ESI-MS date for the arene ruthenium(ii) complexes 2a–2d.

Complex	Type ions [XRuL]+	Type ions [XRuLCl]+	Sandwich ions	Ions in negative mode
2a	388.1(34%), 389.1(42%), 390.1(72%), 392.0(40%)	423.1(42%), 425(69%), 426.1(100%), 427.1(36%), 428.0(76%)	811.9(11%), 812.9(13%), 813.6(10%), 814.8(19%), 815.6(13%), 816.9(10%)	Not observed
2b	415.1(45%), 416.1(49%), 417.1(59%), 418.1(100%), 419.1(33%), 420(74%)	452.1(20%), 453.1(43%), 454.1(63%), 456.0(54%)		Not observed
2c	451.1(42%), 452.2(39%), 453.1(63%), 454.1(100%), 456.0(60%)	Not observed		486.4(29%), 487(64%), 488.3(100%), 489.3(35%), 490(64%)
2d	389.1(34%), 390.1(38%), 394.1(52%), 392.1(100%), 394.1(54%)	426.1(9%), 426.9(8%), 428.1(15%), 430.1(11%)	780.0(6%), 781.0(5%), 782.0(12%), 782.4(6%), 783.0(11%), 783.8(4%)	Not observed