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Ruthenium complexes of hemilabile phosphinocarboxamide ligands, and their use to form metallacycles using halide abstraction/deprotonation reactions are reported. Thus, [Ru(p-cym){PPh2C(=O)NHR}Cl2; R = iPr (1), Ph (2), p-tol (3)] and [Ru(p-cym){PPh2C(=O)N(R)C(=O)N(H)R}Cl2; R = Ph (4), p-tol (5)] were synthesized from [(p-cym)RuCl2]2 (p-cym = para-cymene) and phosphinocarboxamides or phosphinodicarboxamides, respectively. Single crystal X-ray diffraction measurements on 1–5 reveal coordination to ruthenium through the phosphorus donor, with an intramolecular hydrogen bond between the amine-bound proton and a metal-bound chloride. Six-membered metallacycles formed by halide abstraction/deprotonation of complexes 4 and 5 afforded [Ru(p-cym){κ2-P,N-PPh2C(=O)N(R)C(=O)NR}Cl] [R = Ph (6), p-tol (7)]. These species exist as a mixture of two rotational isomers in solution, as demonstrated by NMR spectroscopy.

We report the reversible adsorption of ammonia (NH3) up to 9.9 mmol g–1 in a robust Al-based metal–organic framework, MFM-303(Al), which is functionalized with free carboxylic acid and hydroxyl groups. The unique pore environment decorated with these acidic sites results in an exceptional packing density of NH3 at 293 K (0.801 g cm–3) comparable to that of solid NH3 at 193 K (0.817 g cm–3). In situ synchrotron X-ray diffraction and inelastic neutron scattering reveal the critical role of free −COOH and −OH groups in immobilizing NH3 molecules. Breakthrough experiments confirm the excellent performance of MFM-303(Al) for the capture of NH3 at low concentrations under both dry and wet conditions.

A two-coordinate Fe(II) m-terphenyl complex acts as a precatalyst for the hydroamination of isocyanates, affording urea and biuret derivatives, with product selectivity accomplished via modificatio...

Co-crystals of thiocyanuric acid (TCA) and five multitopic bases are reported, and their structures are compared. The adducts of all five co-crystals form two-dimensional hydrogen-bonded sheets tha...

In this paper, we describe experimental evidence of a change in the emission energy as a function of the Au-Au distance. We have employed a luminescent complex exhibiting an aurophilic interaction, which is weak enough to allow its length to be modified by external pressure but rigid enough to confer structural stability on the complex. By determining the crystal structures and emission characteristics over a range of pressures, we have identified an exponential relationship between the energy of the emitted light and the metal-metal distances under pressure. This result can be indirectly related to the repulsive branch of the fitted function representing the energy of the system in the ground state at different Au-Au distances. The relativistic nature of gold appears to play an important role in the behavior of this complex.

The development of synthetic analogs of the active sites of [NiFe] hydrogenases remains challenging, and, in spite of the number of complexes featuring a [NiFe] center, those featuring CO and CN- ligands at the Fe center are under-represented. We report herein the synthesis of three bimetallic [NiFe] complexes [Ni(N2S2)Fe(CO)2(CN)2], [Ni(S4)Fe(CO)2(CN)2], and [Ni(N2S3)Fe(CO)2(CN)2] that each contain a Ni center that bridges through two thiolato S donors to a {Fe(CO)2(CN)2} unit. X-ray crystallographic studies on [Ni(N2S3)Fe(CO)2(CN)2], supported by DFT calculations, are consistent with a solid-state structure containing distinct molecules in the singlet (S = 0) and triplet (S = 1) states. Each cluster exhibits irreversible reduction processes between -1.45 and -1.67 V vs Fc+/Fc and [Ni(N2S3)Fe(CO)2(CN)2] possesses a reversible oxidation process at 0.17 V vs Fc+/Fc. Spectroelectrochemical infrared (IR) and electron paramagnetic resonance (EPR) studies, supported by density functional theory (DFT) calculations, are consistent with a NiIIIFeII formulation for [Ni(N2S3)Fe(CO)2(CN)2]+. The singly occupied molecular orbital (SOMO) in [Ni(N2S3)Fe(CO)2(CN)2]+ is based on Ni 3dz2 and 3p S with the S contributions deriving principally from the apical S-donor. The nature of the SOMO corresponds to that proposed for the Ni-C state of the [NiFe] hydrogenases for which a NiIIIFeII formulation has also been proposed. A comparison of the experimental structures, and the electrochemical and spectroscopic properties of [Ni(N2S3)Fe(CO)2(CN)2] and its [Ni(N2S3)] precursor, together with calculations on the oxidized [Ni(N2S3)Fe(CO)2(CN)2]+ and [Ni(N2S3)]+ forms suggests that the binding of the {Fe(CO)(CN)2} unit to the {Ni(CysS)4} center at the active site of the [NiFe] hydrogenases suppresses thiolate-based oxidative chemistry involving the bridging thiolate S donors. This is in addition to the role of the Fe center in modulating the redox potential and geometry and supporting a bridging hydride species between the Ni and Fe centers in the Ni-C state.

The structural characterization of single crystals of di-4-pyridyl-substituted 3,4,9,10-perylenetetracarboxylic diimide reveals a surprising triple helical arrangement. The intermolecular interactions that lead to such an arrangement are investigated by Hirshfeld surface analysis and indicate that the supramolecular structure arises due to a combination of C–H···O interactions and π–π stacking interactions between adjacent perylene diimide (PDI) species. The interplay of these interactions leads to the formation of a tubular structure enclosed by the triple helix of PDI molecules. In contrast, the analogous phenyl-substituted molecule forms a simple one-dimensional stack of PDI molecules which is also unusual in that the perylene core adopts an essentially planar arrangement despite bay substitution.

The tetranuclear heterometallic complex [Li2Zn2(piv)6(py)2] (1, where piv– = pivalate and py = pyridine) has been successfully employed as a presynthesized node for the construction of four porous metal–organic frameworks (MOFs) [Li2Zn2(R-bdc)3(bpy)]·solv (2-R, R-bdc2–; R = H, Br, NH2, NO2) by reaction with 4,4′-bipyridine (bpy) and terephthalate anionic linkers. The [Li2Zn2] node is retained in the products, representing a rare example of the rational step-by-step design of isoreticular MOFs based on complex heterometallic building units. The permanent porosity of the activated frameworks was confirmed by gas adsorption isotherm measurements (N2, CO2, CH4). Three compounds, 2-H, 2-Br, and 2-NH2 (but not 2-NO2), feature extensive hysteresis between the adsorption and desorption curves in the N2 isotherms at low pressures. The substituents R decorate the inner surface and also control the aperture of the channels, the volume of the micropores, and the overall surface area, thus affecting both the gas uptak...

