Silver catalyzed proto- and sila-Nakamura-type α-vinylation of silyl enol ethers with dichloroacetylene. Divergent formation of stereochemically pure tri- and tetrasubstituted olefins.

The silver-catalyzed reaction of silyl enol ethers with dichloroacetylene (DCA) is described. When DCA was used as a solution in diethyl ether, we found that the silyl group was transferred to the vinyl group, resulting in stereochemically pure tetrasubstituted olefins. However, when DCA was used as a solution in the more polar acetonitrile, protonation was the major pathway, and trisubstituted olefins were the dominant products.

Aqueous-Phase Nitrile Hydration Catalyzed by an In Situ Generated Air-Stable Ruthenium Catalyst.

RuCl2 (PTA)4 (PTA=1,3,5-triaza-7-phosphaadamantane) is an active, recyclable, air-stable, aqueous-phase nitrile hydration catalyst. The development of an in situ generated aqueous-phase nitrile hydration catalyst (RuCl3 ⋅3 H2 O+6 equivalents PTA) is reported. The activity of the in situ catalyst is comparable to RuCl2 (PTA)4 . The effects of [PTA] on the activity of the reaction were investigated: the catalytic activity, in general, increases as the pH goes up, which shows a positive correlation with [PTA]. The pH effects were further explored for both the in situ and RuCl2 (PTA)4 catalyzed reaction in phosphate buffer solutions with particular attention given to pH 6.8 buffer. Increased catalytic activity was observed at pH 6.8 versus water for both systems with turnover frequency (TOF) up to 135 h-1 observed for RuCl2 (PTA)4 and 64 h-1 for the in situ catalyst. Catalyst loading down to 0.001 mol % was examined with turnover numbers as high as 22 000 reported. Similar to the preformed catalyst, RuCl2 (PTA)4 , the in situ catalyst could be recycled more than five times without significant loss of activity from either water or pH 6.8 buffer.

Unusual Water-Soluble Imino Phosphine Ligand: Enamine and Imine Derivatives of 1,3,5-Triaza-7-phosphaadamantane (PTA).

A series of water-soluble and air-stable E-enamine derivatives of 1,3,5-triaza-7-phosphaadamantane (PTA), PTA═C(R)NH2, 1-4, are reported along with data on E-Z isomerization and tautomerization to the imine form (PTA-CR═NH). Reaction of 1,3,5-triaza-7-phosphaamantane-6-yl lithium, PTA-Li, with aromatic nitriles afforded E-enamine derivatives of PTA in good yield (49-91%). Phosphines 1-4 are stable toward water and air, and do not appear to isomerize or tautomerize, unless coordinated to a metal or oxidized. The corresponding oxides, O═PTA═C(R)NH2 (5-8), were observed as ∼55/45 mixtures of E and Z isomers. Kinetic data on the E-Z isomerization is reported. Upon coordination of 1-4 to W(CO)4(pip)2, a κ1- P enamine is formed, [W(CO)4(pip)(κ1- P-PTA═CRNH2)]. Enamine-imine tautomerization of the metal bound phosphine was observed resulting in κ2- P, N imine complexes, [W(CO)4(κ2- P, N-PTA-CR═NH)], 9-12. The crystal structures of the κ1- P enamine 11a, κ2- P, N imine 9 and 12, phosphines 1 and 3, as well as phosphine oxide 8a were obtained. DFT calculations on the various isomers of the phosphines and phosphine oxides are also reported.

Synthesis and Photoisomerization of Substituted Dibenzofulvene Molecular Rotors.

The synthesis, spectral and structural characterization, and photoisomerization of a family of 2-substituted dibenzofulvene molecular actuators based on (2,2,2-triphenylethylidene)fluorene (TEF) are reported. The 2-substituted species investigated are nitro (NTEF), cyano (CTEF), and iodo (ITEF). X-ray structures of these three compounds and three intermediates were determined to assign alkene configuration and investigate the effects of the 2-substituents on steric gearing. The addition-elimination reaction of Z-9 with trityl anion to form Z-10 proceeded with complete retention of configuration. Rates of photoisomerization were measured at irradiation wavelengths between 266-355 nm in acetonitrile/dioxane solutions at room temperature. Photoisomerization quantum yields (φ) were calculated by means of a mathematical model that accounts for a certain degree of photodecomposition in the cases of CTEF and ITEF. Quantum yields vary significantly with substituent, having maximum values of φ=0.26 for NTEF, 0.39 for CTEF, and 0.50 for ITEF. NTEF is photochemically robust and has a large quantum yield for photoisomerization in the near-UV, making it a particularly promising drive rotor moiety for light-powered molecular devices.

