SYNTHESIS AND CHARACTERIZATION OF CATIONIC SQUARE-PLANAR IRIDIUM(I) COMPLEXES CONTAINING CHIRAL DIPHOSPHINES

Cationic square-planar complexes of the type [Ir(diphosphine)(2)]Cl (d iphosphine = (R,R)- and rac-cypenphos, (S,S)-chiraphos, (R)- and rac-p rophos, (R)-phenphos) have been synthesized starting from [Ir(COE)(2)C l](2) or [Ir(C2H4)(2)Cl](2). The complexes were fully characterized th rough H-1- and P-31{H-1}-NMR spectroscopy. With the C-1 diphosphines b oth cis and trans isomers are formed with low selectivity. Using racem ic cypenphos no diastereoselectivity in the formation of the complexes was observed. For the racemic prophos the diastereoselectivity is dif ferent for the two geometrical isomers formed. A study of the electroc hemical behavior of these complexes in acetonitrile with some attentio n to the characteristics of the electron transfer process has been car ried out. The results are compared with those previously obtained in t he reduction of the corresponding dppe derivative and provide a tool f or the determination of the relative basicity of the ligands. The redu ction was found to proceed by a single two-electron step to a d(10) an ion, which is quenched by the protic solvent to give the final metal h ydride derivative which in the case of complexes 2 and 3 were observed by NMR spectroscopy.