Characterisation of 1
Mp 250.4 °C. ¹H NMR (C6D6, 400.13 MHz), d 1.85 (s, 6H), 1.68 (s, 6H), 0.85 (s, 9H), 0.42 (s, 6H); ¹³C{¹H} NMR (C6D6, 100.61 MHz,), d 84.92 (C_ortho), 84.19 (C_meta), 67.02 (C_ipso), 27.27 [C-(CH₃)₃], 20.11 [C-(CH₃)₃], 14.09 (C_ortho-CH₃), 10.89 (C_meta-CH₃), -1.35 (Si-CH₃); ²⁹Si{¹H} NMR (C7D8, 79.49 MHz), d 4.22;[Solution NMR, ¹H-¹H NOESY Spectrum, ¹³C-¹H COLOC Spectrum] ¹³C CP MAS NMR (100.61 MHz), d 85 (C_ortho), 84 (C_meta), 65 (C_ipso), 28 [C-(CH₃)₃], 20 [C-(CH₃)₃], 13 (C-CH₃), -1 (Si-CH₃); ²⁹Si CP MAS NMR (79.49 MHz), d -4.[Solid-State NMR] EI MS: M^+. m/z 526 (100 %), M^+.-Bu^t m/z 469 (13 %). Elemental analysis for C₃₀H₅₄Si₂Fe: C, 68.29(68.40); H, 10.4(10.33%).

Crystal structure data for 1
The structure was solved by direct methods and refined on F² by the full-matrix least-squares procedure. For C₃₀H₅₄Si₂Fe: T = 173(2) K. Specimen 0.3 ´ 0.3 ´ 0.1 mm, M = 526.8, orthorhombic, spacegroup Pnnm (No. 58), a = 7.969(9), b = 13.957(9), c = 13.448(4)Å, V = 1496(2) ų, D_calc = 1.17 g cm^-3, Z = 2. For reflections with 2 £ q £ 25, R(F) = 0.108 for 826 observed reflections [I > 2s(I)] and wR(F²) = 0.311 for all 1383 [R(int) = 0.0000] reflections.

Preparation of 2
A Schlenk tube containing Li{h-C₅Me₄( SiPh₂Cl)} (7.30 g, 21.60 mmol) in thf (100 ml) was cooled to -78 ° C and to it was added with stirring over a 30 minute period LiBu^t (1.7 mol dm^-3 in pentane, 21.60 mmol). After 1 h stirring, FeCl₂ (1.00 g, 7.90 mmol) in thf (20 ml). After a further 1 h stirring, the solution was allowed to warm to room temperature, resulting in a colour change from pale green to deep red. The thf was removed in vacuo and the product washed with hexane (2 ´ 50 ml). The product was extracted with hot Et₂O (2 ´ 60 ml). Removal of the Et₂O in vacuo afforded 4 as an orange powder. Yield 70 % (4.05 g, 5.53 mmol).

Characterisation of 2
Mp 227.9 °C. ¹H NMR (C6D6, 300.13 MHz), d 7.50 (10 H), 1.95 (s, 6 H), 1.70 (s, 6 H); ¹³C NMR (C6D6, 75.43 MHz), d 135.80 (Ph-C_ipso), 134.99, 129.78 (Ph-C_para), 127.56, 86.45 (C_ortho), 85.35 (C_meta), 64.53 (C_ipso), 13.25 (C_ortho-CH₃), 10.46 (C_meta-CH₃).Solution NMR EI MS M^+. m/z 730 (43 %), M^+.-SiPh₂Cl m/z 514 (14 %), M^+.-C₅Me₄(SiPh₂Cl) m/z 393 (4 %), M^+.-C₅Me₄(SiPh₂Cl)-Fe m/z 338 (52 %), M^+.-(SiPh₂Cl)₂ m/z 298 (26 %), [SiPh₂Cl]^+. m/z 217 (100 %), [SiPh₂]^+. m/z 183 (21 %), [C₅Me₄]^+. m/z 120 (32 %). Elemental analysis for C₄₂H₄₄Si₂Cl₂Fe.1/4(C₇H₈): C, 69.43(69.63); H, 6.14(6.14%).

Crystal structure data for 2
The structure was solved by direct methods and refined on F² by the full-matrix least-squares procedure. For C₄₂Cl₂H₄₄FeSi₂.1/4(C₇H₈): T = 293(2) K. Specimen 0.25 ´ 0.15 ´ 0.15 mm, M = 754.7, tetragonal, spacegroup P42₁c (No. 114), a = 20.835(3), c = 17.998(4)Å, a = 90° , V = 7813(3) ų, D_calc = 1.28 g cm^-3, Z = 8. For reflections with 2 £ q £ 25, R(F) = 0.067 for 1602 observed reflections [I > 2s(I)] and wR(F²) = 0.122 for all 3751 [R(int) = 0.1396] reflections.

