Phosphine Moiety Research Articles

Dual reactivity pattern of Mn(I) carbyne complexes Cp(CO)2Mn+≡C–R (R = Ar, Alk) vs. dppm: Subtle balance between double intramolecular nucleophilic addition and nucleophilic addition followed by migratory CO insertion

The Mn(I) cationic carbyne complexes [Cp(CO)2Mn+≡C–R]BX4 (R = Ph, Tol, Me, Bn; X = F, Cl, Ph) react with bis(diphenylphosphino)methane to afford selectively either cyclic λ5-1,3-diphosphetium semi-ylides [RC–P+Ph2CH2P+Ph2)]BPh4 ([R4]BPh4; R = Ph, Tol), or Mn(I) complexes [Cp(CO)Mn(η3-(P,C,C)-Ph2PCH2P+Ph2C(R)=C=O)]BX4 ([R5]BX4; R = Me, X = Ph; R = Bn, X = F) featuring unprecedented phosphonioketene ligands depending on the nature of the carbyne substituent, aryl or alkyl, respectively. The selective formation of these products is tentatively rationalized through the key formation of a transient cationic Mn(I) phosphoniocarbene complexes [Cp(CO)2Mn=C(R)PPh2+CH2PPh2]BX4 bearing a pendent phosphine moiety. The molecular structures of semi-ylide [Ph4]BPh4 and complex [Bn5]BF4 were elucidated by single-crystal X-ray diffraction.

Unprecedented One-Pot Reaction towards Chiral, Non-Racemic Copper(I) Complexes of [2.2]Paracyclophane-Based P,N-Ligands.

Herein, we report a simple one-pot route to enantiopure copper(I) complexes featuring a unique [2.2]paracyclophane-based P,N-ligand system. Phosphine and pyridine moieties can be varied allowing the modular synthesis of these rigid and stable [2.2]paracyclophane-based P,N-ligands. These P,N-ligands are a new ligand class for different transition-metal complexes, which is shown exemplarily for palladium(II).

Ambidentate Ligand Reactivity with the Rhenium(I) Compounds [BrRe(CO)4]2 and cis‐BrRe(CO)4L: A Kinetic and Mechanistic Study

The reaction of the halo‐bridged dimer [BrRe(CO)4]2 with the ambidentate donor 2‐(diphenylphosphanyl)pyridine (PN) has been investigated. The substitution reaction is rapid at room temperature and regioselective for phosphorus coordination to yield exclusively cis‐BrRe(CO)4(κP‐PN) (1). Thermolysis of 1 furnishes the PN‐chelated product fac‐BrRe(CO)3(κP,N‐PN) (2) and CO. The kinetics for the conversion of 1 → 2 + CO have been measured by UV/Vis spectroscopy in toluene over the temperature range of 323–343 K. On the basis of the activation parameters [ΔH‡ = 28.0(0.9) kcal/mol and ΔS‡ = 31(3) eu], a dissociative process is supported, and this was corroborated by electronic structure calculations. The regioselectivity in the ligand‐substitution reaction involving [BrRe(CO)4]2 and the tridentate donor 6‐(diphenylphosphanyl)‐2‐formylpyridine (PON) was also studied, and consistent with the PN donor, only the κP‐product, cis‐BrRe(CO)4(κP‐PON) (3) is formed. The reaction of the dimer [BrRe(CO)4]2 with 2‐(diphenylphosphanyl)pyridine (PN) has been computationally modeled by DFT calculations. The energetics for the creation of an unsaturated intermediate through the cleavage of one of the bridging bromide ligands, followed by the addition of the donor to the unsaturated rhenium center versus the direct attack of the pnictogen donor on the dimer have been evaluated. The latter process is computed as the preferred route for dimer activation, with an attack of the pyridyl moiety slightly favored compared to the phosphine moiety. The computed pnictogen preference agrees with the kinetic data published by Zingales and coworkers. Concerning the reaction of the PN ligand with [BrRe(CO)4]2, we predict the initial formation of the κN‐isomer of 1 as the kinetic product of substitution, which in turn undergoes a rapid isomerization to furnish the thermodynamically more stable κP‐isomer through a reversible ligand dissociation process. The intramolecular linkage isomerization of κN‐1 to κP‐1 in 1 was also investigated by DFT, and the concerted process was found to lie 6.5 kcal/mol above the two‐step process involving ligand dissociation.

