Analogous Palladium Research Articles

Capturing a Square Planar Gold(III) Complex Inside a Platinum Nanocage: A Combined Experimental and Theoretical Study.

A novel synthetic procedure was set up to gain access to platinum coordination cages Pt2L4, which are less investigated compared to their palladium counterparts. This Pt2L4 nanocage exhibits an adequate cavity for guest encapsulation. Indeed, the Au(III) metal complex [Au(bdt)2]- (bdt = benzene-1,2-dithiolate) was successfully captured inside the cavity, in contrast to the analogous palladium cage which failed to host the gold complex. This result represents a rare example where a metal complex with thio-ligands can be encapsulated in a coordination cage. Moreover, it highlights the role of the metal center and the robustness of the platinum cage for host-guest chemistry. This discovery will inspire researchers in this area to pay more attention to Pt-cages. The host-guest system was fully characterized by NMR techniques and X-ray crystallographic analysis. Moreover, the nature of the host-guest interaction in this unique example was investigated and rationalized by DFT computational studies.

Bifunctional Pincer Catalysts for Chemoselective Transfer Hydrogenation and Related Reactions

A comparative study on the chemoselective transfer hydrogenation of nitroarenes to anilines and related processes using FA as the hydrogen source is described; these processes are catalyzed by a series of pincer catalysts equipped with different functional groups in the secondary coordination sphere. Some new (4 and 5) as well as previously reported (1–3) catalysts belonging to the family of bifunctional PC(sp3)P pincer complexes were employed in this study The reported compounds exhibited remarkably different catalytic activity behavior, depending on the nature of the functional groups. Transfer hydrogenation of nitrobenzene with FA as a hydrogen source was probed using iridium complexes 3 or 4 as a catalyst. Under the same conditions, the analogous palladium complex was found to be useful for the selective amidation of aniline with light carboxylic acids.

Understanding the differences between iron and palladium in cross-coupling reactions.

We aim at developing design principles, based on quantum chemical analyses, for a novel type of iron-based catalysts that mimic the behavior of their well-known palladium analogs in the bond activation step of cross coupling reactions. To this end, we have systematically explored C–X bond activation via oxidative addition of CH3X substrates (X = H, Cl, CH3) to model catalysts mFe(CO)4q (q = 0, −2; m = singlet, triplet) and, for comparison, Pd(PH3)2 and Pd(CO)2, using relativistic density functional theory at the ZORA-OPBE/TZ2P level. We find that the neutral singlet iron catalyst 1Fe(CO)4 activates all three C–X bonds via barriers that are lower than those for Pd(PH3)2 and Pd(CO)2. This is a direct consequence of the capability of the iron complex to engage not only in π-backdonation, but also in comparably strong σ-donation. Interestingly, whereas the palladium complexes favor C–Cl activation, 1Fe(CO)4 shows a strong preference for activating the C–H bond, with a barrier as low as 10.4 kcal mol−1. Our results suggest a high potential for iron to feature in palladium-type cross-coupling reactions.

Catalytic reactivity of the complexes [Pd{(Ph2P)2N(tBu)-P,P´}X2], X = Cl, Br, I, in the Suzuki-Miyaura C−C coupling reaction: Probing effects of the halogeno ligand X− and the ligand's tBu group

The synthesis, as well as the spectroscopic and structural characterization of three analogous palladium(II) complexes, [Pd{(Ph2P)2N(tBu)-κ2P,P´}X2], X = Cl, Br, I, is presented. X-ray crystallography studies revealed a similar square planar PdP2X2 first coordination sphere among the three complexes. The catalytic reactivity of these complexes was tested in the Suzuki-Miyaura coupling reaction, showing that the X = Cl, Br, complexes are more active than the X = I analogue. The differences in the catalytic reactivity within this series of complexes, as well as comparisons with similar palladium(II) catalysts reported in the literature, are discussed with respect to the different electronegativity of the three halogens and the strong +I inductive effect of the ligand's tBu group.

