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Showing papers in "Journal of the American Chemical Society in 1992"


Journal ArticleDOI
TL;DR: In this paper, the synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described.
Abstract: The synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described. MCM-41, one member of this family, exhibits a hexagonal arrangement of uniform mesopores whose dimensions may be engineered in the range of - 15 A to greater than 100 A. Other members of this family, including a material exhibiting cubic symmetry, have ken synthesized. The larger pore M41S materials typically have surface areas above 700 m2/g and hydrocarbon sorption capacities of 0.7 cc/g and greater. A templating mechanism (liquid crystal templating-LCT) in which surfactant liquid crystal structures serve as organic templates is proposed for the formation of these materials. In support of this templating mechanism, it was demonstrated that the structure and pore dimensions of MCM-41 materials are intimately linked to the properties of the surfactant, including surfactant chain length and solution chemistry. The presence of variable pore size MCM-41, cubic material, and other phases indicates that M41S is an extensive family of materials.

10,349 citations


Journal ArticleDOI
TL;DR: In this article, the Universal force field (UFF) is described, where the force field parameters are estimated using general rules based only on the element, its hybridization, and its connectivity.
Abstract: A new molecular mechanics force field, the Universal force field (UFF), is described wherein the force field parameters are estimated using general rules based only on the element, its hybridization, and its connectivity. The force field functional forms, parameters, and generating formulas for the full periodic table are presented

7,953 citations



Journal ArticleDOI
TL;DR: In this article, the authors present an automated solid-phase method for the synthesis of oligo(N-substituted glycines) (NSGs) which is general for a wide variety of side-chain substituents and allows the rapid synthesis of molecules of potential therapeutic interest.
Abstract: Oligomers of N-substituted glycines, or “peptoids“, represent a new class of polymers (Figure 1) that are not found in nature, but are synthetically accessible and have been shown to possess significant biological activity and proteolytic stability.’ We present here an efficient, automated solid-phase method for the synthesis of oligo(N-substituted glycines) (NSGs) which is general for a wide variety of side-chain substituents and allows the rapid synthesis of molecules of potential therapeutic interest. The original method’ for the synthesis of oligomeric NSGs is analogous to standard solid-phase methods for peptide synthesis. Specifically, the carboxylate of Nu-Fmoc-protected (and sidechain-protected) NSGs is activated and then coupled to the secondary amino group of the resin-bound peptoid chain. Removal of the Fmoc group is then followed by addition of the next monomer. Thus, oligomeric NSGs have been treated as condensation homopolymers of N-substituted glycine. A disadvantage of this approach, however, is the necessity of preparing suitable quantities of a diverse set of protected N-substituted glycine monomers. In the method presented here, each N-substituted glycine monomer is assembled from two readily available “submonomers” in the course of extending the NSG polymer (Scheme I). Thus, oligomeric NSGs can also be considered to be alternating condensation copolymers of a haloacetic acid and a primary amine. As in the original method, the direction of polymer synthesis with the submonomers occurs in the carboxy to amino direction. The solid-phase assembly of each monomer, in the course of controlled polymer formation, eliminates the need for N*-protected monomers, as only reactive side-chain functionalities need to be protected. The a-haloacetyl submonomer is common to all cycles of chain extension. Moreover, each RNH2 submonomer is simpler in structure and many are commercially available; thus, oligo(NSG) synthesis is dramatically simplified. The preparation of NSG oligomers by the submonomer method2

1,178 citations


Journal ArticleDOI
TL;DR: A new three-dimensional triple resonance NMR experiment is described that correlates the amide 1 H and 15 N resonances of one residue simultaneously with both the 13 C α and 13 C β resonance of its preceding residue.
Abstract: A new three-dimensional triple resonance NMR experiment is described that correlates the amide 1 H and 15 N resonances of one residue simultaneously with both the 13 C α and 13 C β resonances of its preceding residue. Sensitivity of the new experiment is comparable with that of the HN(CO)CA experiment (Bax, A.; Ikura, M.J. Biomol. NMR 1991, 1, 99-105), but the additional correlation to the C β resonance of the preceding residue provides invaluable assignment information, previously inaccessible

1,033 citations


Journal ArticleDOI
TL;DR: In this paper, the remarkable ability of the imidazole nucleus to stabilize a carbene center at the C-2 position is demonstrated by the isolation of 1,3,4,5-tetramethylimidazol-2-ylidene.
Abstract: Four new stable nucleophilic carbenes have been synthesized and structurally characterized. The remarkable ability of the imidazole nucleus to stabilize a carbene center at the C-2 position is demonstrated by the isolation of 1,3,4,5-tetramethylimidazol-2-ylidene. The isolation of three imidazol-2-ylidenes that bear aryl substituents is counter to speculations based on previous reports

