Di‐μ‐pivalamidato‐κ4N:O;O:N‐bis­[(2,2′‐bi­pyridine‐κ2N,N′)(sulfato‐κO)­platinum(III)] tetrahydrate in a head‐to‐tail isomerism

The title compound, [Pt₂^III(C₅H₁₀NO)₂(SO₄)₂(C₁₀H₈N₂)₂]·4H₂O, is the first reported example of a complex in which an amidate‐bridged Pt(bpy) dimer is stabilized in the oxidation level of Pt^III (bpy is 2,2′‐bi­pyridine). The asymmetric unit consists of one half of the formula unit with a twofold axis passing through the center of the dimer. The intradimer Pt^III—Pt^III bond distance [2.5664 (6) Å] is comparable to those reported for α‐pyridonate‐bridged cis‐diammineplatinum(III) dimers [2.5401 (5)–2.5468 (8) Å; Hollis & Lippard (1983). Inorg. Chem. 22 , 2605–2614], in spite of the close contact between the bpy planes within the dimeric unit. The axial Pt—O_sulfate distance is 2.144 (7) Å.     

Luminescent Amphiphilic 2,6‐Bis(1‐alkylpyrazol‐3‐yl)pyridyl Platinum(II) Complexes: Synthesis,Characterization, Electrochemical,Photophysical, and Langmuir–Blodgett Film Formation Studies

Two series of novel platinum(II) 2,6‐bis(1‐alkylpyrazol‐3‐yl)pyridyl (N5Cn) complexes, [Pt(N5Cn)Cl][X] ( 1 – 9 ) and [Pt(N5Cn)(C?CR)][X] ( 10 – 13 ) (X=trifluoromethanesulfonate (OTf) or PF₆; R=C₆H₅, C₆H₄‐p‐CF₃ and C₆H₄‐p‐N(C₆H₅)₂), with various chain lengths of the alkyl groups on the nitrogen atom of the pyrazolyl units have been successfully synthesized and characterized. Their electrochemical and photophysical properties have been studied. Some of their molecular structures have also been determined by X‐ray crystallography. Two amphiphilic platinum(II) 2,6‐bis(1‐tetradecylpyrazol‐3‐yl)pyridyl (N5C14) complexes, [Pt(N5C14)Cl]PF₆ ( 7 ) and [Pt(N5C14)(C?CC₆H₅)]PF₆ ( 13 ), were found to form stable and reproducible Langmuir–Blodgett (LB) films at the air–water interface. The characterization of such LB films has been investigated by the study of their surface pressure–area (π–A) isotherms, UV/Vis spectroscopy, XRD, X‐ray photoelectron spectroscopy (XPS), FTIR, and polarized IR spectroscopy. The luminescence property of 13 in LB films has also been studied.     

trans‐Dichloro(dimethyl sulfide‐κS)(pyridine‐κN)platinum(II)

The structure of the title compound, [PtCl₂(C₅H₅N)(C₂H₆S)], consists of discrete mol­ecules in which the Pt‐atom coordination is slightly distorted square planar. The Cl atoms are trans to each other, with a Cl—Pt—Cl angle of 176.60 (7)°. The pyridine ligand is rotated 64.5 (2)° from the Pt square plane and one of the Pt—Cl bonds essentially bisects the C—S—C angle of the di­methyl sulfide ligand. In the crystal structure, there are extensive weak C—H⋯Cl interactions, the shortest of which connects mol­ecules into centrosymmetric dimers. A comparison of the structural trans influence on Pt—S and Pt—­N distances for PtS(CH₃)₂ and Pt(pyridine) fragments, respectively, in square‐planar Pt^II complexes is presented.     

cis‐[1,2‐Bis(diisopropylphosphino‐κP)‐1,2‐dicarba‐closo‐dodecaborane]dichloroplatinum(II) dichloromethane hemisolvate

The asymmetric unit of the title complex, [PtCl₂(C₁₄H₃₈B₁₀P₂)]·0.5CH₂Cl₂ or cis‐[PtCl₂{1,2‐(PⁱPr₂)₂‐1,2‐C₂B₁₀H₁₀}]·0.5CH₂Cl₂, contains one disordered solvent mol­ecule and two mol­ecules of the complex, in which each Pt^II atom displays slightly distorted square‐planar coordination geometry. The P atoms connected to the cage C atoms are coordinated to the Pt^II atom. The Pt—P distances vary slightly [2.215 (3) and 2.235 (4) Å] and the Pt—Cl distances are equal [2.348 (3) and 2.353 (5) Å].     

