A Triatomic Silicon(0) Cluster Stabilized by a Cyclic Alkyl(amino) Carbene

Abstract

Reduction of the neutral carbene tetrachlorosilane adduct (cAAC)SiCl4 (cAAC=cyclic alkyl(amino) carbene :C(CMe2)2 (CH2)N(2,6-iPr2C6H3) with potassium graphite produces stable (cAAC)3Si3, a carbene-stabilized triatomic silicon(0) molecule. The Si-Si bond lengths in (cAAC)3Si3 are 2.399(8), 2.369(8) and 2.398(8) Å, which are in the range of Si-Si single bonds. Each trigonal pyramidal silicon atom of the triangular molecule (cAAC)3Si3 possesses a lone pair of electrons. Its bonding, stability, and electron density distributions were studied by quantum chemical calculations.

Reactivity of NHC Alane Adducts towards N‐Heterocyclic Carbenes and Cyclic (Alkyl)(amino)carbenes: Ring Expansion, Ring Opening, and Al−H Bond Activation

“…We also tried severalt imes to obtain single crystals suitable for X-ray diffraction of trans-(iPr 2 Im) 2 ·AlH 3 (5)f rom saturated solutionso ft he compound in different solvents, but again we were not successful. Instead, we characterized crystallographically the compound [(iPr 2 Im) 4 ·AlH 2 ][(H 3 Al a iPr 2 Im)·AlH 3 ]( 8; Figure 4, right), whichw as repeatedly obtained by the reaction of (iPr 2 Im)·AlH 3 (3)w ith iPr 2 Im in Et 2 O( a denotes coordination as aNHC). Similarly,w er epeatedly crystallized [(iPr 2 Im) 4 ·AlH 2 ] [(iPr 2 Im) 2 Li(AlH 4 ) 2 ]w ith one molecule of (iPr 2 Im)·AlH 3 (3)i nt he unit cell startingf rom lithium aluminumh ydride and 2equivalents of iPr 2 Im in Et 2 O( see Figure S104 in the Supporting Information).…”

“…Instead, we characterized crystallographically the compound [(iPr 2 Im) 4 ·AlH 2 ][(H 3 Al a iPr 2 Im)·AlH 3 ]( 8; Figure 4, right), whichw as repeatedly obtained by the reaction of (iPr 2 Im)·AlH 3 (3)w ith iPr 2 Im in Et 2 O( a denotes coordination as aNHC). Similarly,w er epeatedly crystallized [(iPr 2 Im) 4 ·AlH 2 ] [(iPr 2 Im) 2 Li(AlH 4 ) 2 ]w ith one molecule of (iPr 2 Im)·AlH 3 (3)i nt he unit cell startingf rom lithium aluminumh ydride and 2equivalents of iPr 2 Im in Et 2 O( see Figure S104 in the Supporting Information). In the cationic part, [(iPr 2 Im) 4 ·AlH 2 ] + ,o ft hese ionic compounds, the aluminum cation is surrounded by four NHC ligandsa nd two trans-configured hydride ligands, which form an almosti deal octahedral coordination polyhedron around the metal ion.…”

“…Research on N-heterocyclic carbenes( NHCs) and relatedm olecules [1] has clearly demonstrated in the last decade that their application is not limited to their use as (spectator) ligands in transition-metalc hemistry and catalysis or to their application as stabilizers for subvalent main group element compounds. [2][3][4] Carbenes themselves show ar ich diversity in their reactionp atterns with main group elementh ydrides and organyls. [5] We and othersd emonstrated earlier that, depending on the electronic and steric properties of the carbene and on the main group element compound used, variousr eaction channels exist.…”

S–H Bond Activation in Hydrogen Sulfide by NHC-Stabilized Silyliumylidene Ions

“…Key to these developments have been the usage of suitable synthetic methodologies in combination with thermodynamic and kinetic stabilization by appropriately chosen ligands. In particular, for the heavier carbon analogue silicon, a plethora of studies reported new low-valent compounds in recent years [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and the chemistry of silylene base adducts has already been carefully developed [14,[26][27][28][29][30][31][32][33][34][35][36]. Before these findings, silyliumylidene ions, cationic Si(II) species were found to be promising as similar versatile Lewis amphiphiles [37,38].…”

Mono‐ and Dicoordinate Germanium(0) as a Four‐Electron Donor

“…Whilet he binuclear derivatives even preceded the mononuclear versions (III: D = NHC, CAAC;E= Si, Ge, Sn), [7][8][9] af irst example for at rinuclear tetrel(0)s pecies( IV:D= CAAC;E= Si)w as reported only recently (Scheme 1). [10] The potentialo fs uch strongly nucleophilic tetrel(0)-base adducts as ligands towards transition metals hadb een pointed out early on by Frenking. [1a, 11] In particular,i nc ase of two and three-coordinate mononuclear tetrel(0)s pecieso ft ype I and II the tetrel centref eatures two lone pairs of electrons that are available for coordination to one or two Lewisa cidic acceptors as documentedb yt he isolation of V (D = NHC;E= Si, Ge) and VI (D = NHC; E= Si)i n the Driess group.…”