¹H and ¹⁹F PGSE diffusion and HOESY NMR studies on cationic palladium (II) 1,3‐diphenylallyl complexes in THF solution

Abstract

THF solutions of the cationic chiral 1,3-diphenylallyl bidentate phosphine complexes [Pd(eta(3)-PhCHCHCHPh)(Duphos)](CF(3)SO(3)), Duphos = 1,2-Bis-((2R,5R)-2,5-dimethylphospholano)benzene), 2, and [Pd(eta(3)-PhCHCHCHPh)(P,S)]BF(4), 4, P,S = [8-((o-(diphenylphosphino)benzyl) thiomethyl]-(7,7'-dimethyl)-exo-norborneol, have been studied via pulsed gradient spin-echo (PGSE) diffusion, (1)H, (19)F HOESY and a variety of other multi-dimensional NMR methods. On the basis of the (1)H, (19)F HOESY data, the anions show a preference for a specific structural position with respect to the eta(3)-PhCHCHCHPh allyl ligand, i.e. the anion does not move evenly around the periphery of the cation. THF is shown to promote significant ion pairing, although neither 2 nor 4 shows 100% ion pairing.

Applications of NMR diffusion methods with emphasis on ion pairing in inorganic chemistry: a mini‐review

“…This may simply involve NH or OH containing molecules that H‐bond to one another or, for salts, the interaction of a suitable cation with polar solvents or anions . In the case of salts where the anion may contain a fluorine atom but no suitable proton, PGSE and DOSY studies reporting both 19 F and 1 H diffusion measurements have become increasingly popular.…”

Ion pairing using PGSE diffusion methods

“…On the other hand, in the CF 3 SO 3 À salt, the anion does show a contact to the methyl ligand (as well as the other selective contacts) and therefore can be near to or occupying a pseudo fifth coordination position on the side of the cation remote from the two benzyl groups. Even though one does not find complete ion pairing, there is, yet again [89,119,[122][123][124]141,142,158], a specific path of approach towards the cation. Possibly the larger size of the CF 3 SO 3 À and/or its stronger tendency to coordinate, places this anion in a slightly disadvantageous position with respect to the necessary olefin complexation which will, eventually, lead to the co-polymer.…”

Silver mediated duplex-type complexes of pyrimidinophanes and their acyclic counterparts

“…The IR absorption spectra were recorded in KBr pellets on a Vector-22 FT-IR spectrometer (Bruker) with a resolution of 4 cm À1 and 16 scan accumulation. The NMR spectra were detected on a Bruker AVANCE-600 spectrometer equipped with a gradient block (eld gradient to 50 g cm À1 ); working frequency of the spectrometer being 600.13 MHz in 1 H, 150.90 MHz in 13 C and 60.81 MHz in 15…”

“…14,15 In this connection, we have measured the self-diffusion coefficients (D s ) both for the solutions of free ligands (L1, L3, L4 and L5a,b) at various concentrations as well as for their complexes with Ag + Pic À ( Table 1). The investigated molecules have several coordination sites and typical NH proton-donor groups which are capable of generating associates even in polar solvents.…”

“…Currently, these methods are widely used for the investigation of a various kind of interactions, and make it possible, in particular, to learn how the cations and anions of transition metal salts interact in the solutions. 14,15 In this connection, we have measured the self-diffusion coefficients (D s ) both for the solutions of free ligands (L1, L3, L4 and L5a,b) at various concentrations as well as for their complexes with Ag + Pic À (Table 1). The complexes with higher molecular weights appeared to possess the lower D s -values.…”