Reactions of the cationic diruthenium carbonyl complex [Ru2(μ-dppm)2(CO)4(μ,η-O2CMe)] with bidentate ligands; intramolecularly assisted stereospecific synthesis via the second-sphere face-to-face π–π stacking interactions

The reactions of the diruthenium carbonyl complexes [Ru₂(μ-dppm)₂(CO)₄(μ,η²-O₂CMe)]X (X=BF₄⁻ (1a) or PF₆⁻ (1b)) with neutral or anionic bidentate ligands (L,L) afford a series of the diruthenium bridging carbonyl complexes [Ru₂(μ-dppm)₂(μ-CO)₂(η²-(L,L))₂]X_n ((L,L)=acetate (O₂CMe), 2,2′-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n=0, 1, 2). Apparently with coordination of the bidentate ligands, the bound acetate ligand of [Ru₂(μ-dppm)₂(CO)₄(μ,η²-O₂CMe)]⁺ either migrates within the same complex or into a different one, or is simply replaced. The reaction of [Ru₂(μ-dppm)₂(CO)₄(μ,η²-O₂CMe)]⁺ (1) with 2,2′-bipyridine produces [Ru₂(μ-dppm)₂(μ-CO)₂(η²-O₂CMe)₂] (2), [Ru₂(μ-dppm)₂(μ-CO)₂(η²-O₂CMe)(η²-bpy)]⁺ (3), and [Ru₂(μ-dppm)₂(μ-CO)₂(η²-bpy)₂]²⁺ (4). Alternatively compound 2 can be prepared from the reaction of 1a with MeCO₂H–Et₃N, while compound 4 can be obtained from the reaction of 3 with bpy. The reaction of 1b with acetylacetone–Et₃N produces [Ru₂(μ-dppm)₂(μ-CO)₂(η²-O₂CMe)(η²-acac)] (5) and [Ru₂(μ-dppm)₂(μ-CO)₂(η²-acac)₂] (6). Compound 2 can also react with acetylacetone–Et₃N to produce 6. Surprisingly [Ru₂(μ-dppm)₂(μ-CO)₂(η²-quin)₂] (7) was obtained stereospecifically as the only one product from the reaction of 1b with 8-quinolinol–Et₃N. The structure of 7 has been established by X-ray crystallography and found to adopt a cis geometry. Further, the stereospecific reaction is probably caused by the second-sphere π–π face-to-face stacking interactions between the phenyl rings of dppm and the electron-deficient six-membered ring moiety of the bound quinolinate (i.e. the N-included six-membered ring) in 7. The presence of such interactions is indeed supported by an observed charge-transfer band in a UV–vis spectrum.     

Formation, solution structure and reactivity of alkylperoxo complexes of titanium

A detailed in situ ¹³C and ¹H NMR spectroscopic characterization of the following families of alkylperoxo complexes of titanium is presented: Ti(η²-OOtBu)_n(OiPr)_4−n, where n = 1–4; binuclear complexes [(iPrO)₃Ti(μ-OiPr)₂Ti(OiPr)₂(η²-OOtBu)] and [(η²-OOtBu)(iPrO)₂Ti(μ-OiPr)₂Ti(OiPr)₂(η²-OOtBu)]; complexes with β-diketonato ligands: Ti(LL)₂(OEt)(η²-OOtBu), Ti(LL)₂(OiPr)(η²-OOtBu), Ti(LL)₂(η²-OOtBu)₂, Ti(LL)₂(OtBu)(η¹-OOtBu), where HLL = acetylacetone, dipivaloylmethane. These alkylperoxo complexes could not be isolated due to their instability and were studied in situ at low temperatures. Whereas the side-on (η²) coordination mode of tert-butylperoxo ligand is generally preferable, the end-on (η¹) coordination caused by spatial hindrance from surrounding bulky ligands is found in two cases. The quantitative data on the reactivity of alkylperoxo complexes found towards sulfides and alkenes were obtained. The system TiO(acac)₂/tBuOOH in C₆H₆ was reinvestigated using ¹³C and ¹H NMR spectroscopy. The structure of the complex Ti(acac)₂{CH₃C(O)(OOtBu)COO} actually formed in this system was elucidated. Four types of titanium(IV) alkylperoxo complexes were detected in the Sharpless–Katsuki catalytic system using ¹³C NMR spectroscopy.     