980 citations




Journal ArticleDOI
TL;DR: In this paper, a set of internal coordinates, the natural valence coordinates, is proposed to reduce both harmonic and anharmonic coupling terms in the potential function as much as possible in a purely geometrical definition.
Abstract: Two suggestions are made to increase the efficiency and accuracy of ab initio optimization of molecular geometries. To improve the convergence of the optimization, a set of internal coordinates, the natural valence coordinates, is suggested. These coordinates originate from vibrational spectroscopy and reduce both harmonic and anharmonic coupling terms in the potential function as much as possible in a purely geometrical definition. The natural valence coordinates are local, eliminate most redundancies, and conform to local pseudosymmetry. Special attention has been paid to ring systems. A computer program has been included in our program system TX90 to generate the natural internal coordinates automatically. The usefulness of these coordinates is demonstrated by numerous examples of ab initio geometry optimization. Starting with a geometry preoptimized by molecular mechanics and using a simple diagonal estimate of the Hessian in conjunction with the GDIIS optimization technique, we usually achieved convergence in 8-15 steps, even for large molecules. It is demonstrated that, due to the reduction in anharmonic couplings, natural coordinates are superior to Cartesian or other simple internal coordinates, even when an accurate initial Hessian is available. Constrained optimization and the location of transition states are also discussed. The gradient optimization method has been generalized to handle redundancies; this is necessary in some complex polycyclic molecules and is illustrated on, among others, the porphine molecule. To increase the accuracy of relatively low-level calculations, empirical corrections to ab initio SCF geometries are suggested in the form of “offset forces” acting along bonds. We recommend offset forces for the most important bonds, to be used with the 4-21G(*) and the 6-31G* basis sets. Based on 130 comparisons, the mean absolute error between theoretical and experimental bond lengths is reduced this way from 0.014 to 0.005 A.

880 citations


Journal ArticleDOI
TL;DR: In this paper, an Ru(II) complex with a strained olefin was used to produce a carbene species that polymerizes norbornene in organic media both in the absence and presence of protic/aqueous solvents.
Abstract: During the past two decades, intense research efforts have enabled an in-depth understanding of the olefin metathesis reaction as catalyzed by early transition metal complexes. In contrast, the nature of the intermediates and the reaction mechanism for group VIII transition metal metathesis catalysts remain elusive. Such knowledge is important in view of the promise group VIII metals show in polymerizing a wide variety of functionalized cyclic olefins in protic solvents. Highly active late transition metal catalysts should also open the way to the metathesis of functionalized acyclic olefins. Previous studies in our group have focused on the chemistry of highly active, functional-group-tolerant catalysts prepared from aquoruthenium(II) olefin complexes. In these systems, characterization of the catalytic intermediates is difficult due to their very low concentrations and high activity in the reaction mixtures. Although it is reasonable to assume that the active species are ruthenacyclobutanes and ruthenium carbenes (ruthenaolefins), the oxidation state and ligation of these intermediates are not known. Furthermore, the discrete ruthenium carbene complexes that have been isolated to date do not exhibit both metathesis activity and stability to protic/aqueous solvents. We report here the reaction of an Ru(II) complex with a strained olefin to produce a carbene species that polymerizes norbornene in organic media both in the absence and presence of protic/aqueous solvents. In both solvent systems, a stable propagating carbene complex can be observed throughout the course of the polymerization, as has been previously found with titanium, tantalum, tungsten, molybdenum, and ruthenium complexes.

878 citations



Journal ArticleDOI
TL;DR: The reaction of K 3 [Cr(ox) 3 ].3H 2 O, a metal(II) salt, and tetra(n-butyl)ammonium bromide in the molar ratio of 1:1:1.5 in water at room temperature afforded a series of mixed-metal assemblies with the formula {NBu 4 [MCr(ox), 3 ]} x (M=Mn 2+, Fe 2+, Co 2+
Abstract: The reaction of K 3 [Cr(ox) 3 ].3H 2 O, a metal(II) salt, and tetra(n-butyl)ammonium bromide in the molar ratio of 1:1:1.5 in water at room temperature afforded a series of mixed-metal assemblies with the formula {NBu 4 [MCr(ox) 3 ]} x (M=Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ).


