Synthesis, chemical characterisation and molecular structure of [Ag-3{mu(3)-Fe(CO)(4)}(dppm)(3)][NO3] and [Au-3{mu-Fe(CO)(4)}(dppm)(2)][Cl]

The reaction of Na-2[Fe(CO)(4)]. xTHF with Ag-2(dppm)(2)(NO3), and Au-2(dpp m)(2)Cl-2, respectively affords the new [Ag-3{mu(3)-Fe(CO)(4)} (dppm)(3)][N O3] and [Au-3{mu-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 th e Fe(CO), unit is triply bridging in [Ag-3 {mu(3)-Fe(CO)(4)}(dppm)(3)](+) a nd doubly bridging in [Au-3{mu-Fe(CO)(4)} (dppm)(2)][Cl]. The [Ag-3{mu(3)-F e(CO)(4)}(dppm)(3)](+) cation has also been obtained from degradation of [A g-13{mu(3)-Fe(CO)(4)}(8)](3-) with dppm. However, this preparation is less convenient owing to concomitant formation of iron carbonyl anions as side-p roducts. (C) 1999 Elsevier Science S.A. All rights reserved.