Fraction of excited-state oxygen formed as b Σg in solution-phase-photosensitized reactions II. Effects of sensitizer substituent

The fraction F_Σ of excited-state oxygen formed as b ¹Σ_g⁺ was determined for a series of triplet-state photosensitizers in CCl₄ solutions. F_Σ was determined by monitoring the intensities of (a) O₂(b ¹Σ_g⁺) fluorescence at 1926 nm (O₂(b ¹Σ_g⁺)→O₂(a ¹Δ_g) and (b) O₂(a ¹ Δ_g) phosphorescence at 1270 nm (O₂(a ¹Δ_g) → O₂(X³Σ_g⁻)). Oxygen excited states were formed by energy transfer from substituted benzophenones and acetophenones. The data indicate that F_Σ depends on several variables including the orbital configuration of the lowest triplet state and the triplet-state energy. The available data indicate that the sensitizer-oxygen charge transfer (CT) state is not likely to influence F_Σ strongly by CT-mediated mixing of various sensitizer-oxygen states.     

Synthesis and characterization of hydroxo, pyrazolato and carboxylato derivatives of the PdR(PPh3)moiety (R = C6F5 or C6Cl5)

The hydroxo-complexes [{PdR(PPh₃)(μ-OH)}₂] (R = C₆F₅ or C₆Cl₅) have been obtained by reaction of the corresponding [{PdR(PPh₃)(μ-Cl)}2] complexes with NBu₄OH in acetone. In this solvent, the reaction of the hydroxo-bridged complexes with pyrazole (Hpz) and 3,5-dimethylpyrazole (Hdmpz) in 1:2 molar ratio leads to the formation of the new complexes [{Pd(C₅F₅)(PPh₃)(μ-azolate)}2] and [{Pd(C₆Cl₅)(PPh₃)}₂(μ-OH)(μ-azolate)] (azolate = pz or dmpz). The reaction of the bis(μ-hydroxo) complexes with Hpz and Hdmpz in acetone in 1:1 molar ratio has also been studied, and the resulting product depends on the organic radical (C₆F₅ or C₆Cl₅) as well as the azolate (pz or dmpz). The identity of the isomer obtained has been established in every case by NMR (¹H, ¹⁹F and ³¹P) spectroscopy. The reaction of the bis(μ-hydroxo) complexes with oxalic (H₂Ox) and acetic (HOAc) acids yields the binucle ar complexes [{PdR(PPh₃)}2(μ-Ox)] (R = C₆F₅ or C₆Cl₅) and [{Pd(C₆F₅)(PPh₃)(μ-OAc)}2], respectively. [{Pd(C₆F₅)(PPh₃)(μ-OH)}₂] reacts with PPh₃ in acetone in 1:2 ratio giving the mononuclear complex trans-[Pd(C₆F₅) (OH)(PPh₃)₂], whereas the pentachlorophenylhydroxo complex does not react with PPh₃, even under forcing conditions.     

Organometallic complexes for nonlinear optics: Part 32: Synthesis, optical spectroscopy and theoretical studies of some osmium alkynyl complexes

The complexes trans-[Os(CCPh)Cl(dppe)₂] (1), trans-[Os(4-CCC₆H₄CCPh)Cl(dppe)₂] (2), and 1,3,5-{trans-[OsCl(dppe)₂(4-CCC₆H₄CC)]}₃C₆H₃ (3) have been prepared. Cyclic voltammetric studies reveal a quasi-reversible oxidation process for each complex at 0.36–0.39 V (with respect to the ferrocene/ferrocenium couple at 0.56 V), assigned to the Os^II/III couple. In situ oxidation of 1–3 using an optically transparent thin-layer electrochemical (OTTLE) cell affords the UV–Vis–NIR spectra of the corresponding cationic complexes 1⁺–3⁺; a low-energy band is observed in the near-IR region (11 000–14 000 cm⁻¹) in each case, in contrast to the neutral complexes 1–3 which are optically transparent below 20 000 cm⁻¹. Density functional theory calculations on the model compounds trans-[Os(CCPh)Cl(PH₃)₄] and trans-[Os(4-CCC₆H₄CCPh)Cl(PH₃)₄] have been used to rationalize the observed optical spectra and suggest that the low-energy bands in the spectra of the cationic complexes can be assigned to transitions involving orbitals delocalized over the metal, chloro and alkynyl ligands. These intense bands have potential utility in switching nonlinear optical response, of interest in optical technology.     

