²⁹Si–¹H IMPACT HMBC: a suitable tool for analyzing silylated derivatives

Abstract

A modified version of the IMPACT heteronuclear multiple bond correlation (HMBC) has allowed the characterization of an organosilane and a tetrasilylated yttrium complex. With the help of this sequence, an average gain in sensitivity close to 2 has been obtained compared with the standard HMBC experiment for disilanes as well as for yttrium complexes containing silylated ligands. This modified version of this long-range correlation experiment opens the way for following kinetics in the range of a fraction of a minute and to study by NMR low concentrated samples and low abundant nuclei.

Probing Long‐Range Anisotropic Interactions: a General and Sign‐Sensitive Strategy to Measure 1H–1H Residual Dipolar Couplings as a Key Advance for Organic Structure Determination

“…However, in most cases, these cause no or minimal complications for long‐range coupling measurements, and it should be noted that other pure shift methods are fully ineffective at homo‐decoupling such equivalent protons. For this reason, PSYCHEDELIC greatly improves the applicability of 1 H– 1 H RDCs for enantiodiscrimination compared to previous methods, as it experiences no negative impact from 2 D HH couplings in methyl groups and provides excellent results even in regions of the spectrum that are hard to decouple with selective pulses. The Supporting Information contains an example on ibuprofen in comparison with previous methods.…”

Current developments in homonuclear and heteronuclear J‐resolved NMR experiments

“…Different δ / J HH coupling patterns obtained in homonuclear J HH ‐resolved ( J res), selective J HH ‐resolved (SERF, GSERF, PSYCHE, and their homodecoupled versions) and δ ‐resolved ( F 1 ‐homodecoupled, DIAG, …) NMR experiments…”

“…The J res spectra are used to extract and identify individual multiplet J structures in overlapped regions, which can facilitate the measurement of J magnitudes but without having an a priori assignment between coupled protons. A doubly selective refocusing (SERF) experiment was initially proposed to carry out the measurement of specific J HH without assignment problems . The SERF method applies two frequency‐selective 180° pulses at two well‐isolated protons (referred to as the passive spin B and the active spin A) as a REFOC element, and the final J res spectrum only shows a doublet along F 1 due to J HAHB at the chemical shift of spin B in F 2 .…”

How to face the low intrinsic sensitivity of 2D heteronuclear NMR with fast repetition techniques: go faster to go higher!

“…In the field of investigating silylated compounds, it was proposed to expand the family of fast repetition techniques by showing the potential of the 2D 1 H– 29 Si IMPACT HMBC (see Fig. A).…”

“…Among possible solutions, the 1 H–X IMPACT HMBC allowed the detection of N … H―N H bonds. The dipeptide 4 was studied to show the robustness of this method (Fig.…”