Metal complexes of pyridine-fused macrocyclic polyamines targeting the chemokine receptor CXCR4.

The chemokine receptor CXCR4 acts as a key cell surface receptor in HIV infections, multiple forms of cancer, and various other pathologies, such as rheumatoid arthritis and asthma. Macrocyclic polyamines and their metal complexes are known to exert anti-HIV activity, many acting as HIV entry inhibitors by specifically binding to CXCR4. Three series of pyridopentaazacylopentadecanes, in which the pyridine ring is fused to zero, one, or two saturated six-membered rings, were synthesized by manganese(ii)-templated Schiff-base cyclization of triethylenetetramine with various dicarbonyl compounds. By evaluating these macrocyclic polyamines and their complexes with Mn(2+), Cu(2+), Fe(3+), and Zn(2+), we have discovered novel CXCR4-binding compounds. The MnCl2 complex of a new pentaazacyclopentadecane with one fused carbocyclic ring (11) was found to have the greatest potency as an antagonist of the chemokine receptor CXCR4 (IC50: 0.014 µM), as evidenced by inhibiting binding of CXCL12 to PBMCs (peripheral blood mononuclear cells). Consequently, this compound inhibits replication of the CXCR4-using (X4) HIV-1 strain NL4-3 in the TZM-bl cell line with an IC50 value of 0.52 µM and low cytotoxicity (CC50: >100 µM). In addition, 18 other compounds were evaluated for their interaction with CXCR4 via their ability to interfere with ligand chemokine binding and HIV entry and infection. Of these, the metal complexes of the two more hydrophobic series with one or two fused carbocyclic rings exhibited the greatest potency. The Zn(2+) complex 21 was among the most potent, showing that redox activity of the metal center is not associated with CXCR4 antagonist activity.

Synthesis and characterization of [Zn(acetate)2(amine)x] compounds (x = 1 or 2) and their use as precursors to ZnO.

As an obvious candidate for a p-type dopant in ZnO, nitrogen remains elusive in this role. Nitrogen containing precursors are a potential means to incorporate nitrogen during MOCVD growth. One class of nitrogen-containing precursors are zinc acetate amines, yet, they have received little attention. The synthesis and single crystal X-ray structure of [Zn(acetate)2(en)], and the synthesis of [Zn(acetate)2(en)2], [Zn(acetate)2(benzylamine)2], [Zn(acetate)2(butylamine)2], [Zn(acetate)2(NH3)2], and [Zn(acetate)2(tris)2], where en = ethylenediamine and tris = (tris[hydroxymethyl]aminomethane) are reported. The compounds were characterized by thermogravimetric analysis and pyrolyzed in air and inert gas to yield ZnO. These compounds are useful single source precursors to ZnO bulk powders by alkali precipitation and ZnO thin films by spray pyrolysis. The amine bound to the zinc influences the ZnO crystal size and shape and acts as a nitrogen donor for preparing nitrogen-doped ZnO during alkali precipitation. Thin films of ZnO prepared by spray pyrolysis using the precursors had a (100) preferred orientation and measured n-type to intrinsic conductivity.

Hemilabile ß-aminophosphine ligands derived from 1,3,5-triaza-7-phosphaadamantane: application in aqueous ruthenium catalyzed nitrile hydration.

A series of ß-aminophosphines derived from 1,3,5-triaza-7-phosphaadamantane (PTA) are described. PTA-CHPhNHPh (1), PTA-CH(p-C(6)H(4)OCH(3))NHPh (2), and PTA-CPh(2)NHPh (3) were prepared in good yield (62-77%) by reaction of lithiated PTA with the corresponding imine followed by hydrolysis. Compounds 1 and 2 were synthesized as pairs of diastereomers which were separated by successive recrystallization from THF/hexane. Compounds 1-3 are somewhat soluble in water (S(25)(o) = 4.8 (1), 4.9 (2), 2.7 (3) g/L). Upon coordination to Ru(II) arene centers both monodentate (κ(1)-P) [RuCl(2)(η(6)-toluene)(1-3)] and bidentate (κ(2)-P,N) [RuCl(η(6)-toluene)(1-3)]Cl coordination modes were observed. Ru(II) arene complexes 4-6 exhibited hemilabile behavior transitioning between κ(1)-P and κ(2)-P,N coordination upon change in solvent or addition of a coordinating ligand such as Cl(-) or CH(3)CN. Complexes (4-6) were found to be active air stable catalysts for the aqueous phase hydration of various nitriles with TOF up to 285 h(-1) and TON of up to 97,000 observed.

