PPh2 Moiety Research Articles

Mechanistic Exploitations of the Asymmetric α-Allylation of an α-CF3 Amide Enabled by Cu/Pd Synergistic Dual Catalysis.

DFT computational investigations were carried out to explore the mechanism of enantioselective Cu/Pd-catalyzed allylation of an α-CF3 amide. A kinetically favored chiral Cu(I)-enolate species undertakes facile allylation with racemic π-allyl-Pd(II) species to stereoconvergently deliver a stereocenter. Computational models and distortion/interaction analyses unveil versatile modes of stereoinduction wherein the reactive site of (R,Rp)-Walphos/copper(I)-enolate cis to the -PPh2 moiety has more space for the nucleophilic reaction, and can face-selectively capture π-allyl-palladium(II) intermediates using sterically affected distortions.

Reactivity of bulky aminophosphanes towards small molecules: Activation of dihydrogen and carbon dioxide by aminophosphane/borane frustrated Lewis pairs

A series of mono- and bisaminophosphanes with formulas R2NPR’R’’ and (R2N)2PR’ (R = iPr, Cy; R’ = Ph, Cy; R’’ = iPr) were characterized by X-ray analysis, NMR spectroscopy and computational methods. The common structural futures of these species are short and polarized PN bonds, a pyramidal geometry at the P atom and an almost planar geometry at the N atoms. According to DFT calculations, these compounds are highly nucleophilic, with nucleophilic centers located on the N and P atoms. Except for species containing a PPh2 moiety, the obtained aminophosphanes are air-stable and do not react with water. They form stable frustrated Lewis pairs with BPh3 or B(C6F5)3. Mono- and bisaminophosphanes in the presence of B(C6F5)3 activate dihydrogen and carbon dioxide at room temperature.

Palladium-Catalyzed Direct Arylation of Polyfluoroarenes for Accessing Tetra- ortho-Substituted Biaryls: Buchwald-type Ligand Having Complementary -PPh2 Moiety Exhibits Better Efficiency.

The first general examples of direct C-H arylation of electron-deficient polyfluoroarenes with challenging di- ortho-substituted aryl(heteroaryl) chlorides for tetra- ortho-substituted biaryl synthesis are reported. Key to success is the use of Buchwald-type biaryl phosphine ligand, notably with inexpensive -PPh2 moiety (instead of -PCy2 group). Pd(OAc)2 associated with ligand L9 exhibits even higher efficiency than the corresponding SPhos toward this reaction. A wide range of sterically hindered di- ortho-substituted chloroarenes bearing electron-donating or -withdrawing groups are found applicable. Excellent product yields are obtained under mild reaction conditions, and the catalyst loading down to 0.25 mol % of Pd can also be achieved.

Stabilization of the Triphosphallyl Ligand η3‐P3{P(O)H} at Iridium via Alkaline Activation of P4

The selective functionalization of the polyphosphorus moiety Ph2PCH2PPh2PPPP present as a tetrahapto-ligand in complex [Ir(dppm)(Ph2PCH2PPh2PPPP)](+) (1, dppm=Ph2PCH2PPh2) was obtained by reaction of 1 with water under basic conditions at room temperature. The formation of the new triphosphaallyl moiety η(3)-P3{P(O)H} was determined in solution by NMR spectroscopy, and confirmed in the solid state by a single-crystal X-ray structure of the stable product [Ir(κ(2)-dppm)(κ(1)-dppm)(η(3)-P3{P(O)H})] (2). In solution, 2 has a fluxional behavior attributable to the four P atoms belonging to the tetraphosphorus moiety in 1 and exhibits a chemical exchange process involving the two PPh2 moieties of the same bidentate ligand, as determined by 1D and 2D NMR spectroscopy experiments carried out at variable temperature. The mechanism of the reaction was investigated at the DFT level, which suggested a selective attack of an in-situ generated OH(-) anion on one of the non-coordinated phosphorus atoms of the P4 moiety. The reaction then evolves through an acid-assisted tautomerization, which leads to the final compound 2. Bonding analysis pointed out that the new unsubstituted P3-unit in the η(3)-P3{P(O)H} moiety behaves as a triphosphallyl ligand.

