Trimethylphosphine Ligands Research Articles

Massive dipoles across the metal-semiconductor cluster interface: towards chemically controlled rectification.

An interface between a metallic cluster (MgAl12) and a semiconducting cluster (Re6Se8(PMe3)5) is shown to be marked by a massive dipole reminiscent of a dipolar layer leading to a Schottky barrier at metal-semiconductor interfaces. The metallic cluster MgAl12 with a valence electron count of 38 electrons is two electrons short of 40 electrons needed to complete its electronic shells in a superatomic model and is marked by a significant electron affinity of 2.99 eV. On the other hand, the metal-chalcogenide semiconducting cluster Re6Se8(PMe3)5, consisting of a Re6Se8 core ligated with five trimethylphosphine ligands, is highly stable in the +2 charge-state owing to its electronic shell closure, and has a low ionization energy of 3.3 eV. The composite cluster Re6Se8(PMe3)5-MgAl12 formed by combining the MgAl12 cluster through the unligated site of Re6Se8(PMe3)5 exhibits a massive dipole moment of 28.38 D resulting from a charge flow from Re6Se8(PMe3)5 to the MgAl12 cluster. The highest occupied molecular orbital (HOMO) of the composite cluster is on the MgAl12 side, which is 0.53 eV below the lowest unoccupied molecular orbital (LUMO) localized on the Re6Se8(PMe3)5 cluster, reminiscent of a Schottky barrier at metal-semiconductor interfaces. Therefore, the combination can act as a rectifier, and an application of a voltage of approximately 4.1 V via a homogeneous external electric field is needed to overcome the barrier aligning the two states: the HOMO in MgAl12 with the LUMO in Re6Se8(PMe3)5. Apart from the bias voltage, the barrier can also be reduced by attaching ligands to the metallic cluster, which provides chemical control over rectification. Finally, the fused cluster is shown to be capable of separating electron-hole pairs with minimal recombination, offering the potential for photovoltaic applications.

Free Energy Profile of a Model Palladium Catalyzed Fluorination of Aryl Bromide with Cesium Fluoride.

Addition of fluorine to aromatic rings has increased in importance in the past decade in view of the increased role of organofluorine compounds in the design of new pharmaceuticals. Palladium catalyzed nucleophilic fluorination of unactivated aryl halides using salts such as cesium fluoride was achieved with the use of bulky biaryl monophosphine ligand. Simple monophosphine palladium complexes were not able to promote this reaction, which is attributed to the difficult reductive elimination step and the formation of dimers of the PdL(Ph)(F) intermediate. The use of theoretical methods for reliable design of new ligands requires the knowledge of the complete free energy profile of the catalyzed reaction. Otherwise, predictions may not be observed. In this work, a complete free energy profile of a model palladium catalyzed fluorination (trimethyl phosphine ligand), including the precatalyst decomposition mechanism (allylpalladium chloride), was investigated using a reliable theoretical method, the mPW2-PLYP double-hybrid functional, which was compared with the DLPNO-CCSD(T) benchmark method. The results suggest that palladium(π-cinnamyl) chloride is not a good precatalyst, while the monophosphine palladium complex bonded to an alkene should work better. The transmetalation step raises the overall barrier for the reductive elimination by 4.3 kcal mol-1 in the case of monophosphine catalyst, making the reaction difficult (ΔG⧧ = 34.1 kcal mol-1), even in the case of no dimerization of the monophosphine palladium fluoride complex. Thus, success of a ligand to promote palladium catalysis requires not only a monophosphine ligand that avoids dimerization but also a strong repulsion to both phenyl and fluorine bonded to the palladium in the PdL(Ph)(F) complex.

Reactions of iron(II) hydrides formed by selective C[sbnd]F/C[sbnd]H bond activation in fluoroaryl-imines

In this paper the reactions of iron(II) hydrides 6–10 formed by selective CF/CH bond activation in fluoroaryl-imines were reported. Iron hydrides 6 and 7 reacted with haloalkane to give rise to the corresponding iron halides 11 and 12 with the mer-rearrangement of the three trimethylphosphine ligands. The related trifluoromethylcarboxyl iron complexes 13 and 14 with the carboxyl group as monodentate ligand were obtained from the reactions of hydrides 8 and 9 with F3CCOOH. The reaction of iron hydride 6 with Lewis acid LiBF4 delivered ionic iron complex 15. Both the reaction of iron hydride 10 with Me3SiCCH and the reaction of iron bromide 11 with Me3SiCCLi could provide the derivative trimethylsilylacetylenyl iron(II) complexes 16 and 17 respectively. The molecular structures of complexes 12, 13 and 17 were determined by single crystal X-ray diffraction.

