Heterobimetallic platinum(II)-palladium(II) complexes bridged by fluorobenzenethiolates. Structure and equilibria

Synthesis of the heterobimetallic platinum(II)-palladium(II) complexes with poly fluorinated benzenethiolates as intermetallic bridges, [(dppe)Pd(μ-SR_F)₂Pt(dppe)](SO₃CF₃)₂ with SR_F = p-SC₆F₄(CF₃) (1), SC₆F₅ (2), p-SC₆HF₄ (3) and o-SC₆H₄(CF₃) (4), have been accomplished either by a redistribution reaction in mixtures of the homonuclear bimetallic species, [(dppe)Pd(μ-SR_F)₂Pd(dppe)]²⁺/[(dppe)Pt(μ-SR_F)₂Pt(dppe)]²⁺ or by assembling the monometallic building blocks [(dppe)M(μ-SR_F)₂]/[(dppe)M′(solvent)₂]²⁺, M, M′ = Pd or Pt. Both experimental systems reach an equilibrium state which is independent of the temperature within the probed range, −90 °C to +50 °C. A single crystal of the heterobimetallic compound [(dppe)Pd(μ-SC₆F₅)₂Pt(dppe)](SO₃CF₃)₂(acetone)₂ (2) was isolated and analyzed by X-ray diffraction. Comparison with the corresponding structures exhibited by the homobimetallic analogous, [Pd₂(μ-SC₆F₅)₂(dppe)₂](SO₃CF₃)₂(acetone)₂ (5) and [Pt₂(μ-SC₆F₅)₂(dppe)₂](SO₃CF₃)₂(acetone)₂ (6) shows that all three structures are isostructural in space group . All three compounds exhibit a centrosymmetric planar [M₂(μ-S)₂] ring in which the sulfur substituents are arranged in an anti configuration.     

Lewis acidity of platinum(II)-based Baeyer-Villiger catalysts: An electrochemical approach

The electrochemical behavior of the Pt(II)-based Baeyer-Villiger catalysts of the general formulae [Pt(μ-OH)(P^∩P)]₂(BF₄)₂ (P^∩P = dppe (1a), 2Fdppe (1 b), 4Fdppe (1c), dfppe (1d), dmpe (1e), depe (1f), dippe (1g), dtbpe (1h)) and [Pt(OH₂)₂(P^∩P)](OTf)₂ (P^∩P = dppe (2a), 2Fdppe (2b), 4Fdppe (2c), dfppe (2d)) is reported. They exhibit irreversible reduction processes whose potentials reflect the Lewis acidity of the metal centres, showing (for the aromatic diphosphine complexes) overall relations with the number of fluorine atoms, with J_Pt-P, with the ν(CN) coordination shift of a ligand isocyanide probe and with the catalytic activity. Single-crystal X-ray diffraction analyses were carried out for [Pt(μ-OH)(4Fdppe)]₂(BF₄)₂ (1c) and [Pt(μ-OH) (dippe)]₂(BF₄)₂ (1g).     

Nucleophilic attack at the carbon atom of a dithiocarbene ligand by coordinated carbon disulphide: The molecular structure of [(dppe)IPt(μ-C(S)SC(SMe)2)Pt(dppe)]+I− (dppe=1,2-bis(diphenylphosphino)ethane)

Reaction of the complex [Pt(η²-CS₂)(dppe)] [dppe=1,2-bis(diphenylphosphino)ethane] with excess methyl iodide results in the formation in high yield of the dimeric complex [(dppe)IPt(μ-C(S)SC(SMe)₂)Pt(dppe)]⁺I⁻·C₇H₈·Et₂O, the crystal structure of which has been determined. Crystals of the complex are monoclinic, space group P2₁/c, with Z=4, in a unit cell with lattice parameters a=21.082(4), b=17.304(3), c=21.423(3) Å, and β=116.62(1)°. The structure has been refined to R₁=0.054 (R₂=0.059) for 4512 unique data and 333 variables. The complex consists of two distorted square-planar Pt fragments which are held together by a novel bridging CS₂C(SMe)₂ group. The complex has been independently prepared by the reaction of [Pt(η²-CS₂)(dppe)] with the carbene complex [Pt(I)(dppe){C(SMe)₂}]⁺I⁻, and has been further characterized by elemental analysis, ¹H, ³¹P{¹H} NMR, IR spectroscopy, and conductivity measurements.     

