Dppf Ligand Research Articles

Palladium-Catalyzed Decarboxylative Benzylation of Acetylides and Enolates

Benzylic alkylation of enolates and acetylides has been achieved through the use of a decarboxylative benzylation strategy. Previous research in this area is often limited by the need for extended conjugation in the electrophiles that are coupled. Herein, we report that the use of 1,1'-bis(diphenylphosphino)ferrocene (dppf) ligand allows the coupling of simple benzyl electrophiles with enolates, while the use of XPhos ligand promotes the decarboxylative couplings of propiolates.

General Synthesis of Alkenyl Sulfides by Palladium-Catalyzed Thioetherification of Alkenyl Halides and Tosylates

The cross-coupling reaction of alkenyl bromides with thiols catalyzed by palladium complexes derived from inexpensive dppf ligand is reported. These reactions occur under low catalyst loading and in high yields and display wide scope, including the coupling of bulky thiols and trisubstituted bromoolefins, and functional group tolerance. In addition, the thioetherification of less reactive chloroalkenes and, for the first time, alkenyl tosylates was accomplished using a catalyst generated from CyPF tBu alkylbisphosphine ligand.

Cycloplatinated(ii) complexes bearing 1,1′-bis(diphenylphosphino)ferrocene ligand: biological evaluation and molecular docking studies

Cycloplatinated(ii) complexes containing dppf ligand were prepared. These complexes exhibited high cytotoxicity and apoptosis-inducing activities to human cancer cell lines.

Synthesis, characterization and electrochemical properties of O-alkyldithiophosphate nickel complexes with dppf ligand

Four new O-alkyldithiophosphate nickel complexes [(dppf)Ni(S2P{O}OR)] with dppf ligand (1, R = CH3; 2, R = CH2CH3; 3, R = CH2Ph; 4, R = CH2CH2Ph; dppf = 1,1′-bis(diphenylphosphino)ferrocene) have been synthesized by treatment of (dppf)NiCl2 with (RO)2PS2NH2Et2 in good yields. All the four complexes were characterized by elemental analysis, spectroscopy (IR, UV–Vis, 1H, 13C and 31P NMR), thermogravimetric analysis and single crystal X-ray diffraction. The crystal structures of 1–4 reveal that the nickel atom lies at the center of a slightly distorted square-planar environment and all complexes display CH⋯Ni intramolecular anagostic interactions. Furthermore, the electrochemical properties for 1–4 were also investigated by cyclic voltammetry. The electrochemical studies indicate that all complexes can be used as eletrocatalysts for reduction proton to hydrogen in the presence of trifluoroacetic acid and acetic acid in CH2Cl2 solution, respectively.

Redox Induced Configurational Isomerization of Bisphosphine-Tricarbonyliron(I) Complexes and the Difference a Ferrocene Makes.

The tricarbonyliron (TCFe) complexes Fe(CO)3(dppf) and Fe(CO)3(dppp), where dppf = 1,1'-bis(diphenylphosphino)ferrocene and dppp = 1,3-bis(diphenylphosphino)propane, exhibit redox activity that induces configurational isomerization. The presence of the ferrocenyl (Fc) group stabilizes higher oxidized forms of TCFe. Using spectroelectrochemistry (IR, UV-vis, Mössbauer, and EPR) and computational analysis, we can show that the Fc in the backbone of the dppf ligand tends to form a weak dative bond to the electrophilic TCFeI and TCFeII species. The open shell TCFeI intermediate was stabilized by the distribution of spin between the two Fe centers (Fc and TCFe), whereas lacking the Fc moiety resulted in highly reactive TCFeI species. The [Fe(CO)3(dppf)]+ cation adopts two possible configurations, square-pyramidal (without an Fe-Fe interaction) and trigonal-bipyramidal (containing an Fe-Fe interaction). The two configurations are in equilibrium with the trigonal-bipyramidal configuration being enthalpically favored (ΔH = -7 kJ mol-1). There is an entropic penalty (ΔS = -20 J mol-1) due to tilting of the Cp (cyclopentadienide) rings of the dppf moieties by ∼8°. Additionally, the terminal iron hydride [FeH(CO)3(dppf)]BF4 was formed by protonation with a strong acid (HBF4·Et2O).

