Ph PCH Research Articles

Antibactericidal Ir(III) and Ru(II) Complexes with Phosphine-Alkaloid Conjugate and Their Interactions with Biomolecules: A Case of N-Methylphenethylamine.

The phosphine ligand (Ph2 PCH2 N(CH3 )(CH2 )2 Ph, PNMPEA) obtained by the reaction of the (hydroxymethyl)diphenylphosphine with naturally occurring alkaloid N-methylphenethylamine, was used to synthesize the half-sandwich iridium(III) (Ir(η5 -Cp*)Cl2 Ph2 PCH2 N(CH3 )(CH2 )2 Ph, IrPNMPEA) and ruthenium(II) (Ru(η6 -p-cymene)Cl2 Ph2 PCH2 N(CH3 )(CH2 )2 Ph, RuPNMPEA) complexes. They were characterized using a vast array of methods, including 1D and 2D NMR, ESI(+)MS spectrometry, elemental analysis, cyclic voltammetry (CV), electron spectroscopy in the UV-Vis range (absorption, fluorescence) and density functional theory (DFT). The initial antimicrobial activity in vitro toward Gram-positive and Gram-negative bacterial strains was examined, indicating that both complexes are selective towards Gram-positive bacteria, e. g., Staphylococcus aureus, where the IrPNMPEA has been more bactericidal compared to RuPNMPEA. Additionally, the interactions of these compounds with various biomolecules, such as DNA (ctDNA, plasmid DNA, 9-ethylguanine (9-EtG), and 9-methyladenine (9-MeA)), nicotinamide adenine dinucleotide (NADH), glutathione (GSH), and ascorbic acid (Asc) were described. The results showed that both Ir(III) and Ru(II) complexes accelerate the oxidation process of NADH, GSH and Asc that appeared to occur by an electron transfer mechanism. Interestingly, only IrPNMPEA leads to the formation of various biomolecule adducts, which can explain its higher activity. Furthermore, RuPNMPEA and IrPNMPEA have been interacting with the DNA through weak noncovalent interactions.

Cationic Tetrylene-Iron(0) Complexes: Access Points for Cooperative, Reversible Bond Activation and Open-Shell Iron(-I) Ferrato-Tetrylenes.

The open-shell cationic stannylene-iron(0) complex 4 (4=[PhiP DippSn⋅Fe⋅IPr]+ ; PhiP Dipp={[Ph2 PCH2 Si(i Pr)2 ](Dipp)N}; Dipp=2,6-i Pr2 C6 H3 ; IPr=[(Dipp)NC(H)]2 C:) cooperatively and reversibly cleaves dihydrogen at the Sn-Fe interface under mild conditions (1.5 bar, 298 K), in forming bridging hydrido-complex 6. The One-electron oreduction of the related GeII -Fe0 complex 3 leads to oxidative addition of one C-P linkage of the PhiP Dipp ligand in an intermediary Fe-I complex, leading to FeI phosphide species 7. One-electron reduction reaction of 4 gives access to the iron(-I) ferrato-stannylene, 8, giving evidence for the transient formation of such a species in the reduction of 3. The covalently bound tin(II)-iron(-I) compound 8 has been characterised through EPR spectroscopy, SQUID magnetometry, and supporting computational analysis, which strongly indicate a high localization of electron spin density at Fe-I in this unique d9 -iron complex.

Polyphosphinoborane Block Copolymer Synthesis Using Catalytic Reversible Chain-Transfer Dehydropolymerization.

An amphiphilic block copolymer of polyphosphinoborane has been prepared by a mechanism-led strategy of the sequential catalytic dehydropolymerization of precursor monomers, H3 B ⋅ PRH2 (R=Ph, n-hexyl), using the simple pre-catalyst [Rh(Ph2 PCH2 CH2 PPh2 )2 ]Cl. Speciation, mechanism and polymer chain growth studies support a step-growth process where reversible chain transfer occurs, i.e. H3 B ⋅ PRH2 /oligomer/polymer can all coordinate with, and be activated by, the catalyst. Block copolymer [H2 BPPhH]110 -b-[H2 BP(n-hexyl)H]11 can be synthesized and self-assembles in solution to form either rod-like micelles or vesicles depending on solvent polarity.