Antisymbiosis. Preferential coordination of anionic oxygen versus neutral sulfur donor atoms of methylsulfanyl- or methylsulfinyl-acetato, 2-benzoato and 2-phenolato to the cis-Pt(PPh3)2 and Pt(dppe) residues

The interaction of an excess of the title ligands L⁻ with the cis-Pt(phos)₂ moieties gives compounds a-bcis-[Pt(L-O)₂(phos)₂] (a, phos = P(Ph)₃; b, phos = 1/2 dppe), in which O- is preferred to S-coordination. Such preference is confirmed by the fact that the same products are obtained by reaction of excess of L⁻ with the previously reported a-d complexes [Pt(L-O,S)(phos)₂]⁺, (c, phos = PPh₃, d, phos = 1/2 dppe), for which chelate ring opening occurs with rupture of Pt-S rather than Pt-O bonds. Compound a can be obtained also by oxidative addition of HL to [Pt(PPh₃)₃]. The Pt-O bonds in compounds a-d are stable towards substitution by Me₂SO, pyridine and tetramethylthiourea. Substitution of L’s occurs with N,N′-diethyldithiocarbamate, which forms a very stable chelate with Pt(II). Thiourea and N,N′-dimethylthiourea also react, because they give rise to cyclometallated products [Pt(phos)₂(NRC(S)NHR)]⁺ (R = H, CH₃), with one ionised thioamido group, as revealed by an X-ray investigation of [Pt(PPh₃)₂(NHC(S)NH₂)]⁺. The preference of O versus S coordination, as well as the stability of the Pt-O bonds, are discussed in terms of antisymbiosis.     

Methimazole complexes of platinum(II): Synthesis, characterization and redox behavior

A variety of platinum(II) complexes of methimazole (2-mercapto-1-methylimidazole; HImS = neutral form and ImS = thiolate form), coordinated in both thione and thiolate forms, have been isolated by reacting methimazole with [PtCl(terpy)]Cl (terpy = 2,2′:6′,2″ terpyridine), [PtCl₂(bipy)] (bipy = bipyridine), [PtCl₂(o-phen)] (o-phen = o-phenanthroline), [PtCl₂(CH₃CN)₂] and [PtCl₂(COD)] (COD = 1,5-cyclooctadiene). These complexes were characterized by electronic absorption, IR and NMR (¹H, ¹³C, ¹⁹⁵Pt) spectroscopies. Molecular structure of [Pt(bipy)(HImS)₂]Cl₂·3H₂O (3a·3H₂O) has been established by single crystal X-ray crystallography. Platinum thiolate complex, [Pt(ImS)₂(HImS)₂] (5), could be obtained by treatment of [Pt(HImS)₄]Cl₂ with sodium methoxide in methanol. The solution of 5 in organic solvents yielded bi- and tri-nuclear platinum complexes. The effect of diimine ligands on oxidation of methimazole moiety in the complexes has been studied by electrochemical oxidation and pulse radiolytic oxidation employing specific one-electron oxidant, radical.     

The platinum complexes with histamine: Pt(II)(Hist)Cl2, Pt(II)(Iodo-Hist)Cl2 and Pt(IV)(Hist)2Cl2

The Pt(II) and Pt(IV) complexes with histamine were calculated by using more than 20 DFT functionals and various basis sets. Based on the comparison between the X-ray and theoretical geometrical parameters of the Pt(II)(Hist)Cl₂ complex the MPW1PW91, OPW91 and SVWN5 functionals combined with the 6-311G^∗∗ basis set for non-metallic and SDD (ECP) basis set for platinum were found to yield the most satisfactory agreement. The structure of the Pt(II) complex with iodohistamine important for pharmacy, so far isolated only in minute amounts, was predicted by using the MPW1PW91 functional. Comparison of the theoretical NMR chemical shifts of the Pt(II)(Hist)Cl₂ complex with those found experimentally have shown that the theoretical ¹H and ¹³C NMR chemical shifts are in plausible agreement with the experimental ones, whereas the theoretical ¹⁹⁵Pt chemical shifts fit the experimental values only when the relativistic approach is applied within the ZORA formalism. We confirmed suitability of the three selected functionals for reproduction of the experimental structure of Pt complexes at fourth oxidation state by using the cis- and ions as models. Finally, with the selected theoretical methods, the structures and stabilities of four Pt(IV)(Hist)₂Cl₂ complex isomers were predicted.     