Recrystallization of [PdCl2([9]aneS2O)] ([9]aneS2O = 1-oxa-4,7-dithiacyclononane), 1, and [PtCl2([9]aneS2O)], 2, by diffusion of Et2O vapor into solutions of the complexes in MeNO2 yielded three phases of 1 and two phases of 2. The known phase of 1, herein designated α-1, was obtained under ambient conditions. A second phase, designated β-1, was initially also obtained by this method; however, following the advent of a third phase, γ-1, all subsequent efforts over a period of a year to crystallize β-1 yielded either γ-1, obtained by carrying out the recrystallization at elevated temperature, or α-1, commonly found throughout the study. This persistent absence of a phase which could initially be crystallized with ease led us to the conclusion that β-1 was an example of a “disappearing polymorph”. The first phase obtained of 2, designated α-2, was obtained by recrystallization under ambient conditions and is isomorphous and isostructural with α-1. The second phase β-2 was obtained by slight elevation of the recrystallization temperature and was found to be isomorphous and isostructural with β-1. Subsequently, β-2 was used to seed the growth of the disappearing polymorph β-1. No third phase of 2 (γ-2) has been isolated thus far., Following the discovery of a third polymorph of [PdCl2([9]aneS2O)] ([9]aneS2O = 1-oxa-4,7-dithiacyclononane), the second polymorph could no longer be grown and was therefore designated as a “disappearing polymorph”. The subsequent discovery that a closely analogous Pt(II) complex [PtCl2([9]aneS2O)] formed an isomorphous phase allowed the recovery of the lost polymorph by means of epitaxy.

Reaction of [{Au(C6X5)2}Ag]n (X = Cl, F) with the crown thioethers 1,4,7-trithiacyclononane ([9]aneS3), 1,4,8,11-tetrathiacyclotetradecane ([14]aneS4), or 1,4,7,10,13,16,19,22-octathiacyclotetracosane ([24]aneS8) affords a series of heteronuclear Au(I)/Ag(I) compounds of stoichiometry [{Au(C6X5)2}Ag(L)x] (L = [9]aneS3, x = 2 (1, 4); L = [14]aneS4, x = 1 (2, 5); L = [24]aneS8, x = 0.5 (3, 6)) formed via Ag-S bonds and Au···Ag contacts. X-ray diffraction studies of some of these complexes reveal different structural arrangements and nuclearity depending on the nature of the crown thioether ligand and on the presence or absence of aurophilic interactions. All the complexes are luminescent in the solid state but not in solution. Density functional theory calculations on representative model systems of complexes 2-4 and 6 were carried out to determine the origin of the electronic transitions responsible for their optical properties, which strongly depend on the nature of the perhalophenyl groups bonded to gold.

The synthesis and characterization of magnesium and calcium complexes of sterically demanding aminopyridinato ligands is reported. The reaction of the 2-Me3SiNH-6-MeC5H3N (L(1)H), 2-MePh2SiNH-6-MeC5H3N (L(2)H), and 2-Me3SiNH-6-PhC5H3N (L(3)H) with KH in tetrahydrofuran (THF) yielded potassium salts L(1)K(thf)0.5 (1), L(2)K (2), and L(3)K(thf)0.5 (3), which, through subsequent reaction with MgI2 and CaI2, afforded the homoleptic complexes (L)2Ae(thf)n [L = L(1), Ae = Mg, n = 1 (4); L = L(2), Ae = Mg, n = 0 (5); L = L(3), Ae = Mg, n = 0 (6); L = L(2), Ae = Ca, n = 2 (7)] and heterobimetallic calciates {[(L)3Ca]K}∞ [L = L(1) (8); L = L(2) (9)]. The solid state structure of 8 reveals a polymeric arrangement in which the calciate units are interlocked by bridging potassium ions. Metalation reactions between L(1)H or L(2)H and ((n)Bu)2Mg lead to the solvent-free compounds (L)2Mg [L = L(1) (10); L = L(2) (5)]. The bridged butyl mixed-metal complex [(L(1))Li(μ2-(n)Bu)Mg(L(1))]∞ (11) was also obtained via a cocomplexation reaction with (n)BuLi and ((n)Bu)2Mg. 11, which adopts a monodimensional polymeric array in the solid state, is a rare example of an alkyl-bridged Li/Mg complex and the first complex to feature an unsupported bridging butyl interaction between two metals. Changing the cocomplexation reaction conditions, the order of reagents added to the reactions mixture, and with the use of a coordinating solvent (tetrahydrofuran) formed the magnesiate complex (L(1))3MgLi(thf) (12).

Treatment of [M(Bn)] (M = K, Cs) with [HC{C(But)NDipp}{C(But)NHDipp}] (LButH; Dipp = 2,6-diisopropylphenyl) afforded [K(LBut)(THF)n], 1, and [Cs(LBut)], 2, which were crystallized from hexane or benzene to afford [K(LBut)(THF)3], 1a, and [{Cs(LBut)}{Cs(LBut)(η3-C6D6)}·C6D6]∞, 2a, respectively. Complexes 1 and 2 were utilized in the preparation of the previously reported [U(LBut)Cl3], which was cleanly converted to [U(LBut)I3], 3, via reaction with an excess of Me3SiI. Attempts to prepare U(III) complexes incorporating the LBut ligand proved unsuccessful, but utilizing [HC{C(Me)NDipp}{C(Me)NHDipp}] (LMeH) led to the isolation of [U(LMe)I2(THF)2], 4, via the reaction of [K(LMe)] with [U(I)3(THF)4]. Complex 4 can be derivatized via reaction with [K(Cp*)] (Cp* = η5-C5Me5) or [K{N(SiMe3)2}] to afford [U(LMe)(Cp*)I], 5, and [U(LMe){N(SiMe3)2}I], 6, respectively. The reaction of 4 with two equivalents of [K{N(SiMe3)2}] did not afford [U(LMe){N(SiMe3)2}2] as expected, but instead led to the isolation of the U(IV)...

The synthesis and separation of the 1,6- and 1,7- isomers of N,N'-bis(alkyl)diadamantylthio-3,4,9,10-perylenetetracarboxylic acid diimide are reported. Investigations of the structural, electrochemical, spectroscopic, and spectroelectrochemical properties of the isomers reveal a sequence of electrochemically and chemically reversible reduction processes for both isomers. Three X-ray crystal structures are reported including a pair of 1,6- and 1,7-isomers demonstrating the twist of the perylene core in the solid state. Our studies thoroughly characterize the mono- and direduced states of the two isomers allowing unequivocal characterization of the reduced species by UV-vis and IR spectroscopic measurements. EPR studies also allow direct identification of the monoreduced PTCDI species and spectroscopic measurements confirm the delocalization of electronic density around the carbonyl moieties of the reduced species.

Porous NOTT-202a shows exceptionally high uptake of SO2, 13.6 mmol g(-1) (87.0 wt %) at 268 K and 1.0 bar, representing the highest value reported to date for a framework material. NOTT-202a undergoes a distinct irreversible framework phase transition upon SO2 uptake at 268-283 K to give NOTT-202b which has enhanced stability due to the formation of strong π···π interactions between interpenetrated networks.

