Impact of the ligands on linear trimetal chains

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Title: Impact of the ligands on linear trimetal chains
Author: Lei, Peng
Abstract: Increasing attention has been given to the preparation and study of compounds with linear chains of metal atoms surrounded by four ligands . The majority of linear trimetal complexes are supported by dpa , the anion of dipyridylamine , having the general formula M3 (dpa )4X2 , where X is typically a monoanion . It has been shown that the behavior of the trinuclear system is far more complicated than might have been expected . Specifically , both symmetrical and unsymmetrical chains can occur and the interpretation of the magnetic properties of certain compounds has been a challenging task . Present in this dissertation is the bulk of work completed on an exploration of syntheses and characterizations of linear trichromium and trinickel compounds with different types of tridentate ligands . These ligands include 2 ,6 -bis (phenylamino )pyridine ,H2BPAP , (the corresponding dianion of this is denoted by BPAP ) and a set of five unsymmetrical formamidines with different organic substituents ranging from strong electron -donating groups , such as -OCH3 , to electron -withdrawing groups , e .g . , F . Ligands impact on the trimetal chain in various ways . In the case of the M3 (BPAP )42 - ions , there are no axial interactions because these anionic species do not attract electron donating ligands . Thus they have properties which are different from those of M3 (dpa )4X2 molecules . Most notably , the Ni3 (BPAP )42 - ion is diamagnetic and all three nickel ions can be described as square -planar , low -spin NiII centers . ivWhen unsymmetrical formamidines are used to support linear trichromium chains with a Cl anion at each end , the separation between terminal chromium atoms is significantly longer (ca . 0 .15 - 0 .25 ) than those in trichromium compounds reported earlier . Moreover , the unsymmetrical formamidinates tend to support symmetrical trichromium chains , while the rest of the known tridentate ligands typically yield unsymmetrical Cr36+ chains . The synthesis and structural studies of trinickel compounds with unsymmetrical formamidines are also presented .
URI: http : / /hdl .handle .net /1969 .1 /253
Date: 2004-09-30


Impact of the ligands on linear trimetal chains. Available electronically from http : / /hdl .handle .net /1969 .1 /253 .

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