Mixed-metal cluster chemistry: 32. Synthesis, structure, and reactivity of a trimetallic molybdenum–iridium carbonyl cluster possessing a μ3-η2-benzyne ligand

The reaction of Mo2Ir2(μ-CO)3(CO)7(η5-C5H5)2 and Ir(CCCH2OH)(CO)(PPh3)3 in refluxing toluene gives the molybdenum–iridium cluster MoIr2(μ3-η2-C6H4)(μ-PPh2)(μ-CO)2(CO)4(η5-C5H5) (1) in low yield. Mo2Ir2(μ-CO)3(CO)6(PPh3)(η5-C5H5)2 (2) is a possible intermediate en route to 1; reaction of Mo2Ir2(μ-CO)3(CO)7(η5-C5H5)2 and Ir(CCCH2OH)(CO)(PPh3)3 in refluxing dichloromethane affords low yields of 2, and thermolysis of the latter in refluxing toluene gives modest yields of 1. A structural study reveals that 1 consists of a triangular MoIr2 core with a molybdenum-bound cyclopentadienyl group, two terminal carbonyls at each of the iridium atoms, one carbonyl bridging each of the Mo–Ir bonds, and a PPh2 moiety spanning the Ir–Ir linkage. The cluster coordination sphere is completed by a face-capping benzyne ligand that ligates η1- to each iridium atom and η2- to the group 6 metal. A structural study of 2 confirms the tetranuclear Mo2Ir2 core with molybdenum-bound cyclopentadienyl groups, six terminal and three-edge-bridging carbonyls, the latter deployed about an MoIr2 face, and a triphenylphosphine ligand ligated axially with respect to the carbonyl-bridged plane. Reaction of 1 with PPh3 in refluxing toluene gives MoIr2(μ3-η2-C6H4)(μ-PPh2)(μ-CO)2(CO)3(PPh3)(η5-C5H5) (3) in low yield. While X-ray structural authentication of 3 has thus far proven elusive, theoretical studies indicate that an equatorially substituted structure is favored energetically over the axially-substituted isomer by around 20kJmol−1, but this energy difference is not sufficiently large so as to exclude formation of the axial isomer experimentally.

Direct Arylation Mediated by Palladium Complexes with Rigid Phosphine-Functionalized N-Heterocyclic Carbenes

New phosphine-functionalized N-heterocyclic carbene ligand precursors (L1H·I and L2H·I) were prepared. The former compound contains a PPh2 moiety, whereas the latter one has a more electron-donating PCy2 group. A reaction of L1H···I with PdCl2 in the presence of base afforded the complex PdL1ClI. An interconversion process between the two structural isomers of PdL1ClI was observed by variable-temperature NMR. The coalescence temperature (Tc) is at 368 K with the free energy of activation (ΔG⧧) found to be 68.9 kJ mol−1. A similar reaction of L2H·I with PdCl2 produced a mixture of PdL2ClI, PdL2Cl2, and PdL2I2. Unlike PdL1ClI, PdL2ClI undergoes a much faster exchange between the two structural isomers. Pure PdLI2 (L = L1 and L2) can be obtained by adding NaI in the reaction mixture to facilitate ligand exchange. [PdL(CH3C≡N)2](BF4)2 were also prepared straightforwardly by salt metathesis reactions. In total, seven new palladium complexes of L were structurally characterized, and in each of these structures an anagostic interaction exists between the palladium center and one of the diastereotopic methylene protons. The interaction also exists in solution, as evidenced by the downfield NMR shift of the proton. The new complexes PdLI2 and [PdL(CH3C≡N)2](BF4)2 show mediocre activities in benchmark Suzuki coupling reactions under conventional and microwave heating. They are, however, highly promising in mediating direct arylation of phenyl halides and diphenylacetylene, affording 9-benzylidene-9H-fluorene in good yields.

Reaction of Rosenthal's Zirconacyclocumulenes with Chlorophosphines

The zirconacyclocumulenes 1a (R = CH3) and 1b (R = Ph) were prepared by isomerization of bis(propynyl)ZrCp2 or bis(phenylethynyl)ZrCp2, respectively, catalyzed by B(C6F5)3 (6 mol %). The compounds 1 added PCl3, PhPCl2, or Ph2PCl with cleavage of only one zirconium−carbon single bond. Chloride was added to zirconium and the remaining −PCl2, −P(Ph)Cl, or −PPh2 moiety attached at the distal β-carbon atom of the strained ZrC4R2 metallacycle to yield the respective ring-opened Zr/P-substituted enyne systems (5−7). The complexes 7a and 7b (both with −PPh2) and 6b (with −P(Ph)Cl) were characterized by X-ray diffraction.

