Compound 1 2 2a 3 ΧM 1.64 1.42 1.42 1.52 Epc1/ mV -1241 -1599 -1615 -1395 ΔEp1 / mV 92     130 E011/ mV -1195     -1330 ipa1 ~µA 1.4 - b 3.1 1.8 ipa/ipc 0.5     0.5 Epa2/ mV - -1523 -1454 - ipa2µA - 5.8 5.7 - Epa3/ mV - -87 - - ipa3µ - 0.9 - - Epa4/ mV -83 311 376 409 ΔEp4 / mV 79 - 79 81 E014/ mV -123 - 337 369 ipa4 µA 4.6 1.4 2.4 0.5 ipc/ipa 1.0 - 1.0 0.8 Epa5 / mV 28c 858 649 470c ΔEp5 / mV - 104 117 - E015/ mV - 533 591 - ipa5µA - 4.6 7.9 - ipc/ipa - 0.3 0.3 -

a) Data obtained from an experiment conducted at -35ºC. b) Peaks overlap to the extent that they could not be separated. Hence no peak currents are provided for this peak. c) Estimate, real value could not be determined due to overlapping of peaks.

Table 1 : Cyclic voltammetry data obtained from voltammograms (vs FcH/FcH+0) of [(C5H5)2Ti{(C5H4)M(C5H5)}2] with M = Fe (1), Ru (2) and Os (3), measured CH2Cl2/0.1 mol dm-3 [NBu4][B(C6F5)4] at a glassy carbon working electrode at 25ºC and a scan rate of 100 mV s-1. The concentration of the metallocene dichloride complexes was 2.0 mmol dm-3. Atomic electronegativity of the metals, ΧM, is also shown.