Reactivity of hemilabile pyridyl- and methyl-substituted pyrimidylselenolates with [MCl2(dppf)] (M = Pd, pt; dppf = bis(diphenylphisphino)ferrocene)

Abstract The bis(diphenylphisphino)ferrocene (dppf) derived palladium analogue of [PdCl2(dppf)] on reaction with the sodium salt of pyridyl/pyrimidyl selenolate yielded mononuclear cis configured complex [Pd(SeAr)2(dppf)] (Ar = C5H4N, C4H(4,6-Me)2N2), as did the platinum precursor [PtCl2(dppf)] with methyl substituted pyrimidyl salt giving [Pt{SeC4H(4,6-Me)2N2}2(dppf)]. In contrast, the reaction of platinum precursor with the sodium salt of pyridylselenolate gave two different complexes [Pt2(μ-SeC5H4N)2(dppf)2]2+ and [Pt(Cl)(SeC5H4N)(dppf)] depending in the reaction solvent. These complexes were characterized by elemental analysis and NMR (1H, 31P) spectroscopy. The molecular structure of [Pt{SeC4H(4,6-Me)2N2}2(dppf)] was established by single crystal X-ray diffraction analysis.

Pd–Ln and Pt–Ln complexes of a bi-compartmental ligand: [MLn(L)(NO3)3] (M = Pd, Pt; Ln = Eu, Tb; H2L = N,N′-bis(3-methoxysalicylidenimino-1,3-diaminopropane))

Abstract The platinum compartment complex [Pt(L)] (1) was synthesized by refluxing a mixture of [PtCl2(SMe2)2], the free ligand (H2L = N,N′-bis(3-methoxysalicylidenimino-1,3-diaminopropane)), and triethylamine in methanol. Complex 1, the first platinum complex of the N2O2–O2O′2-type bi-compartmental ligand, was treated with lanthanide nitrates to give bimetallic Pt–Ln compartment complexes [PtLn(L)(NO3)3] (Ln = Eu (2), Tb (3)). The corresponding palladium analogues, [PdLn(L)(NO3)3] (Ln = Eu (4), Tb (5)), could be prepared from the palladium compartment complex [Pd(L)] and lanthanide nitrates. Structures of all complexes were determined by single X-ray crystallography. Emission quenching of the Ln3+ ions was observed for complexes 2–5 and ascribed to the radiation-less energy loss from excited Ln3+ to M2+ (Ln = Eu, Tb; M = Pd, Pt).

Large d-d luminescence energy variations in square-planar bis(dithiocarbamate) platinum(ii) and palladium(ii) complexes with near-identical MS4 motifs: a variable-pressure study.

We present the variable-pressure luminescence spectra of crystals of isostructural palladium(ii) and platinum(ii) complexes with bis-N-benzyl-N'-3-methylpyridyldithiocarbamate (bmpDTC) ligands. The d-d luminescence band maxima Emax for these complexes are compared to others with different peripheral substituents on the dithiocarbamate ligands in the solid state. The comparison reveals significant variations of Emax despite very similar metal coordination geometries. Emax varies by 3000 cm-1 and 1300 cm-1 among four dithiocarbamate complexes of platinum(ii) and palladium(ii), respectively. Variations of Emax with pressure reveal the effects of intermolecular MH-C interactions on several complexes. ΔEmax/ΔP values are negative for the bmpDTC complexes, unprecedented in the dithiocarbamate family. Static orientation and pressure-induced movement of the C-H bonds involved in intermolecular interactions have a significant effect on Emax and ΔEmax/ΔP, with a stronger impact on platinum(ii) complexes than on their palladium(ii) analogs.

