Unsymmetrical sp2 -sp3 Disilenes

Amidinato silylene-based inorganic aromatic rings

Aromaticity is a key concept that underpins the behavior and applications of a wide range of chemical compounds. Its impact on stability, reactivity, biological functions, material properties, and environmental persistence underscores the importance of understanding and harnessing aromaticity in chemistry and materials sciences. We have been pioneers in the field of silylene chemistry and recently, our silylene molecules have been used to synthesize several inorganic aromatic ring compounds. Aromaticity in inorganic compounds is not commonly observed; hence, inorganic aromatic rings derived from silylene would further enhance our understanding of aromaticity and stability. Herein, we discuss the inorganic aromatic rings which have been synthesized from amidinato silylene.

Stereodivergent sila-germylenation vs. sila-stannylenation of an internal alkyne

We report on the insertion of electron deficient alkyne, dimethyl acetylene dicarboxylate (DMAD), into the E-Si bond of hypersilyl tetrylenes, PhC(NtBu)2ESi(SiMe3)3 (E = Ge and Sn), at room temperature. Uniquely, the germylene leads to cis alkenes, while the stannylene gives access to trans alkenes, and the insight into divergent stereoselectivity has been obtained by DFT studies.

Activation of carbon disulfide by a hypersilyl germylene

In this work, the insertion of CS2 into the Ge-Si bond of PhC(NtBu)2Ge-Si(SiMe3)3 (1) has been investigated, resulting in the formation of PhC(NtBu)2Ge-C(S)-S-Si(SiMe3)3 (2). Interestingly, the addition of NHC to 2 allows the release of NHC·CS2 with concomitant regeneration of 1. Addition of another equivalent of 1 or an analogous hypersilyl silylene, [PhC(NtBu)2Si-Si(SiMe3)3], to 2 led to the formation of compounds with a GeS (3) or a SiS (4) bond.

Tridentate NacNac Tames T-Shaped Nickel(I) Radical

The reaction of a nickel(II) chloride complex containing a tridentate β-diketiminato ligand with a picolyl group [2,6-iPr2 -C6 H3 NC(Me)CHC(Me)NH(CH2 py)]Ni(II)Cl (1)] with KSi(SiMe3 )3 conveniently afforded a nickel(I) radical with a T-shaped geometry (2). The compound's metalloradical nature was confirmed through electron paramagnetic resonance (EPR) studies and its reaction with TEMPO, resulting in the formation of a highly unusual three-membered nickeloxaziridine complex (3). When reacted with disulfide and diselenide, the S-S and Se-Se bonds were cleaved, and a coupled product was formed through carbon atom of the pyridine-imine group. The nickel(I) radical activates dihydrogen at room temperature and atmospheric pressure to give the monomeric nickel hydride.

Synthesis and reactivity of N-heterocyclic carbene (NHC)-supported heavier nitrile ylides

The synthesis and isolation of stable heavier analogues of nitrile ylide as N-heterocyclic carbene (NHC) adducts of phosphasilenyl-tetrylene [(NHC)(TerAr)Si(H)PE14(TerAr)] (E14 = Ge 1, Sn 2; TerAr = 2,6-Mes2C6H3, NHC = IMe4) are reported. The delocalized Si-P-E14 π-conjugation was examined experimentally and computationally. Interestingly, the germanium derivative 1 exhibits a 1,3-dipolar nature, leading to an unprecedented [3 + 2] cycloaddition with benzaldehyde, resulting in unique heterocycles containing four heteroatoms from group 14, 15, and 16. Further exploiting the nucleophilicity of germanium, activation of the P-P bond of P4 was achieved, leading to a [(NHC)(phosphasilenyl germapolyphide)] complex. Moreover, the [3 + 2] cycloaddition and the σ-bond activation by 1 resemble the characteristics of the classic nitrile ylide.

A zwitterionic disilanylium from an unsymmetrical disilene

The reaction of PhC(NtBu)₂SiSi(SiMe₃)₃ (1) with Me₃SiCH₂Cl afforded an unsymmetrical sp²-sp³ disilene, 2, with concomitant elimination of Me₃SiCl. The analogous reaction with PhC(NtBu)₂SiCl resulted in the oxidative addition of the C-Cl bond at the Si(II) atom (3). The reactions of 2 with sulfur and selenium led to compounds with SiE (ES (4) and Se (5)) double bonds. Tellurium reacted differently with 2 and furnished a zwitterionic compound, 6.

A strongly twisted SiSi bond with resemblance to a buckled dimer in an unexpected isomer of hexasilabenzene

The reductive debromination of {N(SiMe₃)Ph}SiBr₃1 with Rieke magnesium yields the six-vertex amido-substituted silicon cluster 2 with zwitterionic character that represents an unprecedented isomer of hexasilabenzene. The topology of Si1 and Si2 in 2 has bonding features of a highly twisted disilene and resembles that of a buckled dimer of Si(100)2 × 1 reconstructed surfaces. Cluster 2 forms the adducts 3 and 4 with NHC^Me4 and DMAP, respectively. The NHC adduct 4 additionally coordinates to BH₃ which affords the saturated cluster BH₃NHC^Me4Si₆{N(SiMe₃)Ph}₆ (5). Furthermore, 2 undergoes addition with MeI and iodine to form the halogenated silicon clusters 6 and 7, respectively.

Pyridylpyrrolido ligand in Ge(II) and Sn(II) chemistry: synthesis, reactivity and catalytic application

In our previous communication, we have reported the synthesis of a new chlorogermylene (B) featuring a pyridylpyrrolido ligand. This study details the preparation of a series of new germylenes and stannylenes starting from B. A transmetallation reaction between B and SnCl₂ led to the analogous chlorostannylene (1) with the simultaneous elimination of GeCl₂. This is a very unusual example of transmetallation between two elements of the same group. The preparation of 1via lithiation led to the formation of 2 as a side product, where the ortho C-H bond of the pyridine ring was activated and functionalized with a ⁿBu moiety. Subsequently, B and 1 were used as precursors to generate germylene (4) and stannylene (5) featuring tris(trimethylsilyl)silyl (hypersilyl) moieties. We also prepared tetrafluoropyridyl germylene (6) by reacting 4 with C₅F₅N with the simultaneous elimination of (Me₃Si)₃SiF by utilizing the fluoride affinity of the silicon atom. As there is scarcity of Sn(II) compounds as single-site catalysts, we investigated 5 as a catalyst towards the hydroboration of aldehydes, ketones, alkenes and alkynes. All the compounds have been characterized by single-crystal X-ray diffraction and by state of the art spectroscopic studies.