to give a new series of imide-bridged [CpFe(CO)2ECO(C6H4)CO]2NH and anhydride-bridged [CpFe(CO)2ECO(C6H4)CO]2O organoiron dinuclear homo and hetero dichalcogeno terephthalate complexes. The complexes were characterized by elemental analysis, i.r. and 1H-n.m.r. spectra.

Metallocene Complexes of Iron and Cobalt Derived from the 4,4‘-Bis(η5-cyclopentadienyl)octafluorobiphenyl Ligand1

The reaction of decafluorobiphenyl with 10 equiv of sodium cyclopentadienide (NaCp) in THF (65 °C, 2 h) afforded 4,4‘-bis(cyclopentadienyl)octafluorobiphenyl (1) as a mixture of double-bond isomers in 72% yield after workup and purification. Subsequent treatment with sodium hydride in THF (25 °C, 6 h) afforded disodium 4,4‘-bis(cyclopentadienyl)octafluorobiphenyl (2). Reaction of NaCp, ligand 2, and FeBr2 (21:1:10 mol ratio) in THF afforded mostly ferrocene as well as the diiron complex CpFe(η5-C5H4-4,4‘-C6F4C6F4-η5-C5H4)FeCp (3), the linear triiron complex Cp[Fe(η5-C5H4-4,4‘-C6F4C6F4-η5-C5H4)]2FeCp (4), and the linear tetrairon complex Cp[Fe(η5-C5H4-4,4‘-C6F4C6F4-η5-C5H4)]3FeCp (5), which were isolated by liquid chromatography. Solution voltammetric analysis of 3 showed a single, reversible two-electron oxidation at +200 mV, 4 showed two reversible oxidations (2:1 ratio) at +180 and +372 mV, respectively, and 5 showed two reversible oxidations (2:2 ratio) at +192 and +382 mV, respectively (all vs Cp2Fe|Cp2Fe+). A similar reaction of NaCp, ligand 2, and CoBr2 in THF was worked up with air and dilute aqueous HCl followed by aqueous KPF6 to afford a mixture of cobaltocenium hexafluorophosphates, from which [Cp2Co]+PF6- and the dicobalt complex [CpCo(η5-C5H4-4,4‘-C6F4C6F4-η5-C5H4)CoCp]2+[PF6-]2 (6) were isolated by liquid chromatography. CV analysis of 6 showed a single, reversible CoII|CoIII wave at +232 mV relative to Cp2Co|Cp2Co+. These voltammetric data suggest that no significant electronic communication exists between two metals bridged by this conjugated dibasic ligand (2). A crystal structure of diiron complex 3 demonstrated the conformational preferences of the CpC6F4C6F4Cp ligand in the solid state with respective torsional angles of 37.5°, 50.1°, and 32.1°.

Synthesis of CpFe(CO)(L) complexes of hydantoin anions (Cp = eta5-C5H5, L = CO, PPh3), and the use of the 5,5-diphenylhydantoin anion complexes as tracers in the nonisotopic immunoassay CMIA of this antiepileptic drug.

As part of our ongoing development of the CMIA nonisotopic immunoassay method, in which the tracers are metal carbonyl complexes and detection is by Fourier transform infrared spectroscopy, we examined the potential use as tracers of the complexes CpFe(CO)2(5,5-diphenylhydantoin) 2d and CpFe(CO)(PPh3)(5, 5-diphenylhydantoin) 3. The present study involved the synthesis of a series of hydantoin complexes (2a-2d), in particular that of the derivative of 5,5-diphenylhydantoin 2d. The structure of 2d was confirmed by X-ray crystallography. The infrared analysis, establishing the position and intensity of the characteristic metal-carbonyl peaks of complexes 2d and 3 in the 1850-2200 cm-1 region, shows that measurement of the absorbance values of these characteristic peaks will permit quantitative analysis in the picomole range, the norm for routine use in immunoassay and thus suitable for use as CMIA tracers. Cross-reaction rates of these tracers with anti-DPH specific antibodies show that 2d and 3 are both recognized by anti-DPH antibodies (cross-reaction rates 43 and 20%, respectively). In developing a CMIA of DPH with these tracers, it was found that 3, with a single, intense band at 1977 cm-1, had very promising IR characteristics for use in multiassay CMIA, but probably owing to its relatively weak affinity for the antibodies, it was not possible to develop a CMIA for DPH using this tracer. Complex 2d, however, showed better recognition by the antibodies, and using this complex as a tracer, it was possible to develop a particularly sensitive monoassay of DPH by the CMIA method.

