Steric and Electronic Properties of the Bulky Terphenyl Ligand Ar^tBu6 (Ar^tBu6 = C₆H₃-2,6-(C₆H₂-2,4,6-^tBu₃)₂) and Synthesis of Its Tin Derivatives Ar^tBu6SnCl, Ar^tBu6SnSn(H)₂Ar^tBu6, and Ar^tBu6SnSnAr^tBu6: A New Route to a Distannyne via Thermolysis of the Asymmetric Hydride Ar^tBu6SnSn(H)₂Ar^tBu6

Abstract

A larger scale, modified synthesis of the bulky terphenyl ligand iodo precursor Ar tBu6 I (1; Ar tBu6 = C 6 H 3 -2,6-(C 6 H 2 -2,4,6-t Bu 3 ) 2 ), featuring six tert-butyl groups on the flanking aryl rings, and the synthesis of its tin derivatives Ar tBu6 SnCl (2), Ar tBu6 SnSn(H) 2 Ar tBu6 (3), and Ar tBu6 SnSnAr tBu6 (4) are described. For the key reagent Ar tBu6 I (1), recently reported by Schrock, Hoyveda, and co-workers, modifications to the synthesis using the easily prepared Grignard reagent EtMgBr to obtain Ar tBu6 MgX, as well as use of their published trituration and iodination protocols in hexane, allowed isolation of ca. 80 g quantities of Ar tBu6 I (1). The tin(II) halide derivative 2 and the unsymmetrical hydride 3 were synthesized by salt metathesis and reduction with DIBAL ( i Bu 2 AlH), respectively. The distannyne 4 was obtained by a new synthetic route by the dehydrogenation of 3 at 100 °C in toluene. It was also synthesized by reduction of 2 with KC 8 . All compounds were characterized using single-crystal X-ray diffraction, multinuclear NMR, UV−vis, and IR spectroscopy. The 119 Sn NMR and UV−vis spectra of 2−4 reveal absorptions considerably shifted from those of other terphenyl-substituted analogues and along with their structural and reactive behavior show that the steric demands of Ar tBu6 are the highest among terphenyl ligands and are sufficiently great to prevent formation of the stannylene Sn(Ar tBu6 ) 2 .

Recent advances of group 14 dimetallenes and dimetallynes in bond activation and catalysis

“…Reductive dehalogenation of di- (R 2 EX 2 ) or trihalometallanes (REX 3 ), dimetallanes (X 2 REERX 2 ), dimetallenes (XREERX), or metallylenes (XRE:) using reductive agents (red.) such as KC 8 , 45,47,56–58 metal naphthalenides, 59,60 and [( Mes Nacnac)Mg] 2 ( Mes Nacnac = (MesNCMe) 2 CH) 61 is the central motif in isolation of these compounds.…”

Structural and electronic studies of substituted m-terphenyl lithium complexes

“…[1][2][3][4][5][6] Although a plethora of m-terphenyl frameworks have been designed, most studies have been structurally focused, aimed at investigating the effects of steric bulk on the geometries, bonding modes, and reactivities of the resulting compounds. [7][8][9][10][11][12][13][14][15][16][17][18] For instance, the solid state structures observed for a series of m-terphenyl lithium complexes vary depending on the steric demands of the flanking ortho-aryl substituents. 19,20 Increasing the steric bulk of 2,6-Ar 2 C 6 H 3 Li alters its aggregation state from a dimer, 19 to a more crowded dimer featuring η 6 -arene coordination of the flanking aryl groups, 20 to a monomer stabilised by a coordinated molecule of benzene, 20 for Ar = Mes (2,4,6-Me 3 C 6 H 2 ), Dipp (2,6-i-Pr 2 C 6 H 3 ) and Tripp (2,4,6-i-Pr 3 C 6 H 2 ) respectively.…”

Low-coordinate first-row transition metal complexes in catalysis and small molecule activation

“…Of particular interest are the relatively new class of cyclic (alkyl) (amino)carbenes (CAACs), which are more σ-donating and π-accepting than N-heterocyclic carbenes; 142 and the recently developed [2,6-(2,4,6-tBu 3 C 6 H 2 ) 2 C 6 H 3 ] − , an incredibly sterically encumbering m-terphenyl ligand, 143 which was recently exploited in the synthesis of several Sn-Sn bonded compounds. 144 Finally, we note the increasing interest in mechanistic investigations of these catalysts, with more researchers undertaking kinetic measurements of these systems rather than simply viewing the reaction as a "black box". Hopefully this will lead to a greater understanding of the factors that underpin the reactivity of low-coordinate metal species and allow for the future rational design of improved catalytic systems.…”