The solid state structures of alkali metal complexes of the 1,3,6,8-tetra-tert-butylcarbazol-9-yl ((t)Bu4carb(-)) ligand are compared. Lithium complex [(t)Bu4carbLi]2 ([1]2) is a dimer in the solid state featuring a planar LiNLiN rhomboid ring, with the differing Li-N distances within the ring due to the effects of σ- and π-interactions. Recrystallization of lithium, sodium, and potassium complexes of the 1,3,6,8-tetra-tert-butylcarbazol-9-yl ligand from THF leads to the formation of (t)Bu4carbLi(THF)2 (1·2THF), (t)Bu4carbNa(THF)3 (2·3THF), and (t)Bu4carbK(THF)4 (3·4THF), respectively, in the solid state. For these THF adducts, on proceeding from lithium to sodium to potassium there is an increase in hapticity of the binding of the carbazol-9-yl ligands to the metal cations, mirroring the increasing ionic bonding character in these compounds.

The yttrium carbene complex [Y(BIPM)(I)(THF)2] (1; BIPM = C(PPh2NSiMe3)2) was reacted with a range of unsaturated substrates. The reaction of 1 with the phosphaalkyne PCBut afforded the [2 + 2] cyc...

The yttrium alkyl carbene complex [Y(BIPM)(CH2Ph)(THF)] (1; BIPM = {C(PPh2NSiMe3)2})2–) was treated with a series of unsaturated organic substrates, a bulky primary amine, and a group 1 metal alkyl to gauge and compare the reactivity of the Y═Ccarbene and Y–Calkyl bonds. Treatment of 1 with tert-butyl nitrile and 1-adamantyl azide gave the 1,2-migratory insertion products [Y(BIPM){NC(But)(CH2Ph)}(THF)] (2) and [Y(BIPM){N3Ad-1,Bn-3-κ2N1,3}(THF)] (3), respectively, with no reactivity observed at the Y═C double bond even when an excess of the relevant organic substrate was added. In contrast, the heteroallenes N,N′-dicyclohexylcarbodiimide and tert-butyl isocyanate reacted at both the Y═Ccarbeneand Y–Calkyl bonds of 1 to afford [Y{C(PPh2NSiMe3)2[C(NCy)2]-κ4C,N,N′,N″}{C(NCy)2(CH2Ph)-κ2N,N′}] (4) and [Y{C(PPh2NSiMe3)2[C(O)(NBut)]-κ4C,N,N′,O}{C(O)(NBut)(CH2Ph)-κ2N,O}] (5), respectively. 4 and 5 form regardless of the molar ratio of 1 to heteroallene, with no intermediates observed; thus, it is not clear if the ...

We report attempts to prepare uranyl(VI)- and uranium(VI) carbenes utilizing deprotonation and oxidation strategies. Treatment of the uranyl(VI)-methanide complex [(BIPMH)UO2Cl(THF)] [1, BIPMH = HC(PPh2NSiMe3)2] with benzyl-sodium did not afford a uranyl(VI)-carbene via deprotonation. Instead, one-electron reduction and isolation of di- and trinuclear [UO2(BIPMH)(μ-Cl)UO(μ-O){BIPMH}] (2) and [UO(μ-O)(BIPMH)(μ3-Cl){UO(μ-O)(BIPMH)}2] (3), respectively, with concomitant elimination of dibenzyl, was observed. Complexes 2 and 3 represent the first examples of organometallic uranyl(V), and 3 is notable for exhibiting rare cation–cation interactions between uranyl(VI) and uranyl(V) groups. In contrast, two-electron oxidation of the uranium(IV)-carbene [(BIPM)UCl3Li(THF)2] (4) by 4-morpholine N-oxide afforded the first uranium(VI)-carbene [(BIPM)UOCl2] (6). Complex 6 exhibits a trans-CUO linkage that represents a [R2C═U═O]2+ analogue of the uranyl ion. Notably, treatment of 4 with other oxidants such as Me3NO, C5...

A range of nitroalkenes 1 and imines 3 derived from alkyl, aryl, and heteroaryl aldehydes underwent a tandem 1,4-hydride addition nitro-Mannich reaction to afford anti-rich β-nitroamines 4. The crude anti-β-nitroamines 4 could be converted to the corresponding anti-β-nitroacetamides 5 (33 examples) to allow purification in good yield from the parent nitroalkenes (60–87%), and with a high diastereomeric ratio (90:10 to mostly >95:5). A representative selection of anti-β-nitroacetamides 5 (five examples) were reduced to vicinal diamines 7 with zinc hydrochloride; concomitant acyl migration provided differentially protected vicinal diamines 7 in good yield (80–91%).

Treatment of [Li{HC(PPh2NSiMe3)2}]2 with 2 equiv of [MOR] (M = Rb, Cs; OR = 2-ethylhexoxide) afforded the heavy group 1 methanides [Rb{HC(PPh2NSiMe3)2}(THF)2] (1) and [Cs{HC(PPh2NSiMe3)2}(DME)2] (2), which do not exhibit methanide C···M contacts in the solid state. Following a literature procedure, H2C(PPh2)2 was reacted with 2 equiv of AdN3 (Ad = adamantyl) to give H2C(PPh2NAd)2 (3). Reaction of 3 with 1 equiv of ButLi in toluene afforded dimeric [Li{HC(PPh2NAd)2}]2 (4). Treatment of 3 with 1 equiv of [M(Bn)] (M = Na, K; Bn = CH2C6H5) in THF gave the Lewis base adducts [M{HC(PPh2NAd)2}(THF)2] [M = Na (5), K (6)]. The heavy group 1 methanides [Rb{HC(PPh2NAd)2}(THF)2] (7) and [Cs{HC(PPh2NAd)2}(DME)2] (8) were prepared by the reaction of [MOR] (M = Rb, Cs; OR = 2-ethylhexoxide) with 4 or reaction of [Cs(Bn)] with 3. The synthetic utility of these group 1 transfer agents has been demonstrated by the preparation of [La{HC(PPh2NR)2}(I)2(THF)] [R = SiMe3 (9), Ad (10)] from [La(I)3(THF)4], employing a salt metat...