Transition Metal Complexes of 2,6‐Dibenzhydryl Derived Bisphosphine: Synthesis, Structural Studies and Palladium Complex Promoted Suzuki‐Miyaura Reactions

AbstractTransition metal chemistry of [Ar*N(CH2PPh2)2] (1) derived from the sterically demanding backbone 2,6‐dibenzhydryl‐4‐methylphenyl core is described. The reactions of 1 with 30 % aq. H2O2 and S8 afforded bischalcogenides [Ar*N(CH2P(O)Ph2)2] (2) and [Ar*N(CH2P(S)Ph2)2] (3), respectively. Treatment of 1 with [M(COD)Cl2] (M=Pd, Pt) in 1 : 1 molar ratios produced chelate complexes cis‐[MCl2{Ar*N(CH2PPh2)2}‐κ2‐P,P] (4, M=Pd; 5, M=Pt), whereas similar reaction between 1 and [Pd(η3‐C3H5)Cl]2 afforded dinuclear complex [{Pd(η3‐C3H5)Cl}2{Ar*N(CH2PPh2)2}‐κ1‐P,P] (6). The reaction of 1 with [Ru(η5‐C5H5)Cl(PPh3)2] in 1 : 1 ratio yielded [{Ru(η5‐C5H5)Cl}{Ar*N(CH2PPh2)2}‐κ2‐P,P] (7). Treatment of 1 with [M(C5H11N)2(CO)4] (M=Mo, W) in 1 : 1 molar ratios afforded cis‐[M(CO)4{Ar*N(CH2PPh2)2}‐κ2‐P,P] (8, M=Mo; 9, M=W). The reaction of 1 with copper(I) halides in 1 : 1 molar ratios produced [Cu(μ2‐X)]2 dinuclear complexes [{Cu(μ2‐X)}2{Ar*N(CH2PPh2)2}2‐κ2‐P,P}] [10, X=Cl; 11, X=Br; and 12, X=I]. Most of these compounds show various C−H⋅⋅⋅π interactions. Bischalcogenides 2 and 3 showed intramolecular hydrogen bonding type interactions, C−H⋅⋅⋅O (2.554 Å) and C−H⋅⋅⋅S (2.825 Å) between the methylene hydrogens of –NCH2PPh2 groups with O or S atoms, which was also evinced by QTAIM and NCI analysis. Bisphosphine 1 was found to be very effective in palladium catalyzed Suzuki‐Miyaura couplings of aryl chlorides with aryl boronic acids.

Review of Calixarene-Derivatives in Transition Metal Chemistry

The survey depicts the combination of large-scale monodentate phosphites in response to PCl3/NEt3 with p-tert-butyl calix[4]-(OH)3-OR, where R contains an oxygen-containing substituent (R = CH2P(O)Ph2, -CH2CO2Et, -CH2C(O)NEt2, -CH2CH2OMe). These funnel-shaped calissarenes have a phosphorus particle bridging three phenolic oxygen atoms, and are incredibly steady in NaOH-aqueous arrangement due to the cone point being more noteworthy than 180°. Upon response with transition metal particles, these phosphites shape either P monodentate complexes or expansive P,O chelate complexes including the oxygen atom of the R group. The reactivity of four different ligands in the rhodium-catalyzed hydroformylation of octene was examined. The general trend is that a bulkier phosphite ligand leads to a slower reaction rate. The ligand-to-base ratios ranged from 1.4 to 3.6, and the highest straight aldehyde selectivity was observed when the carboxylate group was CH2CO2Et.

Geometrically Constrained Cationic Low-Coordinate Tetrylenes: Highly Lewis Acidic σ-Donor Ligands in Catalytic Systems.

