Bonding and stability of dinitrogen-bonded donor base-stabilized Si(0)/Ge(0) species [(cAAC(Me)–Si/Ge)(2)(N(2))]: EDA-NOCV analysis

Recently, dinitrogen (N(2)) binding and its activation have been achieved by non-metal compounds like intermediate cAAC-borylene as (cAAC)(2)(B-Dur)(2)(N(2)) [cAAC = cyclic alkyl(amino) carbene; Dur = aryl group, 2,3,5,6-tetramethylphenyl; B-Dur = borylene]. It has attracted a lot of scientific attention from different research areas because of its future prospects as a potent species towards the metal free reduction of N(2) into ammonia (NH(3)) under mild conditions. Two (cAAC)(B-Dur) units, each of which possesses six valence electrons around the B-centre, are shown to accept σ-donations from the N(2) ligand (B ← N(2)). Two B-Dur further provide π-backdonations (B → N(2)) to a central N(2) ligand to strengthen the B–N(2)–B bond, providing maximum stability to the compound (cAAC)(2)(B-Dur)(2)(N(2)) since the summation of each pair wise interaction accounted for the total stabilization energy of the molecule. (cAAC)(B-Dur) unit is isolobal to cAAC–E (E = Si, Ge) fragment. Herein, we report on the stability and bonding of cAAC–E bonded N(2)-complex (cAAC–E)(2)(N(2)) (1–2; Si, Ge) by NBO, QTAIM and EDA-NOCV analyses (EDA-NOCV = energy decomposition analysis coupled with natural orbital for chemical valence; QTAIM = quantum theory of atoms in molecule). Our calculation suggested that syntheses of elusive (cAAC–E)(2)(N(2)) (1–2; Si, Ge) species may be possible with cAAC ligands having bulky substitutions adjacent to the C(cAAC) atom by preventing the homo-dimerization of two (cAAC)(E) units which can lead to the formation of (cAAC–E)(2). The formation of E[double bond, length as m-dash]E bond is thermodynamically more favourable (E = Si, Ge) over binding energy of N(2) inbetween two cAAC–E units.