Bridging Diphosphine Ligands Research Articles

Influence of a thioether function in short-bite diphosphine ligands on the nature of their silver complexes: structure of a trinuclear complex and of a coordination polymer

New cationic Ag(I) complexes were prepared by reaction of AgBF4 with two thioether-functionalized bis(diphenylphosphino)amine ligands, Ph2PN(p-ArSMe)PPh2 (L1) and Ph2PN(n-PrSMe)PPh2 (L2), and compared with those obtained from the unfunctionalized ligands Ph2PN(Ph)PPh2 (L3) and Ph2PN(n-Bu)PPh2 (L4), respectively. The complex [Ag3(μ3-Cl)2(μ2-L1-P,P)3](BF4) (1·BF4) contains a triangular array of Ag centres supported by three bridging L1 ligands and two triply-bridging chlorides. In contrast, ligand L2 led to the coordination polymer [{Ag2(μ3-L2,-P,P,S)2(MeCN)2}{Ag2(μ2-L2-P,P)2(MeCN)2}(BF4)4]n (2) in which the tethered thioether group connects intermolecularly a Ag2 unit to the diphosphine bridging the other Ag2 unit. With L3 and L4, two similar complexes were obtained, [Ag2(μ2-L3)(BF4)2] (3) and [Ag2(μ2-L4)(BF4)2] (4), respectively, with bridging diphosphine ligands and a BF4 anion completing the coordination sphere of the metal. Complexes 1·BF4·CH2Cl2, 2·THF, 3·3CH2Cl2 and 4 have been fully characterized, including by single crystal X-ray diffraction.

New Pd(II) Binuclear Complexes as Effective Catalysts in Oxidative-Heck Reaction Using Arylboronic Acid Derivatives

A series of new binuclear Pd(II) complexes based on chelating diimines and bridging diphosphine or diimine ligands have been synthesized and characterized successfully. The formula of the new complexes are [Pd2(mbyp)2(DPA)2](PF6)4 (1), [Pd2(mbyp)2(DPE)2] (PF6)4 (2), [Pd2(mbyp)2(4,4-byp)2] (PF6)4 (3), [Pd2(mbyp)2(t-pye)2] (PF6)4 (4) [mbyp = 4,4′-dimethyl-2,2′-bipyridine, DPA = 1,2-bis(diphenylphosphino)acetylene, DPE = 1,2-bis(diphenylphosphino)ethylene, 4,4-byp = 4,4′-bipyridine, and t-ype = trans 1,2-bis(4-pyridyl)ethylene)]. The catalytic activities of the new complexes have been investigated in the coupling of arylboronic acid derivatives to various olefins. Results obtained showed interesting catalytic activities and chemoselectivities for the new complexes in the coupling reactions to produce the conjugate addition and heck coupling products under free base or oxidant conditions.

Silver(I) macrocycles and coordination polymers containing pyridyl carboxylate and phosphine ligands

Six Ag(I) coordination compounds containing pyridyl carboxylates [namely of trans-3-(3′-pyridyl) acrylic acid (3-PAH), trans-3-(4′-pyridyl) acrylic acid (4-PAH), and 4-trans-2-(pyrid-4-yl-vynyl) benzoic acid (Hpvba)] and phosphine ligands [namely triphenylphosphine, 1,1-bis-(diphenylphosphino) methane (dppm), 1,2-bis-(diphenylphosphino) ethane (dppe) and 1,3-bis-(diphenylphosphino) propane (dppp)] are described. By varying the combination of silver salts and bridging ligands, we have synthesized 0D, 1D, 2D and 3D architectures of silver(I) coordination compounds and polymers. The coordination environments and geometries around Ag(I) are highly dependent on the coordination mode of carboxylate ‘O’ (whether monodentate, μ1,1 or μ1,3). On the other hand, the dimensionality of the coordination polymers depends on the bridging diphosphine ligands and shape of the pyridyl carboxylates.

