Studies of phosphorus(III) ligands and their complexes of nickel(II), palladium(II), and platinum(II) immobilized on insoluble supports by high-resolution solid-state phosphorus-31 NMR using magic-angle spinning techniques

Abstract

High-power proton decoupling, cross-polarization, and magic-angle spinning techniques have been employed to obtain high-resolution 31 3P NMR spectra of solid tertiary phosphines, tertiary phosphine oxides, and tertiary phosphine complexes of nickel(II), palladium(II), and platinum(II). Solid-state effects can result in nonequivalence of 31P shieldings in simple di-[PtCl2(PR3)2] complexes. The magnitudes of the scalar couplings, V(195Pt,31P), in platinum(II) complexes are comparable with those obtained by high-resolution solution 31P NMR measurements, allowing the geometry of such complexes to be determined in the solid state. The ligand Ph2PCH2CH2Si(OEt}3 and its Ni(II), Pd(II), and Pt(II) complexes have been immobilized on silica gel and high-surface-area glass beads and the immobilized species studied by solid-state 31P NMR. The results show that the geometry of surface-immobilized complexes may be determined and the surface reactions may be monitored. The merits of some preparative routes to supported transition-metal catalysts have been studied and some common representations of surface reactions and surface-immobilized species shown to be misleading.

Phosphorus-31 solid-state nuclear magnetic resonance study of monophosphazenes

“…While the chemical shielding anisotropy varies little in this series, it is only 70% of that observed for P h 3 M in the solid state (32)(33)(34) a) and 3 (b). Note that the relative intensities of the components of the asymmetric doublet in 3 appear to be reversed compared to 2 and the other monophosphazenes examined in the present study.…”

“…In all cases, the most shielded component of the chemical shift tensor, S33, was found to lie along the P=N bond. This indicates that the phosphorus nucleus is most shielded when the P=N bond axis is parallel to the applied magnetic field, Bo, a result in accord with other R3P=X systems, where X = 0 , S , and Se (32)(33)(34). However, the asymmetry in the shielding, q, is substantially greater for 1-4, as would be expected for an asymmetric substituent like X = N-Ph.…”

Single Site Supported Cationic Rhodium(I) Complexes for the Selective Redox Isomerization of Allylic Alcohols

“…It features as et of relativelym inor spinnings idebands, spaced by the magic-angle spinning (MAS)f requency.T he centerbandr evealed three components, markedb yt he dotted lines in the zoomed spectrumi nF igure 4b.T he two main peaks around2 8a nd 21 ppm stem from complex 3 and are tentatively assigned to each of the Pa toms showni nS cheme1.T he widths of the relatively broad 31 PNMR peaks are primarily dictated by structural disorder,a nd unresolved scalar couplings to 103 Rh. Besides am inor 31 PNMR peak at about 42 ppm, attributed to an oxidation product impurity (such NMR signals appear typically above 40 ppm [38,39] ), the absence of additional resonances reflects ap ure sample of complex 3.T he NMR spectrum reveals no traces of residual MeO-TPPMS (1b), which were observed to generate as harp 31 PNMR peak at À10 ppm (data not shown).…”

New Silica‐Immobilized Nickel Catalysts for Cyclotrimerizations of Acetylenes

“…More detailed studies and signal assignments will be a subject of future investigations. However, this result is in accord, for example, with the finding of Fyfes group [58] for the analogous complex [(EtO) 3 SiCH 2 CH 2 PPh 2 ] 2 NiCl 2 , which was reported not to give a 31 P NMR signal at room temperature. Obviously, these complexes are tetrahedral, although some other dichloronickel complexes with diarylalkylphosphine ligands that we and others have investigated so far, [19,59] including 15 (see below) are planar and diamagnetic, and they give 31 P and 13 C CP/MAS signals with small halfwidths.…”