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Mechanistic studies on dinuclear complexes that can activate CO2 are rare. Based on the investigations done for the mononuclear compound (bpy)Re(CO)3Cl (bpy-Re, with bpy = 2,2′-bipyridine), many re...

Tetramercaptotetrathiacalix[4]arene (LH4) can be used as a coordination platform to bind four CuI ions at the thiolate and thioether S atoms. Donor ligands such as phosphanes can stabilize the resulting [LCu4] units, which then remain monomeric ([(Ph3PCu)4L]). In the absence of donor ligands, they aggregate, providing a hexamer ([LCu4]6) in high yields, with a hollow‐sphere structure formed by an unprecedented Cu24S48 cage that is surrounded by the organic framework of the calixarene chalices. Preliminary NMR experiments with regard to the host‐guest chemistry in solution showed that the compound represents a polytopic host for acetonitrile and methane., A cluster with a CuI 24 S48 nanocage can be accessed in high yields using mercaptothiacalixarenes as directing ligands. The structure contains 12 Cu2S2 diamond core building blocks featuring exceptionally short Cu⋅⋅⋅Cu distances. Detailed NMR spectroscopic investigations revealed, for instance, that it can host small molecules like acetonitrile and methane.

In soluble methane monooxygenase enzymes (sMMO), dioxygen (O2) is activated at a diiron(II) center to form an oxodiiron(IV) intermediate Q that performs the challenging oxidation of methane to meth...

In recent years, it has become clear that the presence of redox-inactive Lewis acidic metal ions can decisively influence the reactivity of metal-dioxygen moieties that are formed in the course of O2 activation, in molecular complexes, and metalloenzymes. Superoxide species are often formed as the primary intermediates but they are mostly too unstable for a thorough investigation. We report here a series of chromium(III) superoxide complexes [L2 Cr]M2 O2 (THF)y (L=- OSiPh2 OSiPh2 O- , M+ =Li+ , Na+ , K+ and y=4, 5), which could be accessed, studied spectroscopically and partly crystallized at low temperatures. They only differ in the two incorporated Lewis acidic alkali metal counterions (M+ ) and it could thus be shown that the nature of M+ determines considerably its interaction with the superoxide ligand. This interaction, in turn, has a significant influence on the stability and reactivity of these complexes towards substrates with OH groups. Furthermore, we show that stability and reactivity are also highly solvent dependent (THF versus nitriles), as donor solvents coordinate to the alkali metal ions and thus also influence their interaction with the superoxide moiety. Altogether, these results provide a comprehensive and detailed picture concerning the correlation between spectroscopic properties, structure, and behavior of such superoxides, that may be exemplary for other systems.

The hetero-Pacman architecture places two different metal coordination sites in close proximity, which can support efficient energy and/or electron transfer and allow for cooperative activation of small molecules. Herein, we present the synthesis of dyads consisting of a porphyrin unit as photosensitizer and a rhenium unit as catalytically active site, which are held together by the rigid xanthene backbone. Mononuclear [(NN)Re(CO)3(Cl)] complexes for CO2 reduction where NN represents a bidentate diimine ligand (e.g. bipyridine or phenanthroline) lack light absorption in the visible region, resulting in poor photocatalysis upon illumination with visible light. In order to improve their visible light absorption, we have focused on the incorporation of a strongly absorbing free base or zinc porphyrin unit. Resulting photocatalytic experiments showed a strong dependence of catalytic performance on both the type of photosensitizer and also the excitation wavelengths. Most notably, the intramolecular hetero-Pacman system containing a zinc porphyrin unit showed much better catalytic activity in the visible region (excitation wavelengths >450 nm) than the free base version, the corresponding mononuclear rhenium compound or an intermolecular system comprised of a 1:1 mixture of the mononuclear analogues.

Two new examples of cyanido-bridged {FeIIILnIII}2 molecular squares, with pyim and PPh3O as capping ligands at the LnIII sites, exhibit weak antiferromagnetic interactions [Ln = Eu (1), Sm (2), pyim = 2-(1H-imidazol-2-yl)pyridine, PPh3PO = triphenylphosphine oxide].