Journal ArticleDOI
TL;DR: In this paper, the van der Waals (vdW) interactions of rare-gas atoms can be used to formulating the representation of vdW nonbonded interactions in molecular mechanics force fields.
Abstract: This paper explores the premise that insights gained from studying the well-characterized van der Waals (vdW) interactions of rare-gas atoms can be used advantageneoulsy in formulating the representation of vdW nonbonded interactions in molecular mechanics force fields, a subject to which little attention has been givin to date

Journal ArticleDOI
TL;DR: In this article, an IR-based van-t Hoff analysis of the intramolecular hydrogen bonding equilibrium occurring in a 1 mM CH2C12 solution of 2 over the temperature range -69 to 23 OC was carried out.
Abstract: diamide’s behavior on the basis of spectroscopic data should be more straightforward than for 1. Previously reported variabletemperature IH NMR measurements (AG(NH)/A.T) indicated that the intramolecularly hydrogen-bonded and non-hydrogenbonded6 states of 2 are of very similar enthalpy in CD2C12.2a In contrast, when an attempt was made to account for solvation by including three CH2C12 molecules in a “supermolecule” calculation, AM1 predicted the minimum energy intramolecularly hydrogen-bonded conformation of 2 to be 1.9 kcal/mol more enthalpically favorable than the minimum energy non-hydrogen-bonded c~nformat ion .~ In order to provide a more quantitative comparison with the calculations, we have now carried out an IR-based van’t Hoff analysis of the intramolecular hydrogen bonding equilibrium occurring in a 1 mM CH2C12 solution of 2 over the temperature range -69 to 23 OC. Figure 1 shows the N-H stretch region of the IR spectra obtained at high and low temperatures. Both hydrogen-bonded (3340-50 cm-l) and non hydrogen-bonded6 (3443-8 cm-I) bands are observed at each temperature. No hydrogen-bonded N-H stretch band can be detected at any temperature for a 1 mM sample of N-methylcyclohexylactamide (3) in CH,Cl,; therefore, we used this compound to estimate the extinction coefficient of the non-hydrogen-bonded N-H stretch band of 2 as a function of temperature. van’t Hoff analysis (intramolecularly hydrogen-bonded vs non-hydrogen-bonded states; each “state” comprises a set of conformations) indicated that the internally hydrogen-bonded state of 2 is 0.25 f 0.06 kcal/mol less enthalpically favorable and 0.67 f 0.48 eu more entropically favorable than the non-hydrogen-bonded state.’ Since CH2C12 is relatively nonpolar, it is interesting that the internally hydrogen-bonded and non-hydrogen-bonded states of 2 have very similar enthalpies, with the state containing the N-H-O=C interaction slightly less enthalpically favorable. An ideal amide-amide hydrogen bond should be enthalpically superior to any interaction between the amide group and the solvent. The enthalpic similarity of the internally hydrogen-bonded and non-hydrogen-bonded states of 2 may result from at least two factors: (1) the geometry of the seven-membered-ring hydrogen bond is not optimal for the amide-amide interaction (e.g., a nonlinear N-H-0 angle is unavoidable); (2) closure of the hydrogen-bonded ring may involve the development of torsional strain and/or other enthalpically unfavorable interactions. The entropic similarity between the internally hydrogen-bonded and non-hydrogen-bonded states may arise from the fact that these two states enjoy similar degrees of conformational mobility2c and/or from desolvation associated with intramolecular hydrogen bond formation.* (The breadth and asymmetry of the hydrogen-bonded N-H stretch band in Figure 1 is consistent with the existence of multiple hydrogen-bonded ring conformations.) Why does AM1 overestimate the enthalpic favorability of the intramolecularly hydrogen-bonded state of 2? One potential source of error is indicated by the comparison between ab initio and AM1 results for the hydrogen-bonded formamide dimer reported by Novoa and Whangboe3 When interaction energy was examined as a function of the N-H--0 angle, the ab initio calculations predicted that the hydrogen bond energy becomes increasingly unfavorable as the angle decreases below 150°.9 For an N-H-0 angle of 120’ (the smallest angle examined), the ab initio interaction energy was 1.5 kcal/mol less favorable than in the

