Complex Mer Research Articles

Photoinduced Reductive C-C and C-Heteroatom Couplings from Bis-cyclometalated Pt(IV) Alkynyl Complexes.

Unsymmetrical dicarboxylato complexes [Pt(tpy)2(O2CR)2] [tpy = cyclometalated 2-(p-tolyl)pyridine, R = Me, CF3] react with the terminal alkynes 4-methoxyphenylacetylene, phenylacetylene, 4-(trifluoromethyl)phenylacetylene or 3,5-difluorophenylacetylene in the presence of a base to produce complexes mer-[Pt(tpy)2(O2CR)(CCAr)], in which the metalated carbon atoms are in a meridional arrangement. Irradiation of the trifluoroacetato derivatives with a 365 nm LED source leads to isomerization to the facial complexes, which can be converted to chlorido derivatives upon reaction with NH4Cl. In contrast, irradiation of the acetato derivatives leads to four different processes, namely, reduction to cis-[Pt(tpy)2], annulations involving one of the tpy ligands and the Cα and Cβ atoms of the alkynyl to give benzoquinolizinium derivatives, isomerization to the facial geometry, or C-O couplings between the acetato ligand and one tpy. The first two processes are favored by the presence of electron-donating groups on the alkynyl, whereas electron-withdrawing groups favor the last two. Irradiation of complexes fac-[Pt(tpy)2(O2CCF3)(CCAr)] with a medium-pressure Hg UV lamp leads to a reductive C-C coupling involving the alkynyl Cα atom and one of the tpy ligands to give pyridoisoindolium derivatives, except for the methoxyphenylacetylide derivative, which is photostable. On the basis of TDDFT calculations, the photoreactivity of the mer complexes is attributed to 3LLCT [π(alkynyl) → π*(tpy)] excited states for annulations or 3LMCT [π(alkynyl) → dσ*] excited states for the rest of the processes, which are accessible through thermal population from 3LC(tpy) states. The C-C couplings from the fac complexes are attributed to photoreactive pentacoordinate intermediates.

Mixed-Isocyanide Complexes of Technetium under Steric and Electronic Control.

Reactions of the alkyl isocyanide fac-[Tc(CO)3(CNR)2Cl] complexes (2) (CNR = CNnBu or CNtBu) with the sterically encumbered isocyanide CNp-FArDarF2 [DArF = 3,5-(CF3)2C6H3] allow a selective exchange of the carbonyl ligands of 2 and the isolation of the mixed-isocyanide complexes mer,trans-[Tc(CNp-FArDarF2)3(CNR)2Cl] (3). Depending on the steric requirements of the residues R, the remaining chlorido ligand can be replaced by another isocyanide ligand. Cationic complexes such as mer-[Tc(CNp-FArDarF2)3(CNnBu)3]+ (4a) or mer,trans-[Tc(CNp-FArDarF2)3(CNnBu)2(CNtBu)]+ (6) have been prepared in this way and isolated as their PF6- salts. mer,trans-[Tc(CNp-FArDarF2)3(CNnBu)2(CNtBu)](PF6) represents to the best of our knowledge the first transition-metal complex with three different isocyanides in its coordination sphere. Since the degree of the ligand exchange seems to be controlled both by the electronic and steric measures of the incoming isocyanides, we undertook similar reactions with the sterically less demanding p-fluorophenyl isocyanide, CNPhpF, which indeed readily led to the hexakis(isocyanide)technetium(I) cation through an exchange of all ligands in the staring materials [Tc2(CO)6(μ-Cl)3]- or fac-[Tc(CO)3(CNR)2Cl]. The influence of the substituents at the isocyanide ligands in such reactions has been reasoned with the density functional theory-derived electrostatic potential at the accessible surface of the corresponding isocyanide carbon atoms.

Facial-Meridional Isomerization and Reductive Elimination in [(R2P-o-C6H4)2N]PtMe3 (R = Ph, iPr).

