Cationic Dimetallic Gold Hydride Complex Stabilized by a Xantphos-Phosphole ligand: Synthesis, X-ray Crystal Structure, and Density Functional Theory Study

Abstract

The bis-2,5-diphenylphosphole xantphos ligand (XDPP) 1 reacts with the [AuCl(tht)] complex to afford the monocoordinated [Au(XDPP)Cl] 2 and the dicoordinated chelate species [Au(XDPP)Cl] 3. Addition of AgOTf on this mixture, at room temperature, affords the cationic [Au(XDPP)][OTf] complex 4 which was fully characterized. An X-ray crystal structure analysis confirms the bent structure of this 14 VE [ML(2)](+) complex. Reaction of 4 with HSiMe(2)Ph in tetrahydrofuran at -78 degrees C yields the dinuclear [(XDPP)Au-H-Au(XDPP)](+) cationic complex 5, in which the hydride bridges the two [Au(XDPP)](+) metal fragments. In 5, the Au-P bond lengths are different and the phosphorus atoms which are located nearly trans to the hydride ligand exhibit significantly shorter P-Au bond lengths. Reaction of 4 with DSiMe(2)Ph to form the [(XDPP)Au-D-Au(XDPP)](+) complex 6 allowed to unambiguously ascribe the chemical shift of the deuteride in (2)H NMR (delta = 7.0 ppm with a (2)J(DP) = 8.4 Hz. The electronic structure of the [(XDPP)Au-H-Au(XDPP)](+) complex was studied through density functional theory calculations. An orbital analysis is developed in which complex 5 is viewed as the combination of two 12 electrons fragments [Au(XDPP)](+) with H(-). This analysis reveals that the hydride interacts in a bonding way with the sigma MO between the two gold atoms and in an antibonding way with a combination of d orbitals at the metal centers. This simple description allows to rationalize the inequivalence of the two types of P-Au bonds in 5.

Mechanism of the Dehydrogenative Silylation of Alcohols Catalyzed by Cationic Gold Complexes: An Experimental and Theoretical Study

“…[12] Using this mixture of gold chloride complexes was not a suitable way to test the catalytic reaction. On the other hand, a single cationic complex, 3-BF 4 , was obtained from the mixture upon chloride abstraction by the silver salt AgBF 4 [Eq.…”

“…Nuclear magnetic resonance spectra were recorded on a Bruker AC-300 SY spectrometer operating at 300. [18] 2-OTf, [12] and 3-OTf [12] were prepared as reported previously. [AuClA C H T U N G T R E N N U N G (tht)] was prepared according to the established procedure.…”

“…(4)]. This thermal decomposition formed a mononuclear complex, 8, [12] as well as Au 0 particles (see Supporting Information). In parallel, the same complex was synthesized quantitatively by the stoichiometric addition of ligand 1 to 3-OTf (see Supporting Information).…”

“…Following previous work on the stabilization of unsaturated, low-valent transition-metal fragments using the widebite-angle, electron-accepting ligand XDPP (bis-2,5-diphenylphosphole xantphos 1), [11,18] in 2009 we isolated the first AuÀH complex featuring a phosphine ligand in the form of the Au 2 H + species, 2-OTf (Scheme 1). [12] The stability of this species is undoubtedly linked to our peculiar ligand, as it is known in the literature that the reaction of [(R 3 P)AuCl] complexes with stoichiometric amounts of hydride sources leads to the formation of Au clusters without observation of Au À H bonds, [13,14] and that an excess of hydride sources can lead to the formation of phosphine-stabilized Au nanoparticles. [15] As far as catalysis is concerned, Ito showed that only Au I chloride complexes, B (Scheme 1), featuring wide-biteangle ligands of the xantphos (xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) type, were efficient precatalysts for dehydrogenative silylation.…”

Applications of nuclear shielding

“…33 The 2 H NMR chemical shift of [(XDPP)Au-H-Au(XDPP)] þ complex (XDPP: bis-2,5-diphenylphosphole xantphos ligand) and the electronic structure of the [(XDPP)Au-H-Au(XDPP)] þ complex were studied through DFT calculations. 34 It was revealed that the hydride interacts in a bonding way with the s MO between the two Au atoms and in an antibonding way with a combination of d orbitals at the metal centres. 2 H, 1 H, 19 F and 15 N NMR spectra of CNHF-as an ion pair with a tetrabutylammonium cation dissolved in CDF 3 -CDF 2 Cl mixture were recorded in the slow exchange regime at temperatures down to 110 K and the fine structure due to spin-spin coupling of all nuclei involved in the hydrogen bridge was resolved.…”