Activation of vinylic carbon–chlorine bond by nickel complexes supported with phosphine ligands

The vinylic C–Cl bonds of ortho-chlorinated cycloalkenyl aldehydes (1–4) and ortho-chlorinated cycloalkenyl acetal derivatives (5–6) were successfully activated by nickel(0) and nickel(II) complexes supported by trimethylphosphine ligands. Except one trans-five-coordinate nickel(II) chloride complex trans-[Ni(PMe3)2Cl{(C5H6)CHO}] (7) as a cyclometalation product with coordination of the aldehyde group, the other six four-coordinate nickel(II) chloride complexes trans-[Ni(PMe3)2Cl{(C5H6)CHO}] (8), trans-[Ni(PMe3)2Cl{(C6H8)CHO}] (9), trans-[Ni(PMe3)2Cl{(C6H7Memeta)CHO}] (10), trans-[Ni(PMe3)2Cl{(C6H7Bu-tmeta)CHO}] (11), trans-[Ni(PMe3)2Cl{(C6H8)CH(OCH2CH2O)}] (12) and trans-[Ni(PMe3)2Cl{(C6H7Bu-t-meta)CH(OCH2CH2O)}] (13) as C–Cl bond activation products were obtained without coordination of the aldehyde groups. These complexes were characterized by IR and NMR. The crystal and molecular structures of complexes 8, 9 and 12 were determined by single crystal X-ray diffraction.

Highly Electron-Rich Pincer-Type Iron Complexes Bearing Innocent Bis(metallylene)pyridine Ligands: Syntheses, Structures, and Catalytic Activity

The first neutral bis(metallylene)pyridine pincer-type [ENE] ligands (E = SiII, GeII) were synthesized, and their coordination chemistry and reactivity toward iron was studied. First, the unprecedented four-coordinate complexes κ2E,E′-[ENE]FeCl2 were isolated. Unexpectedly and in contrast to other related pyridine-based pincer-type Fe(II) complexes, the N atom of pyridine is reluctant to coordinate to the Fe(II) site due to the enhanced σ-donor strength of the E atoms, which disfavors this coordination mode. Subsequent reduction of κ2Si,Si′-[SiNSi]FeCl2 with KC8 in the presence of PMe3 or direct reaction of the [ENE] ligands using Fe(PMe3)4 produced the highly electron-rich iron(0) complexes [ENE]Fe(PMe3)2. The reduction of the iron center substantially changes its coordination features, as shown by the results of a single-crystal X-ray diffraction analysis of [SiNSi]Fe(PMe3)2. The iron center, in the latter, exhibits a pseudosquare pyramidal (PSQP) coordination environment, with a coordinative (pyridine)N→Fe bond, and a trimethylphosphine ligand occupying the apical position. This geometry is very unusual for Fe(0) low-spin complexes, and variable-temperature 1H and 31P NMR spectra of the [ENE]Fe(PMe3)2 complexes revealed that they represent the first examples of configurationally stable PSQP-coordinated Fe(0) complexes: even after heating at 70 °C for >7 days, no changes are observed. The substitution reaction of [ENE]Fe(PMe3)2 with CO resulted in the isolation of [ENE]Fe(CO)2 and the hitherto unknown κ2E,E′-[ENE]Fe(CO)2L (L = CO, PMe3) complexes. All complexes were fully characterized (NMR, MS, XRD, IR, and 57Fe Mössbauer spectroscopy), showing the highest electron density on the iron center for pincer-type complexes reported to date. DFT calculations and 57Fe Mössbauer spectroscopy confirmed the innocent behavior of these ligands. Moreover, preliminary results showed that these complexes can serve as active precatalysts for the hydrosilylation of ketones.

Linear coordination fullerene C60 polymer [{Ni(Me3P)2}(μ-η(2),η(2)-C60)]∞ bridged by zerovalent nickel atoms.