Treatment of H2C(PPh2NMes)2 (Mes = 2,4,6-trimethylphenyl) with 1 equiv of [Na(Bn)] (Bn = CH2C6H5) in THF gave the Lewis base adduct [Na{HC(PPh2NMes)2}(THF)2] (1). The heavy group 1 methanides [Rb{HC(PPh2NMes)2}(DME)2] (2) and [Cs{HC(PPh2NMes)2}]6 (3) were prepared by the reaction of [MOR] (M = Cs, Rb; OR = 2-ethylhexoxide) with [Li{HC(PPh2NMes)2}]. The Lewis base adduct 2 is monomeric, but 3 exists as a novel cyclic 2.9 nm hexamer in the solid state even though it was recrystallized from the strong donor solvent THF. The reaction of H2C(PPh2NDipp)2 (Dipp = 2,6-diisopropylphenyl) with [Na(Bn)] afforded [Na{HC(PPh2NDipp)2}(THF)] (4). The potassium congener [K{HC(PPh2NDipp)2}(THF)2] (5) was prepared by the reaction of the parent methane with KH. In 5, the methanide ligand is bound to potassium through one N center, the methanide center, and an η6-Dipp interaction. However, the THF molecules in 5 are loosely bound, as evidenced by the isolation of dimeric [{K[HC(PPh2NDipp)2](THF)}2] (6) from hexane. In 6, the...

Three isostructural anionic frameworks {[(Hdma)(H(3)O)][In(2)(L(1))(2)]·4DMF·5H(2)O}(∞) (NOTT-206-solv), {[H(2)ppz][In(2)(L(2))(2)]·3.5DMF·5H(2)O}(∞) (NOTT-200-solv), and {[H(2)ppz][In(2)(L(3))(2)]·4DMF·5.5H(2)O}(∞) (NOTT-208-solv) (dma = dimethylamine; ppz = piperazine) each featuring organic countercations that selectively block the channels and act as pore gates have been prepared. The organic cations within the as-synthesized frameworks can be replaced by Li(+) ions to yield the corresponding Li(+)-containing frameworks {Li(1.2)(H(3)O)(0.8)[In(2)(L(1))(2)]·14H(2)O}(∞) (NOTT-207-solv), {Li(1.5)(H(3)O)(0.5)[In(2)(L(2))(2)]·11H(2)O}(∞) (NOTT-201-solv), and {Li(1.4)(H(3)O)(0.6)[In(2)(L(3))(2)]·4acetone·11H(2)O}(∞) (NOTT-209-solv) in which the pores are now unblocked. The desolvated framework materials NOTT-200a, NOTT-206a, and NOTT-208a display nonporous, hysteretic and reversible N(2) uptakes, respectively, while NOTT-206a and NOTT-200a provide a strong kinetic trap showing adsorption/desorption hysteresis with H(2). Single crystal X-ray analysis confirms that the Li(+) ions are either tetrahedrally (in NOTT-201-solv and NOTT-209-solv) or octahedrally (in NOTT-207-solv) coordinated by carboxylate oxygen atoms and/or water molecules. This is supported by (7)Li solid-state NMR spectroscopy. NOTT-209a, compared with NOTT-208a, shows a 31% enhancement in H(2) storage capacity coupled to a 38% increase in the isosteric heat of adsorption to 12 kJ/mol at zero coverage. Thus, by modulating the pore environment via postsynthetic cation exchange, the gas adsorption properties of the resultant MOF can be fine-tuned. This affords a methodology for the development of high capacity storage materials that may operate at more ambient temperatures.

Catalytic phosphorus(V)-mediated chlorination and bromination reactions of alcohols have been developed. The new reactions constitute a catalytic version of the classical Appel halogenation reaction. In these new reactions oxalyl chloride is used as a consumable stoichiometric reagent to generate the halophosphonium salts responsible for halogenation from catalytic phosphine oxides. Thus, phosphine oxides have been transformed from stoichiometric waste products into catalysts and a new concept for catalytic phosphorus-based activation and nucleophilic substitution of alcohols has been validated. The present study has focused on a full exploration of the scope and limitations of phosphine oxide catalyzed chlorination reactions as well as the development of the analogous bromination reactions. Further mechanistic studies, including density functional theory calculations on proposed intermediates of the catalytic cycle, are consistent with a catalytic cycle involving halo- and alkoxyphosphonium salts as intermediates.

Attempts to prepare [Dy{C(PPh2NSiMe3)2}(I)(THF)2] (1) from in situ prepared “[Dy(Bn)2(I)(THF)3]” (“2”; Bn = C6H5CH2) and H2C(PPh2NSiMe3)2 resulted in the isolation of [Dy{CH(PPh2NSiMe3)2}(I)2(THF)]...

Dirhodium tetraacetate catalyzed reaction of alpha-diazo-beta-keto-carboxylates and -phosphonates with arenecarboxamides gives 2-aryloxazole-4-carboxylates and 4-phosphonates by carbene N-H insertion and cyclodehydration. In stark contrast, dirhodium tetrakis(heptafluorobutyramide) catalysis results in a dramatic change of regioselectivity to give oxazole-5-carboxylates and 5-phosphonates. Alpha-diazo-beta-ketosulfones behave similarly and give 5-sulfonyloxazoles upon dirhodium tetrakis(heptafluorobutyramide) catalyzed reaction with carboxamides. The analogous reactions of thiocarboxamides give the corresponding thiazole-5-carboxylates, -phosphonates, and -sulfones.

Carbenes derived from diazoimidazolecarboxylates 4 under thermal or photochemical conditions undergo O-H and N-H insertion reactions with alcohols and amines, respectively, in moderate yield, in competition with reduction in good H-donor solvents. Dichloromethane reacts to give the corresponding 4-chloroimidazole. Aromatic hydrocarbons are excellent traps for the imidazolylidene carbene and lead to a range of arylimidazole derivatives 7. Reaction with pyridine leads to the first example of a pyridinium ylide 8 formed from an imidazolylidene carbene, whereas irradiation in hexafluorobenzene gives the imidazoazocine 11, presumably by way of an initial norcaradiene intermediate.

We have synthesized five new metal-organic coordination polymers incorporating the bent ligand H(2)hfipbb [4,4'-(hexafluoroisopropylidene)bis(benzoic acid)] with different transition metal ions and co-ligands via solvothermal reactions to give [Zn(2)(hfipbb)(2)(py)(2)] x DMF (1), [Zn(2)(hfipbb)(2)(4,4'-bipy)(H(2)O)] (2), [Zn(2)(hfipbb)(2)(bpdab)].2DMF (3), [Cd(2)(hfipbb)(2)(DMF)(2)] x 2 DMF (4), and [Co(hfipbb)(dpp)] x MeOH (5) (py = pyridine, 4,4'-bipy = 4,4'-bipyridine, bpdab = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, dpp = 1,3-di(4-pyridyl)propane). Compound 1 displays a 2-fold 2D--2D parallel interpenetrated layer network with one-dimensional (1D) helical channels, while 3 exhibits a three-dimensional pillared helical-layer open framework of alpha-Po topology based upon binuclear paddlewheel units. In compounds 2 and 5, binuclear motifs with double carboxylate bridges are linked by hfipbb(2-) ligands into a 1D ribbon, which are further assembled into two-dimensional non-interpenetrated (4,4) layers via bipyridyl co-ligands. However, the different bridging modes of hfipbb(2-) ligands and the different disposition of the coordinated co-ligands around metal ions result in subtle differences in the final architecture. Thus, 2 is based on a binuclear cluster node, double-stranded hfipbb(2-) linkers, and single-stranded 4,4'-bipy linkers, while 5 is based on a binuclear cluster node and hfipbb(2-) and dpp linkers which are both double-stranded. Among these compounds, the Cd(II) complex 4 is possibly the most interesting because it represents a rare example in which metal centers are linked by carboxylate groups into infinite chains further joined together by hfipbb(2-) spacers to form a 2D network with tubular helical channels. All these coordination polymers exhibit low solvent-accessible volumes. Both 3 and 4 retain structural integrity and permanent microporosity upon evacuation of guest molecules, with hydrogen uptakes of 0.57 and 0.78 wt %, respectively, at 20 bar and 77 K.