Tuning the Diiron Core Geometry in Carboxylate-Bridged Macrocyclic Model Complexes Affects Their Redox Properties and Supports Oxidation Chemistry.

We introduce a novel platform to mimic the coordination environment of carboxylate-bridged diiron proteins by tethering a small, dangling internal carboxylate, (CH2)nCOOH, to phenol-imine macrocyclic ligands (H3PIMICn). In the presence of an external bulky carboxylic acid (RCO2H), the ligands react with [Fe2(Mes)4] (Mes = 2,4,6-trimethylphenyl) to afford dinuclear [Fe2(PIMICn)(RCO2)(MeCN)] (n = 4-6) complexes. X-ray diffraction studies revealed structural similarities between these complexes and the reduced diiron active sites of proteins such as Class I ribonucleotide reductase (RNR) R2 and soluble methane monooxygenase hydroxylase. The number of CH2 units of the internal carboxylate arm controls the diiron core geometry, affecting in turn the anodic peak potential of the complexes. As functional synthetic models, these complexes facilitate the oxidation of C-H bonds in the presence of peroxides and oxo transfer from O2 to an internal phosphine moiety.

Derivatization of Phosphine Ligands with Bulky Deltahedral Zintl Clusters-Synthesis of Charge Neutral Zwitterionic Tetrel Cluster Compounds [(Ge9{Si(TMS)3}2)tBu2P]M(NHCDipp) (M: Cu, Ag, Au).

Reactions of silylated clusters [Ge9{Si(TMS)3}3]- or [Ge9{Si(TMS)3}2]2- with dialkylhalophosphines R2PCl (Cy, iPr, tBu) at ambient temperature yield the first tetrel Zintl cluster compounds bearing phosphine moieties. Varying reactivity of the dialkylhalophosphines toward the silylated clusters is observed depending on the bulkiness of the phosphine's alkyl substituents and on the number of hypersilyl groups at the tetrel cluster. Reactions between phosphines with small cyclohexyl- (Cy) or isopropyl- (iPr) groups and the tris-silylated cluster [Ge9{Si(TMS)3}3]- yield the novel neutral cluster compounds [Ge9{Si(TMS)3}3PR2] (R: Cy (1), iPr (2)) with discrete Ge-P exo bonds. By contrast, the bulkier phosphine tBu2PCl does not react with [Ge9{Si(TMS)3}3]- due to steric crowding. However, the reaction with the bis-silylated cluster [Ge9{Si(TMS)3}2]2- yields the novel cluster compound [Ge9{Si(TMS)3}2PtBu2]- (3). Subsequent reactions of compound 3 with NHCDippMCl (M: Cu, Ag, Au) yield the charge neutral zwitterionic compounds [(Ge9{Si(TMS)3}2)tBu2P]M(NHCDipp) (M: Cu, Ag, Au) (4-6), in which compound 3 acts as a phosphine ligand bearing a bulky tetrel Zintl cluster moiety. Compounds 4-6 also represent the first uncharged examples for 3-fold substituted tetrel Zintl clusters.

Polymerization of Ethylene Catalyzed by Phosphine-Iminophosphorane Palladium Complexes

Phosphine-iminophosphorane palladium complexes were synthesized and studied as catalysts for ethylene polymerization. The effect of the substituents on the phosphine and iminophosphorane moieties was investigated. Catalyst 15 promoted the conversion of ethylene to moderate molecular weight linear polyethylene (Mn ≈ 14000 g/mol, branches/1000C ≈ 7). This catalyst proved to be stable at temperatures up to 100 °C with a turnover frequency of 2100 h–1.

