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The COVID-19 pandemic highlighted the inaccessibility of quick and affordable clinical diagnostics. This led to increased interest in creating low-cost portable electrochemical (EC) devices for environmental monitoring and clinical diagnostics. One important perspective is to develop new fabrication methods for functional and low-cost electrode chips. Techniques, such as electron beam and photolithography, allow precise and high-resolution electrode fabrication; however, they are costly and can be time-consuming. More recently, fused deposition modeling three-dimensional (3-D) printing is being used as an alternative fabrication technique due to the low-cost of the printer and rapid prototyping capability. In this study, we explore enhancing the conductivity of 3-D printed working electrodes with EC gold deposition. Two commercial conductive filament brands were used and investigated to fabricate electrode chips. Furthermore, strategies to apply epoxy glue and conductive silver paint were investigated to control the electrode surface area and ensure good electrical connection. This device enables detection at drinking water concentration thresholds. The practical application of the fabricated electrodes is demonstrated by detecting Cu

Mono- and dianion species of 1,8-naphthalene diamide 2 were generated under sec-BuLi/TMEDA conditions and trapped with a variety of electrophiles to give 2- and 2,7- substituted products 3 and 4. U...

A phosphaguanidine [Me2NC(PPh2)=N i Pr], the analogous guanidine [Me2NC(NPh2)=N i Pr], and their hydrochloride (HCl) salts were prepared to study the influence of substituting a phosphorus atom for a nitrogen atom on the basicity of the two compounds and the bonding in their conjugate acids. The pK a values of both HCl salts were measured in acetonitrile by NMR titration. Surprisingly, the substitution of P for N has essentially no effect on basicity even though the geometry at that atom is changed. The presence of phenyl substituents in the protonated guanidine reduces the resonance in the CN3 core, whereas poor orbital overlap between P and C reduces the resonance in the N2CP core of the protonated phosphaguanidine. The neutral phosphaguanidine binds to a Cu(I) halide through both the Nimine and the P, which suggested that the basic N atom on the bound ligand may have little utility as a Brønsted base. Fortunately, however, a Cu(I) halide complex of the protonated phosphaguanidine is stable. Thus, the tendency of the basic N to bind to metals does not proscribe it serving as a metal-proximate Brønsted base.

Preparation of formamides by CO2 hydrogenation requires an efficient catalyst and temperatures around 100 °C or higher, but most catalysts reported so far incorporate rare and toxic precious metals...

We report the synthesis and solid-state 17O NMR characterization of three 17O-labeled oxiranes: (2S*,3S*)-2,3-bis(4-nitrophenyl)-[17O]oxirane, (2S*,3R*)-2,3-bis(4-nitrophenyl)-[17O]oxirane, and 2,2,3-triphenyl-[17O]oxirane. In addition, we have determined the crystal structure of (2S*,3R*)-2,3-bis(4-nitrophenyl)oxirane by X-ray crystallography. When the experimentally determined 17O NMR tensors for oxiranes (where the C–O–C bond angle is about 60°) are compared with those for dimethyl ether (where the C–O–C bond angle is 113°) and other R–O–R′ functional groups, we found that the highly constrained geometry of oxiranes results in distinct tensor orientations in the molecular frame of reference. The experimental results are complemented by quantum chemical computations. This study represents the first time that 17O chemical shift and quadrupole coupling tensors are simultaneously determined for oxirane compounds.

Herein, we describe the synthesis of a toroidal Au

Mono- and dianion species of 1,8-naphthalene diamide

Preparation of formamides by CO

The investigations of bismuth halide chemistry in DMSO/MeOH solutions led to the discovery of a new solvent-stabilized compound with a chemical formula of Cs3BiBr6·3DMSO. In addition, a new phase o...

Phosphaamidine metal complexes Rh2Cl2[Ph2PC(Ph)NPh]2μ-CO (1), RuCl2[Ph2PC(Ph)N(Ph)]2 (2), [Rh{iPr2PC(Ph)NiPr}(COD)]BF4 (3), and RuCl2[iPr2PC(Ph)NiPr](DMSO)2 (4) are prepared by combining phosphaamidines Ph2P-C(Ph)NPh and iPr2P-C(Ph)NiPr (1,3-P,N) with their corresponding metal ions. Complexes 1 and 2 are stable in air while 3 and 4 are stable under inert conditions. For further comparison of structure and stability, a Ru(II) phosphaguanidine complex, RuCl2[Me2NC(PPh2)NiPr](DMSO)2 (6) was prepared. Complex 6 is stable in air and in the presence of water. The structures of the phosphaamidine and phosphaguanidine complexes, determined using single crystal X-ray diffraction, revealed P,N bidentate coordination. While all five complexes have some activity as precatalysts, complex 6 was the most active.

