Fe-P Bond Research Articles

Prediction of HER electrocatalyst with enhanced performance based on atoms-doped black phosphorene: A first-principles study

Black phosphorene (BP), with great potential as electrocatalyst material, has been paid much attention around the world due to its unique structural and electronic properties. And doping of atoms has been regarded as an efficient method to boost their electrocatalytic performance. Herein, we investigated the structural characteristics and hydrogen evolution reaction (HER) performance of atoms-doped BP based on density functional theory (DFT) calculations. The results show that the doping of metal atoms can readjust the Bader charge distribution and density of state (DOS), improving their electronic properties. In addition, among the systems doped with eight kinds of elements (e.g. Fe, Co, Ni, Cu, Ru, Rh, Pd, and Ag), the Fe-doped BP (Fe/BP) presents most nearly neutral hydrogen adsorption free energies (ΔGH*, 0.034 eV), the highest charge exchange between Fe and P through the Fe-P bond, the highest charge exchange between H and Fe/BP model, and its d-band center is most nearly the Femi level as compared with the other systems. The results mentioned above can verify that the doping of metal atoms, especially the doping of Fe atoms can improve the HER performance obviously. This work can provide theoretical significance for the design of high-efficiency HER electrocatalyst.

A Nontrigonal Tricoordinate Phosphorus Ligand Exhibiting Reversible "Nonspectator" L/X-Switching.

We report here a "nonspectator" behavior for an unsupported L-function σ3 -P ligand (i.e. P{N[o-NMe-C6 H4 ]2 }, 1a) in complex with the cyclopentadienyliron dicarbonyl cation (Fp+ ). Treatment of 1a⋅Fp+ with [(Me2 N)3 S][Me3 SiF2 ] results in fluoride addition to the P-center, giving the isolable crystalline fluorometallophosphorane 1aF ⋅Fp that allows a crystallographic assessment of the variance in the Fe-P bond as a function of P-coordination number. The nonspectator reactivity of 1a⋅Fp+ is rationalized on the basis of electronic structure arguments and by comparison to trigonal analogue (Me2 N)3 P⋅Fp+ (i.e. 1b⋅Fp+ ), which is inert to fluoride addition. These observations establish a nonspectator L/X-switching in (σ3 -P)-M complexes by reversible access to higher-coordinate phosphorus ligand fragments.

Pyrrolyl-based pincer complexes of iron – Synthesis and electronic structure

Four- and five-coordinate high-spin (S=2) Fe(II) complexes bearing the pyrrolyl-derived tBuPNP pincer ligand [tBuPNP=2,5-(tBu2PCH2)2(C4H2N)] have been prepared. All three complexes were characterized by X-ray diffraction, zero-field 57Fe Mössbauer spectroscopy and solid-state magnetic susceptibility studies. Furthermore, the experimentally determined Mössbauer parameters of compounds 4–6 can be modeled satisfactorily by density functional theory (DFT) computations at the B97D level of theory. Introduction of the sterically demanding bis(trimethylsilyl)amido moiety induces significant distortions from ideal tetrahedral geometry in [(tBuPNP)FeN(SiMe3)2] (4), featuring an Fe(II) high-spin state with large negative axial zero-field splitting and slow paramagnetic relaxation at low temperature, as evidenced by measurements of the solid-state magnetic susceptibility and zero-field 57Fe Mössbauer spectroscopy. Replacing the chlorido ligand in [(tBuPNP)FeCl] (3) by the bidentate acetylacetonato (acac) ligand enforces a trigonal–bipyramidal structure in [(tBuPNP)Fe(acac)] (5), in which the Fe(II) atom also adopts a high-spin configuration. Reaction of 3 with adamantyl azide allowed us to confirm the inherent lability of the phosphine coordination, since the azide inserts into the FeP bond to form [(tBuPNPN3Adamantyl)FeCl] (6), in which the tBuPNP ligand is transformed to a phosphino-pyrrolyl-phosphazide ligand framework (tBuPNPN3Adamantyl). This motif can be considered as a trapped Staudinger intermediate along the reaction pathway of free phosphines with organic azides to form phosphinimines. Bidentate binding of the phosphazide sidearm in κN:κN-fashion to the Fe(II) atom enforces an s-anti coordination of the P1–N2–N3–N4 moiety, which raises the barrier for the thermodynamically favorable N2 elimination and allows this intermediate to be trapped. Complex 6 contains a high-spin Fe(II) atom with a square-pyramidal structure.