The Suzuki reaction in aqueous media promoted by P, N ligands.

The synthesis and structure of palladium complexes of trisubstituted PTA derivatives, PTA(R3), are described. Water-soluble phosphine ligands 1,3,5-triaza-7-phosphaadmantane (PTA), tris(aminomethyl)phosphine trihydrobromide, tri(aminomethyl) phosphine, 3,7-dimethyl-1,5,7-triaza-3-phosphabicyclo[3,3,1]nonane (RO-PTA), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA), lithium 1,3,5-triaza-7-phosphaadamantane-6-carboxylate (PTA-CO2Li), 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo [3.3.1.1]decane, and 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane were used as ligands for palladium catalyzed Suzuki reactions in aqueous media. RO-PTA in combination with palladium acetate or palladium chloride was the most active catalyst for Suzuki cross coupling of aryl bromides and phenylboronic acid at 80 °C in 1:1 water:acetonitrile. The activity of Pd(II) complexes of RO-PTA is comparable to PPh2(m-C6H4SO3Na) (TPPMS) and P(m-C6H4SO3Na)3 (TPPTS) and less active than tri(4,6-dimethyl-3-sulfonatophenyl)phosphine trisodium salt (TXPTS). Activated, deactivated, and sterically hindered aryl bromides were examined, with yields ranging from 50% to 90% in 6 h with 5% palladium precatalyst loading. X-ray crystal structures of (RO-PTA)PdCl2, (PTA(R3))2PdCl2 (R = Ph, p-tert-butylC6H5), and PTA(R3) (R = p-tert-butylC6H5) are reported.

Organometallic ruthenium complexes with thiosemicarbazone ligands: Synthesis, structure and cytotoxicity of [(eta-p-cymene)Ru(NS)Cl] (NS = 9-anthraldehyde thiosemicarbazones).

A series of half-sandwich arene-ruthenium complexes of the type [(eta(6)-p-cymene) Ru(thiosemicarbazone)Cl](+) have been synthesized and their biological activity investigated. The first structurally characterized arene-ruthenium half-sandwich complex with a thiosemicarbazone ligand is reported.

Insertion of CO2, ketones, and aldehydes into the C-Li bond of 1,3,5-triaza-7-phosphaadamantan-6-yllithium.

The synthesis and structures of a series of new water-soluble phosphine ligands based on 1,3,5-triaza-7-phosphaadamantane (PTA) are described. Insertion of aldehydes or ketones into the C-Li bond of 1,3,5-triaza-7-phosphaadamantan-6-yllithium (PTA-Li) resulted in the formation of a series of slightly water-soluble beta-phosphino alcohols (PTA-CRR'OH, R = C6H5, C(6)H(4)OCH(3), ferrocenyl; R' = H, C(6)H(5), C(6)H(4)OCH(3)) derived from the heterocyclic phosphine PTA. Insertion of CO(2) yielded the highly water-soluble carboxylate PTA-CO(2)Li, S(2)5 degrees approximately 800 g/L. The compounds have been fully characterized in the solid state by X-ray crystallography and in solution by multinuclear NMR spectroscopy. The addition of PTA-Li to symmetric ketones results in a racemic mixture of PTA-CR(2)OH ligands with a single resonance in the (31)P{(1)H} NMR spectrum between -95 and -97 ppm. The addition of PTA-Li to aldehydes results in a mixture of diasteromeric compounds, PTA-CHROH, with two (31)P{(1)H} NMR resonances between -100 and -106 ppm. Three (eta(6)-arene)RuCl(2)(PTA-CRR'OH) complexes of these ligands were synthesized and characterized, with the ligands binding in a kappa1 coordination mode. All the ligands and ruthenium complexes are slightly soluble in water with S25 degrees = 3.9-11.1 g/L for the PTA-CRR'OH ligands and S(25) degrees = 3.3-14.1 g/L for the (eta(6)-arene)RuCl(2)(PTA-CRR'OH) complexes.

Development of a series of P(CH(2)N=CHR)(3) and trisubstituted 1,3,5-Triaza-7-phosphaadamantane ligands.

The synthesis and structure of a series of novel phosphine ligands derived from the condensation of P(CH2NH2) with aldehydes are described. Depending on the reaction conditions, either substituted tris(iminomethyl)phosphine, P(CH2N=CHR)3, or 1,3,5-triaza-7-phosphaadamantane structures substituted at the "lower rim", PTAR3, are obtained.