An Alkyne‐Appended,Click‐Ready PtII Complex with an Unusual Arrangement in the Solid State

To better understand the range of cellular interactions of Pt^II‐based chemotherapeutics, robust and efficient methods to track and analyze Pt targets are needed. A powerful approach is to functionalize Pt^II compounds with alkyne or azide moieties for post‐treatment conjugation through the azide–alkyne cycloaddition (click) reaction. Herein, we report an alkyne‐appended cis‐diamine Pt^II compound, cis‐[Pt(2‐(5‐hexynyl)amido‐1,3‐propanediamine)Cl₂] ( 1 ), the X‐ray crystal structure of which exhibits a combination of unusual radially distributed CH/π(C?C) interactions, Pt? Pt bonding, and NH:O/NH:Cl hydrogen bonds. In solution, 1 exhibits no Pt? alkyne interactions and binds readily to DNA. Subsequent click reactivity with nonfluorescent dansyl azide results in a 70‐fold fluorescence increase. This result demonstrates the potential for this new class of alkyne‐modified Pt compound for the comprehensive detection and isolation of Pt‐bound biomolecules.     

A one‐dimensional chloride‐bridged PtII/PtIV mixed‐valence complex with a 4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate counter‐ion

The title compound, catena‐poly[[[bis(ethylenediamine‐κ²N,N′)platinum(II)]‐ μ‐chlorido‐[bis(ethylenediamine)platinum(IV)]‐μ‐chlorido] tetrakis{4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate} dihydrate], {[Pt^IIPt^IVCl₂(C₂H₈N₂)₄](HOC₆H₄N=NC₆H₄SO₃)₄·2H₂O}_n, has a linear chain structure composed of square‐planar [Pt(en)₂]²⁺ (en is ethylenediamine) and elongated octahedral trans‐[PtCl₂(en)₂]²⁺ cations stacked alternately, bridged by Cl atoms, along the b axis. The Pt atoms are located on an inversion centre, while the Cl atoms are disordered over two sites and form a zigzag ...Cl—Pt^IV—Cl...Pt^II... chain, with a Pt^IV—Cl bond length of 2.3140 (14) Å, an interatomic Pt^II...Cl distance of 3.5969 (15) Å and a Pt^IV—Cl...Pt^II angle of 170.66 (6)°. The structural parameter indicating the mixed‐valence state of the Pt atom, expressed by δ = (Pt^IV—Cl)/(Pt^II...Cl), is 0.643.     

Syntheses,Spectroscopic, Electrochemical,and Third‐Order Nonlinear Optical Studies of a Hybrid Tris{ruthenium(alkynyl)/(2‐phenylpyridine)}iridium Complex

