P(MeNCH2CH2)3N: an efficient catalyst for the desilylation of tert-butyldimethylsilyl ethers

tert-Butyldimethylsilyl (TBDMS) ethers of primary, secondary, and tertiary alcohols and phenolic TBDMS ethers are desilylated to their corresponding alcohols and phenols, respectively, in DMSO, at 80 degrees C, in 68-94% yield in the presence of 0.2-0.4 equiv of P(MeNCH2CH2)3N. Using P(i-PrNCH2-CH2)3N as the catalyst, 85-97% yields of desilylated alcohols were obtained from TBDMS ethers of 1-octanol, 2-phenoxyethanol, and racemic alpha-phenyl ethanol. These are the first examples of desilylations of silyl ethers catalyzed by nonionic bases. Both catalysts were much less effective for the desilylation of tert-butyldiphenylsilyl (TBDPS) ethers (22-45% yield) under the same conditions as used for TBDMS ethers. Possible pathways involving nucleophilic attack of the anion of the solvent molecule (generated by the catalyst) at the Si-O bond of silyl ether or a prior activation of the silyl ether by the catalyst via a P-Si interaction followed by nucleophilic attack of the solvent anion are proposed on the basis of 1H and 31P NMR experimental data.     

PhCH=P[MeNCH(2)CH(2)](3)N: a novel ylide for quantitative E selectivity in the Wittig reaction

PhCH=P[MeNCH(2)CH(2)](3)N (1), a semi-stabilized ylide prepared from the commercially available nonionic base P[MeNCH(2)CH(2)](3)N, reacts with aldehydes to give alkenes in high yield with quantitative E selectivity. In contrast with other ylides, this E selectivity is maintained despite changes in the metal ion of the ionic base used to deprotonate 1, temperature, and solvent polarity. In conjunction with structural parameters gained from the X-ray molecular structure of 1, the pathway to E selectivity in these reactions is rationalized by the Vedejs model of Wittig reaction stereochemistry.     

Chiral Auxiliary-Bearing Isocyanides as Synthons: Synthesis of Strongly Fluorescent (+)-5-(3,4-Dimethoxyphenyl)-4-[[N- [(4S)-2-oxo-4-(phenylmethyl)-2-oxazolidinyl]]carbonyl]oxazole and Its Enantiomer

Both (4S-(+)-3-(isocyanoacetyl)-4-(phenylmethyl)-2-oxazolidinone (R)-1 and its enantiomer (S)-1 have been synthesized as potentially useful synthons in asymmetric synthesis. Optically active (+)-5-(3,4-dimethoxyphenyl)-4-[[N-[(4S)-2-oxo-4-(phenylmethyl)-2-oxazolidinyl]]carbonyl] oxazole (S)-2 and its enantiomer (R)-2 obtained by treating 3,4-dimethoxybenzoyl chloride with (S)-1 and (R)-1, respectively, in the presence of the nonionic superbase P(MeNCH(2)CH(2))(3)N, have high fluorescence quantum yields. The molecular structure of (S)-2 obtained by X-ray means is also presented.     

Imido Complexes Derived from the Reactions of Niobium and Tantalum Pentachlorides with Primary Amines: Relevance to the Chemical Vapor Deposition of Metal Nitride Films