Treatment of PtMe3I in tetrahydrofuran with either in situ prepared [R-PNP]Li ([R-PNP]- = [(R2P-o-C6H4)2N]-; R = Ph, iPr) or H[R-PNP] in the presence of triethylamine at room temperature affords quantitatively fac-[R-PNP]PtMe3. Thermolysis of fac-[R-PNP]PtMe3 in benzene solutions generates mer-[R-PNP]PtMe3 and ultimately [R-PNP]PtMe and ethane. Complexes mer-[R-PNP]PtMe3 represent the first meridional trialkylplatinum(IV) derivatives to date.

Facial vs. Meridional Coordination Modes in ReI Tricarbonyl Complexes with a Carbodiphosphorane‐based Tridentate Ligand

AbstractThe reactivity of the novel cationic ligand precursor [(dppm)2CH](PF6) (1) with a weakly coordinating anion and [ReBr(CO)5] is reported. The initial coordination results in the formation of the facially coordinated dicationic complex fac‐[({dppm}2CH)Re(CO)3]X2 (fac‐2, X=Br, PF6). The facial coordination mode is retained in fac‐[({dppm}2C)Re(CO)3](PF6) (fac‐3) upon deprotonation of the central cationic donor group. Quantum chemical investigations indicate that for both complexes, 2 and 3, the meridional coordination mode is thermodynamically favored. In line with these findings, the isomerization of the facially coordinated complex fac‐3 to the meridionally coordinated complex mer‐[({dppm}2C)Re(CO)3](PF6) (mer‐3) is observed under irradiation with UV‐light.

A Vanadium(III) Complex with Blue and NIR-II Spin-Flip Luminescence in Solution.

Luminescence from Earth-abundant metal ions in solution at room temperature is a very challenging objective due to the intrinsically weak ligand field splitting of first-row transition metal ions, which leads to efficient nonradiative deactivation via metal-centered states. Only a handful of 3dn metal complexes (n ≠ 10) show sizable luminescence at room temperature. Luminescence in the near-infrared spectral region is even more difficult to achieve as further nonradiative pathways come into play. No Earth-abundant first-row transition metal complexes have displayed emission >1000 nm at room temperature in solution up to now. Here, we report the vanadium(III) complex mer-[V(ddpd)2][PF6]3 yielding phosphorescence around 1100 nm in valeronitrile glass at 77 K as well as at room temperature in acetonitrile with 1.8 × 10-4% quantum yield (ddpd = N,N'-dimethyl-N,N'-dipyridine-2-ylpyridine-2,6-diamine). In addition, mer-[V(ddpd)2][PF6]3 shows very strong blue fluorescence with 2% quantum yield in acetonitrile at room temperature. Our comprehensive study demonstrates that vanadium(III) complexes with d2 electron configuration constitute a new class of blue and NIR-II luminophores, which complement the classical established complexes of expensive precious metals and rare-earth elements.

Novel redox active rhodium(iii) complex with bis(arylimino)acenaphthene ligand: synthesis, structure and electrochemical studies

(Rhodium trichloride reacts with 1,2-bis[(2,6-diisopropylphenyl)imino] acenaphthene (dpp-bian) to afford new octahedral complex mer-[Rh(dpp-bian)(H2O)Cl3]·CH2Cl2. The CV of mer-[Rh(dpp-bian)(H2O)Cl3] in MeCN shows an irreversible reduction that corresponds to the RhIII/RhI couple, followed by reversible or quasi-reversible cathodic waves assigned to reduction of the dpp-bian ligand. DFT calculations confirm the assignment of the redox processes and predict the elimination of two chloride ligands from axial positions upon two-electron reduction of mer-[Rh(dpp-bian)(H2O)Cl3] with the formation of a RhI square-planar complex [RhI(dpp-bian)(H2O)Cl].

Synthesis, Structural Characterization and Photodecarbonylation Study of a Dicarbonyl Ruthenium(II)-Bisquinoline Complex.