Intermolecular Hydroacylation: High Activity Rhodium Catalysts Containing Small-Bite-Angle Diphosphine Ligands

Readily prepared and bench-stable rhodium complexes containing methylene bridged diphosphine ligands, viz. [Rh(C(6)H(5)F)(R(2)PCH(2)PR'(2))][BAr(F)(4)] (R, R' = (t)Bu or Cy; Ar(F) = C(6)H(3)-3,5-(CF(3))(2)), are shown to be practical and very efficient precatalysts for the intermolecular hydroacylation of a wide variety of unactivated alkenes and alkynes with β-S-substituted aldehydes. Intermediate acyl hydride complexes [Rh((t)Bu(2)PCH(2)P(t)Bu(2))H{κ(2)(S,C)-SMe(C(6)H(4)CO)}(L)](+) (L = acetone, MeCN, [NCCH(2)BF(3)](-)) and the decarbonylation product [Rh((t)Bu(2)PCH(2)P(t)Bu(2))(CO)(SMePh)](+) have been characterized in solution and by X-ray crystallography from stoichiometric reactions employing 2-(methylthio)benzaldehdye. Analogous complexes with the phosphine 2-(diphenylphosphino)benzaldehyde are also reported. Studies indicate that through judicious choice of solvent and catalyst/substrate concentration, both decarbonylation and productive hydroacylation can be tuned to such an extent that very low catalyst loadings (0.1 mol %) and turnover frequencies of greater than 300 h(-1) can be achieved. The mechanism of catalysis has been further probed by KIE and deuterium labeling experiments. Combined with the stoichiometric studies, a mechanism is proposed in which both oxidative addition of the aldehyde to give an acyl hydride and insertion of the hydride into the alkene are reversible, with the latter occurring to give both linear and branched alkyl intermediates, although reductive elimination for the linear isomer is suggested to have a considerably lower barrier.

Bisxantphos: Stereoselective synthesis and coordination behaviour of a new class of cyclic double bridged diphosphines

A new class of cyclic double bridged diphosphine ligands was developed and the coordination properties are described. The reaction of 4,5-dilithioxanthene with dichlorophenylphosphine gave a cyclic double bridged diphosphine ligand based on two xanthene backbones ( 4) as a single stereoisomer. X-ray crystal structure determination revealed that the groups bridging the two phosphorus atoms are arranged in a syn-disposition. This new cyclic bisxantphos structure was modified with bulky residues at the third substituent of the phosphorus atoms, thus forming cavity-shaped ligands.

Influences on the rotated structure of diiron dithiolate complexes: electronic asymmetry vs. secondary coordination sphere interaction

In the pursuit of a "rotated" structure, and exploration of the influence of the aza nitrogen lone pair, the Fe(I)Fe(I) model complexes wherein two Fe(CO)(3-x)P(x) moieties are significantly twisted from the ideal configuration (torsion angle >30°) are reported. [Fe(2)(μ-S(CH(2))(2)N(i)Pr(X)(CH(2))(2)S)(CO)(4)(κ(2)-dppe)](2)(2+) (X = H, 4; Me, 5) prepared from protonation and methylation, respectively, of [Fe(2)(μ-S(CH(2))(2)N(i)Pr(CH(2))(2)S)(CO)(4)(κ(2)-dppe)](2), 1, possess Φ angles of 34.1 and 35.4° (av.), respectively. Such dramatic twist is attributed to asymmetric substitution within the Fe(2) unit in which a dppe ligand is coordinated to one Fe site in the κ(2)-mode. In the presence of the N···C(CO(ap)) interaction, the torsion angle is decreased to 10.8°, suggesting availability of lone pairs of the aza nitrogen sites within 1 is in control of the twist. Backbones of the bridging diphosphine ligands also affect distortion. For a shorter ligand, the more compact structure of [Fe(2)(μ-S(CH(2))(2)N(i)Pr(CH(2))(2)S)(μ-dppm)(CO)(4)](2), 7, is formed. Dppm in a bridging manner allows achievement of the nearly eclipsed configuration. In contrast, dppe in [Fe(2)(μ-S(CH(2))(2)N(i)Pr(CH(2))(2)S)(μ-dppe)(CO)(4)](2), 6, could twist the Fe(CO)(3-x)L(x) fragment to adopt the least strained structure. In addition, the NC(CO(ap)) interaction would direct the twist towards a specific direction for the closer contact. In return, the shorter N···C(CO(ap)) distance of 3.721(7) Å and larger Φ angle of 26.5° are obtained in 6. For comparison, 3.987(7) Å and 3.9° of the corresponding parameters are observed in 7. Conversion of (μ-dppe)[Fe(2)(μ-S(CH(2))(2)N(i)Pr(CH(2))(2)S)(CO)(5)](2), 2, to complex 1 via an associative mechanism is studied.

