The transmetallation reaction between [(η 6 -arene)RuCl 2 ] 2 (η 6 -arene = C 6 H 6 (benzene) (1); 1-Me-4- i Pr-C 6 H 4 (cymene) (2); 1,2,4,5-Me 4 -C 6 H 2 (durene) (3); 1,2,3,5-Me 4 -C 6 H 2 (isodurene) (4) and the aminoaryl-mercury derivatives Hg{Q-dmba} 2 (Q-dmba = 1-{C 6 H 3 -3-F-6-CH 2 NMe 2 } (a); 1-{C 6 H 3 -3-Me-6-CH 2 NMe 2 } (b); 1-{C 6 H 2 -2,3-OCH 2 O-6-CH 2 NMe 2 } (c); 1-{C 6 H 2 -2,4-(MeO) 2 -6-CH 2 NMe 2 } (d); 1-{C 6 H 4 CH 2 NMe 2 } (e)) affords the corresponding C,N-cycloruthenated complexes [(η 6 -arene)RuCl{Q-dmba}]. All complexes were charaterised by 1 H and 1 3 C{ 1 H} NMR. The reaction seems to be governed by steric rather than by electronic factors: an increase in the number of alkyl substituents in the η 6 -arene ligand or the presence of bulky groups ortho to Hg in the starting material leads to a significant decrease of the yields of the desired cycloruthenated products.