A photoactivatable ruthenium(II) carbonyl complex mer,cis‐[Ru(II)Cl(BisQ)(CO)2]PF6 2 was prepared using a tridentate bisquinoline ligand (BisQ=(2,6‐diquinolin‐2‐yl)pyridin). Compound 2 was thoroughly characterized by standard analytical methods and single crystal X‐ray diffraction. The crystal structure of the complex cation reveals a distorted octahedral geometry. The decarbonylation upon exposure to 350 and 420 nm light was monitored by UV/VIS absorbance and Fourier transform infrared spectroscopies in acetonitrile and 1 % (v/v) DMSO in water, respectively. The kinetic of the photodecarbonylation has been elucidated by multivariate curve resolution alternating least‐squares analysis. The stepwise decarbonylation follows a serial mechanism. The first decarbonylation occurs very quickly whereas the second decarbonylation step proceeds more slowly. Moreover, the second rate constant is lower in 1 % (v/v) DMSO in water than in acetonitrile. In comparison to 350 nm irradiation, exposure to 420 nm light in acetonitrile results in a lower second rate constant.

Synthesis and reactivity of an osmium(iii) aminoguanidine complex.

The biological activities of aminoguanidine (GNH2) and its derivatives have been extensively studied due to their properties as radical scavengers and antioxidants. Some of their biological activities may result from their binding to various metals present in biological systems. However, the reactivity of coordinated aminoguanidines has not been investigated. We report herein the synthesis, structure and reactivity of a novel osmium(iii) complex bearing the parent aminoguanidine, mer-[Os{NHC(NH2)(NHNH2)}(L)(CN)3]- (OsGNH2, HL = 2-(2-hydroxyphenyl)benzoxazole). The antioxidant properties of OsGNH2 have been investigated by reactions with various oxidants, including O2, H2O2, m-chloroperbenzoic acid (m-CPBA) and Ce(iv). Various osmium products are produced, which depend on the type of oxidant used. OsGNH2 is readily oxidized by O2 or H2O2 under ambient conditions to afford an osmium(iii) formamidine complex, [OsIII(NH2C[double bond, length as m-dash]NH)(L)(CN)3]- (OsFA, FA = formamidine). With m-CPBA, the nitrosyl complex, mer-[Os(NO)(L)(CN)3]- (OsNO), is formed instead. On the other hand, the nitrido complex mer-[Os(N)(L)(CN)3]- (OsN) is produced when the one-electron oxidant (NH4)2[CeIV(NO3)6] (Ce(iv)) is employed. The molecular structures of OsGNH2 and OsFA have been determined by X-ray crystallography. The oxidation of OsGNH2 to OsFA by O2 or H2O2 is proposed to go through initial dehydrogenation to give a diazoamidine intermediate. In the oxidation by m-CPBA and Ce(iv), it is proposed that the initially formed OsFA is further oxidized to OsNO and OsN, respectively, via osmium(iii) hydrogen cyanamido and osmium(iv) cyanoimido intermediates.

Ru(iii)–TMSO complexes containing azole-based ligands: synthesis and cytotoxicity study

The reaction of mer-[RuCl3(S-TMSO)2(O-TMSO)] with azoles in dichloromethane produced the complexes mer-[RuCl3(S-TMSO)(pzH)2], mer-[RuCl3(S-TMSO)(O-TMSO)(pzH)], mer-[RuCl3(S-TMSO)(dmpzH)2], and mer-[RuCl3(S-TMSO)(O-TMSO)(dmpzH)].

In search of new anticancer drug – Dimethylsulfoxide ruthenium(III) complex with bulky triazolopyrimidine derivative and preliminary studies towards understanding the mode of action

By reacting of [H(dmso)2]trans-[RuCl4(dmso)2] with 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) in molar ratio of M:L = 1:2 new ruthenium(III) complex mer,cis-[RuCl3(dbtp)2(dmso)] has been prepared and structurally characterized by X-ray, IR and EPR spectroscopies. The crystal structure of the Ru(III) complex showed slightly distorted octahedral geometry with unique cis positioned monodentate dbtp ligands bound to the ruthenium(III) ion through the N3 nitrogen atom. In vitro toxicity assay proves that slightly lipophilic the mer,cis-[RuCl3(dbtp)2(dmso)] (logP = 0.80) is 5-fold less toxic against non-tumorigenic human epithelial cell line (MCF-10A) and normal murine embryonic fibroblast cells (BALB/3T3) than cisplatin. Preliminary studies towards understanding the mode of action suggested that activation by reduction, electrostatic interactions of the mer,cis-[RuCl3(dbtp)2(dmso)] with CT-DNA and selective delivery to cells by apotransferrin might be relevant for the biological properties of the complex.

