Magnetic Behavior of Odd- and Even-Electron Metal Carbonyl Clusters: The Case Study of [Co8Pt4C2(CO)24]n- (n=1, 2) Carbide Cluster

The reaction of [Co6C(CO)(15)](2-) with 2 equiv of PtCl2(Et2S)(2) affords the new heterobimetallic [Co8Pt4C2(CO)(24)](2-), [1](2-), carbonyl cluster. [1](2-) undergoes reversible chemical and electrochemical oxidation and reduction processes disclosing a complete series of [1](n-) (n = 1-4) clusters. The mono- and dianion of [1](n-) have been isolated as their tetra-substituted ammonium salts and fully characterized by means of IR, C-13 NMR, ESI-MS, and X-ray crystallography. Variable-temperature (VT) solid-state EPR studies on pure crystalline samples indicate that both [11](2-) and [1](-center dot) are paramagnetic, due to a doublet state of the latter and a triplet state of [1](2-). This conclusion is supported by SQUID measurements on the same crystalline sample of [1](2-). The present study indisputably demonstrates that even-electron transition metal carbonyl clusters (TMCC) can be magnetic.