Metal–Arene Interactions in Dialkylbiarylphosphane Complexes of Copper, Silver, and Gold

Abstract

Dialkylbiphenylphosphane-Au(I) complexes exhibit only weak metal-arene interactions with the covering arene ring. However, the contacts in isoleptic Ag(I) and Cu(I) complexes are shorter than the limiting values of 3.03 A (Ag(I)) and 2.83 A (Cu(I)). Strong metal-arene interactions were also found in the two Ag(I) aquo complexes and in two acetonitrile--Cu(I) complexes with dialkylbiphenylphosphane ligands. Arene-Ag(I) complexes with these bulky phosphane ligands show the strongest Ag(I)--arene bonds known.

Catalytic stereoselective addition to alkynes. Borylation or silylation promoted by magnesia-supported iron oxide and cis-diboronation or silaboration by supported platinum nanoparticles

“…Selected distances for Ag-η 2 -toluene C(21) and C(22), Ag-P, Ag-(C7)ipso and shortest distance between Ag and the closest carbon atom (C8) of distal phenyl ring are 2.367(6) and 2.480(6), 2.3873 (14), 2.906 and 2.838 Å, respectively. The structure of 7 was coincident with the previous reported structure for this complex 7 [3] with η 2 -arene coordination of toluene to Ag I . Complex 7 was also characterized by NMR spectroscopy and combustion elemental analysis (see experimental section and Figs.…”

“…[1] The interest in silver (I) catalysts stems from its possible coordination modes [2] and its affinity for hard donor atoms such as nitrogen or oxygen. [3] The instable, low-activity and easily decomposed AgI, [4] Ag2CO3, [5] AgSbF6 [6] and AgOTf salts [7] are used as Lewis acids and as sacrificial agents in some procedures for the preparations of gold (I) complexes. [8] In this context, it is important to establish whether or not stable Ag I complexes can exhibit good catalytic activity with respect to their silver salt precursors for certain reactions.…”

“…These data have made possible to draw some important conclusions respect the stability of these complexes and the lability of the aquo-, N-and organosulfonate ligands. bulky 2-di-tert-butylphosphanylbiphenyl (L = 2) and phenylacetylene (3) as ligand and reagent were dissolved in non-dried CH2Cl2 at RT for 24 h with the following stoichiometric proportion (1:1:2) (Scheme 1, Top). Filtration of the resulting transparent, colourless solutions followed by addition of nhexane at -8 ºC leads to the formation of a mixture of white precipitate and colourless needles crystals (see the Experimental Section) that could be isolated by filtration.…”

“…The structure obtained was a polymorph of a previously reported one for complex 4. [3] Another additional unsuccessful experiment aimed to isolate the silver (I) acetylide complex (6) (Scheme 2, top) was performed by starting from the same conditions of the first experiment (Scheme 1), but using in this case dried CH2Cl2. The addition of n-hexane over the resulting transparent colourless solution followed by standing over night at -30 ºC did not lead to the isolation of any solid product.…”

“…S21-S23 in the supporting information). It should be noted, however, that the reaction took place in only few minutes (6 min) at room temperature (26 ºC) for Ag (I) complexes 7, 10 and 11 (Table 1, entries 1, 2 and 3), compared to the slightly higher reaction temperature (50 ºC) and time (12 min) One important conclusion from Table 1 (entries [1][2][3][4][5][6] is that the cationic Ag I complexes were more active than the Cu I complexes and considerably more active than the Au I complex. This higher activity of Ag I and Cu I vs Au I can be explained by the lack of formation of di-cationic σ, π-disilver-(scheme 2: Top) or dicopper- [14] phenylacetylene adduct analogous to the fluxional…”