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Reaction of the lithium dithiolene radical 2 • with the imidazolium salt [{(Me)CN( i -Pr)} 2 CH] + [Cl] - (in a 1:1 molar ratio) gives the first stable naked anionic dithiolene radical 3 • , which, when coupled with hexasulfide, [{(Me)CN( i -Pr)} 2 CH] + 2 [S 6 ] 2- ( 4 ), and N-heterocyclic silylene 5 , unexpectedly results in synergic THF ring-opening via a radical mechanism.

This Award Article targets the evolving, yet surprisingly fruitful, chemistry of N-heterocyclic carbenes with low-oxidation-state main-group elements. Specifically, the chemistry of carbene-stabilized diatomic allotropes, diborenes, gallium octahedra, beryllium borohydride, and a host of related compounds will be presented. Providing a valuable historical perspective, the foundational work concerning the organometallic chemistry of gallium with sterically demanding m-terphenyl ligands from this laboratory will also be discussed. [ABSTRACT FROM AUTHOR]

Reaction of N-heterocyclic-carbene (NHC)-stabilized disilicon ( 1) with CuCl gave a carbene-stabilized disilicon-copper(I) chloride complex ( 2). The nature of the structure and bonding in 2 has been investigated by crystallographic, spectroscopic, and computational methods. The dynamic complexation behavior of 2 was experimentally explored by variable-temperature NMR analysis. [ABSTRACT FROM AUTHOR]

Reaction of thiolate 1 with carbene-stabilized diiodo-bis-silylene (2) (in a 2:1 ratio) in THF unexpectedly gives both the first five-membered, sulfur-containing, zwitterionic silylene ring (3) via insertion of the "Si2I" unit of 2 into the olefinic C--H bond of the imidazole ring of 1 and four-membered cyclic silylene (4) via insertion of a silicon(I) atom of 2 into the Cphenyl--N bond of the carbene ligand. The parallel reaction in toluene only gives 3 as the major product. The nature of the bonding in isomeric 3 and 4 was probed by experimental and theoretical methods. [ABSTRACT FROM AUTHOR]

Sulfurization of anionic N-heterocyclic dicarbene, [:C{[N(2,6-Pri2C6H3)]2CHCLi}]n (2), with elemental sulfur (in a 1:2 ratio) in Et2O at low temperature gives 3 by inserting two sulfur atoms into the Li-C (i.e., C2 and C4) bonds in polymeric 2. Further reaction of 3 with 2 equiv of elemental sulfur in THF affords 4• via unexpected C-H bond activation, which represents the first anionic dithiolene radical to be structurally characterized in the solid state. Alternatively, 4• may also be synthesized directly by reaction of 1 with sulfur (in a 1:4 ratio) in THF. Reaction of 4• with GeCl2⋅dioxane gives an anionic germanium(IV)-bis(dithiolene) complex (5). The nature of the bonding in 4• and 5 was probed by experimental and theoretical methods. [ABSTRACT FROM AUTHOR]

The anionic N-heterocyclic dicarbenes (NHDCs) Iaredemonstrated to be a convenient platform from which abnormal NHC (aNHC)–borane complexes V–VIImay be prepared. The anionic NHDC binuclear complex IIand the aNHC mononuclear adduct VIIcan be interconverted through lithiation and protonation,respectively, of the C2 carbon atom of the imidazole ring. [ABSTRACT FROM AUTHOR]

The first anionic N-heterocyclic dicarbene, polymeric [:C{[N(2,6-Pri2C6H3)]2CHCLi(THF)}]n1, containing both normal (C2) and abnormal carbene (C4) centers in the same five- membered imidazole ring (III), has been prepared by lithiation of the imidazole monocarbene, :C{N(2,6-Pri2C6H3)CH}2. The dicar bene nature of 1 was unambiguously demonstrated by the formation of the group 13 Lewis acid adducts (THF)2Li:C{[N(2,6-Pri2C6H3)]2CHC(LA)}, where LA = AIMe3 [2·(THF)2] and BEt3[3·(THF)2]. [ABSTRACT FROM AUTHOR]