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