Pseudo-octahedral complexes built on chelating ligands offer valuable isomeric properties such as the formation of fac vs mer isomers, and Λ vs Δ enantiomers. This article discusses factors guiding the fac vs mer selection of complexes built from the triazolyl-pyridine platform bearing a benzyl substituent, in conjunction with labile metal ions such as zinc(II), iron(II), and nickel(II). Critical parameters that are explored include the geometrical flexibility of the individual metal ion, and the nature of the counteranion. In essence, it was observed that ions which can withstand significant distortions in their first coordination sphere, such as zinc(II), generally prefer forming the mer isomer irrespective of the counteranion, whereas ions with more restricted geometry, such as iron(II), are directed either to a fac arrangement by small, tetrahedral anions such as tetrafluoroborate or perchlorate or to a mer organization by counteranions of lower symmetry, such as triflate. The molecular interactions o...

Two nickel(II) complexes, [Ni(acac) 2 (dmpeO 2 )] n ·2CHCl 3 ( 1 ) and [(Ni(acac)(MeO)(MeOH)] 4 ( 2 ) (acac − = pentane-2,4-dionato) have been synthesized and characterized by elemental analysis, FT-IR spectroscopy, and single crystal X-ray diffraction. The geometries around the central nickel(II) ion are distorted octahedral in both complexes. The equatorial plane includes four oxygen donor atoms of two acetylacetonato ligands and the axial positions are occupied by two oxygen atoms of two dmpeO 2 ligands. Complex 1 has a polymeric chain structure in the solid state, while complex 2 has a tetranuclear cubane structure. These complexes are the first reported examples of polymeric and tetranuclear structures of Ni((II) containing acac - ligand. Neither complex is catalytically active for the hydrogenation of CO 2 to formamide, even though a mixture of Ni(acac) 2 and dmpe form a very active in situ catalyst together.

Tambjamines are natural products that consist of a conserved bipyrrole core functionalized with different imines giving rise to many derivatives. The core structure of tambjamines allows ion coordination through the nitrogen atoms, which is a key aspect in many of their observed antimicrobial, anticancer, and antimalarial bioactivities. Minor variances in the compound structure have a considerable impact on the potency of these activities, so identifying new analogues is valuable for maximizing tambjamine biological potential. In this work, we describe the isolation and structure elucidation of the first naturally occurring macrocyclized tambjamine, tambjamine MYP1, from the marine microbe Pseudoalteromonas citrea. We also compare the apparent pK(a) of cyclic and linear tambjamine analogues and discuss how structural strain may effect the compound's ion coordination abilities.

A family of ferrocenylborane compounds has been synthesized with the aim to examine the impact of the linker units on the mutual influence of the borane and ferrocene units on electronic and electrochemical properties. Fluoride titrations were performed on all compounds. The monoferrocenyl compounds 1–3 and the diferrocenyl compound 4 showed expected fluoride binding, while compounds 5 and 6 do not or only weakly respond to the addition of fluoride ions, as indicated by UV–vis and NMR spectroscopic data. Cyclic voltammetry studies showed that there is no electronic communication between the ferrocenyl units in compounds that contain two or three ferrocenyl units. The linker units were found to have a distinct impact on the electronic and electrochemical properties of the borane-linked/containing ferrocene molecules.

The Pd-catalyzed regioselective C–H activation/arylation, /iodination, and/acetoxylation reactions of 4-arylpyrimidines using aryl iodides, N-iodosuccinimide, and (diacetoxyiodo)benzene respectively as coupling partners are described. Suzuki–Miyaura coupling and Sonogashira reactions of the resulting aryl iodides are demonstrated. The scalability of the C–H activation/functionalization starting with readily accessible 4-aryl pyrimidines is also reported.

A 1-phosphonium-8-borane-decorated naphthalene molecule 2 has been found to react with N,N'-dimethylimidazol-2-ylidene (IMe), a popular member of the N-heterocyclic carbene (NHC) family, which converts it into two vinyl-amine fragments one of which is trapped between the phosphonium and borane unit by the formation of a C-C and a B-N bond. The same reactivity was not observed for larger NHC molecules. Control experiments and mechanistic studies have established the involvement of an ylide-borane molecule and an imidazolium salt in addition to IMe carbene in this new transformation of an NHC.