Assembly of Symmetrical or Unsymmetrical Cyclometalated Organoplatinum Complexes through a Bridging Diphosphine Ligand

The cyclometalated complexes [Pt(ppy)Ar(SMe2)] or [Pt(bhq)Ar(SMe2)], where ppyH = 2-phenylpyridine, bhqH = benzo[h]quinoline, and Ar = 4-tolyl or 4-anisyl, react with bis(diphenylphosphino)methane, dppm, in a 1:1 ratio to give the corresponding complexes [Pt(ppy)Ar(κ1-dppm)] and [Pt(bhq)Ar(κ1-dppm)], in which the dppm ligands are monodentate, or in a 2:1 ratio to give the symmetrical binuclear complexes [{Pt(ppy)Ar}2(μ-dppm)] and [{Pt(bhq)Ar}2(μ-dppm)], in which the dppm ligands are bridging bidentate. Most remarkably, the reaction of [Pt(ppy)Ar(SMe2)] with [Pt(bhq)Ar′(κ1-dppm)] or of [Pt(bhq)Ar′(SMe2)] with [Pt(ppy)Ar(κ1-dppm)] occurs selectively to give the unsymmetrical bridged complexes [(ppy)ArPt(μ-dppm)PtAr′(bhq)]. An example of each structural type has been characterized crystallographically, and it is shown that some of the bhq complexes undergo supramolecular self-assembly through π-stacking.

Spectroscopic and X-ray Diffraction Data on Three Novel Trimetallic Clusters from Thermally Promoted Ligand Substitution in the Tetrahedrane Clusters MeCCo2MoCp(CO)8 and PhCCo2Mo(η5-C5H4CHO)(CO)8

The reaction between the ethylidyne-substituted cluster MeCCo2MoCp(CO)8 (1) and the diphosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) in refluxing CH2Cl2 has been investigated and found to afford the new mixed-metal clusters MeCCo2MoCp(CO)6[trans-2,3-bis(diphenylphosphino)succinic anhydride] (2) and Co2MoCp(CO)5[μ-C(Me)C=C(PPh2)C(O)OC(O)](μ-PPh2) (3), with the latter cluster representing the principal reaction product. Refluxing 1 with bma in either 1,2-dichloroethane or toluene yields only 3. The tetrahedrane cluster PhCCo2Mo(η5-C5H4CHO)(CO)8 (4), which contains a formyl-substituted cyclopentadienyl ring, has also been examined with added bma in refluxing CH2Cl2 and found to give only Co2Mo(η5-C5H4CHO)(CO)5[μ-C(Ph)C=C(PPh2)C(O)OC(O)](μ-PPh2) (5). All three products have been isolated and characterized spectroscopically in solution, and each molecular structure has been determined by X-ray crystallography. Cluster 2 contains a bridging diphosphine ligand with a succinic anhydride ring that results from the formal reduction of the maleic anhydride platform of the bma ligand, while clusters 3 and 5 each exhibit triangular Co2Mo cores, whose one face is capped by a 6e- C(R)C=C(PPh2)C(O)OC(O) [where R = Me (3), Ph (5)] ligand. The observed substitution products are discussed as a function of the capping carbyne group, ancillary polyene ligand, and related derivatives prepared by our groups. Thermolysis of the mixed-metal cluster MeCCo2MoCp(CO)8 (1) with bma in CH2Cl2 furnishes the new clusters MeCCo2MoCp(CO)6[trans-2,3-bis(diphenylphosphino)succinic anhydride] (2) and Co2MoCp(CO)5[μ-C(Me)C=C(PPh2)C(O)OC(O)](μ-PPh2) (3) as the minor and major products, respectively. The reaction between bma and the related benzylidyne-capped cluster PhCCo2Mo(η5-C5H4CHO)(CO)8 (4), which contains a formyl-substituted cyclopentadienyl ring, has also been examined and found to afford only Co2Mo(η5-C5H4CHO)(CO)5[μ-C(Ph)C=C(PPh2)C(O)OC(O)](μ-PPh2) (5) in moderate yield.