Reactions of niobium and tantalum pentachlorides with tert-butylamine (>/=6 equiv) in benzene afford the dimeric imido complexes [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) (90%) and [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) (79%). The niobium complex exists as two isomers in solution, while the tantalum complex is composed of three major isomers and at least two minor isomers. Analogous treatments with isopropylamine (>/=7 equiv) give the monomeric complexes NbCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2) (84%) and TaCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2) (84%). The monomeric complexes are unaffected by treatment with excess isopropylamine, while the dimeric complexes are cleaved to the monomers MCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)(2) upon addition of excess tert-butylamine in chloroform solution. Treatment of niobium and tantalum pentachlorides with 2,6-diisopropylaniline affords insoluble precipitates of [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (100%) and [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[TaCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (100%), which react with 4-tert-butylpyridine to afford the soluble complexes [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (45%) and [4-t-C(4)H(9)C(5)H(4)NH](2)[TaCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (44%). Sublimation of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), MCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2), and [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[MCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] leads to decomposition to give [MCl(3)(NR)(NH(2)R)](2) as sublimates (32-49%), leaving complexes of the proposed formulation MCl(NR)(2) as nonvolatile residues. By contrast, [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) sublimes without chemical reaction. Analysis of the organic products obtained from thermal decomposition of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) showed isobutylene and tert-butylamine in a 2.2:1 ratio. Mass spectra of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), and [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2) showed the presence of dimeric imido complexes, monomeric imido complexes, and nitrido complexes, implying that such species are important gas phase species in CVD processes utilizing these molecular precursors. The crystal structures of [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))], [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2), [NbCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2), and [TaCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) were determined. [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] crystallizes in the space group P2(1)/c with a = 12.448(3) ?, b = 10.363(3) ?, c = 28.228(3) ?, beta = 94.92(1) degrees, V = 3628(5) ?(3), and Z = 4. [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2) crystallizes in the space group P2(1)/c with a = 9.586(4) ?, b = 12.385(4) ?, c = 11.695(4) ?, beta = 112.89(2) degrees, V = 1279.0(6) ?(3), and Z = 2. [NbCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) crystallizes in the space group P2(1)/n with a = 10.285(3) ?, b = 11.208(3) ?, c = 23.867(6) ?, beta = 97.53 degrees, V = 2727(1) ?(3), and Z = 2. [TaCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) crystallizes in the space group P2(1)/n with a = 10.273(1) ?, b = 11.241(2) ?, c = 23.929(7) ?, beta = 97.69(2) degrees, V = 2695(2) ?(3), and Z = 2. These findings are discussed in the context of niobium and tantalum nitride film depositions from molecular precursors.     

Reductive elimination/oxidative addition of carbon-hydrogen bonds at Pt(IV)/Pt(II) centers: mechanistic studies of the solution thermolyses of Tp(Me2)Pt(CH3)2H

Reductive elimination of methane occurs upon solution thermolysis of kappa(3)-Tp(Me)2Pt(IV)(CH(3))(2)H (1, Tp(Me)2 = hydridotris(3,5-dimethylpyrazolyl)borate). The platinum product of this reaction is determined by the solvent. C-D bond activation occurs after methane elimination in benzene-d(6), to yield kappa(3)-Tp(Me)2Pt(IV)(CH(3))(C(6)D(5))D (2-d(6)), which undergoes a second reductive elimination/oxidative addition reaction to yield isotopically labeled methane and kappa(3)-Tp(Me)2Pt(IV)(C(6)D(5))(2)D (3-d(11)). In contrast, kappa(2)-Tp(Me)2Pt(II)(CH(3))(NCCD(3)) (4) was obtained in the presence of acetonitrile-d(3), after elimination of methane from 1. Reductive elimination of methane from these Pt(IV) complexes follows first-order kinetics, and the observed reaction rates are nearly independent of solvent. Virtually identical activation parameters (DeltaH(++)(obs) = 35.0 +/- 1.1 kcal/mol, DeltaS(++)(obs) = 13 +/- 3 eu) were measured for the reductive elimination of methane from 1 in both benzene-d(6) and toluene-d(8). A lower energy process (DeltaH(++)(scr) = 26 +/- 1 kcal/mol, DeltaS(++)(scr) = 1 +/- 4 eu) scrambles hydrogen atoms of 1 between the methyl and hydride positions, as confirmed by monitoring the equilibration of kappa(3)-Tp(Me)()2Pt(IV)(CH(3))(2)D (1-d(1)()) with its scrambled isotopomer, kappa(3)-Tp(Me)2Pt(IV)(CH(3))(CH(2)D)H (1-d(1'). The sigma-methane complex kappa(2)-Tp(Me)2Pt(II)(CH(3))(CH(4)) is proposed as a common intermediate in both the scrambling and reductive elimination processes. Kinetic results are consistent with rate-determining dissociative loss of methane from this intermediate to produce the coordinatively unsaturated intermediate [Tp(Me)2Pt(II)(CH(3))], which reacts rapidly with solvent. The difference in activation enthalpies for the H/D scrambling and C-H reductive elimination provides a lower limit for the binding enthalpy of methane to [Tp(Me)2Pt(II)(CH(3))] of 9 +/- 2 kcal/mol.     