Oxidation in vitro of chromium(III) dietary supplements mer-[Cr(pic)3] and trans(S,S)-[Cr(Cys)2]\u2212 by hydrogen peroxide

Biological tests performed using 3T3 fibroblasts indicated low cytotoxicities for the complexes mer-[Cr(pic)3] and trans(S,S)-[Cr(Cys)2]−, where pic = picolinate anion and Cys = cysteine. Oxidation of these complexes by hydrogen peroxide was studied in NaOH and NaHCO3 media. Electronic (UV–Vis) and EPR spectroscopies were used to monitor the reaction course. Hydrogen peroxide oxidizes chromium(III) to both [CrV(O2)4]3− and CrVIO42− anions in alkaline media and practically completely to CrO42− anion in bicarbonate solution. The reactions follow consecutive biphasic or simple first-order kinetics. The first-order decay of [CrV(O2)4]3− anion at pH ≈ 8 was followed by EPR spectroscopy. Based on the obtained kinetic and spectroscopic data, mechanisms for the redox transformations of these chromium(III) complexes are proposed.

Syntheses, Reactivity, Structures, and Dynamic Properties of Gyroscope-like Iron Carbonyl Complexes Based on Dibridgehead Diarsine Cages

Reactions of BrMg(CH2)mCH═CH2 (m = 4, a; 5, b; 6, c) and AsCl3 (0.30 equiv) give the arsines As((CH2)mCH═CH2)3 (58–70%), which when added to iron tricarbonyl sources yield trans-Fe(CO)3(As((CH2)mCH═CH2)3)2 (66–70%). Reactions with Grubbs’ catalyst (18 mol %, CH2Cl2, reflux) and then hydrogenations (ClRh(PPh3)3/60–80 °C) afford gyroscope-like complexes trans-Fe(CO)3(As((CH2)n)3As) (4a–c, n = 2m + 2; 41–59%/two steps) of idealized D3h symmetry. Additions of NO+BF4– give the isoelectronic and isosteric cations [Fe(CO)2(NO)(As((CH2)n)3As)]+BF4– (5a–c+ BF4–; 81–98%), and [H(OEt2)2]+BArf– (BArf = B(3,5-C6H3(CF3)2)4) gives the hydride complexes mer,trans-[Fe(CO)3(H)(As((CH2)n)3As)]+BArf– (6a–c+ BArf–; 98–99%). Crystal structures of 4a–c and 5b+BF4– are determined. That of 4c suggests enough van der Waals clearance for the Fe(CO)3 moiety to rotate within the As(CH2)14As linkages; that of 4a shows rotation to be blocked by the shorter As(CH2)10As linkages. The rotator dynamics in these complexes are probed by VT N...

Gyroscope-Like Complexes Based on Dibridgehead Diphosphine Cages That Are Accessed by Three-Fold Intramolecular Ring Closing Metatheses and Encase Fe(CO)3, Fe(CO)2(NO)(+), and Fe(CO)3(H)(+) Rotators.

