Metallomacrocycles with metalmetal bonds: synthesis, characterization and electrochemistry of [(P)SnRe(CO) 5]BF 4 and [{(P)Sn} 2Re(CO) 4]BF 4 derivatives, where P = tetra- p-tolyporphyrin or tetra- m-tolylporphyrin

Abstract

The synthesis and characterization of bimetallic and trimetallic porphyrins of the type [(P)SnRe(CO) 5]BF 4 and [{(P)Sn} 2Re(CO) 4]BF 4 are reported where P is the dianion of tetra- p-tolyporphyrin (TpTP) or tetra- m-tolyporphyrin (TmTP). These metal-metal bonded complexes were synthesized by reaction of Re 2(CO) 10 with the corresponding (P)SnCl 2 derivatives in 1,2-dichlorobenzene followed by a reaction with NaBF 4 or TBABF 4 in toluene to give the BF − 4 salt. Each compound was characterized by a variety of spectroscopic and electrochemical techniques while the structures were assigned on the basis of FAB mass spectral data and by comparison of their physicochemical properties with data for related metalmetal bonded porphyrins previously synthesized in our laboratories. Each [(P)SnRe(CO) 5]BF 4 complex undergoes two reversible one-electron reductions at the porphyrin π-ring system while each [{(P)Sn} 2Re(CO) 4]BF 4 derivatives exhibits four reversible reductions in accordance with the presence of two Sn porphyrin units having interacting redox centers. These reductions also occur at the conjugated macrocycle. The first oxidation of each compound is irreversible and is associated with a cleavage of the tinrhenium bond.