Key factors determining the course of methyl iodide oxidative addition to diamidonaphthalene-bridged diiridium(I) and dirhodium(I) complexes

The course of methyl iodide oxidative addition to various nucleophilic complexes, [Ir2(mu-1,8-(NH)2naphth)(CO)2(PiPr3)2] (1), [IrRh(mu-1,8-(NH)2naphth)(CO)2(PiPr3)2] (2), and [Rh2(mu-1,8-(NH)2naphth)(CO)2(PR3)2] (R = iPr, 3; Ph, 4; p-tolyl, 5; Me, 6), has been investigated. The CH3I addition to complex 1 readily affords the diiridium(II) complex [Ir2(mu-1,8-(NH)2naphth)I(CH3)(CO)2(PiPr3)2] (7), which undergoes slow rearrangement to give a thermodynamically stable stereoisomer, 8. The reaction of the Ir-Rh complex 2 gives the ionic compound [IrRh(mu-1,8-(NH)2naphth)(CH3)(CO)2(PiPr3)2]I (10). The dirhodium compounds, 3-5, undergo one-center additions to yield acyl complexes of the formula (Rh2(mu-1,8-(NH)2naphth)I(COCH3)(CO)(PR3)2] (R = iPr, 12; Ph, 13; p-tolyl, 14). The structure of 12 has been determined by X-ray diffraction. Further reactions of these Rh(III)-Rh(I) acyl derivatives with CH3I are productive only for the p-tolylphosphine derivative, which affords the bis-acyl complex [Rh2(mu-1,8-(NH)2naphth)(CH3CO)2I2(P(p-tolyl)3)2] (15). The reaction of the PMe3 derivative, 6, allows the isolation of the bis-methyl complex [Rh2(mu-1,8-(NH)2naphth)(mu-I)(CH3)2(CO)2(PMe3)2]I (16a), which emanates from a double one-center addition. Upon reaction with methyl triflate, the starting materials, 1, 2, 3, and 6, give the isostructural cationic methyl complexes 9, 11, 17, and 18, respectively. The behavior of these cationic methyl compounds toward CH3I, CH3OSO2CF3, and tetrabutylamonium iodide is consistent with the role of these species as intermediates in the SN2 addition of CH3I. Compounds 18 and 17 react with an excess of methyl triflate to give [Rh2(mu-1,8-(NH)2naphth)(mu-OSO2CF3)(CH3)2(CO)2(PMe3)2][CF3SO3] (19) and [Rh2(mu-1,8-(NH)2naphth)(OSO2CF3)(COCH3)(CH3)(CO)(PiPr3)2][CF3SO3] (20), respectively. Upon treatment with acetonitrile, complexes 17 and 18 give the isostructural cationic acyl complexes [Rh2(mu-1,8-(NH)2naphth)(COCH3)(NCCH3)(CO)(PR3)2][CF3SO3] (R = iPr, 21; Me, 22). A kinetic study of the reaction leading to 21 shows that formation of these complexes involves a slow insertion step followed by the fast coordination of the acetonitrile. The variety of reactions found in this system can be rationalized in terms of three alternative reaction pathways, which are determined by the effectiveness of the interactions between the two metal centers of the dinuclear complex and by the steric constraints due to the phosphine ligands.     

Investigation of silver salt metathesis: preparation of cationic germanium(II) and Tin(II) complexes,and silver adducts containing unsupported silver-germanium and silver-tin bonds

Syntheses of halide derivatives of germanium(II) and tin(II) aminotroponiminate (ATI) complexes and their silver salt metathesis reactions have been investigated. The treatment of GeCl(2) x (1,4-dioxane), SnCl(2), or SnI(2) with [(n-Pr)(2)ATI]Li in a 1:1 molar ratio affords the corresponding germanium(II) or tin(II) halide complex [(n-Pr)(2)ATI]MX (where [(n-Pr)(2)ATI](-) = N-(n-propyl)-2-(n-propylamino)troponiminate; M = Ge or Sn; X = Cl or I). As usually expected, [(n-Pr)(2)ATI]GeCl and [(n-Pr)(2)ATI]SnCl undergo rapid metathesis with CF(3)SO(3)Ag, leading to trifluoromethanesulfonate salts, [[(n-Pr)(2)ATI]Ge][SO(3)CF(3)] and [[(n-Pr)(2)ATI]Sn][SO(3)CF(3)], and silver chloride. However, when the silver source [HB(3,5-(CF(3))(2)Pz)(3)]Ag(eta(2)-toluene) is used, rather than undergoing metathesis, very stable 1:1 adducts [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Ge(Cl)[(n-Pr)(2)ATI] and [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(Cl)[(n-Pr)(2)ATI] are formed (where [HB(3,5-(CF(3))(2)Pz)(3)](-) = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate). The use of the iodide derivative [(n-Pr)(2)ATI]SnI did not change the outcome either. All new compounds have been characterized by multinuclear NMR spectroscopy and X-ray crystallography. The Ag-Ge and Ag-Sn bond distances of [HB(3,5-(CF(3))(2)Pz)(3)]Ag<-- Ge(Cl)[(n-Pr)(2)ATI], [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(Cl)[(n-Pr)(2)ATI], and [HB(3,5-(CF(3))(2)Pz)(3)]Ag<--Sn(I)[(n-Pr)(2)ATI] are 2.4142(6), 2.5863(6), and 2.5880(10) A, respectively. A convenient route to [(n-Pr)(2)ATI]H is also reported.     

