Intramolecularly Stabilised Group 10 Metal Stannyl and Stannylene Complexes: Multi‐pathway Synthesis and Observation of Platinum‐to‐Tin Alkyl Transfer

Reaction of [PdClMe(P^N)₂] with SnCl₂ followed by Cl‐abstraction leads to apparent Pd?C bond activation, resulting in methylstannylene species trans‐[PdCl{(P^N)₂SnClMe}][BF₄] (P^N=diaryl phosphino‐N‐heterocycle). In contrast, reaction of Pt analogues with SnCl₂ leads to Pt?Cl bond activation, resulting in methylplatinum species trans‐[PtMe{(P^N)₂SnCl₂}][BF₄]. Over time, they isomerise to methylstannylene species, indicating that both kinetic and thermodynamic products can be isolated for Pt, whereas for Pd only methylstannylene complexes are isolated. Oxidative addition of RSnCl₃ (R=Me, Bu, Ph) to M⁰ precursors (M=Pd or Pt) in the presence of P^N ligands results in diphosphinostannylene pincer complexes trans‐[MCl{(P^N)₂SnCl(R)}][SnCl₄R], which are structurally similar to the products from SnCl₂ insertion. This showed that addition of RSnCl₃ to M⁰ results in formal Sn?Cl bond oxidative addition. A probable pathway of activation of the tin reagents and formation of different products is proposed and the relevancy of the findings for Pd and Pt catalysed processes that use SnCl₂ as a co‐catalyst is discussed.     

Conjugated Polyelectrolyte‐Induced Self‐Assembly of Alkynylplatinum(II) 2,6‐Bis(benzimidazol‐2′‐yl)pyridine Complexes

Water‐soluble cationic alkynylplatinum(II) 2,6‐bis(benzimidazol‐2′‐yl)pyridine (bzimpy) complexes have been demonstrated to undergo supramolecular assembly with anionic polyelectrolytes in aqueous buffer solution. Metal–metal‐to‐ligand charge transfer (MMLCT) absorptions and triplet MMLCT (³MMLCT) emissions have been found in UV/Vis absorption and emission spectra of the electrostatic assembly of the complexes with non‐conjugated polyelectrolytes, driven by Pt???Pt and π–π interactions among the complex molecules. Interestingly, the two‐component ensemble formed by [Pt(bzimpy‐Et){C?CC₆H₄(CH₂NMe₃‐4)}]Cl₂ ( 1 ) with para‐linked conjugated polyelectrolyte (CPE), PPE‐SO₃^?, shows significantly different photophysical properties from that of the ensemble formed by 1 with meta‐linked CPE, mPPE‐Ala. The helical conformation of mPPE‐Ala allows the formation of strong mPPE‐Ala– 1 aggregates with Pt???Pt, electrostatic, and π–π interactions, as revealed by the large Stern–Volmer constant at low concentrations of 1 . Together with the reasonably large Förster radius, large HOMO–LUMO gap and high triplet state energy of mPPE‐Ala to minimize both photo‐induced charge transfer (PCT) and Dexter triplet energy back‐transfer (TEBT) quenching of the emission of 1 , efficient Förster resonance energy transfer (FRET) from mPPE‐Ala to aggregated 1 molecules and strong ³MMLCT emission have been found, while the less strong PPE‐SO₃^?– 1 aggregates and probably more efficient PCT and Dexter TEBT quenching would account for the lack of ³MMLCT emission in the PPE‐SO₃^?– 1 ensemble.     

Experimental and quantum‐chemical studies of 1H, 13C and 15N NMR coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with picolines

¹H, ¹³C and ¹⁵N NMR studies of gold(III), palladium(II) and platinum(II) chloride complexes with picolines, [Au(PIC)Cl₃], trans‐[Pd(PIC)₂Cl₂], trans/cis‐[Pt(PIC)₂Cl₂] and [Pt(PIC)₄]Cl₂, were performed. After complexation, the ¹H and ¹³C signals were shifted to higher frequency, whereas the ¹⁵N ones to lower (by ca 80–110 ppm), with respect to the free ligands. The ¹⁵N shielding phenomenon was enhanced in the series [Au(PIC)Cl₃] < trans‐[Pd(PIC)₂Cl₂] < cis‐[Pt(PIC)₂Cl₂] < trans‐[Pt(PIC)₂Cl₂]; it increased following the Pd(II) → Pt(II) replacement, but decreased upon the trans → cis‐transition. Experimental ¹H, ¹³C and ¹⁵N NMR chemical shifts were compared to those quantum‐chemically calculated by B3LYP/LanL2DZ + 6‐31G**//B3LYP/LanL2DZ + 6‐31G*. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

