Characteristic Reactivties and Functions of Metal Complexes containing Hypodentate Ligands.

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Hypodentate ligand is defined as a ligand in which fewer than the maximum possible number of donor atoms are bonded to metal centers. The purpose of the study is to prepare various new complexes containing such ligands and to investigate their reactivities and functional characteristics. In particular we have paid special attention to luminecent complexes as the control of photophysical properties by using uncoordinated ligand moieties are promising. The results obtained by using polypyridyl ligands such as tris(2-pyridylmethyl)amine (tpa) and N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (tpen) are as follows, (i) A series of planar Pt(II) and Pd(II) complexes with these ligands all have uncoordinated arms. The exchange of the free and coordinated arms have been found in the order Pt(II) < Pd(II) and tpa < tpen. (ii) Luminescent [Re(CO)_3(tpa)]^+ has been prepared which also has one uncoordinated arm that does not undergo exchange with the coordinated ones. (iii) V^<IV>O complexes of tpa has fully coordinated tpa (tetradentate), different from ReO-tpa complexes which have tridentate tpa, but with tpen V^<IV>O complex containing hypodentate ligand has been isolated. With the diphosphine ligands Ph_2P(CH_2)_nPPh_2 (n = 1 - 5), a series of luminescent hexarhenium cluster complexes containing monodentate diphosphines have been obtained. For the hexarhenium unit, we have also successfully introduced giant ligands free base pyridylporphyrines. We have also used a small polydentate ligand, 2.5-dimercapto-1,3,4-thiadiazole(McMTH). The complexes prepared include those containing a monodentate McMT are [Pt(terpy) (McMT)]^+ and [Ru(terpy)(bpy)(McMT)]^+. They react with another Pt(terpy)-unit to form homo and hetero dinuclear complexes. Furthermore various type of Cu(I) and Ag(I) complexes of McMT ligands have been obtained. All these McMT complexes are strongly luminescent.