Efficient Synthesis of Unsaturated δ‐ and ε‐Lactones/Lactams by Catalytic Cycloisomerization: When Pt Outperforms Pd

AbstractPlatinum pincer complexes featuring an SCS indenediide backbone have been prepared and evaluated in the catalytic cycloisomerization of alkynoic acids and N‐tosyl alkynylamides. One of the platinum complexes significantly outperforms its palladium analogue for the formation of 6‐ and 7‐membered rings. The catalytic system takes advantage of the alkynophilicity of Pt and of the non‐innocent character of the indenediide framework. Like for Pd, the catalytic performance is significantly improved by using an H‐bond donor additive such as pyrogallol. For the first time, a large variety of ω‐unsaturated δ‐ and ε‐lactones/lactams could be prepared with high selectivities and in very good yields.magnified image

Coordination versatility of p-hydroquinone-functionalized dibenzobarrelene-based PC(sp3)P pincer ligands.

The manuscript describes the synthesis and coordination chemistry of a novel diphosphine pincer ligand based on a p-hydroquinone-functionalized dibenzobarrelene scaffold. The p-hydroquinone fragment of the ligand is oxidatively and coordinatively non-innocent and may render new reactivity to the metal center due to implied reversible redox behavior, tautomeric interconversion and metal-hydroxyl/alkoxide coordination switch of the pendant hydroxyl side-arm. Palladium, platinum and iridium complexes were prepared and characterized. Investigation of their coordination chemistry revealed that while tautomeric equilibrium exists in free ligands and in the chelate non-metalated complexes, it is essentially blocked in the corresponding C(sp3)-pincer compounds due to stabilizing hemilabile coordination of the hydroxyl group. However, its presence in close proximity to the metal center is essential for catalyzing acceptorless dehydrogenation of alcohols by the iridium complexes via the outer-sphere hydrogen transfer mechanism. Remarkably, we found a similar activity for the analogous palladium complexes, which is not characteristic of this metal. This unprecedented reactivity of palladium stresses the fact that besides the choice of an active metal, transformation-oriented design of the ligand is crucial for catalysis.

From NHC to Imidazolyl Ligand: Synthesis of Platinum and Palladium Complexes d10-[M(NHC)2] (M = Pd, Pt) of the NHC 1,3-Diisopropylimidazolin-2-ylidene

The widely held belief that N-heterocyclic carbenes (NHCs) act only as innocent spectator ligands is not always accurate, even in the context of well-explored reactions. Ligand exchange in the conversion of [Pt(PPh3)2(η2-C2H4)] (3) to [Pt(iPr2Im)2] (2) depends critically on the particular reaction conditions employed, with slight changes leading to vastly different outcomes. In addition to [Pt(iPr2Im)2] (2), complexes [Pt(iPr2Im)(PPh3)(η2-C2H4)] (5) and trans-[Pt(iPr2Im)2(iPr-Im*)(H)] (6) were isolated and in the case of 6 fully characterized. Complex 5 represents the first mixed-olefin complex in transition metal chemistry containing both an NHC and a phosphine ligand. Chemical degradation of the NHC was shown to yield the new imidazole-2-yl iPr-Im* in 6. Therefore, the synthesis of [Pt(iPr2Im)2] (2) via metallic reduction of the ionic precursor [Pt(iPr2Im)3(Cl)]+Cl– (9) is favorable, a procedure adaptable to analogous palladium compounds. While [Pd(iPr2Im)3(Cl)]+Cl– (8) is the only product obtained from...

Benzoato and Thiobenzoato Ligands in the Synthesis of Dinuclear Palladium(III) and ‐(II) Compounds: Stability and Catalytic Applications