Topological variations of the PDP ligand and its prospects in molybdenum(0) dearomatization agents

The compounds fac-(κ(3)-PDP)Mo(CO)(3) {1; PDP = 2-[[2-(1-(pyridin-2-ylmethyl)pyrrolidin-2-yl)pyrrolidin-1-yl]methyl]pyridine}, [(cis-β-PDP)Mo(NO)(CO)]PF(6) ([cis-β-3]PF(6)), [(cis-α-PDP)Mo(NO)(CO)]PF(6) ([cis-α-3]PF(6)), [(cis-α-PDP)Mo(NO)Br]PF(6) ([4]PF(6)), [(trans-PDP)Cu](BF(4))(2)·CH(3)CN ([5](BF(4))(2)·CH(3)CN), and [(trans-PDP)Cu](OSO(2)CF(3))(2) ([5](OSO(2)CF(3))(2)) have been synthesized and structurally characterized by single-crystal X-ray diffraction. These are the first reported complexes of PDP on metal centers other than iron(II). The observed configurations indicate a broader range of accessible PDP topologies than has been reported. The {(cis-α-PDP)Mo(NO)}(+) fragment is found to be less π-basic than the dearomatizing {Tp(MeIm)Mo(NO)} fragment [Tp = hydridotris(1-pyrazolyl)borato; MeIm = 1-methylimidazole].     

Dinickel(II) complexes: preparation and catalytic activity

Ligands (L(a-c)) based on 2,7-bis(3,5-di-R-pyrazol-1-yl)-1,8-naphthyridine (a, R = H; b, R = CH(3); c, R = Ph) were prepared for the construction of a series of dinickel complexes. Treatment of L(x) with NiCl(2) in an anhydrous methanol/THF solution resulted in the formation of dinuclear complexes [(L(x))(μ-Cl)(2)Ni(2)Cl(2)(CH(3)OH)(2)] (3, x = a; 4, x = b; 5, x = c). These new complexes were characterized by elemental analysis, IR and UV-Vis spectroscopic techniques. The structures of complexes 3 and 4 were further confirmed by X-ray diffraction studies. Interestingly, crystals of 4 were obtained as a co-crystallization of 4 and the methanol substituted species [{(L(b))(μ-Cl)(2)Ni(2)Cl(CH(3)OH)(3)}Cl] (4'). These dinickel complexes have been tested in the catalytic homo-coupling of terminal alkynes with the use O(2) as the oxidant, showing excellent activities. A clear improvement on the catalytic activity of these complexes is observed as compared to the mono-nuclear species.     

Model studies of methyl CoM reductase: methane formation via CH3-S bond cleavage of Ni(I) tetraazacyclic complexes having intramolecular methyl sulfide pendants

The Ni(I) tetraazacycles [Ni(dmmtc)](+) and [Ni(mtc)](+), which have methylthioethyl pendants, were synthesized as models of the reduced state of the active site of methyl coenzyme M reductase (MCR), and their structures and redox properties were elucidated (dmmtc, 1,8-dimethyl-4,11-bis{(2-methylthio)ethyl}-1,4,8,11-tetraaza-1,4,8,11-cyclotetradecane; mtc, 1,8-{bis(2-methylthio)ethyl}-1,4,8,11-tetraaza-1,4,8,11-cyclotetradecane). The intramolecular CH(3)-S bond of the thioether pendant of [Ni(I)(dmmtc)](OTf) was cleaved in THF at 75 °C in the presence of the bulky thiol DmpSH, which acts as a proton source, and methane was formed in 31% yield and a Ni(II) thiolate complex was concomitantly obtained (Dmp = 2,6-dimesityphenyl). The CH(3)-S bond cleavage of [Ni(I)(mtc)](+) also proceeded similarly, but under milder conditions probably due to the lower potential of the [Ni(I)(mtc)](+) complex. These results indicate that the robust CH(3)-S bond can be homolytically cleaved by the Ni(I) center when they are properly arranged, which highlights the significance of the F430 Ni environment in the active site of the MCR protein.     

