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Synthesis of Molybdenum-Molybdenum Quadruple Bonds W
The concept of quadruple bonds formed between transition metal atoms is often not encountered until students are juniors or seniors, and it is rarely reinforced by laboratory experience, owing to a paucity of easily reproducible experiments at the advanced level. We describe an inorganic experiment that focuses on the formation of the quadruple bond and the substitution chemistry of the assembled dimetal unit for the relatively unfamiliar second-row transition element, molybdenum. The intense and varied colors of the products demonstrate the influence of tt-donor, o-donor, and it-acceptor ligands on the energies of the frontier molecular orbitals; shifts in orbital energies alter the wavelength of the 8-S* transition in the visible region. The experiment requires students to learn inert atmosphere techniques, but affordable methods are presented as alternatives to glove boxes and vacuum lines.
This multistep inorganic experiment is appropriate for an advanced synthetic or integrated laboratory course and is designed to include common aspects of industrial and academic working environments. By carrying out three sequential reactions in which the product of one reaction is the starting material for the next, students are introduced to the complex process of chemical research, which will ease the transition that they make from single-step introductory laboratory experiments to their postgraduate experiences. The molybdenum experiment also may be adapted for a team or "research group" of students who collaborate on...