REACTIVITY OF MOLECULES CONTAINING ELEMENT ELEMENT BONDS .2. TRANSITION-ELEMENTS

Exchange reactions between homodinuclear species to give the heterodinuclear complexes (Mn2(CO)10 + Re2(CO)10 reversible 2MnRe(CO)10; Mo2Cp2(CO)6 + W2Cp2(CO)6 reversible 2MoWCp2(CO)6) have been studied under different conditions (both thermally and photochemically). For the systems Mn2(CO)10/Re2(CO)10 and Mo2Cp2(CO)6/W2Cp2(CO)6 (the latter photochemically only), the reactions were found to reach an equilibrium value close to the statistical distribution. For the Mn2(CO)10/Re2(CO)10 system, a small enthalpy contribution, if any, was inferred from the equilibrium data measured as a function of temperature, both in solution (decahydronaphthalene) and in the melt. On the other hand Cr2Cp2(CO)6 reacts thermally with E2Ph4 (E = As, Sb, Bi) at room temperature to give the exchange product CrCp(CO)3-EPh2. The molybdenum and tungsten analogues, M2Cp2(CO)6, which did not react in the dark, exchange with Bi2Ph4 under exposure to normal laboratory daylight.