Cobalt a structural analog to ferrocene, with cobalt in place of iron. Cobaltocene is much more sensitive to oxidation than ferrocene. Cobalt carbonyl (Co(CO)) is a catalyst in carbonylation and hydrosilylation reactions. Vitamin B (see below) is an organometallic compound found in nature and is the only vitamin that contains a metal atom. An example of an alkylcobalt complex in the otherwise uncommon +4 oxidation state of cobalt is the homoleptic complex (Co(1-norb)), a transition metal-alkyl complex that is notable for its stability to β-hydrogen elimination. The cobalt(III) and cobalt(V) complexes [Li(THF)][Co(1-norb)] and [Co(1-norb)][BF] are also known. Co is the only
Chemical element For example, the formula for heavy water may be written DO instead of HO. Only about 4% of the total mass of the universe is made of atoms or ions, and thus represented by chemical elements. This fraction is about 15% of the total matter, with the remainder of the matter (85%) being dark matter. The nature of dark matter is unknown, but it is not composed of atoms of chemical elements because it contains no protons, neutrons, or electrons. (The remaining non-matter part of the mass of the universe is composed of the even more mysterious dark energy). The