Synthesis and Crystal Structure of a New Triosmium Alkylidyne Carbonyl Cluster Containing a Chiral Ferrocenylphosphine Ligand

The synthesis, spectroscopic characterization and X-ray crystal structure of a new chiral triosmium alkylidyne carbonyl cluster, (R,S)-[Os3(μ-H)2(CO)9{μ3-CPPh2(η5-C5H4)Fe(η5-C5H3(PPh2)CH(Me)NMe2)}] (1) are described. Compound 1 crystallizes in the non-centrosymmetric space group P21 and its absolute configuration has been established. The structure consists of an Os3C metal core with one of the PPh2 moieties of the chiral ferrocenylphosphine bonded to the apical alkylidyne carbon atom to give a zwitterionic cluster complex, reminiscent of the phosphorus ylide.

Coordination behavior of phosphino-phosphaferrocenes: monodentate versus bidentate coordination to divalent palladium

Two novel phosphino-phosphaferrocenes [η5-C5H4(CH2)nPPh2]Fe(η5-PC4H2-2,5-Cy2) (PP1: n=1; PP2: n=2) have been designed and prepared in order to clarify weak chelate effect in the previously reported (η5-C5H4CH2PPh2)Fe[η5-PC4H2-2,5-((–)-menthyl)2] (1). 31P NMR studies of reactions of PP1 with PdCl2(cod) (6) revealed that PP1 showed stronger tendency to coordinate to the PdII center in bidentate fashion compared to 1. On the other hand, chelate effect in PP2 was negligibly weak and a reaction of PP2 with 6 in a PP2/6 = 2/1 molar ratio gave a complex PdCl2(PP2)2 (10) cleanly in which PP2 coordinated to the palladium center at the PPh2 moiety as a monodentate ligand. X-ray crystal structure studies of chelate complexes PdCl2(PP1) (7) and PdCl2(PP2) (9) showed that 9 had deviations from an idealized geometry in the square planar complex which could be attributed to a larger chelate ring of PP2, while PP1 in 7 constructed nearly ideal geometry for the square planar complex.From comparison of the coordination behavior between 1, PP1, and PP2, it is concluded that steric bulk of (–)-menthyl groups in 1 is the main factor of the weak chelate coordination of 1.

(R,R)-1-(N-Benzylideneamino)-2-(diphenylphosphino)cyclohexane-κ2N,P]dichloro(triphenylphosphine-κP)ruthenium(II)

The title compound, [RuCl2(C18H15P)(C25H26NP)], crystallizes with two mol­ecules in the asymmetric unit. The coordination geometry is a distorted square pyramid, with the P atom of the —PPh2 moiety at the apical position. This is the first reported structure determination of a compound containing the (R,R)-1-(N-benzyl­idene­amino)-2-(di­phenyl­phosphino)­cyclo­hexane ligand.

Organometallic chemistry on rhodaheteroborane clusters: reactions with bidentate phosphines and organotransition metal reagents