Studies of mixed surfactant solutions of cationic dimeric (gemini) surfactant with nonionic surfactant C12E6 in aqueous medium

The interaction between the alkanediyl-alpha,omega-type cationic gemini surfactant, [(C(16)H(33)N(+)(CH(3))(2)(CH(2))(4)N(+)(CH(3))(2)C(16)H(33))2Br(-)], 16-4-16 and the conventional nonionic surfactant [CH(3)(CH(2))(10)CH(2)(OCH(2)CH(2))(6)OH], C(12)E(6) in aqueous medium has been investigated. The critical micelle concentrations of different mixtures have been measured by surface tension using a du Nouy tensiometer in aqueous solution at different temperatures (303, 308, and 313 K). Maximum surface excess (Gamma(max)) and minimum area per molecule (A(min)) were evaluated from a surface tension vs log(10)C (C is concentration) plot. The cmc value of the mixture was used to compute beta(m), the interaction parameter. The beta(sigma), the interaction parameter at the monolayer air-water interface, was also calculated. We observed synergism in 16-4-16/C(12)E(6) system at all concentration ratios. The micelle aggregation number (N(agg)) has been measured using a steady state fluorescence quenching method at a total surfactant concentration approximately 2 mM at 25 degrees C. The micropolarity and the binding constant (K(sv)) of mixed systems were determined from the ratio of intensity of peaks (I(1)/I(3)) of the pyrene fluorescence emission spectrum. The micellar interiors were found to be reasonably polar. We also found, using Maeda's concept, that the chain-chain interactions are very important in this system.     

Methyl Tin(IV) derivatives of HOTeF(5) and HN(SO(2)CF(3))(2): a solution multinuclear NMR study and the X-ray crystal structures of (CH(3))(2)SnCl(OTeF(5)) and [(CH(3))(3)Sn(H(2)O)(2)][N(SO(2)CF(3))(2)

The new tin(IV) species (CH(3))(2)SnCl(OTeF(5)) was prepared via either the solvolysis of (CH(3))(3)SnCl in HOTeF(5) or the reaction of (CH(3))(3)SnCl with ClOTeF(5). It was characterized by NMR and vibrational spectroscopy, mass spectrometry, and single crystal X-ray diffraction. (CH(3))(2)SnCl(OTeF(5)) crystallizes in the monoclinic space group P2(1)/n (a = 5.8204(8) A, b =10.782(1) A, c =15.493(2) A, beta = 91.958(2) degrees, V = 971.7(2) A(3), Z = 4). NMR spectroscopy of (CH(3))(3)SnX, prepared from excess Sn(CH(3))(4) and HX (X = OTeF(5) or N(SO(2)CF(3))(2)), revealed a tetracoordinate tin environment using (CH(3))(3)SnX as a neat liquid or in dichloromethane-d(2) (CD(2)Cl(2)) solutions. In acetone-d(6) and acetonitrile-d(3) (CD(3)CN) solutions, the tin atom in (CH(3))(3)SnOTeF(5) was found to extend its coordination number to five by adding one solvent molecule. In the strong donor solvent DMSO, the Sn-OTeF(5) bond is broken and the (CH(3))(3)Sn(O=S(CH(3))(2))(2)(+) cation and the OTeF(5)(-) anion are formed. (CH(3))(3)SnOTeF(5) and (CH(3))(3)SnN(SO(2)CF(3))(2) react differently with water. While the Te-F bonds in the OTeF(5) group of (CH(3))(3)SnOTeF(5) undergo complete hydrolysis that results in the formation of [(CH(3))(3)Sn(H(2)O)(2)](2)SiF(6), (CH(3))(3)SnN(SO(2)CF(3))(2) forms the stable hydrate salt [(CH(3))(3)Sn(H(2)O)(2)][N(SO(2)CF(3))(2)]. This salt crystallizes in the monoclinic space group P2(1)/c (a = 7.3072(1) A, b =13.4649(2) A, c =16.821(2) A, beta = 98.705(1) degrees, V = 1636.00(3) A(3), Z = 4) and was also characterized by NMR and vibrational spectroscopy.     