Hydrogen-halide versus alkyl-halide oxidative addition in dimethyl platinum(II) complexes: Crystal structure of [PtBr2(bpy)]

Dimethyl platinum(II) complexes [PtMe₂(NN)] {NN = bu₂bpy (4,4′-di-tert-butyl-2,2′-bipyridine) (1a), bpy (2,2′-bipyridine) (1b), phen (1,10-phenanthroline) (1c)} reacted with commercial 3-bromo-1-propanol in the presence of 1,3-propylene oxide to afford cis, trans- [PtBrMe₂{(CH₂)₃OH}(NN)] (NN = bu₂bpy (2a), bpy (2b), phen (2c)). On the other hand, [PtMe₂(NN)] (1a)-(1b) reacted with the trace of HBr in commercial 3-bromo-1-propanol to give [PtBr₂(NN)] (NN = bu₂bpy (3a), bpy (3b)). The reaction pathways were monitored by ¹H NMR at various temperatures. Treatment of 1a-1b with a large excess of 3-bromo-1-propanol at −80 °C gave the corresponding methyl(hydrido)platinum(IV) complexes [PtBr(H)Me₂(NN)] (NN = bu₂bpy (4a), bpy (4b)) via the oxidative addition of dimethyl platinum(II) complexes with HBr. The complexes [PtBr(H)Me₂(NN)] decomposed by reductive elimination of methane above −20 °C for bu₂bpy and from −20 to 0 °C for bpy analogue to give methane and platinum(II) complexes [PtBrMe(NN)] (5a)-(5b) and then decomposed at about 0 °C to yield [PtBr₂(NN)] and methane. When the reactions were performed at a molar ratio of Pt:RX/1:10, the corresponding complexes [PtBrMe(NN)] (5a)-(5b) were also obtained. The crystal structure of the complex 3b shows that platinum adopts square planar geometry with a twofold axis through the platinum atom. The Pt…Pt distance (5.164 Å) is considerably larger than the interplanar spacing (3.400 Å) and there is no platinum-platinum interaction.     

Synthesis and characterization of complexes of the type [Pt(amine)4]I2 and trans-[Pt(CH3NH2)2(H3CNC(CH3)2)2]I2 by crystallography and multinuclear magnetic resonance spectroscopy

Complexes of the type [Pt(amine)₄]I₂ were synthesized and characterized mainly by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. The compounds were prepared with different primary amines, but not with bulky amines, due to steric hindrance. In ¹⁹⁵Pt NMR, the signals were observed between −2715 and −2769 ppm in D₂O. The coupling constant ³J(¹⁹⁵Pt-¹H) for the MeNH₂ complex is 42 Hz. In ¹³C NMR, the average values of the coupling constants ²J(¹⁹⁵Pt-¹³C) and ³J(¹⁹⁵Pt-¹³C) are 18 and 30 Hz, respectively. The crystal structure of [Pt(EtNH₂)₄]I₂ was determined by X-ray diffraction methods. The Pt atom is located on an inversion center. The structure is stabilized by H-bonding between the amines and the iodide ions. The compound with n-BuNH₂ was found by crystallographic methods to be [Pt(n-BuNH₂)₄]₂I₃(n-BuNHCOO). The crystal contains two independent [Pt(CH₃NH₂)₄]²⁺ cations, three iodide ions and a carbamate ion formed from the reaction of butylamine with CO₂ from the air. When the compound [Pt(CH₃NH₂)₄]I₂ was dissolved in acetone, crystals identified as trans-[Pt(CH₃NH₂)₂(H₃CNC(CH₃)₂)₂]I₂ were isolated and characterized by crystallographic methods. Two trans bonded MeNH₂ ligands had reacted with acetone to produce the two N-bonded Schiff base Pt(II) compound.     