AbstractNew palladium(III) compounds of formula Pd2[(C6H4)PPh2]2[OXC(C6H5)]2Cl2 [3a (X = O); 3b (X = S)] were obtained by the oxidation of the analogous palladium(II) ones with PhICl2 and were characterized by 31P, 1H, and 13C NMR spectroscopy at 223 K. Compound 3a was also structurally characterized by single‐crystal X‐ray diffraction methods, which revealed a Pd–Pd distance of 2.5212(10) Å. DFT calculations were conducted to study the stability of all of these new palladium(III) and ‐(II) compounds with focus on the influence of the O↔S substitution of the donor atom in the ligand. The palladium(II) compounds Pd2[(C6H4)PPh2]2[OXC(C6H5)]2 [2a (X = O), 2b (X = S)] were also tested as precatalyst in two reactions: (1) the acetoxylation of 2‐phenylpyridine and (2) the room‐temperature 2‐phenylation of indoles. Compound 2b is a better precatalyst than 2a in the first reaction (4 h; isolated yield, 67.5 vs. 50.4 %). In the second catalytic reaction, isolated yields of 97 (10 h, substrate: 1‐methylindole) and 99 % (24 h, substrate: indole) were obtained with 2a as the precatalyst, whereas 2b gave low or no conversion.

Reactions of phenylacetylene with nickel POCOP-pincer hydride complexes resulting in different outcomes from their palladium analogues.

Nickel POCOP-pincer hydride complexes [2,6-(R2PO)2C6H3]NiH (R = (I)Pr, 4a; R = (c)Pe = cyclopentyl, 4b) react with phenylacetylene to generate [2,6-(R2PO)2C6H3]NiC(Ph)=CH2 (5a–b) as the major product and (E)-[2,6-(R2PO)2C6H3]NiCH=CHPh (6a–b) as the minor product. The 2,1-insertion is more favorable than the 1,2-insertion and both pathways involve cis addition of Ni–H across the C≡C bond. Unlike the palladium case, alkynyl complexes [2,6-(R2PO)2C6H3]NiC≡CPh (7a–b) and H2 are not produced in the nickel system. The more bulky hydride complex [2,6-((t)Bu2PO)2C6H3]NiH (4c) shows no reactivity towards phenylacetylene. Catalytic hydrogenation of phenylacetylene with 4a–b takes place at an elevated temperature (70–100 °C) and proves to be heterogeneous. The structures of 5b, 6a, 7a and 7b have been studied by X-ray crystallography.

Higher fluorescence in platinum(iv) orthometallated complexes of perylene imine compared with their platinum(ii) or palladium(ii) analogues.

The reaction of 3-perylenylmethylen-4'-ethylaniline () with [Pt2Me4(μ-SMe2)2] (and subsequent addition of PPh3) or with [Pt2(η(3)-C4H7)2(μ-Cl)2] produced cyclometallated Pt(II) complexes [Pt(C^N)Me(PPh3)] () and, respectively, [Pt2(C^N)2(μ-Cl)2] () (HC^N = 3-C20H11CH[double bond, length as m-dash]NC6H4-p-C2H5), with Pt bound to the ortho site of the perylenyl fragment. From the mononuclear complexes [Pt(C^N)L2] (L2 = acac (); S2COMe (); S2CNEt2 () are easily formed. Oxidative addition of methyl iodide to the square-planar Pt(II) complexes , , and gave the corresponding cyclometallated Pt(IV) compounds [Pt(C^N)L2MeI] , and . The X-ray structures of , , and show that the perylenyl fragment remains essentially flat in and and slightly twisted in . Comparison of the optical properties of these Pt(II) complexes with those reported for similar Pd(II) derivatives reveals that the change of metal exerts a notable influence on the UV-vis spectra. In solution at room temperature, all the Pt complexes exhibit fluorescence associated with the perylene fragment with low emission quantum yields for the Pt(II) complexes (<1%) and remarkably higher emission values for the Pt(IV) complexes: up to 29%, with emission lifetimes of 1-5 ns. Time-dependent density functional theory (TD-DFT) calculations were performed on the perylene imine and on representative complexes [M(C^N)(acac)] (M = Pd, Pt) and [Pt(C^N)(acac)MeI] to analyse the absorption spectra. These calculations support a perylene-dominated intraligand π-π*emissive state based on the HOMO and LUMO orbitals of the perylene chromophore, and a ligand-to-ligand charge-transfer (more intense for the Pt(II) complex) that explains the observed influence of the metal on the absorption properties.