A tetranuclear molecular rectangle from four gold(I) atoms linked by dicarbene and diphosphine ligands

A tetranuclear molecular rectangle consisting of two bridging dicarbene ligands and two bridging diphosphine ligands was prepared by connection of two dinuclear gold(I) complexes with 1,2-bis(diphenylphosphino)ethane.

The chemistry of N-benzylidene-1,4-phenylenediamine palladacycles: The crystal and molecular structure of the first tetranuclear palladacycle with bridging Ph2PCH2PPh2 ligands

Abstract The reaction of the tetranuclear halide-bridged complexes 1−2(a−d) with Ph2PCH2PPh2 (dppm) or Ph2PC( CH2)PPh2 (vdpp) in 1:2 molar ratio and NH4PF6 afforded the novel tetarnuclear palladacycles 3−6 (a, c, d) as 1:2 electrolytes with bridging diphosphine and halogen ligands. The structure of 4a has been determined by X-ray diffraction analysis, and represents the first example of a tetranuclear palladacycle with bridging dppm and halogen ligands. Reaction of 1−2(a−d) with (Ph2PCH2CH2)2PPh (triphos) in 1:2 molar ratio gave 7(a−d) bearing two pentacoordinated palladium atoms. The structure of 7a, as determined by X-ray diffraction analysis, shows the distorted square pyramidal geometry around the metal centers. Treatment of 1−2(a−d) with dppm, vdpp or Ph2PN(Me)PPh2 (dppma) in 1:4 molar ratio gave the dinuclear palladacycles 8−10(a−d) with a chelating diphosphine ligand at each metal center; further treatment of 9(a−c) with the nucleophiles pyrrolidine, piperidine, morpholine or 4-methyl-piperidine gave the Michael addition derivatives 11−12(a−c), 13b, 13c and 14c, promoted by the withdrawing effect of the palladacycle which activates the C CH2 double bond.

W/Cu(Ag)/S complexes containing bridging diphosphine ligands: Synthesis, structures and optical properties

The substitution reactions of [Et 4N] 2[WOS 3MCN] (M = Cu, Ag) with dppe (dppe = 1,2-bis(diphenylphosphino) ethane) in DMF afforded a tetranuclear cluster [Et 4N] 2[WOS 3Cu(dppe)] 2 · H 2O ( 1) and a polymer [WEE′S 2Ag(dppe)] 2 · CH 3CN ( 3) (E = 0.636S + 0.364O, E′ = 0.581O + 0.419S), respectively. Treatment of 1 with AgI at elevated temperature yielded polymeric complex [WS 4Cu 2(dppe) 2] n ( 2). X-ray single crystal structural analyses revealed that in both 1 and 2, the W/Cu/S cluster units are linked by two dppe ligands to form a 10-membered [–Cu–P–C–C–P–] 2 ring. In the polymeric structure of 2, the W and Cu atoms form a helical chain whereas in 3 the cluster units (WEE′S 2Ag) are bridged by dppe ligands affording a zig-zag chain structure. The optical absorption spectra and the solid-state photoluminescent properties of the title complexes are also studied.