Isomerization of trans-[Ru(PTA)4Cl2] to cis-[Ru(PTA)4Cl2] in water and organic solvent: revisiting the chemistry of [Ru(PTA)4Cl2].

trans-[Ru(PTA)4Cl2] (trans-1), (PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane) has been isolated and structurally characterized by X-ray crystallography. The structure reveals ruthenium in a slightly distorted-octahedral environment bound to two axial chlorides and four equatorial PTA ligands. In organic solvents, trans-1 undergoes a relatively clean isomerization to cis-1. In aqueous environments, trans-1 undergoes a more complicated transformation involving isomerization, protonation, and ligand substitution affording cis-1 and a series of structurally related molecules. From these results, we conclude that the synthesis of [Ru(PTA)4Cl2] (1) affords trans-1, not cis-1, as earlier reports suggest. The water-soluble hydride cis-[Ru(PTA)4H2] (2) has also been synthesized from the reaction of trans-[Ru(PTA)4Cl2] with excess sodium formate. Compound 2 is stable in deoxygenated water and undergoes H/D exchange with D2O (t1/2 approximately equal to 120 min, at 25 degrees C). The solid-state structures of both trans-1 and 2 are described.

Synthesis and coordination chemistry of a novel bidentate phosphine: 6-(diphenylphosphino)-1,3,5-triaza-7-phosphaadamantane (PTA-PPh2).

The upper rim of 1,3,5-triaza-7-phosphaadamantane (PTA) has been modified for the first time. Lithiation of PTA, with n-butyllithium, resulted in deprotonation of an alpha-phosphorus methylene and the formation of 1,3,5-triaza-7-phosphaadamantane-6-yllithium (PTA-Li). The chiral chelating phosphine 6-(diphenylphosphino)-1,3,5-triaza-7-phosphaadamantane (PTA-PPh2) was synthesized, in racemic form, by the reaction of PTA-Li with ClPPh2. PTA-PPh2 has been fully characterized in solution by multinuclear NMR spectroscopy and mass spectrometry and in the solid state by X-ray crystallography. The 31P NMR spectrum contains a pair of doublets at -19.8 and -100.1 ppm (d, (2)J(PP) = 65 Hz). Unlike PTA, the new bidentate phosphine, PTA-PPh2, is insoluble in aqueous solutions. Two group 6 metal carbonyl complexes, [M(CO)4(PTA-PPh2)] (M = W and Mo), were synthesized by the addition of PTA-PPh2 to cis-[M(CO)4(pip)2] and characterized by NMR spectroscopy, IR spectroscopy, and X-ray crystallography. Also reported are the solid-state structures of cis-[W(CO)4PTA2], cis-[W(CO)4(PTA)(PPh3)], and [W(CO)4DPPM] (DPPM = diphenylphosphinomethane). PTA-PPh2 appears to be sterically similar to and slightly more electron-donating than DPPM.

Manganese complexes of 1,3,5-triaza-7-phosphaadamantane (PTA): the first nitrogen-bound transition-metal complex of PTA.

The structures of two manganese(II) complexes of 1,3,5-triaza-7-phosphaadamantane (PTA) reveal the first transition-metal complexes of PTA in which the metal preferentially coordinates to a nitrogen and not the phosphorus of PTA. The coordination environment about the manganese was probed using X-ray crystallography (solid state) and EXAFS spectroscopy (solution).

Structural and Spectroscopic Studies of 16-Electron, Unsaturated Derivatives of Low-Valent, Group 6 Carbonyl Complexes Containing pi-Donor Ligands.