Reversible C-H bond activation at a triosmium centre: A comparative study of the reactivity of unsaturated triosmium clusters Os3(CO)8(μ-dppm)(μ-H)2 and Os3(CO)8(μ-dppf)(μ-H)2 with activated alkynes

Heating a benzene solution of the unsaturated cluster Os3(CO)8(μ-dppm)(μ-H)2 (1) [dppm = bis(diphenylphosphino)methane] with MeO2CCCCO2Me (DMAD) or EtO2CCCCO2Et (DEAD) at 80 °C furnished the dinuclear compounds Os2(CO)4(μ-dppm)(μ-η2;η1;к1-RO2CCCHCO2R)(μ-H) (3a, R = Me, 3b, R = Et) and the saturated trinuclear complexes Os3(CO)7(μ-dppm)(μ3-η2;η1;η1-RO2CCCCO2R)(μ-H)2 (4a, R = Me, 4b, R = Et). In contrast, similar reactions using unsaturated Os3(CO)8(μ-dppf)(μ-H)2 (2) [dppf = bis(diphenylphosphino)ferrocene] afforded only the trinuclear complexes Os3(CO)8(μ-dppf)(μ-η2;η1-RO2CCHCCO2R)(μ-H) (5a, R = Me; 5b, R = Et) and Os3(CO)7(μ-dppf)(μ3-η2;η1;η1-RO2CCCCO2R)(μ-H)2 (6a, R = Me; 6b, R = Et). Control experiments confirm that 5a and 5b decarbonylate at 80 °C to give 6a and 6b, respectively. Both 5a and 5b exist as a pair of isomers in solution, as demonstrated by 1H NMR and 31P{1H} NMR spectroscopy. DFT calculations on cluster 5a (as the dppf-Me4 derivative) indicate that the isomeric mixture derives from a torsional motion that promotes the conformational flipping of the cyclopentadienyl groups of the dppf-Me4 ligand relative to the metallic plane. VT NMR measurements on clusters 6a and 6b indicate that while the hydride ligand associated with the dppf-bridged Os-Os bond is nonfluxional at room temperature, the second hydride rapidly oscillates between the two non-dppf-bridged Os-Os edges. DFT examination of this hydride fluxionality confirms a “windshield wiper” motion for the labile hydride that gives rise to a time-average coupling of this hydride to both phosphorus centers of the dppf ligand. Thermolysis of 6a and 6b in refluxing toluene yielded Os3(CO)7(μ-dppf)(μ-η2;η1;к1-CCHCO2R) (7a, R=Me; 7b, R=Et). The vinylidene moieties in 7a and 7b derive from the carbon-carbon bond cleavage of coordinated alkyne ligands, and these two products exhibit high thermal stability in refluxing toluene.

Preparation, structure and electrochemistry of heterometallic Ru(II) and Fe(II) complexes

Four ruthenium(II) complexes containing ferrocene-based ligands, Ru(acac)2(dppf) (1), Ru(acac)2(η2-O2CFc) (2), Ru(PPh3)2(η2-O2CFc)2 (3) and Ru(dppf)(η2-O2CFc)2 (4) have been prepared by the reaction of Ru(acac)2(CH3CN)2 with 1,1-bis(diphenylphosphino)ferrocene or Ru(PPh3)3Cl2 with ferrocenecarboxylic acid in the presence of sodium bicarbonate. In these complexes, the Ru center is chelated by the dppf ligand or bound with the ferrocenecarboxylate moiety in a η2 fashion. All the complexes were characterized by microanalyses, 1H and 31P{1H} NMR, ESI-MS, IR, and UV–Vis spectroscopy. The solid state structure of complex 1 was confirmed by X-ray crystallography. Cyclic voltammetry measurements in dichloromethane for all complexes display reversible or quasi-reversible Ru and Fe couples with significant coupling. Two one-electron oxidation waves were observed in the cyclic voltammetry of 3 and 4 due to the stepwise oxidation of [Fe2II,II] into [Fe2II,III]+ and [Fe2II,III]+ into [Fe2III,III]2+.

Cyclometalated platinum(ii) complexes of 2,2'-bipyridine N-oxide containing a 1,1'-bis(diphenylphosphino)ferrocene ligand: structural, computational and electrochemical studies.

