Group 11 complexes with the bis(3,5-dimethylpyrazol-1-yl) methane ligand. How secondary bonds can influence the coordination environment of Ag(I): the role of coordinated water in [Ag-2(mu-L)(2)(OH2)(2)](OTf)(2)

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 [Ag-2(mu-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 [Au-2(C6F5)(2)(mu-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 Ag-2 framework.