Ni(II), Pd(II) and Pt(II) complexes of PNP and PSP tridentate amino-phosphine ligands

The ligands D((CH(2))(2)NHPiPr(2))(2) (D = NH 1, S 2) react with (dme)NiCl(2) or (PhCN)(2)MCl(2) (M = Pd, Pt) to give complexes of the form [D((CH(2))(2)NHPiPr(2))(2)MX]X (X = Cl, I; M = Ni, Pd, Pt) which were converted to corresponding iodide derivatives by reaction with Me(3)SiI. Reaction of 1 or 2 with (COD)PdMeCl affords facile routes to [κ(3)P,N,P-NH((CH(2))(2)NHPiPr(2))(2)PdMe]Cl (8a) and [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)PdMe]Cl (9a) in high yields. An alternative synthetic approach involves oxidative addition of MeI to a M(0) precursor yielding [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)NiMe]I (10), [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MMe]I (M = Pd 8b Pt 11) and [κ(3)P,S,P-S(CH(2)CH(2)NHPiPr(2))(2)MMe]I (M = Pd 9b, Pt 12). Alternatively, use of NEt(3)HCl in place of MeI produces the species [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MH]X (X = Cl, M = Ni 13a, Pd 14a, Pt 16a). The analogs containing 2; [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)MH]X (M = Pd, X = PF(6)15: M = Pt, X = Br, 17a, PF(6)17b) were also prepared in yields ranging from 74-93%. In addition, aryl halide oxidative addition was also employed to prepare [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MC(6)H(4)F]Cl (M = Ni 18, Pd 19) and [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)Pd(C(6)H(4)F)]Cl (20). Crystal structures of 3a, 4a, 5a, 6a, 8a, 9a, 14b and 16b are reported.     

Correlation of Solution and Gas Phase Complexation Assessed by Electrospray Ionization Mass Spectrometry: Application to One-, Two-, and Three-Ring Macrocycles

Electrospray ionization mass spectrometry (ESI-MS) was used to probe multiple cation complexation by C(12)H(25)(CH(2))(12)(CH(2))(12)C(12)H(25), 2, and <18N>CH(2)C(6)H(4)CH(2), 3. Complexation of two cations (2Na(+), 2 K(+), or Na(+) and K(+)) by 3 and three cations by 2 (3 Na(+), 3 K(+), and mixtures) as well as mixed proton-metallic cation complexes of both were observed. The K(+)/Na(+) cation-binding selectivity of 18-crown-6 was studied by ESI-MS of a methanol solution, and the selectivity profile was favorably compared with data obtained previously by ion-selective electrode techniques in the same solvent.     

Stabilization of the P(CF(3))(2)(-) ion as a reversible CS(2) adduct, [P(CF(3))(2)CS(2)](-), and its potential use as a nucleophilic P(CF(3))(2)(-) source: synthesis and structure of [18-crown-6-K][P(C(6)F(5))(2)CS(2)

The bis(trifluoromethyl)phosphanide ion, P(CF(3))(2)(-), decomposes slowly above -30 degrees C in CH(2)Cl(2) and THF solution. An increase of the thermal stability of the P(CF(3))(2)(-) moiety is observed if excess CS(2) is added. The P(CF(3))(2)(-) moiety is stabilized because of the formation of the bis(trifluoromethyl)phosphanodithioformate anion. Solutions of a [P(CF(3))(2)CS(2)](-) salt still act as a source of P(CF(3))(2)(-), even in the presence of excess of CS(2). The stable compound [18-crown-6-K][P(CF(3))(2)CS(2)] was characterized by multinuclear NMR spectroscopy, elemental analysis, and vibrational spectroscopy in combination with quantum chemical calculations. The thermally unstable P(C(6)F(5))(2)(-) ion decomposes even at -78 degrees C in solution giving polymeric material. The intermediate formation of the bis(pentafluorophenyl)phosphanide anion in the presence of excess of CS(2) allows the isolation of [18-crown-6-K][P(C(6)F(5))(2)CS(2)]. The novel compound crystallizes with one solvent molecule CH(2)Cl(2) in the monoclinic space group P2(1)/n with a = 1151.8(1) pm, b = 1498.1(2) pm, c = 2018.2(2) pm, beta = 102.58(1) degrees, and Z = 4. Optimized geometric parameters of the [P(C(6)F(5))(2)CS(2)](-) ion at the B3PW91/6-311G(d) level of theory are in excellent agreement with the experimental values.     