A novel non‐innocent ligand class, namely cationic single‐centre ambiphiles, is reported in the phosphine‐functionalised cationic tetrylene Ni0 complexes, [PhRDippENi(PPh3)3]+ (4 a/b (Ge) and 5 (Sn); PhRDipp={[Ph2PCH2SiR2](Dipp)N}−; R=Ph, iPr; Dipp=2,6‐iPr2C6H3). The inherent electronic nature of low‐coordinate tetryliumylidenes, combined with the geometrically constrained [N−E−Ni] bending angle enforced by the chelating phosphine arm in these complexes, leads to strongly electrophilic EII centres which readily bind nucleophiles, reversibly in the case of NH3. Further, the GeII centre in 4 a/b readily abstracts the fluoride ion from [SbF6]− to form the fluoro‐germylene complex PhRDippGe(F)Ni(PPh3)3 9, despite this GeII centre simultaneously being a σ‐donating ligand towards Ni0. Alongside the observed catalytic ability of 4 and 5 in the hydrosilylation of alkynes and alkenes, this forms an exciting introduction to a multi‐talented ligand class in cationic single‐centre ambiphiles.

Mono- and di-phosphine oxide complexes of aluminium, gallium and indium with weakly coordinating triflate anions – Synthesis, structures and properties

Reaction of the Group 13 triflates, M(OTf)3 (M = Al, Ga, In; OTf = CF3SO3−), with 3 mol. eq. of R3PO (R = Ph or Me) gives the six-coordinate complexes, [M(OTf)3(R3PO)3], with coordinated triflate, as white powdered solids. Similarly, using 3 mol. eq. of PyNO (pyridine-N-oxide) readily forms [In(OTf)3(PyNO)3], whose crystal structure confirms a mer octahedral arrangement. In contrast, reaction of the harder Lewis acids Al(III) and Ga(III) with PyNO produce mixtures, mostly likely of the 3:1 and 4:1 species, [M(OTf)3(PyNO)3] and [M(OTf)2(PyNO)4][OTf] (M = Al, Ga). Both of the tetrakis species have been confirmed via single crystal X-ray studies and shown to exist as trans isomers. Higher ratios (4:1, 5:1 and 6:1) of Me3PO coordinated to In(OTf)3 can also be achieved by varying the reaction stoichiometry appropriately, with the coordinated OTf groups readily displaced by the Me3PO.Crystal structures of two polymorphs of the salt, [In(OTf)2(Me3PO)4][In{(OH2)2(OTf)4}(Me3PO)4], in which the [In{(OH2)2(OTf)4}(Me3PO)4]− anion is (unusually) comprised of a ‘InIII(OH2)2(Me3PO)4′ unit with four OTf anions H-bonded to the aquo ligands, giving the overall monoanionic charge. A similar arrangement is present in [In(OTf)2(Ph3PO)4][In{(OH2)4(OTf)4}(Ph3PO)2], the structure of which shows that all of the H atoms associated with the four aquo ligands in the [In{(OH2)4(OTf)4}(Ph3PO)2]− form significant H-bonds to the OTf groups; specifically, the four OTf− anions each show two O⋯H interactions, forming bridges that link the equatorial aquo ligands into a 24-membered ‘pseudo-macrocyclic’ ring. The crystal structure of the mononuclear 5:1 complex, [Ga(Me3PO)5(MeCN)][OTf]3, is also described.Using the diphosphine dioxide, dppmO2 (Ph2P(O)CH2P(O)Ph2), with M(OTf)3 in a 3:1 ratio readily affords the tris-chelate species, [M(dppmO2)3][OTf]3 for all three metals, while a 2:1 ratio also gives [Ga(OTf)2(dppmO2)2][OTf]. Crystal structures of both [Al(dppmO2)3][OTf]3·MeCN and [Ga(dppmO2)3][OTf]3·2CHCl3 are reported.Multinuclear (1H, 13C{1H}, 19F{1H}, 31P{1H}, 27Al, 71Ga and 115In, where appropriate) NMR data show that in CD3CN the complexes are labile and the different R3PO coordination environments are not distinguished (although exchange between coordinated and ‘free’ Me3PO is slow on the 31P NMR timescale), while the MeCN solvent also replaces OTf in the metal coordination sphere.

Octapalladium Strings Trap C60 and C70 Fullerenes Affording Metal-Chain-Wired Bucky Balls.