Even though aluminas and aluminosilicates have found widespread application, a consistent molecular understanding of their surface heterogeneity and the behavior of defects resulting from hydroxylation/dehydroxylation remains unclear. Here, we study the well-defined molecular model compound, [Al3 (μ2 -OH)3 (THF)3 (PhSi(OSiPh2 O)3 )2 ], 1, to gain insight into the acid-base reactivity of cyclic trinuclear Al3 (μ2 -OH)3 moieties at the atomic level. We find that, like zeolites, they are sufficiently acidic to catalyze the isomerization of olefins. DFT and gas phase vibrational spectroscopy on solvent-free and deprotonated 1 show that the six-membered ring structure of its Al3 (μ2 -OH)3 core is unstable with respect to deprotonation of one of its hydroxy groups and rearranges into two edge-sharing four-membered rings. This renders AlIV -O(H)-AlIV units strong acid sites, and all results together suggest that their acidity is similar to that of zeolitic SiIV -O(H)-AlIV groups.

The assembly of heterometallic complexes capable of activating dioxygen is synthetically challenging. Here, we report two different approaches for the preparation of heterometallic superoxide complexes [

In soluble methane monooxygenase enzymes (

Reduced CO2 species are key intermediates in a variety of natural and synthetic processes. In the majority of systems, however, they elude isolation or characterisation owing to high reactivity or limited accessibility (heterogeneous systems), and their formulations thus often remain uncertain or are based on calculations only. We herein report on a Ni-CO22- complex that is unique in many ways. While its structural and electronic features help understand the CO2 -bound state in Ni,Fe carbon monoxide dehydrogenases, its reactivity sheds light on how CO2 can be converted into CO/CO32- by nickel complexes. In addition, the complex was generated by a rare example of formate β-deprotonation, a mechanistic step relevant to the nickel-catalysed conversion of Hx COyz- at electrodes and formate oxidation in formate dehydrogenases.

The complex trans-[Pt(F)(SF3 )(PCy3 )2 ] (1) shows a diverse reactivity pattern at the SF3 ligand towards ethanol and Me3 SiOEt. This led by deoxyfluorination or alcoholysis to the generation of platinum complexes bearing a metal-bound S(O)F or S(OEt)2 group. For the latter reaction trans-[Pt(F){S(F)(OEt)2 }(PCy3 )2 ] is suggested as an intermediate. In reactivity studies of trans-[Pt(F)(SF2 )(PCy3 )2 ][BF4 ] the complex [Pt(F){S(F)(OEt)}(PCy3 )2 ][BF4 ] was prepared, which does not react with ethanol.

As a rather inert gas, sulfur hexafluoride is still used as a dielectric in high-voltage power applications despite its high global warming potential. Its activation at transition metal complexes has been reported, but the fate of the sulfur-containing products is often unknown. The activation of SF6 at [Rh(H){tBuxanPOP}] (tBuxanPOP = 9,9-dimethyl-4,5-bis(ditert-butylphosphino)xanthene) at room temperature leads to the generation of the bifluorido complex [Rh(FHF){tBuxanPOP}]. A subsequent regeneration of [Rh(H){tBuxanPOP}] completes a cyclic process for the degradation of SF6. Furthermore, the SF6 activation at [Rh(H){tBuxanPOP}] in the presence of triethylsilane as a hydrogen source is described, which leads to the formation of the fluorido complex [Rh(F)2(H){tBuxanPOP}] as well as [Rh(SH){tBuxanPOP}] and S(SiEt3)2 as sulfur-containing products.

The synthesis of the ligand systems L1 and L2 with two different N3-binding sites linked through a dibenzofuran spacer and their coordination properties towards a variety of CuI precursors are reported. The reaction of L1 with copper halides leads to the formation of a bimetallic species [(L1)(CuICl)2] (1), and metallodimers [((L1)(CuIX)2)2(μ-(CuI2)(μ-X)2)] (2: X = Br, 3: X = I) in which two dicopper complexes are bridged by a (μ-(CuI2)(μ-X)2)-moiety whereas L2 reacts with copper chloride to afford {[CuI2(L2)Cl2]}n (8). Furthermore, starting from L1 in combination with copper(I) salts of weakly coordinating anions the dicopper complexes [(L1)(CuI(NCCH3))2](BF4)2 (4), [(L1)(CuI(NCCH3))(Cu(Y))](Y) (5: Y = OTf, 6: Y = ClO4) and [(L1)(CuI2(dppe))](PF6)2 (7) were isolated, and employing L2, the complexes [(L2)(CuI(NCCH3))2](Z)2 (9: Z = PF6, 10: Z = OTf) and [(L2)(CuI2(dppe))](PF6)2 (11) were obtained. Complexes 4–6 as well as 9 and 10 react rapidly with O2 to form metastable O2 adducts in acetone at −90 °C, where O2 is bound between the two copper centers within one dicopper molecule, as evidenced by UV/Vis spectroscopy, kinetic investigations, Raman spectroscopy and studies with ligands containing the isolated donor sites. The reactivity of the O2 adducts towards selected substrates was also investigated, showing their ability to act as electrophiles as well as nucleophiles.