Polymer and cage-type structures in silver(I) complexes with heterocyclic thiones and bridging diphosphine ligands. Crystal structures of [Ag(μ-dpppent)(tHpymtH)(ONO 2)] n and [Ag 2(μ- trans-dppen) 3(pymtH) 2](NO 3) 2 · CH 3CN

Reaction of silver(I) nitrate with equimolar amounts of the rigid diphos ligand trans-1,2-bis(diphenylphosphino)ethene ( trans-dppen) and some heterocyclic thiones (L) in acetonitrile/methanol solvent gave rise to triply-bridged coordination cages [Ag 2(μ 2- trans-dppen) 3L 2](NO 3) 2. On the other hand, the complexes produced when using the flexible 1,5-bis(diphenylphosphino)pentane (dpppent) turned out to be diphosphine-bridged polymers of the type [Ag(μ 2-dpppent)(L)(ONO 2)] n with the diphosphine ligand acting as bridge between two pseudo-tetrahedraly coordinated metal centres. The structures of one representative for each of the two aforementioned series of complex compounds, namely, [Ag 2(μ 2- trans-dppen) 3(pymtH) 2](NO 3) 2 (pymtH = pyrimidine-2-thione) and [Ag(μ 2-dpppent)(tHpymtH) (ONO 2)] n (tHpymtH = tetrahydropyrimidine-2-thione) have been established by single-crystal X-ray diffraction.

Syntheses, crystal structures and characterization of a series of heterothiometallic gold(I) complexes containing bridging diphosphine ligands

A series of tetranuclear heterothiometallic clusters [Et 4N] 2[(MS 4) 2Au 2(dppe)] ( 1: M = Mo; 2: M = W), [PPh 4] 2[(MoOS 3) 2Au 2(dppe)] ( 3), [Et 4N] 2[(WOS 3) 2Au 2(dppe)] ( 4) (dppe = 1,2-bis(diphenylphosphino)ethane), [Et 4N] 2[(MS 4) 2Au 2(dppf)] ( 5: M = Mo; 6: M = W) and [Et 4N] 2[(MOS 3) 2Au 2(dppf)] ( 7: M = Mo; 8: M = W) (dppf = 1,1′-bis(diphenylphosphino)ferrocene) have been synthesized from the reactions of thiometalates [MXS 3] 2− (M = Mo or W, X = O or S), AuCl(SC 4H 8) and dppe or dppf. The crystal structures of the complexes 2, 4 and 6 have been determined by single-crystal X-ray diffraction studies. In the molecular structures of these complexes, the two linear M/Au/S units are linked via bidentate phosphines dppe or dppf. The complexes have been fully characterized by IR, UV–vis as well as elemental analyses. These clusters all exhibit room-temperature luminescence in the solid state.

Binuclear dimethylplatinum (II) complexes each containing monodentate phosphine ligands and a bridging diphosphine ligand X(PPh 2) 2, X = CH 2 or NH. Molecular structure of cis, cis-[Me 2(pyPh 2P)Pt(μ-Ph 2PNHPPh 2)Pt(PPh 2py) Me 2] · 2CH 2Cl 2

Displacement of the labile bridging SMe 2 ligand in the organodiplatinum(II) complexes cis, cis-[Me 2Pt(μ-SMe 2){μ-X(PPh 2) 2}PtMe 2], in which X(PPh 2) 2 is either bis(diphenylphosphino)amine [dppa (X = NH)], 1a, or bis(diphenylphosphino)methane [dppm (X = CH 2)], 1b, with 2 equiv of some monodentate phosphine ligands, L, gave a series of organodiplatinum(II) complexes with general formula cis, cis-[Me 2LPt(μ-dppa)PtLMe 2][L = PPh 3, 2a, PPh 2py(2-diphenylphosphinopyridine, PN), 3a, or P(O- i Pr) 3, 4a] or cis, cis-[Me 2LPt(μ-dppm)PtLMe 2][L = PPh 3, 2b, PN, 3b, or P(O- i Pr) 3, 4b] in good yields. In these complexes the two metallic centers are held together by only one bridging diphosphine ligand with no metal–metal bond. When L is PPh 2Me or PPhMe 2, the diplatinum(II) complexes are split to the corresponding monomers, [PtMe 2{X(PPh 2) 2}] and cis-[PtMe 2L 2]. No reaction was observed when L is pyridine or SMe 2. The complexes were fully characterized using multinuclear NMR ( 1H, 13C, 31P and 195Pt) methods, and the structure of cis, cis-[Me 2(pyPh 2P)Pt(μ-Ph 2PNHPPh 2)Pt(PPh 2py)Me 2] · 2CH 2Cl 2, 3a, has been determined crystallographically.

