Reactivity of Silanes with (^tBuPONOP)Ruthenium Dichloride: Facile Synthesis of Chloro‐Silyl Ruthenium Compounds and Formic Acid Decomposition

Abstract

The coordination of PONOP ( PONOP=2,6-bis(ditert-butylphosphinito)pyridine) to different ruthenium starting materials, to generate ( PONOP)RuCl , was investigated. The resultant ( PONOP)RuCl reactivity with three different silanes was then investigated and contrasted dramatically with the reactivity of ( PONOP)RuCl (DMSO) ( PONOP=2,6-bis(diisopropylphosphinito)pyridine) with the same silanes. The 16-electron species ( PONOP)Ru(H)Cl was produced from the reaction of triethylsilane with ( PONOP)RuCl . Reactions of ( PONOP)RuCl with both phenylsilane or diphenylsilane afforded the 16-electron hydrido-silyl species ( PONOP)Ru(H)(PhSiCl ) and ( PONOP)Ru(H)(Ph SiCl), respectively. Reactions of all three of these complexes with silver triflate afforded the simple salt metathesis products of ( PONOP)Ru(H)(OTf), ( PONOP)Ru(H)(PhSiCl(OTf)), and ( PONOP)Ru(H)(Ph Si(OTf)). Formic acid dehydrogenation was performed in the presence of triethylamine (TEA), and each species proved competent for gas-pressure generation of CO and H . The hydride species ( PONOP)Ru(H)Cl, ( PONOP)Ru(H)(OTf), and ( PONOP)Ru(H)(PhSiCl ) exhibited faster catalytic activity than the other compounds tested.

Manganese‐Mediated Formic Acid Dehydrogenation

“…Iridium and ruthenium catalysts have shown the most promise for expedient dehydrogenation of FA, with iridium systems capable of handling either aqueous or, importantly, neat conditions. Our previous report of a base‐assisted ( t Bu PONOP)RuHCl ( 6 ) catalyst exhibited high TOFs, generating hundreds of PSI of pressure in the desired short reaction times ( t Bu PONOP=2,6‐bis(di‐ tert ‐butylphosphinito)pyridine) under high FA concentrations (Figure ) . This is in contrast to a separate report exploring FA reactivity with ( t Bu PNNNP)Ru complexes requiring slow addition of FA to the catalyst solution ( t Bu PNNNP=2,6‐bis (di tert butylphosphinamine)pyridine) .…”

“…Ourp revious report of ab ase-assisted ( tBu PONOP)RuHCl (6)c atalyste xhibited high TOFs, generating hundreds of PSI of pressure in the desired short reaction times ( tBu PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine) under high FA concentrations (Figure 1). [14] Thisi si nc ontrast to as eparate report exploring FA reactivity with ( tBu PNNNP)Ru complexes requiring slow addition of FA to the catalysts olution ( tBu PNNNP = 2,6-bis (ditertbutylphosphinamine)pyridine). [15] Sizeable interesti na dopting base-metalc atalysts remains, and this work we represents as ignificant development for manganese as robust catalysts for FA dehydrogenation.Herein we report the synthesis of tBu PNNOP (1, tBu PNNOP = 2,6-(di-tert-butylphosphinito)(di-tert-butylphosphinamine)pyridine)), in order to marry the single chemically noninnocent moiety (NÀH) of PNP ligands with the steric and geometric properties of tBu PONOP,r epresenting an alternate ligand motif with which to explore transition-metalc hemistry.T he hybrid backbone tBu PNNOP-chelate of [Mn(CO) 2 ] + was shown to be highly reactive as aF Ad ehydrogenation catalysta sc ompared to the comparablep arentb ackbone ( tBu PONOP, tBu PNNNP) chelate-supportedc omplexes.…”

“…Ourp revious report of ab ase-assisted ( tBu PONOP)RuHCl (6)c atalyste xhibited high TOFs, generating hundreds of PSI of pressure in the desired short reaction times ( tBu PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine) under high FA concentrations ( Figure 1). [14] Thisi si nc ontrast to as eparate report exploring FA reactivity with ( tBu PNNNP)Ru complexes requiring slow addition of FA to the catalysts olution ( tBu PNNNP = 2,6-bis (ditertbutylphosphinamine)pyridine). [15] Sizeable interesti na dopting base-metalc atalysts remains, and this work we represents as ignificant development for manganese as robust catalysts for FA dehydrogenation.…”

“…Chem.E ur.J.2019, 25,10557 -10560 www.chemeurj.org served with 6. [14] With 0.5equivalents of TEA, initial catalysis was sluggish until the TEA/FAr atio reached an optimum ratio and catalysis became rapid ( Figure 3D). The identityo ft he base does not significantly alter catalytic results (Table 1, entries 10-12).…”

“…Attempted catalysis with 2 (0.5 mol %) in 4mLC 6 H 5 Cl with 1mLF Aa t8 08Cr esulted in little generationo fg as pressure. Few FA decomposition catalysts proceed withoutt he addition of base, [18] and as base effects figuredp rominently in the catalysis of 6, [14] ab ase study was conducted with 2 by using 0.5, 1.0, and 1.5 equivalents of triethylamine (TEA) to FA (Table 1, entries 7-9;F igure 3D), with one equivalent giving the most rapid catalysis, ar esult also ob-Scheme1. Description of the:a)synthesis of 1,b)synthesis of 2,and c) synthesis of 3.…”