Heterometallic complexes with cube-type [MTi3N4] cores containing Group 10 metals in a variety of oxidation states.

Treatment of [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)] (1) with one equivalent of [Ni(cod)2] (cod = 1,5-cyclooctadiene) in toluene at 60–80 °C and subsequent addition of diphenylacetylene, trans-stilbene or triphenylphosphane afforded the nickel(0) complexes [LNi{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (L = PhCCPh (2), PhCH≡CHPh (3), PPh3 (4)). The nickel(II) complex [I2Ni{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (5) was prepared by analogous addition of iodine to the solution obtained from the heating of 1 and [Ni(cod)2]. Treatment of 1 with one equivalent of [Pd(dba)2] (dba = dibenzylideneacetone) in toluene at room temperature led to the palladium(0) complex [(dba)Pd{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (6). Compound 6 reacted immediately with chloroform-d1 to give the palladium dichloride derivative [Cl2Pd{(μ3-NH)2Ti3(η5-C5Me5)3(μ-NH)(μ3-N)}] (7), which was prepared by treatment of 1 with [PdCl2(cod)] at room temperature. Addition of iodine to a toluene solution of 6 afforded the analogous palladium(II) derivative [I2Pd{(μ3-NH)2Ti3(η5-C5Me5)3(μ-NH)(μ3-N)}] (8). Complex 6 reacted with two equivalents of dimethylacetylenedicarboxylate (dmad) to give the metallacyclopentadiene palladium(II) complex [{(MeOOC)4C4}Pd{(μ3-NH)2Ti3(η5-C5Me5)3(μ-NH)(μ3-N)}] (9) via oxidative coupling. The treatment of 1 with [Pt(nbe)3] (nbe = norbornene) in toluene at room temperature gave the platinum(0) complex [(nbe)Pt{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (10). Compound 10 reacted with excess iodine to afford the platinum(IV) ionic derivative [I3Pt{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}]2(I3)(I5) (11) via an intermediate platinum(II) complex [I2Pt{(μ3-NH)2Ti3(η5-C5Me5)3(μ-NH)(μ3-N)}] (12). The X-ray crystal structures of 5, 8, 9 and 11 have been determined.

Kinetico-Mechanistic Insights on the Assembling Dynamics of Allyl-Cornered Metallacycles: The PtNpyBond is the Keystone

The square-like homo- and heterometallamacrocycles [{Pd(η(3) -2-Me-C3 H4 )(L(n) )2 }2 {M(dppp)}2 ](CF3 SO3 )6 (dppp=1,3-bis(diphenylphosphino)propane) and [{Pd(η(3) -2-Me-C3 H4 )(L(1) )2 }2 {M(PPh3 )2 }2 ](CF3 SO3 )6 [py=pyridine, M=Pd, Pt, L(n=) 4-PPh2 py (L(1) ), 4-C6 F4 PPh2 py (L(2) )] containing allyl corners were synthesised by antisymbiotic self-assembly of the different palladium and platinum metallic corners and the ambidentate N,P ligands. All the synthesised assemblies displayed a complex dynamic behaviour in solution, the rate of which is found to be dependent on the electronic and/or steric nature of the different building blocks. A kinetico-mechanistic study by NMR line shape analysis of the dynamics of some of these assemblies was undertaken in order to determine the corresponding thermal activation parameters. Both an enhanced thermodynamic stability and slower dynamics were observed for platinum-pyridine-containing species when compared with their palladium analogues. Time-dependent NMR spectroscopy in combination with ESI mass spectrometry was used to study the exchange between the assemblies and their building blocks, as well as that occurring between different metallamacrocycles. Preliminary studies were carried out on the activity of some of the metallamacrocyclic compounds as catalytic precursors in the allylic substitution reaction, and the results compared with that of the monometallic allylic corner [Pd(η(3) -2-Me-C3 H4 )(L(1) )2 ](+) .

