Precise Activation of Ammonia and Carbon Dioxide by an Iminodisilene

Abstract

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.

Widening the Landscape of Small Molecule Activation with Gold‐Aluminyl Complexes: A Systematic Study of E−H (E=O, N) Bonds, SO2 and N2O Activation

“…Experimental reactivity of the [ t Bu 3 PCuAl(NON)] complex with 3‐hexyne ( 9 – 10 ) [18] . Examples of experimental reactivity of disilenes (Tip = 2,4,6‐triisopropylphenyl, TMOP = 2,4,6‐trimethoxyphenyl, NHI = N‐heterocyclic imine) with NH 3 and N 2 O ( 11 – 14 ) [19] …”

“…Clearly, this state‐of‐the‐art demonstrates the high importance of finding new strategies for its synthetic utilization, especially via selective homogeneous catalysis. Note that, for instance, disilene 11 (Scheme 1) has been reported to efficiently activate N−H bonds in ammonia, leading to the hydroamminated species 12 [19] …”

“…) [39–41] Clearly new strategies for its capture, activation and removal are particularly attractive, especially since it can be in principle also used as a synthetic reagent, for instance with the role of O‐atom donor [42,43] . Note, again, that the efficient reduction of N 2 O with Group 14 dimetallenes has been extensively reported (see as examples 8 and 14 in Scheme 1) [8,9,19] and that, in general, there is considerable interest around the exploration of novel N 2 O cooperative bimetallic activation processes, both from a biomimetic and a synthetic perspective [44] …”

On the Stereochemistry of the NH Bond Activation of Ammonia or Amines by Disilenes: Predictability

“…It has long been recognized that the disilenes are able to activate the O‐H bond in water and alcohols; in fact, the reaction with water and alcohols is one of the most extensively investigated reactions of disilenes [6–8] . Disilene activation of σ‐bonds in other important small molecules, such as NH 3 [9–13] 1 and H 2 , [14] has recently been realized. With the ability to selectively give the NH activated product in high yield rather than the coordinated donor adduct, the promise of disilenes in NH activation chemistry is particularly attractive and, to realize the potential, a thorough understanding of the mechanism and stereochemistry of this fundamental reaction is needed.…”

“…The addition of ammonia to ( Z )‐imino(silyl)disilene Z‐ 1 , a disilene with a highly trans ‐bent and twisted structure [fold angle ( θ )=37.86 and 39.03°, and twist angle ( τ )=23.1°), has been studied by Inoue and coworkers and was found to give the anti ‐isomer [15] of disilylamine 2 , stereospecifically (Scheme 1). [11] The mechanism of the addition of ammonia and dimeric ammonia to disilene Z‐ 1 was examined computationally. The reaction was reported to proceed via an “anti ‐addition pathway” in a single step.…”