Synthetic, Structural, and Spectroscopic Characterization of a Novel Family of High-Spin Iron(II) [(β-Diketiminate)(phosphanylphosphido)] Complexes.

This work describes a series of iron(II) phosphanylphosphido complexes. These compounds were obtained by reacting lithiated diphosphanes R2PP(SiMe3)Li (R = t-Bu, i-Pr) with an iron(II) β-diketiminate complex, [LFe(μ2-Cl)2Li(DME)2] (1), where DME = 1,2-dimethoxyethane and L = Dippnacnac (β-diketiminate). While the reaction of 1 with t-Bu2PP(SiMe3)Li yields [LFe(η1-Me3SiPP-t-Bu2)] (2), that of 1 with equimolar amounts of i-Pr2PP(SiMe3)Li, in DME, leads to [LFe(η2-i-Pr2PPSiMe3)] (3). In contrast, the reaction of 1 with (i-Pr2N)2PP(SiMe3)Li provides not an iron-containing complex but 1-[(diisopropylamino)phosphine]-2,4-bis(diisopropylamino)-3-(trimethylsilyl)tetraphosphetane (4). The structures of 2-4 were determined using diffractometry. Thus, 2 exhibits a three-coordinate iron site and 3 a four-coordinate iron site. The increase in the coordination number is induced by the change from an anticlinal to a synclinal conformation of the phoshpanylphosphido ligands. The electronic structures of 2 and 3 were assessed through a combined field-dependent 57Fe Mössbauer and high-frequency and -field electron paramagnetic resonance spectroscopic investigation in conjunction with analysis of their magnetic susceptibility and magnetization data. These studies revealed two high-spin iron(II) sites with S = 2 ground states that have different properties. While 2 exhibits a zero-field splitting described by a positive D parameter (D = +17.4 cm-1; E/D = 0.11) for 3, this parameter is negative [D = -25(5) cm-1; E/D = 0.15(5)]. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations provide insights into the origin of these differences and allow us to rationalize the fine and hyperfine structure parameters of 2 and 3. Thus, for 2, the spin-orbit coupling mixes a z2-type ground state with two low-lying {xz/yz} orbital states. These interactions lead to an easy plane of magnetization, which is essentially parallel to the plane defined by the N-Fe-N atoms. For 3, we find a yz-type ground state that is strongly mixed with a low-lying z2-type orbital state. In this case, the spin-orbit interaction leads to a partial unquenching of the orbital momentum along the x axis, that is, to an easy axis of magnetization oriented roughly along the Fe-P bond of the phosphido moiety.

Cleavage of phosphorus-sulfur bond and formation of (μ4-S)Fe4 core from photochemical reactions of Fe(CO)5 with [(RO)2PS2]2; (R = Me, Et, iPr)

When hexane or alcohol solutions containing iron pentacarbonyl and bis(dialkoxythiophosphoryl) disulfide (R = Me (1), Et (2), or Pri (3)), were irradiated with 366 nm light, under argon atmosphere at 0 °C, clusters [(μ-RS)Fe2(CO)6](μ4-S)[(μ-(OR)2P)Fe2(CO)6] (4: R = Me, 5: R = Et) and [Fe2(CO)6S{P(OiPr)2}]2 (6) were obtained in hexane and [Fe4(CO)8(μ-CO)2(μ4-S)2P(OR)3] (7: R = Me, 8: R = Et) in MeOH and EtOH respectively. These reactions involve P–S bond cleavage of ligands and desulfurization process and Fe-S and Fe-P bond formation. Computational and experimental bond parameters have been studied on the new compounds.