Platinum‐Containing Polyoxometalates: syn‐ and anti‐[PtII2(α‐PW11O39)2]10− and Formation of the Metal–Metal‐Bonded di‐PtIII Derivatives

The first examples of dimeric, di‐Pt^II‐containing heteropolytungstates are reported. The two isomeric di‐platinum(II)‐containing 22‐tungsto‐2‐phosphates [anti‐Pt^II₂(α‐PW₁₁O₃₉)₂]^10? ( 1 a ) and [syn‐Pt^II₂(α‐PW₁₁O₃₉)₂]^10? ( 2 a ) were synthesized in aqueous pH 3.5 medium using one‐pot procedures. Polyanions 1 a and 2 a contain a core comprising two face‐on PtO₄ units, with a Pt???Pt distance of 2.9–3 Å. Both polyanions were investigated by single‐crystal XRD, IR, TGA, UV/Vis, ³¹P NMR, ESI‐MS, CID‐MS/MS, electrochemistry, and DFT. On the basis of DFT and electrochemistry, we demonstrated that the {Pt₂^II} moiety in 1 a and 2 a can undergo fully reversible two‐electron oxidation to {Pt₂^III}, accompanied by formation of a single Pt?Pt bond. Hence we have discovered the novel subclass of Pt^III‐containing heteropolytungstates.     

Darstellung,Kristallstrukturen, Schwingungsspektren und Normalkoordinatenanalyse von trans‐(n‐Bu4N)2[Pt(ECN)2(ox)2], E = S,Se

Synthesis, Crystal Structure, Vibrational Spectra, and Normal Coordinate Analysis of trans ‐( n ‐Bu₄N)₄[Pt(ECN)₂(ox)₂], E = S, Se By reaction of (n‐Bu₄N)₂[Pt(ox)₂] with (SCN)₂ and (SeCN)₂ in dichloromethane trans‐(n‐Bu₄N)₂[Pt(SCN)₂(ox)₂] ( 1 ) und trans‐(n‐Bu₄N)₂[Pt(SeCN)₂(ox)₂] ( 2 ) are formed. The crystal structures of 1 (triclinic, space group P1, a = 10.219(2), b = 11.329(2), c = 12.010(3) Å, α = 114.108(15), β = 104.797(20), γ = 102.232(20)°, Z = 1) and 2 (triclinic, space group P1, a = 10.288(1), b = 11.332(1), c = 12.048(1) Å, α = 114.391(9), β = 103.071(10), γ = 102.466(12)°, Z = 1) reveal, that the compounds crystallize isotypically with centrosymmetric complex anions. The bond lengths are Pt–S = 2.357, Pt–Se = 2.480 and Pt–O = 2.011 ( 1 ) und 2.006 Å ( 2 ). The oxalato ligands are nearly plane with O–C–C–O torsion angles of 1.7–3.6°. The via S or Se coordinated linear groups are inclined between both oxalato ligands with Pt–E–C angles of 100.4 (E = S) and 97.4° (Se). In the vibrational spectra the PtE stretching vibrations are observed at 299–314 ( 1 ) and 189–200 cm^–1 ( 2 ). The PtO stretching vibrations are coupled with internal vibrations of the oxalato ligands and appear in the range of 400–800 cm^–1. Based on the molecular parameters of the X‐ray determinations the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are f_d(PtS) = 1.75, f_d(PtSe) = 1.35 and f_d(PtO) = 2.77 mdyn/Å. The NMR shifts are δ(¹⁹⁵Pt) = 5435.2 ( 1 ), 5373.7 ( 2 ) and δ(⁷⁷Se) = 353.2 ppm with the coupling constant ¹J(SePt) = 37.4 Hz.     