Synthesis and characterization of cis-[(PPh3)2Pt{9-MeAd(-H),NN}]X (X = NO3, PF6): The first example of a platinum(II) complex containing the N,N-chelated 9-methyladenine anion

Reaction between the binuclear hydroxo complex cis-[(PPh₃)₂Pt(μ-OH)]₂X₂ (X⁻ = NO₃, 1a; , 1b) and the model DNA base 9-methyladenine (9-MeAd) leads to the formation of the mononuclear species cis-[(PPh₃)₂Pt{9-MeAd(-H),N⁶N⁷}]X (X⁻ = NO₃, 2a; PF₆, 2b), in which the nucleobase chelates the Pt(II) ion with the N6 and N7 atoms. The coordination mode of the nucleobase has been determinated through a multinuclear (¹H, ³¹P, ¹³C, ¹⁵N and ¹⁹⁵Pt) NMR analysis and the nuclearity of the complex has been obtained by E.S.I. mass spectrometry. 2 represents the first example of an isolated platinum complex in which the NH₂-deprotonated adenine exhibits this binding mode.     

Synthesis and luminescence properties of [Pt{4′-(Np1)-trpy}(CCPh)]SbF6 and [Pt{4′-(Np1)-trpy}{CC(CH2)2CH3}]SbF6 [4′-(Np1)-trpy = 4′-(1-naphthyl)-2,2′:6′,2″-terpyridine]

The synthesis and characterisation of [Pt{4′-(Np1)-trpy}(CCPh)]SbF₆ (1) and [Pt{4′-(Np1)-trpy}{CC(CH₂)₂CH₃}]SbF₆ (2) [4′-(Np1)-trpy = 4′-(1-naphthyl)-2,2:6′,2′-terpyridine] are described. Complexes 1 and 2 exhibit unimolecular ³MLCT (MLCT = metal-to-ligand charge transfer) emission in acetonitrile and in a low concentration 77 K glass solution in butyronitrile. The high concentration glass emission as well as the emission in the solid state is from a ³MMLCT (MMLCT, metal-metal-to-ligand charge transfer) excited state, reflecting the presence of interactions in these media.     

Synthesis and characterization of copper(I) and silver(I) complexes with heterocyclic bidentate ligands (N, X), X = S, Se

The synthesis and structural characterization of series of copper and silver homoleptic complexes [M(R-pyX)], M = Cu, Ag, X = S, Se; R = H, 3-CF₃, 5-CF₃ (not all combinations), is described. The copper compounds, as well as [Ag(pySe)] and [Ag(3-CF₃-pySe)], were synthesised by electrochemical oxidation of anodic metal in a cell containing an acetonitrile solution of the corresponding proligand. The other homoleptic silver complexes were obtained by direct reaction between AgNO₃ and the salt of the corresponding ligand in methanol. In addition, the reaction of the metal thiolate compounds with bis(diphenylphosphino)ethane (dppe) in acetone allowed the synthesis of heteroleptic compounds [M₂(R-pyX)₂(dppe)₃]. The compounds obtained have been characterized by microanalysis, IR spectroscopy and mass spectrometry and, in cases where the complexes were sufficiently soluble, by ¹H NMR spectroscopy. The proligands (3-CF₃pySe)₂ (1), (5-CF₃-pySe)₂ (2) and (5-CF₃-pySe-DMF) (3) and the complexes [Cu(3-CF₃-pyS)] (4), [Ag(3-CF₃-pyS)] (5) and [Cu₂(5-CF₃-pyS)₂(dppe)₃] (6) were obtained as crystalline products and were studied by X-ray diffraction methods.     