Connecting [NiFe]- and [FeFe]-hydrogenases: mixed-valence nickel-iron dithiolates with rotated structures.

New mixed-valence iron-nickel dithiolates are described that exhibit structures similar to those of mixed-valence diiron dithiolates. The interaction of tricarbonyl salt [(dppe)Ni(pdt)Fe(CO)(3)]BF(4) ([1]BF(4), where dppe = Ph(2)PCH(2)CH(2)PPh(2) and pdt(2-) = -SCH(2)CH(2)CH(2)S-) with P-donor ligands (L) afforded the substituted derivatives [(dppe)Ni(pdt)Fe(CO)(2)L]BF(4) incorporating L = PHCy(2) ([1a]BF(4)), PPh(NEt(2))(2) ([1b]BF(4)), P(NMe(2))(3) ([1c]BF(4)), P(i-Pr)(3) ([1d]BF(4)), and PCy(3) ([1e]BF(4)). The related precursor [(dcpe)Ni(pdt)Fe(CO)(3)]BF(4) ([2]BF(4), where dcpe = Cy(2)PCH(2)CH(2)PCy(2)) gave the more electron-rich family of compounds [(dcpe)Ni(pdt)Fe(CO)(2)L]BF(4) for L = PPh(2)(2-pyridyl) ([2a]BF(4)), PPh(3) ([2b]BF(4)), and PCy(3) ([2c]BF(4)). For bulky and strongly basic monophosphorus ligands, the salts feature distorted coordination geometries at iron: crystallographic analyses of [1e]BF(4) and [2c]BF(4) showed that they adopt "rotated" Fe(I) centers, in which PCy(3) occupies a basal site and one CO ligand partially bridges the Ni and Fe centers. Like the undistorted mixed-valence derivatives, members of the new class of complexes are described as Ni(II)Fe(I) (S = ½) systems according to electron paramagnetic resonance spectroscopy, although with attenuated (31)P hyperfine interactions. Density functional theory calculations using the BP86, B3LYP, and PBE0 exchange-correlation functionals agree with the structural and spectroscopic data, suggesting that the spin for [1e](+) is mostly localized in a Fe(I)-centered d(z(2)) orbital, orthogonal to the Fe-P bond. The PCy(3) complexes, rare examples of species featuring "rotated" Fe centers, both structurally and spectroscopically incorporate features from homobimetallic mixed-valence diiron dithiolates. Also, when the NiS(2)Fe core of the [NiFe]-hydrogenase active site is reproduced, the "hybrid models" incorporate key features of the two major classes of hydrogenase. Furthermore, cyclic voltammetry experiments suggest that the highly basic phosphine ligands enable a second oxidation corresponding to the couple [(dxpe)Ni(pdt)Fe(CO)(2)L](+/2+). The resulting unsaturated 32e(-) dications represent the closest approach to modeling the highly electrophilic Ni-SI(a) state. In the case of L = PPh(2) (2-pyridyl), chelation of this ligand accompanies the second oxidation.

Activation of H–H and H–O Bonds at Phosphorus with Diiron Complexes Bearing Pyramidal Phosphinidene Ligands