The synthesis of fac‐[Ir{N,C₁′‐(2,2′‐NC₅H₄C₆H₃‐5′‐C?C‐1‐C₆H₂‐3,5‐Et₂‐4‐C?CC₆H₄‐4‐C?CH)}₃] ( 10 ), which bears pendant ethynyl groups, and its reaction with [RuCl(dppe)₂]PF₆ to afford the heterobimetallic complex fac‐[Ir{N,C₁′‐(2,2′‐NC₅H₄C₆H₃‐5′‐C?C‐1‐C₆H₂‐3,5‐Et₂‐4‐C?CC₆H₄‐4‐C?C‐trans‐[RuCl(dppe)₂])}₃] ( 11 ) is described. Complex 10 is available from the two‐step formation of iodo‐functionalized fac‐tris[2‐(4‐iodophenyl)pyridine]iridium(III) ( 6 ), followed by ligand‐centered palladium‐catalyzed coupling and desilylation reactions. Structural studies of tetrakis[2‐(4‐iodophenyl)pyridine‐N,C₁′](μ‐dichloro)diiridium 5 , 6 , fac‐[Ir{N,C₁′‐(2,2′‐NC₅H₄C₆H₃‐5′‐C?C‐1‐C₆H₂‐3,5‐Et₂‐4‐C?CH)}₃] ( 8 ), and 10 confirm ligand‐centered derivatization of the tris(2‐phenylpyridine)iridium unit. Electrochemical studies reveal two ( 5 ) or one ( 6 – 10 ) Ir‐centered oxidations for which the potential is sensitive to functionalization at the phenylpyridine groups but relatively insensitive to more remote derivatization. Compound 11 undergoes sequential Ru‐centered and Ir‐centered oxidation, with the potential of the latter significantly more positive than that of Ir(N,C′‐NC₅H₄‐2‐C₆H₄‐2)₃. Ligand‐centered π–π* transitions characteristic of the Ir(N,C′‐NC₅H₄‐2‐C₆H₄‐2)₃ unit red‐shift and gain in intensity following the iodo and alkynyl incorporation. Spectroelectrochemical studies of 6 , 7 , 9 , and 11 reveal the appearance in each case of new low‐energy LMCT bands following formal Ir^III/IV oxidation preceded, in the case of 11 , by the appearance of a low‐energy LMCT band associated with the formal Ru^II/III oxidation process. Emission maxima of 6 – 10 reveal a red‐shift upon alkynyl group introduction and arylalkynyl π‐system lengthening; this process is quenched upon incorporation of the ligated ruthenium moiety on proceeding to 11 . Third‐order nonlinear optical studies of 11 were undertaken at the benchmark wavelengths of 800 nm (fs pulses) and 532 nm (ns pulses), the results from the former suggesting a dominant contribution from two‐photon absorption, and results from the latter being consistent with primarily excited‐state absorption.     

Pt2II and Pt2III dimers containing a Pt2(2,2′‐bipyridine)2(μ‐N,N‐dimethyl­guanidinato)2 unit

The syntheses and crystal structures of the title Pt₂^II and Pt₂^III dimers doubly bridged with N,N‐dimethyl­guanidinate ligands, namely bis­(μ‐N,N‐dimethyl­guanidinato)bis­[(2,2′‐bipyridine)platinum(II)](Pt—Pt) bis­(hexa­fluoro­phosphate) acetonitrile disolvate, [Pt₂^II(C₃H₈N₃)₂(C₁₀H₈N₂)₂](PF₆)₂·2CH₃CN, (I), and guanidinium bis­(μ‐N,N‐dimethyl­guanidinato)bis­[(2,2′‐bipyridine)sulfatoplatinum(III)](Pt—Pt) bis­(hexa­fluoro­phosphate) nitrate hexa­hydrate, (C₃H₁₀N₃)[Pt^III₂(C₃H₈N₃)₂(SO₄)₂(C₁₀H₈N₂)₂]NO₃·6H₂O, (II), are reported. The oxidation of the Pt₂^II dimer into the Pt₂^III dimer results in a marked shortening of the Pt—Pt distance from 2.8512 (6) to 2.5656 (4) Å. The change is mainly compensated for by the change in the dihedral angle between the two Pt coordination planes upon oxidation, from 21.9 (2) to 16.9 (3)°. We attribute the relatively strong one‐dimensional stack of dimers achieved in the Pt₂^II compound in part to the strong Pt^II⋯C(bpy) associations (bpy is 2,2′‐bipyridine) in the crystal structure [Pt⋯C = 3.416 (10) and 3.361 (12) Å].     

Isocyanate‐ and Isothiocyanate‐Derived RuIV‐Based Alkylidenes: Synthesis,Structure, and Activity