Reactions of metalloalkynes VII. Protonation of ruthenium ethyne-1,2-diyl complexes

The acid–base chemistry of some ruthenium ethyne-1,2-diyl complexes, [{Ru(CO)₂(η-C₅H₄R)}₂(μ₂-CC)] (R=H, Me) has been investigated. Initial protonation of [{Ru(CO)₂{η-C₅H₄R}}₂(μ₂-CC)] gave the unexpected complex cation, crystallised as the BF₄ salt, [{Ru(CO)₂(η-C₅H₄R}}₃(μ₃-CC)][BF₄] (R=Me structurally characterised). This synthesis proved to be unreliable but subsequent, careful protonation experiments gave excellent yields of the protonated ethyne-1,2-diyl complexes, [{Ru(CO)₂{η-C₅H₄R)}₂(μ₂-η¹:η²-CCH)](BF₄) (R=Me structurally characterised) which could be deprotonated in high yield to return the starting ethyne-1,2-diyl complexes.     

H2O2-based epoxidation of bridged cyclic alkenes with [P{Ti(O2)}2W10O38] in monophasic systems: active site and kinetics

The H₂O₂-based epoxidation of bridged cyclic alkenes in a monophasic system containing low concentrations (<2 mM) of [Bu₄ⁿN]₄[Pr₂ⁱNH₃]₂H[P{Ti(O₂)}₂W₁₀O₃₈]·H₂O (1) (with two η²-peroxotitanium sites in the anion) has been studied in search of the catalytically active species involved. ³¹P NMR spectra of 1, measured under a variety of conditions, revealed that the active species was not hydroperoxotitanium complex [P{Ti(OOH)}₂W₁₀O₃₈]⁷⁻or [P{Ti(OOH)}Ti(O₂)W₁₀O₃₈]⁷⁻. The reaction pathways for the alkene epoxidation are discussed to understand the kinetics (especially the initial [H₂O₂] dependence). It was concluded that the net catalytic reaction for the epoxidation occurred through the two-electron oxidation at the hydroperoxotitanium site in the catalyst.     

Highly stereoselective reduction of methyl ketone complexes of the chiral Lewis acid [(η-C5H5)Re(NO)(PPh3)] by K(s-C4H9)3BH; synthesis of optically active secondary alcohols and derivatives

Reaction of optically active ketone complexes (+)-(R)-[(η⁵-C₅H₅)Re(NO)-(PPh₃)(η¹-O=C(R)(CH₃)]⁺ BF₄⁻ (R = CH₂CH₃, CH(CH₃)₂m C(CH₃)₃, C₆H₅) with K(s-C₄H₉)₃BH gives alkoxide complexes (+)-(RS)-(η⁵-C₅H₅)Re(NO)(PPh₃)-(OCH(R)CH₃) (73–90%) in 80–98% de. The alkoxide ligand is then converted to Mosher esters (93–99%) of 79–98% de.     

A spectroscopic study on the reaction-controlled phase transfer catalyst in the epoxidation of cyclohexene

The epoxidation of cyclohexene with hydrogen peroxide in a biphase medium (H₂O/CHCl₃) was carried out with the reaction-controlled phase transfer catalyst composed of quaternary ammonium heteropolyoxotungstates [π-C₅H₅N(CH₂)₁₅CH₃]₃[PW₄O₁₆]. A conversion of about 90% and a selectivity of over 90% were obtained for epoxidation of cyclohexene on the catalyst. The fresh catalyst, the catalyst under reaction conditions and the used catalysts were characterized by FT-IR, Raman and ³¹P NMR spectroscopy. It appears that the insoluble catalyst could degrade into smaller species, [(PO₄){WO(O₂)₂}₄]³⁻, [(PO₄){WO(O₂)₂}₂{WO(O₂)₂(H₂O)}]³⁻, and [(PO₃(OH)){WO(O₂)₂}₂]²⁻ after the reaction with hydrogen peroxide and becomes soluble in the CHCl₃ solvent. The active oxygen in the [W₂O₂(O₂)₄] structure unit of these soluble species reacts with olefins to form the epoxides and consequently the corresponding W---Ob---W (corner-sharing) and W---Oc---W (edge-sharing) bonds are formed. The peroxo group [W₂O₂(O₂)₄] can be regenerated when the W---Ob---W and W---Oc---W bonds react with hydrogen peroxide again. These soluble species lose active oxygen and then polymerize into larger compounds with the W---Ob---W and W---Oc---W bonds and then precipitate from the reaction solution after the hydrogen peroxide is consumed up. Part of the used catalyst seems to form more stable compounds with Keggin structure under the reaction conditions.     

