Ronald Snaith

Bio: Ronald Snaith is an academic researcher from University of Strathclyde. The author has contributed to research in topics: Lithium & Crystal structure. The author has an hindex of 22, co-authored 94 publications receiving 1665 citations.

.eta.3 and .eta.6 Bridging cations in the N,N,N',N'',N''-pentamethyldiethylenetriamine-solvated complexes of benzylpotassium and benzylrubidium: an x-ray, NMR, and MO study

Abstract: The metalation of toluene (PhCH 3 ) with a 1:1 mixture of n-BuLi/MO t Bu (M=K, Rb) at ambient temperature affords orange-red powders of benzylpotassium or benzylrubidium. On addition of N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDTA) the precipitates dissolve to give burgundy-red solutions, from which needles of [PhCH 2 K.PMDTA.0.5PhCH 3 ] n (1) or [PhCH 2 Rb-PMDTA] n (2) are obtained. X-ray analysis reveals that 1 incorporates half a molecule of toluene per asymmetric unit. In both 1 and 2, the η 3 and η 6 interaction of one M + cation with two benzyl fragments gives rise to the formation of polymeric chains. The coordination sphere of the cations is completed by one chelating triamine ligand

Ladder structures in lithium amide chemistry: syntheses, solid-state, and solution structures of donor-deficient lithium pyrrolidide complexes, [cyclic] {[H2C(CH2)3NLi]3.cntdot.PMDETA}2 and [cyclic] {[H2C(CH2)3NLi]2.cntdot.TMEDA}2, and ab initio MO calculations probing ring vs ladder vs stack structural preferences

Abstract: Describes ladder structures in lithium amide chemistry: syntheses, solid-state, and solution structures of donor-deficient lithium pyrrolidide complexes, [cyclic] {[H2C(CH2)3NLi]3.cntdot.PMDETA}2 and [cyclic] {[H2C(CH2)3NLi]2.cntdot.TMEDA}2, and ab initio MO calculations probing ring vs ladder vs stack structural preferences.

The laddering principle in lithium amide chemistry: the crystal and molecular structure of the pyrrolididolithium adduct [H2C(CH2)3NLi]3·MeN(CH2CH2NMe2)2

Abstract: The title compound, {[H2[graphic omitted]NLi]3·PMDETA}n, (1)(PMDETA = pentamethyldiethylenetriamine), is shown to be the first example of an organonitrogen–lithium laddered structure, consisting in the solid (n= 2) of two attached (NLi)2 rings, or alternatively four (N–Li) rungs, with two terminal NLi units complexes by PMDETA, so preventing further association; cryoscopic and 7Li n.m.r. spectroscopic studies imply that extension of the ladder framework can occur in arene solutions of (1), and these results, together with those from ab initio m.o. calculations on model systems, suggest that similar compounds of type (RR′NLi·xdonor)n, but of various ladder lengths, should be preparable.

Azomethine derivatives. Part 20. Crystal and molecular structures of the lithioketimine [{Li(NCBut2)}6] and lithioguanidine [{Li[NC(NMe2)2]}6]; electron-deficient bridging of Li3 triangles by methyleneamino-nitrogen atoms

Abstract: The lithioketimine Li(NCBut2)(1) and lithioguanidine Li[NC(NMe2)2](2) have remarkably similar hexameric structures [{Li(NCR2)}6](R = But or NMe2) in the crystal phase, based on slightly folded chair-shaped Li6 rings held together by triply-bridging methyleneamino-groups, NCR2, thus providing examples of electron-deficient bridging by the nitrogen atoms of organonitrogen ligands. The mean distance between adjacent metal atoms in the Li6 rings is 2.35(2)A in (1), and 2.445(2)A in (2), and the mean dihedral angles between Li6 chair seats and backs are 85 and 78° respectively. The nitrogen atoms of the bridging methyleneamino-groups are approximately equidistant from the three bridged metal atoms, the mean Li–N distance being 2.06(1)A in (1) and 2.00(1)A in (2). The NC distances of 1.30(1) and 1.244(3)A respectively lie within the range expected for carbon–nitrogen double bonds. Features of these structures are compared with those of related compounds, and some bonding implications are discussed.

Ligand and metal effects on the formation of main-group polyhedral clusters.

Abstract: The reaction of AlMe3 or ZnMe2 with hppH (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) and then with tBuLi affords [Li8(H)m(hpp)6]n+[X] -n, X = [ZntBu3], m = n = 1 (the cation core of which is shown); X = [Li(Me2AltBu2)2, m = 0, n = 2, as the major product in each case. These data reveal that non-aromatic heterocycle hppH and ZnMe2 can be employed to generate novel hydride-encapsulation main-group-metal clusters, and that related polylithium architectures can also incorporate a central void.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

High-symmetry coordination cages via self-assembly.

Abstract: We provide a summary of our results in three-dimensional, coordination-driven self-assembly based on the directional-bonding methodology, in which the stoichiometric mixing of complementary building blocks, with appropriate, predefined geometries, leads to targeted, nanoscopic cages. Using this motif, we have synthesized high-symmetry ensembles resembling the Platonic solids, such as dodecahedra, and the Archimedean solids, such as truncated tetrahedra and cuboctahedra, as well as other cages, like trigonal bipyramids, adamantanoids, and trigonal prisms. The synthesis and characterization of these compounds is discussed, as is some host-guest chemistry.

Strategies for the Construction of Supramolecular Compounds through Coordination Chemistry

Abstract: Synthetic organic chemists enjoy the luxury of having a large collection of reliable reactions at their disposal for preparing small molecules, mesoscopic structures, and polymers. Coordination chemists, on the other hand, are faced with the fact that transition metal chemistry, when normalized for the number of transition metals, has relatively few high-yielding reactions, when compared to the chemistry of carbon, for preparing even small molecule structures. This lack of control is manifested, in large part, in the weak metal-ligand interactions found in coordination complexes as compared with the strong covalent bonds in organic compounds. Weak bonding often translates into many reaction pathways that are not substantially different from an energetic point of view, and therefore, results in poor selectivity. As a result, many coordination chemists in recent years have come to the realization that it may be easier and more productive to develop straightforward and reliable routes to mesoscopic supramolecular structures by capitalizing on the modest collection of high-yielding reactions in coordination chemistry, the directional bonding afforded by metal centers, and strategies aimed at taking advantage of the weak metal bonds found in coordination complexes. Three emerging synthetic strategies, the symmetry-interaction, directional-bonding, and weak-link synthetic approaches, all use metal centers as structural building blocks to rationally assemble molecular components into supramolecular metallocyclophanes. These three approaches are discussed herein, and the fundamental principles underlying each as well as their capabilities are compared and contrasted.