NH bond activation of ammonia and amines by ditetrelenes: key insights into the stereochemistry of nucleophilic addition

Synthesis, Reactivity, and Complexation with Fe(0) of a Tight-bite Bis(N-heterocyclic silylene)

The synthesis, reactivity, and complexation with Fe(0) precursor of a tight-bite bis(N-heterocyclic silylene) (bis(NHSi)) ligand 1 are reported. The reaction of 1 with p-toluidine led to the activation of both N-H bonds across Si(II) atoms to afford a four-membered heterocyclic cyclodisilazane 2, with hydride substituents attached to five-coordinate Si atoms. A 1 : 2 reaction of 1 with Fe(CO)5 led to an intriguing dinuclear complex 3 featuring a five-membered (N-Si-Fe-Fe-Si) ring with a Fe-Fe bond distance of 2.6892(13) Å. All compounds (1-3) were thoroughly characterized by various spectroscopic methods and X-ray diffraction studies conclusively established their molecular structures. DFT calculations were carried out to shed light on bonding and energetic aspects in 1-3.

Facile Reduction of Phosphine Oxides and <i>H</i>-Phosphonates by Ditetrelenes

The addition of secondary phosphine oxides to tetramesityldisilene and -digermene results in the mild, partial reduction of the P(V) centre of the organophosphorus oxide to P(III) to yield disilyl and digermyl phosphinite derivatives and illustrates the potential of ditetrelenes to serve as mild reducing agents under ambient conditions. An analogous reaction happens with <i>H</i>-phosphonates. Mechanistic experiments, including deuterium-labelling, kinetic isotope effect (KIE) and variable time normalization analysis (VTNA) experiments, reveal that the 1,3-PH addition likely proceeds through a stepwise reaction pathway with the organophosphorus oxide acting as the nucleophile towards the ditetrelene. Furthermore, a facile exchange between the R₂PO- moiety on the digermylphosphinite with the R₂PO moiety of phosphine oxides was discovered and likely proceeds through a direct substitution mechanism.