Formation of Acyliron Complexes CpFe(CO){P(OR′)3}COR′ by Reaction of Silyliron Complexes CpFe(CO)2SiR3 with Alkylphosphites P(OR′)3

Abstract Heating a toluene solution of CpFe(CO)2SiR3 (R3 = HMe2, HEt2, and FMe2) and excess P(OR′)3 (R′ = Me, Et, and Me-d3) at 80 °C resulted in the formation of an acyliron complex CpFe(CO){P(OR′)3}COR′ in 25–40% yield: Hence the alkyl group of phosphite is transferred to the carbon of a carbonyl ligand to give an acyl ligand during the reaction.

Synthesis and Properties of Intramolecularly Base-Stabilized (Disilanyl−silylene)ruthenium and -iron Complexes

Photolysis of the 3-methoxytrisilanyl complex CpM(CO)2SiMe2SiMe2SiMe2OMe (1a, M = Ru; 1b, M = Fe) afforded the intramolecularly methoxy-stabilized disilanyl−silylene complex Cp(OC)M{SiMe2←O(Me)SiMe2SiMe2} (2a, M = Ru; 2b, M = Fe) as a primary product. Prolonged irradiation of the solution resulted in the decay of 2a,b with release of a dimethylsilylene moiety to give the methoxy-bridged bis(silylene) complex Cp(OC)M{SiMe2···O(Me)···SiMe2} (3a, M = Ru; 3b, M = Fe). The X-ray crystal structure analysis of 2a revealed that 2a has a five-membered chelate ring and the Ru−Si(silylene) bond (2.291(2) Å) is much shorter than the other Ru−Si bond (2.350(1) Å). It can be concluded from the bond lengths that the former possesses a partial double-bond character while the latter is a normal Ru−Si single bond. Photolysis of diisopropyl derivatives CpM(CO)2SiMe2SiiPr2SiMe2OMe (4a, M = Ru; 4b, M = Fe) gave Cp(OC)M{SiMe2←O(Me)SiMe2SiiPr2} (5a, M = Ru; 5b, M = Fe) exclusively, in which the positions of substituents on silicon atoms in 5a and 5b were determined by 29Si−1H COLOC and NOESY NMR spectra. A mechanism involving 1,2-migration of the methoxydisilanyl group to the metal center was suggested. Irradiation of the tetrasilanyl complex CpFe(CO)2SiMe2SiMe2SiMe2SiMe2OMe (6) caused a complicated reaction, giving at least five products having methoxy groups coordinated to silylene ligands.

The Nature of the Ring-Opening Process in a Substituted Cyclopropylmethyliron Complex

Irradiation of CpFe(CO)2(2,2-dimethylcyclopropylmethyl) (4) in the absence and presence of triphenylphosphine leads to the ring-opened and CpFe(CO)(PPh3)CH2CMe2CHCH2) (7). These are interconverted on further irradiation and on heating are more slowly converted to the π-allylic complex CpFe(CO)(η3CH2CHCHCHMe2) (8). Ring-opening rearrangement in the sense to produce mainly 6 or 7 (with a primary σ-bonded alkyl group) rather than products derived from a tertiary σ-bonded alkyl group is most consistent with a concerted four-center organometallic rearrangement process. A radical route, previously proposed for the unsubstituted cyclopropylmethyl complex, is unlikely. Complex 4 also undergoes normal migratory insertion to an acyl complex, without opening of the cyclopropylmethyl group.

THEORETICAL COMPARISON OF THE BONDING OF CHALCOCARBONYL LIGANDS

Fenske-Hall molecular orbital calculations on the complexes CpFe(CO)2(CX)+ (X = O, S, Se, and Te) have been used to quantify the nature of bonding between the CX ligands and the metal atom. In addition, conclusions have been reached about the reactivity of the complexes under both nucleophilic and electrophilic attack. The previously established trend of increasing metal—ligand bond strength as X changes from O to S to Se is demonstrated by our molecular orbital calculations, and found to extend to Te. The mechanism for nucleophilic attack, variously explained in the past by either charge control or orbital control, is quantitatively ascribed to orbital control only. The nature of electrophilic attack on these complexes is also found to begin with orbital control.