Reactions of Pd8 strings supported by meso-Ph2 PCH2 P(Ph)CH2 P(Ph)CH2 PPh2 (meso-dpmppm) ligands, [Pd8 (meso-dpmppm)4 (L)2 ]4+ (L=CH3 CN (1), XylNC (2)) with C60 resulted in the exclusive formation of unprecedented metal-chain-wired C60 bucky balls, [{Pd4 (meso-dpmppm)2 (L)}2 (C60 )]4+ (L=CH3 CN (11), XylNC (12)), in which a C60 fullerene is trapped in the central Pd-Pd junction, as unambiguously established by spectroscopic, X-ray crystallographic, and theoretical techniques. The similar reaction of Pd8 strings supported by rac-dpmppm, [Pd8 (rac-dpmppm)4 (CH3 CN)2 ]4+ (3) also afforded a racemic mixture of [{Pd4 ((R*,R*)-dpmppm)2 (CH3 CN)}2 (C60 )]4+ (13) without scrambling the Pd4 fragments with (R,R)- and (S,S)-dpmppm ligands. Consequently, those of enantiopure chiral Pd8 strings, [Pd8 ((R*,R*)-dpmppm)4 (CH3 CN)2 ]4+ , certainly afforded chiral bucky balls of [{Pd4 ((R*,R*)-dpmppm)2 (CH3 CN)}2 (C60 )]4+ (13RR and 13SS ), that exhibit mirror-image circular dichroism spectra. The reactions of 1 and 2 were also applied for trapping a C70 fullerene to give 2 : 1 adducts of [{Pd4 (meso-dpmppm)2 (L)}2 (C70 )]4+ (L=CH3 CN (21), XylNC (22)). These results provide useful information for creating a platform to develop dimensionally and chirality controlled metal-carbon nanocomposite materials.

Macrocyclic Complexes Derived from Four cis-L2 Pt Corners and Four Butadiynediyl Linkers; Syntheses, Electronic Structures, and Square versus Skew Rhombus Geometries.

The dialkyl malonate derived 1,3-diphosphines R2 C(CH2 PPh2 )2 (R=a, Me; b, Et; c, n-Bu; d, n-Dec; e, Bn; f, p-tolCH2 ) are combined with (p-tol3 P)2 PtCl2 or trans-(p-tol3 P)2 Pt((C≡C)2 H)2 to give the chelates cis-(R2 C(CH2 PPh2 )2 )PtCl2 (2 a-f, 94-69 %) or cis-(R2 C(CH2 PPh2 )2 )Pt((C≡C)2 H)2 (3 a-f, 97-54 %). Complexes 3 a-d are also available from 2 a-d and excess 1,3-butadiyne in the presence of CuI (cat.) and excess HNEt2 (87-65 %). Under similar conditions, 2 and 3 react to give the title compounds [(R2 C(CH2 PPh2 )2 )[Pt(C≡C)2 ]4 (4 a-f; 89-14 % (64 % avg)), from which ammonium salts such as the co-product [H2 NEt2 ]+ Cl- are challenging to remove. Crystal structures of 4 a,b show skew rhombus as opposed to square Pt4 geometries. The NMR and IR properties of 4 a-f are similar to those of mono- or diplatinum model compounds. However, cyclic voltammetry gives only irreversible oxidations. As compared to mono-platinum or Pt(C≡C)2 Pt species, the UV-visible spectra show much more intense and red-shifted bands. Time dependent DFT calculations define the transitions and principal orbitals involved. Electrostatic potential surface maps reveal strongly negative Pt4 C16 cores that likely facilitate ammonium cation binding. Analogous electronic properties of Pt3 C12 and Pt5 C20 homologs and selected equilibria are explored computationally.

Yldiide Ligands as Building Blocks for Polynuclear Coinage Metal Complexes: Metal Squares, Triangles and Chains.