Journal ArticleDOI
TL;DR: In this paper, self-assembled monolayers (SAMs) derived from adsorption of nalkanethiols onto the surfaces of copper slow the oxidation of the copper surface by reaction with atmospheric dioxygen.
Abstract: Self-assembled monolayers (SAMs) derived from adsorption of n-alkanethiols onto the surfaces of copper slow the oxidation of the copper surface by reaction with atmospheric dioxygen. Angstrom-level changes in the thickness of the monolayer result in readily observable differences (by X-ray photoelectron spectroscopy, XPS) in the rates of oxidation of the copper and adsorbed thiolates. The rates of oxidation of the copper and the thiolates can be decreased by ∼50% by increasing the length of the adsorbate, and thus of the SAM, by four CH 2 units

Journal ArticleDOI
TL;DR: In this paper, mixed monolayers can be formed when the electroactive thiols are co-adsorbed with alkanethiols and ω-mercaptoalkanecarboxylic acids.
Abstract: Thiols with pendant redox centers (HS(CH 2 ) n CONHCH 2 pyRu(NH 3 ) 5 2+ , n=10, 11, 15) adsorb from acetonitrile solutions onto gold electrodes to form electroactive monolayers. Mixed monolayers can be formed when the electroactive thiols are co-adsorbed with alkanethiols (HS(CH 2 ) n CH 3 , n=11, 15) and ω-mercaptoalkanecarboxylic acids (HS(CH 2 ) n COOH, n=10, 11, 15); the diluent thiol in each case is slightly shorter than the electroactive thiol

Journal ArticleDOI
TL;DR: In this paper, a method for attaching semiconductor nanocrystals to metal surfaces using self-assembled difunctional organic monolayers as bridge compounds is described, and three different techniques are presented.
Abstract: A method is described for attaching semiconductor nanocrystals to metal surfaces using self-assembled difunctional organic monolayers as bridge compounds. Three different techniques are presented. Two rely on the formation of self-assembled monolayers on gold and aluminum in which the exposed tail groups are thiols. When exposed to heptane solutions of cadmium-rich nanocrystals, these free thiols bind the cadmium and anchor it to the surface. The third technique attaches nanocrystals already coated with carboxylic acids to freshly cleaned aluminum. The nanocrystals, before deposition on the metals, were characterized by ultraviolet-visible spectroscopy, X-ray powder diffraction, resonance Raman scattering, transmission electron microscopy (TEM), and electron diffraction. Afterward, the nanocrystal films were characterized by resonance Raman scattering, Rutherford back scattering (RBS), contact angle measurements, and TEM. All techniques indicate the presence of quantum confined clusters on the metal surfaces with a coverage of approximately 0.5 monolayers. These samples represent the first step toward synthesis of an organized assembly of clusters as well as allow the first application of electron spectroscopies to be completed on this type of cluster. As an example of this, the first X-ray photoelectron spectra of semiconductor nanocrystals are presented. 51 refs., 17 figs.

Journal ArticleDOI
TL;DR: A series of ruthenium(II) complexes have been prepared which contain two phenanthroline ligands and a third bidentate ligand which is one of a set of derivatives of the parent dipyrido[3,2-a:2',3'c]phenazine (DPPZ) ligand.
Abstract: A series of ruthenium(II) complexes have been prepared which contain two phenanthroline ligands and a third bidentate ligand which is one of a set of derivatives of the parent dipyrido[3,2-a:2',3'c]phenazine (DPPZ) ligand. The spectroscopic properties of these complexes in the presence and absence of DNA have also been characterized. The derivatives have been prepared by condensation of different diaminobenzenes or diaminopyridines with the synthetic intermediate bis(1,10-phenanthroline)(1,10-phenanthroline-5,6-dione)ruthenium(II). [Ru(phen)_2DPPz](2+), like [Ru(bpy)_2DPPz]^(2+), acts as a molecular "light switch" for the presence of DNA, displaying no detectable photoluminescence in aqueous solution but luminescing brightly on binding to DNA. None of the DPPZ derivatives prepared show comparable "light switch" enhancements, since some luminescence may be detected in aqueous solution in the absence of DNA. For some complexes, however, luminescence enhancements of a factor of 20-300 are observed on binding to DNA. For these and the parent DPPZ complexes, the large enhancements observed are attributed to a sensitivity of the ruthenium-DPPZ luminescent charge-transfer excited state to quenching by water; although these complexes show little or no luminescence in water, appreciable luminescence is found in acetonitrile. Other derivatives show little solvent sensitivity in luminescence, and these, like Ru(phen)_3^(2+), display moderate enhancements (20-70%) on binding to DNA. [Ru(phen)_2DPPz]^(2+) and its derivatives all show at least biexponential decays in emission. Two binding modes have been proposed to account for these emission characteristics: a perpendicular mode where the DPPZ ligand intercalates from the major groove such that the metal-phenazine axis lies along the DNA dyad axis, and another, side-on mode where the metal-phenazine axis lies along the long axis of the base pairs.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a continuous symmetry measure to quantify the distance of a given (distorted molecular) shape from any chosen element of symmetry, allowing one to compare the symmetry distance of several objects relative to a single symmetry element.
Abstract: We advance the notion that for many realistic issues involving symmetry in chemistry, it is more natural to analyze symmetry properties in terms of a continuous scale rather than in terms of "yes or no". Justification of that approach is dealt with in some detail using examples such as: symmetry distortions due to vibrations; changes in the "allowedness" of electronic transitions due to deviations from an ideal symmetry; continuous changes in environmental symmetry with reference to crystal and ligand field effects; non-ideal symmetry in concerted reactions; symmetry issues of polymers and large random objects. A versatile, simple tool is developed as a continuous symmetry measure. Its main property is the ability to quantify the distance of a given (distorted molecular) shape from any chosen element of symmetry. The generality of this symmetry measure allows one to compare the symmetry distance of several objects relative to a single symmetry element and to compare the symmetry distance of a single object relative to various symmetry elements. The continuous symmetry approach is presented in detail for the case of cyclic molecules, first in a practical way and then with a rigorous mathematical analysis. The versatility of the approah is then further demonstrated with alkane conformations, with a vibrating ABA water-like molecule, and with a three-dimensional analysis of the symmetry of a (2 3 21 reaction in which the double bonds are not ideally aligned.