Synthesis and electrochemical studies of diiron complexes of 1,8-naphthyridine-based dinucleating ligands to model features of the active sites of non-heme diiron enzymes

A bis(mu-carboxylato)(mu-1,8-naphthyridine)diiron(II) complex, [Fe2(BPMAN)(mu-O2CPhCy)2](OTf)2 (1), was prepared by using the 1,8-naphthyridine-based dinucleating ligand BPMAN, where BPMAN = 2,7-bis[bis(2-pyridylmethyl)aminomethyl]-1,8-naphthyridine. The cyclic voltammogram (CV) of this complex in CH2Cl2 exhibited two reversible one-electron redox waves at +296 mV (DeltaE(p) = 80 mV) and +781 mV (DeltaE(p) = 74 mV) vs Cp2Fe+/Cp2Fe, corresponding to the FeIIIFeII/FeIIFeII and FeIIIFeIII/FeIIIFeII couples, respectively. This result is unprecedented for diiron complexes having no single atom bridge. Dinuclear complexes [Fe2(BPMAN)(mu-OH)(mu-O2CPhCy)](OTf)2 (2) and [Mn2(BPMAN)(mu-O2CPhCy)2](OTf)2 (3) were also synthesized and structurally characterized. The cyclic voltammogram of 2 in CH2Cl2 exhibited one reversible redox wave at -22 mV only when the potential was kept below +400 mV. The CV of 3 showed irreversible oxidation at potentials above +900 mV. Diiron(II) complexes [Fe2(BEAN)(mu-O2CPhCy)3](OTf) (4) and [Fe2(BBBAN)(mu-OAc)2(OTf)](OTf) (6) were also prepared and characterized, where BEAN = 2,7-bis(N,N-diethylaminomethyl)-1,8-naphthyridine and BBBAN = 2,7-bis[2-[2-(1-methyl)benzimidazolylethyl]-N-benzylaminomethyl]-1,8-naphthyridine. The cyclic voltammograms of these complexes were recorded. The M?ssbauer properties of the diiron compounds were studied.     

The preparation and characterisation of bimetallic iridium(II) complexes containing derivatised bridging naphthalene-1,8-disulfur or 4,5-dithiolato acephenanthrylene ligands

Oxidative addition of the disulfide compounds naphtho[1,8-cd][1,2]dithiole, 2-tert-butylnaptho[1,8-cd][1,2]dithiole, 2,7-di-tert-butylnaphtho[1,8-cd][1,2]dithiole, 4,5-dithiaacephenanthrylene and the thio/sulfinyl and thio/sulfonyl compounds naphtho[1,8-cd][1,2]dithiole 1-oxide, and naphtho[1,8-cd][1,2]dithiole 1,1-dioxide respectively to [[Ir(mu-Cl)(cod)](2)] give dinuclear Ir-Ir bonded Ir(II) compounds [[IrCl(cod)](2)(mu(2)-1,8-S(2)-nap)] 1, [[IrCl(cod)](2)(mu(2)-1,8-S(2)-2-(t)Bu-nap)] 2, [[IrCl(cod)](2)(mu(2)-1,8-S(2)-2,7-di-(t)Bu-nap)]] 3, [[IrCl(cod)](2)(mu(2)-4,5-S(2)-phenan)] 4, [[IrCl(cod)](2)(mu(2)-1-S,8-[S(O)]-nap)] 5 and [[IrCl(cod)](2)(mu(2)-1-S,8-[S(O)(2)]-nap)] 6 where the di-sulfur ligands act as bridges between the two Ir(II) metal centres. The compounds were obtained in moderate to good yields as orange or deep red powders or crystalline solids. Five of the new complexes have been structurally characterised and were found to have Ir-Ir bond lengths in the range 2.7630(8) to 2.8113(11) A.     

