Molecular Structures of Triiron Dodecacarbonyl and Tetracobalt Dodecacarbonyl

Aromaticity of Tri‐ and Tetranuclear Metal–Carbonyl Clusters Based on Magnetic Criteria

“…[34] Results and Discussion 12 ] has a C 2v structure with two bridging groups, [5] in contrast to the D 3h symmetry of the rutheniumand osmium-carbonyl clusters with only terminal CO groups. [35] The stability of [M 3 (CO) 12 ] (M = Fe, Ru, Os) clusters is generally explained in terms of s-aromaticity, [12] which has long been invoked in the description of the electronic structure of cyclopropane; [11,36,37] strong evidence [11g] exists for this phenomenon.…”

“…[1] However, the trinuclear nature of 1 was only realized by Hieber and Becker [2,3] in 1930 after cryoscopic molecular weight determinations in [Fe(CO) 5 ]. The correct triangular C 2v structure of 1 with two bridging CO groups was established definitively by X-ray diffraction only in 1966 after considerable controversy [4] and difficulties with disorder problems.…”

“…The correct triangular C 2v structure of 1 with two bridging CO groups was established definitively by X-ray diffraction only in 1966 after considerable controversy [4] and difficulties with disorder problems. [5,6] The ruthenium and osmium analogues [M 3 (CO) 12 ] (M= Ru, Os), unlike Fe 3 (CO) 12 , have structures with exclusively terminal CO groups and have more robust metal-metal bonds in their M 3 triangles. [7][8][9][10] These triangular metal-carbonyl complexes may be regarded as analogues of cyclopropane in which the three CH 2 groups are replaced by isolobal and isoelecctronic M(CO) 4 groups (M = Fe, Ru, Os).…”

A Carbonyl Group Bridging Four Metal Atoms in a Homoleptic Carbonylmetal Cluster: The Remarkable Case of ­Co4(CO)11

“…[1] Subsequent X-ray crystallographic studies [2][3][4] show Co 4 (CO) 12 to contain a Co 4 tetrahedron with Co-Co distances of 2.50 Å for the three edges bridged by CO groups and 2.48 Å for the three unbridged edges leading to overall C 3v symmetry ( Figure 1; M = Co). Because the cobalt atoms in Co 4 (CO) 12 have the favored 18-electron configuration if all of the Co-Co edges in the Co 4 tetrahedron correspond to single bonds, these Co-Co distances around 2.50 Å can be taken as indicative of single bonds in these metal-cluster structures.…”

“…[5] However, the corresponding valence-isoelectronic carbonyliridium compound Ir 4 (CO) 12 has this more symmetrical unbridged structure ( Figure 1; M = Ir). [6] The M(CO) 3 (M = Co, Rh, Ir) vertex units in these tetranuclear carbonylmetal groups are isoelectronic and isolobal with phosphorus atoms. The M 4 (CO) 12 derivatives, particularly the symmetrical T d structures (Figure 1), are thus closely related to P 4 (white phosphorus), which is a spherically aromatic system.…”