The complex [Fe(2)Cp(2)(μ-PMes*)(μ-CO)(CO)(2)] (Mes* = 2,4,6-C(6)H(2)(t)Bu(3)), which in the solid state displays a pyramidal phosphinidene bridge, reacted at room temperature with H(2) (ca. 4 atm) to give the known phosphine complex [Fe(2)Cp(2)(μ-CO)(2)(CO)(PH(2)Mes*)] as the major product, along with small amounts of other byproducts arising from the thermal degradation of the starting material, such as the phosphindole complex [Fe(2)Cp(2)(μ-CO)(2)(CO){PH(CH(2)CMe(2))C(6)H(2)(t)Bu(2)}], the dimer [Fe(2)Cp(2)(CO)(4)], and free phosphine PH(2)Mes*. During the course of the reaction, trace amounts of the mononuclear phosphide complex [FeCp(CO)(2)(PHMes*)] were also detected, a compound later found to be the major product in the carbonylation of the parent phosphinidene complex, with this reaction also yielding the dimer [Fe(2)Cp(2)(CO)(4)] and the known diphosphene Mes*P═PMes*. The outcome of the carbonylation reactions of the title complex could be rationalized by assuming the formation of an unstable tetracarbonyl intermediate [Fe(2)Cp(2)(μ-PMes*)(CO)(4)] (undetected) that would undergo a fast homolytic cleavage of a Fe-P bond, this being followed by subsequent evolution of the radical species so generated through either dimerization or reaction with trace amounts of water present in the reaction media. A more rational synthetic procedure for the phosphide complex was accomplished through deprotonation of the phosphine compound [FeCp(CO)(2)(PH(2)Mes*)](BF(4)) with Na(OH), the latter in turn being prepared via oxidation of [Fe(2)Cp(2)(CO)(4)] with [FeCp(2)](BF(4)) in the presence of PH(2)Mes*. To account for the hydrogenation of the parent phosphinidene complex it was assumed that, in solution, small amounts of an isomer displaying a terminal phosphinidene ligand would coexist with the more stable bridged form, a proposal supported by density functional theory (DFT) calculations of both isomers, with the latter also revealing that the frontier orbitals of the terminal isomer (only 5.7 kJ mol(-1) above of the bridged isomer, in toluene solution) have the right shapes to interact with the H(2) molecule. In contrast to the above behavior, the cyclohexylphosphinidene complex [Fe(2)Cp(2)(μ-PCy)(μ-CO)(CO)(2)] failed to react with H(2) under conditions comparable to those of its PMes* analogue. Instead, it slowly reacted with HOR (R = H, Et) to give the corresponding phosphinous acid (or ethyl phosphinite) complexes [Fe(2)Cp(2)(μ-CO)(2)(CO){PH(OR)Mes*}], a behavior not observed for the PMes* complex. The presence of BEt(3) increased significantly the rate of the above reaction, thus pointing to a pathway initiated with deprotonation of an O-H bond of the reagent by the basic P center of the phosphinidene complex, this being followed by the nucleophilic attack of the OR(-) anion at the P site of the transient cationic phosphide thus formed. The solid-state structure of the cis isomer of the ethanol derivative was determined through a single crystal X-ray diffraction study (Fe-Fe = 2.5112(8) Å, Fe-P = 2.149(1) Å).

Grain Boundary Embrittlement of Fe Induced by P Segregation: First-Principles Tensile Tests

The GB embrittlement mechanism of Fe enhanced by P segregation has been investigated by first-principles tensile tests because a P atom is a famous GB embrittler in Fe. The first-principles tensile tests have been performed on Fe with two P-segregated GBs, where P atoms are located at the different sites, and with a nonsegregated GB. The tensile strength and the strain to failure in the P-segregated GBs were lower than those in the nonsegegated GB. The first bond breaking occurred at the Fe-P bond owing to the covalent-like characteristics, although the charge densities were high at the Fe-P bonds even just before the bond breaking. This premature bond breaking of Fe-P was independent of the location of the P atom.

First-Principles Study on Enhanced Grain Boundary Embrittlement of Iron by Phosphorus Segregation

It is known that segregation of P atoms at grain boundaries (GB) enhances the intergranular embrittlement in Fe. In the present work, firstprinciples tensile tests have been performed on two bcc Fe cell models with a 3 ð111Þ=1⁄21 10 tilt GB: the cell model without P segregation at the GB (clean GB model) and the cell model with P segregation at the GB (P-segregated GB model). The tensile strength and the strain to failure in the P-segregated GB model were 6% and 13% lower than those in the clean GB model. The first bond breaking occurred at the Fe-P bond due to the covalent-like characteristics, although the charge densities were high at the Fe-P bonds. This premature bond breaking of Fe-P was independent of the location of the P atom. [doi:10.2320/matertrans.MBW201022]

