Tungsten to tungsten quadruple bonds: over 30 years of research, 50 structurally characterized compounds and 100 known compounds

Since the first reported structure of a quadruply bonded ditungsten complex in 1977, the field of W2(II, II) chemistry has expanded as new synthetic methodologies have been developed. Based on a recently developed synthetic route in our laboratory, the synthesis and structures of two new W2(II, II) complexes with substituted formamidinate ligands are reported. With the addition of these two new structures, the number of structurally characterized quadruply bonded W2(II, II) complexes exceeds 50 and over 100 W2(II, II) complexes have been synthesized. A compilation of the quadruply bonded W2(II, II) compounds, W–W bond distances, and synthetic methodologies is presented.