Two novel bis(triazolyl)carbazole ligands Hbtc1 (3,6-di(tert-butyl)-1,8-bis[(1-(3,5-di(tert-butyl)phenyl)-1,2,3-triazol-4-yl)]-9H-carbazole) and Hbtc2 (3,6-di(tert-butyl)-1,8-bis[(4-(3,5-di(tert-butyl)phenyl)-1,2,3-triazol-1-yl)]-9H-carbazole), differing in the regiochemistry of triazole attachment, have been synthesized by Cu-catalyzed azide-alkyne cycloaddition, the so-called "click-reactions". Metalation with Ru, Zn, and Ni precursors led to the formation of M(btc)2 complexes (M=Ru, Zn, Ni), with two deprotonated ligands coordinating to the metal center in tridentate fashion, forming almost perfectly octahedral coordination spheres. The redox properties of M(btc)2 complexes have been investigated by cyclic voltammetry, UV/Vis spectroscopy, spectroelectrochemistry, and chemically. The CV of the ruthenium complexes revealed three quasi-reversible one-electron oxidation processes, one assigned as the RuII/III couple and two originating from ligand-based oxidations. The CVs of both Zn and Ni complexes contained only two oxidation waves corresponding to the oxidation of the two ligands. The oxidation potentials of complexes derived from Hbtc1 ligands were found to be 300-400 mV lower than those of the corresponding complexes derived from Hbtc2, reflecting the significant difference in donation through the N(2) or N(3) atom of the triazole moiety.

The synthesis of [NMe4][AuF4] and [NEt4][AuF4] as well as an improved one-pot synthesis of Cs[AuF4] is reported. The new [AuF4]- salts were structurally characterized by single crystal X-ray diffraction, NMR spectroscopy, vibrational spectroscopy and mass spectrometry. These salts are the first gold(III) fluoride salts that can be isolated in pure form and are convenient to be used in usual organic solvents for subsequent synthesis. We further report the formation of molecular AuF3 complexes in solution characterized as [F3Au(NCCH3)] at low temperature, as [F3Au(py)] and a binuclear derivative which is stable at room temperature. The stability of these species in common organic solvents was investigated and they showed a satisfying stability.

A xanthene-based bismuthane/phosphane chelating ligand has been accessed that has enabled the synthesis of a palladium(0) bismuthane complex. The bismuthane donor proved to be hemilabile as it switched to a dangling position upon addition of O2 that gave a palladium(II) peroxide complex. Unlike the corresponding 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) palladium peroxide, the bismuth analogue could be employed for catalytic phosphane oxidation and oxidative phenol coupling.

A hexanuclear iron(II) siloxide complex has been prepared by reacting an incompletely condensed silsesquioxane first with NaOMe and then with Fe(OTf)2. In the process of product formation, the siloxane framework undergoes a transformation and it was shown that this happens already upon addition of base: Treatment of the ligand precursor with NaOMe leads to a completely condensed silsesquioxane cage with 12 Si atoms that is composed of 2 equiv of the tetrasiloxide ligands found in the product complex. Its iron centers form a two-dimensional array reminiscent of the situations found in minerals and two-dimensional oxide films caused by segregation of FeOx and silica. As the hexairon(II) assembly contains two high-spin square-planar FeO4 units—suggested to represent the active sites in Fe-zeolites, which react with N2O to generate strongly oxidizing sites—it was treated with Me3NO. This led to the oxidation of two of the iron centers to the oxidation state +III and elimination of one iron ion, so that a pent...