AbstractThis article reviews our recent work on the reactions of the rhodaheteroboranes [8,8‐(PPh3)2‐nido‐8,7‐RhSB9H10] (1) and [9,9‐(PPh3)2‐nido‐9,7,8‐RhC2B8H11] (2), and their derivatives, with the bidentate phosphines, dppe [(CH2)2(PPh2)2], dppp [(CH2)3(PPh2)2], and dppm [CH2(PPh2)2], and also with organotransition metal reagents. Simple substitution of the two PPh3 ligands by a single bidentate phosphine takes place when a 1 : 1 molar ratio of base (dppe or dppp) to rhodathiaborane (1) is used. However, in the presence of an excess of dppe or dppp, products containing 1 or 2 mol of base are formed. These products include a bidentate ligand on the metal and a monodentate ligand on the cage. The displaced hydrogen atom from the cage has moved to the metal center. These bis(ligand) species are unstable with respect to the loss of dihydrogen, affording closo‐11 vertex clusters with a pendent phosphine ligand on the cage. In concentrated solutions, the pendent phosphine attacks another cage to afford linked clusters. Under both sets of conditions, when dppm is used, only one product is observed. This species has two dppm ligands coordinated to the metal: one in a unidentate mode and the other bidentate. A similar product is obtained in the reaction of 2 with dppm, although the arrangement of the ligands on the metal in the product is different. Ligand exchange experiments on the dppm–thiaborane system lead to results that provide keys to the reaction pathways in some of these processes. The bis(dppm) derivatives of 1 and 2 are amenable to further derivatization. A second metal may be added, either as an exo‐polyhedral atom in a nido cluster in which the metal is part of a bidentate ligand, in the case of 1 and 2, or in a closo cluster derivative of 1 in which the metal is bonded to a dangling PPh2 moiety. Thus, it was possible to add the metals iridium, rhodium or ruthenium to the cluster, in the case of 1 and ruthenium in the case of 2. However, the reaction of more electrophilic organotransition metal reagents, such as Wilkinson's catalyst, with the dppm derivative of 1 affords species resulting from removal of ligand rather than incorporation of metal, and the products shed light on the rearrangement processes in these systems. Copyright © 2003 John Wiley & Sons, Ltd.

Acetylide Participation in Ligand Substitution and P−C Bond Cleavage in the Reaction between HRu3(CO)9(μ3,η2,η2,η1-C⋮CPh) and 4,5-Bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). Syntheses and X-ray Structures of HRu3(CO)7[μ3,η2,η2,η1,η1,η1-Ph2PCCC(O)CH2C(O)PPh2CCPh] and Ru3(CO)7(μ,η2,η1-PhCCHPh)[μ2,η2,η1- PPhCCC(O)CH2C(O)PPh2

The triruthenium cluster HRu3(CO)9(μ3,η2,η2,η1-C⋮CPh) (1) reacts with the diphosphine ligand bpcd in the presence of Me3NO to afford the new cluster compounds HRu3(CO)7(bpcd)(μ3,η2,η2,η1-C⋮CPh) (2) and (3). Cluster 2 is the sole product from the controlled thermolysis of 1 with bpcd. Both 2 and 3 have been isolated and characterized in solution by IR and NMR (1H and 31P) spectroscopies, and by X-ray crystallography in the case of the latter cluster. The bpcd ligand in 2 chelates to the ruthenium center that is σ bound by the acetylide ligand, and in the zwitterionic compound 3 one of the PPh2 moieties of the bpcd ligand coordinates to a hydride-bridged ruthenium atom while the other PPh2 group exists as a phosphonium center due to attack on the acetylide Cα carbon. Whereas 3 slowly decomposes in solution at elevated temperatures, cluster 2 was found to undergo a clean conversion to the new cluster (4). The bridging alkenyl ligand in 4 results from the formal cleavage of one of the P−Ph bonds of the bpcd ligand, followed by the concomitant coupling of the phenyl and hydride groups with the acetylide ligand. Cluster 4 has been fully characterized in solution and the solid-state structure established by X-ray analysis. NMR data are presented from a labeling study employing HRu3(CO)7(bpcd)(μ3,η2,η2,η1-C⋮Ctol-p) that shows that the hydrogen in the μ,η2,η1-RCCHR‘ moiety of is distributed between both the phenyl and tol-p groups. The scrambling of the alkenyl hydrogen between the phenyl- and tol-p-substituted carbon atoms in the μ,η2,η1-RCCHR‘ moiety suggests that hydride transfer from the triruthenium frame occurs via a transient cluster compound that possesses a coordinated PhC⋮Ctol-p ligand.