Bond mobility mechanism in grain boundary embrittlement: First-principles tensile tests of Fe with a P-segregatedΣ3grain boundary

First-principles simulated tensile tests have been performed on Fe with a P-segregated grain boundary to investigate the nature of the bond mobility mechanism in grain boundary embrittlement. The first site for bond breaking was the Fe-P bond, despite its high charge density. This is because the Fe-P bond exhibited the covalentlike characteristics of a localized bonding and the mobility of electrons was reduced. The breaking of the Fe-P bond accelerated the breaking of the Fe-Fe bond around the Fe-P bond because the Fe-P bond breaking affected the electron density of states of the Fe-Fe bond. Thus, P segregation enhanced the grain boundary embrittlement in Fe.

Interplay among Tetrahedrane, Butterfly Diradical, and Planar Rhombus Structures in the Chemistry of the Binuclear Iron Carbonyl Phosphinidene Complexes Fe2(CO)6(PX)2

Density functional theory studies on a series of Fe2(CO)6(PX)2 derivatives show the tetrahedrane to be the most stable for the alkyl (X = Me, tBu), P-H (X = H), and chloro (X = Cl) derivatives. However, butterfly diradical and planar rhombus structures are found to be more stable than tetrahedranes for the amino (X = NH2, NMe2, and NiPr2) and aryloxy (R = 2,6-tBu2-4-Me-C6H2O) derivatives. For the chloro (X = Cl) and methoxy (X = OMe) derivatives energetically accessible bishomotetrahedrane Fe2(CO)6P2(mu-X)2 isomers are observed in which the X substituents on the phosphorus atoms interact with the iron atom to form two direct Fe-X bonds at the expense of two of the four Fe-P bonds. In addition, the global minimum for the hydroxy (X = OH) derivative is an unusual FeP-butterfly structure with a central Fe-P bond as well as two external Fe-P bonds, one external P-P bond, and one external Fe=Fe double bond. Comparison of calculated with experimental nu(CO) frequencies shows that low-temperature Nujol matrix photolysis of (iPr2NP)2COFe2(CO)6 leads to a planar rhombus rather than a tetrahedrane isomer of Fe2(CO)6(PNiPr2)2.

Quantum Chemistry Study on Local Structure and Properties of Amorphous Fe80P20 Alloy

According to the structure features of Fe80P20, a series of clusters Fe4P were designed and focused on studying the stability of local structure, charge distribution and chemical bond. Using the DFT method, energy and structure of Fe4P clusters were optimized and analyzed. The computational results showed that the energy of cluster 1(2) has the lowest energy, and the possibility of its existence in the Fe80P20 is high. Analyzing the transition states among the clusters, it was found that the clusters in the doublet state are more stable than those in the quartet state. The numbers of the FeP bond in the clusters play important roles in the cluster stability and electrons transfer properties. The more numbers of FeP bonds in the clusters, the higher the cluster stability, and the weaker the ability of P atom to get electron. The number of Fe atoms, which has bonding interactions with the P atom, is direct proportional to the average 3d orbit population of Fe atom. Basing on the orbital population, average magnetic moments of each Fe atom in the Fe4P clusters were calculated, and they are all smaller than that of single metal Fe atom. This suggests that all Fe4P clusters have soft magnetic property and they are expected to be perfect material for preparing soft magnetic apparatus.

Chemical preparation and investigation of Fe-P-B ultrafine amorphous alloy particles

A series of Fe-P-B ultrafine amorphous alloy particles has been prepared by the chemical reduction method. The composition and size of the particles have been effectively adjusted. Mossbauer spectroscopy in addition to some other techniques has been used to investigate the reaction process, the factors that influence the preparation, the crystallization of the particles, and the interactions between the components within them. The results indicate that the co-deposition of iron, phosphorus and boron atoms in the solution at room temperature forms Fe-P-B amorphous alloy particles, and a preferential bonding of Fe-P bond to Fe-B one exists in the particles.