Reactive Intermediates in the Photodecarbonylation of the Cyclopentadienyl and Indenyl Complexes CpFe(CO)2(C(O)CH3) and IndFe(CO)2(C(O)CH3) (Cp = η5-C5H5; Ind = η5-C9H7)

Time-resolved infrared and time-resolved optical spectroscopy have been used to probe further into the spectra and dynamics of reactive intermediates I and Iind generated by flash photodecarbonylation of the respective acetyl complexes CpFe(CO)2(C(O)CH3) (A) and IndFe(CO)2(C(O)CH3) (Aind) (Cp = η5-C5H5; Ind = η5-C9H7). The competitive reaction dynamics of CH3 migration to the metal, trapping by CO, and trapping by other ligands such as P(OCH3)3 were determined for these intermediates in various solvents. Hydrostatic pressure effects on the competitive photoreaction pathways for both A and Aind in hexane solutions were also examined, and it was found that the photosubstitution pathway has a significantly more negative activation volume than does the photoinduced methyl migration (although a less negative value was found than that previously reported from these laboratories). The indenyl intermediate Iind is about 5-fold more reactive toward methyl migration and toward trapping by various ligands than is th...

Room-Temperature Reactions of the Intermediate(s) Generated by Flash Photolysis of (η5-C5H5)Fe(CO)2CH3

The transient formed by the photolysis of the methyl complex CpFe(CO)2CH3 (M, Cp = (η5-C5H5)) has been studied by FTIR spectroscopy in methylcyclohexane solution at 77 K and by time-resolved infrared detection in ambient-temperature solutions in cyclohexane and tetrahydrofuran. The transient IR spectrum of the intermediate IM displays a single νco absorption band and can be characterized as a monocarbonyl. In 295 K solution, the reaction of IM with CO occurs with second-order kinetics (rate = kco[IM][CO]) with kco values of (6.3 ± 0.2) × 108 and (3.4 ± 0.4) × 106 M-1 s-1 in cyclohexane and THF, respectively. On the basis of these data, IM is concluded to be the solvento complex CpFe(CO)(Sol)CH3.

Syntheses, characterization and structures of CpFe(CO)( μ-I)( μ-dppm)M(CO) 4 (M=Cr, Mo, W)

Reaction of CpFe(CO)I( η 1-dppm) with M(CO) 4(L) 2 (L=acetonitrile or norbornadiene) affords the heterobimetallic complexes CpFe(CO)( μ-I)( μ-dppm)M(CO) 4 ( 1, 2 and 3 for M=Cr, Mo and W, respectively). These new complexes have been characterized by elemental analyses and IR, mass, 1H and 31P NMR spectroscopies. The crystal structures of 1 and 3 reveal that the two heterometal atoms are not bonded but are bridged by a dppm and an iodide ligands. Compound 1 crystallizes in a space group P2 1/ c with a=10.664(3) Å, b=15.495(4) Å, c=20.494(3) Å, β=92.37(2)°, V=3383(1) Å 3, Z=4 and R/ R F =0.058/0.050. Compound 3 crystallizes in a space group P2 1/ c with a=10.668(2) Å, b=15.567(2) Å, c=20.512(2) Å, β=92.65(1)°, V=3402.7(8)Å 3, Z=4 and R/ R F =0.048/0.066.

Dppa als Komplexligand: Metall-Koordination und P-N-Spaltung in Komplexen des Typs [CpM(L)dppa]X (M = Fe, Mn; L = CO, NO) / Dppa as a Ligand: Metal Coordination and P-N Cleavage in Complexes of the Type [CpM(L)dppa]X (M = Fe, Mn; L = CO, NO)

