Abstract
The synthesis and characterization of the triethanolamine (TEA) complexes Sc(TEA)2Cl3 (1), Y(TEA)2(ClO4)3·3C5 H5N (2), Fe(TEA)2Cl3 (3), Ni(TEA)2Cl2 (4), Zn(TEA)2Br2 (5), Zn(TEA)2(NO3)2 (6), Cd(TEA)2Cl2 (7), Cd(TEA)2(NO3)2 (8), Pb(TEA)2(OAc)2 (9) and Bi(TEA)2Cl3 (10) are reported. The structures of 2 and 8, determined by X-ray diffraction, unexpectedly revealed eight-coordinate metals in both cases. Both structures adopt a distorted hexagonal bipyramidal configuration in which the atoms in the hexagonal plane alternately fall above and below the plane. In 2, the tree pyridines as well as the three perchlorates are involved only in hydrogen bonding to the OH groups of different TEA ligands, causing a novel distortion of the coordination sphere. Compound 8 represents an unusual example of the relatively rare coordination number eight for cadmium(II).
| Original language | English (US) |
|---|---|
| Pages (from-to) | 393-400 |
| Number of pages | 8 |
| Journal | Polyhedron |
| Volume | 14 |
| Issue number | 3 |
| DOIs | |
| State | Published - Feb 1995 |
| Externally published | Yes |
Bibliographical note
Funding Information:The ORTEP drawing of the cation of 8 is shown in Fig. 4 while the unit cell depiction is given in Fig. 5. Here cadmium is eight-coordinate as a result of iigation by two TEA groups. This coordination number is not common for cadmium, 15 and it has been structurally verified in only eight other instances, all but one of them in complexes containing macrocyclic ligands.1~21 In striking contrast to 2, the M--O and M--N lengths for both TEA groups are almost equal in 8 as a result of similar hydrogen bonding between the OH groups of each TEA and the NO3 anions. The average Cd--O bond distance in 8 is 2.417(3) A which closely matches that reported for \[Cd(L)(NO3)2\] (2.396 (3) /k) wherein cadmium is eight-coordinate and L = 1, 4, 7, 10-tetraoxa-13-azacyclopentadecane.17 However, it is shorter than that in catena-bis(#-6- amino-3-methyl, 5-nitrosouracilato-N 5, 0 4, N I, O2)cadmium (2.625(2) /k) in which the cadmium is eight-coordinate.16 The metal-oxygen distance in Cd9(OC2H4OMe)ls"2HOCzH4OMe ranges from 2.129(6) A to 2.555(6) /~.22 The Cd--O distances in this cluster complex fall in the pattern Cd--O (terminal) < #2,r/l-Cd--O ~ #-r/2-Cd--O </~3-r/2-Cd--O < Cd--O(ether). In 8 the average Cd--O distance lies between/42,ql-Cd--O or #-q2-Cd--O and #3-~f-Cd--O. The Cd--N bond in 8 is 2.460 (2) A, which is only slightly longer than the Cd--O link. This is in striking contrast with the structure of 2 in which the average Y--N bond length is about 0.3 /k longer than the average Y--O bond distance. Noteworthy is the 167.6(1) ° angle for the N(1)--Cd--N(1A) angle in 8 which contrasts that in centrosymmetric species such as the Sr(TEA)~ + cation. 8b Acknowledgments--The authors are grateful to the NSF for grant support of this work. They thank Dr K. Erd-mann for the solid state ~3C NMR spectra.
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