TPPMS/3 anilin

The use of water-soluble metal catalysts for the hydrogenation of thiophenes in aqueous biphasic systems has been primarily introduced by Sanchez-Delgado and coworkers at INTEVEP S.A. [61]. The precursors RuHC1(TPPTS)2(L2) (TPPTS=triphenylphosphine trisulfonate L=aniline, 1,2,3,4-tetrahydroquinoline) and RuHC1(TPPMS)2(L2) (TPPMS=triphenylphosphine monosulfonate) were... 

It occurred to us that ionic interactions might be a highly suitable binding motif to enforce the formation of heterobidentate ligand combinations [48[. The assembly ligand 14 /IS has been formed from the well-known TPPMS (14, monosulfonated triphenylphosphine sodium salt) and 3-(diphcnylphosphinyl)aniline hydrochloride (IS) by a simple ion-exchange reaction (Scheme 10.6). The coordination behavior ofthe ion-pair 14 /I S has been tested with various transition metal complexes. Other... 

TPPMS - m-monosulfonated triphenylphosphine. base = aniline Tp hydrotrispyrazolylborates... 

In aqueous/organic biphasic medium the reaction rate for the hydrogenation of linear and cyclic alkenes with several Ru(II) complexes including [HRuCl-(TPPMS)2]2, [HRuC1(TPPMS)2(L)2] and [HRuCl(TPPTS)2(L)2] (L = aniline or tet-rahydroquinoline) followed the order linear C2 f-6 linear C7-C10 > cyclic alkenes > branched alkenes [54]. This reactivity pattern is similar to the case of al-kene hydrogenations with [HRuCl(PPh3)3], i.e., the least-substituted double bonds are hydrogenated the fastest. 

Interestingly, the rate almost quadruples if nitrogen bases such as quinoline (Q) or aniline are used as co-catalysts. This kinetic effect may be due to several beneficial actions by the nitrogen bases on either the catalyst (faster formation and/or better stabilization) or the phase system (stabilization of the emulsion, improved solubility of BT in water). The quality of the emulsion seems to be of particular importance as shown by the fact that TPPTS, which is a worse surfactant than TPPMS, also gives worse catalytic results. Other nitrogen bases such as acridine, tetrahydro-quinoline (THQ), piperidine, and triethylamine give lower conversions to DHBT as compared with analogous reactions co-catalyzed by aniline or quinoline. 

The same reactions are also catalyzed by Ru-TPPMS or Ru-TPPTS catalysts however, under comparable conditions, rather low activity (TOF 2.5 h ) was observed. Addition of nitrogen bases (quinoline, aniline) resulted in significantly increased reaction rates. 

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