Despite tremendous efforts to synthesize isolable compounds with an Si=O bond, silicon analogues of ketones that contain an unperturbed Si=O bond have remained elusive for more than 100 years. Herein, we report the synthesis of an isolable silicon analogue of a ketone that exhibits a three‐coordinate silicon center and an unperturbed Si=O bond, thus representing the first example of a genuine silanone. Most importantly, this silanone does not require coordination by Lewis bases and acids and/or the introduction of electron‐donating groups to stabilize the Si=O bond. The structure and properties of this unperturbed Si=O bond were examined by a single‐crystal X‐ray diffraction analysis, NMR spectroscopy, and theoretical calculations. Bimolecular reactions revealed high electrophilicity on the Si atom and high nucleophilicity on the O atom of this genuine Si=O bond.
The stabilization of silicon(II) and germanium(II) dihydrides by an intramolecular Frustrated Lewis Pair (FLP) ligand, PB, i Pr 2 P(C 6 H 4)BCy 2 (Cy = cyclohexyl) is reported. The resulting hydride complexes [PB{SiH 2 }] and [PB{GeH 2 }] are indefinitely stable at room temperature, yet can deposit films of silicon and germanium, respectively, upon mild thermolysis in solution. Hallmarks of this work include: 1) the ability to recycle the FLP phosphine-borane ligand (PB) after element deposition, and 2) the single-source precursor [PB{SiH 2 }] deposits Si films at a record low temperature from solution (110 8C). The dialkylsilicon(II) adduct [PB{SiMe 2 }] was also prepared, and shown to release poly(dimethylsilane) [SiMe 2 ] n upon heating. Overall, this study introduces a "closed loop" deposition strategy for semiconductors that steers materials science away from the use of harsh reagents or high temperatures. Scheme 1. General concept of FLP-assisted semiconductor (E) and polymer [ER 2 ] n deposition (E = Si, Ge).
A phenylene multiring with a corannulenoidal skeleton was synthesized. Geodesic constraints over 20 phenylene panels resulted in its nanometer-sized, bowl-shaped molecular structure, which was unequivocally revealed by crystallographic analysis. The crystal structure also showed the presence of a bowl-in-bowl dimeric assembly, which was driven by entropic factors in solution.
A saddle-shaped macromolecule has been synthesized. The molecule was designed as a geodesic saddle with 1,3,5-trisubstituted benzene (named phenine) as the fundamental unit. The phenines were woven into a polygonal framework that was composed of 168 sp -hybridized carbon atoms. The saddle-shaped structure with unique symmetry showed atypical conformational changes. The biaryl linkages in this molecule had a small energy barrier for rotation, and these structural fluctuations resulted in seven H NMR resonances representing 84 aromatic hydrogen atoms. Nevertheless, the overall saddle shape of the molecule was persistent, and the "up" and "down" orientations of phenine moieties circulated to give average H resonances. The structural characteristics of this molecule, including the anomalous entropy-driven dimerization, may deepen our understanding of defect-rich graphitic sheets.
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