CoRh(CO)7 (3) was prepared by the reaction of Na[Co(CO)4] with [Rh(CO)2Cl]2 under a continuous purge of carbon monoxide at -78 °C or by the treatment of Co2Rh2(CO)12 (4) with 2.5 bar of CO at 0 °C. The CoRh(CO)7 formula for 3 was established on the basis of its decomposition with Br2/CH2C12 and I2/pyridine followed by atomic emission analysis of the metals and freezing point molecular weight determination under carbon monoxide pressure. Its yellow crystals or its n-hexane solutions are stable only below -65 °C under N2. Under carbon monoxide the existence of two pseudoequilibria is observed: between CoRh(CO)7 (3) and Co2Rh2(CO)12 (4) (-65 °C < T < 15 °C and 0 < pco < 2.5 bar) and between CoRh(CO)7 (3) and CoRh(CO)8 (5) (T = 0 °C and 130 < pco < 160 bar), respectively. At room temperature and under 10 bar of CO pressure 3 disproportionates very slowly to Co2(CO)8 (1) and Rh4(CO)12 (2).
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry