65496-72-2Relevant academic research and scientific papers
Activation barriers to meso-aryl group rotation in titanyl tetraaryltetrapyrroles. An investigation of the out-of-plane flexibility of hydroporphyrins
Stolzenberg, Alan M.,Haymond, G. Scott
, p. 300 - 308 (2002)
The free-base and titanyl (TiIVO) complexes of meso-tetratolyl- and meso-tetra(3,5-xylyl)hydroporphyrins were synthesized and characterized. Metalation of the hydroporphyrins with titanium was achieved by reaction of the lithium salts of the hydroporphyrin with TiCl4. Other methods used to metalate porphyrins with titanium required harsher reaction conditions and led to substantial oxidative dehydrogenation of the macrocycle when applied to hydroporphyrins. The titanyl group differentiates the two faces of the macrocycle and consequently the two sides of the meso-aryl groups, which are tilted nearly perpendicular to the macrocycle plane. The 1H NMR signals for the nonequivalent ortho protons and nonequivalent meta protons averaged on the NMR time scale at elevated temperatures due to aryl group rotation. Activation barriers for aryl group rotation in the para-substituted and meta-disubstituted titanyl hydroporphyrin complexes and in related titanyl porphyrin complexes were determined from variable-temperature NMR spectra and ranged from 15.6 to 18.4 kcal/mol. In chlorin compounds, barriers for rotation of aryl groups located between a pyrrole and a pyrroline (reduced) ring are greater than those of aryl groups located between two pyrrole rings. Comparisons of barriers in complexes with different macrocycle saturation levels show that the increased barriers for aryl groups adjacent to pyrroline rings cannot be attributed solely to the increased steric bulk of the pyrroline β-CH2 group relative to the pyrrole β-CH group. Variations in flexibility and electronic environments at meso carbons in the hydroporphyrins may also contribute. Rotation barriers for metadisubstituted aryl groups, which are higher than those for para-substituted aryl groups, increase with the size and mass of the substituent.
Synthesis, characterization, and reactivity of group 4 metalloporphyrin diolate complexes
Du, Guodong,Woo, L. Keith
, p. 450 - 455 (2008/10/08)
A number of group 4 metalloporphyrin diolate complexes were synthesized via various approaches. For example, treatment of imido complex (TTP)Hf=NAriPr with diols resulted in information of the corresponding diolato complexes (TTP)Hf[OCR1R2CR1R2O] (R1 = R2 = Me, 1; R1 = Me, R2 = Ph, 2; R1 = R2 = Ph, 3). Treatment of (TTP)Ti=NiPr with diols generated (TTP)Ti[OCR1R2CR1R2O] (R1 = R2 = Me, 5; R1 = Me, R2 = Ph, 6; R1 = H, R2 = Ph, 7; R1 = H, R2 = p-tolyl, 8). Alternatively hafnium and titanium pinacolates 1 and 5 were prepared through metathetical reactions of (TTP)MCl2 (M = Hf, Ti) with disodium pinacolate. The substitution chemistry of hafnium complexes correlated well with the basicity of the diolato ligands. Complexes 1-6 underwent oxidative cleavage reaction, producing carbonyl compounds and oxometalloporphyrin species. For less substituted diolates 7 and 8, an array of products including the enediolate complexes (TTP)Ti[OC(Ar)C(Ar)O] (Ar = Ph, 9; Ar = p-tolyl, 10) was observed. The possible cleavage reaction pathways are discussed.
Atom transfer reactions of (TTP)Ti(n2-3-hexyne): Synthesis and molecular structure of trans-(TTP)Ti[OP(Oct)3]2
Thorman,Young Jr.,Boyd,Guzei,Woo
, p. 499 - 506 (2008/10/08)
Atom and group transfer reactions were found to occur between heterocumulenes and (TTP)Ti(n2-3-hexyne), 1 (TTP = meso-5,10,15,20-tetra-p-toly]porphyrinato dianion). The imido derivatives (TTP)Ti=NR (R = ′Pr, 2; ′Bu, 3) were produced upon treatment of complex 1 with ′PrN=C=N′Pr, ′PrNCO, or ′BuNCO. Reactions between complex 1 and CS2, ′BuNCS, or ′BuNCSe afforded the chalcogenido complexes, (TTP)Ti=Ch (Ch = Se, 4; S, 5). Treatment of complex 1 with 2 equiv of PEt3 yielded the bis(phosphine) complex, (TTP)Ti(PEt3)2, 6. Although (TTP)Ti(n2-3-hexyne) readily abstracts oxygen from epoxides and sulfoxides, the reaction between 1 and O=P(Oct)3 did not result in oxygen atom transfer. Instead, the paramagnetic titanium(II) derivative (TTP)-Ti[O=P(Oct)3]2, 7, was formed. The molecular structure of complex 7 was determined by single-crystal X-ray diffraction: Ti-O distance 2.080(2) A and Ti-O-P angle of 138.43(10)°. Estimates of Ti=O, Ti=S, Ti=Se, and Ti=NR bond strengths are discussed.
Synthesis and reactivity of hydrazido(2-) and imido derivatives of titanium(IV) tetratolylporphyrin
Thorman, Joseph L.,Keith Woo
, p. 1301 - 1304 (2008/10/08)
Titanium porphyrin hydrazido complexes (TTP)Ti = NNR2 (TTP = meso-tetra-p-tolylporphyrinato dianion; R = Me (1), Ph (2)) were synthesized by treatment of (TTP)TiCl2 with 1,1-disubstituted hydrazines H2NNR2 (R =
Halogenated oxo- and peroxotitanium porphyrinates as sensitizers for the photooxygenation of olefinic compounds
Esser, Peter E.,Driessen-Hoelscher, Birgit,Keim, Wilhelm
, p. 13 - 24 (2008/10/09)
A series of porphines, oxotitanium(IV) and peroxotitanium(IV) porphyrinates were tested as photosensitizers of the singlet oxygen ene reaction with cyclohexene and cis-cyclooctene. The relative order of activity is: H2(P) ≥ O=Ti(P) ≥ Ti(O2)P. Best stability is obtained for porphines or porphyrinate complexes with fluorine substituents. Oxotitanium(IV) porphyrinates are active in the decomposition of allylic hydroperoxides. The (photo)catalytic epoxidation occurs less readily than the thermal reaction at 82°C. Attempts of photocatalytic hydrogen peroxide activations lead to fast destruction of O=Ti(P).
Synthesis, Electrochemistry, and Imido Transfer Reactions of (TTP)Ti(η(2)-PhN=NPh)
Gray, Steven D.,Thorman, Joseph L.,Adamian, Victor A.,Kadish, Karl M.,Woo, L. Keith
, p. 1 - 4 (2008/10/08)
Treatment of (TTP)Ti(η(2)-RC.tplbond.CR) (R = Et or Ph) with PhN=NPhresults in formation of the azobenzene adduct (TTP)Ti(η(2)-PhN=NPh) (1) in good isolated yield. Complex 1 reacts with (TTP)Ti(η(2)-RC.t plbond.CR) at elevated temperatures to cleanly affo
Facile Syntheses of Titanium(II), Tin(II), and Vanadium(II) Porphyrin Complexes through Homogeneous Reduction. Reactivity of trans-(TTP)TiL2 (L = THF, t-BuNC)
Wang, Xiaotai,Gray, Steve D.,Chen, Jinyuan,Woo, L. Keith
, p. 5 - 9 (2008/10/08)
Facile syntheses of the meso-tetra-p-tolylporphyrin (TTP) complexes trans-(TTP)Ti(THF)2 (1), (TTP)Sn (2), and trans-(TTP)V(THF)2 (3) are achieved through homogeneous reduction of high-valent precursors using NaBEt3H. The composition of the new compound trans-(TTP)Ti(THF)2 was determined by spectroscopic and chemical characterization. Ligand displacement reactions of trans-(TTP)Ti(THF)2 with t-BuNC produced a new Ti(II) complex, trans-(TTP)Ti(t-BuNC)2. The ligand-binding preference of (TTP)TiIILn (n = 1, 2) is picoline ～pyridine > t-BuNC > PhC≡CPh > EtC≡CEt > THF.