Synthesis and structures of a 3-sila-beta-diketiminatomagnesium bromide, ketenimide and triflate

The crystalline compounds [Mg(Br)(L)(thf)].0.5Et2O [L = {N(R)C(C6H3Me2-2,6)}2SiR, R = SiMe3] (1), [Mg(L){N=C=C(C(Me)=CH)2CH2}(D)2] [D = NCC6H3Me2-2,6 (2), thf (3)] and [{Mg(L)}2{mu-OSO(CF3)O-[mu}2] (4) were prepared from (a) Si(Br)(R){C(C6H3Me2-2,6)=NR}2 and Mg for (1), (b) [Mg(SiR3)2(thf)2] and 2,6-Me2C6H3CN (5 mol for (2), 3 mol for (3)), and (c) (2) + Me3SiOS(O)2CF3 for (4); a coproduct from (c) is believed to have been the trimethylsilyl ketenimide Me3SiN=C=C{C(Me)=CH}2CH2 (5).     

Synthesis of molybdenum complexes that contain "hybrid" triamidoamine ligands, [(hexaisopropylterphenyl-NCH2CH2)2NCH2CH2N-aryl]3-, and studies relevant to catalytic reduction of dinitrogen

In the Buchwald-Hartwig reaction between HIPTBr (HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3 = hexaisopropylterphenyl) and (H2NCH2CH2)3N, it is possible to obtain a 65% isolated yield of (HIPTNHCH2CH2)2NCH2CH2NH2. A second coupling then can be carried out to yield a variety of "hybrid" ligands, (HIPTNHCH2CH2)2NCH2CH2NHAr, where Ar = 3,5-Me2C6H3, 3,5-(CF3)2C6H3, 3,5-(MeO)2C6H3, 3,5-Me2NC5H3, 3,5-Ph2NC5H3, 2,4,6-i-Pr3C6H2, or 2,4,6-Me3C6H2. The hybrid ligands may be attached to Mo to yield [hybrid]MoCl species. From the monochloride species, a variety of other species such as [hybrid]MoN, {[hybrid]MoN2}Na, and {[hybrid]Mo(NH3)}+ can be prepared. [Hybrid]MoN2 species were prepared through oxidation of {[hybrid]MoN2}Na species with ZnCl2, but they could not be isolated. [Hybrid]Mo=N-NH species could be observed as a consequence of the protonation of {[hybrid]MoN2}- species, but they too could not be isolated as a consequence of a facile decomposition to yield dihydrogen and [hybrid]MoN2 species. Attempts to reduce dinitrogen catalytically led to little or no ammonia being formed from dinitrogen. The fact that no ammonia was formed from dinitrogen in the case of Ar = 3,5-Me2C6H3, 3,5-(CF3)2C6H3, or 3,5-(MeO)2C6H3 could be attributed to a rapid decomposition of intermediate [hybrid]Mo=N-NH species in the catalytic reaction, a decomposition that was shown in separate studies to be accelerated dramatically by 2,6-lutidine, the conjugate base of the acid employed in the attempted catalytic reduction. X-ray structures of [(HIPTNHCH2CH2)2NCH2CH2N{3,5-(CF3)2C6H3}]MoCl and [(HIPTNHCH2CH2)2NCH2CH2N(3,5-Me2C6H3)]MoN2}Na(THF)2 are reported.     

Tuning redox potentials of bis(imino)pyridine cobalt complexes: an experimental and theoretical study involving solvent and ligand effects

The structure and electrochemical properties of a series of bis(imino)pyridine Co(II) complexes (NNN)CoX(2) and [(NNN)(2)Co][PF(6)](2) (NNN = 2,6-bis[1-(4-R-phenylimino)ethyl]pyridine, with R = CN, CF(3), H, CH(3), OCH(3), N(CH(3))(2); NNN = 2,6-bis[1-(2,6-(iPr)(2)-phenylimino)ethyl]pyridine and X = Cl, Br) were studied using a combination of electrochemical and theoretical methods. Cyclic voltammetry measurements and DFT/B3LYP calculations suggest that in solution (NNN)CoCl(2) complexes exist in equilibrium with disproportionation products [(NNN)(2)Co](2+) [CoCl(4)](2-) with the position of the equilibrium heavily influenced by both the solvent polarity and the steric and electronic properties of the bis(imino)pyridine ligands. In strong polar solvents (e.g., CH(3)CN or H(2)O) or with electron donating substituents (R = OCH(3) or N(CH(3))(2)) the equilibrium is shifted and only oxidation of the charged products [(NNN)(2)Co](2+) and [CoCl(4)](2-) is observed. Conversely, in nonpolar organic solvents such as CH(2)Cl(2) or with electron withdrawing substituents (R = CN or CF(3)), disproportionation is suppressed and oxidation of the (NNN)CoCl(2) complexes leads to 18e(-) Co(III) complexes stabilized by coordination of a solvent moiety. In addition, the [(NNN)(2)Co][PF(6)](2) complexes exhibit reversible Co(II/III) oxidation potentials that are strongly dependent on the electron withdrawing/donating nature of the N-aryl substituents, spanning nearly 750 mV in acetonitrile. The resulting insight on the regulation of redox properties of a series of bis(imino)pyridine cobalt(II) complexes should be particularly valuable to tune suitable conditions for reactivity.     