The synthesis and characterization of a series of isocyanate‐ and isothiocyanate‐derived second generation Grubbs–Hoveyda‐type ruthenium–alkylidene complexes, that is, [Ru(N?C?O)₂(IMesH₂)(?CH‐2‐(2‐PrO)‐C₆H₄)] ( 1 ), [Ru(N?C?O)₂(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)(=CH‐2‐(2‐PrO)‐C₆H₄)] ( 2 ), [Ru(N?C?S)₂(IMesH₂)(?CH‐2‐(2‐PrO)‐C₆H₄)] ( 3 ), and [Ru(N?C?S)₂(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)(?CH‐2‐(2‐PrO)‐C₆H₄)] ( 4 ), and their activity in various metathesis reactions are described. Compounds 1 – 4 were prepared by reaction of the parent complexes [RuCl₂(IMesH₂)(?CH‐2‐(2‐PrO)C₆H₄)] ( 5 ) (IMesH₂=1,3‐bis‐(2,4,6‐trimethylphenyl)‐4,5‐dihydroimidazol‐2‐ylidene) and [RuCl₂(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)(?CH‐2‐(2‐PrO)‐C₆H₄)] ( 6 ) with silver cyanate and thiocyanate, respectively. The X‐ray structure of 1 was determined, confirming the isocyanate‐type bonding of the ligand. The isothiocyanate‐type bonding in 3 and 4 was unambiguously confirmed by IR and ¹³C NMR spectroscopy. The isocyanate‐derived complexes 1 and 2 were found to be excellent catalysts for the ring‐opening metathesis polymerization (ROMP) of cis‐cycloocta‐1,5‐diene (COD). Both 1 and 2 yielded poly(COD) with a trans‐content of about 80 %. First‐order kinetics with unprecedentedly high rate constants of polymerization (k_p=0.068 and 0.26 s^?1, respectively) were observed. Compounds 3 and 4 were also active initiators for the ROMP of COD, however, they generated poly(COD) with a cis‐content of 80 and 67 %, respectively. Complexes 1 and 2 also showed good catalytic activity in cross‐metathesis (CM) reactions. Finally, 1 – 4 were also found to be excellent catalysts for the regioselective cyclopolymerization of diethyl 2,2‐dipropargylmalonate (DEDPM), resulting in poly(DEDPM) almost entirely based on five‐membered repeat units, that is, cyclopent‐1‐ene‐1,2‐vinylenes.     

Cis–trans isomerism in a square‐planar platinum(II) complex bearing bulky fluorinated phosphane ligands

Transition‐metal complexes bearing fluorinated phosphane and thiolate ligands has been an area of study in recent years and the chemical context of the current work is related to the metal‐assisted functionalization of fluorinated derivatives. The cis and trans isomers of the square‐planar complex bis[(pentafluorophenyl)diphenylphosphane‐κP]bis(2,3,5,6‐tetrafluorobenzenethiolato‐κS)platinum(II), [Pt(C₆HF₄S)₂{P(C₆H₅)₂(C₆F₅)}₂], have been crystallized from a single chromatographic fraction and characterized by X‐ray diffraction analysis. The stabilization of the cis isomer results from weak intramolecular π‐stacking interactions and possibly from the formation of a C—F…Pt contact, characterized by an F…Pt separation of 2.957 (6) Å. The natural bond orbital analysis (NBO) for this isomer confirms that the corresponding F → Pt charge transfer accounts for 6.92 kcal mol⁻¹ in the isomer stabilization. Such interactions are not present in the centrosymmetric trans isomer.     

Synthesis and Spectroscopic Characterization of Potassium Polyfluoroalken‐1‐yltrifluoroborates

The potassium fluoroborates K[RCF=CFBF₃] (R = F, Cl (cis‐/trans‐mixture), trans‐C₄F₉, cis‐C₂F₅, cis‐C₆F₁₃, trans‐C₄H₉, trans‐C₆H₅) were prepared by fluoridation (methoxide‐fluoride substitution with K[HF₂]) of RCF=CFB(OMe)₂ and Li[RCF=CFB(OMe)₃] which were obtained from RCF=CFLi and B(OMe)₃. The K[RCF=CFBF₃] salts were characterized by their ¹H, ¹¹B, ¹⁹F NMR and IR spectra.     

Crystallization experiments with the dinuclear chelate ring complex di‐μ‐chlorido‐bis[(η2‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC1)platinum(II)]