The use of the heteroleptic [CrIII(AA)(CN)4]- complex as a ligand towards the preformed [MnII(tptz)]2+ and [MnII(pyim)2]2+ species afforded the heterometallic compounds: [MnII(tptz)(H2O)(NO3)(-NC)CrIII(ampy)(CN)3]CH3CN (1), [MnII(tptz)(H2O)(NO3)(-NC)CrIII(phen)(CN)3]H2O (2) and {[MnII(pyim)2][(-NC)Cr(phen)(CN)3]2}3H2O (3) [AA = 2-aminomethylpyridine (ampy) and 1,10-phenanthroline (phen), tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine and pyim = 2-(1H-imidazol-2-yl)pyridine]. 1 and 2 are neutral heterodinuclear complexes where a [CrIII(AA)(CN)4]- building block acts as a monodentate ligand through one cyanide group towards a seven coordinate MnII ion. Compound 3 is a neutral heterotrinuclear complex made up by two [CrIII(AA)(CN)4]- units acting as monodentate ligands through one cyanide group towards an inner [MnII(pyim)2]2+ entity, the MnII ion being six-coordinate. The magnetic properties of 1-3 were investigated in the temperature range 1.9-300 K. Overall AF behavior is observed for all three compounds, the antiparallel alignment of the local spins leading to either a ground spin triplet (1 and 2) or a spin doublet (3). The values of the magnetic coupling between the CrIII and MnII ions across the single cyanido bridges are J = -7.40(2) (1), -6.65(2) (2) and -6.41(2) and -4.65(2) cm-1 (3), the spin Hamiltonian being defined as H = -J(SCr1 SMn1) (1 and 2) and H = -J1(SCr1 SMn1) - J2(SCr2 SMn2) (3). These values could be correlated with the Mn-N-Ccyanide angle.

Reactions of platinum(0) tolane complexes, bearing a chelating ligand with P and N donor atoms, with the electrophilic fluorinating agent XeF2 give facile access to platinum(II) β-fluorovinyl fluorido complexes. A series of new platinum(II) β-fluorovinyl complexes have been synthesized and were structurally characterized. Further oxidation with XeF2 led to ortho-metalated platinum(IV) fluorido compounds. Additional reactions of platinum(0) tolane complexes, bearing a chelating P,P donor ligand, with XeF2 led to a variety of fluorido and fluorovinyl complexes.

To support mechanistic inferences made for an iron-based dioxygenase model, a nickel analogue, i.e. a TpNi-malonate (1) was prepared. 1 proved to represent a rare case of a nickel complex reacting with O2 in a controlled manner - mechanistically different from the iron case - and leads to hydroxylation of the malonate.

The isolation and identification of intermediates formed in the course of the activation of dioxygen at transition metal centers reveals important mechanistic insights concerning such processes. We previously reported the reaction of the dinuclear CrII complex [L2Cr2(MeCN)2][Li(MeCN)]2 (L=PhSi(OSiPh2O−)3) (5) with dioxygen, which resulted in the formation of the CrIV oxo complex [L2Cr2O2][Li(THF)2]2 (6), as the final room temperature stable product. Here we now report the isolation and characterization of an intermediate en route to 6, namely the dinuclear CrIII superoxo complex [L2Cr2(O2)2][Li(MeCN)]2 (7). 7 is the first example of a structurally characterized dinuclear CrIII superoxo complex with two independent side‐on bound superoxo ligands. Reactivity studies outline the capability of this superoxo complex to activate weak O−H bonds.

The reaction of the rhodium(i) complexes [Rh(E)(PEt3)3] (E = GePh3 (1), Si(OEt)3 (5)) with HFO-1234yf (2,3,3,3-tetrafluoropropene) afforded [Rh(F)(PEt3)3] (2) and the functionalized olefins Z-CF3CH[double bond, length as m-dash]CH(E) (E = GePh3 (4a), Si(OEt)3 (7)). Conceivable reaction pathways were assessed using DFT calculations. Reactions of [Rh(E)(PEt3)3] with HFO-1234ze (E-1,3,3,3-tetrafluoropropene) yielded the rhodium fluorido complex 2 and [Rh{(E)-CH[double bond, length as m-dash]CH(CF3)}(PEt3)3] (9) via two different reaction pathways. Using complexes 1 and 5 as catalysts, functionalized building blocks were obtained.

