Oxygen-bound Ligands

The kinetics of isomerization of complexes of type [Al(/ -diketonato)a] were studied earlier and now isomerization involving the cis- and trans-lsomevs of a related complex (15) has been studied. The trans (Ci) isomer on dissolving in CCI4 is converted into an equilibrium mixture with the cis (C3) isomer the rates of isomerization and the equilibrium positions have been determined. The intramolecular process relates kinetically to similar processes involving classical / -diketonato-ligands. 

A change in the pattern of Pt to Me coupling with temperature has been used to identify a dynamic process in complex (18). - Between -95 and 

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The effect of the metal ion may be gauged by comparison of trans-[FeCl2(DMSO)all oxygen-bound (5), and cis-[RuC12(DMS0) ], with three sulfur and one oxygen-bound ligand... 

The X-ray crystal structure of [Ru(DMSO)g ] (BFi >2 shows three sulfur-bound fac to three oxygen-bound ligands (14), confirming the structure proposed from N.M.R. studies in CD2CI2. However, in D2O, the N,M,R. measurements show four S-bound ligands and two free DMSO molecules arising from substitution of the easily-displaced 0-bound sulfoxides by solvent ... 

The important point to appreciate is that the formal valency of zinc is satisfied by two bonds to sulfur so that the additional interactions are indeed hypervalent interactions. Thus, the nature of the adopted structures arises from the ability of the central element to form hypervalent, or secondary, interactions and it is proposed that this ability is moderated by steric considerations associated with the alkyl substituents. As noted from the structural studies for the uncoordinated xanthate anions summarized earlier in Section II, there are no electronic differences among the xanthate ligands that can be correlated with the nature of the oxygen-bound substituent. This conclusion is vindicated by the homogeneity of the molecular structures of the binary nickel xanthates as... 

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