Equivalents Of Me Research Articles

Facile Carbon-Fluorine Bond Activation and Subsequent Functionalisation of 1,1-Difluoroethylene and Tetrafluoroethylene Promoted by Adjacent Metal Centres

The bridging fluoroolefin ligands in the complexes [Ir(2)(CH(3))(CO)(2)(μ-olefin)(dppm)(2)][OTf] (olefin = tetrafluoroethylene, 1,1-difluoroethylene; dppm = μ-Ph(2)PCH(2)PPh(2); OTf(-) = CF(3)SO(3)(-)) are susceptible to facile fluoride ion abstraction. Both fluoroolefin complexes react with trimethylsilyltriflate (Me(3)SiOTf) to give the corresponding fluorovinyl products by abstraction of a single fluoride ion. Although the trifluorovinyl ligand is bound to one metal, the monofluorovinyl group is bridging, bound to one metal through carbon and to the other metal through a dative bond from fluorine. Addition of two equivalents of Me(3)SiOTf to the tetrafluoroethylene-bridged species gives the difluorovinylidene-bridged product [Ir(2)(CH(3))(OTf)(CO)(2)(μ-OTf)(μ-C=CF(2))(dppm)(2)][OTf]. The 1,1-difluoroethylene species is exceedingly reactive, reacting with water to give 2-fluoropropene and [Ir(2)(CO)(2)(μ-OH)(dppm)(2)][OTf] and with carbon monoxide to give [Ir(2)(CO)(3)(μ-κ(1):η(2)-C≡CCH(3))(dppm)(2)][OTf] together with two equivalents of HF. The trifluorovinyl product [Ir(2)(κ(1)-C(2)F(3))(OTf)(CO)(2)(μ-H)(μ-CH(2))(dppm)(2)][OTf], obtained through single C-F bond activation of the tetrafluoroethylene-bridged complex, reacts with H(2) to form trifluoroethylene, allowing the facile replacement of one fluorine in C(2)F(4) with hydrogen.

Complexes of Multifunctional Phosphorus Ligands. Rhenium(V) Complexes of the Multidentate Phenoxyphosphine Ligands Bis(o-trimethylsilyloxyphenyl)phenylphosphine and Tris(o-trimethylsilyloxyphenyl)phosphine. Stepwise Elimination of Me(3)SiX (X = Cl, OEt) from the Metal-Ligand System.

The silylated aryloxo ligands bis(o-silyloxyphenyl)phenylphosphine (abbreviated PhP{OT}(2)) and tris(o-trimethylsilyloxyphenyl)phosphine (abbreviated P{OT}(3), where T = Me(3)Si) were prepared. Complexation reactions with O=ReCl(2)(OEt)(PPh(3))(2) and O=ReCl(3)(PPh(3))(2) proceed by displacement of one PPh(3) and the subsequent stepwise replacement of the OEt and/or Cl substituents. The new complex Re(O)Cl(2)[kappa(2)-(P,O)-(PhP{O}{OT})](PPh(3)), formed by elimination of Me(3)SiOEt, exists in diastereomeric cis and trans forms. Elimination of a second equivalent of Me(3)SiCl gives Re(O)Cl[kappa(3)-(P,O,O)-(PhP{O}(2))](PPh(3)). Similarly P{OT}(3) converts Re(O)Cl(2)(OEt)(PPh(3))(2) to ReOCl(2)[kappa(2)-(P,O)-(P{O}{OT}(2))](PPh(3)) (5) (structurally characterized as 5.0.875CH(2)Cl(2)): crystal data; triclinic P&onemacr;, a = 14.302(4) Å, b = 18.734(2) Å, c = 17.639(4) Å, alpha = 80.950(12) degrees, beta = 80.12(2) degrees, gamma = 81.76(2) degrees, Z = 4. Final R(1) and wR(2) values are 0.0852 and 0.1525, respectively on F(o)(2) > 2sigma(F(o)(2)) data (or 0.1948 and 0.2019 on all data). The phenoxy phosphine ligand in 5 is bound via P and one O to Re. The P atoms are mutually cis to each other and to the terminal oxygen on Re. Two ortho-trimethylsiloxy substituted phenyl rings dangle from the coordinated phosphorus atom. Complex 5 can be converted to Re(O)Cl[kappa(3)-(P,O,O)-(P{O}(2){OT})](PPh(3)) (6) by treatment with PPN(+) Cl(-) and 6 was also obtained by direct reaction of Re(O)Cl(3)(PPh(3))(2) with P{OT}(3) at higher temperatures. The complex 6 has been structurally characterized: crystal data triclinic, P&onemacr;, a = 10.1509(6) Å, b = 12.1123(8) Å, c = 16.2142(14) Å, alpha = 97.851(7) degrees, beta = 94.852(7) degrees, gamma = 96.889(6) degrees, Z = 2. Final R(1) and wR(2) values were 0.0303 and 0.0721 on F(o)(2) > 2sigma(F(o)(2)) data (or 0.0348 and 0.0742 on all data). The phenoxyphosphine ligand in 6 is bound facially to Re through P and two of the phenoxy oxygens. The Ph(3)P group and terminal oxygen atoms are cis to the oxygen atoms of the phenoxy ligands and the Cl lies trans to P. One trimethylsiloxyphenol group dangles. Careful hydrolysis of 6 gave Re(O)Cl[kappa(3)-(P,O,O)-(P{O}(2){OH})](PPh(3)) which was also formed during complexation reactions in moist solvent. Solution (31)P{(1)H} NMR demonstrated cis- or trans-(P,P) geometry for the complexes, which was confirmed in the two aforementioned cases by structure determinations.

