Highly-symmetric complexes

To illustrate this point, the contributions of the occupied molecular orbitals to the total electron density at the nucleus are summarized in Table 5.2 for Fep4 (S - 5/2). It is evident from the table that the contributions coming from the orbitals at —6,966 eV must be assigned to the iron Is orbital, those from orbitals at —816 eV to the iron 2s orbital, and those from orbitals at —95 eV to the iron 3s orbital. In this highly symmetric complex, only two valence orbitals contribute to p(0), i.e. the —25 eV contribution from the totally symmetric ligand-group orbital that is derived from the F 2s orbitals and the —1 eV contribution from the totally symmetric... 

While the rotation barriers for highly symmetric complexes such as Mo(CO)(H2)(dppe)2 (7) can be extremely low (0.6 kcal/mol), they are not in fact zero. This is because X-ray data reveal that the structure of the MP4 fragment is distorted with at least one of the P-M-P axes bent back away from the H2 (with which it is nearly parallel). The distortions rehybridize M orbitals such that the overlap with [Pg.184]

The frequency of most interest Vhh is not formally forbidden in the IR of H2 complexes, but is polarized along the direction of the M-H2 bond in highly symmetric complexes. Therefore, intensity arises only from coupling of , with other modes of the same symmetry such as vs(mh2) or Vco if CO is present, and... 

Phosphinidenes, are however, most conunonly of the m or 1X4 type (8.134). The highly symmetrical complex Nig(CO)8(p.-PPh)6 is based on a central confignration of 8 Ni atoms situated at the corners of a cube (8.134a) with a carbonyl group attached to each comer. The PPh groups are centred over each of the six faces of the cube with each P atom equidistant from four... 

The characterization of the lanthanide(II) [8]annulene complexes is, however, limited. The infrared spectrum of Yb(C3HQ)i2 suggests a highly symmetric complex (the only bands present between 1000 and 600 cm"i occur at 888 and 678 cm-M. a and the low solubility of the complexes in hydrocarbons, ethers and liquid ammonia suggests that the class LnlCgHg) is polymeric.59... 

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