PtII Ion Research Articles

Discrete Platinum(II/IV)-Arsenito Clusters with Pt-As and Pt-O Bonding: [PtIV(As3O6)2]2-, [Pt4II(H2AsO3)6(HAsO3)2]2-, and [Pt2IIAs6W4O28]10.

The first two discrete, fully inorganic platinum(II/IV)-arsenito clusters, [fac-PtIV(As3O6)2]2- (PtAs6) and [Pt4II(H2AsO3)6(HAsO3)2]2- (Pt4As8), as well as the platinum(II)-arsenito heteropolytungstate [Pt2IIAs6W4O28]10- (Pt2As6W4), have been synthesized in aqueous media using simple one-pot reaction conditions. In PtAs6, a PtIV ion is coordinated to two cyclic, tridentate As3O6 units via oxo-donation (PtIV-O ∼ 2.02 Å). In Pt4As8, each PtII ion is coordinated to four AsO3 ligands via two oxygens and two AsIII atoms in a square-planar fashion (PtII-AsIII 2.31 Å, PtII-O 2.07 Å), resulting in an open cage-like structure, which forms a strong tetrameric assembly in the solid state mediated by two K+ counterions. In Pt2As6W4, each PtII ion is coordinated by the As atoms of three AsO3 ligands (PtII-AsIII 2.38 Å) and an oxo group (PtII-O 2.07 Å) in addition to bridging two tungsten ions, and this polyanion was characterized in solution by 195Pt NMR.

Photoinduzierte Metallonitrenbildung durch N2 Abspaltung aus Azid‐Diradikal‐Liganden

AbstractÜbergangsmetallnitride/nitrene sind vielversprechende Reagenzien für katalytischen Stickstoffatomtransfer, die in situ durch optisch induzierte N2‐Eliminierung aus Azidkomplexen zugänglich sind. Um ihr synthetisches Potenzial für die Katalyse voll ausschöpfen zu können, ist ein grundlegendes Verständnis der primären photoinduzierten Prozesse und der stereoelektronischen Faktoren, welche die N2‐Dissoziation kontrollieren, unerlässlich. Mit Hilfe von Femtosekunden‐Infrarotspektroskopie klären wir hier die primären molekularen Mechanismen auf, die für die Bildung eines einzigartigen Platin(II)nitrens mit Triplett‐Grundzustand aus einem geschlossenschaligen Platin(II)azidkomplex verantwortlich sind. Die spektroskopischen Daten in Kombination mit quantenchemischen Rechnungen ergeben einen konsistenten Mechanismus: Produktbildung erfordert die anfängliche Besetzung eines angeregten Singulett‐Zustands mit anionischen Azid‐Diradikal‐Liganden, der an ein low‐spin d8‐konfiguriertes PtII‐Ion gebunden ist. Anschließende Interkombination erzeugt das an Platin gebundene Triplett‐Aziddiradikal, welches sich durch N2‐Verlust in einer nahezu barrierelosen, adiabatischen Dissoziation nahtlos in das Triplett‐Nitren umwandelt. Unsere Daten unterstreichen die Bedeutung des produktiven, N2‐freisetzenden Zustands mit Azid ππ* Charakter als Konstruktionsprinzip für den Zugang zu effizienten Stickstoffatomtransfer‐Katalysatoren.

Photoinduced Metallonitrene Formation by N2 Elimination from Azide Diradical Ligands.

Transition-metal nitrides/nitrenes are highly promising reagents for catalytic nitrogen-atom-transfer reactivity. They are typically prepared in situ upon optically induced N2 elimination from azido precursors. A full exploitation of their catalytic potential, however, requires in-depth knowledge of the primary photo-induced processes and the structural/electronic factors mediating the N2 loss with birth of the terminal metal-nitrogen core. Using femtosecond infrared spectroscopy, we elucidate here the primary molecular-level mechanisms responsible for the formation of a unique platinum(II) nitrene with a triplet ground state from a closed-shell platinum(II) azide precursor. The spectroscopic data in combination with quantum-chemical calculations provide compelling evidence that product formation requires the initial occupation of a singlet excited state with an anionic azide diradical ligand that is bound to a low-spin d8 -configured PtII ion. Subsequent intersystem crossing generates the Pt-bound triplet azide diradical, which smoothly evolves into the triplet nitrene via N2 loss in a near barrierless adiabatic dissociation. Our data highlight the importance of the productive, N2 -releasing state possessing azide ππ* character as a design principle for accessing efficient N-atom-transfer catalysts.