Acylation of 2,5-dimethoxycarbonyl[60]fulleropyrrolidine and synthesis of its multifullerene derivatives

2,5-Dimethoxycarbonyl[60]fulleropyrrolidine (1) is acylated with various chlorocarbonyl compounds to give fullerene derivatives with the general formula C(60)(MeOOCCH)(2)NC(O)R, R = (CH(2))(5)Br, (CH(2))(8)C(O)Cl (3), (CH(2))(4)C(O)Cl, or cis-C(6)H(4)(C(O)Cl. The monoacylated sebacoyl derivative 3 readily reacts with alcohols and amines such as methanol, diethylamine, glycine methyl ester, and aza-18-crown-6 through the remaining chlorocarbonyl group. Chromatography of 3 on silica gel converts it into the corresponding acid C(60)(MeOOCCH)(2)NC(O)(CH(2))(8)COOH (4). Treating 4 with PCl(5) regenerates the precursor 3 quantitatively. Piperazine reacts with 4 in the presence of DCC and BtOH to form a bisfullerene derivative in which two sebacoyl chains and the piperazine act as the bridge between two molecules of 1. Other molecules with multifunctional groups react with 4 similarly to form multifullerene derivatives. NMR data indicate that the rotation of the relatively bulky phthaloyl group is hindered around the amide bond N [bond] C(O), the rotation barrier of which is 15.06 kcal/mol. The relative stereochemistry of the 2,5-dimethoxycarbonyl groups is established by (1)H NMR spectra and further confirmed by resolution of the enantiomeric 2,5-trans-isomer of the starting material 1.     

Inherent stability limits of intramolecular boron nitrogen Lewis acid-base pairs

The reaction of (C(6)F(5))(2)BH (1) with N,N-dimethylallylamine (2), N,N-diethylallylamine (3) and 1-allylpiperidine (4) afforded the five-membered ring systems (C(6)F(5))(2)B(CH(2))(3)NR(2) (R = Me (5), Et (6)) and (C(6)F(5))(2)B(CH(2))(3)N(CH(2))(5) (7) with an intramolecular dative B-N bond. A different product was obtained from the reaction of (C(6)F(5))(2)BH (1) with N,N-diisopropylallylamine (8), which afforded the seven-membered ring system (C(6)F(5))(2)B(CH(2))(3)N(iPr)CH(Me)CH(2) (9) under extrusion of dihydrogen. All compounds were characterised by elemental analysis, NMR spectroscopy and single-crystal X-ray diffraction experiments. Density functional theory (DFT) studies were performed to rationalise the different reaction mechanism for the formation of products 6 and 9. The bonding situation of compound 9 was analysed in terms of its electron density topology to describe the delocalised nature of a borane-enamine adduct.     

P(RNCH(2)CH(2))(3)N: efficient 1,4-addition catalysts

The 1,4-addition of primary alcohols, higher nitroalkanes, and a Schiff's base of an alpha-amino ester to alpha,beta-unsaturated substrates produces the corresponding products in moderate to excellent yields when carried out at -63 to 70 degrees C in the presence of catalytic amounts of the nonionic strong bases P(RNCH(2)CH(2))(3)N (R = Me, i-Pr, i-Bu) in isobutyronitrile. Diastereoselectivity for the anti form of the product is high in the case of the Schiff's base in the absence of lithium ion. These catalysts are easily removed from the product by either column filtration through silica gel or via aqueous workup.     