Several eighteen- and sixteen-electron derivatives of tungsten(0), molybdenum(0), and chromium(0) carbonyl complexes, including [PPN](2)[Cr(CO)(3)(O,S-C(6)H(4))] (2c), [PPN](2)[W(CO)(3)(NH,S-C(6)H(4))] (5c), [PPN](2)[W(CO)(3)(O,S-C(6)H(4))] (6c), [PPN](2)[W(CO)(4)(S,S-C(6)H(4))] (7b) have been synthesized from the reaction of photochemically generated M(CO)(5)THF with a series of doubly deprotonated 1,2-disubstituted benzene rings with the appropriate oxygen, nitrogen, and sulfur donor atoms. These complexes have been characterized in the solid state by X-ray crystallography and in solution by IR and (13)C NMR spectroscopies. The crystal of 2c (C(84)H(71)N(3)O(5)P(4)SCr) is triclinic P&onemacr;, a =13.869(3) Å, b = 23.128(5) Å, c = 12.056(2) Å, alpha = 104.84(3) degrees, beta = 106.91(3) degrees, gamma = 95.29(3) degrees, Z = 2; that of 5c (C(89)H(77)N(7)O(3)P(4)SW) is monoclinic P2(1), a = 11.054(2) Å, b = 28.140(6) Å, c = 12.566(2) Å, beta = 90.58(1) degrees, Z = 2; that of 6c (C(85)H(70)N(4)O(4)P(4)SW) is triclinic P&onemacr;, 12.236(2) Å, b = 14.419(2) Å, c = 22.748(4) Å, alpha = 76.44(1) degrees, beta = 75.98(2) degrees, gamma = 70.98(1) degrees, Z = 2; that of 7b (C(82)H(64)N(2)O(4)P(4)S(2)W) is triclinic P&onemacr;, a = 12.650(1) Å, b = 14.810(1) Å, c = 21.053(2) Å, alpha = 77.182(7) degrees, beta = 78.334(7) degrees, gamma = 66.579(7), Z = 2; and that of 8 (C(10)H(8)O(4)P(2)W) is monoclinic P2(1)/c, a = 11.582(1) Å, b = 10.791(1) Å, c = 10.449(1) Å, beta = 100.867(7) degrees, Z = 2. The average nu(CO) frequencies for each tricarbonyl species reported are compared to those related dianions previously reported in order to gauge the pi-donor character of the different ligands. The (13)C NMR spectrum for each tricarbonyl derivative consists of a single sharp peak for the three inequivalent carbonyls as a result of a low-energy, fast intramolecular exchange process. Both inter- and intramolecular CO-exchange processes have been probed via variable temperature (13)C NMR. In the case of the 16-electron species the geometry of the metal dianion is that of a distorted trigonal bipyramid consisting of three carbonyl ligands and a five-membered chelate ring bound through the pi-donor atoms at an equatorial and an axial position, with the stronger pi-donor atom in the equatorial site. The equatorial site for the most effective pi-donor is preferred over the axial position because the unoccupied d(xy)() orbital lies in the equatorial plane, and may be stabilized via a pi-donor ligand in the equatorial position. The axial position exhibits a filled/filled repulsion as both orbitals available for pi-bonding are filled.

Coordination Chemistry, Structure, and Reactivity of Thiouracil Derivatives of Tungsten(0) Hexacarbonyl: A Theoretical and Experimental Investigation into the Chelation/Dechelation of Thiouracil via CO Loss and Addition.

The synthesis of 2-thiouracil and 6-methyl-2-uracil derivatives of tungsten carbonyl from the reaction of photogenerated W(CO)(5)(solvent) (solvent = MeOH or THF) and the corresponding [Et(4)N][thiouracilate] is described. The crystal structure of the [Et(4)N][W(CO)(5)(2-thiouracilate)], 1, derivative is reported where the thiouracilate is found to be bound to the tungsten center via the exocyclic sulfur atom. In the solid-state structure of 1 two anions are associated by means of two hydrogen bonds between the metal bound nucleobases. These pentacarbonyl complexes stereoselectively lose cis carbonyl ligands, as is apparent from (13)C-labeling studies, to provide the endocyclic nitrogen N(1)-chelated tungsten tetracarbonyl derivatives, e.g., [Et(4)N][W(CO)(4)(2-thiouracilate)], 3. The kinetics of the loss of CO from the pentacarbonyl anions to afford the metal tetracarbonyls, and the reverse of that process, were monitored by means of in situ infrared spectroscopy in the nu(CO) region as a function of temperature. These studies reveal that the tetracarbonyl anions in CO-saturated acetonitrile ([CO] approximately 6 x 10(-)(3) M) are unstable with respect to the formation of the pentacarbonyl derivatives, i.e., the equilibrium 1 right harpoon over left harpoon 3 + CO lies to the left under an atmosphere of carbon monoxide. From the activation parameters determined for the dissociative CO loss process (DeltaH() = 82.0 +/- 3.6 kJ mol(-)(1) and DeltaS() = -44.9 +/- 9.6 J mol(-)(1) K(-)(1) for complex 1) it is apparent that the sulfur-bound thiouracilate ligand is serving as a pi-donor during CO dissociation, i.e., behaving as a cis-labilizing ligand. Ab initio geometry optimizations carried out for the process 1 right harpoon over left harpoon 3 + CO at the Hartree-Fock and DFT levels support these experimental observations. For example, complex 1 is shown to be more stable than 3 + CO and chelation via the endocyclic N(1) donor is favored over N(3) binding. Finally, the "16-electron" intermediate resulting from CO dissociation in 1 was found to possess a significantly shortened W-S interaction, presumably due to the pi-donating ability of the thiouracilate ligand.