Transformation of 1-t-Boc-4-methoxyindole-3-glucosinolate under acidic conditions yielded the potent phytoalexin rapalexin A, providing its first biomimetic synthesis via Lossen type rearrangement, while a novel 1-thioimidocarbonyl-β-d-glucopyranose heterocyclic system was obtained under basic conditions via Neber type rearrangement.

The interaction between carbon dioxide (CO2) and amidines such as 1,8-diazabicyclo[5.4.0]undecane (DBU) has been extensively studied, but the reaction of isovalent CS2 with such bases has been largely ignored, apart from a single crystallography report. Acyclic acetamidines are cleaved by CS2 at room temperature to give an isothiocyanate and a thioacetamide. Because the pathway to that cleavage involves a rotation that is difficult for cyclic amidines, the reaction of CS2 with cyclic amidines produces an entirely different product: a cyclic carbamic carboxylic trithioanhydride structure. The path to that product involves sp3 C-H activation leading to the formation of a new C–C bond at a carbon α to the central carbon of the amidine group. Alkylation and ring-opening of the cyclic carbamic carboxylic trithioanhydride has also been demonstrated under ambient conditions.

Dimeric rhodium N-heterocyclic carbene complexes are demonstrated to be effective catalyst precursors for directed C-H borylation reactions at room temperature. The reactions are highly selective for mono-borylation and can be combined with a one-pot Suzuki-Miyaura coupling to give C-H arylation products with exclusive selectivity for mono-arylation without the requirement for steric blocking groups.

Here we report the structure and optical properties of a new Cu–cysteamine complex (Cu–Cy) with a formula of Cu3Cl(SR)2 (R = CH2CH2NH2). This Cu–Cy has a different structure from a previous Cu–Cy complex, in which both thio and amine groups from cysteamine bond with copper ions. Single-crystal X-ray diffraction and solid-state nuclear magnetic resonance results show that the oxidation state of copper in Cu3Cl(SR)2 is +1 rather than +2. Further, Cu3Cl(SR)2 has been observed to show intense photoluminescence and X-ray excited luminescence. More interesting is that Cu3Cl(SR)2 particles can produce singlet oxygen under irradiation by light or X-ray. This indicates that Cu3Cl(SR)2 is a new photosensitizer that can be used for deep cancer treatment as X-ray can penetrate soft tissues. All these findings mean that Cu3Cl(SR)2 is a new material with potential applications for lighting, radiation detection and cancer treatment.

The interaction between carbon dioxide (CO2) and amidines such as 1,8-diazabicyclo[5.4.0]undecane (DBU) has been extensively studied, but the reaction of isovalent CS2 with such bases has been largely ignored, apart from a single crystallography report. Acyclic acetamidines are cleaved by CS2 at room temperature to give an isothiocyanate and a thioacetamide. Because the pathway to that cleavage involves a rotation that is difficult for cyclic amidines, the reaction of CS2 with cyclic amidines produces an entirely different product: a cyclic carbamic carboxylic trithioanhydride structure. The path to that product involves sp3 C-H activation leading to the formation of a new C–C bond at a carbon α to the central carbon of the amidine group. Alkylation and ring-opening of the cyclic carbamic carboxylic trithioanhydride has also been demonstrated under ambient conditions.

Salt-metathesis reactions between dilithioferrocene (Li(2)fc·2/3tmeda) and intramolecularly coordinated aluminum and gallium species RECl(2) [R = 5-Me(3)Si-2-(Me(2)NCH(2))C(6)H(3); E = Al (2a), Ga (2b); and R = (2-C(5)H(4)N)Me(2)SiCH(2); E = Al (3a), Ga (3b)] gave respective [1.1]ferrocenophanes ([1.1]FCPs). Those obtained from 2a and 2b, respectively, were isolated as analytically pure compounds and fully characterized including single-crystal X-ray structure determinations [4a (Al): 43%; 4b (Ga): 47%]. Bis(ferrocenyl) compounds of the type REFc(2) [R = 5-Me(3)Si-2-(Me(2)NCH(2))C(6)H(3); E = Al (5a), Ga (5b); and R = (2-C(5)H(4)N)Me(2)SiCH(2); E = Al (6a), Ga (6b)] and R(2)SiFc(2) [R = Me (7(Me)); Et (7(Et))] were prepared, starting from respective element dichlorides and lithioferrocene (LiFc). Molecular structures of 6a, 7(Me), and 7(Et) were solved by single-crystal X-ray analyses. One of the two Fc moieties of 6a was bent toward the open coordination site of the aluminum atom. The measured dip angles α* of the two independent molecules in the asymmetric unit were 11.9(5) and 13.3(5)°, respectively. The redox behavior of [1.1]FCPs 4 and bis(ferrocenyl) species 5, 6, 7, and (Mamx)EFc(2) [Mamx = 2,4-tBu(2)-6-(Me(2)NCH(2))C(6)H(2); E = Al (8a), Ga (8b)] were investigated with cyclic voltammetry. While all gallium and silicon compounds gave meaningful and interpretable data, all aluminum compounds were problematic with the exception of 8a. Aluminum species, compared to respective gallium species, are more sensitive and, presumably, fluoride ions or residual water from the electrolyte and solvent are causing degradation. The splitting between the formal potentials for bis(ferrocenyl) species was significantly smaller (5b, 6b, and 8b: ΔE°' = 0.138-0.159 V) than that of the [1.1]FCP 4b (ΔE°' = 0.309 V). These results were explained by assuming an electrostatic interaction between the two iron centers; differences between bis(ferrocenyl) species and [1.1]FCPs are likely due to a more effective solvation of Fe-containing moieties in the more flexible bis(ferrocenyl) species.

