A solution of NaBH(OAc)3 (0.17 g, 0.8 mmol) and 4-vinylbenzylamine (0.26 g, 1.95 mmol) in 10 ml of dichloroethane is admixed dropwise at ambient temperature with a solution of 1,2-bis-(diphenylphosphino)-1′-diisopropylphosphino-4-(4-oxo-2-methylbut-2-yl)ferrocene (1.3 g, 1.2 mmol) in 5 ml of dichloroethane. The solution is held with stirring for 24 hours and then neutralized by addition of 1M aqueous sodium hydroxide solution. The aqueous phase is extracted with 2 times 30 ml of dichloromethane. The organic phases are combined, dried over MgSO4, and concentrated under reduced pressure. The crude product obtained is purified by chromatography on silica gel (CH2Cl2/MeOH, 95:5) to give 0.4 g (ρ=55%) of 1,1′,2-tris(diphenylphosphino)-2′-diisopropylphosphino-4-[2-methyl-5-(4-vinylbenzylamino)pent-2-yl]ferrocene in the form of a red-orange powder. The 31P NMR spectrum preserves, as expected, the A2B spin system appearance typical of these triphosphines, as described by Hierso et al. for the nonheterogeneizable analog in Org. Lett. 2004, 6, 3473-3476, with slightly modified chemical shifts.