Yldiides have unique electronic properties and donor abilities, but as ligands in transition metal complexes they are scarcely represented in the literature. Here, the controlled synthesis of a series of polynuclear gold yldiide complexes derived from triphenyl(cyanomethyl)phosphonium bromide, [Ph3 PCH2 CN]Br, under mild conditions is described. Anionic dinuclear NBu4 [(AuX)2 {C(CN)PPh3 }] (X=Cl, C6 F5 ) or trinuclear derivatives NBu4 [Au3 X2 {C(CN)PPh3 }] bearing terminal chloride or pentafluorophenyl groups and bridging yldiide ligands have been prepared. These compounds evolve in solution giving rise to the formation of an unprecedented tetrameric gold cluster, [Au4 {C(CN)PPh3 }4 ], by the loss of the gold complex NBu4 [AuX2 ]. This gold cluster can also be prepared in high yield by a transmetalation reaction from the analogous tetrameric silver cluster, and two geometric isomers have been characterised, their formation dependent on the synthetic route. The triphenylphosphonium cyanomethyldiide ligand has also been used to build different dinuclear and trinuclear cationic complexes bearing phosphine or diphosphine ancillary ligands and bridging yldiide moieties. Further coordination through the cyano group of the yldiide ligand gives heterometallic trinuclear or pentanuclear derivatives. Structural characterisation of many of these compounds reveals the presence of complex molecular systems stabilised by gold⋅⋅⋅gold interactions and bridging yldiide ligands.

Synthesis and crystallographic characterisation of a homologous series of bis-tridentate phosphine oxide NP3O3 Fe(II), Co(II), Ni(II) and Cu(II) complexes

Despite the large numbers of mono- and bidentate phosphine oxide complexes, examples of well characterised discrete multidentate phosphine oxide transition metal complexes are relatively rare. Herein, we report the coordination chemistry of the triphosphine oxide ligand N{CH2P(O)Ph2}3 (NP3O3, 1) with a series of first row transition metals. Ligand 1 was found to form a series of bis-tridentate homoleptic complexes with Fe(II), Co(II), Ni(II) and Cu(II) salts of the type M(BF4)2·6H2O. The anion exchange reaction of BF4— for BPh4— aided in the crystallisation of three of the four complexes. X-Ray crystallographic analysis of this series: [Fe(N{CH2P(O)Ph2}3)2](BPh4)2 (2), [Co(N{CH2P(O)Ph2}3)2](BPh4)2 (3), [Ni(N{CH2P(O)Ph2}3)2](BPh4)2 (4) and [Cu(N{CH2P(O)Ph2}3)2](BF4)2 (5) confirmed either almost idealised octahedral or distorted octahedral structures and tridentate coordination of 1. Complex 5, Cu(II) d9, displayed a classic Jahn-Teller distortion showing a prominent elongation of the axial M–O bonds. All complexes were found to be paramagnetic which precluded NMR spectroscopy analysis. Magnetic susceptibility measurements on solid samples of the complexes confirmed their number of unpaired electrons and high spin states.

C, C coordination mode in comparison with C, P coordination mode in six and seven pallada- and platinacycle complexes of phosphorous ylide; synthesis, X-ray and theoretical studies

