Transition metal (Mn, Co) and zinc formamidinate compounds having the basic beryllium acetate structure, and unique isomeric iron compounds

Oxidation of Co₂(DPhF)₃ or hydrolysis of Co₂(DPhF)₄ (DPhF=N,N′-diphenylformamidinate) gives Co₄O(DPhF)₆ (I). This tetranuclear compound consists of an oxygen atom centered in a tetrahedron of four-coordinate Co atoms with a DPhF bridge along each edge of the tetrahedron. An idealized T_d symmetry is also found for zinc, II, and manganese, III, analogs. The latter, Mn₄O(DPhF)₆, crystallizes in a disordered fashion so as to appear as two interpenetrating tetrahedra. Two μ₄-O tetrairon compounds, namely, Fe₄O(DPhF)₆ (IV) and Fe₄O(DBiPhF)₆ (V) (DBiPhF=N,N′-bisbiphenylformamidinate) are also described. These molecules are isomers of the Co, Zn and Mn molecules in that they have the 'tetrahedron' of metal atoms badly distorted by a different distribution of the formamidinate ligands. Two opposite Fe-Fe edges are doubly bridged, another two opposite edges are singly bridged and the remaining two edges are unbridged. The lengths of these three pairs of opposite edges are shorti medium and long and the idealized molecular symmetry is only C₂. Crystal data for I·toluene at -60°C are: triclinic, space group P1̄, a=13.426(3), b=13.491(3), c=22.600(5) Å, α=99.55(3), β=95.39(3), γ=111.80(3)°, Z=2. For II·1.45C₆H₁₄ at -60°C: orthorhombic, space group Pbca, a=23.8113(8), b=23.406(2), c=30.956(1) Å, Z=8. For III at - 150°C: trigonal, space group R3, a=23.440(1), c=10.708(1) Å, Z=3. For IV·1.5 toluene at -60°C: triclinic, space group P1̄, a=14.920(3), b=15.539(3), c=19.027(4) Å, α=84.63(3), β=85.67(3), γ=63.30(3)°, Z=2.