Synthesis, crystal structure and DFT calculations of (2′,6′-difluoro-2,3′-bipyridine-κN 2)[2,6-difluoro-3-(pyridin-2-yl)phenyl-κ2 C 1,N 3]methylplatinum(II)

The title compound, [Pt(CH3)(C10H5F2N2)(C10H6F2N2)], displays a distorted cis-PtN2C2 square-planar geometry around the PtII ion consisting of the bidentate C,N chelating anion, a monodentate N-bonded neutral ligand and a methyl group. In the crystal, the molecules are linked by C—H...F, C—H...N and C—H...π interactions. Time-dependent density functional theory (TD-DFT) at the B3LYP level with the 6–311++G(d,p) basis set was applied to optimize the ground-state geometry. The electronic properties, such as excitation energies and the HOMO–LUMO gap energies, were calculated and compared to related structures.

Cis-{1-Butyl-3-[2-(phenyl-sulfan-yl)eth-yl]-4-imidazolin-2-yl-κ2 C 2,S'}di-chlorido-platinum(II).

The asymmetric unit of the title compound, [PtCl2(C15H20N2S)], comprises one PtII ion, one N-heterocyclic carbene(NHC)-thio-ether ligand and two chloride ions. The PtII ion is four-coordinated by one C atom and one S atom of the NHC-thio-ether ligand, and by two chloride ions, forming an approximately square-planar geometry. In the crystal, the mol-ecules are linked via C-H⋯Cl and C-H⋯π inter-actions, forming a layer parallel to the ab plane.

Platinum(II) complex with 4-nitro-N-(pyridin-2-ylmethylidene)aniline: synthesis, characterization, crystal structure and antioxidant activity.

A novel complex has been prepared using the (E)-4-nitro-N-(pyridin-2-ylmethylidene)aniline bidentate Schiff base ligand and PtCl2, namely, dichlorido[(E)-4-nitro-N-(pyridin-2-ylmethylidene)aniline-κ2N,N']platinum(II) acetonitrile hemisolvate, [PtCl2(C12H9N3O2)]·0.5CH3CN, 1. According to the X-ray measurements of the crystal structure, the PtII ion adopts a PtCl2N2 square-planar coordination. The coordination of the Schiff base ligand to the PtII ion occurs in a cyclic bidentate fashion, as a result of which a five-membered metallacycle is formed. Furthermore, in the structure of 1, the neutral molecules form a one-dimensional chain structure through C-H...Cl and C-H...O hydrogen bonds. The characterization of the complex was performed via single-crystal X-ray diffraction, IR spectroscopy and elemental analysis, and the antioxidant activity of the complex was evaluated using spectrophotometry by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method.

(1,2,5,6-η)-Cycloocta-1,5-diene]bis(thiocyanato-κS)platinum(II)

In the title complex, [Pt(SCN)2(C8H12)], the PtII ion lies in a square-planar coordination geometry defined by the mid-points of the two π-coordinated double bonds of cycloocta-1,5-diene and two S-bound SCN− anions. The complex is disposed about a mirror plane passing through the Pt atom and the SCN− ligands, and bisecting the cycloocta-1,5-diene molecule. The room-temperature crystal structure of the title complex was previously reported in the orthorhombic space group Pna21 [Musitu & Garcia-Blanco (1984). Acta Cryst. A40, C101]. The low-temperature structure presented herein represents a different (higher symmetry) orthorhombic space group Pnma whereby the PtII atom lies on a mirror plane, lacking in the earlier study.