New symmetrical [p-CN-C6H4C(O)CH2PPh2(CH2)2PPh2CH2C(O)C6H4-p-CN]Br2(1) and unsymmetrical [PPh2(CH2)2PPh2CH2C(O)C6H4-p-CN]Br (2) phosphonium salts were prepared by reacting Bis(diphenylphosphino)ethane (dppe) with p-CN-C6H4C(O)CH2Br in acetone, in 1:2 and 1:1 ratios, respectively. Treatment of these salts with an appropriate alkali led to symmetrical p-CN-C6H4C(O)C(H)PPh2(CH2)2PPh2C(H)C(O)C6H4-p-CN (3) and unsymmetrical PPh2(CH2)2PPh2C(H)C(O)C6H4-p-CN (4) ylides.The reaction of 3 and 4 with [MCl2(cod)] (M = Pd or Pt; cod = 1,5-cyclooctadiene) in 1:1 ratio, using dichloromethane as a solvent, led to mononuclear seven membered metallocyclic ring complexes ([MCl2(p-CN-C6H4C(O)C(H)PPh2(CH2)2PPh2C(H)C(O)C6H4-p-CN)] (M = Pd (5) and Pt (6), having C,C coordination mode) and mononuclear six membered ring complexes [MCl2(PPh2(CH2)2PPh2C(H)C(O)C6H4-p-CN)] (M = Pd (7) and Pt (8), having P,C coordination mode), respectively. Characterization of the resulting compounds were performed by elemental analysis, IR, 1H,13C and 31P NMR spectroscopic methods. As well, the unequivocal structure of compound 5 (seven membered pallada-cycle complex) was characterized crystallographically. In the symmetrical complexes, with seven membered metallocyclic rings, the title ylide is coordinated to the metal through two ylidic carbon atoms. Using theoretical methods, Density-function theory (DFT) calculations at the BP86/def2-SVP level of theory, the structures of the unsymmetrical six membered pallada- and platinacyclic complexes were compared with the structures of the symmetrical seven membered pallada- and platinacyclic complexes. The strength and nature of donor−acceptor bonds between the phosphorus ylide (Y ligand) and MCl2 fragments in the [YMCl2] (M = Pd, Pt, Y = p-CN-C6H4C(O)C(H)PPh2(CH2)2PPh2C(H)C(O)C6H4-p-CN,PPh2(CH2)nPPh2C(H)C(O)C6H4-p-CN, n = 1–2, were carried out by Natural bond orbital analysis (NBO) and energy-decomposition analysis (EDA) as well as their natural orbitals for chemical valence (NOCV) variations.

Luminescence properties of the antifungal agent ketoconazole and its diphenylphosphane derivatives

In this paper we present a physico-chemical characterization of ketoconazole (Ke) and four derivatives: diphenylphosphane (KeP), where acetyl group is replaced with –CH2PPh2 moiety and the phosphane chalcogenides: oxide (KeOP), sulphide (KeSP) and selenide (KeSeP). The antifungal activity of these compounds was recently studied, showing that they are promising antifungal agents towards Saccharomyces cerevisiae and Candida albicans. All the compounds share the same mode of action, which is to inhibit the cytochrome P450 14α-demethylase. However, differences in antifungal activity suggest that there may be additional modes of action or important interactions with other cellular components. The further understanding of the action mechanisms of these compounds will demand a detailed study of their interactions with different potential molecular partners, and understand their behavior in different molecular environments. Therefore, in this study we characterized thoroughly the luminescence characteristics of Ke, as well as of its diphenylphosphano derivatives using fluorescence spectroscopy techniques and DFT calculations. It has been shown that their main absorption and luminescence bands, which result from a mixture of π→π* and n→π* transitions located at the −1,3-dioxolan-4-yl–C6H4–piperazine aromatic ring, overlap the transitions at the –CH2P(X)Ph2 moiety which thereby acts as a intramolecular fluorescence quencher.

Rhodium Complexes in P−H Bond Activation Reactions

The feasibility of oxidative addition of the P-H bond of PHPh2 to a series of rhodium complexes to give mononuclear hydrido-phosphanido complexes has been analyzed. Three main scenarios have been found depending on the nature of the L ligand added to [Rh(Tp)(C2 H4 )(PHPh2 )] (Tp= hydridotris(pyrazolyl)borate): i) clean and quantitative reactions to terminal hydrido-phosphanido complexes [RhTp(H)(PPh2 )(L)] (L=PMe3 , PMe2 Ph and PHPh2 ), ii) equilibria between RhI and RhIII species: [RhTp(H)(PPh2 )(L)]⇄[RhTp(PHPh2 )(L)] (L=PMePh2 , PPh3 ) and iii) a simple ethylene replacement to give the rhodium(I) complexes [Rh(κ2 -Tp)(L)(PHPh2 )] (L=NHCs-type ligands). The position of the P-H oxidative addition-reductive elimination equilibrium is mainly determined by sterics influencing the entropy contribution of the reaction. When ethylene was used as a ligand, the unique rhodaphosphacyclobutane complex [Rh(Tp)(η1 -Et)(κC,P -CH2 CH2 PPh2 )] was obtained. DFT calculations revealed that the reaction proceeds through the rate limiting oxidative addition of the P-H bond, followed by a low-barrier sequence of reaction steps involving ethylene insertion into the Rh-H and Rh-P bonds. In addition, oxidative addition of the P-H bond in OPHPh2 to [Rh(Tp)(C2 H4 )(PHPh2 )] gave the related hydride complex [RhTp(H)(PHPh2 )(POPh2 )], but ethyl complexes resulted from hydride insertion into the Rh-ethylene bond in the reaction with [Rh(Tp)(C2 H4 )2 ].