Synthesis and crystal structure of an organolanthanide fluoride, [{(Me3Si)2C5H3}2Sm(μ-F)

Treatment of [(Me 3 Si) 2 C 5 H 3 ] 2 SmI(THF) with stoichiometric amounts of AgSbF 6 in dry diethyl ether, or reaction of [(Me 3 Si) 2 C 5 H 3 ] 3 Sm with one equivalent of Me 3 NHF in dry 1,2-dimethoxyethane afforded the dimeric complex [{(Me 3 Si) 2 C 5 H 3 } 2 Sm( μ -F)] 2 in good yield, which represents the first structurally characterized example of a fluoride-bridged organosamarium complex. It crystallizes in space group P 2 1 / n with a = 12.215(1)Å, b = 16.028(1)Å, c = 15.677(1)Å, β = 99.78(1)°, V = 3025(2)Å 3 , and Z = 2 for D calcd = 1.292 g cm −3 . Least squares refinement of the structural model based on 5471 reflections (| F | > 6.0 σ | F |) converged to R F = 0.040. The average Sm(1)—F distance is 2.302(3)Å.

Synthesis and structural characterization of the isomers of Rh 6(CO) 14L 2 clusters (L = NCME, Py, P(OPh) 3), X-ray crystal structure of trans-Rh 6(CO) 14{P(OPh 3)} 2

The reaction of Rh 6(CO) 16 with two equivalents of Me 3 NO in the presence of a substituting ligand (L = NCME, Py, P(OPh) 3) affords a mixture of isomers of the general formula Rh 6(CO) 14L 2. The substituting ligands occupy two terminal sites in the structure of the parent cluster. For L = P(OPh) 3 three isomers ( I-III) were separated from the reaction mixture. The structure of the first isomer (I) has been established by X-ray analysis. This compound crystallizes in two polymorphic modifications, monoclinic and triclinic; both of which consist of identical molecules and differ only in the packing of the molecules in the crystals. It should be noted that both polymorphic forms contain in the unit cells the racemic mixture (RR and SS) of the Rh 6(CO) 14{P(OPh) 3} 2 molecules. This octahedral cluster may be considered as a derivative of the parent Rh 6(CO) 16 cluster with two terminal CO groups in trans positions at Rh(1) and Rh(2) atoms substituted by phosphite ligands. The structures of two other disubstituted clusters, (II) and (III) were established by 31P NMR spectroscopy. Phosphite ligands in these compounds occupy the terminal sites at the adjacent rhodium atoms of the Rh 6 octahedron but differ in their mutual orientation. Other disubstituted derivatives (L = NCME, Py) are labile compounds and exist in solution as inseparable mixtures of the isomers characterized by 1H and 13C NMR spectroscopy. A mechanism of interconversion of the isomers is proposed.