Reactions of trans-Fe(CO)3(P((CH2)mCH═CH2)3)2 (m = a/4; b/5, c/6, e/8) and Grubbs' catalyst (12-24 mol %, CH2Cl2, reflux) give the cage-like trienes trans- Fe(CO)3(P((CH2)mCH═CH(CH2)m)3 P) (3a-c,e, 60-81%). Hydrogenations (ClRh(PPh3)3, 60-80 °C) yield the title compounds trans- Fe(CO)3(P((CH2)n)3 P) (4a-c,e, 74-86%; n = 2m + 2), which have idealized D3h symmetry. A crystal structure of 4c suggests enough van der Waals clearance for the Fe(CO)3 moiety to rotate within the three P(CH2)14P linkages; structures of E,E,E-3a show rotation to be blocked by the shorter P(CH2)4CH═CH(CH2)4P linkages. Additions of NO(+)BF4(-) give the isoelectronic and isosteric cations [ Fe(CO)2(NO)(P((CH2)n)3 P)](+)BF4(-) (5a-c(+)BF4(-); 81-98%). Additions of [H(OEt2)2](+)BArf(-) (BArf = B(3,5-C6H3(CF3)2)4) afford the metal hydride complexes mer,trans-[ Fe(CO)3(H)(P((CH2)n)3 P)](+)BArf(-) (6a-c,e(+)BArf(-); 98-99%). The behavior of the rotators in the preceding complexes is probed by VT NMR. At ambient temperature in solution, 5a,b(+)BF4(-) and 6a(+)BArf(-) show two sets of P(CH2)n/2 (13)C NMR signals (2:1), whereas 5c(+)BF4(-) and 6b,c(+)BArf(-) show only one. At higher temperatures, the signals of 5b(+)BF4(-) coalesce; at lower temperatures, those of 5c(+)BF4(-) and 6b(+)BArf(-) decoalesce. These data give ΔH(⧧)/ΔS(⧧) values (kcal/mol and eu) of 8.3/-28.4 and 9.5/-6.5 for Fe(CO)2(NO)(+) rotation (5b,c(+)) and 6.1/-23.5 for Fe(CO)3(H)(+) rotation (6b(+)). (13)C CP/MAS NMR spectra show that the Fe(CO)3 moiety in polycrystalline 4c (but not 4a) undergoes rapid rotation between -60 and 95 °C. Approaches to minimizing these barriers and developing molecular gyroscopes are discussed.

Dye‐Sensitized Solar‐Cell Performance of a Cobalt(III/II) Redox Mediator with the 2,6‐Bis(8‐quinolinyl)pyridine Ligand

Optical and electrochemical properties of the homoleptic cobalt(III/II) complexes mer,mer-[Co(tpy-κ3N,N′,N″)]n+ and mer,mer-[Co(bqp-κ3N,N′,N″)]n+ (n = 3+ or 2+) are presented [tpy = 2,2′:6′,2″-terpyridine; bqp = 2,6-bis(8′-quinolinyl)pyridine]. Both [Co(tpy)2]3+/2+ and [Co(bqp)2]3+/2+ systems have been used to formulate redox-mediator electrolytes for application in dye-sensitized solar-cell (DSSC) devices with the MK-2 dye TiO2 sensitizer. The [Co(tpy)2]3+/2+-based electrolyte shows a slightly higher percentage power-conversion efficiency (η = 4.47 %) in a DSSC device relative to the [Co(bqp)2]3+/2+-based electrolyte (η = 3.73 %). Although the [Co(bqp)2]3+/2+ electrolyte shows a slightly higher open-circuit potential (VOC = 0.79 V), it suffers from a reduced short-circuit current (JSC = 6.21 mA cm–2) relative to that of the [Co(tpy)2]3+/2+ system (JSC = 10.84 mA cm–2). Tafel and electrochemical impedance analysis (EIS) of symmetric FTO/Pt||Pt/FTO cells, as well as EIS and chronocoulometry of the functional DSSC device are presented. Collectively, this data points toward a decreased turnover of the CoIII/II redox couple at the Pt counter electrode for the [Co(bqp)2]3+/2+ system concomitant with an increased resistance to mass-transfer diffusion.

Chiral (SO)–N–(SO) Sulfoxide Pincer Complexes of Mg, Rh, and Ir: N–H Activation and Selective Sulfoxide Reduction upon Ligand Coordination

