| Abstract |
The single compartmental Schiff base N,N -ethylenebis(salicylaldimine) (H2L) and [SnPh2Cl2] were utilized to synthesize heterobimetallic 3d metal-Sn complexes, the (CoSnIV)-Sn-III compound [\SnPhCl2\(1 kappa(ON2)-N-2,2 kappa O-2-mu-L)(mu-OMe)\CoPh\] (1), the (NiSnIV)-Sn-II compound [\SnPh2Cl2\(1 kappa(ON2)-N-2,2 kappa O-2-mu-L)Ni] (2) and the (CuSnIV)-Sn-II compound [\SnPh2Cl2\(1 kappa(ON2)-N-2,2 kappa O-2-mu-L)Cu] (3). Attempting to prepare the ethoxido bridged compound analogous to 1 (in ethanol) gives the phenylcobalt(III) complex [Co(kappa(ON2)-N-2) Ph(H2O)] (1A). Single crystal X-ray structure analyses reveal that 1 is derived from an intermetallic (Sn to Co) phenyl shift and that 1A is a transmetallated product; in compounds 2 and 3, the phenyl groups remain coordinated to Sn-IV but one of the pi rings interacts with the 3d-metal. Thus, while systems 1 and 1A show the lability of the phenyl ligand, 2 and 3 reveal its flexible nature. Theoretical DFT calculations demonstrate that the conceivable Ph group shift occurs in the oxidized Co-III intermediate [\(SnPh2Cl2)-Ph-IV\(kappa O2N2-mu-L)\Co-III(MeO)\] (5) rather than in the corresponding Co-II species [\(SnPh2Cl2)-Ph-IV\(kappa(ON2)-N-2-mu-L)\Co-II(MeOH)\] (4). Their catalytic studies in the Baeyer-Villiger oxidation of cyclohexanone into e-caprolactone with two different oxidants reveal that the sacrificial aldehyde method (with dioxygen/benzaldehyde) is better than that with aqueous H2O2 (30\%). The effects of various reaction parameters such as solvent, catalyst amount, temperature, time and heating method were studied allowing the achievement of yields up to 83\% with 89\% selectivity. |
