Homo- and hetero-bridged mixed-valence dinuclear complexes which contain the fragment ‘Rh(C6F5)3’

The reaction of the anionic mononuclear rhodium complex [Rh(C₆F₅)₃Cl(Hpz)]^t- (Hpz = pyrazole, C₃H₄N₂) with methoxo or acetylacetonate complexes of Rh or Ir led to the heterodinuclear anionic compounds [(C₆F₅)₃Rh(μ-Cl)(μ-pz)M(L₂)] [M = Rh, L₂ = cyclo-octa-1,5-diene, COD (1), tetrafluorobenzobarrelene, TFB (2) or (CO)₂ (4); M = Ir, L₂ = COD (3)]. The complex [Rh(C₆F₅)₃(Hbim)]⁻ (5) has been prepared by treating [Rh(C₆F₅)₃(acac)]⁻ with H₂bim (acac = acetylacetonate; H₂bim = 2,2′-biimidazole). Complex 5 also reacts with Rh or Ir methoxo, or with Pd acetylacetonate, complexes affording the heterodinuclear complexes [(C₆F₅)₃Rh(μ-bim)M(L₂)]⁻ [M = Rh, L₂ = COD (6) or TFB (7); M = Ir, L₂ = COD (8); M = Pd, L₂ = η³-C₃H₅ (9)]. With [Rh(acac)(CO)₂], complex 5 yields the tetranuclear complex [{(C₆F₅)₃Rh(μ-bim)Rh(CO)₂}₂]₂₋. Homodinuclear Rh^III derivatives [{Rh(C₆F₅)₃}₂(μ-L)₂]^·- [L₂ = OH, pz (11); OH, S^tBu (12); OH, SPh (13); bim (14)] have been obtained by substitution of one or both hydroxo groups of the dianion [{Rh(C₆F₅)₃(μ-OH)}₂]²⁻ by the corresponding ligands. The reaction of [Rh(C₆F₅)₃(Et₂O)_x] with [PdX₂(COD)] produces neutral heterodinuclear compounds [(C₆F₅)₃Rh(μ-X)₂Pd(COD)] [X = Cl (15); Br (16)]. The anionic complexes 1–14 have been isolated as the benzyltriphenylphosphonium (PBzPh₃⁺) salts.     

Mechanistic investigation of CO2 hydrogenation by Ru(II) and Ir(III) aqua complexes under acidic conditions: two catalytic systems differing in the nature of the rate determining step

Ruthenium aqua complexes [(eta(6)-C(6)Me(6))Ru(II)(L)(OH(2))](2+) {L = bpy (1) and 4,4'-OMe-bpy (2), bpy = 2,2'-bipyridine, 4,4'-OMe-bpy = 4,4'-dimethoxy-2,2'-bipyridine} and iridium aqua complexes [Cp*Ir(III)(L)(OH(2))](2+) {Cp* = eta(5)-C(5)Me(5), L = bpy (5) and 4,4'-OMe-bpy (6)} act as catalysts for hydrogenation of CO(2) into HCOOH at pH 3.0 in H(2)O. The active hydride catalysts cannot be observed in the hydrogenation of CO(2) with the ruthenium complexes, whereas the active hydride catalysts, [Cp*Ir(III)(L)(H)](+) {L = bpy (7) and 4,4'-OMe-bpy (8)}, have successfully been isolated after the hydrogenation of CO(2) with the iridium complexes. The key to the success of the isolation of the active hydride catalysts is the change in the rate-determining step in the catalytic hydrogenation of CO(2) from the formation of the active hydride catalysts, [(eta(6)-C(6)Me(6))Ru(II)(L)(H)](+), to the reactions of [Cp*Ir(III)(L)(H)](+) with CO(2), as indicated by the kinetic studies.     