The preparation and characterization of new heteronuclear-platinum(ii) complexes containing a 1,1'-bis(diphenylphosphino)ferrocene (dppf) ligand are described. The reaction of the known starting complex [PtMe(κ2N,C-bipyO-H)(SMe2)], A, in which bipyO-H is a cyclometalated rollover 2,2'-bipyridine N-oxide, with the dppf ligand in a 2 : 1 ratio or an equimolar ratio led to the formation of the corresponding binuclear complex [Pt2Me2(κ2N,C-bipyO-H)2(μ-dppf)], 1, or the mononuclear complex [PtMe(κ1C-bipyO-H)(dppf)], 2, respectively. According to the reaction conditions, the dppf ligand in 1 and 2 behaves as either a bridging or chelating ligand. All complexes were characterized by NMR spectroscopy. The solid-state structure of 2 was determined by the single-crystal X-ray diffraction method and it was shown that the chelating dppf ligand in this complex was arranged in a "synclinal-staggered" conformation. Also, the occurrence of intermolecular C-HCpObipyO-H interactions in the solid-state gave rise to an extended 1-D network. The electronic absorption spectra and the electrochemical behavior of these complexes are discussed. Density functional theory (DFT) was used for geometry optimization of the singlet states in solution and for electronic structure calculations. The analysis of the molecular orbital (MO) compositions in terms of occupied and unoccupied fragment orbitals in 2 was performed.

Synthesis, electronic structure and molecular docking of new organometallic palladium (II) complexes with intercalator ligands: The influence of bridged ligands on enhanced DNA/serum protein binding and in vitro antitumoral activity

Novel organometallic palladium(II) complexes [Pd2{(C,N)C12H8NH2)}2(μ-dppf)Cl2] (2) [Pd2{(C,N)C12H8NH2)}2(μ-dpp)Cl2] (3) [1,1-bis(diphenylphosphine)-ferrocene (dppf), 1,3-Bis(4-pyridyl)propane (bpp)] have been synthesized, fully characterized by elemental analysis, multi-nuclear (1H,31P{1H},13C{1H}) NMR and IR spectroscopic techniques and their biological activities such as anti-tumoral activity and DNA-protein interactions have been investigated. The crystal structure of (2), established by X-ray diffraction, shows that the dppf ligand is bound to the two palladium atoms in bridged form. The interaction of the complexes with calf thymus DNA (CT-DNA) has been explored by UV–Vis spectroscopy, emission titration and thermal denaturation (Tm) methods, which have revealed that these complexes interact with DNA through intercalation mode. Competitive studies with methylene blue (MB) have shown the ability of the complexes to displace the DNAbound MB, suggesting a competition with MB. Furthermore, the microenvironment and the secondary structure of BSA are changed in the presence of the complexes. Competitive binding using Warfarin, Digoxin and site markers, which have definite binding sites, demonstrated that the complexes bind to site I on BSA. Notably, the complexes exhibit significant in vitro selective cytotoxicity against two human cancer cell lines (JURKAT and SKOV3) with IC50 values varying from 2.3 to 6.7 μM. This indicates that they are more active than cisplatin and showing low cytotoxic activity on normal cells. Finally, molecular modelling studies have been conducted to determine the binding site of the DNA and BSA with the complexes.

Ferrocene-Functionalized Cu(I)/Ag(I) Dithiocarbamate Clusters.

A series of compounds, namely, [Cu8(μ4-H){S2CNMeCH2Fc}6](PF6) (1), [Cu7(μ4-H) {S2CN(i)PrCH2Fc}6] (2), [Cu3{S2CN(Bz) (CH2Fc)}2(dppf)2](PF6) (3), and [Ag2{S2CNMe(CH2Fc)}2(PPh3)2] (4) (dppf = 1,1'-bis(diphenylphosphino)ferrocene), supported by multiferrocene assemblies, were synthesized. All the compounds were characterized by (1)H NMR, Fourier transform infrared, elemental analysis, and electrospray ionization mass spectrometry techniques. Single-crystal X-ray structural analysis revealed that 1 is a monocationic octanuclear Cu(I) cluster and that 2 is a neutral heptanuclear Cu(I) cluster with tetracapped tetrahedral (1) and tricapped tetrahedral (2) geometries entrapped with an interstitial hydride, anchored by six ferrocene units at the periphery of the core. Compounds 3 and 4 comprise trimetallic Cu(I) and dimetallic Ag(I) cores enfolded by four and two ferrocene moieties. Interestingly both chelating and bridging modes of binding are observed for dppf ligand in 3. Further the formation and isolation of polyhydrido copper clusters [Cu28H15{S2CN(i)PrCH2Fc}12](PF6) (5) and [Cu28H15{S2CN(n)Bu2}12](PF6) (7), stabilized by bulky ferrocenyl and n-butyl dithiocarbamate ligands, was demonstrated. They are readily identified by (2)H NMR studies on their deuterium analogues, [Cu28D15{S2CN(i)PrCH2Fc}12](PF6) (6) and [Cu28D15{S2CN(n)Bu2}12](PF6) (8). Though the structure details as well as spectroscopic characterizations of 5 are yet to be investigated, the compound 7 is fully characterized by variety of spectroscopy including single-crystal X-ray diffraction. The cyclic voltammetry studies for compounds 1, 2, and 4 display irreversible redox peaks for Fe(2+)/Fe(3+) couple wherein the reduction peaks are not well-resolved due to some adsorption of the complex onto the electrode surface.

