Molecular mechanics calculations of tin-bis (triphenylphosphine oxide) complexes

The capability of molecular mechanics for modeling the wide distribution of bond angles and bond lengths characteristic of coordination complexes was investigatecl. This was the preliminary step for future modeling of solvent extraction. Several tin-phosphine oxide COrnI)le:){es were selected as the test groUl) for t.he d,esired range of geometry they eX!libi ted as \-vell as the ligands they cOD.tained r Wllich were c\f interest in connection with solvation. A variety of adjustments were made to Allinger's M:M2 force·-field ill order to inl.prove its performance in the treatment of these systems. A set of u,nique force constants was introduced for' those terms representing the metal ligand bond lengths, bond angles, and, torsion angles. These were significantly smaller than trad.itionallY used. with organic compounds. The ~1orse poteIlt.ial energ'Y function was incorporated for the M-X l')ond lE~ngths and the cosine harmonic potential erlerg-y function was invoked for the MOP bond angle. These functions were found to accomodate the wide distribution of observed values better than the traditional harmonic approximations~ Crystal packing influences on the MOP angle were explored thr"ollgh ttle inclusion of the isolated molecule withil1 a shell cc)ntaini11g tl1e nearest neigl1'bors duri.rlg energy rninimization experiments~ This was found to further improve the fit of the MOP angle.

The crystal and molecular structure of bis (pyridoxamine) copper (II) dinitrate monohydrate

The crystal structure of Cu(PM)2(N03hoH20 (where PM is pyridoxamine, CSHI2N202) has been determined from three dimensional x-ray diffraction data. The crystals are triclinic, space group pI, a = 14.248 (2), b = 8.568 (1), c = 9.319 (1) 1, a = 94.08 (1), e = 89.73 (1), y~~ 99.18 (1)°, z = 2, jl(MoK) = 10.90 em-I, Po = 1.61 g/cm3 and Pc = 1.61 g/em3• The structure a was solved by Patterson techniques from data collected on a Picker 4-circle diffractometer to 26max = 45°. All atoms, including hydrogens, have been located. Anisotropic thermal parameters have been refined for all nonhydrogen atoms. For the 2390 independent reflections with F ? 3cr(F) , R = 0.0408. The results presented here provide the first detailed structural information of a metal complex with PM itself. The copper atoms are located on centres of symmetry and each is chela ted by two PM zwitterions through the amino groups and phenolate oxygen atoms. The zwitterionic form found in this structure involves the loss of a proton from the phenolate group and protonation of the pyridine ring nitrogen atoms. The two independent Cu(PM)2 moieties are symmetrically bridged by a single oxygen atom from one of the nitrate groups. The second nitrate group is not coordinated to the copper atoms but is central to an extensive hydrogen bonding network involving the water molecule and uncoordinated functional groups of PM.

The kinetics and mechanism of the thermal decomposition of bis diphenyl methyl and related peroxides in liquid phase /|nby C. Thankachan. -- 260 St. Catharines, Ont. : [s. n.],

Rates and products have been determined for the thermal decomposition of bis diphenyl methyl peroxide and diphenyl methyl tert* butyl peroxide at 110@~145@C* The decomposition was uniformly unimolecular with activation energies for the bis diphenyl methyl peroxide in tetrachloroethylene* toluene and nitrobenzene 26,6* 28*3f and 27 Kcals/mole respectively. Diphenyl methyl tert* butyl peroxide showed an activation energy of 38*6 Kcals/mole* About 80-90% of the products in the case of diphenyl methyl peroxide could be explained by the concerted process, this coupled with the negative entropies of activation obtained is a conclusive evidence for the reaction adopting a major concerted path* All the products in the case of diphenyl methyl peroxide could be explained by known reactions of alkoxy radicals* About 80-85% of tert butanol and benzophenone formed suggested far greater cage disproportionation than diffusing apart* Rates of bis triphenyl methyl peroxide have been determined in tetrachloroethylene at 100-120@C* The activation energy was found to be 31 Kcals/mole*

The nucleophillic substitution of various chloroanthraquinones of their possible rearrangement via aryne intermediates

