Oxidative Addition of Small Molecules to a Dinuclear Au(I) Amidinate Complex, Au2[(2,6-Me2Ph)2N2CH]2. Syntheses and Characterization of Au(II) Amidinate Complexes Including One Which Possesses Au(II)−Oxygen Bonds

Abstract

The dinuclear Au(I) amidinate complex Au₂(2,6-Me₂Ph-form)₂ (1) is isolated in quantitative yield by the reaction of (THT)AuCl and the potassium salt of 2,6-Me₂Ph-form in a 1:1 stoichiometric ratio. Various reagents such as Cl₂, Br₂, I₂, CH₃I, and benzoyl peroxide add to the dinuclear Au(I)amidinate complex Au₂(2,6-Me₂Ph-form)₂ to form oxidative-addition Au(II) metal−metal-bonded complexes 2, 3, 4, 5, and 6. The Au(II) amidinate complexes are stable as solids at room temperature. The structures of the dinuclear Au₂(2,6-Me₂Ph-form)₂ and the Au(II) oxidative-addition products Au₂(2,6-Me₂Ph-form)₂X₂, X = Cl, Br, I, are reported. Crystalline products with an equal amount of oxidized and unoxidized complexes in the same unit cell, [Au₂(2,6-Me₂Ph-form)₂X₂][Au₂(2,6-Me₂Ph-form)₂], X = Cl, 2 m, or Br, 3 m, are isolated and their structures are presented. The structure of [Au₂(2,6-Me₂Ph-form)₂X₂][Au₂(2,6-Me₂Ph-form)₂], X = Cl has a Au(II)−Au(II) distance slightly longer, 0.05Å, than that observed in the fully oxidized product Au₂(2,6-Me₂-form)₂Cl₂, 2. The gold−gold distance in the dinuclear complex decreases upon oxidative addition with halogens from 2.7 to 2.5 Å, similar to observations made with the Au(I) dithiolates and ylides. The oxidative addition of benzoyl peroxide leads to the isolation of the first stable dinuclear Au(II) nitrogen complex possessing Au−O bonds, Au₂(2,6-Me₂Ph-form)₂(PhCOO)₂, 6, with the shortest Au−Au distance known for Au(II) amidinate complexes, 2.48 Å. The structure consists of unidentate benzoate units linked through oxygen to the Au(II) centers. The replacement of the bromide in 3 by chloride, and the benzoate groups in 6 by chloride or bromide also occurs readily. The unit cell dimensions are, for 1, a = 7.354(6) Å, b = 9.661(7) Å, c = 11.421(10) Å, α = 81.74(5)°, β = 71.23(5)°, and γ = 86.07(9)° (space group P1̄, Z = 1), for 2·1.5C ₆ H ₁₂, a = 11.012(2) Å, b = 18.464(4) Å, c = 19.467(4) Å, α = 90°, β = 94.86(3)°, and γ = 90° (space group P2₁/c, Z = 4), for 2m·ClCH ₂ CH ₂ Cl, a = 16.597(3) Å, b = 10.606(2) Å, c = 19.809(3) Å, α = 90°, β = 94.155(6)°, and γ = 90° (space group P2₁/n, Z = 2), for 3 m, a = 16.967(3) Å, b = 10.783(2) Å, c = 20.060(4) Å, α = 90°, β = 93.77(3)°, and γ = 90° (space group P2₁/n, Z = 2), for 4·THF, a = 8.0611(12) Å, b = 10.956(16) Å, c = 11.352(17) Å, α = 84.815(2)°, β = 78.352(2)°, and γ = 88.577(2)° (space group P1̄, Z = 1), for 5, a = 16.688 Å, b = 10.672(4) Å, c = 19.953(7) Å, α = 90.00 (6) °, β = 94.565(7)°, and γ = 90.00° (space group P2₁/n, Z = 4), for 6·0.5C ₇ H ₈, a = 11.160(3) Å, b = 12.112(3) Å, c = 12.364(3) Å, α = 115.168(4)°, β = 161.112(4)°, and γ = 106.253(5)° (space group P1̄, Z = 1).