Multigram quantities of the optically pure amino–bis-sulfoxide ligand (S,S)-bis(4-tert-butyl-2-(p-tolylsulfinyl)phenyl)amine ((S,S)-3) are accessible by in situ lithiation of bis(2-bromo-4-tert-butylphenyl)amine (1) followed by a nucleophilic displacement reaction with Andersen’s sulfinate 2. Deprotonation of (S,S)-3 with MgPh2 yields the magnesium amido–bis-sulfoxide salt (S,S)-4 quantitatively. Metathetical exchange of (S,S)-4 with [RhCl(COE)2]2 affords the optically pure pseudo-C2-symmetric Rh(I)–amido bis-sulfoxide pincer complex mer-(R,R)-[Rh(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amide)(COE)] (mer-(R,R)-5). This complex reacts with 3 equiv of HCl to give the facial Rh(III) complex fac-(S,R,R)-[Rh(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amine)Cl3] (fac-(S,R,R)-6), in which one of the sulfoxide functions has been reduced to the sulfide and in which the resulting sulfoxide–sulfide–amine ligand is facially coordinated. The same complexes 5 and 6 form in a 1:2 ratio in a disproportionation reaction when [RhCl(COE)2]2 is treated with 2 equiv of neutral ligand 3. N–H activation is directly observed in the reaction of [IrCl(COE)2]2 with 3, affording the amido–hydrido–Ir(III) complex [Ir(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amide)(Cl)(H)(COE)] (8).

Rh–POP Pincer Xantphos Complexes for C–S and C–H Activation. Implications for Carbothiolation Catalysis

The neutral Rh(I)–Xantphos complex [Rh(κ3-P,O,P-Xantphos)Cl]n, 4, and cationic Rh(III) [Rh(κ3-P,O,P-Xantphos)(H)2][BArF4], 2a, and [Rh(κ3-P,O,P-Xantphos-3,5-C6H3(CF3)2)(H)2][BArF4], 2b, are described [ArF = 3,5-(CF3)2C6H3; Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; Xantphos-3,5-C6H3(CF3)2 = 9,9-dimethylxanthene-4,5-bis(bis(3,5-bis(trifluoromethyl)phenyl)phosphine]. A solid-state structure of 2b isolated from C6H5Cl solution shows a κ1-chlorobenzene adduct, [Rh(κ3-P,O,P-Xantphos-3,5-C6H3(CF3)2)(H)2(κ1-ClC6H5)][BArF4], 3. Addition of H2 to 4 affords, crystallographically characterized, [Rh(κ3-P,O,P-Xantphos)(H)2Cl], 5. Addition of diphenyl acetylene to 2a results in the formation of the C–H activated metallacyclopentadiene [Rh(κ3-P,O,P-Xantphos)(ClCH2Cl)(σ,σ-(C6H4)C(H)═CPh)][BArF4], 7, a rare example of a crystallographically characterized Rh–dichloromethane complex, alongside the Rh(I) complex mer-[Rh(κ3-P,O,P-Xantphos)(η2-PhCCPh)][BArF4], 6. Halide abstraction from [Rh(κ3-P,O,P-Xantphos)Cl]n in the presence of diphenylacetylene affords 6 as the only product, which in the solid state shows that the alkyne binds perpendicular to the κ3-POP Xantphos ligand plane. This complex acts as a latent source of the [Rh(κ3-P,O,P-Xantphos)]+ fragment and facilitates ortho-directed C–S activation in a number of 2-arylsulfides to give mer-[Rh(κ3-P,O,P-Xantphos)(σ,κ1-Ar)(SMe)][BArF4] (Ar = C6H4COMe, 8; C6H4(CO)OMe, 9; C6H4NO2, 10; C6H4CNCH2CH2O, 11; C6H4C5H4N, 12). Similar C–S bond cleavage is observed with allyl sulfide, to give fac-[Rh(κ3-P,O,P-Xantphos)(η3-C3H5)(SPh)][BArF4], 13. These products of C–S activation have been crystallographically characterized. For 8 in situ monitoring of the reaction by NMR spectroscopy reveals the initial formation of fac-κ3-8, which then proceeds to isomerize to the mer-isomer. With the para-ketone aryl sulfide, 4-SMeC 6H4COMe, C–H activation ortho to the ketone occurs to give mer-[Rh(κ3-P,O,P-Xantphos)(σ,κ1-4-(COMe)C6H3SMe)(H)][BArF4], 14. The temporal evolution of carbothiolation catalysis using mer-κ3-8, and phenyl acetylene and 2-(methylthio)acetophenone substrates shows initial fast catalysis and then a considerably slower evolution of the product. We suggest that the initially formed fac-isomer of the C–S activation product is considerably more active than the mer-isomer (i.e., mer-8), the latter of which is formed rapidly by isomerization, and this accounts for the observed difference in rates. A likely mechanism is proposed based upon these data.

