Exploring structural trends for complexes of Me2E(OSO2CF3)2 (E = Si, Ge, Sn) with pyridine derivatives

Abstract

The coordination of Me2E(OTf)2 (E = Si, Ge, Sn) acceptors by dmap or 2,2'-bipy furnishes two series of complexes which exhibit distinct structural trends that correlate with the covalent radii of the tetrael elements, and which contrast complexes of these ligands with EX4 (X = Cl or Br).

Reactive p-block cations stabilized by weakly coordinating anions

“…Many of these [R 3 Si-L] + ions stabilized by different σ-donors are known: with nitriles, 297 – 299 pyridine, 296 , 300 water, 301 o -dichlorobenzene, 81 sulfur dioxide 81 and bipyridine. 302 Even though 2,6-bis(2,6-difluorophenyl)phenyldimethylsilylium ion has no additional ligand acting as a σ-donor, the cationic center is stabilized by one fluorine of each 2,6-difluorophenyl-substituent ( Fig. 40 ).…”

“… 303 With the stronger stabilizing DMAP, the dication [Me 2 Si(dmap) 2 ] 2+ has been synthesized. 302 …”

“… 298 In addition, together with the analogous silicon complex, [Me 2 Ge(bipy)(OTf)] + [OTf] – has been published. 302 Interesting is however, that the corresponding substances with DMAP coordinating to germanium and the ones with DMAP or bipyridine coordinating to tin have to be described as ion-like, since in all of them both [OTf] – anions do have close contacts to the cationic center. 302 As already stated for silicon, symmetrical compounds of the type [R 3 E–X–ER 3 ] + are somewhat special since the positive charge is evenly distributed and it is not possible to speak of an cation and a ligand anymore.…”

Silicon Tetrakis(trifluoromethanesulfonate): A Simple Neutral Silane Acting as a Soft and Hard Lewis Superacid

“…[5,6] Other silicon(IV)based LAs are routinely used in organic synthesis, with the commercially available TMSOTf (TMS = Me 3 Si) arguably being prevalent, [7] but far from being a LSA. [3] Bis-and tris(triflate) silanes potentially represent stronger LAs, but have mainly served as building blocks for polysilane syntheses [8,9] or as precursors for silicon-based polycations [10,11] with cleavage of the SiÀOTf bonds. Donor-free Si(OTf) 4 has not been isolated to date, [9] but recently, a high FIA was calculated for Si(OTf) 4 suggesting its Lewis superacidity.…”

A 2,2′-bipyridine coordination complex of [ICl2]+

“…[5][6][7] Burford has also recently used bpy to investigate the coordination chemistry of Me 2 ECl 2 type compounds from group 14 (4E). 8 Here we report on the synthesis of a new type of iodine(III) compounda square planar [ICl 2 ] + cation stabilized by bpy, via a straightforward synthesis from ICl 3 . An investigation of the electronic structure was undertaken and preliminary investigation of the chemistry of this compound is also described, demonstrating that it is a competent oxidant.…”