Project description:Heterobimetallic CuPd and CuPt bis(mu-oxo) complexes have been prepared by the reaction of (PPh3)2MO2 (M=Pd, Pt) with LCu(I) precursors (L=beta-diketiminate and di- and triamine ligands) and characterized by low-temperature UV-vis, resonance Raman, and 1H and 31P[1H] NMR spectroscopy in conjunction with DFT calculations. The complexes decompose upon warming to yield OPPh3, and in one case this was shown to occur by an intramolecular process through crossover experiments using double-labeling (oxo and phosphine). The reactivity of one of the complexes, LMe2Cu(mu-O)2Pt(PPh3)2 (LMe2 = beta-diketiminate), with a variety of reagents including CO2, 2,4-di-tert-butylphenol, 2,4-di-tert-butylphenolate, [NH4][PF6], and dihydroanthracene, was compared to that of homometallic Pt2 and Cu2 counterparts. Unlike typical [Cu2(mu-O)2]2+ cores which have electrophilic oxo groups, the oxo groups in the [Cu(mu-O)2Pt]+ core behave as bases and nucleophiles, similar to previously described Pt2 compounds. In addition, however, the [Cu(mu-O)2Pt]+ core is capable of oxidatively coupling 2,4-di-tert-butylphenol and 2,4-di-tert-butylphenolate. Theoretical evaluation of the electron affinities, basicities, and H-atom transfer kinetics and thermodynamics of the Cu2 and CuM (M=Pd, Pt) cores showed that the latter are more basic and form stronger O-H bonds.
Project description:Three diplatinum(II) complexes [{PtL}2(μ-thea)] (H4thea = 2,3,6,7-tetrahydroxy-9,10-dimethyl-9,10-dihydro-9,10-ethanoanthracene) have been prepared, with diphosphine or bipyridyl "L" co-ligands. One-electron oxidation of these complexes gave radical cations containing a mixed-valent [thea·](3-) ligand with discrete catecholate and semiquinonate centers separated by quaternary methylene spacers. The electronic character of these radicals is near the Robin-Day class II/III border determined by UV/Vis/NIR and EPR spectroscopies. Crystal-structure determinations and a DFT calculation imply that oxidation of the thea(4-) ligand may lead to an increased through-space interaction between the dioxolene π systems.
Project description:A terminal FeIIIOH complex, [FeIII(L)(OH)]2- (1), has been synthesized and structurally characterized (H4L = 1,2-bis(2-hydroxy-2-methylpropanamido)benzene). The oxidation reaction of 1 with one equiv. of tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBAH) or ceric ammonium nitrate (CAN) in acetonitrile at -45 °C results in the formation of a FeIIIOH ligand radical complex, [FeIII(L˙)(OH)]- (2), which is hereby characterized by UV-visible, 1H nuclear magnetic resonance, electron paramagnetic resonance, and X-ray absorption spectroscopy techniques. The reaction of 2 with a triphenylcarbon radical further gives triphenylmethanol and mimics the so-called oxygen rebound step of Cpd II of cytochrome P450. Furthermore, the reaction of 2 was explored with different 4-substituted-2,6-di-tert-butylphenols. Based on kinetic analysis, a hydrogen atom transfer (HAT) mechanism has been established. A pK a value of 19.3 and a BDFE value of 78.2 kcal/mol have been estimated for complex 2.
Project description:In the title compound, [Ni(2)(C(16)H(18)FN(3)O(3))(2)(H(2)O)(4)](OH)(NO(3)), the cationic [Ni(2)(C(16)H(18)FN(3)O(3))(2)(H(2)O)(4)](2+) building units are linked through Ni-O(carboxyl-ate) and Ni-N(amino) bridges into a layer structure. The two independent nickel atoms lie on inversion centres: one adopts an NiO(6) octa-hedral geometry, the other a trans-NiN(2)O(4) octahedral arrangement. The charge-balancing hydroxide and nitrate ions are of half site occupancy each. A network of O-H⋯O and N-H⋯O hydrogen bonds helps to establish the packing.
Project description:In the crystal structure of the title compound, [Ni(2)(NCS)(4)(C(4)H(4)N(2))(3)(CH(3)OH)(2)](n), each nickel(II) cation is coordinated by three N-bonded pyrimidine ligands, two N-bonded thio-cyanate anions and one O-bonded methanol mol-ecule in a distorted octa-hedral environment. The asymmetric unit consists of one nickel cation, two thio-cyanate anions and one methanol mol-ecule in general positions, as well as one pyrimidine ligand located around a twofold rotation axis. The crystal structure consists of μ-N:N' pyrimidine-bridged zigzag-like nickel thio-cyanate chains; these are further linked by μ-N:N-bridging pyrimidine ligands into layers which are stacked perpendicular to the b axis. The layers are connected via weak O-H⋯S hydrogen bonding.