Alternatives to Phosphinooxazoline (t‐BuPHOX) Ligands in the Metal‐Catalyzed Hydrogenation of Minimally Functionalized Olefins and Cyclic β‐Enamides

AbstractThis study presents a new series of readily accessible iridium‐ and rhodium‐phosphite/oxazoline catalytic systems that can efficiently hydrogenate, for the first time, both minimally functionalized olefins and functionalized olefins (62 examples in total) in high enantioselectivities (ees up to >99%) and conversions. The phosphite‐oxazoline ligands, which are readily available in only two synthetic steps, are derived from previous privileged 4‐alkyl‐2‐[2‐(diphenylphosphino)phenyl]‐2‐oxazoline (PHOX) ligands by replacing the phosphine moiety by a biaryl phosphite group and/or the introduction of a methylene spacer between the oxazoline and the phenyl ring. The modular design of the ligands has given us the opportunity not only to overcome the limitations of the iridium‐PHOX catalytic systems in the hydrogenation of minimally functionalized Z‐olefins and 1,1‐disubstituted olefins, but also to expand their use to unfunctionalized olefins containing other challenging scaffolds (e.g., exocyclic benzofused and triaryl‐substituted olefins) and also to olefins with poorly coordinative groups (e.g., α,β‐unsaturated lactams, lactones, alkenylboronic esters, etc.) with enantioselectivities typically >95% ee. Moreover, both enantiomers of the hydrogenation product could be obtained by simply changing the configuration of the biaryl phosphite moiety. Remarkably, the new catalytic systems also provided excellent enantioselectivities (up to 99% ee) in the asymmetric hydrogenation of another challenging class of olefins – the functionalized cyclic β‐enamides. Again, both enantiomers of the reduced amides could be obtained by changing the metal from Ir to Rh. We also demonstrated that environmentally friendly propylene carbonate can be used with no loss of enantioselectivity. Another advantage of the new ligands over the PHOX ligands is that the best ligands are derived from the affordable (S)‐phenylglycinol rather than from the expensive (S)‐tert‐leucinol.magnified image

Synthesis and Coordination Chemistry of a Chelating P–Sn Ligand Based on Stanna‐closo‐dodecaborate

Substitution at a B–H unit of the heteroborate cluster stanna‐closo‐dodecaborate [SnB11H11]2– at the upper belt of the icosahedron by one of the triarylphosphine moieties of xantphos was carried out under the catalysis of palladium acetate. The resulting coupling product is a monoanion offering two coordination sites: a low‐valent tin‐cluster vertex and a triaryl phosphine moiety. The basicity and nucleophilicity of the anion were investigated in reactions with a strong acid or an alkylating agent. Transition‐metal electrophiles like platinum halide PtCl2 or rhodium carbonyl [Rh(CO)2Cl]2 react with the bidentate ligand, with the formation of cis‐coordination products.

Synthesis, Structural Characterization and Catalytic Evaluation of Anionic Phosphinoferrocene Amidosulfonate Ligands

Triethylammonium salts of phosphinoferrocene amidosulfonates with electron-rich dialkyphosphino substituents, R2PfcCONHCH2SO3(HNEt3) (4a–c), where fc = ferrocene-1,1′-diyl, and R = i-Pr (a), cyclohexyl (Cy; b), and t-butyl (c), were synthesized from the corresponding phosphinocarboxylic acids-borane adducts, R2PfcCO2H·BH3 (1a–c), via esters R2PfcCO2C6F5·BH3 (2a–c) and adducts R2PfcCONHCH2SO3(HNEt3)·BH3 (3a–c). Compound 4b was shown to react with [Pd(μ-Cl)(η-C3H5)]2 and AgClO4 to afford the zwitterionic complex [Pd(η3-C3H5)(Cy2PfcCONHCH2SO3-κ2O,P)] (5b), in which the amidosulfonate ligand coordinates as a chelating donor making use of its phosphine moiety and amide oxygen. The structures of 3b·CH2Cl2, 4b and 5b·CH2Cl2 were determined by single-crystal X-ray diffraction analysis. Compounds 4a–c and their known diphenylphosphino analogue, Ph2PfcCONHCH2SO3(HNEt3) (4d), were studied as supporting ligands in Pd-catalyzed cyanation of aryl bromides with K4[Fe(CN)6] and in Suzuki–Miyaura biaryl cross-coupling performed in aqueous reaction media under mild reaction conditions. In the former reaction, the best results were achieved with a catalyst generated from [PdCl2(cod)] (cod = η2:η2-cycloocta-1,5-diene) and 2 equiv. of the least electron-rich ligand 4d in dioxane–water as a solvent. In contrast, the biaryl coupling was advantageously performed with a catalyst resulting from palladium(II) acetate and ligand 4a (1 equiv.) in the same solvent.