Regioselective addition of bifunctional oximehydroxamic acid by the hydroxamic group to Pt(IV)-coordinated nitriles

The metal-mediated coupling between the nitriles RCN in the platinum(IV) complexes trans-[PtCl₄(RCN)₂] (RMe, Et, CH₂Ph, Ph), cis/trans-[PtCl₄(MeCN)(Me₂SO)] and the newly synthesized bifunctional oximehydroxamic acid, viz. N,2-dihydroxy-5-(1-hydroxyiminoethyl)benzamide, proceeds smoothly in CH₂Cl₂ at 40-45 °C to accomplish the new metallaligands HNC(R)ONHC(O)C₆H₃(2-OH)(5-C(Me)NOH) with pendant oxime functionalities due to the regioselective addition of the reagent via its hydroxamic groups. The obtained iminoligands exist in hydroxamic/hydroximic tautomeric equilibrium in solution. The structures of the isolated compounds are based on elemental analyses (C, H, N), IR, 1D ¹H, ¹³C{¹H}, and 2D NMR correlation experiments, i.e. ¹H,¹³C-COSY, ¹H,¹³C long range COSY, ¹H,¹⁵N-COSY, and ¹H,¹⁵N long range COSY.     

Synthesis and structure of iron (III) and iron (II) complexes in S4P2 environment created by diethyldithiocarbamate and 1,2-bis(diphenylphosphino)ethane chelation: Investigation of the electronic structure of the complexes by Mössbauer and magnetic studies

Iron (II) and iron (III) complexes, [Fe^II(DEDTC)₂(dppe)] · CH₂Cl₂ (1), [Fe^II(ETXANT)₂(dppe)] (2) (DEDTC = diethyldithiocarbamate, ETXANT = ethyl xanthate, dppe = 1,2-bis (diphenylphosphino) ethane), and [Fe^III(DEDTC)₂(dppe)] [Fe^IIICl₄] (3) have been synthesized and characterized. Since 3 contains two magnetic centers, an anion metathesis reaction has been conducted to replace the tetrahedral FeCl₄⁻ by a non-magnetic BPh₄⁻ ion producing [Fe^III(DEDTC)₂(dppe)]BPh₄ (4) for the sake of unequivocal understanding of the magnetic behavior of the cation of 3. With the similar end in view, the well-known FeCl₄⁻ ion, the counter anion of 3, is trapped as PPh₄[Fe^IIICl₄] (5) and its magnetic property from 298 to 2 K has been studied. Besides the spectroscopic (IR, UV-Vis, NMR, EPR, Mass and XPS) characterization of the appropriate compounds, especially 2, others viz. 1, 3 and 4 have been structurally characterized by X-ray crystallography. While Fe^II complexes, 1 and 2, are diamagnetic, the Fe^III systems, namely the cations of 3, and 4 behave as low-spin (S = 1/2) paramagnetic species from 298 to 50 K. Below 50 K 3 shows gradual increase of χ_MT up to 2 K suggesting ferromagnetic behavior while 4 exhibits gradual decrease of magnetic moment from 60 to 2 K, indicating the occurrence of weak antiferromagnetic interaction. These conclusions are supported by the Mössbauer studies of 3 and 4. The Mössbauer pattern of 1 exhibits a doublet site for diamagnetic (2-400 K) Fe^II. The compounds 1, 2 and 4 encompass interesting cyclic voltammetric responses involving Fe^II, Fe^III and Fe^IV.     

Synthesis and characterisation of palladium(II) and platinum(II) compounds containing pyrazole-derived ligands: crystal structure of [PdCl2(HL)] (HL = 3-phenyl-5-(2-pyridyl)pyrazole)

Reaction of the ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL¹), 3,5-bis(2-pyridyl)pyrazole (HL²), 3-methyl-5-(2-pyridyl)pyrazole (HL³) and 3-methyl-5-phenylpyrazole (HL⁴) with [MCl₂(CH₃CN)₂] (M = Pd(II), Pt(II)) or [PdCl₂(cod)] gives complexes with stoichiometry [PdCl₂(HL)₂] (HL = HL¹, HL², HL³), [Pt(L)₂] (L = L¹, L², L³) and [MCl₂(HL⁴)₂] (M = Pd(II), Pt(II)). The new complexes were characterised by elemental analyses, conductivity measurements, infrared and ¹H NMR spectroscopies. The crystal and molecular structure of [PdCl₂(HL¹)] was resolved by X-ray diffraction, and consists of monomeric cis-[PdCl₂(HL¹)] molecules. The palladium centre has a typical square planar geometry, with a slight tetrahedral distortion. The tetra-coordinated metal atom is bonded to one pyridine nitrogen, one pyrazolic nitrogen and two chloro ligands in a cis disposition. The ligand HL¹ is not completely planar.     