Darstellung,Kristallstrukturen und Schwingungsspektren von trans‐[Pt(N3)4(ECN)2]2–, E = S,Se

Synthesis, Crystal Structures, and Vibrational Spectra of trans ‐[Pt(N₃)₄(ECN)₂]^2–, E = S, Se By oxidative addition to (n‐Bu₄N)₂[Pt(N₃)₄] with dirhodane in dichloromethane trans‐(n‐Bu₄N)₂[Pt(N₃)₄(SCN)₂] and by ligand exchange of trans(n‐Bu₄N)₂[Pt(N₃)₄I₂] with Pb(SeCN)₂ trans‐(n‐Bu₄N)₂[Pt(N₃)₄(SeCN)₂] are formed. X‐ray structure determinations on single crystals of trans‐(Ph₄P)₂[Pt(N₃)₄(SCN)₂] (triclinic, space group P 1, a = 10.309(3), b = 11.228(2), c = 11.967(2) Å, α = 87.267(13), β = 75.809(16), γ = 65.312(17)°, Z = 1) and trans‐(Ph₄P)₂[Pt(N₃)₄(SeCN)₂] (triclinic, space group P 1, a = 9.1620(10), b = 10.8520(10), c = 12.455(2) Å, α = 90.817(10), β = 102.172(10), γ = 92.994(9)°, Z = 1) reveal, that the compounds crystallize isotypically with octahedral centrosymmetric complex anions. The bond lengths are Pt–S = 2.337, Pt–Se = 2.490 and Pt–N = 2.083 (S), 2.053 Å (Se). The approximate linear Azidoligands with N^α–N^β–N^γ‐angles = 172,1–175,0° are bonded with Pt–N^α–N^β‐angles = 116,7–120,5°. In the vibrational spectra the platinum chalcogen stretching vibrations of trans‐(n‐Bu₄N)₂[Pt(N₃)₄(ECN)₂] are observed at 296 (E = S) and in the range of 186–203 cm^–1 (Se). The platinum azide stretching modes of the complex salts are in the range of 402–425 cm^–1. Based on the molecular parameters of the X‐ray determinations the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are f_d(PtS) = 1.64, f_d(PtSe) = 1.36, f_d(PtN^α) = 2.33 (S), 2.40 (Se) and f_d(N^αN^β, N^βN^γ) = 12.43 (S), 12.40 mdyn/Å (Se).     

Assignment of the E,Z configurational isomers of platinum complexes of N,N‐dialkyl‐N′‐acyl(aroyl)thioureas by means of triple resonance 1H/13C/195Pt PFG correlation NMR spectroscopy

Unsymmetrical, dialkyl‐substituted N,N‐dialkyl‐N^′‐acyl(aroyl)thioureas show E,Z configurational isomerism at room temperature in solution, which is also expressed in the existence of cis‐[Pt(ZZ‐L‐S,O)₂], cis‐[Pt(EZ‐L‐S,O)₂] and cis‐[Pt(EE‐L‐S,O)₂] complexes derived from these ligands. These configurational isomers were assigned by means of a double magnetization transfer ¹H/¹³C/¹⁹⁵Pt correlation NMR experiment, despite the fact that the long‐range ⁵J(¹⁹⁵Pt, ¹H) and ⁴J(¹⁹⁵Pt, ¹³C) scalar couplings are not directly observable in their ¹H and ¹³C spectra at high field. Depending on the ligand structure, the relative amounts of cis‐[Pt(ZZ‐L‐S,O)₂], cis‐[Pt(EZ‐L‐S,O)₂] and cis‐[Pt(EE‐L‐S,O)₂] complexes are in the ranges 40–42% ZZ, 46–47% ZE and 12–13% EE. The cis‐bis[N‐methyl‐N‐(tert‐butyl)‐N^′‐(2,2‐dimethylpropanoyl)thioureato]platinum(II) complex is found to occur exclusively as the ZZ isomer. Copyright © 2003 John Wiley & Sons, Ltd.     

cis‐ and trans‐Dichloro(3,6‐dihydro‐1,2‐oxazine‐N)(dimethyl sulfoxide‐S)‐platinum(II)