Influence of Ligand Backbone Structure and Connectivity on the Properties of Phosphine-Sulfonate Pd(II)/Ni(II) Catalysts.

Phosphine-sulfonate based palladium and nickel catalysts have been extensively studied in ethylene polymerization and copolymerization reactions. Previously, the majority of the research works focused on the modifications of the substituents on the phosphorous atom. In this contribution, we systematically demonstrated that the change of the ligand backbone from benzene to naphthalene could greatly improve the properties of this class of catalysts. In the palladium system, this change could increase catalyst stability and polyethylene molecular weights. In the nickel system, this change could dramatically increase the polyethylene molecular weights. Most interestingly, the change in the connectivity of phosphine and sulfonate moieties to the naphthalene backbone could also significantly influence the catalyst properties.

Ratiometric Visualization of NO/H2S Cross-Talk in Living Cells and Tissues Using a Nitroxyl-Responsive Two-Photon Fluorescence Probe.

It is of scientific significance to explore the intricate relationship between two crucial gasotransmitters nitric oxide (NO) and hydrogen sulfide (H2S) because they exert similar and interdependent biological actions within the living organisms. Nevertheless, visualization of the NO/H2S crosstalk using effective molecular imaging tools remains challenging. To address this issue, and given that nitroxyl (HNO) has been implicated as the interdependent production of NO and H2S via a network of cascading chemical reactions, we herein design a ratiometric two-photon fluorescent probe for HNO, termed TP-Rho-HNO, which consists of benzo[h]chromene-rhodol scaffold as two-photon energy transfer cassette with phosphine moiety as specific HNO recognition unit. The newly proposed probe has been successfully applied in ratiometric two-photon bioimaging of endogenous HNO derived from NO and H2S interaction in the human umbilical vein cells (HUVECs) and as well as in rat brain tissues. Intriguingly, the imaging results consistently demonstrate that the mutually dependent upgeneration of H2S and NO are present in living biosystems, indicating that this molecular probe would provide a powerful approach to elucidate the chemical foundation for the anfractuous cross-talk between the NO and H2S signaling pathways in biology.

A C-Pyrenyl Poly(methylenephosphine): Oxidation “Turns On” Blue Photoluminescence in Solution and the Solid State

A C-pyrenyl poly(methylenephosphine) (Mn = 4800, Đ = 1.56) was synthesized from the anionic polymerization of a P-mesityl phosphaalkene. The phosphine oxide polymer exhibits blue fluorescence in solution (λmax 379, 400 nm, λonset 560 nm; Φ = 0.05) and blue-green fluorescence in the solid state at room temperature (λmax 460 nm, Φ = 0.07). In contrast, unoxidized polymer displays only a weak emission in solution and no emission in the solid state. Fluorescence studies of partially oxidized polymers (50, 75, 83% oxidation) indicate that “turn on” emission occurs only at very high degrees of oxidation (near 100%). We conclude that even a small number of unoxidized phosphine moieties within the partially oxidized polymer intramolecularly quench the fluorescence.

ChemInform Abstract: 4‐Toluenesulfonyloxymethyl‐(H)‐phosphinate: A Reagent for the Introduction of O‐ and S‐Methyl‐(H)‐phosphinate Moieties.

ChemInformVolume 47, Issue 42 Natural Products ChemInform Abstract: 4-Toluenesulfonyloxymethyl-(H)-phosphinate: A Reagent for the Introduction of O- and S-Methyl-(H)-phosphinate Moieties. Ondrej Kostov, Ondrej Kostov Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorOndrej Pav, Ondrej Pav Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorMilos Budesinsky, Milos Budesinsky Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorRadek Liboska, Radek Liboska Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorOndrej Simak, Ondrej Simak Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorMagdalena Petrova, Magdalena Petrova Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorPavel Novak, Pavel Novak Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorIvan Rosenberg, Ivan Rosenberg Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this author Ondrej Kostov, Ondrej Kostov Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorOndrej Pav, Ondrej Pav Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorMilos Budesinsky, Milos Budesinsky Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorRadek Liboska, Radek Liboska Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorOndrej Simak, Ondrej Simak Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorMagdalena Petrova, Magdalena Petrova Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorPavel Novak, Pavel Novak Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this authorIvan Rosenberg, Ivan Rosenberg Inst. Org. Chem. Biochem., Acad. Sci. Czech Rep., CZ-166 10 Prague 6, Czech RepublicSearch for more papers by this author First published: 28 September 2016 https://doi.org/10.1002/chin.201642206Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume47, Issue42September, 2016 RelatedInformation

