Synthesis of Phenanthroline-Bridged Siloxane

3,8-Dibromo-1,10-phenanthroline (1.49 g, 4.4 mmol) and a stirring bar were placed in an autoclave (125 mL) with a PTFE inner vessel and Ni(dppp)Cl₂ (138 mg, 6 mol%) and THF (50 mL) were gradually added. A THF solution of (iPrO)₃SiCH₂MgCl (12.5 mmol) was added dropwise over 3 min under continuous stirring. The autoclave was sealed and stirred at room temperature for 1 h, and then heated to 140 °C. After 17 h, the mixture was cooled to room temperature and then quenched with water. The mixture was extracted with CHCl₃ and the organic layer was washed with brine and dried over Na₂SO₄. The solvents were removed by rotary evaporator. The crude product was dissolved in n-hexane and stirred for 15 min. The mixture was filtered through a Celite pad and the solvent was removed by rotary evaporator. The crude product was purified by silica gel column chromatography (n-hexane/AcOEt) to give the Phen-PMO precursor, 3,8-bis[(triisopropoxysilyl)methyl]-1,10-phenanthroline (1a), as a pale-yellow solid (1.11 g, 41%). ¹H NMR (600 MHz, CDCl₃): δ 9.00 (d, J = 2.1 Hz, 2H), 8.00 (d, J = 2.1 Hz, 2H), 7.65 (s, 2H), 4.21 (sept, J = 6.1 Hz, 6H), 2.36 (s, 4H), 1.15 ppm (d, J = 6.1 Hz, 36H). ¹³C{¹H} NMR (151 MHz, CDCl₃): δ 151.9, 143.9, 134.8, 133.4, 127.9, 126.2, 65.7, 25.7, 19.6 ppm. ²⁹Si{¹H} NMR (119 MHz, CDCl₃): δ −56.5 ppm. Anal. calcd for C₃₂H₅₂N₂O₆Si₂: C, 62.30; H, 8.50; N, 4.54. Found: C, 62.30; H, 8.90; N, 4.50.