Silicon-29-nitrogen-15 spin-spin coupling constants in silazanes

Aggregation and Solvation of Sodium Hexamethyldisilazide: Across the Solvent Spectrum

“…Figure illustrates coupling that played an unexpectedly important role in the study. In the 1980s, Lukevics and co-workers reported 15 N– 29 Si coupling constants for various disilazanes and several salts . Without the benefits of additional data, they attributed the 7.8 Hz 15 N– 29 Si coupling for NaHMDS in benzene to a ligand-free tetramer, which we are now confident is the benzene-solvated dimer.…”

“…Its solubility, stability, and commercial availability appeal to synthetic chemists and render NaHMDS an attractive target for studying aggregation and solvation. Aside from NaHMDS crystal structures of potential interest to synthetic chemists (Chart ), there are remarkably few physicochemical studies of NaHMDS in solution. ,− Even the computational community has shown little interest …”

A new X-ray crystal structure (100 K) of Yb[N(SiMe 3 ) 2 ] 2 [Me 2 PCH 2 CH 2 PMe 2 ]

“…The 13 C{ 1 H} NMR spectra follow a similar pattern as a function of temperature; at 26°C the spectrum shows the same resonances previously reported; at higher field (150.9 MHz) the 1 J C-Si coupling constant of 52.2 Hz is observed, this and related spectra are available as SI. The average value of the 1 J C-Si in Yb[N(SiMe 3 ) 2 ] 2 (dmpe) at 25°C lies between the value of 56.2 Hz in HN(SiMe 3 ) 2 [11] and 51.9 Hz in NaN(SiMe 3 ) 2 [12]. The small change is consistent with loss of electron density in the Si b C c rbond, since the coupling constant is determined by the Fermi contact interaction and therefore the polarization of the s-orbital density in the Si b C c r-bond [12,13].…”

“…The average value of the 1 J C-Si in Yb[N(SiMe 3 ) 2 ] 2 (dmpe) at 25°C lies between the value of 56.2 Hz in HN(SiMe 3 ) 2 [11] and 51.9 Hz in NaN(SiMe 3 ) 2 [12]. The small change is consistent with loss of electron density in the Si b C c rbond, since the coupling constant is determined by the Fermi contact interaction and therefore the polarization of the s-orbital density in the Si b C c r-bond [12,13]. By À90°C, the PCH 2 resonance is broadened but no other changes are visible.…”

Analysis of isotope effects in NMR one-bond indirect nuclear spin–spin coupling constants in terms of localized molecular orbitals

“…However, the same phenomenon for the indirect spin-spin coupling constants (SSCC) has not been studied in such detail and many aspects remain still unknown. Isotope effects on the SSCC were pioneered by Jameson et al, 1,2 Lukevics and co-workers, 3,4 Sergeyev et al [5][6][7][8][9][10][11][12] and Raynes et al [10][11][12][13][14][15][16][17][18][19][20][21][22] More recently Limbach et al, 23 and Schilf et al 24 have also contributed to the unravelling of the physics behind them.…”