Pd(II) Trifluoroacetate Complexes Containing Chelating Phosphine Ligands: Synthesis, Structures, and Catalysis

Carboxylates coordinate to transitionmetals in a terminal, chelating, or bridging mode through their oxygen atoms, and serve as active ligands in various catalytic reactions. Transition-metal complexes having a trifluoroacetate (TFA) ligand are well known to have higher solubility and crystallinity than the corresponding acetate counterparts depending on the metal identity. In particular, TFA complexes of late transitionmetals are efficient catalysts in several organic reactions, including polymerization of isocyanide or butadiene and copolymerization of CO and olefin. Moreover, such complexes exhibit higher efficiency than the corresponding acetate complexes in the aerobic oxidation of organic substrates, enamide formation by vinyl transfer, or oxidative cyclization of organic substrates in the presence of Pd catalysts. Although many catalytic Suzuki–Miyaura C C coupling reactions have been reported, those involving late-transition-metal–TFA complexes are still rare. For this reason, we attempted to develop a new synthetic route to Pd–TFA complexes possessing chelating phosphine ligands for use in such coupling reactions. In this work, we prepared a series of Pd(II)–TFA–(chelating diphosphine) complexes and examined their catalytic C C coupling reactions of aryl halides and arylboronic acids. We first prepared a Pd(II)–TFA–TMEDA complex (TMEDA = N,N,N0,N0-dimethyl ethylene diamine), [Pd (TMEDA)(TFA)2] (1), by themetathesis of [PdCl2(TMEDA)] and 2 equiv of [Ag(TFA)]. Subsequently, the ligand replacement of complex 1 was investigated with one or two equivalents of chelating phosphine, including DMPE, DEPE, 1,2Ph2P(CH2)nPPh2 (n = 2, DPPE; n = 3, DPPP; n = 4, DPPB), and the ferrocene-bridged phosphines DPPF and DIPPF (1,10-bis(diphenyl or diisoporpyl)phosphine ferrocene). These reactions afforded ionic bis(diphosphine) Pd(II) complexes [Pd(P~P)2](TFA)2 (type A, 2–6) or neutral mono(diphosphine) Pd(II)–TFA complexes [Pd(P~P) (TFA)2] (type B, 7 and 8) in high yields (Scheme 1). Chemical compositions of complexes2–8 strongly indicate that sterically hindered and less basic chelating phosphines such as DPPF or DIPPF prefer to form mono(diphosphine) compounds. Isolated bis(chelating phosphine)–Pd(II)–TFA complexes are poorly soluble in organic solvents. All products were characterized by spectroscopy (IR and NMR) and elemental analysis, together with X-ray crystallography for complexes 2 and 7. The IR spectra display characteristic stretching C O and C F bands at 1671–1711 and at 1105–1190 cm, respectively. Details on crystal data of complexes are summarized in Supporting Information (see Table S1). Figure 1 shows the cationic part of complex 2 H2O, in which two CF3COO counterions and one lattice water are omitted for clarity. The molecular structure of 7 is given in Figure 2, which shows a Pd(II) metal, a DPPF ligand, and two CF3COO ligands. TwoCp rings in theDPPF ligand are not perfectly parallel,with a dihedral angle of 4.4(4) . ThePd Fe separation of 4.1932(8)A indicates no direct interactions between these two metals. We examined the ligand exchange reaction of complex 8 with 2 equiv of NaN3 in CH2Cl2 (Scheme 2). The reaction readily proceeded to give a Pd(II) azide complex, [(DIPPF) Pd(N3)2] (9), as an orange crystal in quantitative yield, which was characterized by spectroscopic data and elemental analysis. The IR spectrum of 9 shows a strong absorption band at 2045 cm, a characteristic peak of the N3 group. Recently, several Suzuki–Miyaura C C coupling reactions employing Pd(II)–TFA complexes containing C–N donor or pincer-type (PCP) ligands were reported. However, the corresponding reactions with bis(chelating phosphine) analogs are relatively rare. In this context, we evaluated the catalytic activity of several complexes (1, 2, 6–8, and 9) for the coupling reactions (catalysts in Chart 1 and Scheme 3). In order to find the optimum conditions for Scheme 1. Syntheses of Pd(II) trifluoroacetates. Note DOI: 10.1002/bkcs.10590 K.-W. Kim et al. BULLETIN OF THE KOREAN CHEMICAL SOCIETY