Abstract The reactions of [CpMn(CO)2(NO)]BF4 or CpFe(CO)2Cl with PPh2NHR (R = Ph, PPh2) lead to the salts [CpML(CO)PPh2NHR]X with monodentate aminophosphine ligands. In the case of R = PPh2 (= dppa) the complexes [CpML(dppa)]X with bidentate dppa are also formed. The salt [CpFe(CO)(dppa)]Cl can be deprotonated to give the neutral complex CpFe(CO){(PPh2)2N)} with the diphosphinoamide ligand, which can be N-alkylated by Mel to afford [CpFe(CO){(PPh2)2NMe}]I. The complex [CpMn(NO)(dppa)]BF4 undergoes a P-N cleavage reaction by the solvent methanol to form [CpMn(NO)(PPh2NH2)(PPh2OMe)]BF4. The non-chelated complexes [CpFe(CO)2PPh2NHR]Cl are deprotonated by DBU to give the neutral ferrioiminophosphoranes CpFe(CO)2PPh2 = NR. For R = PPh2 photolysis leads to CO-elimination and to CpFe(CO)(PPh2NPPh2). CpFe(CO)2PPh2NPPh2 can be alkylated by Mel or metallated by CpFe(CO)2Cl to form [CpFe(CO)2PPh2NPPh2Me]I or [CpFe(CO)2PPh2NPPh2(CO)2FeCp]Cl, respectively. Oxidation of CpFe(CO)2PPh2NPPh2 is possible by (SiMe3)2O2, sulfur, or selenium to lead to the neutral complexes CpFe(CO)2PPh2=NPPh2 = E (E = O, S, Se) with a heterodiene system. The IR and NMR spectra of all species as well as the X-ray structures of the complexes [CpFe(CO)dppa]Cl, [CpMn(NO)dppa]BF4 and [CpMn(NO)(PPh2NH2)(PPh2OMe)]BF4 are reported and discussed.

57Fe NMR Study of Ligand Effects in Cyclopentadienyliron Complexes

The first systematic 57Fe NMR study of ligand effects in cyclopentadienyliron complexes is presented. Four series encompassing a total of 35 compounds have been studied. Among the compounds are five new ring-substituted complexes with the formula (C5H4Y)Fe(CO)(PPh3)(Me), Y = Me, SiMe3, NEt2, I, and Ph. The crystal structure of (C5H4I)Fe(CO)(PPh3)(Me) (32) was determined. For the series CpFe(CO)2R (type I), 57Fe shielding was found to decrease with the bulkiness of the alkyl ligand R and to correlate with the CO-insertion rate of the complex. In type III complexes CpFe(CO)(L)(COMe), L = PR3, and CO, it is again the steric requirement of the ligand L that dominates the 57Fe chemical shift which increases with larger cone angles (θ). In contrast, a strong electronic effect was found for type II complexes CpFe(CO)(PPh3)X, X = H, Me, and I. Ligands with higher electronegativity induce a shift of the 57Fe resonance to higher frequencies. In the complexes (C5H4Y)Fe(CO)(PPh3)(Me), Y = Me, H, SiMe3, NEt2, I, Ph, COOMe, and COiPr (type IV), again electronic effects are dominant, whereby electron acceptor substituents (e.g. Y = COiPr, COOMe) cause a deshielding of the iron nucleus, relative to complexes with electron donor substituents (e.g. Y = Me, H, SiMe3). Dominant electronic ligand effects in type IV complexes are also apparent from the correlation of δ(57Fe) with the electronic substituent parameter σI. The 57Fe chemical shift is shown to be very sensitive to changes in the ligand sphere, and the effects are discussed in terms of the paramagnetic shielding constant (σpara). The 1J(57Fe,13C) coupling constants and longitudinal relaxation times T1 of 57Fe in selected complexes have been determined and ligand effects are discussed.

Thermal substitution reactions of the heterodinuclear complex CpFe(CO)2Co(CO)4 with phosphorus ligands

Abstract The thermal reactions of CpFe(CO) 2 Co(CO) 4 with phosphorus ligands (L = P( n -Bu) 3 , P( c -Hx) 3 , PPh 3 , P(OPh) 3 , PMePh 2 ) lead to formation of both ionic disproportionation products, [CpFe(CO) 2 L] + [Co(CO) 4 ] − , via a radical chain path, and neutral monosubstitution products, CpFe(CO) 2 Co(CO) 3 L, via a CO-dissociative pathway. Reaction with PPh( o -CH 3 Ph) 2 results in forming only the monosubstituted product and no reactions were observed with the two bulkiest ligands, P( o -CH 3 Ph) 3 and P(C 6 F 5 ) 3 . The slow CO-dissociative pathway is always in effect in these reactions, and the product distribution is therefore determined by the rate of radical chain process. The steric and electronic requirements on the ligand for the radical chain process to dominate are much milder than that for other homodinuclear and heterodinuclear complexes that have been studied.