MULTINUCLEATING LIGANDS FROM MULTIPLE PALLADIUM(0)-CATALYSED CROSS-COUPLING REACTIONS - SYNTHESIS AND CHARACTERISATION OF A TRINUCLEAR CYCLOMETALLATED RUTHENIUM(II) COMPLEX AND A HEXANUCLEAR EPR-ACTIVE MOLYBDENUM COMPLEX

摘要

Two multinucleating ligands have been prepared from 1,3,5-tris(3,5-dibromophenyl)benzene by multiple Pd(0)-catalysed cross-coupling reactions. 1,3,5-Tris[3,5-bis(4-pyridylethenyl)phenyl]benzene (L(1)) has six remote pyridyl moieties, each of which can coordinate a 17 valence-electron (Mo(tp*)(NO)Cl} fragment (tp*=hydrotris(3,5-dimethylpyrazolyl)borate), affording the hexanuclear complex [{Cl(NO)(tp*)Mo}(6)(L(1))] (1). 1,3,5-Tris[3,5-bis(2-pyridyl)phenyl]benzene (L(2)) incorporates three potentially terdentate, cyclometallating N,C,N-donor sets, and can coordinate three {Ru(tpy)}(2+) fragments (tpy=2,2':6',2''-terpyridine) giving the trinuclear complex [{(tpy)Ru}(3)(L(2))][PF6](3) (2). Complex 1 is EPR active, with nearest-neighbour pairs of molybdenum centres displaying magnetic exchange interactions. Electrochemical studies of the two complexes suggest that there is little ground-state interaction between the metal centres in either case. [References: 29]