First row divalent transition metal complexes of aryl-appended tris((pyridyl)methyl)amine ligands: syntheses, structures, electrochemistry, and hydroxamate binding properties

Divalent manganese, cobalt, nickel, and zinc complexes of 6-Ph(2)TPA (N,N-bis((6-phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; [(6-Ph(2)TPA)Mn(CH(3)OH)(3)](ClO(4))(2) (1), [(6-Ph(2)TPA)Co(CH(3)CN)](ClO(4))(2) (2), [(6-Ph(2)TPA)Ni(CH(3)CN)(CH(3)OH)](ClO(4))(2) (3), [(6-Ph(2)TPA)Zn(CH(3)CN)](ClO(4))(2) (4)) and 6-(Me(2)Ph)(2)TPA (N,N-bis((6-(3,5-dimethyl)phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; [(6-(Me(2)Ph)(2)TPA)Ni(CH(3)CN)(2)](ClO(4))(2) (5) and [(6-(Me(2)Ph)(2)TPA)Zn(CH(3)CN)](ClO(4))(2) (6)) have been prepared and characterized. X-ray crystallographic characterization of 1A.CH(3)()OH and 1B.2CH(3)()OH (differing solvates of 1), 2.2CH(3)()CN, 3.CH(3)()OH, 4.2CH(3)()CN, and 6.2.5CH(3)()CN revealed mononuclear cations with one to three coordinated solvent molecules. In 1A.CH(3)()OH and 1B.2CH(3)()OH, one phenyl-substituted pyridyl arm is not coordinated and forms a secondary hydrogen-bonding interaction with a manganese bound methanol molecule. In 2.2CH(3)()CN, 3.CH(3)()OH, 4.2CH(3)()CN, and 6.2.5CH(3)()CN, all pyridyl donors of the 6-Ph(2)TPA and 6-(Me(2)Ph)(2)TPA ligands are coordinated to the divalent metal center. In the cobalt, nickel, and zinc derivatives, CH/pi interactions are found between a bound acetonitrile molecule and the aryl appendages of the 6-Ph(2)TPA and 6-(Me(2)Ph)(2)TPA ligands. (1)H NMR spectra of 4 and 6 in CD(3)NO(2) solution indicate the presence of CH/pi interactions, as an upfield-shifted methyl resonance for a bound acetonitrile molecule is present. Examination of the cyclic voltammetry of 1-3 and 5 revealed no oxidative (M(II)/M(III)) couples. Admixture of equimolar amounts of 6-Ph(2)TPA, M(ClO(4))(2).6H(2)O, and Me(4)NOH.5H(2)O, followed by the addition of an equimolar amount of acetohydroxamic acid, yielded the acetohydroxamate complexes [((6-Ph(2)TPA)Mn)(2)(micro-ONHC(O)CH(3))(2)](ClO(4))(2) (8), [(6-Ph(2)TPA)Co(ONHC(O)CH(3))](ClO(4))(2) (9), [(6-Ph(2)TPA)Ni(ONHC(O)CH(3))](ClO(4))(2) (10), and [(6-Ph(2)TPA)Zn(ONHC(O)CH(3))](ClO(4))(2) (11), all of which were characterized by X-ray crystallography. The Mn(II) complex 8.0.75CH(3)()CN.0.75Et(2)()O exhibits a dinuclear structure with bridging hydroxamate ligands, whereas the Co(II), Ni(II), and Zn(II) derivatives all exhibit mononuclear six-coordinate structures with a chelating hydroxamate ligand.     

Reduction of the allylic substituents in Ni(I)(1,8-dipropenyl-1,4,8,11-tetraazacyclotetradecane)+ by the central Ni(I) in aqueous solutions

The complex Ni(II)(1,8,-di-2-propenyl-1,4,8,11-tetraazacyclotetradecane)(2+), (NiL(1))(2+), was synthesized. X-ray crystallography demonstrates that the complex obtained is the trans-III isomer. The allylic substituents shift the redox couples (NiL(1))(3+/2+) and (NiL(1))(2+/+) anodically relative to the corresponding couples for Ni(II)(1,4,8,11-tetraazacyclotetradecane)(2+), (NiL(2))(2+), as expected. Surprisingly, the lifetime of (NiL(1))(+) in neutral aqueous solutions is shorter than that of (NiL(2))(+). Pulse radiolysis experiments reveal that the allylic substituents are reduced by the central Ni(I) ion. The first step in this reduction is a general acid catalyzed process. The results suggest that this step involves schematically the reaction Ni(I)[bond]NCH(2)CH[double bond]CH(2)(+) + H(+) --> Ni(III)[bond]NCH2CH2CH(2)(2+). The latter transient decomposes slowly with a half-life time of several minutes. Preliminary results support the suggestion that (NiL(2))(+), or other Ni(I)L complexes of this family, might reduce many alkenes present in the solution.     