Synthesis, structure and reactivity of homobimetallic Rh(I) and Ir(I) complexes of s- and as-indacene-diide

The Rh(COD) and Ir(COD) homobimetallic complexes of s-indacene-diide, 2,6-dimethyl-s-indacene-diide, as-indacene-diide, and 2,7-dimethyl-as-indacene-diide have been synthesized from the di-lithium salts of the dianions and metal dimers [M(μ-Cl)L₂]₂ (M = Rh, Ir; L₂ = COD, NBD, (ethylene)₂, (CO)₂ as mixtures of syn and anti isomers. The syn/anti ratio depends on the nature of the ancillary ligands at the metal and on the s or as geometry of the bridging ligand. In the reaction of the 2,7-dimethyl-as-indacene-diide-[M(COD)]₂ species with CO, the higher reactivity of the syn isomers has been justified on the basis of a greater instability of the ground state due to steric interactions between the COD groups. Bis-η¹ metal-bonded intermediates have been identified in the carbonylation of iridium derivatives; on the other hand, the formation of the bis-η⁵ mixed complexes syn and anti-{2,7-dimethyl-as-indacene-diide-[Rh(COD)][Rh(CO)₂]} and their reactivity strongly support the existence of metal---metal interaction in the rhodium derivatives.     

简单的配体改变调控钌配合物催化还原CO2的活性：硼基配体的对位效应和Ru―H键的性质

开发高效的催化剂用于催化还原CO₂转化为甲酸和它的盐类已经成为研究的热点,是因为将CO₂转化为C1产物不仅可以解决CO₂的含量升高带来的环境问题,还可以解决化石能源燃烧日趋严重的问题。贵金属配合物催化CO₂转化为甲酸和甲酸盐类是目前这类反应最有效的方式,尤其是Ru、Ir和Rh等贵金属。我们之前的研究结果表明Ir(Ⅲ), Ru(Ⅱ)类配合物催化还原CO₂转化为甲酸盐的活性是由配合物Ru―H键的成键性质决定的。它们能高活性的催化CO₂是由于它们都含有同一种特点的Ru―H键,是由Ru的sd²杂化轨道和H的1s轨道杂化而成的,而且这一特点可以被活性氢的对位配体显著影响。鉴于硼基配体具有强的对位效应,我们基于高活性的均相催化剂Ru(PNP)(CO)H₂ (PNP = 2, 6-二(二叔丁基磷甲基)-吡啶)设计了Ru-PNP-HBcat和Ru-PNP-HBpin,并计算了二者催化还原CO₂的活性。Bcat和Bpin配体是实验上常用的硼基配体。我们的计算结果表明Ru-PNP-HBcat和Ru-PNP-HBpin有比Ru-PNP-H₂更长的Ru―H键、亲核性更强的活性氢,其Ru―H键中的Ru原子的d轨道杂化成分的贡献也比Ru-PNP-H₂的更少。相应地Ru-PNP-HBcat和Ru-PNP-HBpin活化CO₂的能垒比Ru-PNP-H₂低。而且Ru-PNP-H₂、Ru-PNP-HBcat和Ru-PNP-HBpin催化CO₂转化为甲酸盐的能垒分别为76.2、67.8、54.4 kJ∙mol^-1,表明Ru-PNP-HBpin具有最高的催化活性。因此,钌配合物催化还原CO₂的活性可由硼基配体强的对位效应和Ru―H键的成键性质来调控。     

Rhodium complexes with dioximes as catalysts of hydroformylation and hydrogenation of 1-hexene

