Solid-state 31P NMR characterisation of phosphinine-stabilised gold nanoparticles and a phosphinine-gold complex

Abstract

Solid-State (31)P NMR studies reveal that phosphinine ligands employed for the stabilisation of gold nanoparticles react in part during the synthesis, and that the particles are stabilised by a mixture of intact phosphinine units together with several other surface-bound species. The spectral data of these species are characteristic for phosphine-type donors although unambiguous structure assignment was as yet unfeasible. The spectral data of surface-bound phosphinines were verified by comparison with the spectrum of an authentic complex [()AuCl]. The metal-bound phosphinines in both the complex and the nanoparticles prefer eta(1)(P)-coordination to a single metal atom, and the observation of splittings arising from coupling with (197)Au (I = 3/2) nuclei indicates that these ligands are not mobile. The fraction of intact phosphinines on the nanoparticles drops with decreasing steric protection although the observed product distribution shows no simple relation with substituent patterns.

Controlled metal nanostructures: Fertile ground for coordination chemists

“…Phosphines are used on e.g. Pd [101], [102], [103], Pt [104], [41], or Ru [105] NPs, diphosphites on Pd [106], [107], [108], as well as on Ru, Rh, or Ir [109] NPs or phosphine oxide on Co [110], indium [111] or Au ones [112], phosphinine ligands on Au NPs [113], and phosphonic acid on Cu NPs [114]. Care should be taken when phosphines or phosphine oxides are envisaged for the stabilization of MNPs.…”

“…This implies that surface diffusion kinetics is slow for thiols, as observed by Ionita et al in the case of smaller This correlates well with the lower strength of the Au-P bond in comparison to the Au-S one. Interestingly solid-state 31 P NMR characterization of phosphinine-stabilized Au NPs indicates that the ligand is coordinated via a  1 (P) coordination to a single metal atom mode and the observation of splitting arising from coupling with197 Au nuclei shows that the ligands are not mobile[113] Comparison of the binding behaviors of alkylthiols, phosphine and phosphinine ligands at the surface of Au NPs clearly indicates that, not only the nature of the atom binding to metal surface, but also its purified NPs. The dynamics of the amines at the metal surface is expected to lead to a temporary lack of ligands on the NPs surface and consequently, to favor the coalescence of the initially formed NPs into ones of elongated shape, as observed by TEM.…”

Cooperative Gold Nanoparticle Stabilization by Acetylenic Phosphaalkenes

“…(Hetero-)Ene-yne motifs tested for AuNP preparation and stabilization.P hosphaalkenes (1-3), acetylenicp hosphaalkenes(4-7), and all-carbon reference compounds(8)(9)(10)(11).…”

“…Structural integrity of the surface-bound phosphinines is however debated in view of as olid-state MAS-NMR spectroscopic study. [9] With our interest to explore low-valent phosphoruscontaining systems for molecular electronics applications, [10] we were intrigued by the possibility to use phosphaalkenes as conducting anchoring groups on Au surfaces.T he inherent instability of phosphaalkenes has presumably kept many researchers from using l 3 s 2 -phosphanes for these kinds of …”

“…Structural integrity of the surface-bound phosphinines is however debated in view of as olid-state MAS-NMR spectroscopic study. [9] With our interest to explore low-valent phosphoruscontaining systems for molecular electronics applications, [10] we were intrigued by the possibility to use phosphaalkenes as conducting anchoring groups on Au surfaces.T he inherent instability of phosphaalkenes has presumably kept many researchers from using l 3 s 2 -phosphanes for these kinds of purposes.T his obstacle is easily met through kinetic stabilization provided by P-bound Mes* groups (Mes* = 2,4,6-(tBu) 3 C 6 H 2 ). However,steric protection of the P = Cunit could also impede strong binding of the phosphorus center to the Au surface.T he present paper is the first report that shows that l 3 s 2 -phosphanes in the form of phosphaalkenes can stabilize AuNPs,a lbeit only when in conjunction with acetylenes.E xperimental observations,s pectroscopic data, and theoretical evidence are presented to show that both structural features of acetylenic phosphaalkenes,t hat is,t he P = Cand the C Cunits are required in acooperative fashion for AuNP stabilization.…”