Crystallization experiments with the dinuclear chelate ring complex di‐μ‐chlorido‐bis[(η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)platinum(II)], [Pt₂(C₁₅H₁₉O₄)₂Cl₂], containing a derivative of the natural compound eugenol as ligand, have been performed. Using five different sets of crystallization conditions resulted in four different complexes which can be further used as starting compounds for the synthesis of Pt complexes with promising anticancer activities. In the case of vapour diffusion with the binary chloroform–diethyl ether or methylene chloride–diethyl ether systems, no change of the molecular structure was observed. Using evaporation from acetonitrile (at room temperature), dimethylformamide (DMF, at 313 K) or dimethyl sulfoxide (DMSO, at 313 K), however, resulted in the displacement of a chloride ligand by the solvent, giving, respectively, the mononuclear complexes (acetonitrile‐κN)(η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chloridoplatinum(II) monohydrate, [Pt(C₁₅H₁₉O₄)Cl(CH₃CN)]·H₂O, (η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chlorido(dimethylformamide‐κO)platinum(II), [Pt(C₁₅H₁₉O₄)Cl(C₂H₇NO)], and (η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chlorido(dimethyl sulfoxide‐κS)platinum(II), determined as the analogue {η²‐2‐allyl‐4‐methoxy‐5‐[(ethoxycarbonyl)methoxy]phenyl‐κC¹}chlorido(dimethyl sulfoxide‐κS)platinum(II), [Pt(C₁₄H₁₇O₄)Cl(C₂H₆OS)]. The crystal structures confirm that acetonitrile interacts with the Pt^II atom via its N atom, while for DMSO, the S atom is the coordinating atom. For the replacement, the longest of the two Pt—Cl bonds is cleaved, leading to a cis position of the solvent ligand with respect to the allyl group. The crystal packing of the complexes is characterized by dimer formation via C—H…O and C—H…π interactions, but no π–π interactions are observed despite the presence of the aromatic ring.     

Hydrogallierungsreaktionen mit den Monoalkinen H5C6‐C≡C‐SiMe3 und H5C6‐C≡C‐CMe3 – cis/trans‐Isomerie und Substituentenaustausch

Hydrogallation Reactions Involving the Monoalkynes H₅C₆‐C≡C‐SiMe₃ and H₅C₆‐C≡C‐CMe₃ – cis/trans Isomerisation and Substituent Exchange Phenyl‐trimethylsilylethyne, H₅C₆‐C≡C‐SiMe₃, reacted with different dialkylgallium hydrides, R₂Ga‐H (R = Me, Et, nPr, iPr, tBu), by the addition of one Ga‐H bond to its C≡C triple bond (hydrogallation). The gallium atoms attacked selectively those carbon atoms, which were also attached to trimethylsilyl groups. The cis arrangement of Ga and H across the resulting C=C double bonds resulted only for the sterically most shielded di(tert‐butyl)gallium derivative, while in all other cases spontaneous cis/trans rearrangement occurred with the quantitative formation of the trans addition products. The diethyl compound Et₂Ga‐C(SiMe₃)=C(H)‐C₆H₅ ( 2 ) gave by substituent exchange the secondary products EtGa[C(SiMe₃)=C(H)‐C₆H₅]₂ ( 7 , Z,Z) and Ga[C(SiMe₃)=C(H)‐C₆H₅]₃ ( 8 ). Interestingly, compound 8 has two alkenyl groups with a Z configuration, while the third C=C double bond has the cis arrangement of Ga and H (E configuration). The reversibility of the cis/trans isomerisation of hydrogallation products was observed for the first time. tert‐Butyl‐phenylethyne gave the simple addition product, R₂Ga(C₆H₅)=C(H)‐CMe₃ ( 9 ), only with di(n‐propyl)gallium hydride.     

cis‐Bis(acetato‐κO)bis(dimethyl sulfide‐κS)platinum(II)

The title compound, cis‐[Pt(CH₃COO)₂(C₂H₆S)₂], crystallizes in the P2₁/c space group with a pseudo‐square‐planar coordination geometry. The complex forms centrosymmetric dimeric packing units, with C—H...O—Pt interactions and a short Pt...Pt distance [3.5868 (2) Å]. The coordination mode of the acetate ligands is monodentate and they are oriented almost perpendicular to the coordination plane. Cambridge Structural Database [Allen (2002). Acta Cryst. B 58 , 380–388] data show a preferred staggered conformation with respect to the coordination plane for Me₂S in complexes with Pt^II.     