Both the cis, (I), and trans, (II), isomers of the title complex, [PtCl₂(C₄H₇NO)(C₂H₆OS)], possess relatively undistorted square‐planar geometries about the Pt atoms. For (I), cisL—Pt—L angles are in the range 88.8 (2)–91.08 (8)°, while trans angles are 178.61 (8) and 179.4 (2)°. For (II), cisL—Pt—L 86.1 (3)–93.7 (1)°, and transL—Pt—L 175.5 (1) and 179.1 (3)°. The di­methyl sulfoxide (dmso) ligand adopts a normal pyramidal geometry in both complexes. In (I), the S=O bond essentially eclipses the adjacent Pt—N bond, while the oxazine ligand in (I) is twisted so as to avoid steric interactions with the adjacent chloride ligand. By contrast, the dmso ligand in (II) is rotated such that the S=O bond is approximately perpendicular to the square plane, while the oxazine ligand is once again twisted out of the plane by a similar amount as in (I). These are the first structural examples of square‐planar platinum(II) complexes containing a 1,2‐oxazine ligand.     

trans‐Di­chloro­bis­(tri­phenyl­phosphine‐P)­platinum(II)

Two different crystals (A and B) were used to structurally characterize trans‐[PtCl₂(PPh₃)₂] and to study random and systematic errors in derived parameters. The compound is isomorphous with trans‐[PdCl₂(PPh₃)₂] and with one of the polymorphs of trans‐[PtMeCl(PPh₃)₂] reported previously. Half‐normal probability plot analyses based on A and B show realistic s.u.'s and negligible systematic errors. R.m.s. calculations give very good agreement between A and B, 0.0088 Å. Important geometrical parameters are Pt—P = 2.3163 (11) Å, Pt—Cl = 2.2997 (11) Å, P—Pt—Cl = 87.88 (4) and 92.12 (4)°. Half‐normal probability plots and r.m.s. calculations were also used to compare the title compound with the palladium analogue, showing small systematic differences between the compounds. The torsion angles around the Pt—P bond were found to be very similar to those reported for isomorphous complexes, as well as to the torsion angles around the Pt—As bond in trans‐[PtCl₂(AsPh₃)₂]. The NMR coupling constants for the title compound are similar to Pt—P coupling constants reported for analogous trans complexes.     

Self‐Assembled Hexanuclear Organometallic Cages: Synthesis,Characterization, and Host–Guest Properties

A series of iridium‐ and rhodium‐based hexanuclear organometallic cages containing 2,5‐dichloro‐3,6‐dihydroxy‐1,4‐benzoquinone, 9,10‐dihydroxy‐1,4‐anthraquinone, and 6,11‐dihydroxynaphthacene‐5,12‐dione ligands were synthesized from the self‐assembly of the corresponding molecular “clips” and 2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine ligands in good yields. These organometallic cages can form inclusion systems with a wide variety of π‐donor substrates, including coronene, pyrene, [Pt(acac)₂], and hexamethoxytriphenylene. The 1:1 complexation of the resulting supramolecular assemblies was confirmed by ¹H NMR spectroscopy. Large complexation shifts (Δδ>1 ppm) were observed in the ¹H NMR spectra of guests in the presence of cage [Cp*₆M₆(μ‐DHNA)₃(tpt)₂](OTf)₆ ( 6a ; M=Ir, tpt=2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine). The formation of discrete 1:1 donor–acceptor complexes, pyrene ?6 b (M=Rh), coronene ?6 a , coronene ?6 b , and [Pt(acac)₂] ?6 a was confirmed by their single‐crystal X‐ray analyses. In these systems, the most important driving force for the formation of guest–host complexes is clearly the donor–acceptor π???π stacking interaction, including charge‐transfer interactions between the electron‐donating and electron‐accepting aromatic components. These structures provide compelling evidence for the existence of strong attractive forces between the electron‐deficient triazine core and electron‐rich guest. The results presented here may provide useful guidance for designing artificial receptors for functional biomolecules.     