Core phosphine-functionalized amphiphilic nanogels as catalytic nanoreactors for aqueous biphasic hydroformylation

Amphiphilic phosphine-functionalized nanogel particles were synthesized by aqueous polymerization-induced self-assembly insuring a well-defined architecture as well as a narrow size distribution (average diameter of ca. 90nm in water). They were successfully applied as ligands for the biphasic hydroformylation of 1-octene catalyzed by rhodium, yielding TOFs in the 350–650h−1 range and a linear to branched aldehyde ratio of 3.5. Embedding the phosphine ligands within a cross-linked structure did not strongly impede mass transfer toward the active centers, as proved by fast metal coordination and a catalytic activity tantamount to that of higher chain mobility micelles or core-cross-linked micelles that have phosphine moieties located on flexible linear arms. However, this extended cross-linking reduced particle swelling and transfer to the organic phase, affording a significantly lowered Rh loss. For all the architectures, a low functionalization degree was preferable to achieve high activity, the selectivity remaining essentially unchanged.

Synthesis and Alkali-Metal-Ion Complexation of P-Stereogenic Diphosphacrowns.

Phosphine is conformationally stable because of the high inversion energy barrier of the phosphorus atom, which allows the phosphorus atom to become a chiral center. Thus, enantiopure P‐stereogenic 12‐, 15‐, 18‐, and 21‐membered aliphatic phosphines “diphosphacrowns” were synthesized from secondary P‐stereogenic bisphosphine as a chiral building block. Their complexation behaviors with alkali metal ions are investigated in comparison with benzo‐18‐diphosphacrown‐6 and benzo‐18‐crown‐6. 15‐, 18‐, and 21‐Membered diphosphacrowns captured alkali metal ions to form 1:1 metal complexes. Unique guest selectivity was observed, as diphosphacrowns encapsulated smaller alkali metal ions than common crown ethers; for example, 18‐membered diphosphacrowns interacted more strongly with Na+ than K+. The difference in guest selectivity between diphosphacrowns and common crown ethers is speculated to result from the cavity size, owing to the large phosphorus atom as well as steric hindrance around the phosphine moiety.

4-Toluenesulfonyloxymethyl-(H)-phosphinate: A Reagent for the Introduction of O- and S-Methyl-(H)-phosphinate Moieties.

The straightforward synthesis of sodium 4-toluenesulfonyloxymethyl-(H)-phosphinate and (H)-phosphinomethylisothiouronium tosylate as new reagents for the preparation of O- and S-methyl-(H)-phosphinic acid derivatives, respectively, is described. The reactivity of both reagents was demonstrated by the preparation of protected 2'-deoxyribonucleoside-O-methyl-(H)-phosphinates in the 5'- and 3'-series and 2',5'-dideoxyribonucleoside-5'-S-methyl-(H)-phosphinates. These compounds represent a new class of monomers compatible with the solid phase synthesis of oligonucleotides by H-phosphonate chemistry, as it was proved with the synthesis of a fully phosphonate heptamer.

Adsorption behavior and mechanism of glufosinate onto goethite

The adsorption of glufosinate (GLU), a widely used herbicide similar to glyphosate (GLY), onto goethite was investigated as a function of the pH, ionic strength, background cations and anions, heavy metal ions and fulvic acids (FAs) by using batch adsorption experiments. In situ ATR-FTIR spectroscopy and density functional theory (DFT) calculations were carried out to characterize the molecular interactions between GLU and goethite surfaces. The macroscopic results indicated that an increasing pH exerted an adverse effect on GLU adsorption because of the electrostatic repulsion, and the adsorption was not sensitive to ionic strengths or background cation types, indicating that an inner-sphere surface complex was involved. GLU adsorption can be considerably depressed by PO43−, SO42−, and a high level of FA because of the competitive effect, while being enhanced by Cu2+ with a maximum adsorption at approximately pH5 because of the metal ion bridging effect. Other examined divalent metal cations (Cd2+, Zn2+, and Pb2+) showed almost no effect on GLU adsorption, indicating weak interaction between them. ATR-FTIR spectra and the DFT calculations further proved that GLU was bonded to goethite surfaces through the formation of a monodentate mononuclear inner-sphere complex between the phosphinic moiety and surface Fe(III) centers under an acidic condition. The results showed that GLU had a similar adsorption mechanism to that of GLY onto goethite, but with a lower adsorption affinity, possibly exerting higher mobility and risk in soils.

