The activation of NH and CO is still an ambitious target for multiply bonded sub-valent silicon compounds. Now, the precise splitting of the N-H bond of ammonia by (Z)-imino(silyl)disilene 1 to give trans-1,2-adduct 2 a at low temperatures (-78 °C) is presented. According to DFT calculations, the stereospecific hydroamination follows a similar mechanism as the recently reported anti-addition of H to the Si=Si bond of 1. The aminosilane 2 b could also be obtained as the formal silylene addition product under thermodynamic reaction control. By applying low temperatures, the activation of CO with 1 selectively afforded the cis-oxadisilacyclobutanone 7-c as [2+2] cycloadduct. By performing the reaction directly at ambient temperatures, a mixture of three different-sized silacycles (4-6) was observed. Their formation was investigated theoretically and their structures were revealed with separate experiments using 1 and the oxygenation agents N O and O .

Combining high catalytic activity with broad monomer scope is an appealing yet challenging task in polymerization catalysis. Examples of such all-rounder catalysts in the ring-opening polymerization (ROP) of lactones are...

The activation of NH3 and CO2 is still an ambitious target for multiply bonded sub‐valent silicon compounds. Now, the precise splitting of the N−H bond of ammonia by (Z)‐imino(silyl)disilene 1 to give trans‐1,2‐adduct 2 a at low temperatures (−78 °C) is presented. According to DFT calculations, the stereospecific hydroamination follows a similar mechanism as the recently reported anti‐addition of H2 to the Si=Si bond of 1. The aminosilane 2 b could also be obtained as the formal silylene addition product under thermodynamic reaction control. By applying low temperatures, the activation of CO2 with 1 selectively afforded the cis‐oxadisilacyclobutanone 7‐c as [2+2] cycloadduct. By performing the reaction directly at ambient temperatures, a mixture of three different‐sized silacycles (4–6) was observed. Their formation was investigated theoretically and their structures were revealed with separate experiments using 1 and the oxygenation agents N2O and O2.

The synthesis and characterization of an Nheterocyclic carbene (NHC)-stabilized silyliumylidene borane adduct [mTer(IMe 4 )with either Me 2 S•BH 3 or tetrahydrofuran (THF)•BH 3 , usage of the amine borane Me 2 NH•BH 3 gives protonation at silicon instead to yield the dication complex [3][OTf] 2 . Alternately, [3][OTf] 2 can be prepared by the addition of triflic acid to [1][OTf]. The reaction outcome strongly depends on the borane source and is evidence of the unprecedented nucleophilic character of [1][OTf] as elucidated by density functional theory (DFT) calculations. [3][OTf] 2 can irreversibly react with one molecule of CO 2 , forming the insertion product [6][OTf] 2 . Subsequent introduction of a second equivalent CO 2 leads to a 1:1 equilibrium of single-([6][OTf] 2 ) and double-CO 2 -insertion ([7][OTf] 2 ) products, as determined by multinuclear NMR spectroscopy, single-crystal X-ray diffraction (SC-XRD) analysis, and supported by theoretical calculations.

Fluorenyl cyclopentadienyl C s -symmetric ansa-metallocene (M = Zr, Hf) complexes I−IV featuring different bridging motifs (C and Si) were synthesized and subsequently examined in the syndiospecific coordinative polymerization of propylene. All complexes were activated in situ with triisobutylaluminum (TIBA) and [Ph 3 C][B(C 6 F 5 ) 4 ] (TrBCF) in order to highlight the benefits of this in situ activation, resulting in a significantly higher molecular weight and a significantly increased productivity in comparison to methylaluminoxane (MAO). The isopropylidene-bridged zirconocene Ia (ZrCl 2 [Me 2 C(η 5 -Flu)(η 5 -Cp)]) exhibited a high productivity (80000 kg PP (mol cat h) −1 ) and stereoregularity ([rrrr] up to 93%) with a moderate molecular weight of polypropylene (PP), whereas the polymerization with the corresponding hafnocene Ib (HfCl 2 [Me 2 C(η 5 -Flu)(η 5 -Cp)]) resulted in a lower productivity and stereoregularity but yielded ultrahigh molecular weight polypropylene (M w = 1100 kg mol −1 ). The backbone in II (HfCl 2 [Ph 2 C(η 5 -Flu)(η 5 -Cp)]) was associated with a higher productivity and molecular weight, while the syndiotacticity was not affected. In contrast, SC-XRD revealed a reduced dihedral angle and D value for Si-bridged hafnocenes III (HfCl 2 [Me 2 Si(η 5 -Flu)(η 5 -Cp)]) and IV (HfCl 2 [Ph 2 Si(η 5 -Flu)(η 5 -Cp)]), resulting in a more constrained geometry of the catalyst. This led to an increased molecular weight, while the productivity as well as the syndiotacticity decreased due to these structural parameters. Activation of Ib and II−IV with n-octyl-modified methylaluminoxane (MMAO) resulted in a lower molecular weight of the polymer, because the transfer of the growing polymer chain onto the Al center was enhanced. Nevertheless, the stereoregularity of MMAO-activated catalysts was slightly increased, probably due to a coordination of the ill-defined MMAO anion during the polymerization. DSC analysis exposed for syndiotactic polypropylene (sPP) produced by the highly active zirconocene Ia a defined melting transition (T m up to 145.2 °C), whereas TIBA/TrBCF-activated hafnocenes Ib and II−IV gave polymers with no observable T m value.

Furan and thiophene diarylmethenes are potential redox-active ligands for metal centers that could be exploited in the development of nontraditional, stoichiometric, and catalytic redox reactions. As such, we describe here the selective meso-deprotonations of dithiophene, difuran, and diimine-difuran diarylmethanes to form the π-conjugated anions, for which only the diimino-difuryl anion is truly isolable and studied by X-ray crystallography. In all cases, facile one-electron oxidation of these anions occurs, which allows the isolation of the neutral dithienyl and diimino-difuryl radicals. UV-Visible and time-dependent density functional theory studies reveal that the oxidation of the dithienyl anion to its radical is associated with an increase in the highest (singly) occupied molecular orbital-lowest unoccupied molecular orbital gap, evident through a hypsochromic shift of the main absorption band in the electronic spectrum, whereas oxidation of the diimino-difuryl anion causes only minor spectroscopic changes. Electrochemical studies support the stability of the radicals with respect to the anion, showing strongly negative oxidation potentials. The control of the redox activity of these diarylmethene carbanions through variation of the nature of the substituents, donor-atom, and the conjugated π-system and their potential as ligands for redox-inert metal centers makes them intriguing candidates as noninnocent partners for redox reactions.