N-Acyclic carbene complexes supported by meso-Ph2PCH2P(Ph)CH2P(Ph)CH2PPh2 (meso-dpmppm) as an asymmetric pincer ligand

Reaction of [PtCl2(cod)] with a tetraphosphine meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (meso-dpmppm), afforded mononuclear PtII complexes, [PtCl(meso-dpmppm−κ3)]X (X = Cl (1a), PF6 (1b)); the meso-dpmppm ligand coordinates to the PtII ion tightly with two outer and one inner phosphorus atoms to form fused six- and four-membered chelate rings which is regarded as an asymmetric PPP pincer ligand bearing an uncoordinate inner phosphine unit. Complex 1 readily reacted with RNC in the presence of NH4PF6 to afford [Pt(meso-dpmppm−κ3)(RNC)](PF6)2 (R = Xyl (2a), Cy (2b), tBu (2c)). When 2a and 2b were reacted with excess of benzylamine (BnNH2), N-acyclic carbene complexes, [Pt(meso-dpmppm−κ3){C(NHR)(NHBn)}](PF6)2 (R = Xyl (3a), Cy (3c)), were obtained, and a similar treatment of 2a with n-octylamine (C8H17NH2) afforded [Pt(meso-dpmppm−κ3)- {C(NHXyl)(NHC8H17)}](PF6)2 (3b). In contrast, complex 2c was transformed into a cyanide complex, [Pt(CN)(meso-dpmppm−κ3)]PF6 (4), through NC(tBu) bond cleavage when heated at 80 °C with BnNH2 or PhNH2. Complexes 1–4 were characterized by 1H and 31P NMR and ESI-MS spectroscopies and X-ray diffraction analyses. The uncoordinate inner phosphine of 1b is readily reacted with [Cp*MCl2]2 to give heterodimetallic complexes, [PtCl(η5-Cp*MCl2)(μ−meso-dpmppm−κ3,κ1)]PF6 (M = Ir (5a), Rh (5b); Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl). Complex 2a also reacted with [Cp*IrCl2]2 to yield [Pt(η5-Cp*IrCl2)(μ−meso-dpmppm−κ3,κ1)(XylNC)]PF6 (6a) together with 5a, and however, 6a would not react with BnNH2, just releasing XylNC to result in 5a. Attachment of the metal fragment of {Cp*IrCl2} to the uncoordinated phosphine caused a crucial conformational change of the six-membered chelate ring from a stable chair conformation to a twist-boat structure, which concomitantly reduced reactivity of the isocyanide ligand toward nucleophilic attack of the amine by steric hindrance of meso-dpmppm pincer ligand. These results could be recognized as on/off switching of the asymmetric {PtII(meso-dpmppm−κ3)} pincer complex.

Metal-centred azaphosphatriptycene gear with a photo- and thermally driven mechanical switching function based on coordination isomerism

Metal ions can serve as a centre of molecular motions due to their coordination geometry, reversible bonding nature and external stimuli responsiveness. Such essential features of metal ions have been utilized for metal-mediated molecular machines with the ability to motion switch via metallation/demetallation or coordination number variation at the metal centre; however, motion switching based on the change in coordination geometry remain largely unexplored. Herein, we report a PtII-centred molecular gear that demonstrates control of rotor engagement and disengagement based on photo- and thermally driven cis–trans isomerization at the PtII centre. This molecular rotary motion transmitter has been constructed from two coordinating azaphosphatriptycene rotators and one PtII ion as a stator. Isomerization between an engaged cis-form and a disengaged trans-form is reversibly driven by ultraviolet irradiation and heating. Such a photo- and thermally triggered motional interconversion between engaged/disengaged states on a metal ion would provide a selector switch for more complex interlocking systems.

Complexes of rhodium and platinum with 4,6-dinitro-5,7-dihydroxybenzo[1,2-c][1,2,5]oxadiazole 1-oxide

Complexes being not described earlier and being obtained by the interaction of RhCl3·nH2O and PtCl4 with disodium complex of 4,6-dinitro-5,7-dihydroxybenzo[1,2-c][1,2,5]oxadiazole 1-oxide (Na2DODNBF) of the following composition: [Rh4III(C6N4O8)4Cl16]2·Rh26IIICl9·3H2O and [PtII(HC6N4O8)Cl·H2O]·10H2O have been synthesized and characterized by TG/DSC, ES (UV–vis), IR, 13C NMR, MS (MALDI TOF) methods and quantum-chemical modeling. It has been established that the rhodium (III) compound is a complicated polynuclear-polyligand complex; the Pt(II) compound represents a mononuclear-monoligand complex, in which the selected ligand acts as a bidentate. Changes in oxidation state of RhIII ion during complexing has not been observed, while for platinum the reduction of PtIV into PtII and coordination of ligand to PtII ion has been revealed.