The synthesis and characterization of ferrocene-based oligomers that contained two different elements (Si and Sn) as alternating bridges is described for the first time. The salt-metathesis reaction of R(2) Si[(C(5) H(4) )Fe(C(5) H(4) Li)](2) (R=Me, Et) with R'(2) SnCl(2) (R'=Me, nBu, tBu) afforded a mixture of oligomers (6(Me) SnMe(2), 6(Et) SnMe(2), 6(Me) SnnBu(2), 6(Et) SnnBu(2), 6(Me) SntBu(2), and 6(Et) SntBu(2)). These oligomers were characterized by (1) H, (13) C, (29) Si, and (119) Sn NMR spectroscopy and by mass spectrometry. MS (MALDI-TOF) studies of 6(Et) SnMe(2) revealed the presence of linear (l) and cyclic (c) species that contained up to 20 ferrocene moieties. The molecular weights of the polymers were determined by gel-permeation chromatography (GPC) and by dynamic-light scattering (DLS). GPC analysis revealed average molecular weights of 2100-6300 Da with respect to polystyrene as a standard. DLS analysis yielded very similar results. Some compounds, c-(6(Me) SnMe(2) )(1), c-(6(Me) SntBu(2))(2), c-(6(Et) SnMe(2))(1), c-(6(Et) SntBu(2))(2), l-(6(Me) SnnBu(2) )(2), and l-(6(Me) SnnBu(2))(3), which contained up to six ferrocene moieties, were isolated in their pure form either by column chromatography or by crystallization. The Si- and Sn-bridged macrocycles that contained four ferrocene units (c-(6(Me) SntBu(2))(2) and c-(6(Et) SntBu(2))(2)) were structurally characterized by single-crystal X-ray analysis.

Two different ligands equipped with pyridine donor moieties, (2-H4C5N)(Me3Si)2C (R′) and (2-H4C5N)(Me3Si)(Me)C (R″), were applied in the preparation of aluminum and gallium dihalides that could be employed in salt metathesis reactions with 1,1′-dilithioferrocene. R′GaCl2 (1) was accessible from LiR′ and GaCl3 (21%), whereas the respective aluminum compound R′AlCl2 (3Cl) and its bromine analogue R′AlBr2 (3Br) could only be prepared through the intermediate species R′AlMe2 (2) by the addition of Me3SnCl and Br2, respectively. An improved synthesis of the ligand precursor R″H, (2-H4C5N)(Me3Si)(Me)CH), is described. Attempted syntheses of R″AlX2 starting from LiR″ and AlCl3 or ClAlMe2 gave the bis-ligand compounds R″2AlCl (4) and R″2AlMe (6), respectively. As deduced from proton NMR spectroscopy, the formation of 6 proceeded through the intermediate R″AlMe2 (5) and was facilitated in the presence of tmeda. The formation of 4 and 6, respectively, is diastereospecific, as only rac isomers were formed (R,R-Λ and...