O2 activation at a chromium(II) siloxide complex in propionitrile leads to a chromium(III) complex with an end-on bound superoxide ligand, while the reaction in tetrahydrofuran leads to a side-on peroxo chromium(IV) compound. The superoxide reacts faster with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl hydroxylamine while the peroxide, unlike the superoxide, proved capable of deformylating aldehydes. The system was found to represent a unique case, where even a switching between the two structures can be achieved via the solvent; its ability to coordinate at the position trans to the O2 ligand is decisive, as supported by density functional theory studies. Altogether, the results show that subtle changes can determine for an initially formed metal-dioxygen adduct, whether it exists as a superoxide or a peroxide, which thus merits consideration in discussions on mechanisms and possible reaction routes.

Two new examples of cyanido-bridged {Fe

The hetero-Pacman architecture places two different metal coordination sites in close proximity, which can support efficient energy and/or electron transfer and allow for cooperative activation of small molecules. Here, the synthesis of dyads consisting of a porphyrin unit as photosensitizer and a rhenium unit as catalytically active site, which are held together by the rigid xanthene backbone, is presented. Mononuclear [(NN)Re(CO)

The reaction of [Fp]2 (Fp = (η5-C5H5)(CO)2Fe) with bismuth formate was shown to proceed via Fe-Bi bond formation yielding [Fp–Bi(O2CH)2]n, 1, that could be crystallized in form of two polymorphs. These differ in the way the [Fp−Bi(O2CH)2] units are connected via bridging formate ligands to yield the respective coordination polymers. The acetate derivative [Fp–Bi(O2CCH3)2] was used as a precursor compound targeting at the construction of an additional transition metal-bismuth bond: the reaction of [Fp–Bi(O2CCH3)2] with [Cp2ReH] likely yields in the envisaged complex [Fp−Bi(O2CCH3)ReCp2] first but then undergoes further transformation due to the presence of chloride and acetic acid in solution, which lead to the formation of [Fp−Bi(Cl)ReCp2], 3, and [Cp2Re–Bi(O2CCH3)2], 4, respectively. The identity of the heterotrimetallic compound 3 was established by a single-crystal X-ray diffraction analysis, while an independent synthetic route (reaction of [Cp2ReH] with [Bi(O2CCH3)3]) was developed for 4 in order to unambiguously identify 4 also as the product of the reaction between [Fp–Bi(O2CCH3)2] and [Cp2ReH].

While addition of [Cp2ReH] to [Bi(OtBu)3] leads to an equilibrium containing [Cp2Re-Bi(OtBu)2], [{Cp2Re}2Bi(OtBu)], tBuOH and [CpRe(μ-η5,η1-C5H4)Bi–ReCp2], in the presence of water [{(Cp2Re)2Bi}2O] (1) is formed selectively. Also [FpH] [Fp = (η5-C5H5)(CO)2Fe] can be employed as a precursor to form heterometallic bismuth compounds. Synthesis of [FpBi{OCH(CF3)2}2]2 (5) can be achieved by reaction of [FpH] with [Bi{OCH(CF3)2}3(thf)]2 and carboxylates [FpBi(O2CR)2]2 are generated upon treatment of [FpH] with [Bi(O2CR)3] (R = CH3, tBu). While the compounds [Fp-Bi(O2CR)2]2 can also be obtained from reactions with Fp-Fp, they are formed far more readily using [FpH] as the precursor. They typically crystallize as dimers, like the alkoxide 5. A monomeric compound of the type [Fp-BiX2] (6) could be isolated for X = thd (tetramethylheptanedionate), that is, after the reaction of [FpH] with [Bi(thd)3]. Altogether, the results demonstrate the potential of [FpH] as a precursor for [Fp-BiX2] compounds, which are formed in reactions with bismuth alkoxides, carboxylates and diketonates.