A structural and spectroscopic investigation of octahedral platinum bis(dithiolene)phosphine complexes: platinum dithiolene internal redox chemistry induced by phosphine association.

The complexes [Pt(mdt)2] (4; mdt = methyldithiolene, [Me2C2S2](n-)), [Pt(adt)2] (5; adt = p-anisyldithiolene, [(MeO-p-C6H4)2C2S2](n-)), and [Pd(adt)2] (10) have been prepared in yields of ≥90% via transmetalation reactions with the corresponding [R2Sn(S2C2R'2)] complexes (R = (n)Bu, R' = Me; R = Me, R' = -C6H4-p-OMe, 3). Intraligand C-S and C-Cchelate bond lengths (~1.71 and ~1.40 Å, respectively) obtained by X-ray crystallography show these compounds to be comprised of radical monoanions mdt(•-) and adt(•-). The six-coordinate octahedral adducts [Pt(adt)2(dppe)] [6; dppe = 1,2-bis(diphenylphosphino)ethane], trans-[Pt(adt)2(PMe3)2] (8), and trans-[Pt(mdt)2(PMe3)2] (9) have also been prepared, and crystal structures reveal dithiolene ligands that are fully reduced ene-1,2-dithiolates (C-S and C-C(chelate) = ~1.77 and 1.35 Å, respectively). Reduction of the dithiolene ligand thus occurs to accommodate the +IV oxidation state typical of octahedral six-coordinate platinum. The cyclic voltammogram of 5 shows two fully reversible reductions at -0.11 and -0.84 V in CH2Cl2 (vs Ag/AgCl), attributed to successive (adt(•-) + e(-) → adt(2-)) processes, and a reversible oxidation at +1.01 V. The cyclic voltammogram of 9 shows two reversible oxidations at +0.38 and +0.86 V, which are assigned as successive (adt(2-) → adt(•-) + e(-)) oxidations. Consistent with their formulation as having fully reduced dithiolene ligands, the UV-vis spectra for 6, 8, and 9 show no low-energy absorptions below 700 nm, and the S K-edge XAS spectra of 6 and 8 show dithiolene sulfur that is reduced relative to that in 5. The introduction of PMe3 to 10 did not produce the palladium analogue of 8 but rather [Pd(adt)(PMe3)2] (11). The reaction of [PdCl2(PPh3)2] with Li2(mdt) produced a mixture of [Pd(mdt)(PPh3)2] (12, 20%) and [(Ph3P)Pd(μ-1,2-mdt-S,S':S)2Pd(PPh3)] (13, 28%), with the latter having C2 symmetry with a Pd2S2 core structure folded along the S···S axis.

Ortho-Metallated triphenylphosphine chalcogenide complexes of platinum and palladium: synthesis and catalytic activity.