Complexes of TaOCl3 and TaSCl3 with neutral N- and O-donor ligands – Synthesis, properties and comparison with the niobium analogues

The white complexes, [TaOCl3(OPPh3)2], [TaOCl3(L-L)] (L-L = 1,10-phenanthroline, 2,2′-bipyridyl, Ph2P(O)CH2P(O)Ph2, Ph2P(O)CH2CH2P(O)Ph2 and o-C6H4(P(O)Ph2)2), have been prepared from TaCl5, O(SiMe3)2 and the ligands in anhydrous CH2Cl2 solution. The corresponding yellow [TaSCl3(OPPh3)2] and [TaSCl3(L-L)] were made similarly using S(SiMe3)2. The complexes have been characterised by microanalysis, IR and NMR (1H, 31P{1H}) spectroscopy. X-ray crystal structures have been obtained for [TaOCl3(1,10-phen)], [TaSCl3(1,10-phen)], [TaOCl3{o-C6H4(P(O)Ph2)2}], [TaSCl3(OPPh3)2], [TaSCl3{Ph2P(O)CH2CH2P(O)Ph2}] and [TaSCl3(MeCN)2], which all contain mer-chlorines and with the neutral ligands trans to O/Cl or S/Cl. The structure of the Ta(V) dimer [Cl2S(1,10-phen)Ta(µ-O)Ta(1,10-phen)SCl2], formed by trace hydrolysis, is also reported. Comparisons between the complexes of TaOCl3 and TaSCl3 and their niobium analogues are discussed.

Synthesis, characterization, theoretical and cytotoxicity studies of Pd(II) and Pt(II) complexes with new bidentate carbon donor ligand

The new phosphonium salt, the C,C-chelating phosphorus ylide ligand, (MeOC6H5C(O)CHPPh2(CH2)2PPh2CHC(O)C6H5OMe), and its Pd(II) and Pt(II) complexes have been synthesized and the cytotoxic activity of the synthesized complexes against three human cancer cell lines, including HeLa (Human cervix cancer cell line), KB (human oral cancer cell line) and U87 MG (human glioblastoma cell line) were evaluated using an MTT assay. The new compounds were identified and characterized using multinuclear (1H, 13C and 31P) NMR, infrared (IR) spectroscopy, elemental analysis, and through UV absorption and fluorescence emission spectra. Also, the crystal structure of the phosphorus ylide ligand was determined by single-crystal X-ray diffraction analysis. According to the obtained results from the MTT assay, the Pd(II) and Pt(II) complexes demonstrated a higher cytotoxic activity against KB human oral cancer cells in comparison with other cell lines, rendering these compounds into suitable candidates for further anti-oral cancer studies. Furthermore, a theoretical study on structure and nature of the MC bonding between the Y ligand (ylide) and MCl2 fragment in the [YMCl2] (M = Pd, Pt and Y = (MeOC6H5C(O)CHPPh2(CH2)2PPh2CHC(O)C6H5OMe)) complexes have been reported via NBO and energy-decomposition analysis (EDA).