Amidophosphine‐stabilized palladium complexes catalyse Suzuki–Miyaura cross‐couplings in aqueous media

We report a simple and efficient procedure for Suzuki–Miyaura reactions in aqueous media catalysed by amidophosphine‐stabilized palladium complexes trans‐{L³PPh₂}₂PdCl₂ ( 3 ), trans‐{L³PPhtBu}₂PdCl₂ ( 4 ), [Pd(η³‐C₃H₅)(L³PPh₂)Cl] ( 5 ) and {Pd[2‐(Me₂NCH₂)C₆H₄](L³PPh₂)Cl} ( 6 ). The acidity of the NH proton in complexes 3 , 4 , 5 , 6 plays an important role in their catalytic activity. In addition, the palladium complexes cis‐{L¹PPh₂}PdCl₂ ( 1 ) and trans‐{L²PPh₂}₂PdCl₂ ( 2 ) stabilized by phosphines containing Y,C,Y‐chelating ligands L^1,2 have also been found to be useful catalysts for Suzuki–Miyaura reactions in aqueous media. The method can be effectively applied to both activated and deactivated aryl bromides yielding high or moderate conversions. The catalytic activity of couplings performed in pure water increases when utilizing a Pd complex with more acidic NH protons. A decrease of palladium concentration from 1.0 to 0.5 mol% does not lead to a substantial loss of conversion. In addition, Pd complex 1 can be efficiently recovered using two‐phase system extraction. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis,structure and characterization of two new metal–organic coordination polymers based on the ligand 5‐iodobenzene‐1,3‐dicarboxylate

Two new coordination polymers (CPs) formed from 5‐iodobenzene‐1,3‐dicarboxylic acid (H₂iip) in the presence of the flexible 1,4‐bis(1H‐imidazol‐1‐yl)butane (bimb) auxiliary ligand, namely poly[[μ₂‐1,4‐bis(1H‐imidazol‐1‐yl)butane‐κ²N³:N^3′](μ₃‐5‐iodobenzene‐1,3‐dicarboxylato‐κ⁴O¹,O^1′:O³:O^3′)cobalt(II)], [Co(C₈H₃IO₄)(C₁₀H₁₄N₄)]_n or [Co(iip)(bimb)]_n, (1), and poly[[[μ₂‐1,4‐bis(1H‐imidazol‐1‐yl)butane‐κ²N³:N^3′](μ₂‐5‐iodobenzene‐1,3‐dicarboxylato‐κ²O¹:O³)zinc(II)] trihydrate], {[Zn(C₈H₃IO₄)(C₁₀H₁₄N₄)]·3H₂O}_n or {[Zn(iip)(bimb)]·3H₂O}_n, (2), were synthesized and characterized by FT–IR spectroscopy, thermogravimetric analysis (TGA), solid‐state UV–Vis spectroscopy, single‐crystal X‐ray diffraction analysis and powder X‐ray diffraction analysis (PXRD). The iip²⁻ ligand in (1) adopts the (κ¹,κ¹‐μ₂)(κ¹, κ¹‐μ₁)‐μ₃ coordination mode, linking adjacent secondary building units into a ladder‐like chain. These chains are further connected by the flexible bimb ligand in a trans–trans–trans conformation. As a result, a twofold three‐dimensional interpenetrating α‐Po network is formed. Complex (2) exhibits a two‐dimensional (4,4) topological network architecture in which the iip²⁻ ligand shows the (κ¹)(κ¹)‐μ₂ coordination mode. The solid‐state UV–Vis spectra of (1) and (2) were investigated, together with the fluorescence properties of (2) in the solid state.     

The Quest for PdII–PdII Interactions: Structural and Spectroscopic Studies and Ab Initio Calculations on Dinuclear [Pd2(CN)4(μ‐diphosphane)2] Complexes

Structural and spectroscopic properties of and theoretical investigations on dinuclear [Pd₂(CN)₄(P–P)₂] (P–P=bis(dicyclohexylphosphanyl)methane ( 1 ), bis(dimethylphosphanyl)methane ( 2 )) and mononuclear trans‐[Pd(CN)₂(PCy₃)₂] ( 3 ) complexes are described. Xray structural analyses reveal Pd???Pd distances of 3.0432(7) and 3.307(4) Å in 1 and 2 , respectively. The absorption bands at λ>270 nm in 1 and 2 have 4d →5p_σ electronic‐transition character. Calculations at the CIS level indicate that the two low‐lying dipole‐allowed electronic transition bands in model complex [Pd₂(CN)₄(μ‐H₂PCH₂PH₂)₂] at 303 and 289 nm are due to combinations of many orbital transitions. The calculated interaction‐energy curve for the skewed dimer [{trans‐[Pd(CN)₂(PH₃)₂]}₂] is attractive at the MP2 level and implies the existence of a weak Pd^II–Pd^II interaction.     