Platinum metal complexes of hexa-aza macrocycles: Synthesis and single crystal X-ray structure of [Pd 2Cl 2(Me 6[18]aneN 6)](PF 6) 2 (Me 6[18]aneN 6  1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane)

Reaction of PdCl 2(NCPh) 2 with 0.5 molar equivalents of Me 6[18]aneN 6 in refluxing MeCN affords initially the binuclear complex [Pd 2Cl 2(Me 6[18]aneN 6)]Cl 2. Addition of H 2O redissolves this orange precipitate giving a clear orange solution from which the complex [Pd 2Cl 2(Me 6[18]aneN 6)](PF 6) 2 can be isolated in high yield following addition of excess aqueous NH 4PF 6. A single crystal structure determination of the complex shows the binuclear cation lying across an inversion centre, with each palladium(II) ion coordinated via an N 3Cl donor set with PdN(1) = 2.113(5), PdN(4) = 2.035(5), PdN(7) = 2.105(5) Å and PdCl = 2.3081 (16) Å. Thus the hexa-aza macrocycle is bound through a meridional arrangement of three N-donors to each metal ion giving an overall distorted square planar stereochemistry. The restricted bite angle of the five-membered chelate rings within the crown leads to bond angle strain and a significant tetrahedral distortion of the N 3Cl donor set away from square planarity. The Pd ⋯ Pd distance of 4.001(1) Å indicates that the palladium(II) ions are non-interacting.

Chemistry and structural studies on the dioxygen-binding copper-1,2-dimethylimidazole system

Studies of copper complexes with the 1,2-dimethylimidazole (Me[sub 2]im) system have provided insights into the factors which control dioxygen (O[sub 2]) binding and activation in imidazole (histidine) ligated copper complexes and proteins. A two-coordinate complex [Cu(Me[sub 2]im)[sub 2]](PF[sub 6]) (1(PF[sub 6])) is formed by the reaction of 1,2-dimethylimidazole with [Cu(CH[sub 3]CN)[sub 4]](PF[sub 6]). Although 1 is unreactive toward O[sub 2] or CO, reaction with one additional molar equivalent of Me[sub 2]im yields a three-coordinate complex [Cu(Me[sub 2]im)[sub 3]](PF[sub 6])(2(PF[sub 6])) which reacts with O[sub 2](Cu/O[sub 2] = 2:1, manometry), producing the EPR silent dioxygen adduct, formulated as [Cu[sub 2](Me[sub 2]im)[sub 6](O[sub 2])][sup 2+] (3). The structure of 1 has been studied by X-ray crystallography; it crystallizes in the monoclinic space group C2/c with Z = 4, a = 14.877 (2) [angstrom], b = 15.950 (4) [angstrom], c = 6.931 (4) [angstrom], and [beta] = 108.54 (2)[degrees]. The linear two-coordinate Cu(I) structure is typical and contains crystallographically equivalent Cu-N(imid) distances of 1.865 [angstrom]. The structures of 2 and 3 have been studied by X-ray absorption spectroscopy, using imidazole group-fitting and full curved-wave multiple scattering analysis. Complex 2 is best fit by a T-shaped structure involving two short (1.89 [angstrom]) and onemore » longer (2.08 [angstrom]) Cu-N(imid) distances. Absorption edge data confirm that the dioxygen complex 3 should be formulated as a Cu(II)-peroxo species. The EXAFS of 3 can be fit by either of two models, A and B. 50 refs., 9 figs., 3 tabs.« less

Rhodium catalyzed transformation of propargylamines to 2-silylmethyl-2-alkenals: Formal silylformylation of allenes

Propargylamines are effectively transformed to 2-dimethylphenylsilylmethyl-2-alkenals by the interaction of two equivalents of Me 2PhSiH under silylformylation conditions catalyzed by Rh 4(CO) 12. The products are not obtained directly by silylformylation of the corresponding allenes.