Comparison of dppf‐Supported Nickel Precatalysts for the Suzuki–Miyaura Reaction: The Observation and Activity of Nickel(I)

AbstractNi‐based precatalysts for the Suzuki–Miyaura reaction have potential chemical and economic advantages compared to commonly used Pd systems. Here, we compare Ni precatalysts for the Suzuki–Miyaura reaction supported by the dppf ligand in 3 oxidation states, 0, I and II. Surprisingly, at 80 °C they give similar catalytic activity, with all systems generating significant amounts of NiI during the reaction. At room temperature a readily accessible bench‐stable NiII precatalyst is highly active and can couple synthetically important heterocyclic substrates. Our work conclusively establishes that NiI species are relevant in reactions typically proposed to involve exclusively Ni0 and NiII complexes.

Comparison of dppf-Supported Nickel Precatalysts for the Suzuki-Miyaura Reaction: The Observation and Activity of Nickel(I).

Ni-based precatalysts for the Suzuki-Miyaura reaction have potential chemical and economic advantages compared to commonly used Pd systems. Here, we compare Ni precatalysts for the Suzuki-Miyaura reaction supported by the dppf ligand in 3 oxidation states, 0, I and II. Surprisingly, at 80 °C they give similar catalytic activity, with all systems generating significant amounts of Ni(I) during the reaction. At room temperature a readily accessible bench-stable Ni(II) precatalyst is highly active and can couple synthetically important heterocyclic substrates. Our work conclusively establishes that Ni(I) species are relevant in reactions typically proposed to involve exclusively Ni(0) and Ni(II) complexes.

Synthesis and characterization of 1,1′-ferrocenyldichalcogenolato complexes of palladium and platinum

A rare class of heterobimetallic complexes [M{Fe(η5-EC5H4)2}(L)] [M=Pt, Pd; E=Se, Te; L=dppe=1,2-bis(diphenylphosphino)ethane, dppf=1,2-bis(diphenylphosphino)ferrocene] (1–7) containing the 1,1′-ferrocenylditellurolato and -selenolato ligands were synthesized by the reaction of [MCl2(L)] with Li2[Fe(η5-EC5H4)2] in thf. All complexes were characterized by 31P, 77Se, 125Te, and 195Pt NMR spectroscopy, as appropriate. The crystal structures of [Pt{Fe(η5-TeC5H4)2}(dppe)]·C7H8 (2·C7H8), [Pd{Fe(η5-SeC5H4)2}(dppe)]·C7H8 (3·C7H8), [Pd{Fe(η5-SeC5H4)2}(dppe)]·C7H8 (4·C7H8), and [Pt{Fe(η5-SeC5H4)2}(dppf)] (5) were determined by single crystal X-ray crystallography. All complexes exhibited the same or related structural motif. The simulation of the NMR spectra of 1, 6, and 7, for which no crystals were obtained, showed that these complexes also have the same molecular structure. The complexes (1–4) containing the chelating dppe ligand were more stable that those (5–7) containing the dppf ligand. In fact, [Pd{Fe(η5-TeC5H4)2}(dppf)] could not be obtained by the reaction of [PdCl2(dppf)] with Li2[Fe(η5-TeC5H4)2]. A small crop of crystals of [Fe(η5-C5H4Se)2CH2] (8) were observed upon slow decomposition of [Pd{Fe(η5-SeC5H4)2}(dppe)] and [Pt{Fe(η5-SeC5H4)2}(dppf)] in CH2Cl2.

Facile synthesis of acridines via Pd(0)-diphosphine complex-catalyzed tandem coupling/cyclization protocol.