Ligand Perturbations on Fluorescence of Dinuclear Platinum Complexes of 5,12-Diethynyltetracene: A Spectroscopic and Computational Study

To understand how the PtII ion perturbs the electronic structures of tetracene, 10 dinuclear [X(Et3P)2PtII]2-5,12-diethynyltetracene complexes with different auxiliary ligands were synthesized. Interactions between the PtII ion and 5,12-diethynyltetracene were probed spectroscopically and computationally. The dinuclear [X(Et3P)2PtII]2-5,12-diethynyltetracene complexes exhibit red-shifted absorption and fluorescence in comparison with those of 5,12-bis(triisopropylsilylethynyl)tetracene, with the neutral complexes with π-donating auxiliary ligands showing a larger red shift than the cationic complexes with π-accepting ligands. Electronic structures of the complexes and effects of the metal ions and the ligands on the electronic transitions of the complexes were investigated by TD-DFT calculations, the results of which showed that the electronic structure of the 5,12-diethynyltetracene core is perturbed by π interactions with the Pt fragments, the extent of which depends on the energies of the dπ orbitals of the Pt fragments.

Trans-Dichloridobis[tris(4-methoxylphenyl)phosphane-κP]platinum(II) acetone disolvate

In the title compound, [PtCl2(C21H21O3P)2]·2C3H6O, the asymmetric unit contains a PtII ion situated on an inversion center, one chloride anion, one tris­(4-meth­oxy­lphen­yl)phosphane (L) ligand and one acetone solvent mol­ecule. The PtII ion is coordinated by two P atoms [Pt—P = 2.3196 (5) Å] from two L ligands and two chloride anions [Pt—Cl = 2.3075 (5) Å] in a distorted square-planar geometry with P—Pt—Cl angles of 88.016 (16) and 91.984 (16)°. The effective cone angle of the phosphane ligand was calculated to be 156°. Weak C—H⋯O and C—H⋯Cl hydrogen bonds hold mol­ecules together.

(2,3-Di-2-pyridylpyrazine-κ2 N 2,N 3)diiodidoplatinum(II)

The PtII ion in the title complex, [PtI2(C14H10N4)], exists in a distorted square-planar environment defined by the two pyridine N atoms of the chelating 2,3-di-2-pyridyl­pyrazine ligand and two iodide anions. The pyridine rings are inclined to the least-squares plane of the PtI2N2 unit [maximum deviation = 0.070 (3) Å] at 66.1 (2) and 65.9 (2)°; the pyrazine ring is perpendicular to this plane [dihedral angle = 89.7 (2)°]. Two inter­molecular C—H⋯I hydrogen bonds, both involving the same I atom as hydrogen-bond acceptor, generate a layer structure extending parallel to (001). Mol­ecules are stacked in columns along the a axis. Along the b axis, successive mol­ecules stack in opposite directions.

Dichlorido(2,3-di-2-pyridylpyrazine-κ2N1,N2)platinum(II)

The PtII ion in the title complex, [PtCl2(C14H10N4)], is four-coordinated in a distorted square-planar environment by two N atoms of a chelating 2,3-di-2-pyridyl­pyrazine ligand and two chloride anions. The pyridyl ring coordinated to the PtII atom is inclined slightly to its carrier pyrazine ring [dihedral angle = 13.5 (1)°], whereas the uncoordinated pyridyl ring is inclined considerably to the pyrazine ring [dihedral angle = 54.3 (2)°]. The dihedral angle between the two pyridyl rings is 59.2 (2)°. In the crystal, the complexes are assembled through inter­molecular C—H⋯N and C—H⋯Cl hydrogen bonds, forming a three-dimensional network. Intra­molecular C—H⋯N and C—H⋯Cl hydrogen bonds are also present.

Dibromido(2,3-di-2-pyridylpyrazine-κ2N2,N3)platinum(II)

The PtII ion in the title complex, [PtBr2(C14H10N4)], has a slightly distorted square-planar environment defined by the two pyridyl N atoms of the chelating 2,3-di-2-pyridyl­pyrazine ligand and two bromide anions. In the crystal, the pyridyl rings are considerably inclined to the least-squares plane of the PtBr2N2 unit [maximum deviation = 0.064 (2) Å] with dihedral angles of 65.2 (2) and 66.0 (2)°. The nearly planar pyrazine ring [maximum deviation = 0.020 (5) Å] is almost perpendicular to the unit plane with a dihedral angle of 89.2 (2)°. Two independent weak inter­molecular C—H⋯Br hydrogen bonds, both involving the same Br atom as a hydrogen-bond acceptor, give rise to chains running along the a and b axes, forming a layer structure extending parallel to (001). The complexes are stacked in columns along the a axis. When viewed down the b axis, the successive complexes stack in the opposite direction.