Dichlorohydroquinone dioxygenase (PcpA) is the ring-cleavage enzyme in the PCP biodegradation pathway in Sphingobium chlorophenolicum strain ATCC 39723. PcpA dehalogenates and oxidizes 2,6-dichlorohydroquinone to form 2-chloromaleylacetate, which is subsequently converted to succinyl coenzyme A and acetyl coenzyme A via 3-oxoadipate. Previous studies have shown that PcpA is highly substrate-specific and only uses 2,6-dichlorohydroquinone as its substrate. In the current study, we overexpressed and purified recombinant PcpA and showed that PcpA was highly alkaline resistant and thermally stable. PcpA exhibited two activity peaks at pH 7.0 and 10.0, respectively. The apparent k(cat) and K(m) were measured as 0.19 ± 0.01 s(-1) and 0.24 ± 0.08 mM, respectively at pH 7.0, and 0.17 ± 0.01 s(-1) and 0.77 ± 0.29 mM, respectively at pH 10.0. Electron paramagnetic resonance studies showed rapid oxidation of Fe(II) to Fe(III) in PcpA and the formation of a stable radical intermediate during the enzyme catalysis. The stable radical was predicted to be an epoxide type dichloro radical with the unpaired electron density localized on C3.

Dichlorohydroquinone dioxygenase (PcpA) is the ring-cleavage enzyme in the PCP biodegradation pathway in Sphingobium chlorophenolicum strain ATCC 39723. PcpA dehalogenates and oxidizes 2,6-dichlorohydroquinone to form 2-chloromaleylacetate, which is subsequently converted to succinyl coenzyme A and acetyl coenzyme A via 3-oxoadipate. Previous studies have shown that PcpA is highly substrate-specific and only uses 2,6-dichlorohydroquinone as its substrate. In the current study, we overexpressed and purified recombinant PcpA and showed that PcpA was highly alkaline resistant and thermally stable. PcpA exhibited two activity peaks at pH 7.0 and 10.0, respectively. The apparent kcat and Km were measured as 0.19 ± 0.01 s-1 and 0.24 ± 0.08 mM, respectively at pH 7.0, and 0.17 ± 0.01 s-1 and 0.77 ± 0.29 mM, respectively at pH 10.0. Electron paramagnetic resonance studies showed rapid oxidation of Fe(II) to Fe(III) in PcpA and the formation of a stable radical intermediate during the enzyme catalysis. The stable radical was predicted to be an epoxide type dichloro radical with the unpaired electron density localized on C3.

Bis(cyclopentadienyl)aluminum and -gallium species of the type (Pytsi)ECp2 [E = Al (2a), Ga (2b); Pytsi = C(SiMe3)2SiMe2(2-C5H4N)] have been prepared from NaCp and respective dichlorides (Pytsi)ECl2 in isolated yields of 65% (2a) and 83% (2b). In addition to applying standard methods of characterization (NMR spectroscopy, CHN analysis, and MS), the molecular structures of both compounds were solved by single-crystal X-ray crystallography. Reactions between 2a or 2b with Zr(NMe2)4 in benzene, followed by addition of an excess of ClSiMe3, gave the first ansa-zirconocene dichlorides with aluminum (4a) or gallium (4b) in bridging position. The gallium compound 4b was isolated in a yield of 40% and characterized by NMR spectroscopy, CHN analysis, and mass spectrometry. The aluminum species 4a could not be obtained in an analytically pure form; it was characterized by NMR spectroscopy, and its molecular structure was determined by single-crystal X-ray analysis. The angle between the two planes of the Cp ligands...

The production of phytoalexins in Thellungiella halophila exposed to UV-radiation and NaCl was investigated over a period of 8 days. UV-radiation induced substantially larger quantities of wasalexins A and B than NaCl irrigation or CuCl2 spray. Isolation of two metabolites and their chemical structure determination using X-ray diffraction analysis provided the phytoalexins biswasalexins A1 and A2, that resulted from head-to-tail photodimerization of wasalexin A. The production of biswasalexins A1 and A2 in stressed T. halophila, as well as their chemical synthesis and antifungal activity are reported. Biswasalexins A1 and A2 (60 nmol/g and 15 nmol/g fresh wt, respectively, 2 days after UV elicitation) are cruciferous phytoalexins whose formation in planta appears to result from a photochemical reaction, which might protect the plant from fungal attack and UV-radiation.