Structure of trans-Bis{3-methylbut-3-en-1-yn-1-yl}bis{1,2-bis(dimethylphosphino)ethane}iron(II)

An iron(II) bisacetylide complex containing conjugated 3-methylbut-3-en-1-yn-1-yl ligands has been synthe-sized and characterized. The structure consists of a neutral trans-[Fe{C≡CC(CH3)=CH2}2{Me2PCH2 CH2PMe2}2] molecule with iron located at a centre of symmetry. The Fe-P bond lengths {2·184(1) Å} are the same as those in the analogous propyne complex {2·183(1) Å} and phenylacetylide complex {2·180(5) and 2·191(3) Å} , and are indicative of low-spin iron(II). The Fe-C distance is 1·905(4) Å.

X-ray absorption spectroscopic studies of the FeZn derivative of uteroferrin.

The FeZn derivative of purple acid phosphatase from porcine uterus (FeZnUf) and its phosphate complex (FeZnUf.PO4) have been characterized by X-ray absorption spectroscopy at both the iron and zinc K-edges, to gain insight into the nature of the FeZn active site as well as the phosphate binding mode. Pre-edge data show that both FeZnUf and FeZnUf.PO4 have a 6-coordinate iron site. The iron site has an average Fe-O/N bond length of 2.01-2.02 A, which can be resolved into subshells of 1.92 and 2.11 A for FeZnUf.PO4. On the other hand, the zinc site has a shell of scatterers at 2.02-2.03 A plus one scatterer at ca. 2.4 A. These metal-ligand bond lengths are consistent with the nature of the ligands deduced from spectroscopic studies or identified in the crystal structure of the related kidney bean purple acid phosphatase (KBPAP). The outer-sphere analysis indicates an Fe-Zn separation of approximately 3.3 A in both FeZnUf and FeZnUf.PO4, consistent with the presence of an M2(mu-OR)2 diamond core as found in the crystal structures of KBPAP, calcineurin, and protein phosphatase 1. The Fe-P and Zn-P bond distances in FeZnUf.PO4 are determined to be 3.23 and 3.18 A, respectively, indicating that phosphate binds to the dinuclear center in a bidentate mode; such a mode has been observed in oxoanion complexes of KBPAP, calcineurin, and alkaline phosphatase, as well as in a number of synthetic FeFe and FeZn complexes. The implications of these structural results on the mechanism of phosphatase action are discussed.

Characterization of Pentacyano(Phosphine or Phosphite)Ferrates (II) By31P NMR and Cyclic Voltammetry

Abstract The Fe-P bond in low-spin pentacyanoferrates(II) of the type Na3[Fe(CN)5L](L[dbnd]phosphine or phosphite) has been characterized by 31P NMR and cyclic voltammetry. The chemical shift in the 31P{1H} NMR spectra increases with the redox potential on the cyclic voltammogram. A linear dependence of the chemical shifts on the redox potentials has revealed that the π-back donation from the iron d π-orbitals to the phosphorus d π-orbitals plays an important role in the character of the Fe-P bond.

Structure of trans-bis[1,2-bis(dimethylphosphino)ethane]dibromoiron(II)

[FeBr 2 (C 6 H 16 P 2 ) 2 ], M r =515.94, monoclinic, P2 1 /n, a=8.739 (2), b=12.743 (2), c=9.533 (1) A, β=91.32 (1) o , V=1061.2 A 3 , Z=2, D x =1.615 g cm -3 , λ(Mo Kα)=0.71069 A, μ=45.56 cm -1 , F(000)=520, T=293 K, final R=0.043 for 1178 observed reflections. The structure consists of a neutral trans-[FeBr 2 {1,2-bis(dimethylphosphino)ethane} 2 ] molecule with the Fe atom located at a centre of symmetry. The Fe-P bond lengths (2.230 and 2.236A) are indicative of low spin Fe II .