Synthesis and structure of new carborane-substituted cyclotriphosphazenes

The reactions of [N(3)P(3)Cl(6)] with one, two, or three equivalents of the difunctional 1,2-closo-carborane C(2)B(10)H(10)[CH(2)OH](2) and K(2)CO(3) in acetone have been investigated. These reactions led to the new spiro-closo-carboranylphosphazenes gem-[N(3)P(3)Cl(6-2n)[(OCH(2))(2)C(2)B(10)H(10)](n)] (n=1 (1), 2 (2)) and the first fully carborane-substituted phosphazene gem-[N(3)P(3)[(OCH(2))(2)C(2)B(10)H(10)](3)] (3). A bridged product, non-gem-[N(3)P(3)Cl(4)[(OCH(2))(2)C(2)B(10)H(10)]] (4), was also detected. The reaction of the well-known spiro derivatives [N(3)P(3)Cl(2)(O(2)C(12)H(8))(2)] and [N(3)P(3)Cl(4)(O(2)C(12)H(8))] with the same carborane-diol and K(2)CO(3) in acetone gave the new compounds gem-[N(3)P(3)(O(2)C(12)H(8))(3-n)[(OCH(2))(2)C(2)B(10)H(10)](n)] (n=1 (5) or 2 (6), respectively), without signs of intra- or intermolecularly bridged species. Upon treatment with NEt(3) in acetone, compound 5 was converted into the corresponding nido-carboranylphosphazene. However, the reaction of gem-[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(10)H(10)]] (5) with NEt(3) in ethanol instead of acetone proceeded in a different manner to give the new compound (NHEt(3))(2)[N(3)P(3)(O(2)C(12)H(8))(2)(O)[OCH(2)C(2)B(9)H(10)CH(2)OCH(2)CH(3)]] (7). For compounds with two 2,2'-dioxybiphenyl units, gem-[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(10)H(10)]] (5), (NHEt(3))[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(9)H(10)]] (8), and (NHEt(3))(2)[N(3)P(3)(O(2)C(12)H(8))(2)(O)[OCH(2)C(2)B(9)H(10)CH(2)OCH(2)CH(3)]] (7), a mixture of different stereoisomers may be expected. However, for 5 and 7 only the meso compounds seem to be formed, with the same (R,S)-configuration as in the precursor [N(3)P(3)Cl(2)(O(2)C(12)H(8))(2)]. The reaction of 5 to give 8 seems to proceed with a change of configuration at one phosphorus center, giving a racemic mixture. The crystal structures of the nido-carboranylphosphazenes 7 and 8 have been confirmed by X-ray diffraction methods.     

Second generation fluorous DEAD reagents have expanded scope in the Mitsunobu reaction and retain convenient separation features

First generation fluorous DEAD reagent bis(perfluorohexylethyl)azo dicarboxylate (C(6)F(13)(CH(2))(2)O(2)CN=NCO(2)(CH(2))(2)C(6)F(13), F-DEAD-1) has been shown to underperform relative to diisopropylazodicarboxylate in difficult Mitsunobu reactions involving hindered alcohols or less acidic pronucleophiles (phenols). Two new second generation fluorous reagents bearing propylene spacers instead of the ethylene spacers show expanded reaction scope while retaining the easy fluorous separation features. Byproducts from "half fluorous" reagent perfluorooctylpropyl tert-butyl azo dicarboxylate (C(8)F(17)(CH(2))(3)O(2)CN=NCO2(t)Bu, F-DEAD-2) can be removed by fluorous flash chromatography, and byproducts from bis(perfluorohexylpropyl)azo dicarboxylate (C(6)F(13)(CH(2))(3)O(2)CN=NCO(2)(CH(2))(3)C(6)F(13), F-DEAD-3) can be removed by fluorous solid-phase extraction. The new reagents promise to provide general and complementary solutions for separation problems in Mitsunobu reactions without restricting reaction scope.     