A facile and efficient approach for the synthesis of a variety of acridines via the tandem coupling/cyclization of substituted 2-bromobenzaldehydes and anilines is described. The reaction can be accomplished with ease in the presence of a catalytic amount of Pd2(dba)3 and diphosphine ligand dppf, providing a broad range of substituted acridines in good to excellent yields (up to 99%). The Lewis acid, AlCl3, is required to promote the cyclization for less electron-rich anilines.

Sp3–sp2 vs sp3–sp3 C–C Site Selectivity in Rh-Catalyzed Ring Opening of Benzocyclobutenol: A DFT Study

The C(sp(3))-C(sp(2)) vs C(sp(3))-C(sp(3)) site selectivity in the C-C bond activation in Rh-catalyzed ring opening of benzocyclobutenol was systematically investigated using density functional theory (DFT). The catalytic cycle includes three elementary steps: the proton transfer from the substrate to a rhodium hydroxide, the C-C cleavage, and the proton transfer from water onto a carbon forming the final product with regeneration of the rhodium hydroxide. The site selectivity is determined by the C-C cleavage step; the C(sp(3))-C(sp(2)) cleavage is favored over the C(sp(3))-C(sp(3)) cleavage because the former transition state is stabilized by an interaction between the benzene ring of the substrate and Rh. DMSO, a more polar solvent, reduces the site selectivity as the more polar C(sp(3))-C(sp(3)) transition state (TS) is stabilized more than the C(sp(3))-C(sp(2)) TS and decreases the advantage of the latter TS. DPPF ligand is bulky, and the steric repulsion on the tighter C(sp(3))-C(sp(2)) TS causes the loss of the site selectivity. For the even more crowded Rh(P(t-Bu)3)2 catalyst, one phosphine has to dissociate before the C-C cleavage reaction takes place, and the advantage of the C(sp(3))-C(sp(2)) TS is regained for the less crowded RhP(t-Bu)3 active catalyst.

Mononuclear Coordination Complexes of Fullerene C60 with Zerovalent Cobalt Having S = 1/2 Spin State: Co(η2-C60)(L)(C6H5CN)·(o-C6H4Cl2) (L = 1,2-bis(diphenylphosphino)ethane and 1,1′-bis(diphenylphosphino)ferrocene)

Two mononuclear coordination complexes of fullerene C60 with cobalt, Co(η(2)-C60)(dppe)(C6H5CN)·C6H4Cl2 (1) and Co(η(2)-C60)(dppf)(C6H5CN)·C6H4Cl2 (2) (dppe is 1,2-bis(diphenylphosphino)ethane and dppf is 1,1'-bis(diphenylphosphino)ferrocene) have been obtained by sodium fluorenone reduction of the Co(dppe)Cl2 or Co(dppf)Br2 and C60 mixtures. The IR and visible-NIR spectra of 1 and 2 indicate the neutral state of fullerenes. Therefore, cobalt atoms formally have the zerovalent state. Cobalt coordinates to the 6-6 bond of C60 by η(2)-type coordination with Co-C bond lengths in the 2.008(3)-2.060(3) Å range. Diphosphine and benzonitrile ligands additionally coordinate to cobalt to form a distorted square-pyramidal environment for the cobalt atoms. Complexes 1 and 2 are rare examples of fullerene coordination complexes with paramagnetic metal centers. Both complexes manifest intense asymmetric EPR signals attributed to zerovalent cobalt atoms, which can be fitted by three components with g = 2.261-2.124 (1) and g = 2.258-2.092 (2). Effective magnetic moments of 1 and 2 indicate the low-spin (S = 1/2) state of Co(0). In accordance with EPR spectra, DFT calculations show that the spin density is localized mainly on the central cobalt atoms and only slightly delocalized into C60, benzonitrile, dppe, or dppf ligands.