Rhodium(II) complexes with dioximes [Rh(Hdmg)₂(PPh₃)]₂ [I] (Hdmg=monoanion of dimethylglyoxime) and [Rh(Hdmg)(ClZndmg)(PPh₃)]₂ [II] catalyse hydroformylation and hydrogenation reactions of 1-hexene at 1 MPa CO/H₂ and 0.5 MPa H₂ at 353 K, respectively. Hydroformylation with complex [I] produces 94% of aldehydes (n/iso=2.2) and 6% 2-hexene whereas the second catalyst [II] gives ca. 40% of aldehydes (n/iso=2.1) and 60% of 2-hexene. Corresponding Rh(III) complexes are inactive in hydroformylation except of RhH(Hdmg)₂(PPh₃) [III], which shows activity similar to [I]. Complexes [Rh(Hdmg)₂(PPh₃)]₂ [I], [Rh(Hdmg)(ClZndmg)(PPh₃)]₂ [II], RhH(Hdmg)₂(PPh₃) [III] and [Rh(Hdmg)₂(PPh₃)₂]ClO₄ [V] catalyse 1-hexene hydrogenation with an average TON ca. 18 cycles/mol [Rh]×min. Complex [II] has also been found to catalyse hydrogenation of cyclohexene, 1,3-cyclohexadiene and styrene.     

Preparation and characterization of ruthenium(II), rhodium(III) and iridium(III) complexes of isocyanide bearing the azo group

Reactions of [(η⁶-arene)RuCl₂]₂ (1) (η⁶-arene=p-cymene (1a), 1,3,5-Me₃C₆H₃ (1b), 1,2,3-Me₃C₆H₃ (1c) 1,2,3,4-Me₄C₆H₂(1d), 1,2,3,5-Me₄C₆H₂ (1e) and C₆Me₆ (1f)) or [Cp*MCl₂]₂ (M=Rh (2), Ir (3); Cp*=C₅Me₅) with 4-isocyanoazobenzene (RNC) and 4,4′-diisocyanoazobenzene (CN–R–NC) gave mononuclear and dinuclear complexes, [(η⁶-arene)Ru(CNC₆H₄N=NC₆H₅)Cl₂] (4a–f), [Cp*M(CNC₆H₄N=NC₆H₅)Cl₂] (5: M=Rh; 6: M=Ir)_, [{(η⁶-arene)RuCl₂}₂{μ-CNC₆H₄N=NC₆H₄NC}] (8a–f) and [(Cp*MCl₂)₂(μ-CNC₆H₄N=NC₆H₄NC)}] (9: M=Rh; 10: M=Ir)_, respectively. It was confirmed by X-ray analyses of 4a and 5 that these complexes have trans-forms for the ---N=N--- moieties. Reaction of [Cp*Rh(dppf)(MeCN)](PF₆)₂ (dppf=1,1′-bis (diphenylphosphino)ferrocene) with 4-isocyanoazobenzene gave [Cp*Rh(dppf)(CNC₆H₄N=NC₆H₅)](PF₆)₂ (7), confirmed by X-ray analysis. Complex 8b reacted with Ag(CF₃SO₃), giving a rectangular tetranuclear complex 11b, [{(η⁶-1,3,5-Me₃C₆H₃)Ru(μ-Cl}₄(μ-CNC₆H₄N=NC₆H₄NC)₂](CF₃SO₃)₄ bridged by four Cl atoms and two μ-diisocyanoazobenzene ligands. Photochemical reactions of the ruthenium complexes (4 and 8) led to the decomposition of the complexes, whereas those of 5, 7, 9 and 10 underwent a trans-to-cis isomerization. In the electrochemical reactions the reductive waves about −1.50 V for 4 and −1.44 V for 8 are due to the reduction of azo group, [---N=N---]→[---N=N---]²⁻. The irreversible oxidative waves at ca. 0.87 V for the 4 and at ca. 0.85 V for 8 came from the oxidation of Ru(II)→Ru(III).     

The lively chemistry of the di-μ-methylene-bis(pentamethylcyclopentadienyl-rhodium) complexes, analogues of surface reactions in heterogeneous catalysis

