Resonance Raman, X-ray crystallographic, and magnetic susceptibility studies of metal-metal-bonded MoRu and WOs porphyrin dimers. 1. Evidence for an unusual MO diagram

Solution (VT NMR, Evans method magnetic susceptibility, resonance Raman) an d solid-state (SQUID magnetic susceptibility, X-ray crystallography) spectr oscopic studies of intertriad heterodimeric [(OEP)MoRu(OEP)] (1), [(OEP)WOs (OEP)] (2), and [(OEP)MoRu(TPP)]PF6 (3(+)) metalloporphyrins are reported ( OEP = 2,3,7,8,12,13,17,18-octaethylporphyrinato; TPP = 5,10,1 5,20-tetraphe nylporphyrinato). Solution and solid-state magnetic susceptibility data ind icate that 1 and 2 contain two unpaired electrons in the ground electronic configuration. The presence of a delta bond in 3(+) has been confirmed by s tructural characterization: The experimental evidence is consistent with a molecular orbital ordering, sigma < pi < delta < pi* < delta*, which is dif ferent from that seen for homologous metalloporphyrin dimers with homometal lic or intratriad heterometallic multiple metal-metal bonds. Resonance Rama n data suggest that the heterometallic bonds are slightly stronger than iso electronic homometallic species.