Macrocyclic Gold(I) Complexes with Bridging Diacetylide and Diphosphine Ligands

Abstract The new dialkynyldigold(I) complexes [Ar(OCH2C≡CAu)2]n {Ar = 1,4-C6H4(CMe2-4-C6H4)2, 4,4’-C6H4C6H4 and 1,5-C10H6} react with diphosphines LL = Ph2P(CH2)nPPh2 (n = 1 to 6) and trans-Ph2PCH=CHPPh2 to give luminescent macrocyclic digold(I) or tetragold(I) complexes with bridging diphosphine and diacetylide ligands. The digold(I) complex [1,4-C6H4(CMe2-4- C6H4OCH2C≡CAu)2(μ-LL)], with LL = trans-Ph2PCH=CHPPh2, forms a 28-membered ring, and the rings associate through aurophilic bonding in the solid state. In contrast, the tetragold(I) complex [4,4’-C6H4C6H4(OCH2C≡CAu)2(μ-LL)], with LL = Ph2PCH2PPh2, forms a more rigid 42-membered ring.

Structure and Luminescence of a Dinuclear Copper Complex Bridged by a Diphosphine Ligand

Abstract A new dinuclear copper(I) complex containing two 2,9-dimethylphenanthroline ligands and a bridging diphosphine ligand has been prepared. The structure of the complex was characterized by X-ray crystallography. A considerable blue shift was observed for the solid-state photoluminescence and absorption spectra of the complex as compared with the mononuclear mixed-ligand complex.

Reaction of 1,2-bis(diphenylphosphino)cyclobutenedione (bpcbd) with fac-BrRe(CO)3(THF)2: X-ray diffraction structure of the dimeric complex [BrRe(CO)3]2(bpcbd) Ch2Cl2

Treatment of the diphosphine ligand 1,2-bis(diphenylphosphino)cyclobutenedione (bpcbd) with the THF adduct fac-BrRe(CO)3(THF)2 at room temperature furnishes the new dirhenium compound [BrRe(CO)3]2(bpcbd) instead of the expected mononuclear compound fac-BrRe(CO)3(bpcbd). [BrRe(CO)3]2(bpcbd) was characterized in solution by IR spectroscopy, and the solid-state structure was solved by X-ray crystallography. [BrRe(CO)3]2(bpcbd), as the CH2Cl2 solvate, crystallizes in the space group P\(\overline {\text{1}} \), a = 11.173(1), b = 13.362(1), c = 15.250(1) A, α = 108.973(7)°, β = 99.477(8)°, γ = 110.466(7)°, V = 1915.0(3) A3, Z = 2, and dcalc = 2.143 g-cm−3. The structure of [BrRe(CO)3]2(bpcbd) consists of two rhenium centers that are six-coordinate and possess nearly ideal octahedral geometry. The two Re(CO)3 units are linked together by the bridging diphosphine ligand and two bridging bromide groups.

