Bond lengths macrocyclic complexes

Donor atom to metal-ion bond lengths which are shorter or longer than expected as well as unusual angular relationships between such bonds have all been documented in macrocyclic complexes. Such effects can be a prime cause of the unusual properties mentioned previously. Thus the... 

Also, the structure of 63 is better described as zwitterionic with a C-N bond length of only 1.651 A <2001J(P2)133> in the case of methoxy instead of NMe2, the MeO- C=S separation is longer (2.550 A) and the two substituents behave as normal /rm-substituents. Furthermore, the 2,6,9-trioxo-bicyclo[3,3,l]nona-3,7-diene moiety 64 has been structurally characterized as part of Pd(ii) complexes <2003JOM(676)93> and as a novel chiral spacer unit in macrocyclic polyethers <2002SMC383, 2004T2857>. 

The complexes in Table I have been assigned an end-on geometry on the basis of spectroscopic data, chemical behavior, and, in the case of a macrocyclic rhodium complex, X-ray crystallographic data (53). The 0-0 stretching frequencies and 0-0 bond lengths are useful indicators of the electronic structure of coordinated dioxygen (54-59),... 

In [Ag(3,2,3-N5)]C104 there were two cations of similar geometries in the unit cell. Ag—N bond lengths were in the range 237-255 pm.452 In the dimeric complex [Ag(2,3,2-N5)]2(C104)2, two near planar [Ag(2,3,2-N5)]+ cations were associated in a face to face fashion such that each Ag1 ion interacted with an N of the other macrocycle. The Ag—Ag separation was 317.7 pm, which may have represented a weak Ag--Ag bond.453... 

Fig. 13 Aromaticity analysis in free-base porphyrin (top), porphyrin dianion, and porphyrin complex (bottom) [37]. Bond lengths (in Angstroms) are averages obtained from X-ray structural data. Values in parentheses correspond to calculated geometries (B3LYP/6-31G, no substituents, M = Mg). HOMA indices were calculated from the average (calculated) bond lengths. The values inside the macrocyclic ring and outside the macrocycle correspond respectively to the inner cross ([16]annulene circuit) and the complete macrocycle. NICS values (GIAO-RHF/6-31 + G ) were calculated at the points indicated with dots...

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