691410-59-0Relevant articles and documents
Synthesis, characterization and reactivity of heterobimetallic complexes (η5-C5R5)Ru(CO)(μ-dppm)M(CO)2 (η5-C5H5) (R = H, CH3; M = Mo, W). Interconversion of hydrogen/carbon dioxide and formic acid by these complexes
Man, Man Lok,Zhou, Zhongyuan,Ng, Siu Man,Lau, Chak Po
, p. 3727 - 3735 (2003)
The heterobimetallic complexes [(η5-C5R5)Ru(CO)(μ-dppm) M(CO)2(η5-C5H5)] (M = Mo, W; R = H, CH3) (1-4) are prepared by metathetical reactions between (η5-C5R5)Ru(dppm)Cl and Na+[(η5-C5H5) M(CO)3]-. IR spectroscopic and X-ray structural studies show that each of these complexes contains a semi-bridging carbonyl ligand. The low activity of these complexes in catalytic CO2 hydrogenation to formic acid might be attributed to their non-facile reactions with H2 to yield the active dihydride species. The metal-metal bonds can be protonated to form the cationic complexes, which contain strong Ru-H-M bridges. The bridging hydrogen atom is weakly acidic since it can be removed by a strong base, and it protonates BPh4- to give BPh3 and benzene. It also reacts with the hydridic hydrogen of Et3SiH to yield H2. The bridging hydrogen, however, cannot be removed by hydride scavengers such as Ph3C+OTf- and Me3Si+OTf-. The sluggishness of the catalytic formic acid decomposition by 1-4 is attributable to the stability of the protonated bimetallic intermediate [(η5-C5R5)Ru(CO)(μ-dppm)(μ-H) M(CO)2(η5-C5H5)]+ HCOO- formed during the catalysis.
