Rational Syntheses and Serendipity: Complexes [LSnPtCl (SMe )] , [{LSnPtCl(SMe )} SnCl ], [(LSn) (PtCl )(PtClSnCl){LSn(Cl)OH}], and [O(SnCl) (SnL) ] with L=MeN(CH CMe O).

Syntheses and molecular structures of the dimeric tin-platinum complex [LSnPtCl (SMe )] (2), the tin-platinum clusters [{LSnPtCl(SMe )} SnCl )] (3) and [(LSn) (PtCl )(PtClSnCl)(LSnOHCl)] (6) (L=MeN(CH CMe O ) ), and of the unprecedented tin(II) aminoalkoxide-tin oxide chloride complex [O(SnCl) ⋅(SnL) ] (5) are reported. The compounds were characterized by NMR spectroscopy ( H, C, Sn, Pt), Sn Mössbauer spectroscopy (1-3, 6), electrospray ionization mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses (2⋅CH Cl , 3⋅2 C H O, 5, 6⋅3CH Cl ). The tin(II) aminoalkoxide [MeN(CH CMe O) Sn] (1) behaves like a neutral ligand, inserts into a Pt-Cl bond, or is involved in rearrangement reactions with the different behavior occurring even within one compound (3, 6).

Iron(II) Complexes of a Hemilabile SNS Amido Ligand: Synthesis, Characterization, and Reactivity.

We report an easily prepared bis(thioether) amine ligand, SNS, along with the synthesis, characterization, and reactivity of the paramagnetic iron(II) bis(amido) complex, [Fe(κ-SNS)] (1). Binding of the two different thioethers to Fe generates both five- and six-membered rings with Fe-S bonds in the five-membered rings (av 2.54 Å) being significantly shorter than those in the six-membered rings (av 2.

Intermolecular Aminocarbonylation of Alkenes using Concerted Cycloadditions of Iminoisocyanates.

The aminocarbonylation of alkenes is a powerful method for accessing the β-amino carbonyl motif that remains underdeveloped. Herein, the development of intermolecular aminocarbonylation reactivity of iminoisocyanates with alkenes is presented. This includes the discovery of a fluorenone-derived reagent, which was effective for many alkene classes and facilitated derivatization.

Structural and electronic trends for five coordinate 1(st) row transition metal complexes: Mn(ii) to Zn(ii) captured in a bis(iminopyridine) framework.

The preparation and characterization of a series of divalent 3d transition metal complexes supported by a tridentate planar bis(iminopyridine) ligand are reported. The complexes {2,6-[PhC[double bond, length as m-dash]N(tBu2C6H3)]2C5H3N}MBr2 (M = Mn, Fe, Co, Ni, Cu, Zn), 1-6, were characterized by single crystal X-ray structural studies revealing complexes with pentacoordinate distorted square pyramidal coordination environments. This assembly of complexes provided a unique array for examining the relationship between experimental structure and computed electronic structure.

Optical response of the Cu2 S2 diamond core in Cu2II(NGuaS)2 Cl2.

Density functional theory (DFT) and time-dependent DFT calculations are presented for the dicopper thiolate complex Cu2 (NGuaS)2 Cl2 [NGuaS=2-(1,1,3,3-tetramethylguanidino) benzenethiolate] with a special focus on the bonding mechanism of the Cu2 S2 Cl2 core and the spectroscopic response. This complex is relevant for the understanding of dicopper redox centers, for example, the CuA center. Its UV/Vis absorption is theoretically studied and found to be similar to other structural CuA models.

Selective Activation of Fluoroalkenes with N-Heterocyclic Carbenes: Synthesis of N-Heterocyclic Fluoroalkenes and Polyfluoroalkenyl Imidazolium Salts.

Selective reactions between nucleophilic N,N'-diaryl-heterocyclic carbenes (NHCs) and electrophilic fluorinated alkenes afford NHC fluoroalkenes in high yields. These stable compounds undergo efficient and selective fluoride abstraction with Lewis acids to give polyfluoroalkenyl imidazolium salts. These salts react at Cβ with pyrrolidine to give ammonium fluoride-substituted salts, which give rise to conjugated imidazolium-enamine salts through loss of HF.

Intramolecular Alkene Aminocarbonylation Using Concerted Cycloadditions of Amino-Isocyanates.