Treatment of [Cu(dipic)(OH2)3] [dipic2 = pyridine-2,6-dicarboxylate (dipicolinate)] 1 with diverse bipyridyl bridging ligands of varying length [pyrazine (pyz), 4,4′-bipyridine (bipy), trans-4,4′-azobis(pyridine) (azpy), 1,2-bis(pyridin-4-yl)ethene (bpe), 3,6-bis(pyridin-4-yl)-1,2,4,5-tetrazene (pytz) and 1,4-bis{2-(pyridin-4-yl)ethenyl}benzene (bpeb)] under a variety of conditions yielded [Cu2(dipic)2(bipy)]·4H2O, 2, [Cu2(dipic)2(bpe)]·2H2O, 3, [{Cu(dipic)(OH2)}(μ-pyz)0.5]·H2O, 4, [{Cu(dipic)(OH2)}(μ-pyz)0.5], 5, [{Cu(dipic)(OH2)}(μ-bipy)0.5][{Cu(dipic)(OH2)0.75(OHMe)0.25}(μ-bipy){Cu(dipic)(OH2)}]·2.25H2O·0.5CH3OH, 6, {[{Cu(dipic)}2(μ-bipy)]·2H2O·CH2Cl2}∞, 7, [{Cu(dipic)(OH2)}(μ-bpe){Cu(dipic)}]·3H2O, 8, {[{Cu(dipic)}(μ-azpy)0.5]·CH2Cl2}∞, 9, {[{Cu(dipic)}(μ-azpy)0.5]·CH3OH}∞, 10, [{Cu(dipic)(OH2)}2(μ-pytz)]·2H2O, 11, [Cu2(dipic)2(bpeb)]·4H2O, 12 and [{Cu(dipic)(OHMe)}2(μ-bpeb)], 13. Complexes 4−11 and 13 were characterized by single crystal X-ray diffraction which confirmed the presence of binuclear bui...

Four low-coordinate transition metal amido complexes featuring sterically demanding 1,8-bis(silylamido)naphthalene ligands are reported. Reaction of one molar equivalent of 1,8-C(10)H(6)(NLiSiMe(3))(2) with ZnCl(2) yields the structurally authenticated dimer [1,8-C(10)H(6)(NSiMe(3))(2)Zn](2) (1), where the 1,8-bis(silylamido)naphthalene moiety is acting as both a chelating and bridging ligand. The effect on the resulting transition metal complexes of increasing the steric demands of the ligand was investigated, using the triisopropylsilyl-substituted ligand 1,8-C(10)H(6)(NSi(i)Pr(3))(2). Reaction of one molar equivalent of 1,8-C(10)H(6)(NLiSi(i)Pr(3))(2) with ZnCl(2) or FeCl(2)(THF)(1.5) yields 1,8-C(10)H(6)(NSi(i)Pr(3))(2)M(mu-Cl)Li(THF)(3) (M = Zn, 2; M = Fe, 3), respectively; the coordination of the ClLi(THF)(3) moiety to the metal center in these compounds is a rare structural motif in the coordination chemistry of the d-block elements. Analogous reaction of 1,8-C(10)H(6)(NLiSi(i)Pr(3))(2) with MnCl(2) affords the mixed-metal Li-Mn-amido complex 1,8-C(10)H(6)(NSi(i)Pr(3))(2)Li(THF)MnCl(THF) (4) which features an unusual LiMnN(2) core.

Heteroleptic dibenzyl yttrium and erbium iodides [Ln(Bn)2(I)(THF)3] [Ln = Y (1), Er (2); Bn = CH2C6H5] were prepared in high yields and are remarkable for their thermal stability and inertness toward ligand scrambling in Schlenk-type equilibria. A variable-temperature study of 1 revealed a dynamic process in solution attributed to the presence of three isomers, namely, cis-fac, cis-mer, and trans-mer, which were observed in a 0.11:1:0.05 ratio at 298 K, respectively. Only the isomer attributed as cis-mer was observed at 313 K. The synthetic utility of 1 and 2, which combines the potential benefits of protonolysis and salt elimination chemistry, was demonstrated by the facile synthesis of phosphorus-stabilized yttrium and erbium carbenes [Ln(BIPM)(I)(THF)2] [Ln = Y (3); Er (4); BIPM = {C(PPh2NSiMe3)}2−], which each contain unusual T-shaped carbene centers. DFT calculations on 3, BIPM, and Ph3P═C═PPh3 showed very similar frontier orbital compositions in all three examples. Although 3 and 4 are classified as...

A series of multistate redox-active architectures has been synthesized, structurally characterized, and their optical and redox properties investigated. Specifically, two redox-active ferrocene or cobalt-dithiolene moieties have been introduced to the "bay" region of perylene-bisimides. Three of these disubstituted perylene-bisimide species have been structurally characterized by single crystal X-ray diffraction, confirming the twisted nature of the central perylene core. The first isomeric pair of disubstituted perylene-bisimide isomers, N,N'-di-(n-butyl)-1,7-diferrocenyl-perylene-3,4:9,10-tetracarboxylic acid bisimide (2) and N,N'-di-(n-butyl)-1,6-diferrocenyl-perylene-3,4:9,10-tetracarboxylic acid bisimide (3), structurally characterized by single crystal X-ray diffraction are reported and compared. Structural characterization of the cobalt-dithiolene substituted perylene-bisimide, N,N'-di-(n-butyl)-1,7-dicyclopentadienyl-cobalt(II)-dithiolenyl-perylene-3,4:9,10-tetracarboxylic acid bisimide (4), reveals the expected twisting of the perylene core and confirms the ene-dithiolate geometry of the cobalt dithiolene moiety. Cyclic voltammetry measurements, coupled with spectroelectrochemcial and electron paramagnetic resonance studies, of 1-4, where 1 is N,N'-di-(n-butyl)-1,7-diethynylferrocenyl-perylene-3,4:9,10-tetracarboxylic acid bisimide, reveal the two anticipated perylene-bisimide based reductions. In addition, for the ferrocene substituted compounds, 1-3, a single reversible two-electron oxidation is seen with only a small degree of communication between the ferrocene groups observed in the 1,6-isomer where the two ferrocene groups are attached to the same naphthyl moiety. In the case of 4, two reversible reductions associated with the cobalt-dithiolene moieties are observed, confirming communication across the reduced perylene core.