A series of 3,5-bis(benzylidene)-4-piperidones 3 were converted into the corresponding 3,5-bis(benzylidene)-1-phosphono-4-piperidones 5 via diethyl esters 4. The analogues in series 4 and 5 displayed marked growth inhibitory properties toward human Molt 4/C8 and CEM T-lymphocytes as well as murine leukemia L1210 cells. In general, the N-phosphono compounds 5, which are more hydrophilic than the analogues in series 3 and 4, were the most potent cluster of cytotoxins, and, in particular, 3,5-bis-(2-nitrobenzylidene)-1-phosphono-4-piperidone 5 g had an average IC(50) value of 34 nM toward the two T-lymphocyte cell lines. Four of the compounds displayed potent cytotoxicity toward a panel of nearly 60 human tumor cell lines, and nanomolar IC(50) values were observed in a number of cases. The mode of action of 5 g includes the induction of apoptosis and inhibition of cellular respiration. Most of the members of series 4 as well as several analogues in series 5 are potent multi-drug resistance (MDR) reverting compounds. Various correlations were noted between certain molecular features of series 4 and 5 and cytotoxic properties, affording some guidelines in expanding this study.

The synthesis, characterization and crystal structure of the title compound, N-ferrocenoyl-L-Pro-L-Leu-Gly-OMe (Fc-PLG), were reported in this paper. The title compound crystallized in a monoclinic system, space group C2 with Z = 4, a = 20.803(3) Å, b = 6.4428(4) Å, c = 20.557(2) Å, α = 90°, β = 115.498(5)°, γ = 90°; R = 0.0451. The Cp rings in the ferrocenoyl group are nearly coplanar, making a dihedral angle of 178.2 (4)°, while the substituted cyclopentadienyl ring and the proline ring are virtually coplanar with a very small twist angle of 14.0°. Strong hydrogen bonds between the Gly amide group N13 and the Pro carbonyl group O11 (d (N … O) = 2.835 Å) make the molecules fold into a β-turn conformation.

Lithiation of 2-dimethylaminoindene followed by quenching with [( R )-(1,1′-binaphthalene-2,2′-diyl)]chlorophosphite and treatment with triethylamine afforded the crystallographically characterized enantiopure P,N-indene 3 in 71% isolated yield. In the course of rhodium coordination chemistry studies involving 3 , the formation of the isolable complex [(κ 2 - P , N - 3 )(κ 1 - P ,N- 3 )RhCl] ( 7 ) (81%) was observed, thereby confirming the propensity of this new ligand to form L n Rh( 3 ) 2 complexes. Such coordination chemistry behavior may contribute in part to the generally poor catalytic performance exhibited by mixtures of 3 and rhodium precursor complexes in the asymmetric hydrogenation and hydrosilylation studies described herein.

Data obtained from dynamic NMR investigations and reactivity studies revealed that the isolable, 18-electron Cp*Ru(κ3-P,C,C′) complex 3 provides access to the reactive, coordinatively unsaturated Cp*Ru(κ2-P,C) zwitterionic intermediate 4 by way of an unprecedented and reversible Ru−C(sp3) bond cleavage process that can be described as ‘indenyl hemilability’. Indirect support for the reversible generation of 4 from 3 was obtained through the isolation of adducts of the type 4·L upon treatment of 3 with various L-donor substrates (L = CO, PPh3, PHPh2, 4-dimethylaminopyridine, NH3, piperidine, and 2,6-dimethylaniline). The reactivity observed upon treatment of 3 with E−H containing substrates (H2, iPrOH, Ph3SiH, Ph2SiH2, PhNH2, and pyrrole) can be rationalized in terms of net cooperative substrate activation involving the Lewis acidic metal fragment and the Lewis basic indenide unit in the reactive intermediate 4. In the apparent reaction of 4 with PHPh2 and PH2Ph, an unusual ancillary ligand rearrangement i...

Salt metathesis reaction between Li(thf)(Me2Ntsi) [Me2Ntsi = C(SiMe3)2SiMe2NMe2] and InX3 gave the new indium dihalides (Me2Ntsi)InX2 [X = Cl (2a), I (2b); isolated yields 34% (2a) and 44% (2b)]. S...

The bulky m-terphenyl phenol Ar*OH 1 (Ar* = C6H3-2,6-Mes2, Mes = 2,4,6-trimethylphenyl) was synthesized via the treatment of Ar*Li with nitrobenzene. The phenol 1 is prepared in modest to good yield using this method. Attempts were also made to prepare 1 through oxidation of the bulky boronic acid Ar*B(OH)2with Oxone®, but this reaction was not suitable for preparative-scale reactions. Side products of the reaction between Ar*Li and nitrobenzene were identified as Ar*[N(O)Ph] and [C6H5N(O)]2and were characterized by X-ray crystallography and EPR spectroscopy. A variety of main-group and transition-metal complexes of Ar*OH were prepared, namely Sn(OAr*)2, Ge(OAr*)2, [N(SiMe3)2]Ge(OAr*), [Me2Al(OAr*)]2, and Ti(NMe2)(OAr*)2. All compounds were characterized spectroscopically and most were studied by single-crystal X-ray diffraction as well.Key words: m-terphenyl, main-group compounds, X-ray crystallography, multinuclear NMR spectroscopy, EPR spectroscopy.

