Expanding the Steric Coverage Offered by Bis(amidosilyl) Chelates: Isolation of Low-Coordinate N-Heterocyclic Germylene Complexes

Abstract

The synthesis and coordination chemistry of a series of dianionic bis(amido)silyl and bis(amido)disilyl, [NSiN] and [NSiSiN], chelates with N-bound aryl or sterically modified triarylsilyl (SiAr(3)) groups is reported. In order to provide a consistent comparison of the steric coverage afforded by each ligand construct, various two-coordinate N-heterocyclic germylene complexes featuring each ligand set were prepared and oxidative S-atom transfer chemistry was explored. In the cases where clean oxidation transpired, sulfido-bridged centrosymmetric germanium(IV) dimers of the general form [LGe(μ-S)](2) (L = bis(amidosilyl) ligands) were obtained in lieu of the target monomeric germanethiones with discrete Ge═S double bonds. These results indicate that the reported chelates possess sufficient conformational flexibility to allow for the dimerization of LGe═S units to occur. Notably, the new triarylsilyl groups (4-RC(6)H(4))(3)Si- (R = (t)Bu and (i)Pr) still offer considerably expanded degrees of steric coverage relative to the parent congener, -SiPh(3,) and thus the use of substituted triarylsilyl groups within ligand design strategies should be a generally useful concept in advancing low-coordination main group and transition-metal chemistry.

Stable N‐Heterocyclic Germylenes of the Type [Fe{(η5‐C5H4)NR}2Ge] and Their Oxidation Reactions with Sulfur, Selenium, and Diphenyl Diselenide

“…Diaminogermylenes (R 2 N) 2 Ge characteristically undergo oxidative additions with elemental sulfur and selenium. The structurally characterized products invariably are dimers of the type [(R 2 N) 2 Ge(μ‐ E )] 2 ( E = S, Se) with an approximately diamond‐shaped Ge 2 E 2 core.…”

“…Reactions with the molecular allotrope Se 8 (red selenium) and with S 8 afforded products of the type [ 1R Ge(μ‐E)] 2 , whose purification and spectroscopic characterization was severely hampered by their generally low solubilities, which, however, are not unprecedented for compounds of this type. [14b] The 1,1,2,2‐tetramethylpropyl substituent turned out to exert a pronounced solubilizing effect in this context. Conspicuously short intramolecular CH ··· Se contacts compatible with hydrogen bonds were observed in the structures of the alkyl‐substituted compounds 1 t Bu Ge(SePh) 2 , [ 1Ad Ge(μ‐Se)] 2 , and [ 1Pr* Ge(μ‐Se)] 2 , with the latter derivative showing the shortest such contact described to date.…”

Accessing Low‐Valent Inorganic Cations by Using an Extremely Bulky N‐Heterocyclic Carbene

“…Future work will involvem odification of the umbrella-shaped CPh 3 ,i ncluding the formation of structurally flexible alkyl analogues, [17,18] and the introduction of the ITrl igand scaffoldt ot he domain of metal-mediated catalysis. The ability of this ligand to act as at wo-electron donor along with supplying added arene-element interactions facilitated the isolation of aq uasi one-coordinate Tl I cation, [(ITr)Tl] + .T his thermally stable species is av ersatile "all-in-one" transmetalation/ligationr eagent and was used to generate new low-coordinate main group cations (as was exemplified by the successful synthesis of a[ GeCl] + cation).…”

Reactivity of a Bicyclo[2.1.1]hexene Germylene towards Elemental Chalcogens

“…Common to all structures is an almost planar central Ge 2 Ch 2 four‐membered ring with bond angles close to 90° (Ge–Ch–Ge = 83–86°; Ch–Ge–Ch = 93–97°). The Ge–Ch bonds in all three digermetanes exceed tabulated standard bond lengths by 1–6 pm (Table ) but they have the typical length of Ge–Ch bonds in Ge 2 Ch 2 entities , . The structural data of compounds 8 indicate no substantial Ch/Ch or Ge/Ge interaction.…”

“…Digermetanes 8 have bright colors in solution and in solid state (see Figure S1, Supporting Information), in contrast to related germanium‐chalcogen four‐membered ring compounds that are colorless to light yellow . The origin of these colors are two strong absorptions between λ max = 332–341 nm and λ max = 509–584 nm.…”