Coordination nickel-bridged fullerene polymer [{Ni(Me3P)2}(μ-η(2),η(2)-C60)]∞ (1) has been obtained via reduction of a Ni(II)(Me3P)2Cl2 and C60 mixture. Each nickel atom is linked in the polymer with two fullerene units by η(2)-type Ni-C(C60) bonds of 2.087(8)-2.149(8) Å length. Nickel atoms are coordinated to the 6-6 bonds of C60 as well as two trimethylphosphine ligands to form a four-coordinated environment around the metal centers. Fullerene cages approach very close to each other in the polymer with a 9.693(3) Å interfullerene center-to-center distance, and two short interfullerene C-C contacts of 2.923(7) Å length are formed. Polymer chains are densely packed in a crystal with interfullerene center-to-center distances between fullerenes from neighboring polymer chains of 9.933(3) Å and multiple interfullerene C···C contacts. As a result, three-dimensional dense fullerene packing is formed in 1. According to optical and electron paramagnetic resonance spectra, fullerenes are neutral in 1 and nickel atoms have a zerovalent state with a diamagnetic d(10) electron configuration. The density functional theory calculations prove the diamagnetic state of the polymer with a singlet-triplet gap wider than 1.37 eV.

Alkyne reactions with trimethylphosphine complexes of iridium: Lessons for the catalysis of vinyl ester formation and alkyne dimerization

The combination of iridium with trimethylphosphine ligands yields very electron rich iridium compounds that are active for terminal alkyne dimerization chemistry as well as the addition of carboxylic acids to alkynes. The structures, catalytic and stoichiometric chemistry of some iridium tris-trimethlyphosphine compounds with benzoate ligands are detailed in this paper. The roles that these compounds may play in the catalytic cycles involved in the dimerization of terminal alkynes and the addition of benzoic acid to terminal alkynes are examined and possible mechanisms for these catalytic reactions are proposed.

C[sbnd]O bond activation and subsequent decarbonylation of ester promoted by Fe(PMe3)4

The reactions of 8-quinolinyl esters with iron(0) complex supported by trimethylphosphine ligands afforded four hexa-coordinate chelate-[C,N] iron(II) carbonyl complexes 5–8 via CacylO bond activation and subsequent decarbonylation. Complexes 5–8 were characterized through IR, 1H NMR, 31P NMR and elemental analysis. The crystal structures of complexes 5–8 were determined by X-ray diffraction.

2,6-Bis(diphenylphosphinooxy)phenyl]bis(trimethylphosphine)cobalt(I)

The title compound, [Co(C30H23O2P2)(C3H9P)2], was synthesized by the addition of a Co(PMe3)4 solution to (PPh2O)2C6H4. The CoI atom displays a trigonal-bipyramidal geometry with the two P atoms of the ‘PCP’ pincer ligand and the P atom of one of the trimethyl phosphine ligands forming the basal plane, whereas the metalated C atom and the P atom of the second phospine ligand occupy the apical sites. The Co—C distance is 1.961 (2) Å and the C—Co—P angle is 171.96 (6)°.

Imine-assisted C–F bond activation using low-valent cobalt compounds supported by trimethylphosphine ligands and formation of novel organic fluorides

A cyclometalation reaction involving C-F bond activation at a cobalt(i) center with an aldazine-N atom as anchoring group affords ortho-chelated cobalt(iii) complexes containing a [C-Co-F] fragment [CoFMe(PMe(3))(2){(C(6)H(3)F-ortho)CH[double bond, length as m-dash]N-R}] 5-8. Under similar reaction conditions π-coordinated cobalt(0) complexes [Co(PMe(3))(3)((C(6)H(3)F-ortho)CH[double bond, length as m-dash]N-R)] 12-14 were formed when [Co(PMe(3))(4)], instead of [CoMe(PMe(3))(4)], was applied. C-F bond activation did not occur. Carbonylation of complexes 6-8 delivered novel organic fluorides 15-17. A proposed formation mechanism of the novel organic fluorides with demetallation and carbonylation of complexes 6-8 by CO is discussed with experimental support. As important intermediates, an acetyl cobalt complex, [CoFMeC[double bond, length as m-dash]O(PMe(3))(2){(C(6)H(3)F-ortho)CH[double bond, length as m-dash]N-R}] 20, and a 19-electron cobalt(0) complex, Co(CO)(3)(PMe(3))(2)21, were structurally characterized. The crystal and molecular structures of complexes 5, 6, 8, 12, 20 and 21 were determined by X-ray diffraction.