Treatment of Cp*RuCl(kappa2-P,N-2b) (2b = 2-NMe2-3-PiPr2-indene) with TlSO3CF3 produced the cyclometalated complex [4]+SO3CF3- in 94% isolated yield. Exposure of [4]+X- (X = B(C6F5)4 or SO3CF3) to Ph2SiH2 (10 equiv) or PhSiH3 afforded the corresponding [Cp*(mu-P,N-2b)(H)2Ru=SiRPh]+X- complexes, [5]+X- (R = Ph; X = B(C6F5)4, 82%; X = SO3CF3, 39%) and [6]+X- (R = H; X = B(C6F5)4, 94%; X = SO3CF3, 95%). Notably, these transformations represent the first documented examples of Ru-mediated silylene extrusion via double geminal Si-H bond activation of an organosilane-a key step in the recently proposed Glaser-Tilley (G-T) alkene hydrosilylation mechanism. Treatment of [5]+B(C6F5)4- with KN(SiMe3)2 or [6]+SO3CF3- with NaN(SiMe3)2 afforded the corresponding zwitterionic Cp*(mu-2-NMe2-3-PiPr2-indenide)(H)2Ru=SiRPh complex in 69% (R = Ph, 7) or 86% (R = H, 8) isolated yield. Both [6]+X- and 8 proved unreactive toward 1-hexene and styrene and provided negligible catalytic turnover in the attempted metal-mediated hydrosilylation of these substrates with PhSiH3, thereby providing further empirical evidence for the required intermediacy of base-free Ru=Si species in the G-T mechanism. Isomerization of the P,N-indene ligand backbone in [6]+X-, giving rise to [Cp*(mu-1-PiPr2-2-NMe2-indene)(H)2Ru=SiHPh]+X- ([9]+X-), was observed. In the case of [9]+SO3CF3-, net intramolecular addition of the Ru=Si-H group across the styrene-like C=C unit within the ligand backbone to give 10 (96% isolated yield) was observed. Crystallographic characterization data are provided for [4]+X-, [5]+X-, [6]+X-, 8, and 10.

The synthesis and characterization of a new family of (η5-indenyl)MLn complexes (MLn = Mn(CO)3, Cp*Ru, or Cp*Fe; Cp* = η5-C5Me5) derived from 3-PiPr2-indene, 1-PiPr2-2-NMe2-indene (1a[H]), or 1-P(S...

Heating of [(COD)M(κ2-3-PiPr2-2-NMe2-indene)]+X- (M = Rh or Ir; X = BF4, PF6; COD = η4-1,5-cyclooctadiene) in a mixture of water and THF (48 h, 60 °C) afforded the neutral (COD)M(κ2-P,O) complexes (M = Rh, 5a, 80%; M = Ir, 5b, 74%). Similarly, thermolysis of [(COD)M(κ2-3-P(S)iPr2-2-NMe2-indene)]+BF4- (M = Rh or Ir) in a mixture of water and CH2Cl2 (14 h, 60 °C) produced the neutral (COD)M(κ2-P(S),O) complexes (M = Rh, 13a, 91%; M = Ir, 13b, 90%). Subsequent preparation of 1-PiPr2-2-indanone (8, 91%) enabled the non-hydrolytic synthesis of 5b in 70% isolated yield via treatment with 0.5[(COD)IrCl]2 in the presence of NEt3. Lithiation of (o-PiPr2)phenol followed by quenching with 0.5[(COD)IrCl]2 afforded the neutral (COD)Ir(κ2-P,O) complex 10 (91%). Single-crystal X-ray diffraction data are provided for 5b, 10, 13a, and 13b. Whereas 5a, 13a, and 13b performed poorly as catalysts for the hydrogenation of alkenes, the known complex (COD)Ir(OPh)(PCy3) 2 as well as 5b and 10 proved to be excellent catalysts for...

