Applications of Pulsed Field Gradient Spin−Echo Measurements to the Determination of Molecular Diffusion (and Thus Size) in Organometallic Chemistry

Abstract

Pulsed field gradient spin-echo (PGSE) measurements on (a) four arsine complexes of Pd(II), PdCl 2 L 2 (L ) AsMe x Ph 3-x (x ) 3-0)), (b) three different ferrocene phosphine dendrimers, and (c) a selection of other organometallic complexes of differing molecular weight, are demonstrated to provide a practical alternative to classical methods used in organometallic chemistry for estimating molecular size. PGSE measurements make use of translational and not rotational properties of molecules and will be especially valuable where one cannot isolate an unknown complex and/or where a side product is of especial interest, since one can measure several components of the mixture simultaneously.

PGSE NMR Diffusion Overhauser Studies on [Ru(Cp*)(η6‐arene)][PF6], Plus a Variety of Transition‐Metal, Inorganic, and Organic Salts: An Overview of Ion Pairing in Dichloromethane

“…Molecular weight (more properly molecular volume) will play a role, but this cannot be the only component, since the ratio (0.86) for the Ru-bis(phosphine) 6 [47] (cation weight = 618) is similar to that (0.80) for the ammonium salt 17 [48] (cation weight = 366). Table 2, again suggesting no major effect of oxidation state.…”

“…The structure of the TMEDA salt 8 a (D c /D a ratio = 0.93), with its two partially positively charged ammonium-like N atoms concentrates the positive charge near the metal, and the relatively small chelating TMEDA ligand will allow the anion to approach. The bis-phosphine 6 [47] (D c /D a ratio = 0.86), with its longer chains and modestly bulky PnBu 3 ligands will keep the anion a little further away from the positive P atoms. Indeed the HOESY spectrum for 6, see Figure 4 (left), reveals only a weak contact to the PCH 2 group, but shows strong contacts to the remaining three aliphatic resonances.…”

Cationic Gold(I) Phosphanyl Thiolates: Aurophilic Interactions in the Solid State and in Solution

“…(2) Valentini et al [13] used DOSY measurements to determine the diffusion coefficients of some iron and palladium compounds, whose structures in the solid state were known. They obtained the hydrodynamic radii by using the StokesEinstein equation and compared these results to the radii of greatest steric hindrance obtained from crystallographic parameters, r R (rotating the molecule around its geometric centre), and they found very good consistency.…”

Characterization of Titanium Dioxide Nanoparticles Dispersed in Organic Ligand Solutions by Using a Diffusion‐Ordered Spectroscopy‐Based Strategy

“…Keywords: diffusion · ligand effects · nanostructures · NMR spectroscopy · titanium dioxide components of the mixture are separated chemically rather than spectroscopically. It is likewise of major interest for mixtures of soluble or dispersible compounds (surfactants), [4] and products with reduced translational mobility (dendrimers, [5] polymers, [6] and macromolecules [7] ) whenever species of different sizes or molar masses are to be distinguished. [8] Another advantage of this methodology is its potential to investigate interactions between various species in solution and to gain insight into their mutual clustering (for example, organic tin-oxide based clusters) as well as their affinity to the solvent.…”