Platinum-complex-catalyzed 1,4-disilylation of 1,3-dienes using organodisilanes: remarkable effect of a phenyl functionality on silicon atom

The diphosphenyl complex (eta-5-C5Me5)-(CO)2Fe-P=P-Mes* (Mes* = 2,4,6-tBu3C6H2) undergoes a [3 + 2] dipolar cycloaddition with hexafluoroacetone to give the metalla heterocycle (eta-5-C5Me5)(CO)-Fe-P(=PMes*)OC(CF3)2C(O) with a remarkably short Fe-P bond (2.084 (4) angstrom) and an exocyclic P=P bond. When stored in solution at -40-degrees-C, this complex partly rearranges to the metalated 1-oxa-2,3-diphosphetane (eta-5-C5Me5)(CO)2Fe-P-P(Mes*)OC(CF3)2. The molecular structures of both isomers were elucidated by single-crystal X-ray analyses.

Übergangsmetall-silyl-komplexe: XLII. Einfluβ des phosphan-liganden auf bildung, struktur und stabilität der hetero-zweikernkomplexe (CO) 3(R′ 3P)(R 3Si)Fe—ML n (M  Cu, Ag, Au, Hg)

The anionic silyl complexes Na[Fe(CO) 3(PR′ 3)SiR 3] (PR′ 3  PMe 3: SiR 3  SiMePh 2, SiMe 3; PR′ 3  P nBu 3: SiR 3  SiMePh 2; PR′ 3  PPh 2H: SiR 3  SiPh 3, SiMePh 2, SiMe 2Ph) were prepared by deprotonation of the corresponding hydrido silyl complexes. They react with CH 3I or Me 3SnCl to give mer-(CO) 3(R′ 3P)(R 3Si)FeER 3 (PR′ 3  PMe 3 and PPh 2H; ER 3  CH 3, SnMe 3), while with metal complex halides XML n , (ML n ,  AuPR 3, AgPPh 2Tol, CuPR 3 Cudppe, HgPh) the hetero-binuclear complexes mer-(CO) 3(R′ 3P)R 3Si) FeML n are obtained, which contain unbridged metal—metal bonds. Upon reaction of [Fe(CO) 3(PR′ 3)SiR 3] − with HgBr 2 in THF the trinuclear complexes [ fac-(CO) 3(R′ 3P)(R 3Si)Fe] 2Hg are obtained, from which the binuclear complexes mer-(CO) 3(R′ 3P)(R 3Si)FeHgX are formed in toluene with a second equivalent of HgX 2. X-Ray structure analyses of the octahedral complexes mer-(CO) 3(Me 3P)(Ph 2MeSi)(FAuPPh 2Tol (FeAu 252.7(3) pm), mer(CO) 3(Me 3P)(Ph 2MeSi)FeAgPh 2Tol (FeAg 258.1(1) pm) and mer-(CO) 3(Me 3P)-(Ph 2MeSi)FeHgBr) (FeHg 251.5(3) pm) show that the Fe-metal bond is cis to both the PMe 3 and the SiMePh 2 ligand. The comparison of the Fe-Si, Fe-P and Fe-M bond distances indicates that the polarity of the Fe-M bond increases from M  Hg and M  Au to M  Ag. The Fe-Hg compound is loosely dimerized via unsymmetrical Br bridges (Hg-Br 253.5(3) and 306.3(1) pm).

Quantitative analysis of ligand effects (QALE). Systematic study of iron-phosphorus bond lengths and their relationship to steric thresholds

Systematic determination of Fe-P bond lengths for the set of complexes (η-Cp)(CO)(L)FeCOMe containing «sterically unencumbered» σ-donor phosphorus(III) ligands shows that the Fe-P bond lengths vary over a narrow range (2.195±0.0015 A) and are only slightly dependent on the σ-donicity and size of the ligand. π-Acid ligands (i.e. P(OR) 3 ) exhibit significantly shorter Fe-P bond lengths around 2.10 A. In light of this virtual constancy of σ bond length for a family of complexes, it is reasonable to expect steric thresholds to be manifest