Synthesis of intermediates in the C–H activation of acetone with 2-phenylazophenylgold(III) complexes and in the C–C coupling of aryl groups from diarylgold(III) complexes. Crystal and molecular structures of [Au{C6H3(NNC6H4Me-4′)-2-Me-5}(acac-C)Cl](acac = acetylacetonate), cis-[Au(C6H4NNPh-2)Cl2(PPh3)], and [Au(C6H4CH2NMe2-2)(C6F5)Cl]

Abstract

The complex [[graphic omitted]Ph-2)Cl₂] reacts with [HgR₂](R = C₆H₄NO₂-2 or C₆F₅) and NMe₄Cl (2 : 1 : 2) to give [[graphic omitted]Ph-2)(R)Cl][R = C₆H₄NO₂-2, (1); or C₆F₅(2)]. Similarly, [[graphic omitted])Cl₂](3)[C–N = C₆H₃(NNC₆H₄Me-4′)-2-Me-5], prepared by the reaction of [AuCl₃(tht)](tht = tetrahydrothiophene) with [Hg(C–N)Cl] and NMe₄Cl (1 : 1 : 1), reacts with Tl(acac)(Hacac =acetylacetone)(1 : 1) to give [[graphic omitted])(acac-C)Cl](4). Reaction of (2) with PPh₃(1 : 1) leads to [[graphic omitted]Ph-2)(C₆F₅)Cl(PPh₃)](5), which upon standing in dichloromethane solution decomposes to give a mixture of [Au(C₆F₅)(PPh₃)], C₆H₄C₆F₅-1 -NNPh-2, and [Au(C₆H₄NNPh-2)Cl₂(PPh₃)](6). Crystal structures were determined for complexes (4), (6), and [[graphic omitted]Me₂-2)(C₆F₅)Cl](7)[(4), space group P, a= 9.475(4), b= 9.923(4), c= 10.913(4)Å, α= 63.75(3), β= 84.92(3), γ= 89.41 (3)°, Z= 2, R= 0.020 for 3 057 reflections at –95 °C; (6), space group P2₁/n, a= 10.361(3), b= 28.194(8), c= 10.724(4)Å, β= 116.26(2)°, Z= 4, R= 0.038 for 3 734 reflections at 20 °C; (7), space group Pbca, a= 11.996(4), b= 14.484(4), c= 18.310(7)Å, Z= 8, R= 0.045 for 1 909 reflections at 20 °C]. The three structures reveal neutral molecules with square-planar geometry around the gold atom. In complexes (4) and (7) the aryl groups act as chelating ligands, forming a five-membered ring [(4), Au–C 2.026(4), Au–N 2.158(3)Å; (7), Au–C 2.022(10), Au–N 2.128(10), Au–C₆F₅ 2.012(11)Å] while in complex (6) the aryl group acts as a monodentate ligand [Au–C 2.033(5)Å]. The chloro ligand in complex (4) is trans to the carbon atom of the aryl ligand [Au–Cl 2.349(2)Å], and the acac ligand is C-bonded to the gold atom [Au–C 2.083(4)Å]. This is one of the few isolated acetylacetonatogold(III) complexes and the first structurally characterized. In complex (6), chloro atoms are mutually cis[Au–Cl (trans to C) 2.377(2), (trans to N) 2.325(2)Å]. The chloro ligand in complex (7) is trans to the aryl group of the chelating ligand [Au–Cl 2.347(3)Å]. The isolation of complexes (1) and (2) and the observed geometry of (4) support the pathway suggested for the C–H activation of acetone with 2-phenylazophenylgold(III) complexes.