The ubiquity of nitrogen heterocycles in biologically active molecules challenges synthetic chemists to develop a variety of tools for their construction. While developing metal-free hydroamination reactions of hydrazine derivatives, it was discovered that carbazates and semicarbazides can also lead to alkene aminocarbonylation products if nitrogen-substituted isocyanates (N-isocyanates) are formed in situ as reactive intermediates. At first this reaction required high temperatures (150-200 °C), and issues included competing hydroamination and N-isocyanate dimerization pathways.

Mononuclear, Dinuclear, and Trinuclear Iron Complexes Featuring a New Monoanionic SNS Thiolate Ligand.

The new tridentate ligand, S(Me)N(H)S = 2-(2-methylthiophenyl)benzothiazolidine, prepared in a single step from commercial precursors in excellent yield, undergoes ring-opening on treatment with Fe(OTf)2 in the presence of base affording a trinuclear iron complex, [Fe3(μ2-S(Me)NS(-))4](OTf)2 (1) which is fully characterized by structural and spectroscopic methods. X-ray structural data reveal that 1 contains four S(Me)NS(-) ligands meridionally bound to two pseudooctahedral iron centers each bridged by two thiolates to a distorted tetrahedral central iron. The combined spectroscopic (UV-vis, Mössbauer, NMR), magnetic (solution and solid state), and computational (DFT) studies indicate that 1 includes a central, high-spin Fe(II) (S = 2) with two low-spin (S = 0) peripheral Fe(II) centers.

Perfluoroalkyl Cobalt(III) Fluoride and Bis(perfluoroalkyl) Complexes: Catalytic Fluorination and Selective Difluorocarbene Formation.

Four perfluoroalkyl cobalt(III) fluoride complexes have been synthesized and characterized by elemental analysis, multinuclear NMR spectroscopy, X-ray crystallography, and powder X-ray diffraction. The remarkable cobalt fluoride (19)F NMR chemical shifts (-716 to -759 ppm) were studied computationally, and the contributing paramagnetic and diamagnetic factors were extracted. Additionally, the complexes were shown to be active in the catalytic fluorination of p-toluoyl chloride.

A T-shaped Ni[κ-(CF)-] NHC complex: unusual C -F and M-C bond functionalization reactions.

A T-shaped octafluoronickelacyclopentane-NHC complex is prepared and characterized. While the solid-state structure includes a weak isopropyl-CH agostic interaction, the reactivity of this complex with Lewis- and Brønsted acids is clearly enhanced by its low coordination number. Reaction with MeSiOTf, for example, yielded a rare metal-heptafluorocyclobutyl complex whereas carboxylic acids gave substitution at the α-carbon and/or Ni-C bond protonolysis to afford thermally robust 4-octafluorobutyl Ni complexes.

Coinage metal complexes supported by a "PN(3)P" scaffold.

A series of monovalent group 11 complexes, [2,6-{Ph2PNMe}2(NC5H3)]CuBr 1, [2,6-{Ph2PNMe}2(NC5H3)]CuOTf 2, [2,6-{Ph2PNMe}2(NC5H3)]AgOTf 3, and [2,6-{Ph2PNMe}2(NC5H3)](AuCl)24, supported by a neutral PN(3)P ligand have been synthesized and characterized by multinuclear NMR and single crystal X-ray diffraction studies. The variation of the coordination properties were analyzed and electronic structure calculations have been carried out to provide insight on the bonding details in these complexes. The Cu(I) complexes displayed an unusual coordination geometry with a tridentate pincer ligand and an overall four coordinate trigonal pyramidal geometry.

Ambivalent binding between a radical-based pincer ligand and iron.

A complex exhibiting valence delocalization was prepared from 3,5-bis(2-pyridyl)-1,2,4,6-thiatriazinyl (), an inherently redox active pincer-type ligand, coordinated to iron ( ()). Complex can be prepared via two routes, either from the reaction of the neutral radical with FeCl2 or by treatment of the anionic ligand () with FeCl3, demonstrating its unique redox behaviour. Electrochemical studies, solution absorption and solid-state diffuse reflectance measurements along with X-ray crystallography were carried out to elucidate the molecular and solid-state properties.

How Innocent are Potentially Redox Non-Innocent Ligands? Electronic Structure and Metal Oxidation States in Iron-PNN Complexes as a Representative Case Study.