Treatment of [PtI2(COD)] (COD = 1,5-cyclooctadiene) with 2-LiC6H4P(S)Ph2 gives the complex cis-[Pt{κ(2)-2-C6H4P(S)Ph2}2] () containing a pair of ortho-metallated triphenylphosphine sulfide rings. The selenium counterpart, [Pt{κ(2)-2-C6H4P(Se)Ph2}2] (), which exists as cis- and trans-isomers in solution, and the palladium analogues, cis-[Pd{κ(2)-2-C6H4P(X)Ph2}2] [X = S (), Se ()], are obtained by transmetallation of [MCl2(COD)] with the organotin reagent 2-Me3SnC6H4P(X)Ph2 in a 1 : 2 mol ratio. The reaction of [PdCl2(COD)] with 2-Me3SnC6H4P(X)Ph2 in a 1 : 1 mol ratio, and the reaction of with palladium(ii) acetate, give dinuclear, anion-bridged complexes [Pd2(μ-Cl)2{κ(2)-2-C6H4P(X)Ph2}2] [X = S (), Se ()] and [Pd2(μ-OAc)2{κ(2)-2-C6H4P(S)Ph2}2] (), respectively. Complexes and could not be made directly from triphenylphosphine sulfide by standard ortho-palladation procedures. The bridging framework in complexes and is cleaved by tertiary phosphines to give mononuclear derivatives [PdCl{κ(2)-2-C6H4P(X)Ph2}(PR3)] [X = S, R = Ph (); X = Se, R = Ph (); X = Se, R = 4-tolyl ()]. The selenium-containing compounds and decompose slowly in solution giving dinuclear complexes [PdCl(μ2-Se-κ(2)-P,Se-2-SeC6H4PPh2)PdCl(μ-2-C6H4PPh2)(PR3)] [R = Ph (), 4-tolyl ()]. The structure of complex establishes that the bridging 2-C6H4PPh2 group is generated by reduction of the phosphine selenide unit, not by ortho-metallation of the coordinated triphenylphosphine. The chloro-bridges of and are also cleaved by acetylacetonate (acac) and deprotonated Schiff bases forming mononuclear species [Pd{κ(2)-2-C6H4P(X)Ph2}L2] [L2 = acac, X = S (), Se (); L2 = 2-OC6H4CH[double bond, length as m-dash]NC6H4-4-R, X = S, R = OMe (), NO2 (); X = Se, R = OMe (), NO2 ()]. The ability of complexes , and the Schiff base-derivatives to catalyse Heck-Mizoroki and Suzuki-Miyaura C-C bond-forming reactions has also been investigated.

Mesoporous Gold and Palladium Nanoleaves from Liquid–Liquid Interface: Enhanced Catalytic Activity of the Palladium Analogue toward Hydrazine-Assisted Room-Temperature 4-Nitrophenol Reduction

The importance of an interfacial reaction to obtain mesoporous leafy nanostructures of gold and palladium has been reported. A new synthetic strategy involving 1,4-dihydropyridine ester (DHPE) as a potential reducing agent performs exceptionally well for the desired morphologies of both the noble metals at room temperature. The DHPE in turn transforms into its oxidized aromatic form. The as-synthesized gold leaves exhibit high surface-enhanced Raman scattering activity with rhodamine 6G (R6G) due to their hyperbranched structure. It is worthwhile that as-synthesized porous architectures of palladium support the room-temperature hydrogenation of 4-nitrophenol (4-NP) by hydrazine hydrate (N2H4·H2O), reported for the first time. Furthermore, MPL exhibits exceptionally good catalytic activity toward electrooxidation of formic acid. Therefore, an aromaticity driven synthetic technique achieves a rationale to design leafy nanostructures of noble metals from the liquid-liquid interface for multifaceted applications.

Stability and Reactivity of Cyclometallated Naphthylamine Complexes in Pd–C Bond Insertion Reactions with Coordinated Alkynylphosphanes

AbstractPhenylbis(phenylethynyl)phosphane PhP(C≡CPh)2 coordinates regiospecifically to the α‐methyl‐chiral ortho‐platinated and ‐palladated naphthylamine units at the positions trans to the nitrogen donors. The P→Pt coordination bond is kinetically inert, whereas the P→Pd bond is labile. Upon heating of these phosphane complexes at 70 °C, one of the C≡C bonds in the coordinated PhP(C≡CPh)2 was activated towards an intermolecular Pd–C bond insertion reaction with an external ortho‐palladated naphthylamine ring. No intramolecular insertion reaction occurred. In contrast to its palladium analogue, the ortho‐platinated ring is not reactive towards coordinated PhP(C≡CPh)2, although it can promote the Pd–C bond insertion reaction. However, despite the high kinetic stability of the P→Pt coordination, the organoplatinum unit is a noticeably weaker activator than its organopalladium counterpart. The chirality of the reacting ortho‐metallated naphthylamine ligand exhibited high stereochemical influence on the formation of the new stereogenic phosphorus center during the course of these C–C bond‐formation reactions. The coordination chemistry and the absolute stereochemistry of the dimetallic products were determined by single‐crystal X‐ray crystallographic analysis.