Mechanistic studies of platinum(II)-catalyzed ethylene dimerization: determination of barriers to migratory insertion in diimine Pt(II) hydrido ethylene and ethyl ethylene intermediates

The diimine platinum(II) ethylene hydride complex [(N/\N)Pt(H)(ethylene)][BAr'4] (1, N/\N = [(2,6-Me2C6H3)N=C(An)-C(An)=N(2,6-Me2C6H3)], An = 1,8-naphthalenediyl, Ar' = 3,5-(CF3)2C6H3) was prepared by protonation of the diethyl complex (N/\N)PtEt2 with [H(OEt2)2][BAr'4]. The energy barrier to interchange of the platinum hydride with the olefinic hydrogens in 1 was determined to be 19.2 kcal/mol by spin saturation transfer experiments. Complex 1 initiates ethylene dimerization; the ethyl ethylene complex (N/\N)Pt(Et)(ethylene)+ (2) has been identified as the catalyst resting state. Trapping of 1 by ethylene to yield 2 is a second-order process; kinetic studies suggest this occurs via trapping of a reversibly formed beta-agostic ethyl complex. Complex 2 has been isolated and characterized by X-ray crystallography. The barrier to migratory insertion of 2, the turnover-limiting step in catalysis, was determined to be 29.8 kcal/mol. The 1-butene hydride complex, (N/\N)Pt(H)(1-butene)+ (3), is a key intermediate in the dimerization cycle and has also been isolated and characterized. Surprisingly rapid rates of degenerate associative exchange of free ethylene with bound ethylene in complexes 1 and 2 as well as the rate of degenerate exchange of free nitrile with bound nitrile in (N/\N)Pt(Et)(CH3CN)+ are reported.     

Syntheses and reactivities of disubstituted and trisubstituted fluorous pyridines with high fluorous phase affinities: solid state,liquid crystal,and ionic liquid-phase properties

Reactions of 2,6-dibromo-, 3,5-dibromo-, and 2,4,6-tribromopyridine with IZnCH(2)CH(2)R(f8) (R(f8) = (CF(2))(7)CF(3)) in THF at 65 degrees C in the presence of trans-Cl(2)Pd(PPh(3))(2) (5 mol %) gave the fluorous pyridines 2,6- and 3,5-NC(5)H(3)(CH(2)CH(2)R(f8))(2) (1 and 2; 85%, 31%) and 2,4,6-NC(5)H(2)(CH(2)CH(2)R(f8))(3) (3, 61%). Reaction of 2,6-pyridinedicarboxaldehyde with [Ph(3)PCH(2)CH(2)R(f8)](+)I(-)/K(2)CO(3) (p-dioxane/H(2)O, 95 degrees C) gave 2,6-NC(5)H(3)(CH[double bond]CHCH(2)R(f8))(2) (95%; 70:30 ZZ/ZE), which was treated with H(2) (1 atm, 12 h) and 10% Pd/C to yield 2,6-NC(5)H(3)(CH(2)CH(2)CH(2)R(f8))(2) (5, 95%), a higher homologue of 1. Longer reaction times afforded piperidine cis-2,6-HNC(5)H(8)(CH(2)CH(2)CH(2)R(f8))(2) (6, 98%). The stereochemistry was established by NMR analysis of the N-benzylpiperidine. Pyridines 1-3 and 5 are low-melting white solids with CF(3)C(6)F(11)/toluene partition coefficients (24 degrees C) of 93.8:6.2, 93.9:6.1, >99.7:<0.3, and 90.4:9.6, respectively (6, 93.6:6.4). Reaction of 1 and CF(3)SO(3)H gave a pyridinium salt, and Cl(2)Pd(NCCH(3))(2) (0.5 equiv) yielded trans-Cl(2)Pd(1)(2). The crystal structure of the former, which also exhibited liquid crystalline and ionic liquid phases, was determined.     