Synthesis of triamidoamine ligands of the type (ArylNHCH(2)CH(2))(3)N and molybdenum and tungsten complexes that contain an [ArylNCH(2)CH(2))(3)N]3- ligand

Aryl bromides react with (H(2)NCH(2)CH(2))(3)N in a reaction catalyzed by Pd(2)(dba)(3) in the presence of BINAP and NaO-t-Bu to give the arylated derivatives (ArylNHCH(2)CH(2))(3)N [Aryl = C(6)H(5) (1a), 4-FC(6)H(4) (1b), 4-t-BuC(6)H(4) (1c), 3,5-Me(2)C(6)H(3) (1d), 3,5-Ph(2)C(6)H(3) (1e), 3,5-(4-t-BuC(6)H(4))(2)C(6)H(3) (1f), 2-MeC(6)H(4) (1g), 2,4,6-Me(3)C(6)H(2) (1h)]. Reactions between (ArNHCH(2)CH(2))(3)N (Ar = C(6)H(5), 4-FC(6)H(4), 3,5-Me(2)C(6)H(3), and 3,5-Ph(2)C(6)H(3)) and Mo(NMe(2))(4) in toluene at 70 degrees C lead to [(ArNHCH(2)CH(2))(3)N]Mo(NMe(2)) complexes in yields ranging from 64 to 96%. Dimethylamido species (Ar = 4-FC(6)H(4), 3,5-Me(2)C(6)H(3)) could be converted into paramagnetic [(ArNHCH(2)CH(2))(3)N]MoCl species by treating them with 2,6-lutidinium chloride in tetrahydrofuran (THF). The "direct reaction" between 1a-f and MoCl(4)(THF)(2) in THF followed by 3 equiv of MeMgCl yielded [(ArNHCH(2)CH(2))(3)N]MoCl species (3a-f) in high yield. If 4 equiv of LiMe instead of MeMgCl are employed in the direct reaction, then [(ArNHCH(2)CH(2))(3)N]MoMe species are formed. Tungsten species, [(ArNHCH(2)CH(2))(3)N]WCl, could be prepared by analogous "direct" methods. Cyclic voltammetric studies reveal that MoCl complexes become more difficult to reduce as the electron donating ability of the [ArylNCH(2)CH(2))(3)N]3- ligand increases, and the reductions become less reversible, consistent with ready loss of chloride from ([(ArNHCH(2)CH(2))(3)N]MoCl)(-). Tungsten complexes are more difficult to reduce, and reductions are irreversible on the CV time scale.     

C-H activation motivated by N,N'-diisopropylcarbodiimide within a lutetium complex stabilized by an amino-phosphine ligand

A lutetium bis(alkyl) complex stabilized by a flexible amino-phosphine ligand LLu(CH(2)Si(CH(3))(3))(2)(THF) (L = (2,6-C(6)H(3)(CH(3))(2))NCH(C(6)H(5))CH(2)P(C(6)H(5))(2)) was prepared which upon insertion of N,N'-diisopropylcarbodiimide led to C-H activation via metalation of the ligand aryl methyl followed by reduction of the C[double bond, length as m-dash]N double bond.     

Cyclo- and carbophosphazene-supported ligands for the assembly of heterometallic (Cu2+/Ca2+, Cu2+/Dy3+, Cu2+/Tb3+) complexes: synthesis, structure, and magnetism

The carbophosphazene and cyclophosphazene hydrazides, [{NC(N(CH(3))(2))}(2){NP{N(CH(3))NH(2)}(2)}] (1) and [N(3)P(3)(O(2)C(12)H(8))(2){N(CH(3))NH(2)}(2)] were condensed with o-vanillin to afford the multisite coordination ligands [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-OH)(m-OCH(3))}(2)}] (2) and [{N(2)P(2)(O(2)C(12)H(8))(2)}{NP{N(CH(3))N═CH-C (6)H(3)-(o-OH)(m-OCH(3))}(2)}] (3), respectively. These ligands were used for the preparation of heterometallic complexes [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuCa(NO(3))(2)}] (4), [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{Cu(2)Ca(2)(NO(3))(4)}]·4H(2)O (5), [{NC(N(CH(3))(2))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuDy(NO(3))(4)}]·CH(3)COCH(3) (6), [{NP(O(2)C(12)H(8))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuDy(NO(3))(3)}] (7), and [{NP(O(2)C(12)H(8))}(2){NP{N(CH(3))N═CH-C(6)H(3)-(o-O)(m-OCH(3))}(2)}{CuTb(NO(3))(3)}] (8). The molecular structures of these compounds reveals that the ligands 2 and 3 possess dual coordination pockets which are used to specifically bind the transition metal ion and the alkaline earth/lanthanide metal ion; the Cu(2+)/Ca(2+), Cu(2+)/Tb(3+), and Cu(2+)/Dy(3+) pairs in these compounds are brought together by phenoxide and methoxy oxygen atoms. While 4, 6, 7, and 8 are dinuclear complexes, 5 is a tetranuclear complex. Detailed magnetic properties on 6-8 reveal that these compounds show weak couplings between the magnetic centers and magnetic anisotropy. However, the ac susceptibility experiments did not reveal any out of phase signal suggesting that in these compounds slow relaxation of magnetization is absent above 1.8 K.     