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.     

A Photoactivatable Platinum(IV) Anticancer Complex Conjugated to the RNA Ligand Guanidinoneomycin

A photoactivatable platinum(IV) complex, trans,trans,trans‐[Pt(N₃)₂(OH)(succ)(py)₂] (succ=succinylate, py=pyridine), has been conjugated to guanidinoneomycin to study the effect of this guanidinum‐rich compound on the photoactivation, intracellular accumulation and phototoxicity of the pro‐drug. Surprisingly, trifluoroacetic acid treatment causes the replacement of an azido ligand and the axial hydroxide ligand by trifluoroacetate, as shown by NMR spectroscopy, MS and X‐ray crystallography. Photoactivation of the platinum–guanidinoneomycin conjugate in the presence of 5′‐guanosine monophosphate (5′‐GMP) led to the formation of trans‐[Pt(N₃)(py)₂(5′‐GMP)]⁺, as does the parent platinum(IV) complex. Binding of the platinum(II) photoproduct {PtN₃(py)₂}⁺ to guanine nucleobases in a short single‐stranded oligonucleotide was also observed. Finally, cellular uptake studies showed that guanidinoneomycin conjugation improved the intracellular accumulation of the platinum(IV) pro‐drug in two cancer cell lines, particularly in SK‐MEL‐28 cells. Notably, the higher phototoxicity of the conjugate in SK‐MEL‐28 cells than in DU‐145 cells suggests a degree of selectivity towards the malignant melanoma cell line.     

Quantum‐chemical analyses of aromaticity,UV spectra,and NMR chemical shifts in plumbacyclopentadienylidenes stabilized by Lewis bases

We carried out a series of zeroth‐order regular approximation (ZORA)‐density functional theory (DFT) and ZORA‐time‐dependent (TD)‐DFT calculations for molecular geometries, NMR chemical shifts, nucleus‐independent chemical shifts (NICS), and electronic transition energies of plumbacyclopentadienylidenes stabilized by several Lewis bases, (Ph)₂(^tBuMe₂Si)₂C₄PbL₁L₂ (L₁, L₂ = tetrahydrofuran, Pyridine, N‐heterocyclic carbene), and their model molecules. We mainly discussed the Lewis‐base effect on the aromaticity of these complexes. The NICS was used to examine the aromaticity. The NICS values showed that the aromaticity of these complexes increases when the donation from the Lewis bases to Pb becomes large. This trend seems to be reasonable when the 4n‐Huckel rule is applied to the fractional π‐electron number. The calculated ¹³C‐ and ²⁰⁷Pb‐NMR chemical shifts and the calculated UV transition energies reasonably reproduced the experimental trends. We found a specific relationship between the ¹³C‐NMR chemical shifts and the transition energies. As we expected, the relativistic effect was essential to reproduce a trend not only in the ²⁰⁷Pb‐NMR chemical shifts and J[Pb‐C] but also in the ¹³C‐NMR chemical shifts of carbons adjacent to the lead atom. © 2014 Wiley Periodicals, Inc.     

