Iron Iridium Mixed-Metal Carbonyl Clusters .2. Synthesis and Chemical Behavior of the Tetranuclear complexes [FEIR3(CO)12]-, [FE2IR2(CO)12]2-, [FE2IR2H(CO)12]-, and [FE3IR(CO)13]-. Solid-State Structures of [N(PPH3)2][FEIR3(CO)12], [NET4]2[FE2IR2(CO)12], and [PPH4][FE2IR2(CO)12-(MU-3-AU(PPH3))]

The compound [Felr3(CO)12]- can be obtained by degradation of [Felr4(C0)l5]2- under a carbon monoxide atmosphere as well as by reduction of an equimolar mixture of [Fe(CO)5] and [Ir4(CO)12] in alcoholic NaOH under 1 atm of carbon monoxide. The molecular structure of the anion consists of a tetrahedron of metal atoms surrounded by twelve carbonyl groups: nine are terminally bound whereas three are bridging the edges of the Felr2 basal face. The dianion [Fe2lr2(C0)l2]2- was obtained by several different ways, the most selective being the condensation of [Fe2(CO)9] with [Ir(CO)4]-. The molecular structure of the dianion is based on a tetrahedral cluster of metal atoms and consists of an apical Ir(CO)3 group co-ordinated by three metal-metal bonds to a basal Fe2lr(CO)9 fragment containing two Fe(CO)2 units and one Ir(CO)2 group linked to each other by a metal-metal bond and bridging carbonyl groups.The salt [PPh4]2[Fe2lr2(CO)12] reacts with [Au(PPh3)CI] to give [PPh4][Fe2lr2(CO)12{m3-Au(PPh3)}]. The metal framework of the anion is a trigonal bipyramid with the Au(PPh3) moiety in one of the apical positions, the other being occupied by a Fe(CO)3 group. Each edge of the equatorial triangle, formed by one iron and two iridium atoms, is spanned by a bridging carbonyl ligand, and two terminal CO groups are attached to each metal of this triangle.