Synthesis of new platinum(II) compounds with several bidentate and tridentate nitrogen-donor ligands. Structural analyses by H, C{H} and Pt{H} NMR spectroscopy and X-ray crystal structure

The reaction of the N-alkylaminopyrazole (NN′) ligands 1-[2-(ethylamino)ethyl]-3,5-dimethylpyrazole (deae), 1-[2-(tert-butylamino)ethyl]-3,5-dimethylpyrazole (deat), or (NN′N) ligands bis[(3,5-dimethylpyrazolyl)methyl]ethylamine (bdmae) and bis[(3,5-dimethylpyrazolyl)ethyl]ethylamine (ddae) with [PtCl₂(CH₃CN)₂] affords a series of square-planar Pt(II) complexes with formula [PtCl₂(NN′)] (NN′ = deae (1); deat (2)), [PtCl₂(bdmae)] (3), or [PtCl(ddae)]Cl (4). Treatment of complex 4 in the presence of AgBF₄ in CH₂Cl₂/methanol (3:1) gives [PtCl(ddae)](BF₄) (5). These Pt(II) complexes have been characterised by elemental analyses, conductivity measurements and IR, ¹H, ¹³C{¹H}, and ¹⁹⁵Pt{¹H} NMR spectroscopies. The ¹H NMR spectroscopic studies of the complexes prove the rigid conformation of the ligands when they are complexed. The solid-state structure of complex 1 was determined by single crystal X-ray diffraction methods. The deae ligand is coordinated through the N_pz and N_amino atoms to the metallic centre, which completes its coordination with two chlorine atoms in cis disposition.     

Novel reactivity aspects of cis-bis(1-alkenyl)platinum(II) compounds of the type Pt(CH2(CH2)nCHCH2)2L2 (where L2 = dppp, dppe, dppm and n = 1, 2)

We describe the synthesis, structure and reactivity of novel bis(1-alkenyl)platinum(II) complexes, Pt[CH₂(CH₂)_nCHCH₂]₂L₂ (where L₂ = dppp, dppe, dppm and n = 1, 2). The stability of the title complexes with the different ligands is discussed. The steric, chelating and electronic properties of the ligands have a significant impact on the structure as well as on the reactivity of the complexes. Novel reactions with elemental sulfur and carbon dioxide are described and discussed.     

Heteropolymetallic complexes of 1,1′-bis(diphenylphosphino)ferrocene (dppf). IV. Solvolytic behavior and cytostatic properties towards the KB cell-line of dppf and 1,2-bis(diphenylphosphino)ethane cis-complexes of Pt(II) and Pd(II)

The novel cis-platinum(II) complexes [(dppe)Pt(μ-OH)]₂(BF₄)₂ and [(dppe)Pt(DMF)₂](BF₄)₂ have been prepared and characterized by ³¹P NMR, together with cis-[(dppe)Pt(μ-Cl)]₂(BF₄)₂, both in poorly and strongly coordinating solvents (dppe = 1,2-bis(diphenylphosphino)ethane). All these complexes and their dppf analogs (dppf = 1,1′-bis(diphenylphosphino)ferrocene) as well as (dppf)PtCl₂, (dppe)PtCl₂, (dppf)PdCl₂, [(dppf)Pd(μ-Cl)]₂(BF₄)₂ and [(dppf)Pd(μ-OH)]₂(BF₄)₂ have been tested as antiproliferating agents towards Eagle's KB cell-line. Their activity is compared with that of free diphosphine ligands. For Pt(II) complexes, the ID₅₀ figures are found to be higher than those observed for free dppf and dppe. On the contrary, the activity of the palladium dppf complexes is substantially identical to that of free diphosphine.     