1H, 13C, 15N and 195Pt NMR studies of Au(III) and Pt(II) chloride organometallics with 2‐phenylpyridine

¹H, ¹³C, ¹⁵N and ¹⁹⁵Pt NMR studies of gold(III) and platinum(II) chloride organometallics with N(1),C(2′)‐chelated, deprotonated 2‐phenylpyridine (2ppy*) of the formulae [Au(2ppy*)Cl₂], trans(N,N)‐[Pt(2ppy*)(2ppy)Cl] and trans(S,N)‐[Pt(2ppy*)(DMSO‐d₆)Cl] (formed in situ upon dissolving [Pt(2ppy*)(µ‐Cl)]₂ in DMSO‐d₆) were performed. All signals were unambiguously assigned by HMBC/HSQC methods and the respective ¹H, ¹³C and ¹⁵N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Δ^1H_coord = δ^1H_complex ? δ^1H_ligand, Δ^13C_coord = δ^13C_complex ? δ^13C_ligand, Δ^15N_coord = δ^15N_complex ? δ^15N_ligand), as well as ¹⁹⁵Pt chemical shifts and ¹H‐¹⁹⁵Pt coupling constants discussed in relation to the known molecular structures. Characteristic deshielding of nitrogen‐adjacent H(6) protons and metallated C(2′) atoms as well as significant shielding of coordinated N(1) nitrogens is discussed in respect to a large set of literature NMR data available for related cyclometallated compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

catena‐Poly[bis(μ‐2,2′‐bipyridin‐6‐olato)‐κ3N,N′:O;O:N,N′‐dicopper(I,II) [[tetrafluoridoniobium(V)]‐μ‐oxido]]

A novel copper–niobium oxyfluoride, {[Cu₂(C₁₀H₇N₂O)₂][NbOF₄]}_n, has been synthesized by a hydrothermal method and characterized by elemental analysis, EDS, IR, XPS and single‐crystal X‐ray diffraction. The structural unit consists of one C₂‐symmetric [NbOF₄]⁻ anion and one centrosymmetric coordinated [Cu₂(obpy)₂]⁺ cation (obpy is 2,2′‐bipyridin‐6‐olate). In the [NbOF₄]⁻ anion, each Nb^V metal centre is five‐coordinated by four F atoms and one O atom in the first coordination shell, forming a square‐pyramidal coordination geometry. These square pyramids are then further connected to each other via trans O atoms [Nb—O = 2.187 (3) Å], forming an infinite linear {[NbOF₄]⁻}_n polyanion. In the coordinated [Cu₂(obpy)₂]⁺ cation, the oxidation state of each Cu site is disordered, which is confirmed by the XPS results. The disordered Cu sites are coordinated by two N atoms and one O atom from two different obpy ligands. The [NbOF₄]⁻ and [Cu₂(obpy)₂]⁺ units are assembled via weak C—H...F hydrogen bonds, resulting in the formation of a three‐dimensional supramolecular structure. π–π stacking interactions between the pyridine rings [centroid–centroid distance = 3.610 (2) Å] may further stabilize the crystal structure.     

1H, 13C, 17O NMR and quantum‐chemical study of the stereochemistry of the sulfoxide and sulfone derivatives of 3‐arylidene‐1‐thioflavan‐4‐one epoxides

The oxidation of the trans,cis‐( 2 ) and trans,trans‐epoxides ( 3 ) of differently substituted (Z)‐3‐arylidene‐1‐thioflavan‐4‐ones ( 1 ) with dimethyldioxirane (DMD) yielded the appropriate sulfoxides ( 4, 5 ) and sulfones ( 6, 7 ). The structures were elucidated by the extensive application of one‐ and two‐dimensional ¹H, ¹³C and ¹⁷O NMR spectroscopy. The conformational analysis was achieved by the application of ³J(C,H) coupling constants, NOESY responses and ab initio calculations. The preferred ground‐state conformers (twisted envelope‐A, twisted envelope‐B for 6 and twisted envelope‐A, envelope‐B for 7 ) were obtained as global minima of the theoretical ab initio MO study and also the examination of the ¹⁷O and ¹³C chemical shifts, calculated for the global minima structures of the sulfone isomers by the GIAO method. Analogous results, obtained for the sulfoxide isomers ( 4, 5 ), not only led to the preferred conformers but also gave evidence for the trans arrangement of the 2‐Ph group and the oxygen atom of the S?O group. Chemical shift differences between the isomers, sulfoxides and sulfones were corroborated by ab initio calculations of the anisotropic effects of the oxirane ring and the S?O and SO₂ groups. Copyright © 2003 John Wiley & Sons, Ltd.