An unprecedented oxidative insertion of the activated ruthenium complex "Ru(CO)(PPh3)(2)" into aryl halide bonds enables a novel preparation of stable five-coordinate 16-electron d(6) sigma-aryl-Ru(II) complex Ru(CO)(p-C6H4Me)Br(PPh3)(2), which has been characterized by NMR, IR, elemental analysis, and X-ray crystallography. These novel five-coordinate Ru(II) complexes were investigated as potential intermediates in the ortho-arylation of aryl ketones (alpha-tetralone) through C-H activation and resulted in the formation of Ru(CO)(eta(1)-C, kappa(1)-O, alpha-tetralone)X(PPh3)(2) and toluene (X = Br or I).

The synthesis and separation of the 1,6- and 1,7- isomers of N,N'-bis(n-butyl)dimorpholino-3,4:9,10-perylenetetracarboxylic acid bisimide are reported. Investigations of the electrochemical and spectroscopic, in particular, spectroelectrochemical, properties of the two isomers reveal a sequence of electrochemically and chemically reversible redox processes for both isomers. Importantly, the 1,7-isomer of N,N'-bis(n-butyl)dimorpholino-3,4:9,10-perylenetetracarboxylic acid bisimide was observed to undergo a two-electron oxidation process, which contrasts with the behavior of both the corresponding 1,6-isomer and other related amino-substituted perylene bis-imide species.

The results of electrochemical measurements, density-functional theory calculations, emission and time-resolved IR (TRIR) spectroscopic studies for fac-[ReCl(CO)3(dppz-X2)], (dppz = dipyrido[3,2-a:2',3'-c]phenazine; X = CH3, H, F, Cl, CF3) are reported. For all complexes the calculations show that the lowest unoccupied molecular orbital (LUMO) is a phenazine based orbital localized on the dppz ligand. We observe that three different excited states, IL pi pi*, metal-to-ligand charge-transfer (MLCT) (phen), and MLCT (phz), are formed depending upon the substituent on the dppz ligand and on the nature of the solvent. This means that both the energy and the nature of the photophysically active state(s) can be tuned by both chemical modification of dppz ligand and solvent properties. The excited-state dynamics in these systems is directly related to the mechanism of the "light switch effect", and ps-TRIR has allowed a deeper insight into this mechanism by being able to directly monitor the change in the population of the higher lying emissive phen-type (3)MLCT and IL pi pi* states and the dark (3)MLCT (phz) state depending on the different environmental factors.

A second generation formal synthesis of the alkaloid (-)-cephalotaxine has been achieved using an alkylidene carbene 1,5-CH insertion reaction to establish a key quaternary stereocenter. The carbene precursor was readily derived from L-proline, and the 1,5-CH insertion reaction was performed under Ohira's conditions using lithiotrimethylsilyldiazomethane (LTDM), which gave the desired spirocyclic product in 74% yield. The hydroxymethyl group was then oxidized and then decarbonylated (93%), and this material was easily transformed into the desired Friedel-Crafts cyclization precursor. Exposure of this material to SnCl4 then gave the desired pentacyclic product, which was identical to that previously prepared by Mori and thus represents a formal total synthesis of (-)-cephalotaxine.

The d (0) yttrium N-heterocyclic carbene compound YL 3 (L = OCMe 2CH 2[C{N(CHCH)NPr ( i )}]) has been made and structurally characterized. It adopts a mer configuration of the three bidentate ligands. A comparison of this with the isostructural d (1) titanium complex TiL 3 is made in order to seek experimental evidence of a pi-bonding contribution to the M-C bond. This has been augmented by DFT calculations. Experimentally, the metal radius-corrected Ti-C distance is shorter than the Y-C distance, suggesting a pi-bonding contribution in the d (1) complex, but the computational data suggest that a shorter sigma bond might simply be formed by the more strongly polarizing titanium cation. From the potassium reduction of TiL(OPr ( i )) 3, only a byproduct arising from silicone grease activation was isolable, identified as a mixed-valent, multinuclear, d (0)/d (1) cluster [Ti (III)L 2{Pr ( i )OSiMe 2O}K 2OTi (IV)(OPr ( i )) 4] 2 in which the carbene ligands are bound to the Ti (III) centers in preference to Ti (IV), with longer Ti-C distances than those found in TiL 3.

Two new mixed aza-thia crowns 5-aza-2,8-dithia[9]-(2,9)-1,10-phenanthrolinophane (L(4)) and 2,8-diaza-5-thia[9]-(2,9)-1,10-phenanthrolinophane (L(7)) have been synthesized and characterized. The coordination behavior of L(4) and L(7) toward the metal ions Cu(II), Zn(II), Pb(II), Cd(II), Hg(II), and Ag(I) was studied in aqueous solution by potentiometric methods, in CD3CN/D2O 4:1 (v/v) by (1)H NMR titrations and in the solid state. The data obtained were compared with those available for the coordination behavior toward the same metal ions of structurally analogous mixed donor macrocyclic ligands L(1)-L(3), L(5), L(6): all these contain a phenanthroline subunit but have only S/O/N(aromatic) donor groups in the remaining portion of the ring and are, therefore, less water-soluble than L(4) and L(7). The complexes [Cd(NO3)2(L(5))], [Pb(L(7))](ClO4)2 x 1/2MeCN, [Pb(L(4))](ClO4)2 x MeCN, and [Cu(L(7))](ClO4)2 x 3/2MeNO2 were characterized by X-ray crystallography. The efficacy of L(1)-L(7) in competitive liquid-liquid metal ion extraction of Cu(II), Zn(II), Cd(II), Pb(II), Ag(I), and Hg(II) was assessed. In the absence of Hg(II), a clear extraction selectivity for Ag(I) was observed in all systems investigated.

An improved procedure for the preparation of enamine N-oxides involving aminolysis of epoxides, chlorination, N-oxidation, and dehydrochlorination is described. Although isolated beta-chloroamine N-oxides are prone to rearrangements when isolated, these side reactions can be slowed by the presence of stabilizing organic acids. The scope and limitations of this strategy are discussed.

An alkylidene carbene 1,5-CH insertion has been used as a key step in an enantioselective total syntheses of omuralide, its C7-epimer, and (+)-lactacystin. An additional noteworthy feature of the synthesis is the use of a novel oxidative deprotection procedure, utilizing DMDO, for the conversion of a late-stage benzylidene acetal into a primary alcohol and a secondary benzoate ester.

