NEW TRICKS FOR AN OLD LIGAND - CYCLOMETALATED AND DIDENTATE COORDINATION OF 2,2'6',2''-TERPYRIDINE TO RUTHENIUM(II)

Monomethylation of 2,2':6',2 ''-terpyridine (terpy) afforded the N-met hyl-2,2':6':2 ''-terpyridinium cation, [Hmterpy](+). With one of the t erminal pyridine ring nitrogen atoms thus protected;it co-ordinates to ruthenium(II) either as a didentate N,N'-donor giving [Ru(terpy)(Hmte rpy-N,N')Cl][PF6](2), or as a cyclometallating terdentate ligand givin g [Ru(terpy)(mterpy-N,N',C)][PF6](2), depending upon the reaction cond itions. Both complexes have been fully characterised by spectroscopic and electrochemical methods, and the crystal structures of [Ru(terpy)( mterpy-N,N',C)][BF4](2) . 2MeCN and [Ru(terpy)(Hmterpy-N,N')Cl][PF6](2 ) . 2MeCN determined.