Herein we present a series of new α-iminopyridine-based iron-PNN pincer complexes [FeBr2LPNN] (1), [Fe(CO)2LPNN] (2), [Fe(CO)2LPNN](BF4) (3), [Fe(F)(CO)2LPNN](BF4) (4), and [Fe(H)(CO)2LPNN](BF4) (5) with formal oxidation states ranging from Fe(0) to Fe(II) (LPNN = 2-[(di-tert-butylphosphino)methyl]-6-[1-(2,4,6-mesitylimino)ethyl]pyridine). The complexes were characterized by a variety of methods including (1)H, (13)C, (15)N, and (31)P NMR, IR, Mössbauer, and X-ray photoelectron spectroscopy (XPS) as well as electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectroscopy, SQUID magnetometry, and X-ray crystallography, focusing on the assignment of the metal oxidation states. Ligand structural features suggest that the α-iminopyridine ligand behaves as a redox non-innocent ligand in some of these complexes, particularly in [Fe(CO)2LPNN] (2), in which it appears to adopt the monoanionic form.

Conjugated Polymers à la Carte from Time-Controlled Direct (Hetero)Arylation Polymerization.

Direct (hetero)arylation polymerization (DHAP) shows great promise for simple, cheap, and environmentally benign preparation of conjugated polymers, but seems to involve a lack of selectivity when different aromatic C-H bonds are present. We report that some time-controlled DHAP reactions can yield well-defined and processable semiconducting polymers. Following these procedures, various aromatic compounds have been efficiently polymerized, including 2,7-dibromofluorene, 2,7-dibromocarbazole, 1,4-dibromobenzene, bithiophene, dithienyl-benzothiadiazole, and diketopyrrolopyrrole derivatives.

Tris-heteroleptic ruthenium-dipyrrinate chromophores in a dye-sensitized solar cell.

Two novel tris-heteroleptic Ru-dipyrrinates were prepared and tested as sensitizers in the dye-sensitized solar cell (DSSC). Under AM 1.5 sunlight, DSSCs employing these dyes achieved power conversion efficiencies (PCEs) of 3.

Synthesis, characterization, X-ray crystal structure, DFT calculations, and catalytic properties of a dioxidovanadium(V) complex derived from oxamohydrazide and pyridoxal: a model complex of vanadate-dependent bromoperoxidase.

A vanadium(V) complex with the formula [Et3NH][V(V)O2(sox-pydx)] with a new tridentate ligand 2-[2-[[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl]methylene]hydrazinyl]-2-oxoacetamide (soxH-pydxH), obtained by condensation of oxamohydrazide and pyridoxal (one of the forms of vitamin B6), has been synthesized. The compound was characterized by various analytical and spectroscopic methods, and its structure was determined by single-crystal X-ray diffraction technique. Density functional theory (DFT) and time-dependent DFT calculations were used to understand the electronic structure of the complex and nature of the electronic transitions observed in UV-vis spectra.

Chromium-chromium interaction in a binuclear mixed-valent Cr(I)-Cr(II) complex.

A mixed-valent Cr(I)-Cr(II) binuclear complex, {κ(1),κ(2),κ(3)-N,P,P-cyclo[(Ph)PCH2N(CH2Ph)CH2]}2(CrCl2)[Cr(μ-Cl)(AlClMe2)]·4toluene (1), of a P2N2 cyclic ligand was obtained upon treatment of the chromium precursor with alkylaluminum. Complex 1 was accessible from either its trivalent or divalent precursors, and density functional theory calculations revealed the presence of only σ- and π-orbital interactions in the Cr-Cr bond.

Anisotropic covalency contributions to superexchange pathways in type one copper active sites.

Type one (T1) Cu sites deliver electrons to catalytic Cu active sites: the mononuclear type two (T2) Cu site in nitrite reductases (NiRs) and the trinuclear Cu cluster in the multicopper oxidases (MCOs). The T1 Cu and the remote catalytic sites are connected via a Cys-His intramolecular electron-transfer (ET) bridge, which contains two potential ET pathways: P1 through the protein backbone and P2 through the H-bond between the Cys and the His. The high covalency of the T1 Cu-S(Cys) bond is shown here to activate the T1 Cu site for hole superexchange via occupied valence orbitals of the bridge.

Identifying Homocouplings as Critical Side Reactions in Direct Arylation Polycondensation.