Ni(eta 3-CH2C(CH3)CH2)(SbPh3)3][BAr'4]: an extremely active cationic allyl nickel-stibine catalyst for the oligomerization of styrene

The pseudotetrahedral, formally 5-coordinate complex [Ni(eta 3-CH2C(CH3)CH2)(SbPh3)3][BAr'4] (Ar' = 3,5-C6H3(CF3)2) as well as the 4-coordinate derivative [Ni(eta 3-CH2C(CH3)CH2)(AsPh3)2][BAr'4] act as extremely efficient catalysts for the oligomerization of styrene.     

Adduct formation or metathesis reactions of silver complexes containing the fluorinated ligands [HB(3,5-(CF3)2Pz)3]- and [CF3SO3]-: formation of silver adducts containing unsupported silver-germanium bonds

A mixture of [HB(3,5-(CF3)2Pz)3]Ag(eta 2-toluene) and [(Me)2ATI]GeCl in CH2Cl2, rather than undergoing metathesis, formed a 1:1 adduct [HB(3,5-(CF3)2Pz)3]Ag<--GeCl[(Me)2ATI] (1, where [HB(3,5-(CF3)2Pz)3] = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate and [(Me)2ATI] = N-methyl-2-(methylamino)troponiminate) featuring a silver-germanium bond. Solutions of 1 (in CH2Cl2 or toluene) did not precipitate AgCl even after several days. However, it easily underwent metathesis with CF3SO3Ag, leading to the chloride-free product [HB(3,5-(CF3)2Pz)3]Ag<--Ge(OSO2CF3)[(Me)2ATI] (2). Compounds 1 and 2 were characterized by X-ray crystallography. The Ag-Ge bond distances of 1 and 2 are 2.4215(9) and 2.4116(10) A, respectively.     

(Fluoren-9-ylidene)methanedithiolato complexes of platinum: synthesis, reactivity, and luminescence

Platinum(II) complexes with (fluoren-9-ylidene)methanedithiolato and its 2,7-di-tert-butyl- and 2,7-dimethoxy-substituted analogues were obtained by reacting different chloroplatinum(II) precursors with the piperidinium dithioates (pipH)[(2,7-R2C12H6)CHCS2] [R = H (1a), t-Bu (1b), or OMe (1c)] in the presence of piperidine. The anionic complexes Q2[Pt{S(2)C=C(C12H6R(2)-2,7)}2] [R = H, (Pr(4)N)(2)2a; R = t-Bu, (Pr4N)(2)2b, (Et4N)(2)2b; R = OMe, (Pr4N)(2)2c] were prepared from PtCl(2), piperidine, the corresponding QCl salt, and 1a-c in molar ratio 1:2:2:2. In the absence of QCl, the complexes (pipH)(2)2b and [Pt(pip)(4)]2b were isolated depending on the PtCl(2):pip molar ratio. The neutral complexes [Pt{S2C=C(C12H6R(2)-2,7)L(2)] [L = PPh(3), R = H (3a), t-Bu (3b), OMe (3c); L = PEt(3), R = H (4a), t-Bu (4b), OMe (4c); L(2) = dbbpy, R = H (5a), t-Bu (5b), OMe (5c) (dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridyl)] were similarly prepared from the corresponding precursors [PtCl2L2] and 1a-c in the presence of piperidine. Oxidation of Q(2)2b with [FeCp2]PF6 afforded the mixed Pt(II)-Pt(IV) complex Q2[Pt2{S2C=C[C12H6(t-Bu)(2)-2,7]}4] (Q(2)6, Q = Et4N+, Pr4N+). The protonation of (Pr4N)(2)2b with 2 equiv of triflic acid gave the neutral dithioato complex [Pt2{S2CCH[C12H6(t-Bu)(2)-2,7]}4] (7). The same reaction in 1:1 molar ratio gave the mixed dithiolato/dithioato complex Pr4N[Pt{S2C=C[C12H6(t-Bu)(2)-2,7]}{S2CCH[C12H6(t-Bu)(2)-2,7]}] (Pr(4)N8) while the corresponding DMANH+ salt was obtained by treating 7 with 2 equiv of 1,8-bis(dimethylamino)naphthalene (DMAN). The crystal structures of 3b and 5c.CH2Cl2 have been solved by X-ray crystallography. All the platinum complexes are photoluminescent at 77 K in CH2Cl2 or KBr matrix, except for Q(2)6. Compounds 5a-c and Q8 show room-temperature luminescence in fluid solution. The electronic absorption and emission spectra of the dithiolato complexes reveal charge-transfer absorption and emission energies which are significantly lower than those of analogous platinum complexes with previously described 1,1-ethylenedithiolato ligands and in most cases compare well to those of 1,2-dithiolene complexes.     

