Monatomic zero-valent silicon and germanium complexes (named silylones and germylones) stabilised by neutral donating ligands emerged only recently as a new class of low-valent Group 14 element compounds. Featuring four...

Metrics & More Article Recommendations CONSPECTUS: Silylenes are divalent silicon species with an unoccupied 3p orbital and one lone pair of electrons at the Si II center. Owing to the excellent σ-donating ability of amidinatobased silylenes, which stems from the intramolecular imino-N donor interaction with the vacant 3p orbital of the silicon atom, Nheterocyclic amidinato bis(silylenes) [bis(NHSi)s] can serve as versatile strong donating ligands for cooperative stabilization of central atoms in unusually low oxidation states. Herein, we present our recent achievement on the application of bis(NHSi) ligands with electronically and spatially different spacers to main-group chemistry, which has allowed the isolation of a variety of low-valent compounds consisting of monatomic zero-valent group 14 E 0 complexes (named "metallylones", E = Si, Ge, Sn, Pb); monovalent group 15 E I complexes (E = N, P, isoelectronic with metallylones); and diatomic low-valent E 2 complexes (E = Si, Ge, P) with intriguing electronic structures and chemical reactivities. The role of the Si II •••Si II distance was revealed to be crucial in this chemistry. Utilizing the pyridine-based bis(NHSi) (Si•••Si distance: 7.8 Å) ligand, germanium(0) complexes with additional Fe(CO) 4 protection at the Ge 0 site have been isolated. Featuring a shorter Si•••Si distance of 4.3 Å, the xanthene-based bis(NHSi) has allowed the realization of the full series of heavy zero-valent group 14 element E 0 complexes (E = Si, Ge, Sn, Pb), while the o-carborane-based bis(NHSi) (Si•••Si distance: 3.3 Å) has enabled the isolation of Si 0 and Ge 0 complexes. Remarkably, reduction of the o-carborane-based bis(NHSi)-supported Si 0 and Ge 0 complexes induces the movement of two electrons into the o-carborane core and provides access to Si I −Si I and Ge I −Ge I species as oxidation products. Additionally, the o-carborane-based bis(NHSi) reacts with adamantyl azide, leading to a series of nitrogen(I) complexes as isoelectronic species of a carbone (C 0 complex). Moreover, cooperative activation of white phosphorus gives bis(NHSi)-supported phosphorus complexes with varying and unexpected electronic structures when employing the xanthene-, o-carborane-, and anilinebased bis(NHSi)s. With the better kinetic protection provided by the xanthene-based bis(NHSi), small-molecule activation and functionalization of the bis(NHSi)-supported central E or E 2 atoms (E = Si, Ge, P) are possible and furnish several novel functionalized silicon, germanium, and phosphorus compounds.With knowledge of the ability of chelating bis(NHSi)s in coordinating and functionalizing low-valent group 14 and 15 elements, the application of these ligand systems to other main-group elements such as group 2 and 13 is quite promising. To fully understand the role of the NHSi in a bis(NHSi) ligand, introducing a mixed ligand, i.e., the combination of an NHSi with other functional groups, such as Lewis acidic borane or Lewis basic borylene, in one chelating ligand could lead to new types of low-valent main-...

Terminal aluminium and gallium imides of the type K[(NON)M(NR)], bearing heteroatom substituents at R, have been synthesised via reactions of anionic aluminium(I) and gallium(I) reagents with silyl and boryl azides (NON = 4,5-bis(2,6-diisopropyl-anilido)-2,7-di-tert-butyl-9,9-dimethyl-xanthene). These systems vary significantly in their lability in solution: the N(SiiPr3) and N(Boryl) complexes are very labile, on account of the high basicity at nitrogen. Phenylsilylimido derivatives provide greater stabilization through the -acceptor capabilities of the SiR3 group. K[(NON)AlN(SitBuPh2)] offers a workable compromise between stability and solubility, and has been completely characterized by spectroscopic, analytical and crystallographic methods. The silylimide species examined feature minimal pi-bonding between the imide ligand and aluminium/gallium, with the HOMO and HOMO-1 orbitals effectively comprising orthogonal lone pairs centred at N. Reactivity-wise, both aluminium and gallium silylimides can act as viable sources of nitride, [N]3-, with systems derived from either metal reacting with CO to afford cyanide complexes. By contrast, only the gallium system K[(NON)Ga{N(SiPh3)}] is capable of effecting a similar transformation with N2O to yield azide, N3-, via formal oxide/nitride metathesis. The aluminium systems instead generate RN3 via transfer of the imide fragment [RN]2-.