On the reactivity of platina‐β‐diketones: a straightforward synthesis of trans‐acetylchlorobis(phosphine)platinum(II) complexes and their reactivity

The platina‐β‐diketone [Pt₂{(COMe)₂H}₂(µ‐Cl)₂] ( 1 ) was found to react with monodentate phosphines to yield acetyl(chloro)platinum(II) complexes trans‐[Pt(COMe)Cl(PR₃)₂] (PR₃ = PPh₃, 2a ; P(4‐FC₆H₄)₃, 2b ; PMePh₂, 2c ; PMe₂Ph, 2d ; P(n‐Bu)₃, 2e ; P(o‐tol)₃, 2f ; P(m‐tol)₃, 2g ; P(p‐tol)₃, 2h ). In the reaction with P(o‐tol)₃ the methyl(carbonyl)platinum(II) complex [Pt(Me)Cl(CO){P(o‐tol)₃}] ( 3a ) was found to be an intermediate. On the other hand, treating 1 with P(C₆F₅)₃ led to the formation of [Pt(Me)Cl(CO){P(C₆F₅)₃}] ( 3b ), even in excess of the phosphine. Phosphine ligands with a lower donor capability in complexes 2 and the arsine ligand in trans‐[Pt(COMe)Cl(AsPh₃)₂] ( 2i ) proved to be subject to substitution by stronger donating phosphine ligands, thus forming complexes trans‐[Pt(COMe)Cl(L)L′] (L/L′ = AsPh₃/PPh₃, 4a ; PPh₃/P(n‐Bu)₃, 4b ) and cis‐[Pt(COMe)Cl(dppe)] ( 4c ). Furthermore, in boiling benzene, complexes 2a – 2c and 2i underwent decarbonylation yielding quantitatively methyl(chloro)platinum(II) complexes trans‐[Pt(Me)Cl(L)₂] (L = PPh₃, 5a ; P(4‐FC₆H₄)₃, 5b ; PMePh₂, 5c ; AsPh₃, 5d ). The identities of all complexes were confirmed by ¹H, ¹³C and ³¹P NMR spectroscopy. Single‐crystal X‐ray diffraction analyses of 2a ·2CHCl₃, 2f and 5b showed that the platinum atom is square‐planar coordinated by two phosphine ligands (PPh₃, 2a ; P(o‐tol)₃, 2f ; P(4F‐C₆H₄)₃, 5b ) in mutual trans position as well as by an acetyl ligand ( 2a, 2f ) and a methyl ligand ( 5b ), respectively, trans to a chloro ligand. Single‐crystal X‐ray diffraction analysis of 3b exhibited a square‐planar platinum complex with the two π‐acceptor ligands CO and P(C₆F₅)₃ in mutual cis position (configuration index: SP‐4‐3). Copyright © 2005 John Wiley & Sons, Ltd.     

cis‐Bis(3,6‐di­hydro‐2H‐1,2‐oxazine‐N)­di­iodo­platinum(II) and cis‐bis(3,4,5,6‐tetra­hydro‐2H‐1,2‐oxazine‐N)­di­iodo­platinum(II)

The title complexes, [Pt(C₄H₇NO)₂I₂], (I), and [Pt(C₄H₉NO)₂I₂], (II), possess similar square‐planar coordination geometries with modest distortions from ideality. For (I), the cis‐L—Pt—L angles are in the range 87.0 (4)–94.2 (3)°, while the trans angles are 174.4 (3) and 176.4 (3)°. For (II), cis‐L—Pt—L are 86.1 (8)–94.2 (6)° and trans‐L—Pt—L are 174.4 (6) and 177.4 (5)°. One 3,6‐di­hydro‐2H‐1,2‐oxazine ligand in (I) is rotated so that the N—O bond is out of the square plane by approximately 70°, while the N—C bond is only ca 20° out of the plane. The other oxazine ligand is rotated so that the N—C bond is about 80° out of the plane, while the N—O bond is out of the plane by approximately 24°. In (II), the 3,4,5,6‐tetra­hydro‐2H‐1,2‐oxazine ligands are also positioned with one having the N—O bond further out of the plane and the other having the N—C bond positioned in that fashion. Both ligands, however, are rotated approximately 90° compared with their positions in (I). In both complexes, this results in an unsymmetrical distortion of the I—Pt—N bond angles in which one is expanded and the other contracted. These features are compared to those of reported cis‐di­amine­di­iodo­platinum(II) complexes.     

