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The experimental charge density of a highly substituted fullerene derivative, the T(sub h)-symmetrical dodekakis-(ethoxycarbonyl)-C60-fullerene cocristallized with difluorobenzene, was determined. This state-of-the-artstudy confirms that presently available technical standards allow for accurate experimental charge density determinations on the structures containing more than 100 atoms.

The synthesis of [n,5]-spiroketals (n = 5, 6) via use of exocyclic enol ethers as starting materials is reported. Addition of catalytic amounts of the Lewis acid [Yb(OTf).sub.3] is observed to facilitate the ring enlargement and increase the yield of the corresponding spiroketal in many synthesis examples.

Bader's partitioning scheme is applied to compare the peptide bond regions of three oligopeptides, yielding eight peptide bond regions. From integration over the atomic volume, very reproducible atoms in molecules charges were calculated.

A cyclic alkyl(amino) carbene (cAAC) stabilized dimer [(cAAC)Si(P-Tip)]2 (2) (Tip = 2,4,6-triisopropylphenyl) is reported. 2 can be considered as a dimer of the heavier ketenimine (R2C═C═N-R) analogue. The dark-red rod-shaped crystals of 2 were synthesized by reduction of the precursor, cAAC-dichlorosilylene-stabilized phosphinidene (cAAC)SiCl2→P-Tip with sodium napthalenide. The crystals of 2 are storable at room temperature for several months and stable up to 215 °C under an inert atmosphere. X-ray single-crystal diffraction revealed that 2 contains a cyclic nonplanar four-membered SiPSiP ring. Magnetic susceptibility measurements confirmed the singlet spin ground state of 2. Cyclic voltammetry of 2 showed a quasi-reversible one-electron reduction indicating the formation of the corresponding radical anion 2•-, which was further characterized by EPR measurements in solution. The electronic structure and bonding of 2 and 2•- were studied by theoretical calculations. The experimentally obtained data are in good agreement with the calculated values. [ABSTRACT FROM AUTHOR]

One and a half decades ago the formation of Si2Cl4 from the intermediate species SiCl2 was theoretically predicted to be exothermic. The hypothetical Si2Cl4 has never been experimentally synthesized and isolated. Herein, we report that the Si2Cl4 species was stabilized as singlet biradical (Cy-cAAC-)2Si2Cl4 utilizing two cAAC (cyclic alkyl(amino) carbene). This compound is stable, isolable, and storable at rt under an inert atmosphere. The electronic structure and bonding were studied by theoretical calculations which revealed that the molecule possesses a singlet biradical ground state with an unpaired electron on each carbene C atom having opposite spin. [ABSTRACT FROM AUTHOR]

The photochemical activation of the C( sp )-C( sp 2 ) bond in Pt(0)-η 2 -aryl-phosphaalkyne complexes leads selectively to coordination compounds of the type L n Pt(aryl)(C≡P). The oxidative addition reaction is a novel, clean, and atom-economic route for the synthesis of reactive terminal Pt(II)-cyaphido complexes, which can undergo [3 + 2] cycloaddition reactions with organic azides, yielding the corresponding Pt(II)-triazaphospholato complexes. The C-C bond cleavage reaction is thermodynamically uphill. Upon heating, the reverse and quantitative reductive elimination toward the Pt(0)-phosphaalkyne-π-complex is observed.

Our new model of electron density augmented by point charges (aug-PROmol) provides an estimation of electrostatic interaction energies including penetration effects ( ChemPhysChem 2016, 17, 2455-2460). In this paper we prove that it can be applied using sources of point charges other than those from direct restrained fitting to electrostatic potential (RESP). We used a newly established databank of tabulated invariom point charges and a widely known semiempirical method. Both sources perform equivalently to the basic aug-PROmol method as well as to reference energies at the DFT-SAPT/aug-cc-pVTZ level of theory. This is possible due to the universal character of the penetration model included in the aug-PROmol. Aug-PROmol may become a basis for development of new nonbonded terms in force fields or a high success rate scoring function.

Due to the inherent difficulties in achieving a defined and exclusive formation of multicomponent assemblies against entropic predisposition, we present the rational assembly of a heteroleptic [Pd 2 L A 2 L B 2 ] 4+ coordination cage achieved through the geometric complementarity of two carefully designed ligands, L A and L B . With Pd(II) cations as rigid nodes, the pure distinctly angular components readily form homoleptic cages, a [Pd 2 L A 4 ] 4+ strained helical assembly and a [Pd 4 L B 8 ] 8+ box-like structure, both of which were characterized by X-ray analysis. Combined, however, the two ligands could be used to cleanly assemble a cis-[Pd 2 L A 2 L B 2 ] 4+ cage with a bent architecture. The same self-sorted product was also obtained by a quantitative cage-to-cage transformation upon mixing of the two homoleptic cages revealing the [Pd 2 L A 2 L B 2 ] 4+ assembly as the thermodynamic minimum. The structure of the heteroleptic cage was examined by ESI-MS, COSY, DOSY, and NOESY methods, the latter of which pointed toward a cis-conformation of ligands in the assembly. Indeed, DFT calculations revealed that the angular ligands and strict Pd(II) geometry strongly favor the cis-[Pd 2 L A 2 L B 2 ] 4+ species. The robust nature of the cis-[Pd 2 L A 2 L B 2 ] 4+ cage allowed us to probe the accessibility of its cavity, which could be utilized for shape recognition toward stereoisomeric guests. The ability to directly combine two different backbones in a controlled manner provides a powerful strategy for increasing complexity in the family of [Pd 2 L 4 ] cages and opens up possibilities of introducing multiple functionalities into a single self-assembled architecture.