Preparation of 3
A Schlenk tube containing a solution of Li{h-C₅Me₄(SiMe₃)} (1.00 g, 5.00 mmol) in thf (30 ml) was cooled to -78 ° C and to it was added with stirring over a 1 min period FeCl₂ (0.32 g, 2.50 mmol) in thf (20 ml). The solution was allowed to warm to room temperature, resulting in a colour change from green to orange. After a further 2 h stirring, the thf was removed in vacuo and the product extracted with hot toluene (2 ´ 20 ml). Concentration followed by cooling to ca. -28 ° C afforded 2 as orange cubes. Yield 80 % (0.89 g, 2.00 mmol).

Characterisation of 3
Mp 99.5 ° C. ¹H NMR (C₇D₈, 400.13 MHz): d 1.81 [s, 6H], 1.69 [s, 6H], 0.32 [s, 9H]; ¹³C{¹H} NMR (C₇D₈, 100.61 MHz): d 84.54 [C_ortho], 83.64 [C_meta], 68.59 [C_ipso], 13.41 [C_ortho-CH₃], 10.86 [C_meta-CH₃], 2.60 [Si-CH₃]; ²⁹Si{¹H} NMR (C7D8, 79.49 MHz): d -3.07.[Solution NMR] EI MS: M^+. m/z 442 (100 %), M^+.-SiMe₃ m/z 370 (18 %). Elemental analysis for C₂₄H₄₂Si₂Fe: C, 65.19(65.13); H, 9.56(9.56%).

Crystal structure data for 3
The structure was solved by direct methods and refined on F² by the full-matrix least-squares procedure. For C₂₄H₄₂Si₂Fe: T = 293(2) K. Specimen 0.4 ´ 0.3 ´ 0.3 mm, M = 442.6, orthorhombic, spacegroup Cmca (No. 64), a = 14.0660(10), b = 11.661(2), c = 15.3520(10)Å, V = 2518.1(5) ų, D_calc = 1.17 g cm^-3, Z = 4. For reflections with 2 £ q £ 28, R(F) = .038 for 1273 observed reflections [I > 2s(I)] and wR(F²) = 0.099 for all 1580 [R(int) = 0.0342] reflections.

Preparation of 4
A Schlenk tube containing LiC₅Me₄(SiPh₂Me) (0.66 g, 2.04 mmol) in thf (30 ml) was cooled to -78 ° C and to it was added with stirring over a 1 min period FeCl₂ (0.13 g, 1.02 mmol) in thf (20 ml). The solution was allowed to warm to room temperature, resulting in a colour change from green to orange. The thf was removed in vacuo and extracted with hot hexane (2 ´ 20 ml). Removal of the hexane in vacuo and recrystallisation from toluene at ca. -28 ° C afforded 3 as orange prisms. Yield 83 % (0.59 g, 0.85 mmol).

Characterisation of 4
Mp 129.3 °C. ¹H NMR (C7D8, 400.13 MHz): d 7.41 [Ph-H_meta, m, 4H], 7.12 [Ph-H_ortho,para, m, 6H], 1.75 [s, 6 H], 1.63 [s, 6 H], 0.99 [s, 3H]; ¹³C NMR (C7D8, 100.61 MHz): d 139.25 [Ph-C_ipso], 135.89 [Ph-C_meta], 127.84 [Ph-C_ortho], 86.19 [C_ortho], 84.52 [C_meta], 66.60 [C_ipso], 14.07 [C_ortho-CH₃], 10.89 [C_meta-CH₃], 1.39 [Si-CH₃]. ²⁹Si{¹H} NMR (C7D8, 79.49 MHz): d -9.49.[Solution NMR] EI MS: M^+. m/z 690 (0.6 %), M^+.-SiPh₂Me m/z 494 (84 %), [C₅Me₄SiPh₂Me]^+. m/z 318 (73 %), [SiPh₂Me]^+. m/z 197 (100 %), [C₅Me₄]^+. m/z 120 (35 %). Elemental analysis for C₄₄H₅₀Si₂Fe: C, 76.17(76.49); H, 7.20(7.29%).

Crystal structure data for 4
The structure was solved by direct methods and refined on F² by the full-matrix least-squares procedure. For C₄₄H₅₀FeSi₂: T = 180(2) K. Specimen 0.2 ´ 0.2 ´ 0.1 mm, M = 690.87, tetragonal, spacegroup P2₁c (No. 114), a = 20.7120(2), c = 17.97520(10)Å, a = 90° , V = 7711.13(11) ų, D_calc = 1.19 g cm^-3, Z = 8. For reflections with 1.39 £ q £ 22.49, R(F) = 0.0837 for 2741 observed reflections [I > 4s(I)] and wR(F²) = 0.2328 for all 5046 [R(int) = 0.3435] reflections.