Reversible bidentate-tridentate

They have also demonstrated a reversible photochemical conversion from a tridentate to a bidentate B3H8 (Fig. 14). Fehlner has achieved a photochemical carborane synthesis by irradiating mixtures of B4H8Fe(CO)3 and dimethylacetylene. Products of the reactions include (CH3)4C4B4H4 and (CH3)8C8B4H4. Leyden and co-workers have observed two examples of metalloborane isomerization reactions initiated by light ... 

In addition to chelate complexes, the cyclic amine 1,4,7-triazacyclononane will complex to platinum(II) and (IV). The hexacoordinate platinum(IV) complexes are bonded to two molecules of the tridentate ligand, but platinum(II) complexes with the ligand monodentate and bidentate.988 Also the formation of platinum(II) ammine complexes from chloride complexes is a reversible process. The rate constants decrease as the basicity of the leaving amine increases.989... 

The tridentate macrocyclic ligands 1,4,7-triazacyclo-nonane and 1,4,7-trithiacyclononane (39, E = NH, S, respectively), act as bidentate chelates toward Pd(II) to give square-planar complexes [Pd L2] + with two pendant E donor atoms (40). The complexes can be oxidized chemically or electrochemically to [Pd L2] + (41) (equation 15), which show tetragonaUy elongated octahedral coordination, as expected for a Jahn-Teller distorted d complex. Interestingly, electrochemical stndies on the Pd(n) complexes (30) and (31) (Section 6.5) show that only the second can be reversibly oxidized to Pd(III). 

Histidine and asparagine function as tridentate chelates. In the asparagine complexes, the mixed (dl) form is the more stable while the reverse is true of the histidine complexes. Potentiometric studies of the complexes of various metals (Nill, Cull, Coll, Znll) with a wide range of amino adds all of which function as bidentate chelates have failed to reveal any differences in the stability of Mdl and Mll forms. (Ritsma et al. 1965 Gillard et al. 1966). The reason why the chirodiastaltic interactions should be so much more marked with tridentate than bidentate chelates calls for investigation in terms of the intramolecular force system. 

Electrochemical studies on [Cu(9S3)2] show reversible reduction to the colorless Cu(I) complex (Table 2 Eq. 5b) [93,96], Three obvious structures can be envisaged for [Cu(9S3)2], which has so far eluded structural characterization. Like the Cu(II) complex, [Cu(9S3)2] could be six-coordinate ([3 + 3] coordination). This unlikely (c.f. [Cu(l 856)] below) possibility cannot be dismissed in light of six-coordination in the congeneric complex [Ag(953)2] [114,115,116]. Alternatively, tetrahedral coordination could arise from slippage of one 953 ring with respect to the other (tridentate) one to coordinate in a monodentate fashion ([3 + 1] coordination). Tetrahedral coordination could also be effected by slippage of the two rings such that each coordinates in bidentate fashion ([2 + 2] coordination),... 

A trimethylplatinum(iv) complex with tris(3,5-bistrifluoromethylpyrazolyl)borate as a ligand has been prepared and studied by H-F two-dimensional NMR spectroscopy the spectra exhibit long-range G-H-F-C interaction which is evidenced also by IR spectra.1,4,7-Triazacyclononane coordinates to the Pt(ii) center as a bidentate ligand and to the Pt(iv) center as a facial tridentate ligand. Square-planar dimethylplatinum(ii) complex 1006 is in equilibrium with the octahedral hydrido (dimethyl)platinum(iv) complex 1007 in MeOH via reversible protonation of the Pt(ii)... 

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