Infrared laser magnetic resonance spectroscopy of OD at 118.8, 96.5 and 215.4μ m

Zeeman spectral data are presented for the ²Π_3/2: J = _7/2 → J= _9/2,²Π_3/2: J= _7/2→²Π_1/2:J= _5/2 and²Π_3/2 J= _3/2→ J = _5/2 transitions in OD. Data for the ²Π_3/2. J=3/2→ J= 5/2 and ²Π_3/2 J= _5/2 → ²Π_l/2 : J= _3/2 transitions in OH, taken under similar conditions, are included.     

具有螺旋结构的金属镍有机-无机配位聚合物的合成及表征

在水热体系中合成了3个中心金属为镍离子, 以六配位扭曲八面体构型形成的具有螺旋结构的配位聚合物{[Ni₂L₂(bib)₂·2H₂O]·5H₂O}_n(1), [Ni₂L₂(bpy)]_n(2)和{[Ni₂L₂(bibpip)₂·2H₂O]·6H₂O}_n(3)[H₂L=4,4'-三苯胺二甲酸; bib=1,3-二(咪唑基)苯; bpy=4,4-联吡啶; bibpip=1,4-二(4-咪唑苄基)哌嗪]. 通过单晶及粉末X射线衍射、 红外光谱、 元素分析和热重分析对这3种化合物进行了表征. 结果表明, 化合物1属于单斜晶系, C2/c空间群, 其骨架为具有{4²·6⁵·8}拓扑结构的二维层结构; 化合物2属于斜方晶系, Fdd2空间群, 其骨架为具有{4⁸·5⁴·6³}拓扑结构的三维超分子网络; 化合物3属于三斜晶系, P\begin{array}{c}\bar{1}\end{array}空间群, 为1个五重穿插的三维超分子网络, 其骨架具有{4⁴·6²}拓扑结构.     

The vibrational state distributions in both products of the reaction: O(P) + NO2 → O2 + NO

A laser pulse-and-probe method has been used to determine the nascent vibrational populations in NO(v=0–4) and O₂(v=6–11) formed in the thermal reaction: O(³P) + NO₂ → O₂(v) + NO(v). A frequency-tripled Nd: YAG laser is used to photolyse NO₂, diluted tenfold in Ar, and laser-induced fluorescence spectroscopy in the NO A ²Σ⁺-X ²Π and O₂ B ³Σ⁻_u -X ³Σ⁻_g electronic band system is used both to follow the kinetics of individual vibrational states and to determine the nascent vibrational distributions. The majority of the NO product is formed in v = 0 and the average vibrational yield is ≈ 4.6%. The O₂ populations fall monotonically from v = 6 to 11 in a distribution close to what is expected on prior grounds. Based on a surprisal analysis, the average vibrational energy yield in O₂ is ≈ 26%. The nature of the reaction dynamics is discussed.     

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.     

Intermolecular propargyl/allenyl group transfer from Pd(II) to Pt(0) and Pt(II) to Pd(0). Key reaction in metal-catalyzed isomerization between propargyl and allenyl metal complexes

Isomerization of phenyl-substituted propargylplatinum(II) complex, trans-Pt(CH₂CCPh)(Cl)(PPh₃)₂ (1) to allenyl complex, trans-Pt(CPh=C=CH₂)(Cl)(PPh₃)₂ (2) was found to be catalyzed by zerovalent complex Pd(PPh₃)₄. The reaction was proposed to proceed through the transfer of the propargyl/allenyl ligand both from Pt(II) to Pd(0) and Pd(II) to Pt(0). The former transfer, which seemingly has a thermodynamic disadvantage, has unambiguously been confirmed to take place; treatment of 1 with Pd(PPh₃)₄ or a mixture of Pd₂(dba)₃ and PPh₃ resulted in the formation of Pd(I) complex, Pd₂(μ-PhCCCH₂)(μ-Cl)(PPh₃)₂ which lies in equilibrium with a mixture of propargyl/allenylpalladium(II) and Pd(0) complexes.     