Rhodium thioether chemistry: the synthesis and electrochemistry of [Rh([18]aneS 6)] 3+ and the ring-opened vinyl thioether complexes [Rh([18]aneS 6-H)] 2+ and [Rh(Me 2[18]aneN 2S 4-H)] 2+ ([18]aneS 6 = 1,4,7,10,13,16-hexathiacyclooctadecane, Me 2[18]aneN 2S 4 = 1,10-dimethyl-1,10-diaza-4,7,13,16-tetrathiacyclooctadecane)

Reaction of [RhCl(C 8H 14) 2] 2 with two molar equivalents of [18]aneS 6 in refluxing MeOH/H 2O with 40% HBF 4 (2 cm 3) for 8 h under nitrogen affords the cream coloured precipitate of [Rh([18]aneS 6)](BF 4) 3. In the absence of acid a bright red solution is generated from which the ring-opened vinyl thioether complex [Rh([18]aneS 6-H)](PF 6) 2 can be isolated upon addition of NH 4PF 6. The analogous ring-opened complex [Rh(Me 2[18]aneN 2S 4- H] 2+ can be prepared by treatment of [RhCl(C 8H 14) 2] 2 with two molar equivalents of Me 2[18]aneN 2S 4 in refluxing MeOH/H 2O under nitrogen for 3 h, followed by addition of a few drops of NEt 3 and further refluxing. [Rh([18]aneS 6)](BF 4) 3 exhibits two chemically reversible one-electron redox couples at E 1/2 = −0.53 and −0.90 V vs Fc/Fc +, assigned as rhodium(III)/(II) and rhodium(II)/(I) couples, respectively. The golden yellow rhodium(II) complex shows a strong, near axial ESR signal with g 1 = 2.012, g 2 = 2.085 and g 3 = 2.099, similar to that observed for [Rh([9]aneS 3) 2] 2+. These reductions have been monitored by in situ electronic spectroscopy using an optically transparent electrode cell, which confirms the chemical reversibility of both processes. [Rh([18]aneS 6-H)] 2+ shows two ill-defined, irreversible reductions at more cathodic potentials. By contrast, [Rh(Me 2[18]aneN 2S 4-H)] 2+ shows two chemically reversible reductions at E 1/2 = −1.11 and −1.56 V vs Fc/Fc +, corresponding to rhodium(III)/(II) and rhodium(II)/(I) couples, respectively. These reduction products are much less stable than for the ring-closed [18]aneS 6 complexes. A weak, axial ESR signal with g ⊥ = 2.147, g ⊥ = 2.012 and A ⊥ = 21 G has been observed corresponding to the first reduction product of [Rh(Me 2[18]aneN 2S 4-H)] 2+.

ChemInform Abstract: Alkylimido Complexes of Titanium(IV).

AbstractAlkylimido complexes of TiCl4 are obtained in simple reactions.

Some dimethyl{tris(trimethylsilyl)methyl} silanolato derivatives of tantalum(V), chromium(III) and manganese(II)

The reaction between tantalum(V) chloride and one equivalent of Me 2{(Me 3Si) 3-C}SiOLi ((trisilox)Li) gave [(trisilox)TaCl 4] ( 2). With two equivalents of (trisilox)Li, the major product was the trisubstituted species [(trisilox) 3TaCl 2] ( 3); 3 was the only complex formed in the reactions employing three or five equivalents of (trisilx)Li. The compounds [(trisilox) 3Cr] ( 4) or [(trisilox) 2Mn · LiCl] ( 5) were obtained by treatment of chromium(III) chloride or manganese(II) chloride with two equivalents of (trisilox)Li, respectively. Preliminary crystallographic results for 4 show a trigonal-planar arrangement of the ligands about the chromium atom.

Stereospecific synthesis of mono‐ and di‐substituted 1‐alkenyl sulfides, phosphines and tin compounds.: A new application of substituted vinylcopper(I) intermediates. Part IV

AbstractA new stereospecific synthesis for substituted 1‐alkenyl sulfides, phosphines and tin compounds RR′C=CHX (X = −SMe, −PPh2, −SnPh3) is presented, starting from stereospecifically generated vinylcuprates [RR′C=CHCu(Br, I or R)]MgX′ (X′ = Cl or Br) and MeSSO2Me, Cl−PPh2 and Cl−SnPPh3, respectively, using tetrahydrofuran as solvent.Iodovinylcuprates [RR′CCHCu−I]MgX′ are obtained by selective methylation of the R‐radical in the mixed homocuprates [RR′CCHCu−R]MgX′ with 1 equivalent of Me−I at −50°.