Alkoxido, Amido, and Imido Derivatives of Titanium(IV) Tetratolylporphyrin
Gray, Steven D.,Thorman, Joseph L.,Berreau, Lisa M.,Woo, L. Keith
, p. 278 - 283 (2008/10/09)
Treatment of (TTP)TiCl2 (1) [TTP = meso-5,10,15,20-tetra-p-tolylporphyrinato dianion] with excess NaOR (R = Ph, Me, t-Bu) affords the bis(alkoxide) derivatives (TTP)Ti(OR)2 [R = Ph (2), Me (3), t-Bu (4)] in moderate yield. The corresponding amido derivative (TTP)Ti(NPh2)2 (5) is prepared in an analogous fashion employing LiNPh2. The disubstituted complexes 2, 3, and 5 react cleanly with (TTP)TiCl2 to afford the ligand exchange products (TTP)Ti(OR)Cl [R = Ph (6), Me (7)] and (TTP)Ti(NPh2)Cl (8). respectively. The monosubstituted complexes 6-8 are also obtained by treatment of 1 with 1 equiv of the appropriate NaOR or LiNPh2 reagent. Treatment of 5 with excess phenol produces the bis(phenoxide) derivative 2 and 2 equiv of HNPh2. The imido derivatives (TTP)Ti=NR [R = t-Bu (9), Ph (10), C6H4-p-Me (11)] are prepared by the treatment of 1 with excess LiNHR. The t-Bu derivative (9) is also obtained by reaction of 1 with excess H2N-t-Bu at elevated temperatures. The phenyl imido complex (10) may be produced by the reaction of 0.5 equiv of PhN=NPh with (TTP)Ti(η2-EtC≡CEt) in refluxing toluene. Finally, (TTP)Ti=NTMS (12) is obtained by oxidation of (TTP)Ti(η2-EtC=CEt) with N3TMS.
Synthesis, characterization, substitution, and atom-transfer reactions of (n2-alkyne)(tetratolylporphyrinato)titanium(II). X-ray structure of trans-bis(4-picoline)(tetratolylporphyrinato)titanium(II)
Woo, L. Keith,Hays, J. Alan,Young Jr., Victor G.,Day, Catherine L.,Caron, Cecile,D'Souza, Francis,Kadish, Karl M.
, p. 4186 - 4192 (2008/10/08)
A general preparative method for (tetratolylporphyrinato)titanium(II) η2-acetylene complexes, (TTP)Ti(η2-RC≡CR′), (R = R′ = CH3, CH2CH3, C6H5; R = CH3, R′ = CH2CH3) is described. Displacement of 2-butyne from (TTP)Ti(η2-MeG≡CMe) with terminal acetylenes allows the preparation of (TTP)Ti(η2-HC≡CH) and (TTP)Ti(η2-PnC≡CH). The π complexes undergo simple substitution reactions with pyridine (py) and 4-picoline (pic) to afford the bis(ligand) complexes trans-(TTP)Ti(py)2 and trans-(TTP)Ti(pic)2. The structure of the bis(picoline) complex, C66H56N4Ti, was determined by single-crystal X-ray diffraction (triclinic, P1, a = 9.764(2) A?, b = 10.899(2) A?, c = 13.530(2) A?, α = 92.18(2)?, β = 98.10(2)°, γ = 114.14(2)°, V = 1293.6(4) A?3, Z = 1, R = 5.2%, and Rw 5.4%). Crystallographic symmetry requires that the Ti atom resides in the center of the 24 atom porphyrin plane. The Ti-Npic distance is 2.223(3) A?, and the average Ti-Npyrrole distance is 2.047(8) A?. The two picoline ligands are coplanar, and the dihedral angle formed by the plane of the picoline rings and the Ti-N1 vector is 43°. When (η2-PhC≡CPh)Ti(TTP) is treated with di-p-tolyldiazomethane, a diazo adduct (TTP)Ti=NN=C(C6H4CH3)2 is formed. Atom transfer occurs when (η2-PhC≡CPh)Ti(TTP) is treated with X=PPh3 (X = S, Se), resulting in a two-electron oxidized product, (TTP)Ti=X, PPh3, and free PhC≡CPh. Treatment of (TTP)Ti(η2-PhC≡CPh) with elemental sulfur or selenium produces the perchalcogenido complexes (TTP)Ti(S2) and (TTP)Ti(Se2). The chalcogenide ligand complexes (TTP)Ti=S and (TTP)Ti=Se were also electrochemically characterized for comparison with related derivatives of (P)Ti(S2) and (P)Ti(Se2). Each compound undergoes two reversible one-electron reductions which are located at E1/2 = -1.07 ± 0.01 and 1.47 ± 0.01 V in CH2Cl2 containing 0.1 M tetra-n-butylammonium perchlorate. They also undergo two oxidations, the first of which is irreversible, consistent with an electrode reaction involving the axial ligand rather than the porphyrin macrocycle. A comparison of potentials for oxidation of (TTP)Ti=X and (TPP)Ti (η2-X2) indicates a stronger titanium-chalcogen bond in the case of the terminal selenide and sulfide derivatives as compared to the metal-chalcogen bond in the η2-X2 complexes.