The chemistry of the di-μ-methylene-bis(pentamethylcyclopentadienyl-rhodium) complexes is reviewed. The complex [{(η⁵-C₅Me₅)RhCl₂}₂] (1a) reacted with MeLi to give, after oxidative work-up, blood-red cis-[{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(Me)₂], 2. This has the two rhodiums in the +4 oxidation state (d⁵), and linked by a metal-metal bond (2.620 Å). Trans-2 was formed on isomerisation of cis-2 in the presence of Lewis acids, or by direct reaction of 1a with Al₂Me₆, followed by dehydrogenation with acetone. The Rh-methyls in [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(Me)₂] were readily replaced under acidic conditions (HX) to give [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(X)₂] (X = Cl, Br or I); these latter complexes reacted with a variety of RMgX to give [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(R)₂] (R = alkyl, Ph, vinyl, etc.). Trans-2 also reacted with HBF₄ in the presence of L to give first [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(Me)(L)]⁺ and then [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(L)₂]²⁺ (L = MeCN, CO, etc.). The {(η⁵-C₅Me₅)Rh(μ-CH₂)}₂ core is rather kinetically inert and also forms a variety of complexes with oxy-ligands, both cis-, e.g. [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(μ-OAc)]⁺ and trans-, such as [(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(H₂O)₂]²⁺. The complexes [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(R)L]⁺ (R = Me or aryl) in the presence of CO, or [{(η⁵-C₄Me₅)Rh(μ-CH₂)}₂(R)₂] (R = Me, Ph or CO₂Me) in the presence of mild oxidants, readily yield the C---C---C coupled products RCH=CH₂. The mechanisms of these couplings have been elucidated by detailed labelling studies: they are more complex than expected, but allow direct analogies to be drawn to C---C couplints that occur during Fischer-Tropsch reactions on rhodium surfaces.     

Rhodium and iridium complexes of an asymmetric bicyclic NHC bearing secondary pyridyl donors

A tridentate N^C^N ligand, 1, containing a bicyclic central NHC ring and two flanking pyridyl groups has been coordinated to Rh(I) and Ir(I) to give complexes of the type [M(κ(3)-1)(1,5-COD)]PF(6) (2 M = Rh; 3 M = Ir). In contrast to our earlier study with this ligand, the complexes have been shown to approximate to a trigonal bipyramidal geometry in the solid state and exist as an isomeric mixture in solution as determined by (1)H and (13)C NMR spectroscopy. Electrochemical studies revealed that both complexes undergo a 1-electron oxidation with the potential of the Rh complex 0.1 V less than that of the Ir complex in CH(2)Cl(2). Preliminary DFT studies confirm the lowest energy conformations as those seen in the solid state and show the location and energy of the HOMOs to be identical in 2 and 3. Partial charge analysis shows a greater positive charge on the Ir in 3 compared to the Rh in 2. Some preliminary studies of hydrogenation reactivity have shown the complexes to be efficient for both transfer and direct hydrogenation of prochiral ketones and alkenes at moderate temperatures but without any discernible enantioselectivity.     

Some transition metal complexes of new terdentate ligands: Bis[2-(diphenylphosphino)ethyl]benzylamine and bis[2-(diphenylarsino)ethyl)benzylamine

Complexes of the terdentate ligands bis[2-diphenylphosphino)ethyl]benzylamine (DPBA) and bis[2-(diphenylarsino)ethyl]benzylamine (DABA) with Co(II), Ni(II), Pd(II), Pt(II), Rh(III), Ir(III), Rh(I) and Ir(I) are reported. The ligand DPBA reacts with Co(II) ion to form two types of complexes: a high-spin, paramagnetic, tetrahedral Co(II) complex of composition [CoCl(DPBA)]Cl and a low-spin, paramagnetic, square-planar complex of composition [CoBr(DPBA)]B(C₆H₅)₄. The reaction of DPBA with Ni(II) ion in methanol yields low-spin, diamagnetic, square-planar complexes of type [NiX(DPBA)]Y [X = Cl, Br or I; Y = Cl or B(C₆H₅)₄]. Four-coordinate, square-planar, cationic complexes of type [MY(L⁺[M = Pd(II), Pt(II), Rh(I) or Ir(I); Y = Cl or P(C₆H₅)₃; L = DPBA or DABA], were obtained on reaction of L with various starting materials containing these metal ions. Reaction of DPBA and DABA with rhodium and iridium trichlorides gave octahedral, neutral complexes of general formula [MCl₃(L)] (M = Rh or Ir, L = DPBA or DABA). All the complexes were characterized on the basis of their elemental analysis, molarconductance data, magnetic susceptibilities, electronic spectra, IR spectral measurements, and¹H and³¹P-{¹H} NMR spectral data.     

