Multidentate amines

Multidentate amines form many complexes with these metals. 

Reactions of selected metal complexes of multidentate amines with formaldehyde and a range of carbon acids (such as nitroethane) have led to ring-closure reactions to yield a series of three-dimensional cage molecules (see Chapter 3). Condensations of this type may also be used to produce two-dimensional macrocycles (Comba et al., 1986) - see [2.20], In such cases, it appears that imine intermediates are initially produced by condensation of the amines with formaldehyde as in the Curtis reaction. This is followed by attack of the conjugate base of the carbon acid on an imine carbon. The resulting bound (new) carbon acid then reacts with a second imine in a cis site to yield chelate ring formation. 

A wide range of multidentate amine ligands coordinate to platinum. The conformational analysis of chelate ring systems by NMR has been reviewed by Hawkins, and platinum complexes are included in this work.959 Amine ligands with sulfur groups can also act as chelates, and this subject has also been reviewed.960... 

In general, the literature contains fewer references to complexes formed from monofunctional amines than to those formed from ammonia itself or from multidentate amines. However, some clarification of earlier studies is to be found in recent reports, e.g. the complexes [Cd(PhNH2)X2] (X = C1 or Br), and their deuterated derivatives, have been reinvestigated and shown to be octahedral.166 This latter study clarified some of the confusion present in the earlier literature concerning these compounds. Another aniline complex, 3CdCl2-4L, has been studied and it has been shown that there are two types of octahedral environment in which the cadmium atoms are found, one comprising a CdCU unit and the other a CdCL unit.167... 

N-3 Acyclic multidentate amine ligands yield polymeric solid complexes with Ag(I). Thus, diethylenetetramine and tris(2-aminoethyl)amine give 128 and 129, respectively. In the presence of unidentate ligands such as PPhs, PMe3 and /-BuNC polymer formation may be hampered, as in 130215. 

Shinozuka and co-workers [34] developed bleomycin model complexes bearing long alkyl chains. The multidentate amine ligand contains imidazole and shows high oxygen-activating capacity. 

Reaction of selected metal ion complexes of multidentate amines with formaldehyde and a variety of activated carbon compounds (such as nitro-methane or diethyl malonate) have led to ring closure to yield polyaza macrocycles (Comba et al., 1986 Lawrance and O Leary, 1987). Reaction with the malonate ester gave less than a 2% yield. Another approach for the... 

Troutner DE, Volkert WA, Floffman TJ, Flolmes RA (1984) A neutral lipophilic complex of " Tc with a multidentate amine oxime. Int J Appl Radiat Isot 35 467-470... 

Syntheses reported for the pentaammine(trifluoromethanesulfonato-O) complexes can be readily adapted for other amine or multidentate amine analogs. Syntheses of coIbalt(III) complexes with 1,2-ethanediamine or A -ethyl-l,2-eth-anediamine ligands have been reported earlier in this series. To exemplify the procedures further, trifluoromethanesulfonato-O complexes of cobalt(III), chro-mium(III), and rhodium(III) with unidentate methylamine ligands based on the readily prepared [M(NH3)5Cl]Cl2 precursors are reported here. The following sections report syntheses of 1,2-ethanediamine complexes of Rh(III) and Irflll) and of Ru(II) and Os(II) diimines with trifluoromethanesulfonato ligands. Such syntheses indicate the diversity of the synthesis technique, and the complexes described are excellent precursors for other compounds. 

Multidentate amine ligands react readily with palladium(II) halides to yield chelated products. Crystal structure determinations have been carried out for 1,2-diaminoethane complexes [PdCl2(en)], [Pd(en)2]Cl2 and [Pd(en)2][Pd(S203)2(en)]. A variety of 1,2-diaminoethane, 1,2-diaminocyclohexane and 1,3-diaminocyclohexane complexes have been prepared because their necessarily cis geometry makes them analogous to the antitumour platinum complexes. In contrast to compounds tram-[PdX2L2] these former complexes are claimed to have activity comparable with or greater than that of cisplatin. ... 

Finally, a DEER study on models for molecular wires made from butadiyne-linked zinc porphyrin oligomers, end-labeled with nitroxide radicals, was performed by Lovett, Anderson, and coworkers [107]. Unlike in [104—106], one can control the conformations of these metalloporphyrin-based strucmres by self-assembly with multidentate amine ligands, which bend the rigid oligomeric structure. The experimentally found end-to-end distances in these complexes match the predictions from molecular dynamics calculations. This study thus presents a proof-of-principle that DEER spectroscopy is also well suited for understanding more complex supramolecular stmctures. 

Y. Shen, S. Zhu, F. Zeng, R. H. Pelton, Atom transfer radical polymerization of methyl methacrylate by silica gel supported copper bromide/multidentate amine. Macromolecules 2000, 33, 5427-5431. 

Fig. 10. Multidentate amines used by Hillmyer and co-workers as yttrium ligands.

Multinuclear complexes of Y alkoxide have been S3uithesized with multidentate amines and they have shown high activity in ROP (Fig. 10) (63,64). Although the polymerization of e-CL can be controlled, the polydispersity is rather high (1.5 < PDI < 1.7), and parasitic aggregation and clustering can be the source of complexity. 

Xia, J., and Matyjaszewski, K. (1997). ControUed/ living radical polymerization. Atom transfer radical polymerization using multidentate amine ligands. Macromolecules, 50(25) 7697-7700. 

Xia, J.H., Matyjaszewski, K. 1997. Controlled/"Living" Radical Polymerization. Atom Transfer Radical Polymerization Using Multidentate Amine Ligands. Macromolecules 30 7697-7700. 

---