Pseudo‐tetrahedral Rhodium and Iridium Complexes: Catalytic Synthesis of E‐Enynes

The reactions of the rhodium(I) and iridium(I) complexes [M(PhBP3 )(C2 H4 )(NCMe)] (PhBP3 =PhB(CH2 PPh2 )3 - ) with alkynes have resulted in the synthesis of a new family of pseudo-tetrahedral complexes, [M(PhBP3 )(RC≡CR')] (M=Rh, Ir), which contain the alkyne as a four-electron donor. The reactions of these unusual compounds with two-electron donors (L=PMe3 , CNtBu) produced a change in the "donicity" of the alkyne from a 4e- to a 2e- donor to give five-coordinate complexes. These were the final products with the iridium complexes, whereas further reactions took place with the rhodium complexes. In particular, C(sp)-H bond activation of the alkyne occurred leading to hydrido alkynyl complexes. This process is essential for the further reactivity of the alkynes, and if the alkyne itself was used as reagent, E-enyne complexes were obtained. As a consequence of this chemistry, we show that the complex [Rh(PhBP3 )(C2 H4 )(NCMe)] is a very efficient pre-catalyst for the regioselective di- and trimerization of terminal alkynes to E-enynes and benzene derivatives, respectively. Interestingly, acetonitrile significantly enhanced the catalytic activity by facilitating the C(sp)-H bond activation step. A hydrometalation mechanism to account for these experimental observations is proposed.

Nitrogen-Based Lewis Acids Derived from Phosphonium Diazo Cations.

Reaction of PPh3 and [(p-ClC6 H4 )N2 ][BF4 ] affords [(p-ClC6 H4 )N(PPh3 )N(PPh3 )][BF4 ] 1, while reaction with (Ph2 PCH2 )2 gave [(p-ClC6 H4 )(NPh2 PCH2 )2 )][BF4 ] 2. These species confirm the Lewis acidity of [(p-ClC6 H4 )N2 (PR3 )][BF4 ] cations at N. In contrast, use of bulky phosphines afford the species [ArN2 (PR3 )][BF4 ] (R=tBu 3, Mes 4). Compound 3 undergoes one electron reduction to give the stable radical [(p-ClC6 H4 )N2 (PtBu3 )]. 5. Combination of 3 and PtBu3 acts as an FLP to effect (SPh)2 cleavage, generating [PhSPtBu3 ]+ and the radical [ArN2 (PR3 )]. . Collectively, these data affirm the ability of the cations [ArN2 (PR3 )]+ to behave as one or two electron acceptors.

Synthesis, characterization and electrocatalytic H2 production of base-containing Fe/S and Fe/Se clusters

Reaction of base-containing diphosphine ligand NPS2 (NP2(Ph2PCH2)2NCH3) with [Fe3(CO)12] in THF at room temperature forms [{Fe2(CO)6(µ-PPh2)}2(µ4-S2)] (1) and [Fe3(CO)8(µ3-S)2{kP-PPh2CH2N(CH3)CH2P(S)Ph2}] (2) resulting from PS bond cleavage and PFe bond formation. Similarly, NPSe2 reacts with Fe3(CO)12 to provide [{Fe2(CO)6(µ-PPh2)}2(µ4-Se2)] (3) and [Fe3(CO)7(µ3-Se)2{k2P,P-(PPh2CH2)2NCH3}] (4). All the compounds have been completely characterized by elemental analyses, IR, 1H NMR, 13C NMR and 31P NMR spectroscopy and structurally determined by X-ray crystallography. Electrochemical studies reveal that when using HOAc or TFA as a proton source, 2 and 4 exhibit catalytic H2 production.

A General, Rhodium‐Catalyzed, Synthesis of Deuterated Boranes and N‐Methyl Polyaminoboranes

The rhodium complex [Rh(Ph2 PCH2 CH2 CH2 PPh2 )(η6 -FC6 H5 )][BArF4 ], 2, catalyzes BH/BD exchange between D2 and the boranes H3 B⋅NMe3 , H3 B⋅SMe2 and HBpin, facilitating the expedient isolation of a variety of deuterated analogues in high isotopic purities, and in particular the isotopologues of N-methylamine-borane: R3 B⋅NMeR2 1-dx (R=H, D; x=0, 2, 3 or 5). It also acts to catalyze the dehydropolymerization of 1-dx to give deuterated polyaminoboranes. Mechanistic studies suggest a metal-based polymerization involving an unusual hybrid coordination insertion chain-growth/step-growth mechanism.