Photochemical behavior of phosphorus ligands-substituted diamanganase carbonyls

Abstract Photochemistry of ax,ax-L(OC) 4 Mn-Mn(Co) 4 L (L=P(n-Bu) 3 ) (S) in cyclohexane has been studied by means of laser photolysis with a uv-vis detection system. In addition to the transient absorption features due to the occurrence of primary processes, (1) Mn-Mn bond cleavage to give (Mn(CO) 4 L (I), and 2) CO dissociation without metal-metal bond cleavage to give Mn 2 (CO) 7 L 2 (II). Two absorption features are observed: The one is attributed to the formation of a secondary intermediate (IV), whose structure is assigned to ax,eq-L(OC) 4 Mn-Mn(CO) 4 L, from the reaction of II with CO. The other appears to show the possibility of a third primary process (3) in the photolysis system of the disubstituted L(OC) 4 Mn-Mn(CO) 4 L. A whole photochemical reaction scheme is proposed in Scheme 2 and the nature of the intermediates, IV and unknown II is discussed.