The synthesis of lithium(I) complexes of the neutral and anionic salts of a tridentate aminobis(N-heterocyclic carbene) ligand, L, are reported (L = N{CH2CH2(1-C[NCHCHNMes])}2), along with the X-ray diffraction determined molecular structure of the imidazolium proligand [H2N{CH2CH2(1-HC[NCHCHNMes])}2][Br]3 (H4LBr3). The transamination reaction between the lithium chloride adduct of HL and Y[N{SiMe3}2]3 affords yttrium amidocarbene complexes, while the transamination reaction between the imidazolium proligand and Ti(NMe2)4 or Zr(NMe2)4 affords a titanium or zirconium amidocarbene complex, respectively. The molecular structure of one of the yttrium products, Y(L)(N{SiMe3}2)Cl, is reported. The reactivity of a selection of the complexes with phosphine oxides is compared.

Two new fluorescent chemosensors for metal ions have been synthesized and characterized, and their photophysical properties have been explored; they are the macrocycles 5-(2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L5) and 5-(5-chloro-8-hydroxyquinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L6). Both systems have a pyridyl-thioether-containing 12-membered macrocycle as a binding site. The coordination properties of these two ligands toward CuII, ZnII, CdII, HgII, and PbII have been studied in MeCN/H2O (1:1 v/v) and MeCN solutions and in the solid state. The stoichiometry of the species formed at 25 degrees C have been determined from absorption, fluorescence, and potentiometric titrations. The complexes [CuL5](ClO4)(2).1/2MeCN, [ZnL5(H2O)](ClO4)2, [HgL5(MeCN)](ClO4)2, [PbL5(ClO4)2], [Cu3(5-Cl-8-HDQH-1)(L6H-1)2](ClO4)(3).7.5H2O (HDQ=hydroxyquinoline), and [Cu(L6)2](BF4)(2).2MeNO2 have also been characterized by X-ray crystallography. A specific CHEF-type response of L5 and L6 to the presence of ZnII and CdII, respectively, has been observed at about pH 7.0 in MeCN/H2O (1:1 v/v) solutions.

A comprehensive account of the synthesis, properties, and evaluation of a wide range of ethylene homopolymerization catalysts derived from imido titanium compounds supported by the triazacyclic ligands Me 3[9]aneN 3 and R 3[6]aneN 3 is described (Me 3[9]aneN 2 -1,4,7-trimethyltriazacyclononane; R 3[6]aneN 3 = 1,3,5-trimethyl- or 1,3,5-tris(n-dodecyl) triazacyclohexane). Conventional preparative-scale reactions afforded the triazacycle-supported imido titanium compounds Ti(NR)(Me 3[9]aneN 3)Cl 2 (R = tBu (1), 2,6-C 6H 3Me 2, 2,6-C 6H 3iPr 2, Ph, C 6F 5, or CH 2Ph (6)). Solid phase-supported analogues of 1 and 6 (linked by either the macrocycle or imido ligand to a 1% cross-linked polystyrene support) and representative Me 3[6]aneN 3 solution phase systems Ti(NR)(R 3[6]aneN 3)Cl 2 (R = Me or n-dodecyl) were also synthesized. At ambient temperature, solution phase Me 3[9]aneN 3 catalyst systems were more active for ethylene polymerization (methyl aluminoxane (MAO) cocatalyst) than their solid phase-supported or Me 3[6]aneN 3 analogues. A library of 41 other triazacyclononane-supported catalysts was prepared by the semiautomated, sequential treatment of Ti(NMe 2) 2Cl 2 with RNH 2 and Me 3[9]aneN 3. The ethylene polymerization capabilities of 46 compounds of the type Ti(NR)(Me 3[9]aneN 3)Cl 2 were evaluated at 100°C (MAO cocatalyst) and compared in representative cases to the corresponding productivities at ambient temperature. Whereas either bulky N-alkyl or N-aryl imido substituents in the compounds Ti(NR)(Me 3[9]aneN 3)Cl 2 were sufficient to give highly active catalysts at ambient temperature, only those with bulky N-alkyl groups excelled at 100°C. Polymer end group analysis indicated that polymeryl chain transfer to both AlMe 3 and ethylene monomer is an active mechanism in these systems. The use of MAO pretreated with BHT-H (BHT-H = 2,6-di-tert-butyl-4-methylphenol) led to higher productivites, increased polymer molecular weights, and more polymer chain unsaturations, but productivity decreased when a large excess of BHT-H was used. The reactions of the well-defined alkyl species Ti(N tBu)(Me 3[9]aneN 3)Me 2, [Ti(N tBu)(Me 3[9]aneN 3)-Cu-Me) 2AlMe 2] +, and [Ti(N tBu)(Me 3[9]aneN 3)Me] + with BHT-H were examined, and the aryloxide compound [Ti(N tBu)(Me 3[9]aneN 3)(BHT)][BAr 4F] was isolated (Ar F = C 6F 5). The X-ray structures of Ti(NR)(Me 3[9]aneN 3)Cl 2 (R = tBu, 2,6-C 6H 3Me 2, 2,6-C 6H 3Pr 2, Ph, C 6F 5) and Ti(NR)(Me 3[6]aneN 3)Cl 2 (R = 2,6-C 6H 3iPr 2, Ph, C 6F 5) are reported. The perfluorophenyl imido titanium compounds both exhibit well-defined supramolecular structures based on C⋯F intermolecular interactions. © 2006 American Chemical Society.

A family of coordination polymers formed by the reaction of copper(I) iodide with a range of angular bidentate or tridentate N-donor ligands is reported. The framework polymers [CuI(dpt)](infinity) 1 [dpt = 2,4-bis(4-pyridyl)-1,3,5-triazine], [CuI(dpb)](infinity) 2 [dpb = 1,4-bis-(4-pyridyl)-benzene], [(CuI)3(dpypy)2](infinity) 3, [CuI(dpypy)](infinity) 4 [dpypy = 3,5-bis(4-pyridyl)-pyridine], and [Cu3I3(pypm)](infinity) 5 [pypm = 5-(4-pyridyl)pyrimidine] have been prepared and structurally characterized. It was found that the angular nature of the dpypy and dpt ligands favors the formation of discrete (CuI)2 dimeric subunits as observed in [CuI(dpt).MeCN](infinity) 1 and [(CuI)3(dpypy)2](infinity) 3. In contrast, reaction with the linear ligand dpb affords [CuI(dpb)](infinity) 2 which incorporates a one-dimensional (CuI)(infinity) chain structure. Moreover, the additional donor available on the central ring of the dpypy ligand generates a novel two-dimensional bilayer structure in 3, in contrast to the one-dimensional ribbon structure observed in the case of 1. Interestingly, the bilayer structure of 3 additionally exhibits 2-fold interpenetration. The reaction of CuI with dpypy produces not only 3 but a further product [CuI(dpypy)](infinity) 4 that has been characterized as a one-dimensional chain constructed from trigonal-planar Cu(I) centers bridged by bidentate dpypy ligands. Compound 5, [Cu3I3(pypm)](infinity), exhibits a highly unusual three-dimensional structure in which the pypm ligand bridges two-dimensional brick-wall (CuI)(infinity) sheets.