The work in this thesis deals mainly with nucleophilic substitution of chloroanthraquinones as a route to various starting materials which might rearrange, via aryne intermediates to afford fused-ring heterocy1ic carboxylic acids. 1-Amino-5-chloroanthraquinone was successfully prepared by reacting 1,5-dichloroanthraquinone with sodium aZide in ref1uxing dimethylsulfoxide (DMSO). It could also be prepared from the same starting material by reaction with ammonia (gas) in DMSO in the presence of potassium fluoride. Treatment of l-amino-5-chloroanthraquinone with potassium amide in liquid ammonia or with potassium t-butoxide in t-butylbenzene returned mainly starting material, although in the latter case some 1-amino-5-hydroxyanthraquinone was also isolated. 1-Hydroxy-5-chloroanthraquinone was ultimately prepared by diazotization of the amino-analog. It was recovered almost quantitatively after treatmenu'with potassium amide in liquid ammonia. The reaction with potassium t-butoxide in t-buty1benzene was anomalous and gave 1-hydroxyanthraquinone as the only iso1able product. Acridines were successfully prepared by the action of 70% sulfuric acid on 1,5-bis(p-toluidino)-anthraquinone and 1-p-toluidino-5- ch10roanthraquinone, and in the latter case, cleavage to give an acridinecarboxylate was attempted. Substituted anthraquinones reacted with sodium azide in sulfuric acid to give azepindiones by -NH insertion. Methods for separating and identifying isomeric mixtures of these compounds were examined. Attempted decarbonylation of selected azepindiones to give acridones gave mainly what were thought to be amino-benzophenone derivatives. Chloroanthraquinones were found to react with hexamethylphosphoramide (HMPA) to give mixtures of the dimethylamino- and methylaminoderivatives. Under the same conditions halogeno-nitrobenzenes and nitrophenols were substituted to give the appropriate dimethyl aminobenzenes, except in two cases. 3-Chloronitrobenzene reacted anomalously to give a small amount of 3,3'-dichloroazobenzene and a trace of 4-dimethylamino-nitrobenzene. Pentachlorophenol reacted to give a pentachlorophenylphosphorodiamidate in good yield.

Bis-and tris (amidine) fluoroboron cations and related systems studies by Multinuclear NMR and fast atom bombardment mass spectometry

The formation and the isolation of fluoroboron salts, (D2BF2+)(PF6-), (DD'BF2+)(PF6-) and (D3BF2+)(PF6-)2, have been carried out. 1,8-Diazabicyclo [5,4.0]undec-7-ene (DBU) and 1,5-diazabicyclo[4,3,O]non-5-ene (DBN), extremely strong organic bases, were introduced into the fluoroboron cation systems and induced a complicated redistribution reaction in the D/BF3/BC13 systems. The result was the formation of all BFnCI4-n-, D.BFnCI3-n and fluoroboron cation species which were detected by 19p and 11B NMR spectrometry. The displacement reaction of CI- from these D.BFnCI3-n (n = 1 and 2) species by the second entering ligand is much faster than in other nitrogen donor containing systems which have been previously studied. Tetramethylguanidine, oxazolines and thiazolines can also produce similar reactions in D/BF3/BCI3 systems, but no significant BFnC4-n- species were observed. As well as influences of their basicity and their steric hindrance, N=C-R(X) (X = N, 0 or S) and N=C( X)2 (X = N or S) structures of ligands have significant effects on the fonnationof fluoroboron cations and the related NMR parameters. D3BF2+ and some D2BF2+ show the expected inertness, but (DBU)2BF2+ shows an interestingly high reactivity. (D2BF2+)(X-) formed from weak organic bases such as pyridine can react with stronger organic bases and form DD'BF2+ and D'2BF2+ in acetone or nitromethane. Fast atom bombardment mass spectrometry is doubly meaningful to this work. Firstly, FABMS can be directly applied to the complicated fluoroboron cation containing solution systems as an excellent complementary technique to multinuclear NMR. Secondly, the gas-phase ion substitution reaction of (D2BF2+)(PF6-) with the strong organic bases is successfully observed in a FABMS ion source when the B-N bond is not too strong in these cations.