Trichloroamine complexes of platinum: preparation,crystal structure and solution behavior of cytosinium trichlorocytosineplatinate(II)

A complex containing a protonated and N3-platinated cytosine (C), [CH][Cl₃Pt(C)] (1a) has been prepared, converted into its K[Cl₃Pt(C)] (1b) and NH₄[Cl₃]Pt(C)]·H₂O (1c) analogs, and structurally characterized (X-ray, Raman, NMR). Reaction of 1b with L = 1-methylcytosine and with L = Me₂SO gave the neutral mixed-ligand complexes cis-Cl₂Pt(C)L. Excess NH₃ was used to convert the anion of 1b into the cation [(NH₃)₃Pt(C)]²⁺ (3a). The pK_a of the N(1)H proton in 3a is 9.4, as determined by UV spectroscopy. The N(1)H is displaced by Pt(II) electrophiles even at neutral pH to give N3,N1-diplatinated cytosinato complexes, as shown by ¹H NMR (³J coupling or ¹⁹⁵Pt at N(1) with H6, 29 Hz, and ⁴J coupling of ¹⁹⁵Pt at N(3) with H5, 14Hz). The results of the X-ray structure determination of 1a (R = 0.031, R_w = 0.034) are of relevance in that they permit a direct comparison of the effect of a proton as opposed to that of a Pt electrophile on the nucleobase geometry. Moreover, the expected decrease in CO(2) bond length as a consequence of Pt binding is observed.     

Palladium(II) and platinum(II) monoselenocarboxylates: Synthesis, spectroscopy, structure and their use as molecular precursors for metal selenides

Treatment of MCl₂(P^∩P) or MCl₂(PⁿPr₃)₂ with two equivalents of ArCOSeK readily yields cis-[M(SeCOAr)₂(P^∩P)] and trans-[M(SeCOAr)₂(PⁿPr₃)₂], respectively (M = Pd or Pt; Ar = Ph or 4-MeC₆H₄; P^∩P = dppm, dppe, dppp). The reaction of Pd(SeCOAr)₂(dppe) with PdCl₂(dppe) in the presence of NaBPh₄ in methanol gave a tri-nuclear ionic complex, [Pd₃(μ₃-Se)₂(dppe)₃][BPh₄]₂. These complexes were characterized by UV-Vis, IR and NMR spectroscopy. The complex [Pt(SeCOPh)₂(dppp)] has been structurally characterized by X-ray crystallography. The coordination environment around square planar platinum atom is defined by chelating dppp ligand and two unidentate selenocarboxylates bonded through selenium atoms. Pyrolysis of [Pd(SeCOAr)₂(PⁿPr₃)₂] either in tri-n-butylphosphate (TBP) (at 200 °C) or in the solid state (furnace heating at 350 °C) gave Pd₁₇Se₁₅.     

Reactivity studies of highly electrophilic ruthenium complexes

The 16-electron, coordinatively unsaturated, dicationic ruthenium complex [Ru(P(OH)₂(OMe))(dppe)₂][OTf]₂ (1a) brings about the heterolysis of the C-H bond in phenylacetylene to afford the phenylacetylide complex trans-[Ru(CCPh)(P(OH)₂(OMe))(dppe)₂][OTf] (2). The phenylacetylide complex undergoes hydrogenation to give a ruthenium hydride complex trans-[Ru(H)(P(OH)₂(OMe))(dppe)₂][OTf] (3) and phenylacetylene via the addition of H₂ across the Ru-C bond. The 16-electron complex also reacts with HSiCl₃ quite vigorously to yield a chloride complex trans-[Ru(Cl)(P(OH)₂(OMe))(dppe)₂][OTf] (4). On the other hand, the other coordinatively unsaturated ruthenium complex [Ru(P(OH)₃)(dppe)₂][OTf]₂ (1b) reacts with a base N-benzylideneaniline to afford a phosphonate complex [Ru(P(O)(OH)₂)(dppe)₂][OTf] (5) via the abstraction of one of the protons of the P(OH)₃ ligand by the base. The phenylacetylide, chloride, and the phosphonate complexes have been structurally characterized. The phosphonate complex reacts with H₂ to afford the corresponding dihydrogen complex trans-[Ru(η²-H₂)(P(O)(OH)₂)(dppe)₂][OTf] (5-H₂). The intact nature of the H-H bond in this species was established using variable temperature ¹H spin-lattice relaxation time measurements and the observation of a significant J(H,D) coupling in the HD isotopomer trans-[Ru(η²-HD)(P(O)(OH)₂)(dppe)₂][OTf] (5-HD).