SURPRISINGLY FACILE DECOMPOSITION OF THE DICATION [(C(5)ME(5))IR(MEO-C6H4-CH2CO2NCOCH2CO)](2- A METAL-MEDIATED HUNSDIECKER REACTION OF A SUCCINIMIDYL ESTER() )

A series of dicationic organoiridium complexes [CpIr(arene)](2+), (4, 5 and 6) have been prepared in which the pi-bonded phenyl ring is att ached to an alkyl chain terminated by a succinimidyl ester, thus formi ng Bolton-Hunter reagents for protein labelling. In solution, the benz yl derivative, 4, underwent facile decomposition. Loss of the succinim idyl moiety followed by decarboxylation led to [CpIr(eta-MeO-C6H4-Me) ][BF4](2) (7). This product was characterized spectroscopically and by X-ray crystallography. Compound 7 crystallizes in the space group P2( 1)/a with a = 13.567(5) Angstrom, b = 17.664(1) Angstrom, c = 9.044(5) Angstrom, beta = 90.15 degrees, V = 21.67 Angstrom(3) and Z = 4. A ra tionale for this surprisingly facile decomposition invokes stabilizati on of the intermediate benzyl radical by the iridium.