Thermodynamics of the hydrogenation of olefins catalyzed by Rh(I) and Ir(I) complexes

The homogeneous hydrogenation of cyclohexene catalyzed by Rh(I) and Ir(I) complexes of the terdentate ligands (L) HN(CH₂CH₂Aφ₂)₂ (A = P, As) was investigated in the temperature range 20 - 50°C. Thermodynamic parameters corresponding to the formation of the dihydrido complexes ML(H)₂Cl (M = Ir(I), Rh(I)) and the olefin complexes MLCl(olefin) were computed. The activation parameters corresponding to the rate constant were also calculated. An inverse relationship is found between the enthalpy of formation ΔH⁰ of the dihydrido complexes and the enthalpy of activation ΔH^≠ of the hydrogenation step. This relationship establishes the involvement of the dihydrido complexes as the active intermediates in olefin coordination and hydrogen transfer. The stereochemistry of the terdentate complexes in dihydride formation is discussed. It is concluded that the enthalpy of formation ΔH⁰ of the dihydrido complexes of terdentate ligands is very favourable, as there is no change in the configuration of the ligand in oxidative addition reaction. The significance of the steric factors in the hydrogenation step is discussed.     

Synthesis and characterization of Ru(III), Rh(III), Pt(IV) and Ir(III) thiosemicarbazone complexes

Ru(III), Rh(III), Pt(IV) and Ir(III) complexes of 2-furfural thiosemicarbazone as ligand have been synthesised. These complexes have the composition [M(ligand)₂X₂]X (M = Ru(III) Rh(III) and Ir(III) X = Cl and Br) and [Pt(ligand)₂ X₂] X₂ (X = Cl, Br and 1/2SO₄). The deprotonated ligand forms the complexes of the formulae M(ligand-H)₃ and Pt(ligand-H)₃Cl. All these complexes have been characterized by elemental analysis, magnetic measurements, electronic and infrared spectral studies. All the complexes are six-coordinate octahedral.     

Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Ir: C-H and N-H activation and catalytic transfer hydrogenation

Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amine-NHC and amido-NHC ligands are scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a primary-amine functionalised imidazolium salt 2b with [(p-cymene)RuCl(2)](2) and [Cp*MCl(2)](2) (M = Rh, Ir). Treating 2a with [Cp*MCl(2)](2) and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M = Rh, 3; M = Ir, 4), resulting from aromatic C-H activation. In contrast, treating 2b with [(p-cymene)RuCl(2)](2), Ag(2)O and KI gave the amine-NHC complex [(p-cymene)Ru(C,NH(2))I]I (5). The reaction of 2b with [Cp*MCl(2)](2) (M = Rh, Ir), NaO(t)Bu and KI gave the amine-NHC complex [Cp*Rh(NH(2))I]I (6) or the amido-NHC complex Cp*Ir(C,NH)I (7); both protonation states of the Ir complex could be accessed: treating 7 with trifluoroacetic acid gave the amine-NHC complex [Cp*Ir(C,NH(2))I][CF(3)CO(2)] (8). These are the first primary amine- or amido-NHC complexes of Rh and Ir. Solid-state structures of the complexes 3-8 have been determined by single crystal X-ray diffraction. Complexes 5, 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity.     

