“…This results in the highest reactivity, the metal charge being almost the same along the R n Cl 3 - n Si • series (Table ). Then, the electronic structure of the intermediate radical can influence its addition to the substrate (b, Scheme ), and also the abstraction of hydrogen (c, Scheme ). , 1 1 Spin localization density in R n Cl 3 - n Si • (Hyperchem PM3 calculations).…”
Hydrometalation of carbon−carbon double bonds by group 14 hydrides is inhibited by
carbonyl compoundsmainly by α,β-unsaturated carbonyl groupsas efficiently as by
classical radical trapping compounds, such as galvinoxyl and hydroquinone. This phenomenon, in the case of polyfunctional CC- and CO-containing compounds, such as carvone,
leads to an autoinhibition of the exocyclic alkenylic hydrometalation under normal reaction
conditions, while under drastic conditions, the O-metalation of the α,β-unsaturated carbonyl
group occurs.
“…This results in the highest reactivity, the metal charge being almost the same along the R n Cl 3 - n Si • series (Table ). Then, the electronic structure of the intermediate radical can influence its addition to the substrate (b, Scheme ), and also the abstraction of hydrogen (c, Scheme ). , 1 1 Spin localization density in R n Cl 3 - n Si • (Hyperchem PM3 calculations).…”
Hydrometalation of carbon−carbon double bonds by group 14 hydrides is inhibited by
carbonyl compoundsmainly by α,β-unsaturated carbonyl groupsas efficiently as by
classical radical trapping compounds, such as galvinoxyl and hydroquinone. This phenomenon, in the case of polyfunctional CC- and CO-containing compounds, such as carvone,
leads to an autoinhibition of the exocyclic alkenylic hydrometalation under normal reaction
conditions, while under drastic conditions, the O-metalation of the α,β-unsaturated carbonyl
group occurs.
“…Their VB estimates for barriers and reaction energies deviated by as much as 7 kcal mol -1 from those computed using MP2. Drozdova et al studied hydrogen abstraction from Ge- and Sn-containing species by radicals. Chatgilialoglu et al investigated the reaction of germanium hydrides to determine their hydrogen donation abilities.…”
A series of reactions of the type Y‚ + XH 4 f YH + ‚XH 3 and Y′‚ + HX(CH 3 ) 3 f Y′H + ‚X(CH 3 ) 3 , where Y ) H, CH 3 ; Y′ ) CH 3 , C(CH 3 ) 3 ; and X ) Si, Ge, Sn, Pb are studied using state-of-the-art ab initio electronic structure methods. Second-order Møller-Plesset perturbation theory; the coupled-cluster singles, doubles, and perturbative triples method; and density functional theory are used with correlation-consistent basis sets (cc-pVNZ, where N ) D, T, Q) and their pseudopotential analogs (cc-pVNZ-PP) to determine the transitionstate geometries, activation barriers, and thermodynamic properties of these reactions. Trends in the barrier heights as a function of the group IVA atom (Si, Ge, Sn, and Pb) are examined. With respect to kinetics and thermodynamics, the use of a hydrogen attached to a group IVA element as a possible hydrogen donation tool in the mechanosynthesis of diamondoids appears feasible.
“…The HDon tool is readily covalently bonded to a larger handle structure by extension of a regular diamond lattice of which the adamantane base is a unit cage. The radical chemistry of H donation has been studied [71][72][73][74][75][76] and hydrogen donation tools for DMS have been described qualitatively, 3 Step 1…”
This paper presents the first theoretical quantitative systems level study of a complete suite of reaction pathways for scanning-probe based ultrahigh-vacuum diamond mechanosynthesis (DMS). A minimal toolset is proposed for positionally controlled DMS consisting of three primary toolsthe (1) Hydrogen Abstraction (HAbst), (2) Hydrogen Donation (HDon), and (3) Dimer Placement (DimerP) tools-and six auxiliary tools-the (4) Adamantane radical (AdamRad) and (5) Germyladamantane radical (GeRad) handles, the (6) Methylene (Meth), (7) Germylmethylene (GM), and (8) Germylene (Germ) tools, and (9) the Hydrogen Transfer (HTrans) tool which is a simple compound of two existing tools (HAbst + GeRad). Our description of this toolset, the first to exhibit 100% process closure, explicitly specifies all reaction steps and reaction pathologies, also for the first time. The toolset employs three element types (C, Ge, and H) and requires inputs of four feedstock molecules-CH 4 and C 2 H 2 as carbon sources, Ge 2 H 6 as the germanium source, and H 2 as a hydrogen source. The present work shows that the 9-tooltype toolset can, using only these simple bulk-produced chemical inputs: (1) fabricate all nine tooltypes, including their adamantane handle structures and reactive tool intermediates, starting from a flat passivated diamond surface or an adamantane seed structure; (2) recharge all nine tooltypes after use; and (3) build both clean and hydrogenated molecularly-precise unstrained cubic diamond C(111)/C(110)/C(100) and hexagonal diamond surfaces of process-unlimited size, including some Ge-substituted variants; methylated and ethylated surface structures; handled polyyne, polyacetylene and polyethylene chains of processunlimited length; and both flat graphene sheet and curved graphene nanotubes. Reaction pathways and transition geometries involving 1620 tooltip/workpiece structures were analyzed using Density Functional Theory (DFT) in Gaussian 98 at the B3LYP/6-311+G(2d p) // B3LYP/3-21G* level of theory to compile 65 Reaction Sequences comprised of 328 reaction steps, 354 unique pathological side reactions and 1321 reported DFT energies. The reactions should exhibit high reliability at 80 K and moderate reliability at 300 K. This toolset provides clear developmental targets for a comprehensive near-term DMS implementation program.
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