Ruthenium chalcogenonitrosyl and bridged nitrido complexes containing chelating sulfur and oxygen ligands.

Ruthenium thio- and seleno-nitrosyl complexes containing chelating sulfur and oxygen ligands have been synthesised and their de-chalcogenation reactions have been studied. The reaction of mer-[Ru(N)Cl3(AsPh3)2] with elemental sulfur and selenium in tetrahydrofuran at reflux afforded the chalcogenonitrosyl complexes mer-[Ru(NX)Cl3(AsPh3)2] [X = S (1), Se (2)]. Treatment of 1 with KN(R2PS)2 afforded trans-[Ru(NS)Cl{N(R2PS)2}2] [R = Ph (3), Pr(i) (4), Bu(t) (5)]. Alternatively, the thionitrosyl complex 5 was obtained from [Bu(n)4N][Ru(N)Cl4] and KN(Bu(t)2PS)2, presumably via sulfur atom transfer from [N(Bu(t)2PS)2](-) to the nitride. Reactions of 1 and 2 with NaLOEt (LOEt(-) = [Co(η(5)-C5H5){P(O)(LOEt)2}3](-)) gave [Ru(NX)LOEtCl2] (X = S (8), Se (9)). Treatment of [Bu(n)4N][Ru(N)Cl4] with KN(R2PS)2 produced Ru(IV)-Ru(IV)μ-nitrido complexes [Ru2(μ-N){N(R2PS)2}4Cl] [R = Ph (6), Pr(i) (7)]. Reactions of 3 and 9 with PPh3 afforded 6 and [Ru(NPPh3)LOEtCl2], respectively. The desulfurisation of 5 with [Ni(cod)2] (cod = 1,5-cyclooctadiene) gave the mixed valance Ru(III)-Ru(IV)μ-nitrido complex [Ru2(μ-N){N(Bu(t)2PS)2}4] (10) that was oxidised by [Cp2Fe](PF6) to give the Ru(IV)-Ru(IV) complex [Ru2(μ-N){N(Bu(t)2PS)2}4](PF6) ([10]PF6). The crystal structures of 1, 2, 3, 7, 9 and 10 have been determined.

Exploring excited-state tunability in luminescent tris-cyclometalated platinum(IV) complexes: synthesis of heteroleptic derivatives and computational calculations.

The synthesis, structure, electrochemistry, and photophysical properties of a series of heteroleptic tris- cyclometalated Pt(IV) complexes are reported. The complexes mer-[Pt(C^N)2 (C'^N')]OTf, with C^N=C-deprotonated 2-(2,4-difluorophenyl)pyridine (dfppy) or 2-phenylpyridine (ppy), and C'^N'=C-deprotonated 2-(2-thienyl)pyridine (thpy) or 1-phenylisoquinoline (piq), were obtained by reacting bis- cyclometalated precursors [Pt(C^N)2 Cl2] with AgOTf (2 equiv) and an excess of the N'^C'H pro-ligand. The complex mer-[Pt(dfppy)2 (ppy)]OTf was obtained analogously and photoisomerized to its fac counterpart. The new complexes display long-lived luminescence at room temperature in the blue to orange color range. The emitting states involve electronic transitions almost exclusively localized on the ligand with the lowest π-π* energy gap and have very little metal character. DFT and time-dependent DFT (TD-DFT) calculations on mer-[Pt(ppy)2 (C'^N')](+) (C'^N'=thpy, piq) and mer/fac-[Pt(ppy)3](+) support this assignment and provide a basis for the understanding of the luminescence of tris-cyclometalated Pt(IV) complexes. Excited states of LMCT character may become thermally accessible from the emitting state in the mer isomers containing dfppy or ppy as chromophoric ligands, leading to strong nonradiative deactivation. This effect does not operate in the fac isomers or the mer complexes containing thpy or piq, for which nonradiative deactivation originates mainly from vibrational coupling to the ground state.