The chemical production of electronically excited states in the H/NF2 system

A mixture of NF₃ and Ar is passed through an rf discharge in a flow-system to produce, among other species, F and NF₂. When H₂, D₂, or CH₄ are added downstream, reactions with F atoms produce vibrationally excited HF or DF together with H, D, or CH₃. The latter free radicals can react with NF₂, probably by an elimination reaction to produce electronically excited NF: NF₂(²B₁) + H(D, CH₃) → HF^*(DF^* + NF(a¹Δ). A vibrational-to-electronic energy transfer process between the products of this reaction then produces the next higher state of NF: HF(ν 2) + NF(a¹Δ) → HF(ν−2) + NF(b¹Σ⁺). A similar transfer process has also been found between the electronically excited a¹Δ states of O₂ and NF: O₂(a¹Δ) + NF(a¹Δ) → O₂(X³Σ⁻) + NF(b¹Σ⁺). The H or D atoms but not the CH₃ radicals are then found to react with either NF(a¹Δ) or NF(X³Σ⁻) to produce electronically excited N(₂D) atoms, which in turn react with the NF(a¹Δ) molecules to produce N₂(B³Π_g). The observed nitrogen first positive radiation has been demonstrated to be produced entirely by this reaction mechanism rather than by the N(⁴S) recombination that accounts for the Rayleigh afterglow. In addition, the occurrence of the reaction N(₂D) + N₂O → NO(B²Π_r) + N₂ (X¹Σ⁺_g) has been verified. Finally we have observed emission at 3344 Å, which we attribute to the NF(A³Π), which has not been previously reported.     

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 chemistry of peroxovanadium species in aqueous solutions. Structure and reactivity of a neutral diperoxovanadium complex as provided by V-NMR data, ab initio calculations and kinetic results

The addition of hydrogen peroxide to vanadium (V) precursors in aqueous acidic solutions leads to the formation of a cationic monoperoxospecies [VO(O₂)]⁺ and an anionic diperoxocomplex [VO(O₂)₂]⁻, depending on the pH and on the excess of H₂O₂. The latter may undergo protonation to form the neutral complex [HVO(O₂)₂]. ⁵¹V-NMR data and ab initio calculations suggest that the neutral complex is formed via protonation of a peroxide oxygen and that in such a species, as well as in the other two peroxovanadium derivatives, the usual η² arrangement of the peroxo groups is maintained. The comparison of reactivity data of the three complexes in the self-decomposition reaction and in the oxidation of uracil, indicates that the neutral diperoxocomplex exhibits an oxidizing power considerably larger than that of the other two peroxovanadium species.     

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.     

Reactivity studies of [Pd2(μ-X)2(PBu3)2] (X = Br, I) with CNR (R = 2,6-dimethylphenyl), H2 and alkynes

Improved syntheses for the dimeric compounds [Pd₂(μ-X)₂(PBu^t₃)₂] (X = Br, I) have been developed and the X-ray crystal structure for the dimer with X = 1 is reported. The reactions of these dimers with CNR (R = 2,6-dimethylphenyl), H₂ and a series of terminal and substituted alkynes are also reported. The dimer with X = Br is an initiator for the catalytic polymerisation of phenylacetylene. The product of the dimers with disubstituted alkynes results in the synthesis of trimeric species with formula [Pd₃(μ-X){ν²-C₄(CO₂R)₄}₂][PBu^t₃)Me]₂ (X = Br, I; R = Me, Et). The X-ray crystal structure of one of these compounds (when R = Et and X = I) is presented, demonstrating that the palladium dimers assist the C---C coupling of the alkynes.     

Palladium(II) coordination and cyclometallated complexes derived from 1-tert-butylpyrazole

The synthesis and characterization of a number of new coordination compounds of Pd^II with the nitrogen donor 1-tert-butylpyrazole (^tBuPzH) are described. Compounds are trans-[Pd(^tBuPzH)₂Cl₂] and the cyclometallated structures [Pd₂(^tBuPz)₂(AcO)₂] and [Pd₃(^tBuPz)₂(AcO)₄]. All these complexes are mixtures of syn and anti isomers. Also, the chloro-bridged complex [Pd₂(^tBuPz)₂Cl₂] has been isolated as an equilibrium mixture of cis and trans isomers. The compounds have been studied by variable temperature ¹H- and ¹³C-NMR spectroscopy.