A new oxorhenium(V) complex with benzothiazole derived ligand: Relative stability and global chemical reactivity indices

A new rhenium complex, cis-[ReO(btmp)PPh3Cl2] (2a) with 2-benzothiazolyl-5-methoxyphenol (Hbtmp) has been synthesized and characterized by means of FT-IR, UV–Vis, 1H NMR and elemental analyses. The structural parameters of 2a as obtained from XRD studies have been compared with the calculated [PBEPBE/STMIDI] values. The observed results are in good agreement. The vibrational frequencies, electronic transitions of 2a have been calculated and compared with the experimental results. The global chemical reactivity descriptors based on conceptual density functional theory have also been calculated for a set of analogous systems derived from 2a varying the central metal center (Re or Tc) and substituted phosphine moieties. A good relationship between the calculated hardness (η) and Tolman’s cone angle (θ) of phosphines is observed both for Re and Tc complexes. Similar harmony between electronic chemical potential (μ) and Tolman’s electronic parameter (ν) of phosphines is also noted.

Microwave-induced dppm ligand substitution in triosmium clusters: Structural and DFT evaluation of Os3 clusters containing multiply activated dppm ligands through cyclometalation, ortho metalation, and P[sbnd]C bond cleavage

Four new triosmium carbonyl complexes containing multiple dppm ligands were produced by microwave heating of solutions containing Os3(CO)12 and excess dppm. Three of these complexes, Os3(μ-H)2(CO)6(μ-dppm)[μ3-Ph2PCHP(C6H4)Ph] (2), Os3(CO)6[μ3-Ph2PCH2P(C6H4)Ph]2 (3), and Os3(μ-H)(CO)6[μ3-PhPCH2P(C6H4)Ph][μ3-PhPCH(C6H4)PPh] (4), contain two dppm ligands per Os3 unit, while the fourth, Os3(μ-H)(CO)5(dppm)[μ3-PhPCH2P(C6H4)Ph][μ3-PhPCH(C6H4)PPh] (5), is the first example of an Os3 cluster containing three dppm ligands. Microwave heating was also used to prepare the known complex Os3(μ-dppm)2(CO)8 (1) more efficiently than previously reported. The new complexes 2–5 have been characterized by IR, NMR, mass spectrometry, and X-ray crystallography. In addition, the bonding in these complexes has been examined by electronic structure calculations. All of the new complexes contain at least one dppm ligand that has undergone CH and/or CP bond activation. Complex 2 is a 48e cluster that contains one intact dppm ligand and one face-capping dppm ligand that coordinates all three osmium sites through the phosphine moieties and cyclometalated and ortho-metalated carbon atoms. Complex 3 is a 48e cluster with two ortho-metalated dppm ligands while complexes 4 and 5 are 50e clusters that possess a common metallic framework with one cyclometalated dppm ligand and one ortho-metalated dppm ligand.

Small Molecule Activation by Intermolecular Zr(IV)-Phosphine Frustrated Lewis Pairs.

We report intermolecular transition metal frustrated Lewis pairs (FLPs) based on zirconocene aryloxide and phosphine moieties that exhibit a broad range of small molecule activation chemistry that has previously been the preserve of only intramolecular pairs. Reactions with D2, CO2, THF, and PhCCH are reported. By contrast with previous intramolecular examples, these systems allow facile access to a variety of steric and electronic characteristics at the Lewis acidic and Lewis basic components, with the three-step syntheses of 10 new intermolecular transition metal FLPs being reported. Systematic variation to the phosphine Lewis base is used to unravel steric considerations, with the surprising conclusion that phosphines with relatively small Tolman steric parameters not only give highly reactive FLPs but are often seen to have the highest selectivity for the desired product. DOSY NMR spectroscopic studies on these systems reveal for the first time the nature of the Lewis acid/Lewis base interactions in transition metal FLPs of this type.