The structure and dynamic behaviour of disubstituted derivatives of [Rh 6(CO) 16] containing bidentate phosphorus ligands

The solution structure and dynamic behaviour of [Rh 6(CO) 14(μ,η 2-dppm)] ( 1), [Rh 6(CO) 14(μ,η 2-dppe)] ( 2) and [Rh 6(CO) 14(μ,η 2-dppe f)] ( 3) containing bridging diphosphine ligands have been examined using 1D 13C, 31P and 2D 13C–{ 103Rh}, 31P–{ 103Rh} HMQC and 13C EXSY NMR techniques. It has been shown that the solid state structure of these clusters remains unchanged in solution, including the close non-bonding intramolecular interactions of the perfluorinated phenyl rings with adjacent terminal carbonyls. In solution, two different dynamic processes have been found: for 2 and 3, the P–CH 2–CH 2–P chain of the coordinated dppe and dppe f is non-rigid and this leads to the interchange of the two enantiomeric forms of the clusters through a ‘rocking’ motion of the bridging diphosphine; the rate of this exchange depends strongly on the non-bonding van der Waal's interactions between the phosphorus substituents and adjacent carbonyl ligands which results in substantially slower dynamics for 3 because the steric requirements of the fluorinated phenyl rings considerably hinder this racemization. The second type of dynamics found in 1– 3 involves exchange of terminal/face-bridging CO's associated with the unsubstituted rhodium atoms. Regioselectivity of these exchanges is essentially similar for all three clusters, whereas the rates of these CO-exchanges are substantially higher in 3, which may be due to the lower net donicity of the per-fluorinated diphosphine.

Bridging and chelating diphosphine ligands in Ru3(μ-H)(μ-N=CPh2)(CO)8(P—P). X-ray diffraction structures of Ru3(μ-H)(μ-N=CPh2)(CO)8(dmpe) and Ru3(μ-H)(μ-N=CPh2)(CO)8(bpcd)

Treatment of the azavinylidene-bridged cluster Ru3(μ-H)(μ-N=CPh2)(CO)10 (1) with the diphosphine ligand bis(dimethylphosphino)ethane (dmpe) gives Ru3( μ-H)(μ-N=CPh2)(CO)8(dmpe) (2) in moderate yield, while the ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) reacts with Ru3( μ-H)(μ-N=CPh2)(CO)10 in the presence of Me3NO to furnish Ru3( μ-H)(μ-N=CPh2)(CO)8(bpcd) (3) in low yield. Each new cluster has been isolated and characterized in solution by IR and NMR (1H and 31P) spectroscopies, and the coordination mode exhibited by the ancillary diphosphine ligand in 2 and 3 has been established by X-ray crystallography. Ru3( μ-H)(μ-N=CPh2)(CO)8(dmpe) crystallizes in the monoclinic space group P2(1)/c, a = 10.791(1) A, b = 16.377(1) A, c = 18.148(1) A, β = 96.675(2)°, V = 3185.3(4) A3, Z = 4, D cacl = 1.791 Mg/m3; R = 0.0360, R w = 0.0866 for 7522 observed reflections with I > 2σ(I). Ru3(μ-H)(μ-N=CPh2)(CO)8(bpcd) crystallizes, as the CH2Cl2 solvate, in the triclinic space group $$P\bar 1$$ , a = 11.956(1) A, b = 14.228(1) A, c = 31.409(3) A, α = 89.377(2)°, β = 79.344(2)°, γ = 77.235(2)°, V = 5118.4(8) A3, Z = 2, D calc = 1.670 Mg/m3; R = 0.0557, R w = 0.1069 for 10977 observed reflections with I > 2σ(I). The structural details of clusters 2 and 3 are contrasted with Ru3(μ-H)(μ-N=CPh2)(CO)7(μ-dppm)(η-dppm), which is the only known structurally characterized phosphine-substituted cluster of this genre.

From chelating to bridging diphosphine ligands in quadruply-bonded bimetallic complexes: a non-dissociative phosphine exchange mechanism

The exchange of phosphine ligands in the bimetallic Mo2Cl4[H2P–(CH2)2–PH2]2 complex was studied by means of DFT calculations with the B3LYP functional. A non-dissociative mechanism was fully characterized (minima, transition states) for the isomerization reaction, which transforms the α isomer, with two chelating diphosphines, into the β isomer, with two bridging diphosphines. It involves the non-concerted migration of one end of each diphosphine ligand from one metal center to the other. The computed activation energy (about 30 kcal mol−1) is associated with the jumping of the first phosphine end, which bridges the two metal centers in the transition state structure (TS1).