Journal ArticleDOI
TL;DR: In this article, the synthesis and characterization of μ-η 2 : η 2 peroxo dinuclear copper(II) complexes which to oxyhemocyanin (or oxytyrosinase) in their physicochemical properties are presented.
Abstract: The synthesis and characterization of μ-η 2 :η 2 peroxo dinuclear copper(II) complexes which to oxyhemocyanin (or oxytyrosinase) in their physicochemical properties are presented. The low-temperature reaction of a di-μ-hydroxo copper(II) complex [Cu(HB(3,5-i-Pr 2 pz) 3 )] 2 (OH) 2 (8) with H 2 O 2 gave a μ-peroxo complex [Cu(HB(3,5-i-Pr 2 pz) 3 )] 2 (O 2 ) (6)


Journal ArticleDOI
TL;DR: A potent non-opioid analgesic, epibatidine, has been isolated from skins of the Ecuadoran poison frog, Epipedobates tricolor, and its structure determined by MS, IR, and 1 H NMR analyses as exo-2-(6-chloro-3-pyridyl)-7-azabicyclo[2.2.1]heptane represents a unique new class of alkaloids.
Abstract: A potent non-opioid analgesic, epibatidine, has been isolated from skins of the Ecuadoran poison frog, Epipedobates tricolor, and its structure determined by MS, IR, and 1 H NMR analyses as exo-2-(6-chloro-3-pyridyl)-7-azabicyclo[2.2.1]heptane. It represents a unique new class of alkaloids


Journal ArticleDOI
TL;DR: In this paper, the Universal Force Field (UFF) was used to predict the structures of a variety of organic molecules, including unstrained and uncongested hydrocarbons, silanes, alkenes, saturated amines, saturated ethers and phosphines.
Abstract: The application of a Universal force field (UFF) to the treatment of organic molecules is described. The ability of the force field to predict the structures of a variety of organic molecules is examined, and the results are compared with the MM2 or MM3 force fields. UFF correctly predicts the structures of unstrained and uncongested hydrocarbons, silanes, alkenes, saturated amines, saturated ethers and phosphines, aromatic systems, and simple unconjugated multiple bond containing compounds such as nitriles, ketones, and imines well

Journal ArticleDOI
TL;DR: In this article, the authors reported several carbon-carbon bond-forming reactions catalyzed by rare earth metal alkoxides and their application to a catalytic asymmetric nitroaldol reaction.
Abstract: In a recent paper, the authors reported that Zr(O-t-Bu){sub 4} was an efficient and convenient basic reagent in organic synthesis. However, all reactions examined were performed with stoichiometric quantities of the reagent. The authors envisioned that rare earth metal alkoxides would be stronger bases than group 4 metal alkoxides due to the lower ionization potential (ca. 5.4-6.4 eV) and the lower electronegativity (1.1-1.3) of rare earth elements; thus, the catalytic use of rare earth metal alkoxides in organic synthesis was expected. Although a variety of rare earth metal alkoxides have been prepared for the last three decades, to the authors knowledge, there have been few reports concerning the basicity of rare earth metal alkoxides. Herein, the authors report several carbon-carbon bond-forming reactions catalyzed by rare earth metal alkoxides and their application to a catalytic asymmetric nitroaldol reaction.