A 1,4-diamino-2,3-disila-1,3-butadiene derivative of composition (Me2-cAAC)2(Si2Cl2) (Me2-cAAC = :C(CMe2)2(CH2)N-2,6-iPr2C6H3) was synthesized by reduction of the Me2-cAAC:SiCl4 adduct with KC8. This compound is stable at 0 °C for 3 months in an inert atmosphere. Theoretical studies reveal that the silicon atoms exhibit pyramidal coordination, where the Cl-Si-Si-Cl dihedral angle is twisted by 43.3° (calcd 45.9°). The two silicon-carbon bonds are intermediates between single and double Si-C bonds due to twisting of the C-Si-Si-C dihedral angle (163.6°).

Metal ions with radical centers in their coordination sphere are key participants in biological and catalytic processes. In the present study, we describe the synthesis of the cAAC:ZnCl2 adduct (1) using a cyclic alkylaminocarbene (cAAC) as donor ligand. Compound 1 was treated with 2 equiv of KC8 and LiB(sec-Bu)3H to yield a deep blue-colored dicarbene zinc compound (cAAC)2Zn (2) and the colorless hydrogenated zinc compound (cAACH)2Zn (3), respectively. Compounds 2 and 3 were well characterized by spectroscopic methods and single-crystal X-ray structural analysis. Density functional theory calculations were performed for 2 which indicate that this molecule possesses a singlet biradicaloid character. Moreover, we show the application of 2 in CO2 activation, which yields a zwitterionic cAAC·CO2 adduct.

An efficient total synthesis of (+)-(R)-Pinnatolide is described. As a key step an asymmetric multicomponent domino allylation reaction of methyl levulinate is used to form the quaternary stereogenic center in a highly selective way.

ent-Homoabyssomicins A (1) and B (2) are new complex polycyclic spirotetronate metabolites isolated from Streptomyces sp. isolate Ank 210. The structures of 1 and 2 were elucidated by detailed spectroscopic analyses of 1D and 2D NMR data. The absolute configuration of 1 was established by subsequent single-crystal X-ray diffraction studies.

Pentacoordinate silicon fluorides L(1)SiF(3) (2a), L(2)SiF(3) (2b), and (L(3)SiF(2))(2) (2c)(2) based on amidinate (L(1) = PhC(N(t)Bu)(2)), guanidinate (L(2) = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate), and triazapentadienate (L(3) = NC(NMe(2))NC(NMe(2))NAr; Ar = 2,6-(i)Pr(2)C(6)H(3)) ligands were prepared by fluorination of the corresponding chlorosilanes L(1)SiCl(3) (1a), L(2)SiCl(3) (1b), and L(3)SiCl(2) (1c) with Me(3)SnF at ambient temperature. Compounds 1b, 1c, 2a, 2b, and (2c)(2) were characterized by (1)H, (13)C, (19)F, and (29)Si NMR spectroscopic studies. Molecular structures of 1b, 1c, 2a, and (2c)(2) were determined by single crystal X-ray structural analysis. Invariom refinement involving non-spherical scattering factors of the Hansen-Coppens multipole model was performed for 1b. Compound L(3)SiF(2) (2c) is dimeric both in the solid state and in solution, whereas its chloro-analogue 1c is monomeric. The attempted synthesis of diamidinatotetrachlorodisilane by reaction of lithium amidinate with Si(2)Cl(6) led to the formation of the silane (1a) and the silylene L(1)SiCl (3). Reaction of Si(2)Cl(6) with N-heterocyclic carbenes (NHC) afforded NHC adducts of dichlorosilylene and SiCl(4). A one pot method for the preparation of base-stabilized silylenes from Si(2)Cl(6) is discussed.

In a screening of micro-organisms for new secondary metabolites, two unprecedented tricyclic highly functionalized ketal-lactone metabolites, named lucknolide A (1) and lucknolide B (2), have been isolated, and the compounds were characterized by extensive NMR and mass spectroscopic studies. Single-crystal X-ray diffraction experiments on 1 and 2 were performed, and the absolute configuration of 1 was determined.

The first synthesis of anti-fused oligoannelated THF moieties is reported. The key transformation of the synthetic sequence, consisting of cyclopropanation, reduction and oxidation, is the expansion of a push-pull-substituted three-membered ring into a five-membered enol ether system. A repetition of the sequence allows the creation of oligoacetals up to a nonacyclic system.