Stepwise formation of quasi-octahedral macrocyclic complexes of rhodium(III) and iridium(III) bearing a pentamethylcyclopentadienyl group

Reactions of [[MCl2(Cp*)]2] (1: M=Ir, 2: M=Rh) with bidentate ligands (L) such as 1,4-diisocyano-2,5-dimethylbenzene (a), 1,4-diisocyano-2,3,5,6-tetramethylbenzene (b), pyrazine (c) or 4,4'-dipyridyl (d) gave the corresponding dinuclear complexes [[MCl2(Cp*)]2(L)] (M=Ir: 3a, 3b, 5c, 5d; M=Rh: 4b, 6c, 6d), which were converted into tetranuclear complexes [[M2(mu-Cl)2(Cp*)2]2(L)2](OTf)4 (M=Ir: 7c, 7d, 9a, 9b; M=Rh: 8e, 8d, 10b) on treatment with Ag(OTf). X-ray analyses of 8c and 8d revealed that each of four pentamethylcyclopentadienyl metal moieties was connected by two mu-Cl-bridged atoms and a bidentate ligand to construct a rectangular cavity with the dimensions of 3.7 x 7.0 A for 8c and 3.7 x 11.5 A for 8d. Both the Rh2Cl2 and pyrazine (or 4,4'dipyridyl) ring planes are perpendicular to the Rh4 plane. Treatment of Cl-bridged complexes (7c, 7d, 8e, 8d, 9b, and 10b) with a different ligand (L') resulted in cleavage of the Cl bridges to produce two-dimensional complexes [[MCl(Cp*)]4[(L)-(L')]2](OTf)4 (11ac, 11bc, 11bd, 12bc, and 12bd) with two different ligand "edges". Complex 10b reacted readily with 1,4-diisocyano-2,3,5,6-tetramethylbenzene (b) to give a tetranuclear rhodium(III) complex 12bb. The structure of tetranuclear complexes was confirmed by X-ray analysis of 11bc. Each [MCp*] moiety is surrounded by a Cl atom, isocyanide, and pyrazine (or 4,4'-dipyridyl) and the dimensions of its cavity are 7.0 x 11.6 A.     

Ortho-Metallation reactions V. Reactions of rhodium complexes with azobenzene

Hydrated rhodium(III) chloride reacts with azobenzene (HAzb) affording RhCl₃(PhNH₂)₂ and the dimeric [(Azb)₂RhCl]₂. The latter reacts with donor ligands to give (Azb)₂RhCl(L), (L=PPh₃, tetrahydrofuran). With [Rh(CO)₂Cl]₂, azobenzene affords an unusual Rh^I---Rh^III complex, [(Azb)₂RhCl₂Rh(CO)₂], which can also be obtained from [Rh(CO)₂Cl]₂ and [(Azb)₂RhCl]₂. These complexes contain the ortho-metallated (phenylazo)phenyl-2C,N′ ligand, and their spectroscopic properties are summarised.     

Rhodium phosphine complexes immobilized on silica as active catalysts for 1-hexene hydroformylation and arene hydrogenation

In immobilizing the rhodium complexes [Rh(acac)(CO)(P)] (1) and [Rh(acac)(P)₂] (2) (P = Ph₂PCH₂CH₂Si(OMe)₃) onto SiO₂, acetylacetone is found to be released through protonation of the acac ligand by the acidic silica-OH groups. The resulting complexes [Rh(O-{SiO₂}(HO-{SiO₂})(CO)(P-{SiO₂})] (1a) and [Rh(O-{SiO₂})(HO-{SiO₂})(P-{SiO₂})₂] (2a) were successfully tested with respect to their catalytic action on 1-hexene hydroformylation as well as benzene and toluene hydrogenation. The reaction outcome, viz. the formation of aldehydes versus isomerization, depends strongly on the presence and concentration of a phosphine co-catalyst. Thus, while 1a gave only a 17% yield of aldehyde in the absence of phosphines, the yield is increased to 54% in the presence of phosphinated silica P-{SiO₂} or even 94% if PPh₃ is added to the solution. Without extra added phosphine, both 1a and 2a effect mainly the isomerization of 1-hexene to 2-hexene. Pre-catalyst 1a catalyzes also the hydrogenation of benzene at 10.5 atm H₂ and 90 °C to give cyclohexane with a TOF of 608 h⁻¹.     