Formation of Imino−Phosphine Bidentate Chelates by an Unprecedented Organopalladium Complex Promoted Oxidative Coupling Reaction between Diphenylvinylphosphine and Imines

Oxidative coupling reaction between Ph2P−CHCH2 and a series of imines PhC(R)N(R‘) [where R = H, D; R‘ = H, Ph, p-Me(C6H4), p-Cl(C6H4), p-MeO(C6H4)] in the presence of (S)-ortho-palladated[1-(dimethylamino)ethyl]naphthylene as the reaction template produced the unexpected imino−phosphine ligands (R‘)NC−C(CPhR)PPh2 where the P,N-bidentate chelates to the chiral palladium template. The coupling reactions initially adopted a [2+2] cycloaddition mechanism followed by the ring-opening pathway to generate the acyclic ligands. The rate of these coupling reactions was affected by the electronic properties of the R‘ group on the imines. No coupling reaction was observed between Ph2P−CHCH2 and p-CF3(C6H4)NCPh(H), which contains a strong electronic withdrawing group at the p-position. In all the product complexes the nitrogen donors from the imine and from the naphthylamine chelates are coordinated regiospecifically in the cis positions. Similarly the R substituent and the PPh2 moiety are invariably located in the ci...

Room temperature ligand fragmentation in the reaction between PhCCo3(CO)9 and Ph2PN(Me)N(Me)PPh2. X-ray diffraction structure of PhCCo3(CO)8[Ph2PP(O)Ph2

The cobalt cluster PhCCo3(CO)9 reacts with the bis(phosphanyl)hydrazine ligand bis(diphenylphosphino)dimethylhydrazine (dppdmh) in CH2Cl2 with added Me3NO to give the monosubstituted cluster PhCCo3(CO)8[Ph2PP(O)PPh2] as the major isolable product. The solid-state structure of this new cluster was unequivocally established by X-ray diffraction analysis, which has confirmed the presence of a noncoordinated (O)PPh2 moiety. PhCCo3(CO)8[Ph2PP(O)Ph2] crystallizes in the triclinic space group P $$\bar 1$$ , a = 12.036(2), b = 12.037(2), c = 15.124(3) A, α = 84.82(1)°, β = 89.44(2)°, γ = 60.09(1)°, V = 1890.0(6) A3, Z = 2, and dcalc = 1.540 g/cm3.

Enantioselective Catalysis, XV Preparative and Structural Chemistry of Diastereomeric Derivatives of 3‐Phosphanylpyrrolidine and Their Palladium(II) Complexes ‐ Asymmetric Grignard Cross‐Coupling Reaction

AbstractThe preparation of both diastereomeric derivatives of 3‐(diphenylphosphanyl) pyrrolidine with chiral (tetrahydrofuran‐2‐yl)methyl and [(N‐neopentyl)pyrrolidin‐2‐yl]methyl groups as substituents on the pyrrolidine nitrogen atom and of (2S,4S)‐1‐benzyl‐4‐(diphenylphosphanyl)‐2‐(methoxymethyl) pyrrolidine is reported. [3S,P(RS)]‐3‐(phenylphosphanyl) pyrrolidine, bearing an additional chiral center on phosphorus, is the starting material for the preparation of phosphanes, in which one phenyl group of the PPh2 moiety is substituted by an 2‐methoxyphenyl (=An) or 2,4,6‐trimethoxyphenyl (=TMP) group. PdI2 complexes of these ligands were separated into diastereomers by chromatography on silica gel columns. The structural chemistry of these novel phosphane diastereomers and their PdI2 complexes is investigated by X‐ray crystallography and NMR. At the P,N‐coordinated palladium center displacement of an iodide anion is found for P,N,N′ ligands only. In the nickel complex catalysed cross‐coupling reaction, yielding 3‐phenyl‐1‐butene, we obtain the highest enantioselectivities in the case of simple 1‐alkyl‐3‐(diphenylphosphanyl)pyrrolidine ligands. The enantioselectivity obtained with diastereomeric derivatives, bearing additional ether or amine ligating sites is mainly determined by the chiral center in 3‐position of the 3‐(phosphanyl) pyrrolidine part of these ligands. Optimisation of enantioselectivity with these ligands can be carried out by a variation of the ligand to nickel ratio and by the choice of the vinyl halide used as starting compound. The catalytic cycle must contain at least one catalytically active species, bearing more than one β aminoalkylphosphane ligand.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 89. Tetra- and penta-nuclear tungsten–rhodium complexes: crystal structures of [W3Rh2(µ-CO)2(µ-CMe){µ-C(Me)C(O)}(µ-PPh2)2(µ3-CMe)(CO)2(η-C5H5)3] and [W3Rh2(µ-CO)3(µ-CMe){µ-C(Me)PPh2}(µ3-CMe)-(CO)2(ηC5H5)3

