Trimethylenemethane complexes

[1] The synthesis of cyclobutadieneiron tricarbonyl pointed to the possible existence of related complexes of elusive organic compounds.

Generally speaking, trimethylenemethane complexes are synthesized in the following four ways: (A) the dehalogenation of α, α'-dihalosubstituted precursors, (B) the thermal extrusion of XY (XY = HCl, Br2, and CH4,) from η3-methylallyl complexes, (C) the ring opening of alkylidenecyclopropanes, and (D) the elimination of Me3SiX [X = OAc, Cl, OS(O)2Me] from functionalized allylsilanes (Figure 1).

[9] According to gas phase electron diffraction, η4-C(CH2)3]Fe(CO)3 adopts a staggered conformation about the iron center.

The ligands, which include carbonyl and a trigonal-pyramidal trimethylenemethane, are arranged in the usual umbrella-type configuration.

[12] Introducing a puckered conformation to the trimethylenemethane ligand, which resembles the experimental geometry, leads to an increase in the calculated barrier to 98.6 kJ mol−1.

This puckering induces mixing of s character into e" orbitals, causing a more pronounced orientation toward the metal center.