Synthesis, chemical characterisation and molecular structure of [Ag3{μ3-Fe(CO)4}(dppm)3][NO 3] and [Au3{μ-Fe(CO)4}(dppm)2][Cl]1

The reaction of Na2[Fe(CO)4] · xTHF with Ag2(dppm)2(NO3)2 and Au2(dppm)2Cl2, respectively affords the new [Ag3{μ3-Fe(CO)4}(dppm)3][NO 3] and [Au3{μ-Fe(CO)4}(dppm)2][Cl] derivatives in high yields. These have been crystallised either from dichloromethane or THF by precipitation with hexane and an X-ray diffraction study has unambiguously shown that the Fe(CO)4 unit is triply bridging in [Ag3{μ3-Fe(CO)4}(dppm)3] + and doubly bridging in [Au3{μ-Fe(CO)4}(dppm)2][Cl]. The [Ag3{μ3-Fe(CO)4}(dppm)3] + cation has also been obtained from degradation of [Ag13{μ3-Fe(CO)4}8]3- with dppm. However, this preparation is less convenient owing to concomitant formation of iron carbonyl anions as side-products.