Complexes of rhodium(III) and iridium(III) with the mono-oximes of 1,2-naphthoquinone: X-ray crystal structure of pyridinium trichloro(1,2-naphthoquinone 1-oximato)(pyridine)iridate(III)

The complexes M(1-nqo)₃ (M = Rh or Ir, 1-nqoH = 1,2-naphthoquinone 1-oxime) and M(2-nqo)₃ (M = Rh or Ir, 2-nqoH = 1,2-naphthoquinone 2-oxime) were prepared by the interaction of the quinone oxime with hydrated rhodium(III) chloride or chloroiridic(III) acid. The mixture resulting from the reaction of chloroiridic(III) acid and 1,2-naphthoquinone 1-oxime on treatment with pyridine afforded [pyH][Ir(1-nqo) (py)Cl₃] which was characterized by X-ray crystallography. The complexes Rh(1-nqo)₃ and Rh(2-nqo)₃ were also obtained by the nitrosation of the respective naphthol in the presence of hydrated rhodium(III) chloride. None of the trischelates showed any tendency to react with pyridine, triphenylphosphine or aqueous hydrochloric acid.     

Methods for separation of trace amounts of platinum and investigation of the influence of interfering elements during platinum determination in copper ores and copper concentrates by graphite furnace atomic absorption spectrometry

A THGA graphite furnace with Zeeman background correction has been used to determine platinum content in copper ore and copper concentrate at the part per billion (ppb) concentration level. Two different procedures for the separation of trace platinum have been applied: (i) use of an ion exchange resin; and (ii) a two-stage method based on platinum separation on inorganic carriers. The influence of interfering elements in the matrix (Cu, Pb, Fe, Ti, V, Au, Pd, Ir, Rh and Al) has been examined using a graphite furnace. It was found that the presence of Cu (12.5–100 mg l⁻¹), Pb (100–500 mg l⁻¹), Fe (100–2000 mg l⁻¹), Ti (25–100 mg l⁻¹), V (25–100 mg l⁻¹), Au (25–300 mg l⁻¹), Pd (20–250 mg l⁻¹), Ir (0.5–3.5 mg l⁻¹) and Rh (0.025–1 mg l⁻¹) in the samples analyzed has no effect on the platinum absorption signal when using a recommended temperature program (T_pyr=1300°C, T_at=2450°C). Spectral interference was observed, which was due to aluminum, as a result of the close neighborhood of the Pt 265.945-nm and Al 266.039-nm lines. This interference could not be eliminated by the Zeeman background correction.     

Synthesis, structure, and reactivity of rhodium and iridium complexes of the chelating bis-sulfoxide tBuSOC2H4SOtBu. Selective O-H activation of 2-hydroxy-isopropyl-pyridine

The chloro-bridged rhodium and iridium complexes [M2(BTSE)2Cl2] (M = Rh 1, Ir 2) bearing the chelating bis-sulfoxide tBuSOC2H4SOtBu (BTSE) were prepared by the reaction of [M2(COE)4Cl2] (M = Rh, Ir; COE = cyclooctene) with an excess of a racemic mixture of the ligand. The cationic compounds [M(BTSE)2][PF6] (M = Rh 3, Ir 4), bearing one S- and one O-bonded sulfoxide, were also obtained in good yields. The chloro-bridges in 2 can be cleaved with 2-methyl-6-pyridinemethanol and 2-aminomethyl pyridine, resulting in the iridium(I) complexes [Ir(BTSE)(Py)(Cl)] (Py = 2-methyl-6-pyridinemethanol 5, 2-aminomethyl-pyridine 6). In case of the bulky 2-hydroxy- isopropyl-pyridine, selective OH oxidative addition took place, forming the Ir(III)-hydride [Ir(BTSE)(2-isopropoxy-pyridine)(H)(Cl)] 7, with no competition from the six properly oriented C-H bonds. The cationic rhodium(I) and iridium(I) compounds [M(BTSE)(2-aminomethyl-pyridine)][X] (M = Rh 8, Ir 10), [Rh(BTSE)(2-hydroxy- isopropyl-pyridine)][X] 9(stabilized by intramolecular hydrogen bonding), [Ir(BTSE)(pyridine)2][PF6] 12, [Ir(BTSE)(alpha-picoline)2][PF6] 13, and [Rh(BTSE)(1,10-phenanthroline)][PF6] 14 were prepared either by chloride abstraction from the dimeric precursors or by replacement of the labile oxygen bonded sulfoxide in 3 or 4. Complex 14 exhibits a dimeric structure in the solid state by pi-pi stacking of the phenanthroline ligands.     

