New Tetranuclear Ruthenium(I) Carbonyl Trifluoroacetate Complex: Gas-Phase Transformations and Coordination Reactions

Abstract

A new mixed ligand ruthenium(I) complex of the composition [Ru2(O2CCF3)2(CO)5] (1) has been prepared by refluxing Ru3(CO)12 with trifluoroacetic acid in a dichloromethane/benzene mixture. Crystals of 1 were obtained by gas phase sublimation of the crude product at 110°C. The X-ray diffraction study has revealed a tetranuclear `8dimer of dimers' 9 structure [Ru2(O2CCF3)2(CO)5]2 in 1. Complex 1 can be re-sublimed without decomposition at temperatures up to 130°C, while at higher temperatures fragmentation accompanied by a ligand re-distribution reaction has been observed. As a result, two new ruthenium(I) complexes have been isolated from the gas phase transformation of 1 at 160°C: [Ru2(O2CCF3)2(CO)6] (2) and [Ru2(O2CCF3)2(CO)4] (3). Complex 2 has a dinuclear cis-trifluoroacetato-bridged core, while 3 exhibits a polymeric structure built on axial Ru···O interactions of the dimetal units, [Ru2(O2CCF3)2(CO)4]∞. The above reaction suggests the possible gas phase dissociation of the tetranuclear molecule 1 to the dimetal fragments, [Ru2(O2CCF3)2(CO)5] that have one open axial coordination site. The latter was proved by codeposition of 1 with an aromatic hydrocarbon, [2. 2]paracyclophane, that afforded a new sandwich compound, [Ru2(O2CCF3)2(CO)5·(μ2-C16H16)·Ru2(O2CCF3)2(CO)5] (4), in which the ligand is entrapped between two dimetal complexes. In contrast, when 3 is codeposited with [2. 2]paracyclophane, a new 1D polymeric product, [Ru2(O2CCF3)2(CO)4·(μ2-C16H16)]∞ (5) has been isolated. Complexes 1–5 have been fully characterized by IR and NMR spectroscopy, as well as by X-ray diffraction.