Nuclear magnetic resonance studies of boron trihalide complexes of 1,1-BIS (dimethylamino) ethylene and related bases

Boron tribalide complexes of 1,1-bis(dimethylamino)ethylene (DME) , t etramethylurea (TMU), tetramethylguanidine (TMG) , and pentamethylguanidine (PMG) and also mixed boron t r ihalide adducts of DME have been investigated by 1H and 19F NMR spectroscopy. Both nitrogen and the C-Q-H carbon of DME are possible donor a toms to boron trihal ides but complexation has been found to occur only at carbon of DME. The initial adduct acts as a Bronsted acid and gives up a proton to free DME in solut ion. A side reaction in the DME-BF, system gives rise to trace amounts of a complex aSSigned as (DME)2BF2+. (DME)2BF2+ is produced in much larger quantities in t he DME-BF3-BC13 and DME-BF,-BBr, systems by reaction of free DME with DME:BF2X (X = Cl, Br). Restricted r otation about the C-N bonds of TMUlBC13 and n1U:BBr3 has been observed at low temperatures. This complements previous work in this system and confirms oxygen donation of TMU to boron trihalides . Restricted rotation at low temperatures also has been observed in DMEboron trihalide systems

Synthesis, Catalysis and Stoichiometric Reactivity of Mo Imido Complexes

The syntheses, catalytic reactivity and mechanistic investigations of novel Mo(IV) and Mo(VI) imido systems is presented. Attempts at preparing mixed bis(imido) Mo(IV) complexes of the type (RN)(R′N)Mo(PMe3)n (n = 2 or 3) derived from the mono(imido) complexes (RN)Mo(PMe3)3(X)2 (R = tBu (1) or Ar (2); X = Cl2 or HCl, Ar=2,6-iPr2C6H3) are also described. The addition of lithiated silylamides to 1 or 2 results in the unexpected formation of the C-H activated cyclometallated complexes (RN)Mo(PMe3)2(η2-CH2PMe2)(X) (R = Ar, X = H (3); R = tBu, X = Cl (4)). Complexes 3 and 4 were used in the activation of R′E-H bonds (E = Si, B, C, O, P; R′ = alkyl or aryl), which typically give products of addition across the M-C bond of the type (RN)Mo(PMe3)3(ER′)(X) (4). In the case of 2,6-dimethylphenol, subsequent heating of 4 (R = Ar, R′ = 2,6-Me2C6H3, E = O) to 50 °C results in C-H activation to give the cyclometallated complex (ArN)Mo(PMe3)3(κ2-O,C-OPh(Me)CH2) (5). An alternative approach was developed in synthesizing the mixed imido complex (ArN)(tBuN)Mo(PMe3)(η2-C2H4) (6) through EtMgBr reduction of (ArN)(tBuN)MoCl2(DME) in the presence of PMe3. Complex 6 reacts with various hydro- and chlorosilanes to give β-agostic silylamido complexes and in one case, when Me2SiHCl is the silane, leads to the silanimine complex (tBuN)Mo(η2-SiMe2-NAr)(Et)(η2-C2H4) (7). Mechanistic studies on the formation of the Mo(VI) tris(silyl) complex (tBuN)Mo(SiHPh)(H){(μ-NtBu)(SiHPh)}(PMe3)2 (8) were done from the addition of three equivalents of PhSiH3 to (tBuN)Mo(PMe3)(η2-C2H4), resulting in identification of β- and γ-agostic SiH…Mo intermediates. The reactivity of complex 8 towards ethylene and nitriles was studied. In both cases coupling of unsaturated substrates with the Mo-Si bond of the metalacycle was observed. In the case of nitriles, insertion into the 4-membered disilaazamolybdacycle results in complexes of the type (tBuN)Mo{(κ2-Si,C-SiHPh-NtBu-SiHPh-N=C(R)}(PMe3)2. Catalytic hydrosilylation of carbonyls mediated by the β-agostic silylamido complex (ArN)2Mo(η3-NtBu-SiMe2-H)(H) (9) was investigated. Stoichiometric reactions with organic substrates showed that catalysis with 9 does not proceed via the conventional insertion of substrate into the Mo-H bond.

Estudio del (2-(Bis-(N-acetilsulfanililimino) -4 Tiazolina

Tesis (Maestría en Ciencias con Especialidad en Química Orgánica) UANL

La asistencia legal al testigo y su situación procesal en la averiguación previa (Análisis del artículo 127 Bis del Código Federal de Procedimientos Penales)

Tesis ( Maestría en Ciencias Penales) U.A.N.L.

La inconstitucionalidad del artículo 21 Bis-8 de la Ley de Hacienda para los Municipios del Estado de Nuevo León

Tesis (Maestría en Derecho Fiscal ) U.A.N.L.