Ring openings of lactone and ring contractions of lactide by frustrated Lewis pairs

While B(C(6)F(5))(3) forms the adducts (CH(2))(4)CO(2)B(C(6)F(5))(3)1 and (CHMeCO(2))(2)B(C(6)F(5))(3)7 with δ-valerolactone and lactide, the frustrated Lewis pairs derived from B(C(6)F(5))(3) and phosphine or N-bases react with lactone to effect ring opening affording zwitterionic species of the form L(CH(2))(4)CO(2)B(C(6)F(5))(3) (L = tBu(3)P 2, Cy(3)P 3, C(5)H(3)Me(3)N 4, PhNMe(2) 5, C(5)H(6)Me(4)NH 6) while reaction with rac-lactide results in ring contraction to give salts [LH][OCCHMeCO(2)(CMe)OB(C(6)F(5))(3)] (L = tBu(3)P 8, Cy(3)P 9, C(5)H(3)Me(2)N 10, C(5)H(6)Me(4)NH 11). The mechanistic implications of these reactions are discussed.     

Dehydration reaction of hydroxyl substituted alkenes and alkynes on the Ru(2)S(2) complex

A variety of inter- and intramolecular dehydration was found in the reactions of [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)(mu-S(2))](CF(3)SO(3))(4) (1) with hydroxyl substituted alkenes and alkynes. Treatment of 1 with allyl alcohol gave a C(3)S(2) five-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)CH(2)CH(OCH(2)CH=CH(2))S]](CF(3)SO(3))(4) (2), via C-S bond formation after C-H bond activation and intermolecular dehydration. On the other hand, intramolecular dehydration was observed in the reaction of 1 with 3-buten-1-ol giving a C(4)S(2) six-membered ring complex, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2) [mu-SCH(2)CH=CHCH(2)S]](CF(3)SO(3))(4) (3). Complex 1 reacts with 2-propyn-1-ol or 2-butyn-1-ol to give homocoupling products, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCR=CHCH(OCH(2)C triple bond CR)S]](CF(3)SO(3))(4) (4: R = H, 5: R = CH(3)), via intermolecular dehydration. In the reaction with 2-propyn-1-ol, the intermediate complex having a hydroxyl group, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OH)S]](CF(3)SO(3))(4) (6), was isolated, which further reacted with 2-propyn-1-ol and 2-butyn-1-ol to give 4 and a cross-coupling product, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH=CHCH(OCH(2)C triple bond CCH(3))S]](CF(3)SO(3))(4) (7), respectively. The reaction of 1 with diols, (HO)CHRC triple bond CCHR(OH), gave furyl complexes, [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SSC=CROCR=CH]](CF(3)SO(3))(3) (8: R = H, 9: R = CH(3)) via intramolecular elimination of a H(2)O molecule and a H(+). Even though (HO)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OH) does not have any propargylic C-H bond, it also reacts with 1 to give [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)](2)[mu-SCH(2)C(=CH(2))C(=C=C(CH(3))(2))]S](CF(3)SO(3))(4) (10). In addition, the reaction of 1 with (CH(3)O)(H(3)C)(2)CC triple bond CC(CH(3))(2)(OCH(3)) gives [[Ru(P(OCH(3))(3))(2)(CH(3)CN)(2)][mu-S=C(C(CH(3))(2)OCH(3))C=CC(CH(3))CH(2)S][Ru(P(OCH(3))(3))(2)(CH(3)CN)(3)]](CF(3)SO(3))(4) (11), in which one molecule of CH(3)OH is eliminated, and the S-S bond is cleaved.