Highly Reduced Ruthenium Carbide Carbonyl Clusters: Synthesis, Molecular Structure, Reactivity, Electrochemistry, and Computational Investigation of [Ru 6 C(CO) 15 ] 4 .

The reaction of [Ru 6 C(CO) 16 ] 2- ( 1 ) with NaOH in DMSO resulted in the formation of a highly reduced [Ru 6 C(CO) 15 ] 4- ( 2 ), which was readily protonated by acids, such as HBF 4 ·Et 2 O, to [HRu 6 C(CO) 15 ] 3- ( 3 ). Oxidation of 2 with [Cp 2 Fe][PF 6 ] or [C 7 H 7 ][BF 4 ] in CH 3 CN resulted in [Ru 6 C(CO) 15 (CH 3 CN)] 2- ( 5 ), which was quantitatively converted into 1 after exposure to CO atmosphere. The reaction of 2 with a mild methylating agent such as CH 3, I afforded the purported [Ru 6 C(CO) 14 (COCH 3 )] 3- ( 6 ). By employing a stronger reagent, that is, CF 3 SO 3 CH 3 , a mixture of [HRu 6 C(CO) 16 ] - ( 4 ), [H 3 Ru 6 C(CO) 15 ] - ( 7 ), and [Ru 6 C(CO) 15 (CH 3 CNCH 3 )] - ( 8 ) was obtained. The molecular structures of 2-5 , 7 , and 8 were determined by single-crystal X-ray diffraction as their [NEt 4 ] 4 [ 2 ]·CH 3 CN, [NEt 4 ] 3 [ 3 ], [NEt 4 ][ 4 ], [NEt 4 ] 2 [ 5 ], [NEt 4 ][ 7 ], and [NEt 4 ][ 8 ]·solv salts. The carbyne-carbide cluster 6 was partially characterized by IR spectroscopy and ESI-MS, and its structure was computationally predicted using DFT methods. The redox behavior of 2 and 3 was investigated by electrochemical and IR spectroelectrochemical methods. Computational studies were performed in order to unravel structural and thermodynamic aspects of these octahedral Ru-carbide carbonyl clusters displaying miscellaneous ligands and charges in comparison with related iron derivatives.