Trans-Bis(3-hydroxypyridine-κN)diiodidoplatinum(II) dimethyl sulfoxide disolvate

In the title compound, [PtI2(C5H5NO)2]·2(CH3)2SO, the PtII ion lies on an inversion center and is coordinated in a slightly distorted square-planar environment by two trans iodide ligands and two pyridine N atoms. In the crystal, complex mol­ecules and solvent dimethyl sulfoxide mol­ecules are linked by inter­molecular O—H⋯O hydrogen bonds.

N-Benzyl-N-(diphenylphosphanylmethyl)pyridin-2-amine]chloridomethylplatinum(II)

In the mononuclear title complex, [Pt(CH3)Cl(C25H23N2P)], the N-benzyl-N-(diphenyl­phosphanylmeth­yl)pyridin-2-amine functions as a bidentate ligand with the pyridyl N atom and the phosphine P atom chelating the PtII ion, forming a six-membered metallocycle. The PtII atom adopts a square-planar coordination geometry with one methyl group and one chloride ligand bonding to the metal center in a cis relationship. C—H⋯π and C—H⋯Cl inter­actions help to consolidate the packing.

Catena-Poly[[[diaqua(nitrato-κ2O,O′)(2,2′:6′,2′′-terpyridine-κ3N,N′,N′′)ytterbium(III)]-μ-cyanido-κ2N:C-[dicyanidoplatinum(II)]-μ-cyanido-κ2C:N] acetonitrile monosolvate

The title compound, {[PtYb(CN)4(NO3)(C15H11N3)(H2O)2]·CH3CN}n, was isolated from solution as a one-dimensional coordination polymer. The Yb3+ site has ninefold coordination with a distorted tricapped trigonal–prismatic geometry, while the PtII ion is coordinated by four cyanide groups in an almost regular square-planar geometry. cis-Bridging by the tetra­cyanidoplatinate(II) anions links the Yb3+ cations, forming chains. Additionally, each Yb3+ is coordinated by two water mol­ecules, one bidentate nitrate anion, and one tridentate 2,2′:6′,2′′-terpyridine mol­ecule. O—H⋯N hydrogen-bonding inter­actions are found between adjacent chains and help to consolidate the crystal packing. In addition, π–π stacking inter­actions exist between the terpyridine ligand and the two corresponding terpyridine ligands along the adjacent chain (average inter­planar distance = 3.667 Å). Moderate Pt⋯Pt inter­actions [3.5033 (4) Å] are observed in the structure.

Bis(acridine-κN)dibromidoplatinum(II)

In the title complex, [PtBr2(C13H9N)2], the PtII ion is four-coordinated in a slightly distorted square-planar environment by two N atoms from two acridine ligands and two Br atoms. The Pt atom is located on an inversion centre, and thus the asymmetric unit contains one half of the complex and the PtN2Br2 unit is exactly planar. The dihedral angle between the PtN2Br2 unit and acridine ligand is 78.98 (9)°. In the crystal structure, the complex mol­ecules are arranged in two distinct chains along [110] and [10]. In the chains, inter­molecular π–π inter­actions between the pyridyl and benzene rings connect the complex mol­ecules, with a centroid–centroid distance of 3.631 (4) Å.

Bis(acetonitrile-κN)(1,10-phenanthroline-κ2N,N′)platinum(II) bis(perchlorate)

The asymmetric unit of the title compound, [Pt(CH3CN)2(C12H8N2)](ClO4)2, contains one half of a cationic PtII complex and pair of half perchlorate anions, one of which is disordered over two sites in a 0.53 (3):0.47 (3) ratio. The complex and anions are disposed about a crystallographic mirror plane parallel to the ac plane passing through the Pt and Cl atoms. In the complex, the PtII ion lies in a distorted square-planar environment defined by four N atoms of the chelating 1,10-phenanthroline ligand and two distinct acetonitrile mol­ecules. The component ions inter­act by means of inter­molecular C—H⋯O hydrogen bonds.