Project description:The strikingly different reactivity of a series of homo- and heterodinuclear [(MIII )(?-O)2 (MIII )']2+ (M=Ni; M'=Fe, Co, Ni and M=M'=Co) complexes with ?-diketiminate ligands in electrophilic and nucleophilic oxidation reactions is reported, and can be correlated to the spectroscopic features of the [(MIII )(?-O)2 (MIII )']2+ core. In particular, the unprecedented nucleophilic reactivity of the symmetric [NiIII (?-O)2 NiIII ]2+ complex and the decay of the asymmetric [NiIII (?-O)2 CoIII ]2+ core through aromatic hydroxylation reactions represent a new domain for high-valent bis(?-oxido)dimetal reactivity.
Project description:Solid polymer electrolyte electrochemical energy conversion devices that operate under highly alkaline conditions afford faster reaction kinetics and the deployment of inexpensive electrocatalysts compared with their acidic counterparts. The hydroxide anion exchange polymer is a key component of any solid polymer electrolyte device that operates under alkaline conditions. However, durable hydroxide-conducting polymer electrolytes in highly caustic media have proved elusive, because polymers bearing cations are inherently unstable under highly caustic conditions. Here we report a systematic investigation of novel arylimidazolium and bis-arylimidazolium compounds that lead to the rationale design of robust, sterically protected poly(arylimidazolium) hydroxide anion exchange polymers that possess a combination of high ion-exchange capacity and exceptional stability.
Project description:A reactive high-valent dinuclear nickel(IV) oxido bridged complex is reported that can be formed at room temperature by reaction of [(L)2Ni(II)2(?-X)3]X (X = Cl or Br) with NaOCl in methanol or acetonitrile (where L = 1,4,7-trimethyl-1,4,7-triazacyclononane). The unusual Ni(IV) oxido species is stabilized within a dinuclear tris-?-oxido-bridged structure as [(L)2Ni(IV)2(?-O)3]2+. Its structure and its reactivity with organic substrates are demonstrated through a combination of UV-vis absorption, resonance Raman, 1H NMR, EPR, and X-ray absorption (near-edge) spectroscopy, ESI mass spectrometry, and DFT methods. The identification of a Ni(IV)-O species opens opportunities to control the reactivity of NaOCl for selective oxidations.
Project description:Three complexes of cyclotricatechylene (H6ctc), [{PtL}3(?3-ctc)], have been synthesised: (L = 1,2-bis(diphenylphosphino)benzene {dppb}, 1; L = 1,2-bis(diphenylphosphino)ethane {dppe}, 2; L = 4,4'-bis(tert-butyl)-2,2'-bipyridyl { t Bu2bipy}, 3). The complexes show three low-potential, chemically reversible voltammetric oxidations separated by ca. 180 mV, corresponding to stepwise oxidation of the [ctc]6- catecholato rings to the semiquinonate level. The redox series [1]0/1+/2+/3+ and [3]0/1+/2+/3+ have been characterised by UV/vis/NIR spectroelectrochemistry. The mono- and di-cations have class II mixed valent character, with reduced radical delocalisation compared to an analogous bis-dioxolene system. The SOMO composition of [1?]+ and [3?]+ has been delineated by cw EPR, ENDOR and HYSCORE spectroscopies, with the aid of two monometallic model compounds [PtL(DBsq?)]+ (DBsqH = 3,5-bis(tert-butyl)-1,2-benzosemiquinone; L = dppe or t Bu2bipy). DF and time-dependent DF calculations confirm these interpretations, and demonstrate changes to spin-delocalisation in the ctc macrocycle as it is sequentially oxidised.
Project description:In the title compound, Na(2)CaNi(2)(P(2)O(7))(2)(H(2)O)(10), there are two distinct P-atom sites, each tetra-hedrally coordinated by four O atoms. The resulting phosphate tetra-hedra link through a common O atom, forming a [P(2)O(7)](4-) diphosphate unit. The Ni-O coordination is square pyramidal with four O atoms from two diphosphate groups in equatorial positions and the vertex occupied by a water O atom. The (P(2)O(7))(H(2)O) units link the Ni atoms, forming a chain of pyramids and tetra-hedra. As a result of the d-glide and twofold-axis symmetry of space group Fdd2, the chains propagate along [101] and [10], and chains in adjacent layers are mutually orthogonal. The Ca cation, located on a rotation axis, and the Na cation are each octa-hedrally coordinated by four O atoms and two waters. The Ni-chain arrangement is stabilized by Ca and Na coordination and a network of O-H⋯O hydrogen bonds.