Synergistic Effect of a Low-Valent Cobalt Complex and a Trimethylphosphine Ligand on Selective C−F Bond Activation of Perfluorinated Toluene

The aryne cobalt complex [Co(4-CF3-η2-C6F3)(PMe3)3] (1) was formed from the reaction of [Co(PMe3)4] and perfluorinated toluene through selective activation of two C−F bonds of perfluorotoluene. A m...

Activation of sp3 Carbon−Hydrogen Bonds by Cobalt and Iron Complexes and Subsequent C−C Bond Formation

The sp3 C−H bond activation induced by CoMe(PMe3)4 and FeMe2(PMe3)4 was investigated. C(sp3)-cyclometalated complexes, based on diphosphinito PCP ligand (Ph2POCH2)2CH2, Co{(Ph2POCH2)2CH}(PMe3)2 (1), and Fe{(Ph2POCH2)2MeC}(H)(PMe3)2 (2), were obtained under mild conditions. Iodomethane is oxidatively added to 1, affording Co{(Ph2POCH2)2CH}(PMe3)(Me)(I) (3). Monocarbonylation of the hydrido-iron complex 2 occurs with substitution of a trimethylphosphine ligand trans to the hydrido ligand, affording Fe{(Ph2POCH2)2MeC}(H)(CO)(PMe3) (4). The reaction of 2 with phenylacetylene delivered the demetalated new diphosphine ligand (Ph2POCH2)2CHCH3 (6) and bis(phenylethinyl)iron complex Fe(PhCC)2(PMe3)4 (5). The new complexes 1−4 were characterized by spectroscopic methods and by X-ray diffraction analysis.

Biomimetic Model Featuring the NH Proton and Bridging Hydride Related to a Proposed Intermediate in Enzymatic H2 Production by Fe-Only Hydrogenase

Iron azadithiolate phosphine-substituted complex and its protonated species featuring the NH proton and/or bridging Fe hydride, [Fe(2)(mu-S(CH(2))(2)N(n)Pr(H)(m)(CH(2))(2)S)(mu-H)(n)(CO)(4)(PMe(3))(2)](2)((2m+2n)+) (1, m = n = 0; [1-2H(N)](2+), m = 1, n = 0; [1-2H(N)2H(Fe)](4+), m = n = 1), are prepared to mimic the active site of Fe-only hydrogenase. X-ray crystallographic analyses of these three complexes reveal that two diiron subunits are linked by two azadiethylenethiolate bridges to construct a dimer-of-dimer structure. (31)P NMR spectroscopy confirms two trimethylphosphine ligands within the diiron moiety are arranged in the apical/basal configuration, which is consistent with the solid-state structural characterization. Deprotonation of the NH proton in [1-2H(N)](2+) and [1-2H(N)2H(Fe)](4+) occurs in the presence of triethanolamine (TEOA), which generates 1 and [1-2H(Fe)](2+), respectively. Deprotonation of the Fe hydride is accomplished by addition of bistriphenylphosphineimminium chloride ([PPN]Cl). It is observed that the Fe hydride species, [1-2H(Fe)](2+), is a kinetic product which converts to its thermodynamically stable tautomer, [1-2H(N)](2+), in solution, as evidenced by IR and NMR spectroscopy. The pK(a) values of the aza nitrogen and the diiron sites are estimated to be 8.9-15.9 and <8.9, respectively. [1-2H(N)2H(Fe)](4+) has been observed to evolve H(2) electrocatalytically at a mild potential (-1.42 V vs Fc/Fc(+)) in CH(3)CN solution. Catalysis of [1-2H(N)2H(Fe)](4+) is found to be as efficient as that of the related diiron azadithiolate complexes. In the absence of a proton source, [1-2H(N)2H(Fe)](4+) undergoes four irreversible reduction processes at -1.26, -1.42, -1.82, and -2.43 V, which are attributed to the reduction events from [1-2H(N)2H(Fe)](4+), [1-2H(Fe)](2+), [1-2H(N)](2+), and 1, respectively, according to bulk electrolysis and voltammetry in combination of titration experiments with acids.

