VII-H-8 Oxide Transfer Reaction from Carbonate to Metal-CO Complex, Affording Metal-(eta)¹-CO₂ Complex and Carbon Dioxide

Hiroshi NAKAJIMA, Kiyotsuna TOYOHARA, Kiyoshi TSUGE and Koji TANAKA

[Chem. Lett. 485 (1996)]

Much attention is being devoted to metal-(eta)¹-CO₂ complexes which are the key intermediate for CO₂/CO conversion. In protic media, CO₂/CO conversion on metals takes place through acid-base equilibria among [M-(eta)¹-CO₂]ⁿ⁺, [M-(eta)¹-C(O)OH]⁽ⁿ⁺¹⁾⁺ and [M-CO]⁽ⁿ⁺²⁾⁺ (eq 1). In the absence of proton donors, CO₂/CO conversion is achieved by oxide transfer between metal-CO₂ and CO₂ (eq 2), which may be more

useful than that in H₂O (eq 1) from the viepoint of utilizartion of CO₂ as C1 resources. Reversible oxide transfer reactions from CO₃^2- to [Ru(bpy)₂(CO)₂]²⁺ and from Ru(bpy)₂(CO)((eta)¹-CO₂) to CO₂ are established (Scheme 1). The oxide transfer reaction from CO₃^2- to [Ru(bpy)₂(CO)₂]²⁺ producing Ru(bpy)₂(CO)((eta)¹-CO₂) and CO₂ in CH₃CN is ascribed to the less basicity of the Ru-(eta)¹-CO₂ group compared with that of CO₃^2-. The reverse oxide transfer from Ru(bpy)₂(CO)((eta)¹-CO₂) to CO₂ affording [Ru(bpy)₂(CO)₂]²⁺ is assisted by Li⁺ due to low solubility of Li₂CO₃ in CH₃CN.

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