To gain molecular level insights into the properties of certain functions and units of extended oxides/hydroxides, suitable molecular model compounds are needed. As an attractive route to access such compounds the trapping of early intermediates during the hydrolysis of suitable precursor compounds with the aid of stabilizing ligands is conceivable, which was tested for the aluminum(III)/water system. Indeed, trisilanols proved suitable trapping reagents: their presence during the hydrolysis of Al(i) Bu2 H in dependence on the amount of water used allowed for the isolation of tri- and octanuclear aluminum hydroxide cluster complexes [Al3 (μ2 -OH)3 (THF)3 (PhSi(OSiPh2 O)3 )2 ] (1) and [Al8 (μ3 -OH)2 (μ2 -OH)10 (THF)3 (p-anisylSi(OSiPh2 O)3 )4 ] (2). 1 can be regarded as the Al(OH)3 cyclic trimer, where six protons have been replaced by silyl residues. While 2 features a unique [Al8 (μ3 -OH)2 (μ2 -OH)10 ](12+) core. In contrast to most other known aggregates of this type, 1 and 2 can be readily prepared at reasonable scales, dissolve in common solvents, and retain an intact framework even in the presence of excessive amounts of water. This finding paves the way to future research addressing the reactivity of the individual functional groups.

The subvalent aluminum compound [Cp*Al]4 (1) reacts with dioxygen, N2O, or sulfur to yield the heterocubane complexes [Cp*AlX]4 [X = O (2) and S (3)]. Treatment of [Cp*AlO]4 (2) with (tBuO)3SiOH gave [(tBuO)3SiOAlO]4 (6) and Cp*H. The structures and spectroscopic data of the Al clusters are supported by density functional theory (DFT) calculations, which also demonstrate the importance of noncovalent interactions (NCI) in oligomeric Al(I) complexes as well as in [Cp*AlS]4 and the heavier homologues of Se and Te. The computed (27)Al NMR shifts indicate a deshielding at the Al centers with increasing electronegativity of the chalcogen atom as well as significant spin-orbit shielding effects within the heavier heterocubane [Al4E4] cores. Further hydrolysis of 6 with an additional amount of silanol in the presence of water resulted in the formation of [Al4(OH)6(OH2)2(OSiOtBu3)6] (7), which shows a structural motif found in boehmite and diaspore.

After lithiation of PYR-H2 (PYR = [(NC(Me)C(H)C(Me)NC6H3(iPr)2)2(C5H3N)](2-)) - the precursor of an expanded β-diketiminato ligand system with two binding pockets - with KN(TMS)2 the reaction of the resulting potassium salt with FeBr2 led to a dinuclear iron(ii) bromide complex [(PYR)Fe(μ-Br)2Fe] (1). Through treatment with KHBEt3 the bromide ligands could be replaced by hydrides to yield [PYR)Fe2(μ-H)2] (2), a distorted analogue of known β-diketiminato iron hydride complexes, as evidenced by NMR, Mößbauer and X-ray absorption spectroscopy, as well as by its reactivity: for instance, 2 reacts with the proton source lutidinium triflate via protonation of the hydride ligands to form an iron(ii) product [(PYR)Fe2(OTf)2] (4), while CO2 inserts into the Fe-H bonds generating the formate complex [(PYR)Fe2(μ-HCOO)2] (5); in the presence of traces of water partial hydrolysis occurs so that [(PYR)Fe2(μ-OH)(μ-HCOO)] (6) is isolated. Altogether, the iron(ii) chemistry supported by the PYR(2-) ligand is distinctly different from the one of nickel(ii), where both, the arrangement of the two binding pockets and the additional pyridyl donor led to diverging features as compared with the corresponding system based on the parent β-diketiminato ligand.

Chemical communications : ChemComm 52(6), 1214-1217(2016). doi:10.1039/C5CC08992A, Published by Royal Society of Chemistry, Cambridge

The platinum(ii) complex [Pt(H)2(dcpe)] (; dcpe = 1,2-bis(dicyclohexylphosphino)ethane) reacts with an excess of the dialkoxymethylsilanes (HSiMe(OR)2; R = Me, Et) to give the bis(silyl) complex [Pt(SiH2Me)2(dcpe)] () and trialkoxymethylsilanes by hydrodealkoxylation reactions. These rearrangements of the silyl ligands involve Si-O bond activations. The exchange of the alkoxy moieties against silicon-bound hydrogen atoms occurs stepwise. The intermediate complexes [Pt(H){SiMe(OEt)2}(dcpe)] (), [Pt{SiMe(OEt)2}2(dcpe)] (), [Pt{SiHMe(OEt)}2(dcpe)] () and [Pt{SiHMe(OMe)}2(dcpe)] () were detected. Treatment of the complex with an excess of dichloromethylsilane yields the bis(silyl) complex [Pt(SiMeCl2)2(dcpe)] (). The hydrido silyl complex [Pt(H)(SiMeCl2)(dcpe)] () was identified as an intermediate. The reactions of the complexes [Pt(SiH3)2(dcpe)] () and [Pt(SiH2Me)2(dcpe)] () with iodomethane lead to a transfer of the SiH3 and SiH2Me ligands. Methylsilane and dimethylsilane, respectively, as well as the platinum diiodo complex [Pt(I)2(dcpe)] () were identified as main products.

