DINUCLEAR GOLD(I) AND SILVER(I) COMPLEXES WITH BRIDGING PHOSPHINES CONTAINING AN IMIDAZOLE RING
Fiorella Bachechi1, Alfredo Burini2, Rossana Galassi2, Bianca Rosa Pietroni2.
1Istituto di Strutturistica Chimica,
C.N.R., Area della Ricerca di Roma, C.P. 10, 00016 Monterotondo
St. (Roma), Italy.
2Dipartimento di Scienze Chimiche,
Universita di Camerino, 62032 Camerino, Italy.
Keywords: gold complexes, silver complexes, imidazole
complexes, crystal structures
A phosphine containing an imidazole ring was used to obtain
dimeric derivatives of gold(I) and silver(I). The ligand
(1-benzyl-2-imidazolyl)diphenylphosphine, (BzIm)Ph2P,
can act as a monodentate or bidentate ligand with P and N as
donor atoms, giving mononuclear o binuclear gold(I) complexes.
Analogous dinuclear silver(I) derivatives were obtain reacting
the ligand with AgX salts, were X is a weakly coordinated anion
as BF4- or NO3- . The
eight memebered ring, that forms in the dimeric compounds, is
quite flexible and can assume different conformations according
to the coordination properties of the metals. Thus in the crystal
structure of [BzImPh2PAg]2 [NO3]2
two independent molecules of the cationic dimeric complex coexist
with different conformations. The non-linear coordination
geometry of silver atoms in the P-Ag-N fragments imposes
different folds along the Ag….Ag axis of the binuclear complex.
The variable coordination mode of Ag(I) is accentuated by the
different mode of interaction of each of the silver atoms with
the oxigens of the nitrate anions. In some cases the nitrate
anions act as bidentate asymmetrical ligands, in some other as
bridging groups between two binuclear complexes. Thus, rows of
tetrameric aggregates alternate with rows of dimeric units in the
crystal packing.