The complexation properties of the ligand bis(3,5-dimethylpyrazol-1-yl)methane ( L) towards group 11 metals have been studied. The reaction in a 1 : 1 molar ratio with [Cu(NCMe)4]PF6 or Ag(OTf) complexes gives the mononuclear [CuL(NCMe)]PF6 ( 1), with crystallographic mirror symmetry, or dinuclear [Ag2(µ-L)2](OTf)2 ( 2) (OTf = trifluoromethanesulfonate) in which the ligand bridges both silver centres, an unprecedented mode of coordination for this type of ligands. Compound 2 crystallizes with two water molecules and forms a supramolecular structure through classical hydrogen bonding. The reaction in a 2 : 1 ratio affords in both cases the four-coordinated derivatives [ML2]X (M = Cu, X = PF6 ( 3); Ag, X = OTf ( 4)). The treatment of [Ag(OTf)(PPh3)] with the ligand L gives [AgL(PPh3)]OTf ( 5). The gold(I) derivative [Au2(C6F5)2(µ-L)] ( 6) has also been obtained by reaction of L with two equivalents of [Au(C6F5)(tht)]. These complexes present a luminescent behaviour at low temperature; the emissions being mainly intraligand but enhanced after coordination of the metal. Compounds 1–4 have been characterized by X-ray crystallography. DFT studies showed that, in the silver complex 2, coordination of H2O to Ag in the binuclear complex is favoured by formation of a hydrogen-bonding network, involving the triflato anion, and releasing enough energy to allow distortion of the Ag2 framework.

We thank the Ministerio de Educación y Ciencia (BQU2004- 05495-C02-01) for financial support. We thank the Acción Integrada HP20030147 and Acçâo Integrada E-31/04. P. J. C. acknowledges FCT for grant (SFRH/BD/10535/2002) and S. Quintal for grant (SFRH/BPD/11463/2002).

10 pages, 9 tables, 9 figures, 1 scheme.

Peer reviewed