Stoichiometric reactions of SF5 functionalized bromo or iodo aromatics at [Pd(PiPr3)2] (1) led to the oxidative addition products 3, 5 and 7. They were converted into their corresponding palladium fluorido complexes, which reacted readily with bis(pinacolato)diboron (B2pin2) to give the borylated SF5 aromatic compounds. Based on these studies a catalytic borylation of SF5 organyls was developed.

Molecular spin-crossover (SCO) compounds are attractive for information storage and photovoltaic technologies. We compared two prototypic SCO compounds with Fe(II)N6 (1, [Fe(phen)2(NCS)2], with phen = 1,10-phenanthroline) or Fe(III)S6 (2, [Fe(dedtc)3], with dedtc = N,N'-diethyldithiocarbamate) centers, which show abrupt (1) or gradual (2) thermally induced SCO, using K-edge X-ray absorption and Kβ emission spectroscopy (XAS/XES) in a 8-315 K temperature range, single-crystal X-ray diffraction (XRD), and density functional theory (DFT). Core-to-valence and valence-to-core electronic transitions in the XAS/XES spectra and bond lengths change from XRD provided benchmark data, verifying the adequacy of the TPSSh/TZVP DFT approach for the description of low-spin (LS) and high-spin (HS) species. Determination of the spin densities, charge distributions, bonding descriptors, and valence-level configurations, as well as similar experimental and calculated enthalpy changes (ΔH), suggested that the varying metal-ligand bonding properties and deviating electronic structures converge to similar enthalpic contributions to the free-energy change (ΔG) and thus presumably are not decisive for the differing SCO behavior of 1 and 2. Rather, SCO seems to be governed by vibrational contributions to the entropy changes (ΔS) in both complexes. Intra- and intermolecular interactions in crystals of 1 and 2 were identified by atoms-in-molecules analysis. Thermal excitation of individual dedtc ligand vibrations accompanies the gradual SCO in 2. In contrast, extensive inter- and intramolecular phen/NCS vibrational mode coupling may be an important factor in the cooperative SCO behavior of 1.

The fluorinated cyclopentadienyl complexes [Rh(η5-C5H4CH2CH2C6F13)(CO)2] (2), [Rh(η5-C5H4CH2CH2C8F17)(CO)2] (3), [Rh(η5-C5H4CH2CH2C10F21)(CO)2] (4), [Rh(η5-C5H4CH2CH2CnF2n+1)(CO)(PEt3)] (7: n = 6; 8: n = 8; 9: n = 10) and [Rh(η5-C5H4CH2CH2CnF2n+1)(CO){P(CH2CH2C6F13)3}] (10: n = 8; 11: n = 10) were synthesized and their reactivity was investigated. Compound 3 converts at room temperature into the trinuclear complex [Rh2(η5-C5H4CH2CH2C8F17)2(μ-CO)2Rh(η5-C5H4CH2CH2C8F17)(CO)] (6). The complexes 9 and 11 were employed in dehydrogenation reactions of cycloalkanes in C6F14/hydrocarbon mixtures. Photocatalytic conversions were observed and a turnover number of 16 for the dehydrogenation of cyclooctane with complex 11 was obtained.