Journal ArticleDOI
TL;DR: In this article, the 3-hexylthiophene 2,5-diyl (3-hexylonthiophenes) (HT-PHT) was synthesized with a head-to-tail regioregularity of 91% and an alternative synthesis with almost equal distribution of different linkages in the polymer chain.
Abstract: Recent research on poly(alkylthiophenes) (PAT) has concentrated on the regularity and structure of the polymer chain of PAT. The 3-alkyl substituent in a thiophene ring can be incorporated into a polymer chain with two different regioregularities: head-to-tail (HT) and head-to-head (HH). Head-to-head linkages can cause defects in the polymer chain. The highest regioregularity reported to date for HT-PAT is 91% (usually 50-60% HT regioregularity). The authors report herein a new and facile synthesis which leads to the first completely head-to-tail regioregular poly(3-hexylthiophene 2,5-diyl) (HT-PHT) and an alternative synthesis which yields an unusual regiorandom PHT with almost equal distribution of different linkages in the polymer chain. Both polymers have been characterized by NMR, IR, elemental analysis, GPC (gel-permeation chromatography), and UV-vis. 11 refs., 2 figs., 1 tab.


Journal ArticleDOI
TL;DR: In this paper, high level ab initio molecular orbital studies, using basis sets upto 6-31+G**, with electron correlation included at the second-order MOller Plesset perturbation (MP2) and quadratic configuration interaction with singles and doubles (QCISD) levels, are reported for the tautomeric equilibria of formamide/formamidic acid and 2-pyridone/2-hydroxypyridine in the gas phase and solution.
Abstract: High level ab initio molecular orbital studies, using basis sets upto 6-31+G**, with electron correlation included at the second-order MOller Plesset perturbation (MP2) and quadratic configuration interaction with singles and doubles (QCISD) levels, are reported for the tautomeric equilibria of formamide/formamidic acid and 2-pyridone/2-hydroxypyridine in the gas phase and solution. The solvent effects on the tautomeric equilibria were investigated by self-consistent reaction field (SCRF) theory

Journal ArticleDOI
TL;DR: In this article, an efficient, regiospecific Cp{sup {prime}}{sub 2}LnR (Cp{Sup {prime} = {eta}{sup 5}-Me{sub 5}C{sub 3}H{sub 4]NCHR{sup 1}R{sup 2}CH=CH{sub 1}
Abstract: This contribution reports the efficient, regiospecific Cp{sup {prime}}{sub 2}LnR (Cp{sup {prime}} = {eta}{sup 5}-Me{sub 5}C{sub 5};R = H, CH(TMS){sub 2}, {eta}{sup 3}-C{sub 3}H{sub 5}, N(TMS){sub 2}; Ln-La,Nd,Sm,Y,Lu)-catalyzed hydroamination/cyclization of the amino olefins H{sub 2}NCHR{sup 1}R{sup 2}CH=CH{sub 2} to yield heterocycles. Kinetic isotope effects are observed for some of the cyclizations. The complexes were synthesized to model species in the catalytic cycle. Two independent molecules crystallize per unit cell with average La-NHCH{sub 3} and La{le}NH{sub 2}CH{sub 3} bond distances of 2.31 (1) and 2.70 (1) {Angstrom}, respectively. The amine-amido complexes undergo rapid intramolecular proton transfer between some of the amine and amido ligands. Intermolecular exchange with free amine is rapid on the NMR time scale at -80 {degrees}C. The ordering of precatalyst activities accords with known olefin insertion reactivities. Diastereoselection in H{sub 2}NCH(CH{sub 3})(CH{sub 2}){sub 2}CH=CH{sub 2}(5) cyclization depends on both lanthanide and ancillary ligation. Mechanistic evidence suggests that olefin insertion into the Ln-N bond of the amine-amido complexes is turnover-limiting and is followed by a rapid protonolysis of the resulting Ln-C bond. The proposed catalytic mechanism invokes parallel manifolds, with one manifold populated at high amine concentrations exhibiting high diastereoselectivity in the cyclization of 5, and with the second, favoredmore » at low substrate concentrations, exhibiting lower diastereoselectivity. The catalyst at high amine concentrations is postulated to be a Ln(amido)(amine){sub 2} complex. 93 refs., 15 figs., 8 tabs.« less