Bimetallic osmium-tin complexes: Stannylene and hydrostannylene clusters upon addition of Ph3SnH to unsaturated triosmium clusters [(μ-H)2Os3(CO)8(μ-diphosphine)] (diphosphine = dppm, dppf)

Products of the addition of Ph3SnH to the unsaturated triosmium clusters [(μ-H)2Os3(CO)8(μ-dppm)] (1) and [(μ-H)2Os3(CO)8(μ-dppf)] (2) are highly dependent on the nature of the diphosphine. With the rigid bis(diphenylphosphino)methane (dppm), the stannylene complex [H2Os3(CO)7(μ-SnPh2)2(μ-dppm)] (3) is the major cluster product (35% yield), resulting from both Sn–H and Sn–C bond activation, while two previously reported triphenyltin complexes, [(μ-H)2Os3(CO)8(SnPh3)2(μ-dppm)] (4) (10% yield) and [(μ-H)2Os3(CO)8(SnPh3){μ-Ph2PCH2P(Ph)C6H4}] (5) (11% yield) also result. Biphenyl is also a co-product of this reaction and it is postulated to be formed concomitantly with 3. A similar reaction with the highly flexible 1,1′-bis(diphenylphosphino)ferrocene (dppf) complex leads to the formation of four tin-containing complexes: two previously reported compounds [HOs(CO)4(SnPh3)] (6) (8% yield) and [Os2(CO)6(SnPh3)2(μ-SnPh2)2] (8) (5% yield), and the new triphenyltin and hydrostannylene clusters [H(μ-H)2Os3(CO)8(SnPh3)(μ-dppf)] (10) (22% yield) and [(μ-H)Os2(CO)4(SnPh3)2(μ-HSnPh2)(μ-dppf)] (9) (12% yield) respectively, together with the dihydroxy cluster [Os3(CO)8(μ-OH)2(μ-dppf)] (7). Two of these new clusters have been characterized by X-ray crystallography. Cluster 3 consists of a central Os3 triangle with two stannylene groups, each bridging one Os–Os edge, a dppm ligand that bridges the third Os-Os edge, and two terminal hydride ligands. Cluster 10 consists of an Os3 triangle with a terminal SnPh3 group, one terminal and two bridging hydride ligands, and a bridging dppf ligand. The new compounds 3, 7, 9, and 10 have been investigated by electronic structure calculations, and the computed ground-state structures are discussed relative to the X-ray crystallographic structures.

Diiron Azadithiolate Complexes with Bridging Phosphine Ligand dppf: Synthesis and Characterization

Reaction of complex [(μ-SCH2)2NCH2CO2Me]Fe2(CO)6 (A) with 1,1′-bis(diphenylphosphino)ferrocene (dppf) in the presence of the decarbonylating agent Me3NO∙2H2O gave complex [(μ-SCH2)2NCH2CO2MeFe2(CO)5]2[(η 5-Ph2PC5H4)2Fe] (1) in 72 % yields, whereas complex [(μ-SCH2)2NPhFe2(CO)5]2[(η 5-Ph2PC5H4)2Fe] (2) was produced by reaction of [(μ-SCH2)2NPh]Fe2(CO)6 (B) with dppf in toluene at reflux in 41 % yield. The new complexes 1 and 2 were characterized by elemental analysis, IR, and 1H (31P, 13C) NMR spectroscopy as well as by single crystal X-ray diffraction analysis. In the crystal structures of 1 and 2, the dppf ligand resides in an apical position of the square-pyramidal geometry of the neighbouring Fe atoms and the crystal structures were stabilized by the intermolecular C–H···O hydrogen bonds.

Copper Chalcogenide Clusters Stabilized with Ferrocene-Based Diphosphine Ligands

The redox-active diphosphine ligand 1,1'-bis(diphenylphosphino)ferrocene (dppf) has been used to stabilize the copper(I) chalcogenide clusters [Cu12(μ4-S)6(μ-dppf)4] (1), [Cu8(μ4-Se)4(μ-dppf)3] (2), [Cu4(μ4-Te)(μ4-η(2)-Te2)(μ-dppf)2] (3), and [Cu12(μ5-Te)4(μ8-η(2)-Te2)2(μ-dppf)4] (4), prepared by the reaction of the copper(I) acetate coordination complex (dppf)CuOAc (5) with 0.5 equiv of E(SiMe3)2 (E = S, Se, Te). Single-crystal X-ray analyses of complexes 1-4 confirm the presence of {Cu(2x)E(x)} cores stabilized by dppf ligands on their surfaces, where the bidentate ligands adopt bridging coordination modes. The redox chemistry of cluster 1 was examined using cyclic voltammetry and compared to the electrochemistry of the free ligand dppf and the corresponding copper(I) acetate coordination complex 5. Cluster 1 shows the expected consecutive oxidations of the ferrocene moieties, Cu(I) centers, and phosphine of the dppf ligand.