The effect of subtle changes in the sigma-electron donor ability of 4-substituted pyridine ligands on the lead(II) coordination environment of (2,6-Me(2)C(6)H(3)S)(2)Pb (1) adducts has been examined. The reaction of 1 with a series of 4-substituted pyridines in toluene or dichloromethane results in the formation of 1:1 complexes [(2,6-Me(2)C(6)H(3)S)(2)Pb(pyCOH)](2) (3), [(2,6-Me(2)C(6)H(3)S)(2)Pb(pyOMe)](2) (4), and (2,6-Me(2)C(6)H(3)S)(2)Pb(pyNMe(2)) (5) (pyCOH = 4-pyridinecarboxaldehyde; pyOMe = 4-methoxypyridine; pyNMe2 = 4-dimethylaminopyridine), all of which have been structurally characterized by X-ray crystallography. The structures of 3 and 4 are dimeric and have psi-trigonal bipyramidal S(3)N bonding environments, with the 4-substituted pyridine nitrogen and bridging sulfur atoms in axial positions and two thiolate sulfur atoms in equatorial sites. Conversely, compound 5 is monomeric and exhibits a psi-trigonal pyramidal S(2)N bonding environment at lead(II). The observed structures may be rationalized in terms of a simple valence bond model and the sigma-electron donor ability of the 4-pyridine ligands as derived from the analysis of proton affinity values. Solid-state (207)Pb NMR experiments are applied in combination with density functional theory (DFT) calculations to provide further insight into the nature of bonding in 4, 5, and (2,6-Me(2)C(6)H(3)S)(2)Pb(py)(2) (2). The lead chemical shielding (CS) tensor parameters of 2, 4, and 5 reveal some of the largest chemical shielding anisotropies (CSA) observed in lead coordination complexes to date. DFT calculations using the Amsterdam Density Functional (ADF) program, which take into account relativistic effects using the zeroth-order regular approximation (ZORA), yield lead CS tensor components and orientations. Paramagnetic contributions to the lead CS tensor from individual pairs of occupied and virtual molecular orbitals (MOs) are examined to gain insight into the origin of the large CSA. The CS tensor is primarily influenced by mixing of the occupied MOs localized on the sulfur and lead atoms with virtual MOs largely comprised of lead 6p orbitals.

The cystamine conjugate [(BocNH)Fc(CO)CSA]2 was prepared by coupling cystamine with the N-protected ferrocene amino acid derivative BocHN-Fc-COOH and was fully characterized by spectroscopic methods and by single-crystal X-ray diffraction. The cystamine conjugate forms films on gold substrates, which upon deprotection of the amino group, react with chemical warfare agent (CWA) mimics, upon which the redox properties of the Fc group are affected significantly. Cyclic voltammetry shows 50(5) mV anodic shifts of the Fc redox potentials after exposure to EtSCH2CH2Cl, a simulant for sulfur mustard HD (MA), and (NC)(EtO)2P(O), a simulant for nerve agent Tabun (NA). Exposure to MA and NA causes an increase in 2.3 and 4.5 ng mass, respectively, in QCM which indicates ca. 70% efficiency in Boc-deprotection. Ellipsometry measured a film thickness increase from 6(+/-1) A for the deprotected film to 10(+/-4) A for the film modified with MA and to 7(+/-2) A for the film modified with NA. AFM measurements show changes in the thickness and morphology of the film after reaction with MA and NA. The surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and clearly show the attachment of the cystamine conjugate on the surface and its reaction with CWA mimics.

A family of neutral, cationic, and formally zwitterionic Rh(I) and Ir(I) complexes featuring 1-PiPr2-2-NMe2-indene (3a), 3-PiPr2-2-NMe2-indene (3b), or 3-PiPr2-2-NMe2-indenide (3c) ligands have been prepared and structurally characterized. Whereas treatment of 3a with 0.5 equiv of [(COD)RhCl]2 afforded (COD)RhCl(κ1-P,N-3a) (4a) in 96% isolated yield, [(COD)M(κ2-P,N-3a)]+X- ([5a]+PF6-, M = Rh; [6a]+SO3CF3-, M = Ir) complexes were obtained in 14% and 41% isolated yield from 3a and the appropriate in-situ-prepared [(COD)M(THF)2]+X- precursor. The isomeric complexes [(COD)M(κ2-P,N-3b)]+X- ([5b]+X-, M = Rh; [6b]+X-, M = Ir) were prepared using a similar protocol employing NEt3, with isolated yields ranging from 37% to 94% depending on the identity of M and X. The zwitterionic complexes (COD)M(κ2-P,N-3c) (5c, M = Rh; 6c, M = Ir) were prepared in 89% and 93% isolated yield, either upon treatment of [5b]+X- or [6b]+X- with NaN(SiMe3)2 or via addition of 0.5 equiv of [(COD)MCl]2 to [3c]Li. The Rh(I) complexes (CO)...