Treatment of [Rh2(µ-PPh2)2(cod)2](cod = cyclo-octa-1,5-diene) in thf (tetrahydrofuran) at room temperature with 2 equivalents of [W(CMe)(CO)2(η-C5H5)] rapidly affords the tetranuclear metal complex [W2Rh2(µ-CMe)2(µ-PPh2)2(CO)4(η-C5H5)2](4). If the same reaction is carried out using an excess of the ethylidynetungsten complex two metal cluster compounds are obtained: [W2Rh2(µ-CO){µ-C(Me)C(O)}(µ-PPh2)2(µ3-CMe)(CO)2(η-C5H5)2](5)(formed as a separable mixture of two diastereoisomers) and [W3Rh2(µ-CO)2(µ-CMe){µ-C(Me) C(O)}(µ-PPh2)2(µ3-CMe)(CO)2(η-C5H5)3](6). The structure of the latter was established by X-ray diffraction. The molecule has an essentially planar W(1), Rh(1), W(2), Rh(2), W(3) framework. Carbonyl groups bridge the Rh(1)–W(1) and Rh(2)–W(2) bonds, and PPh2 ligands span the Rh(1)–W(2) and Rh(2)–W(3) linkages. Ethylidyne groups edge-bridge the Rh(1)–W(1) bond and triply bridge the atoms Rh(1)W(2)Rh(2), but the Rh(1)⋯ Rh(2) separation [3.115(4)A] is non-bonding. The Rh(2)–W(3) bond is bridged by a C(Me)C(O) ketenyl group, and the terminal W atoms in the chain each carry a CO ligand and a C5H5 ring. A third C5H5 group ligates W(2). The metal–metal distances fall into two groups [Rh(1)–W(2) 2.791(6), Rh(2)– W(3) 2.813(4); and Rh(1)–W(1) 2.696(5), Rh(2)–W(2) 2.664(5)A], with the shorter separations corresponding to double bonds and the longer to single bonds. Compound (6) is produced by addition of a molecule of [W(CMe)(CO)2(η-C5H5)] to (5), while the latter is formed by isomerisation of (4), a process necessitating migration of µ-CMe and µ-PPh2 between the metal centres. After several hours solutions of (6) in thf afford quantitatively the complex [W3Rh2(µ-CO)3(µ-C(Me){µ-C(Me)PPh2}(µ-PPh2)(µ-CMe)(CO)2(η-C5H5)3](7) an isomer of (6). The structure of (7) was established by X-ray diffraction. An essentially planar metal atom chain W(1), Rh(1), W(2), Rh(2), W(3) forms the spine of the molecule. The various ligands ligate the rhodium and tungsten atoms in a similar manner to those in (6), with the exception of the groups which span the Rh(2)–W(3) bond. This bond is now bridged by a λ5- phospha-alkyne C(Me) PPh2 fragment such that the phosphorus atom ligates W(3) and the carbon atom CMe is bonded to Rh(2) and W(3). The Rh(2)–W(3) bond is also bridged by a CO ligand. Thus the conversion of (6) into (7) involves a novel interchange of CO and PPh2 fragments such that in the former a µ-C(Me)C(O) group is present and in the latter a µ- C(Me)PPh2 moiety. The n.m.r. data (1H, 13C-{1H), and 31P-{1H}) for the new compounds are reported and discussed.

ChemInform Abstract: PREPARATION AND MOLECULAR STRUCTURE OF TAH(P(C6H5)2)2((CH3)2PC2H4P(CH3)2)2, A METAL HYDRIDE OF THE TYPE MHL2(BIDENTATE PHOSPHINE)2N+ HAVING A PENTAGONAL‐BIPYRAMIDAL STRUCTURE

AbstractDie 1:2‐molare Umsetzung von Dichloro‐bis‐[bis‐1,2 (dimethylphosphino)‐ethan]‐Ta mit K‐diphenylphosphid‐2 Dioxan in THF bei 0°C führt zu dem IR‐ und NMR‐spektroskopisch charakterisierten Titelkomplex (I).