Reduced CO

The complex trans-[Pt(F)(SF

A series of heterodinuclear complexes (M-1-Re) based on a phenanthroline (phen) extended tetramesityl porphyrin ligand (H2-1) has been prepared. The phen moiety of this ligand selectively coordinates a Re(I) tricarbonyl chloride unit, whereas the metal in the porphyrin moiety has been varied: namely, Cu, Pd, Zn, Co, or Fe was used. These dinuclear complexes were fully characterized by standard analytical methods. Additionally, a crystal structure of Cu-1-Re·5.5(C7H8)·0.5(C6H6) could be obtained, and extended time-resolved emission lifetime measurements were conducted. Furthermore, their ability to catalyze the photochemical reduction of CO2 to CO was investigated. Light-driven CO2 reduction experiments were performed in dimethylformamide (DMF) using triethylamine (TEA) as the sacrificial electron donor. The TONs (turnover numbers) of CO were determined and revealed a surprising catalytic activity that is obviously independent from the redox activity of the porphyrin metal. We have recently shown that the parent M-1 compounds are active photocatalysts, but the catalytic activity was dependent on the redox activity of the porphyrin metal. In the case of the new heterodinuclear complexes M-1-Re reported in this study, the catalytic active center seems to be the Re(I) moiety and not the porphyrin. Surprisingly, Zn-1-Re proved to be the most active compound in this series showing a TONCO of 13 after 24 h of illumination using a >375 nm cutoff filter while all other compounds showed minimal activity under this condition.

The compound BiCl(o-PPh2-C6H4)2, PBiP-Cl, which in previous work had been shown to form complexes with pronounced M→Bi character, when metal(I) ions of group 11 or PtII and PdII ions were coordinated, behave differently in contact with late metal atoms in low oxidation states, known to easily undergo oxidative additions: Treatment of PBiP-Cl with M(PPh3)4, with M = Pt, Pd, led to the formal insertion of M into the Bi–Cl bond to yield complexes [MCl(PBiP)]. Analogues PBiP-X with X = Br, I that could be accessed behaved similarly, producing [MX(PBiP)]. Both types of complexation reactions—coordination of PBiP-Cl as an ambiphilic ligand and oxidative addition—were observed to occur when [Ir(acac)(cod)] was chosen as the precursor compound. NMR investigations clearly indicated the presence of [IrI(acac)(PBiP-Cl)] and [IrIII(acac)Cl(PBiP)] beside each other in solution, from which, however, only [IrIII(acac)Cl(PBiP)] could be crystallized. DFT results showed that both products differ only slightly in energy. R...

Das bislang realistischste niedermolekulare Analogon fur die 1-Aminocyclopropan-1-carbonsaure-Oxidase (ACCO) wird beschrieben. Das aktive Zentrum der ACCO, bestehend aus einer 2-His-1-Carboxylateisen(II)-Spezies, wurde durch eine Tp-Eisen-Einheit nachgeahmt, welche in der Lage ist, ACC zu binden. Der resultierende Komplex [TpMe,PhFeACC] (1) stellt entsprechend einer fur das Nickelderivat durchgefuhrten Rontgenstrukturanalyse ein hervorragendes Strukturmodell dar, da es, wie fur das Enzym vorgeschlagen, das ACC zweizahnig koordiniert und eine freie Koordinationsstelle verbleibt. Letztere ermoglichte erstmalig auch die Nachahmung der Funktion: 1 ist der erste bekannte ACC-Komplex, der in der Reaktion mit Sauerstoff Ethylen produziert. Da als Teil des katalytischen Zyklus unter anderem ein FeOOH-Intermediat vorgeschlagen worden war, wurde auch H2O2 als Oxidationsmittel gepruft. Tatsachlich konnte eine noch schnellere Ethylen-Entwicklung mit einer Ausbeute von 65 % nachgewiesen werden.

Treatment of the iridium(I) complex trans-[Ir(4-C5F4N)(CNtBu)(PiPr3)2] (2) with O2 or H2O2 gave the iridium(III) peroxido complex trans-[Ir(4-C5F4N)(O2)(CNtBu)(PiPr3)2] (3a). The peroxido complex 3a reacts with Bronsted acids to give the iridium(III) complexes cis-[Ir(4-C5F4N)(X)2(CNtBu)(L)(PiPr3)] (4: X = Cl, L = PiPr3, 5: X = CF3COO, L = H2O) and hydrogen peroxide. In the presence of formic acid, 3a yields the carbonato complex trans-[Ir{κ2-OC(O)O}(4-C5F4N)(CNtBu)(PiPr3)2] (6) as the main product. Reactions between formic acid or dihydrogen and the iridium(I) complex 2 give the isomeric dihydrido complexes trans,trans-[Ir(4-C5F4N)(H)2(CNtBu)(PiPr3)2] (7a) and cis,trans-[Ir(4-C5F4N)(H)2(CNtBu)(PiPr3)2] (9a), respectively.