Trigonal Paddlewheel

Theoretical calculations were performed, initially with SCF-Xa-SW methods on a truncated model [16], and later with the complete active space self-consistent field (CASSCF) and mul-ticonfigurational complete active space second-order perturbation theory (CASPT2) methods on the full molecule [15]. The electronic structures from the two calculations were remarkably similar. The CASSCF/PT2 calculations predicted a single, dominant configuration (73%) with (a) (x) (x ) (a ) (8) (5 ). Although the formal bond order is 1.5, the effective bond order, which considers minor configurations that contribute to the ground-state wavefunction, is lower at 1.15. 

Fe-Fe distance is longer by 0.06-0.09 A than that in tris(amidinate) Fej paddlewheels, considerable lengthening of the Fe-Fe bond was expected with the addition of trans donors. 

The Mossbauer spectrum of FelNArP PrjljFeCl contains two doublets. One doublet with an IS = 0.69 mm s and QS = 2.63 mm s is assigned to the triamido iron while the other doublet 

The bonding in the Fe Fe =lSrR core was investigated by DFT, as these are the first examples of metal-ligand multiple bonds that are tram to an M-M interaction involving rst-row metals. Overall, the d-electrons are highly localized, and M-M bonding interactions are evident only in the o(Fe-Fe) and the three-centered a (Fe-Fe-N) orbitals. The Fe-Fe bond order is predicted to be low at 0.5, which is consistent with a weak Fe-Fe interaction. 

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The syntheses of the tetragonal paddlewheel compound, Co2(DAniF), ([DAniF]" =Al,A/ -di-p-anisylformamidinate), and the trigonal paddlewheel compound, Co2(DAniF)3 have been reported... 

Figure 9.42 Secondary Building Units (SBU) using carboxylates with rigid coordination geometries that replace metal ions as vertices in MOFs. (a) Paddlewheel or lantern structure as in 9.17, (b) octahedral basic zinc acetate SBU used in MOF-5 and (c) a trigonal prismatic oxo-centred trimer. The poly-hedra use carboxylate carbon atoms as their vertices and the MOFs propagate via the linkers attached to these carbon atoms. The metal atoms are bound to only terminal ligands in addition to those shown.

Fig. 17 Commonly recurring structural motifs, (a) the paddlewheel dimer of Cu05 square pyramids, (b) the tetrahedron of Zn04 tetrahedra sharing a central oxygen, and (c) the trigonal planar trimer of OO, octahedra sharing a central oxygen. Gray spheres denote carbon and red oxygen CuO,. ZnO-. and CrC>6 polyhedra are shown in dark blue, pale blue and green, respectively.

The RUj non-paddlewheel complexes can be classified by their geometry - tetragon2il versus trigonal - and further classified by their supporting ligands. Nearly all the unsupported Ruj complexes are tetragonal. 

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