Structure and properties of tripyridine nitrosocomplexes of ruthenium: mer-[Ru(NO)Py3Cl(OH)]Cl·1.5H2O and mer-[Ru(NO)Py3Cl(H2O)]Cl2·2H2O·0.5HCl

The reaction of K2[Ru(NO)Cl5] with pyridine in aqueous ethanol at pH ∼ 7–8 affords a nitrosoruthenium hydroxocomplex mer-[Ru(NO)Py3Cl(OH)]Cl·1.5H2O (I) (yield ∼55%). Treatment of hydroxocomplex I with hydrochloric acid at room temperature gives the aqua complex mer-[Ru(NO)Py3Cl(H2O)]Cl2·2H2O·0.5HCl (II). The structures of the compounds are determined by X-ray crystallography: I, space group P21/n, a = 9.2292(4) A, b = 11.7781(4) A, c = 17.4915(7) A, β = 90.9560(10)°, R = 4.84%; II, space group P-1, a = 7.3528(9) A, b = 11.5793(11) A, c = 13.6961(16) A, α = 84.558(3)°, β = 87.668(4)°, γ = 74.146(4)°, R = 6.22%. Compounds I and II are characterized by powder XRD, 1H and 13C NMR, and IR spectroscopy. The thermal decomposition of compound II in the inert atmosphere is examined by thermal analysis.

Solvent-Dependent Formation of Os(0) Complexes by Electrochemical Reduction of [Os(CO)(2,2′-bipyridine)(L)Cl2]; L = Cl–, PrCN

Cyclic voltammetry and ultraviolet-visible/infrared (UV-vis/IR) spectroelectrochemistry were used to study the cathodic electrochemical behavior of the osmium complexes mer-[Os(III)(CO) (bpy)Cl3] (bpy = 2,2'-bipyridine) and trans(Cl)-[Os(II)(CO) (PrCN)(bpy)Cl2] at variable temperature in different solvents (tetrahydrofuran (THF), butyronitrile (PrCN), acetonitrile (MeCN)) and electrolytes (Bu4NPF6, Bu4NCl). The precursors can be reduced to mer-[Os(II)(CO) (bpy(•-))Cl3](2-) and trans(Cl)-[Os(II)(CO)(PrCN) (bpy(•-))Cl2](-), respectively, which react rapidly at room temperature, losing the chloride ligands and forming Os(0) species. mer-[Os(III)(CO) (bpy)Cl3] is reduced in THF to give ultimately an Os-Os-bonded polymer, probably [Os(0)(CO) (THF)(bpy)]n, whereas in PrCN the well-soluble, probably mononuclear [Os(0)(CO) (PrCN)(bpy)], species is formed. The same products were observed for the 2 electron reduction of trans(Cl)-[Os(II)(CO)(PrCN) (bpy)Cl2] in both solvents. In MeCN, similar to THF, the [Os(0)(CO) (MeCN)(bpy)]n polymer is produced. It is noteworthy that the bpy ligand in mononuclear [Os(0)(CO) (PrCN)(bpy)] is reduced to the corresponding radical anion at a significantly less negative potential than it is in polymeric [Os(0)(CO) (THF)(bpy)]n: ΔE1/2 = 0.67 V. Major differences also exist in the IR spectra of the Os(0) species: the polymer shows a broad ν(CO) band at much smaller wavenumbers compared to the soluble Os(0) monomer that exhibits a characteristic ν(Pr-CN) band below 2200 cm(-1) in addition to the intense and narrow ν(CO) absorption band. For the first time, in this work the M(0)-bpy (M = Ru, Os) mono- and dicarbonyl species soluble in PrCN have been formulated as a mononuclear complex. Density functional theory (DFT) and time-dependent-DFT calculations confirm the Os(0) oxidation state and suggest that [Os(0)(CO) (PrCN)(bpy)] is a square planar moiety. The reversible bpy-based reduction of [Os(0)(CO) (PrCN)(bpy)] triggers catalytic reduction of CO2 to CO and HCOO(-).