title: Mono- and dinuclear Ag(I), Au(I), and Au(III) metallamacrocycles containing N-heterocyclic dicarbene ligands.
abstract: Ag(I) dicarbene complexes [Ag(m)(L(n))m]X(m) (L(n) = Im(Me)(CH2)(n)Im(Me), Im(Me) = N-methylimidazol-N-yl-2-ylidene; n = 3, X = PF6, m = 2; n = 6-8, 10, X = AgBr2, m = 1, 2) were prepared by reacting Ag2O with 1 equiv of the corresponding bisimidazolium salt [H2L(n)]A2 (A = PF6, Br). The dibromoargentates react with 1 equiv of AgTfO to afford [Ag(m)(L(n))m](TfO)m (m = 1, 2). The room temperature transmetalation reaction of [Ag(m)(L(n))m][AgBr2]m (n = 3, 5, 6-8, 10) with [AuCl(SMe2)] and AgTfO (L(n):Au:TfO = 1:1:1) affords [Au2(μ-L(n))2](TfO)2 (n = 3, 5, 10), or mixtures of [Au(κ(2)-L(n))]TfO (main product for n = 7) and [Au2(μ-L(n))2](TfO)2 (main product for n = 6, 8). At room temperature, the equilibrium between [M2(μ-L(n))2](TfO)2 and [M(κ(2)-L(n))]TfO is fast for M = Ag, but slow for M = Au, in the NMR time scale. When n ≥ 7 and M = Ag or Au, the equilibrium is shifted toward the mononuclear complexes in the order 8 > 10 > 7, which proves that the (CH2)8 linker has the optimal length for trans chelation. Correspondingly, the high-temperature metalation of [H2L(n)]Br2 (n = 8, 10) with 1 equiv of [AuCl(SMe2)] and excess of NaAcO, affords [Au(κ(2)-L(n))]Br with a small amount of [Au2(μ-L(n))2]Br2. If AgTfO is added to the reaction mixture, [Au(κ(2)-L(8))]2[AgBr3] is isolated instead of the desired triflate, which can be obtained by reacting the mixture of [Au(κ(2)-L(8))]Br and [Au2(μ-L(8))2]Br2 with AgTfO. [Au(κ(2)-L(10))]TfO was isolated after thermal conversion of [Au2(μ-L(10))2](TfO)2. [Au(κ(2)-L(8))]TfO reacts with I2 to give trans-[AuI2(κ(2)-L(8))]TfO, which is the first Au(III) complex containing a trans-spanning bidentate ligand. We have determined the crystal structures of complexes [Ag2(μ-L(3))2](PF6)2, [Ag(κ(2)-L(7))]TfO, [Au2(μ-L(3))2](TfO)2, [Au(κ(2)-L(8))]Br, [Au(κ(2)-L(8))]2[AgBr3], and trans-[AuI2(κ(2)-L(8))]TfO.
authors.affiliation: Grupo de Química Organometálica, Departamento de Química Inorgánica, Facultad de Química, Universidad de Murcia, E-30071 Murcia, Spain. jgr@um.es
authors.forename: Juan
authors.initials: J
authors.lastname: Gil-Rubio
authors.forename: Verónica
authors.initials: V
authors.lastname: Cámara
authors.forename: Delia
authors.initials: D
authors.lastname: Bautista
authors.forename: José
authors.initials: J
authors.lastname: Vicente