Synthesis and Purification of Ruthenium(II) Bipyridine Complex

[(p-Cymene)Ru(4,4′-dhbpy)Cl]Cl
(0.100 g, 0.201 mmol) and 4,4′-bis(dipropylamido)-2,2′-bipyridine
(0.132 g, 0.404 mmol) were dissolved in 5 mL amine-free N,N-dimethylformamide (dried over 3 Å molecular
sieves). The mixture was degassed for 20 min prior to refluxing for
4 h under nitrogen atmosphere. Once cooled, excess acetone was added,
and the mixture was cooled in the freezer overnight. The precipitated
product, [(dpab)₂Ru(4,4′-dhbpy)]Cl₂,
was collected on a fine fritted filter. The complex was precipitated
as the hexafluorophosphate salt by addition of a molar excess of aqueous
ammonium hexafluorophosphate to an aqueous solution of the product.
[(dpab)₂Ru(4,4′-dhbpy)](PF₆)₂ was purified to remove the predominant impurity [Ru(dpab)₃](PF₆)₂ using column chromatography. The crude
product was added to an alumina column with an eluent of 5% methanol
in dichloromethane. The desired product remained unmovable with this
eluent mixture, but the [Ru(dpab)₃](PF₆)₂ was quickly removed from the column. A secondary eluent mixture
was added, 1:1 H₂O and acetonitrile. The desired product
was successfully removed from the column yielding 0.070 g (28%). The
product was characterized by ¹H NMR, ¹³CNMR,
COSY, and ESI-MS (Figure.S1). ¹H NMR (300 MHz, CD₃CN, residual internal (CD₂H)CN δ 1.94 ppm) δ 8.91 (s, 4H), 7.98 (d, J = 5.9 Hz, 2H), 7.82 (d, J = 6.0 Hz, 2H), 7.74 (d, J = 5.8 Hz, 2H), 7.70–7.59 (m, 6H), 7.52 (s, 2H),
7.17 (d, J = 6.4 Hz, 2H), 6.72 (d, J = 6.5 Hz, 2H), 3.37 (m, J = 14.4, 6.8 Hz, 9H),
1.62 (m, J = 7.5 Hz, 8H), 0.95 (q, J = 7.1 Hz, 12H).