Two-coordinate d9 complexes. synthesis and oxidation of NHC nickel(I) amides

Reaction of the d9-d9 Ni(I) monochloride dimer, [(IPr)Ni(mu-Cl)]2 (1), with NaN(SiMe3)2 and LiNHAr (Ar = 2,6-diisopropylphenyl) gives the novel monomeric, 2-coordinate Ni(I) complexes (IPr)Ni{N(SiMe3)2} (2) and (IPr)Ni(NHAr) (3). Reaction of 2 with Cp2Fe+ results in its 1-e- oxidation followed by beta-Me elimination to give a base-stabilized iminosilane complex [(IPr)Ni(CH3){kappa1-N(SiMe3)=SiMe2.Et2O}][BArF4] (6). Oxidation of 3 gives [(IPr)Ni(eta3-NHAr)(THF)][BArF4] (4), which upon loss of THF affords dimeric [(IPr)Ni(N,eta3:NHC6iPr2H3)]2[BArF4]2 (5).     

Reactions of vinyl acetate and vinyl trifluoroacetate with cationic diimine Pd(II) and Ni(II) alkyl complexes: identification of problems connected with copolymerizations of these monomers with ethylene

Vinyl acetate (VA) and vinyl trifluoroacetate (VA(f)) react with [(NwedgeN)Pd(Me)(L)][X] (M = Pd, Ni, (NwedgeN) = N,N'-1,2-acenaphthylenediylidene bis(2,6-dimethyl aniline), Ar(f) = 3,5-trifluoromethyl phenyl, L = Ar(f)CN, Et2O; X = B(Ar(f))4-, SbF6-) to form pi-adducts 3 and 5 at -40 degrees C. Binding affinities relative to ethylene have been determined. Migratory insertion occurs in a 2,1 fashion (DeltaG++ = 19.4 kcal/mol, 0 degrees C for VA, and 17.4 kcal/mol, -40 degrees C for VA(f)) to yield five-membered chelate complexes [(NwedgeN)Pd(kappa2-CH(Et)(OC(O)-CH3))]+, 4, and [(NwedgeN)Pd(kappa2-CH(Et)(OC(O)CF3))]+, 6. When VA is added to [(NwedgeN)Ni(CH3)]+, an equilibrium mixture of an eta2 olefin complex, 8c, and a kappa-oxygen complex, 8o, results. Insertion occurs from the eta2 olefin complex, 8c (DeltaG++ = 15.5 kcal/mol, -51 degrees C), in both a 2,1 and a 1,2 fashion to generate a mixture of five- and six-membered chelates, 9(2,1) and 9(1,2). VA(f) inserts into the Ni-CH3 bond (-80 degrees C) to form a five-membered chelate with no detectable intermediate. Thermolysis of the Pd chelates results in beta-acetate elimination from 4 (DeltaG++ = 25.5 kcal/mol, 60 degrees C) and beta-trifluoroacetate elimination from 6 (DeltaG = 20.5 kcal/mol, 10 degrees C). The five-membered Ni chelate, 9(2,1), is quite stable at room temperature, but the six-membered chelate, 9(1,2), undergoes beta-elimination at -34 degrees C. Treatment of the OAc(f) containing Pd chelate 6 with ethylene results in complete opening to the pi-complex [(NwedgeN)Pd(kappa2-CH(Et)(OAc(f)))(CH2CH2)]+ (OAc(f) = OC(O)CF3), 18, while reaction of the OAc containing Pd chelate 4 with ethylene establishes an equilibrium between 4 and the open form 16, strongly favoring the closed chelate 4 (DeltaH = -4.1 kcal/mol, DeltaS = -23 eu, K = 0.009 M(-1) at 25 degrees C). The open chelates undergo migratory insertion at much slower rates relative to those of the simple (NwedgeN)Pd(CH3)(CH2CH2)+ analogue. These quantitative studies provide an explanation for the behavior of VA and VA(f) in attempted copolymerizations with ethylene.     

Luminescence enhancement and tuning via multiple cooperative supramolecular interactions in an ion-paired multinuclear complex

[(3,5-(CF(3))(2)Pz)(AgL)(2)](+)[Ag(5)(3,5-(CF(3))(2)Pz)(6)(CH(3)CN)](-) (L = 2-(N,N-diethylanilino-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine) shows bright and tunable emissions influenced by its supramolecular structure. Columnar stacks are assembled via cooperative interactions that include Ag(I)···Ag(I) argentophilic bonding, π···π stacking and Ag(I)···π interactions.