Coordination polyhedron, inversion

Inversion of the Metal Coordination Polyhedron along the O-M-O Axis... 

This reasoning also holds for the reactivity on the Mo(IV) center as illustrated in Fig. 19b and confirmed experimentally (7). A deviation of the experimental points for the inversion of the coordination polyhedron was obtained from the oxygen exchange on the oxo site in the [MoO(OH2)(CN)4]2 complex at pH <6 (Fig. 19b was observed and was interpreted in Section VI,B). 

The inversion of the N-atoms in the diethylenetriamine backbone is precluded. The central N-atom is always chiral, since the ethylene bridges around it have different conformations (<5 and A). Furthermore, the two other N-atoms are chiral as well in the bisamides and chirality of the metal ion should be taken into account. DTPA derivatives with three chiral N-atoms can be wrapped around the Ln3 + ion in 16 different ways (8 diastereomeric pairs, see Fig. 1). In crystal structures of these compounds the Ln3+ coordination polyhedron can generally be best described as a tricapped trigonal prism (TTP). For [Ln(DTPA)]2-A1=A2=A3 = B1=B2, and, consequently, only two enantiomers remain (1/1 ). Analogously, it can be seen that the DTPA-bisamides can have 4 diastereomeric pairs. 

The difference between these two cases is represented by the relative position of the two triangles to the referential hexagonal plane. In the late case, the two triangles are rotated one to each other with 7i/3 angle. Therefore, the resulted structure features an A axis, i.e., an inversion center the coordination polyhedron of the particle with CN=12 in this... 

Of special interest is the crystal structure determination of Sml2 (9P3)2. The complex crystallizes in the monoclinic P2j/n space group. The 8-coordinate Sm(II) lies on an inversion centre and its coordination polyhedron is a distorted... 

The skeletal structure of [Sn(OBu03l2Sr (2) shows that the polyhedron is built from two Sn03Sr trigonal bipyramids connected via a common apex with retention of the three-fold axis. The apical position, which at the same time is a center of inversion, is occupied by the strontium atom with a distorted octahedral environment (Figure 2.12.3). The Sn atoms are trigonal bipyramidally coordinated (O-Sn-O 82.3(1)°) and the average Sn-0 and Sr-0 distances are 2.078(3) and 2.523(3) A respectively. 

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