$\ce{V(CO)6}$ is well known to be an unusual 17 valence electron, paramagnetic octahedral complex.
Do the corresponding tantalum and niobium species form simple dimers or more complicated structures ?
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Sign up to join this communityFrom the abstract of J. Chem. Theory Comput., 2011, 7, 2112-2125 (DOI) is seems that niobium forms a dinuclear $\ce{Nb2(CO)12}$ complex, in which two $\ce{Nb(CO)6}$ units are connected by a 340 pm $\ce{Nb-Nb}$ bond.