Kinetics and mechanisms of homogeneous catalytic reactions: Part 7. Hydroformylation of 1-hexene catalyzed by cationic complexes of rhodium and iridium containing PPh3

Cationic rhodium and iridium complexes of the type [M(COD)(PPh₃)₂]PF₆ (M = Rh, 1a; Ir, 1b) are efficient precatalysts for the hydroformylation of 1-hexene to its corresponding aldehydes (heptanal and 2-methylhexanal), under mild pressures (2–5 bar) and temperatures (60 °C for Rh and 100 °C for Ir) in toluene solution; the linear to branched ratio (l/b) of the aldehydes in the hydroformylation reaction varies slightly (between 3.0 and 3.7 for Rh and close to 2 for Ir). Kinetic and mechanistic studies have been carried out using these cationic complexes as catalyst precursors. For both complexes, the reaction proceeds according to the rate law r_i = K₁K₂K₃k₄[M][olef][H₂][CO]/([CO]² + K₁[H₂][CO] + K₁K₂K₃[olef][H₂]). Both complexes react rapidly with CO to produce the corresponding tricarbonyl species [M(CO)₃(PPh₃)₂]PF₆, M = Rh, 2a; Ir, 2b, and with syn-gas to yield [MH₂(CO)₂(PPh₃)₂]PF₆, M = Rh, 3a; Ir, 3b, which originate by CO dissociation the species [MH₂(CO)(PPh₃)₂]PF₆ entering the corresponding catalytic cycle. All the experimental data are consistent with a general mechanism in which the transfer of the hydride to a coordinated olefin promoted by an entering CO molecule is the rate-determining step of the catalytic cycle.     

两种基于氮杂环结构铱(Ⅲ)配合物的合成及有机电致发光性能

以苯基嘧啶/吡啶基嘧啶为母核, 同时引入2个三氟甲基(CF₃)合成了2-[3,5-二（三氟甲基）苯基]-5-氟基嘧啶(tfmphfppm)和2-[2,6-二（三氟甲基）-4-吡啶基]-5-氟基嘧啶(tfmpyfppm)主配体, 并以2-(5-苯基-1,3,4-噁二唑-2-)苯酚(pop)为辅助配体合成了2种铱(III)配合物Ir(tfmphfppm)₂(pop)和Ir(tfmpyfppm)₂(pop), 其发射光谱峰分别位于484和504 nm, 分别属于蓝绿光和绿光发射, 发光量子效率分别达到76%和89%. 由于氮杂环和2,5-二苯基-1,3,4-噁二唑基团的存在, 配合物具有较低的最低未占据分子轨道(LUMO)能级和较高的电子迁移率. 以2种 铱(III)配合物为发光中心制备的有机电致发光器件(OLED)显示了较好的器件性能, 其最大亮度(L_max)、 最大电流效率(η_{c, max})、 最大功率效率(η_{p, max})和最大外量子效率(EQE_max)分别为33379 cd/m², 76.55 cd/A, 31.59 lm/W和26.7%; 并且该器件显示了比较小的效率滚降, 在亮度为1000 cd/m²时, 器件的η_c仍然可以达到72.71 cd/A. 本文结果表明, 氮杂环、 2,5-二苯基-1,3,4-噁二唑和三氟甲基基团可以有效提高铱(Ⅲ)配合物的发光性能和电子迁移率, 从而提高器件的性能.