Homocouplings are identified as major side reactions in direct arylation polycondensation (DAP) of 4,7-bis(4-hexyl-2-thienyl)-2,1,3-benzothiadiazole (TBT) and 2,7-dibromo-9-(1-octylnonyl)-9-carbazole (CbzBr). Using size exclusion chromatography (SEC) and NMR spectroscopy, we demonstrate that both TBT and Cbz homocouplings occur at a considerable extent. TBT homocoupling preferentially occurs under phosphine-free conditions but can be suppressed in the presence of a phosphine ligand.

Near-IR photoresponse of ruthenium dipyrrinate terpyridine sensitizers in the dye-sensitized solar cells.

Coordination of bidentate 5-pentafluorophenyldipyrrinate (pfpdp) or 5-(2-thienyl)dipyrrinate (2-tdp) to a Ru(II) center bearing 2,2':6',2″-terpyridine-4,4',4″-tricarboxylate (tctpy) and a NCS(-) ligand results in strongly light-absorbing complexes [Ru(tctpy)(L)(NCS)] (L = pfpdp or 2-tdp). Anchored to a mesoporous TiO2 electrode, these complexes afford a photoaction spectral response at wavelengths of up to 950 nm, one of the most red-shifted values reported to date for molecular dyes in the dye-sensitized solar cell (DSSC).

Molecular and electronic structures of complexes containing 1-(2-pyridylazo)-2-phenanthrol (PAPL): revisiting a redox-active ligand.

Herein we report the molecular structures and electronic properties of neutral, homoleptic, six-coordinate complexes of the general formula M(PAPL)2, where PAPL is the monoanion of 1-(2-pyridylazo)-2-phenanthrol (M = Mn, Ni, Zn). Although, the coordination chemistry of PAPL has been investigated in a few previous reports in the 1970s and 1980s, there are, to our knowledge, no reported single crystal X-ray diffraction studies of any complexes, or any other electronic property or computational studies of complexes containing the PAPL anion until now. The electronic structures of the complexes are probed with a combination of cyclic voltammetry, UV-vis spectroscopy, and spectroelectrochemical measurements.

Influence of the ligand field on slow magnetization relaxation versus spin crossover in mononuclear cobalt complexes.

The electronic and magnetic properties of the complexes [Co(terpy)Cl2 ] (1), [Co(terpy)(NCS)2 ] (2), and [Co(terpy)2 ](NCS)2 (3) were investigated. The coordination environment around Co(II) in 1 and 2 leads to a high-spin complex at low temperature and single-molecule magnet properties with multiple relaxation pathways. Changing the ligand field and geometry with an additional terpy ligand leads to spin-crossover behavior in 3 with a gradual transition from high spin to low spin.

Diastereoselective hydrogen-transfer reactions: an experimental and DFT study.

Radical reductions of halogenated precursors bearing a heterocycle exo (α) to the carbon-centered radical proceed with enhanced anti-selectivity, a phenomenon that we termed "exocyclic effect". New experimental data and DFT calculations at the BHandHLYP/TZVP level demonstrate that the origin of the exocyclic effect is linked to the strain energy required for a radical intermediate to reach its reactive conformation at the transition state (ΔE(≠)(strain)). Furthermore, radical reductions of constrained THP systems indicate that high 2,3-anti inductions are reached only when the radical chain occupies an equatorial orientation.

A study of exocyclic radical reductions of polysubstituted tetrahydropyrans.

Exocyclic radical reductions were thoroughly investigated in the context of the synthesis of polysubstituted tetrahydropyrans, which are found in numerous macrolides. The radical precursors studied herein were generated by tandem cycloetherification and iodoetherification reactions or, alternatively, by semicyclic acetals substitutions. DFT calculations (BHandHLYP/TZVP) performed at the transition-state level for the hydrogen radical delivery are in good accordance with the experimental data and enabled the identification of important conformational factors that govern the selectivities obtained.

Noncovalent interactions of metal cations and arenes probed with thallium(I) complexes.

The synthesis, characterization, and computational analysis of Tl(I) complexes bearing the bis(imino)pyridine scaffold, [{ArN═CPh}2(NC5H3)]Tl(+)(OTf)(-) (Ar = 2,6-Et2C6H33, 2,5-(t)Bu2C6H3, 4), are reported. The cations of these species showed long Tl-N and Tl-OTf distances indicating only weak or no ligand coordination. Computational analysis of the interactions between the Tl cation and the ligands (orbital populations, bond order, and energy decomposition analysis) point to only minimal covalent interactions of the cation with the ligands.