A Synthetic Model for the Inhibition of Glutathione Peroxidase by Antiarthritic Gold Compounds

In this paper, inhibition of the glutathione peroxidase activity of two synthetic organoselenium compounds, bis[2-(N,N-dimethylamino)benzyl]diselenide (5) and bis[2-(N,N-dimethylamino)benzyl]selenide (9), by gold(I) thioglucose (1), chloro(triethylphosphine)gold(I), chloro(trimethylphosphine)gold(I), and chloro(triphenylphosphine)gold(I) is described. The inhibition is found to be competitive with respect to a peroxide (H(2)O(2)) substrate and noncompetitive with respect to a thiol (PhSH) cosubstrate. The diselenide 5 reacts with PhSH to produce the corresponding selenol (6), which upon treatment with 1 equiv of gold(I) chlorides produces the corresponding gold selenolate complexes 11-13. However, the addition of 1 equiv of selenol 6 to complexes 11-13 leads to the formation of bis-selenolate complex 14 by ligand displacement reactions involving the elimination of phosphine ligands. The phosphine ligands eliminated from these reactions are further converted to the corresponding phosphine oxides (R(3)P=O) and selenides (R(3)P=Se). In addition to the replacement of the phosphine ligand by selenol 6, an interchange between two different phosphine ligands is also observed. For example, the reaction of complex 11 having a trimethylphosphine ligand with triphenylphosphine produces complex 13 by phosphine interchange reactions via the formation of intermediates 15 and 16. The reactivity of selenol 6 toward gold(I) phosphines is found to be similar to that of selenocysteine.

8-(Diphenylphosphanyl)naphthyl-κ2C1,P](phenylethynyl)tris(trimethylphosphane-κP)iron(II)

The title compound, [Fe(C8H5)(C22H16P)(C3H9P)3], was synthesized by the addition of phenyl­ethine to a solution of the parent methyl iron complex Fe(CH3){P(C6H5)2(C10H6)}(PMe3)3 at 213 K, accompanied by evolution of methane. The coordination around the iron center can be described as slightly distorted octa­hedral [Fe—P 2.2485 (12)–2.2902 (12) Å; Fe—C 1.918 (5), 2.015 (4) Å], with a meridional arrangement of the trimethyl­phosphine ligands and the introduced terminal alkinyl-ligand trans to the P(Ph)2-anchoring group.

C–H activation of diphenylphosphinoaryl-derivatives with dimethyltetrakis(trimethylphosphine)iron(II)

Fe(CH 3) 2(PMe 3) 4 reacts with 1-(diphenylphosphino)naphthalene or benzyldiphenylphosphine within 4 h at 20 °C to give the novel metallated methyl iron complexes Fe(CH 3){P(C 6H 5) 2(C 10H 6)}(PMe 3) 3 ( 1) and Fe(CH 3){(C 6H 4)CH 2P(C 6H 5) 2}(PMe 3) 3 ( 3), respectively, via selective activation of the C–H bond of the pre-chelating ligands. The complexes are thermally unstable releasing metal through a reductive elimination of the aromatic backbone and leading to a C,C-coupling product that is regiospecifically methylated, namely 8-methyl(diphenylphosphino)naphthalene ( 2). Carbonylation (1 bar, 20 °C, 1 h) of complex 1 effects monosubstitution of a trimethylphosphine ligand trans to the metallated 8-C atom to afford Fe(CH 3){P(C 6H 5) 2(C 10H 6)}(CO)(PMe 3) 2 ( 4). The remaining methyl group in the parent complex 1 reacts with trimethylsilylethyne and tert-butylethyne affording the new complexes 5 and 6 bearing an alkynyl substituent trans to the diphenylphosphino anchoring group. The complexes 1 and 3– 6 are diamagnetic and possess octahedral coordination geometry. All novel complexes were fully characterized by spectroscopic methods and by X-ray diffraction.

Chemical vapor deposition of amorphous ruthenium–phosphorus alloy films

Chemical vapor deposition growth of amorphous ruthenium–phosphorus films on SiO 2 containing ∼ 15% phosphorus is reported. cis-Ruthenium(II)dihydridotetrakis-(trimethylphosphine), cis-RuH 2(PMe 3) 4 (Me = CH 3) was used at growth temperatures ranging from 525 to 575 K. Both Ru and P are zero-valent. The films are metastable, becoming increasingly more polycrystalline upon annealing to 775 and 975 K. Surface studies illustrate that demethylation is quite efficient near 560 K. Precursor adsorption at 135 K or 210 K and heating reveal the precursor undergoes a complex decomposition process in which the hydride and trimethylphosphine ligands are lost at temperatures as low at 280 K. Phosphorus and its manner of incorporation appear responsible for the amorphous-like character. Molecular dynamics simulations are presented to suggest the local structure in the films and the causes for phosphorus stabilizing the amorphous phase.

