7-Azaindol-7-ylborate: A Novel Bidentate N^BH₃Chelating Ligand

Abstract

7-Azaindole (H-azain) reacts with sodium borohydride (NaBH4) to yield the sodium salt of the novel 7-azaindol-7-ylborate anion (7-azain-7)BH3 −, two rhodium derivatives of which reveal distinct coordination modes  [Rh{κ2 N,H-H3B(7-azain-7)}(CO)(PPh3)2] and [Rh{κ3 N,H,H′-H3B(7-azain-7)}(PPh3)2]thereby demonstrating how the variable denticity of the ligand may accommodate the varying electronic requirements of the metal center.

Metallasilatranes: Palladium(II) and Platinum(II) as Lone‐Pair Donors to Silicon(IV)

“…The SiÀN bond lengths (1.888(3)-1.917(5) ) are in a typical range for SiÀN bonds in hexacoordinate Si compounds, and the same applies to the SiÀCl bonds (2.151 (1)-2.211(4) ) with the longer Si À Cl bonds being in the Pt complexes, which exhibit a notably shorter trans-disposed M À Si bond. This Si À Cl bond elongation already hints at pronounced donor strength of the Pt atom in [ClSi(m-mt) 4 PtCl]. Further evidence is provided below.…”

“…Within the past decade numerous examples of metallaboratranes followed and have been reviewed and commented on recently. [3] Although further buttressing clamps (e.g., 7-azaindole instead of methimazole) [4] are under investigation for metallaboratrane syntheses, these still rely on the oxidative addition of a B À H bond. The direct formation of metallametallatranes, that is, cage compounds comprising Au!B, Au!Ga, and Au!Al interactions (III), was reported by Bourissou et al [5] Braunschweig et al reported on the compounds IV and V exhibiting Pt 0 !Al III and Pt 0 !Be II interactions (Scheme 1, bottom) and related gallium-containing systems as examples for the straightforward formation of TM!E interactions (E = main-group element), [6] and Fischer et al reported compounds containing Rh I !Ga III bonds.…”

“…The S-donor sites remain in distances between 3.30 and 3.35 from the Si atoms. Whereas Si(mt) 4 4 PdCl] ( Figure 1) [11,12] and [ClSi(m-mt) 4 PtCl] show great similarities to one another.…”

“…Whereas a structurally related tin compound [13] was discovered merely in traces and only characterized by X-ray diffraction and mass spectroscopy, [ClSi(m-mt) 4 PdCl] and [ClSi(m-mt) 4 PtCl] were deliberately prepared and in good yield, thus allowing insights into the TM!E bonding features. The 29 Si cross-polarization/magic-angle spinning (CP/MAS) NMR spectrum of [ClSi(m-mt) 4 PdCl] exhibits three signals (d = À180.0, À182.6, À183.4 ppm) in ratio 1:4:1, as determined by peak deconvolution.…”

“…The 29 Si cross-polarization/magic-angle spinning (CP/MAS) NMR spectrum of [ClSi(m-mt) 4 PdCl] exhibits three signals (d = À180.0, À182.6, À183.4 ppm) in ratio 1:4:1, as determined by peak deconvolution. Thus, the solid-state 29 Si NMR spectrum is in accord with the crystal structure of this compound, which comprises three crystallographically independent Si sites in this ratio.…”