Ring opening of pyridines: the pseudo‐cis and pseudo‐trans isomers of tetra‐n‐butylammonium 4‐nitro‐5‐oxo‐2‐pentenenitrilate

The reaction of 2‐chloro‐5‐nitropyridine with two equivalents of base produces the title carbanion as an intermediate in a ring‐opening/ring‐closing reaction. The crystal structures of the tetra‐n‐butylammonium salts of the intermediates, C₁₆H₃₆N⁺·C₅H₃N₂O₃⁻, revealed that pseudo‐cis and pseudo‐trans isomers are possible. One crystal structure displayed a mixture of the two isomers with approximately 90% pseudo‐cis geometry and confirms the structure predicted by the S_N(ANRORC) mechanism. The pseudo‐cis intermediate undergoes a slow isomerization over a period of months to the pseudo‐trans isomer, which does not have the appropriate geometry for the subsequent ring‐closing reaction. The structure of the pure pseudo‐trans isomer is also reported. In both isomers, the negative charge is highly delocalized, but relatively small differences in C—C bond distances indicate a system of conjugated double bonds with the nitro group bearing the negative charge. The packing of the two unit cells is very similar and largely determined by the interactions between the planar carbanion and the bulky tetrahedral cation.     

trans‐Di­chloro­tetrakis(4‐methylpyrimidine‐N1)­ruthenium(II)

The title compound, trans‐[Ru^IICl₂(N¹‐mepym)₄] (mepym is 4‐methylpyrimidine, C₅H₆N₂), obtained from the reaction of trans,cis,cis‐[Ru^IICl₂(N¹‐mepym)₂(SbPh₃)₂] (Ph is phenyl) with excess mepym in ethanol, has fourfold crystallographic symmetry and has the four pyrimidine bases coordinated through N¹ and arranged in a propeller‐like orientation. The Ru—N and Ru—Cl bond distances are 2.082 (2) and 2.400 (4) Å, respectively. The methyl group, and the N³ and Cl atoms are involved in intermolecular C—H?N and C—­H?Cl hydrogen‐bond interactions.     

A one‐dimensional iodine‐bridged PtII/PtIV mixed‐valence complex,catena‐poly[[[bis­(ethyl­ene­diamine)­platinum(II)]‐μ‐iodo‐[bis­(ethyl­ene­di­amine)platinum(IV)]‐μ‐iodo] hydrogenphosphate dihydrogenphosphate iodide trihydrate]

The title compound, {[Pt^IIPt^IVI₂(C₂H₈N₂)₄](HPO₄)(H₂PO₄)I·3H₂O}_n, has a chain structure composed of square‐planar [Pt(en)₂]²⁺ and elongated octa­hedral trans‐[PtI₂(en)₂]²⁺ cations (en is ethyl­ene­diamine) stacked alternately along the c axis and bridged by the I atoms; a three‐dimensionally valence‐ordered system exists with respect to the Pt sites. The title compound also has a unique cyclic tetra­mer structure composed of two hydrogenphosphate and two dihydrogenphosphate ions connected by strong hydrogen bonds [O⋯O = 2.522 (10), 2.567 (10) and 2.569 (11) Å]. The Pt and I atoms form a zigzag ⋯I—Pt^IV—I⋯Pt^II⋯ chain, with Pt^IV—I bond distances of 2.6997 (7) and 2.6921 (7) Å, inter­atomic Pt^II⋯I distances of 3.3239 (8) and 3.2902 (7) Å, and Pt^IV—I⋯Pt^II angles of 154.52 (3) and 163.64 (3)°. The structural parameters indicating the mixed‐valence state of platinum, expressed by δ = (Pt^IV—I)/(Pt^II—I), are 0.812 and 0.818 for the two independent I atoms.     

Photoinduced Isomerization of Potassium Polyfluoroalk‐1‐enyltrifluoroborates

The UV irradition of K [RCF=CFBF₃] [R = C₄F₉ (trans), C₂F₅ (cis), C₆F₁₃ (cis), Cl (cis/trans 1 : 1)] in acetone led to cis/trans‐isomerization with a final cis/trans composition 7 : 3. In the case of R = C₄H₉ (trans) or C₃F₇O (cis/trans 25 : 75) the photoisomerization was accompanied by a partial decomposition.