A series of titanium(IV) adducts of an amido-tethered N-heterocyclic carbene (NHC) of the form Ti(L)(OiPr)n(Br)3-n (n = 1−3, L = tBuNHCH2CH2[C{NtBu(CHCH)N}]) have been synthesized and characterized. Structural characterization of the n = 2 complex shows marked bending of the two ligands cis (and perpendicular) to the plane of the NHC group in the direction of the carbene, suggestive of a pseudo-back-bonding interaction between adjacent ligands and the carbene p orbital, consistent with a bonding model recently proposed for d0 metal-NHC complexes. However, inspection of a space-filling model and the calculation of bond order using DFT methods suggest that the bending is due to repulsions between lone pairs on the adjacent π-donor ligands in the complexes and not any specific interaction between the NHC and cis π-donor ligands.

We have prepared and characterized a new phenol-based compartmental ligand (H(2)L) incorporating 1,4,7-triazacyclononane ([9]aneN(3)), and we have investigated its coordination behavior with Cu(II), Zn(II), Cd(II), and Pb(II). The protonation constants of the ligand and the thermodynamic stabilities of the 1:1 and 2:1 (metal/ligand) complexes with these metal ions have been investigated by means of potentiometric measurements in aqueous solutions. The mononuclear [M(L)] complexes show remarkably high stability suggesting that, along with the large number of nitrogen donors available for metal binding, deprotonated phenolic functions are also involved in binding the metal ion. The mononuclear complexes [M(L)] show a marked tendency to add a second metal ion to afford binuclear species. The formation of complexes [M(2)(H(2)L)](4+) occurs at neutral or slightly acidic pH and is generally followed by metal-assisted deprotonation of the phenolic groups to give [M(2)(HL)](3+) and [M(2)(L)](2+) in weakly basic solutions. The complexation properties of H(2)L have also been investigated in the solid state. Crystals suitable for X-ray structural analysis were obtained for the binuclear complexes [Cu(2)(L)](BF(4))(2).(1)/(2)MeCN (1), [Zn(2)(HL)](ClO(4))(3).(1)/(2)MeCN (2), and [Pb(2)(L)](ClO(4))(2).2MeCN (4). In 1 and 2, the phenolate O-donors do not bridge the two metal centers, which are, therefore, segregated each within an N(5)O-donor compartment. However, in the case of the binuclear complex [Pb(2)(L)](ClO(4))(2).2MeCN (4), the two Pb(II) centers are bridged by the phenolate oxygen atoms with each metal ion sited within an N(5)O(2)-donor compartment of L(2)(-), with a Pb.Pb distance of 3.9427(5) A.

The synthesis of new Pt(II) diimine complexes bearing perfluorinated thiolate ligands, Pt(II)(NN)(4-X-C(6)F(4)-S)(2), where NN = 2,2'-bipyridine or 1,10-phenanthroline and X = F or CN, is reported, together with an investigation of the nature and dynamics of their lowest excited states. A combined UV-vis, (spectro)electrochemical, resonance Raman, and time-resolved infrared (TRIR) study has suggested that the HOMO is mainly composed of thiolate(pi)/S(p)/Pt(d) orbitals and that the LUMO is largely localized on the pi*(diimine) orbital, thus revealing the [charge-transfer-to-diimine] nature of the lowest excited state. An enhancement of the thiolate ring vibrations, C-F vibrations, and the vibration of the CN-substituent on the thiolate moiety was observed in the resonance Raman spectra, whereas no such enhancement was seen for the nonfluorinated analogues. Thus, the introduction of fluorine substituents on the thiolate moiety probably leads to a more pronounced contribution of the intrathiolate modes to the HOMO compared to the analogous complexes with nonfluorinated thiolates. Furthermore, the introduction of the p-CN group into the thiolate moiety has allowed the dynamics of the lowest excited state of Pt(bpy)(4-CN-C(6)F(4)-S)(2) to be monitored by picosecond TRIR spectroscopy. The dynamics of the lowest [charge-transfer-to-diimine] excited state are governed by ca. 2-ps vibrational cooling and 35-ps back electron transfer.

A series of structurally related binuclear metallacycles [Cd(NO(3))(2)L](2), where L is an angular exo-bidentate ligand, have been synthesized. Each metallacycle contains two coordinatively unsaturated, chiral metal centers within a single molecule, and the assembly of these metallacycles into polymeric framework structures has been studied systematically for the first time. Stereoselective homochiral association of [Cd(NO(3))(2)L](2) leads to the formation of helical coordination polymers, whereas meso type association results in nonhelical chain structures. The type of stereoselective aggregation depends on the conditions of self-assembly as well as on ligand functionality. Both helical and nonhelical polymeric complexes have been isolated for the metallacycle [Cd(NO(3))(2)(2,4'-pyacph)](2) (2,4'-pyacph = 2,4'-(4-ethynylphenyl)bipyridyl). Homochiral association results in the formation of helical [Cd(NO(3))]( infinity ) chains which link the binuclear [Cd(NO(3))(2)(2,4'-pyacph)](2) metallacycles into racemic two-dimensional sheets which contain both P and M [Cd(NO(3))]( infinity ) helices. In contrast, meso-association leads to the formation of nonhelical one-dimensional chains. It is shown that the product of homochiral association is predominately formed at room temperature and that of meso-association is generated at elevated temperatures. Thus, it may be concluded that the homochiral association appears to be energetically less favorable than the meso-association, a conclusion that has been confirmed by theoretical calculations of the crystal lattice energy. Several high-yield syntheses of bipyridyl-type ligands used for metallacyclic assembly are also reported.

Hydrolysis of the PF6- anion during the reaction of AgPF6 with tetramethylhexathiaadamantane (hta) in MeOH leads to the crystallization of a coordination polymer, {[Ag3(hta)(PO2F2)3]}∞, in which hexanuclear [Ag(PO2F2)]6 cages are linked by tetramethylhexathiaadamantane molecules in a three-dimensional architecture. The unprecedented [Ag(PO2F2)]6 cages act as six-connecting units with approximately octahedral geometry, and the tetramethylhexathiaadamantane molecules form three-connecting units with approximately trigonal planar geometry to give a rare example of a metal-organic material with a rutile-like framework construction.

Rare earth carbenes exclusively exhibit Wittig-type reactivity with carbonyl compounds to afford alkenes. Here, we report that yttrium carbenes can effect regioselective ortho-C-H activation and sequential C-C and C-O bond formation reactions of aryl ketones to give iso-benzofurans and hydroxymethylbenzophenones. With MeCOPh, cyclotetramerization occurs giving a substituted cyclohexene. This demonstrates new rare earth carbene reactivity which complements existing Wittig-type reactivity.