Synthesis and Characterization of Cationic Tungsten(V) Methylidynes

Cationic tungsten(V) methylidynes [L4W(X)[triple bond]CH]+[B(C6F5)4]- [L = PMe3, 0.5dmpe (dmpe = Me2PCH2CH2PMe2), X = Cl, OSO2CF3] have been prepared in high yield by a one-electron oxidation of the neutral tungsten(IV) methylidynes L4W(X)[triple bond]CH with [Ph3C]+[B(C6F5)4]-. The ease and reversibility of the one-electron oxidation of L4W(X)[triple bond]CH were demonstrated by cyclic voltammetry in tetrahydrofuran (E1/2 is approximately -0.68 to -0.91 V vs Fc). The paramagnetic d1 (S = 1/2) complexes were characterized in solution by electron spin resonance (g = 2.023-2.048, quintets due to coupling to 31P) and NMR spectroscopy and Evans magnetic susceptibility measurements (mu = 2.0-2.1 muB). Single-crystal X-ray diffraction showed that the cationic methylidynes are structurally similar to the neutral precursor methylidynes. In addition, the neutral (PMe3)4W(Cl)[triple bond]CH was deprotonated with a strong base at the trimethylphosphine ligand to afford (PMe3)3(Me2PCH2)W[triple bond]CH, a tungsten(IV) methylidyne complex that features a (dimethylphosphino)methyl ligand.

Theoretical analysis of bis(ethylene) complexes of molybdenum and tungsten

Density functional calculations on the zero-valent bis(ethylene) trans-[M(C 2H 4) 2(PH 3) 4] model complexes and the actual trans-[M(C 2H 4) 2(PMe 3) 4] (M=Mo, W) compounds were carried out at the BPW91 level of theory. The experimentally characterised molecular structures of both molybdenum and tungsten complexes were properly reproduced by the energy optimised geometries only when the trimethylphosphine ligands were used. The experimentally observed ruffling of the phosphine ligands was not detected when the simplified model was considered. This discrepancy was interpreted as a consequence of different steric interactions between the PH 3 and PMe 3 ligands. The theoretical analysis gives a good account of some chemical properties observed in these compounds. In particular, the low PMe 3 dissociation energies calculated for these compounds are in agreement with the experimental observation of free phosphine dissociation in the solutions of trans-[M(C 2H 4) 2(PMe 3) 4] compounds. The comparison of energy data for PH 3 and PMe 3 complexes corroborates the experimental hypothesis that phosphine dissociation has a steric origin.

Mixed chloride/phosphine complexes of the dirhenium core. 10. Redox reactions of an edge-sharing dirhenium(III) non-metal-metal-bonded complex, Re(2)(mu-Cl)(2)Cl(4)(PMe(3))(4).

Reduction and oxidation reactions of the dirhenium(III) non-metal-metal-bonded edge-sharing complex, Re(2)(mu-Cl)(2)Cl(4)(PMe(3))(4) (1), have been studied. Several new mono- and dinuclear rhenium compounds have been isolated and structurally characterized in the course of this study. Reductions of 1 with 1 and 2 equiv of KC(8) result in an unusual face-sharing complex having an Re(2)(5+) core, Re(2)(mu-Cl)(3)Cl(2)(PMe(3))(4) (2), and a triply bonded Re(II) compound, 1,2,7,8-Re(2)Cl(4)(PMe(3))(4) (3), respectively. Two-electron reduction of 1 in the presence of tetrabutylammonium chloride affords a new triply bonded complex of the Re(2)(4+) core, [Bu(n)()(4)N][1,2,7-Re(2)Cl(5)(PMe(3))(3)] (4). Oxidation of 1 with NOBF(4) yields a Re(IV) mononuclear compound, trans-ReCl(4)(PMe(3))(2) (5). Two isomers of the monomeric Re(III) anion, [ReCl(4)(PMe(3))(2)](-) (6, 7), have been isolated as side products. The crystal structures of compounds 2 and 4-7 have been determined by X-ray crystallography. The Re-Re distance in the face-sharing complex 2 of 2.686(1) A is relatively short. The metal-metal bond length in anion 4 of 2.2354(7) A is consistent with the usual values for the triply bonded Re(2)(4+) core compounds. In addition, a cis arrangement of trimethylphosphine ligands in the starting material 1 is retained upon reduction in the dinuclear products 2-4.