New bisphosphomide ligands, 1,3-phenylenebis((diphenylphosphino)methanone) and (2-bromo-1,3-phenylene)bis((diphenylphosphino)methanone): synthesis, coordination behavior, DFT calculations and catalytic studies

The bisphosphomide, 1,3-{Ph2PC(O)}2C6H4 (1), was prepared by the reaction of isophthaloyl chloride with diphenylphosphine in the presence of triethylamine. The corresponding bromo-derivative, 2-Br-1,3-{Ph2PC(O)}2C6H3 (2), was obtained by the reaction of 2-bromoisophthaloyl chloride with diphenylphosphine. The reaction of 1 with elemental sulfur or selenium yielded the bis(chalcogenides), 1,3-{Ph2P(S)C(O)}2C6H4 (3) and {1,3-Ph2P(Se)C(O)}2C6H4 (4). The reaction between 1 and [Ru(η(6)-p-cymene)Cl2]2 and [Pd(η(3)-C3H5)Cl]2 in 1 : 1 stoichiometry yielded the corresponding binuclear complexes, [Ru2(η(6)-p-cymene)2Cl4{1,3-{Ph2PC(O)}2(C6H4)}] (5) and [Pd2(η(3)-C3H5)2Cl2{1,3-{Ph2PC(O)}2(C6H4)}] (6). The reaction of 1 with AgClO4 followed by the addition of [Pd(COD)Cl2] at room temperature resulted in the formation of a pincer complex [PdCl{2,6-{Ph2PC(O)}2(C6H3)}] (9), via transmetallation. Pincer complex formation through C-H activation requires drastic conditions and yields are generally moderate. The oxidative addition reaction between 2 and [Ni(COD)2] gave a pincer complex [NiBr{2,6-{Ph2PC(O)}2(C6H3)}] (8), whereas the 2:1 reaction of 2 with [Pd2(dba)3] yielded the palladium analogue [PdBr{2,6-{Ph2PC(O)}2(C6H3)}] (9) in quantitative yield. The reaction between 1 and CuX in a 1:1 molar ratio produced binuclear complexes, [Cu2(μ-X)2{1,3-{Ph2PC(O)}2(C6H4)}2] (10, X = Cl; 11, X = Br; 12, X = I), whereas the reaction between 1 and [Cu(NCCH3)4]BF4 led to the isolation of a spirocyclic complex, [Cu(CH3CN)2{1,3-{Ph2PC(O)}2(C6H4)}]BF4 (13). The silver complexes [Ag2(μ-ClO4)2{1,3-{Ph2PC(O)}2(C6H4)}2] (14), [Ag2(μ-OTf)2{1,3-{Ph2PC(O)}2(C6H4)}2] (15) and [Ag2X2{1,3-{Ph2PC(O)}2(C6H4)}] (16, X = ClO4; 17, X = OTf) were obtained by treating 1 with AgClO4 or AgOTf in 1:1 or 1:2 molar ratios. The reactions of 1 with [AuCl(SMe2)] in 1 : 1 and 1 : 2 molar ratios afforded mono- and binuclear complexes, [AuCl{1,3-{Ph2PC(O)}2(C6H4)}2] (18) and [Au2Cl2{1,3-{Ph2PC(O)}2(C6H4)}AuCl] (19), in good yield. The structures of complexes 5, 7-10, 12 and 14a were confirmed by single-crystal X-ray diffraction studies. DFT calculations were performed in order to gain additional insights into the structure and bonding of the pincer complexes. An additional analysis of the orbital interactions in the case of palladium complex 9 is also included. The in situ generated rhodium complex of bisphosphomide 1 showed moderate to good selectivity in the hydroformylation of hex-1-ene and styrene derivatives.