Mechanistic insight into the ruthenium-catalysed anti-Markovnikov hydration of alkynes using a self-assembled complex: A crucial role for ligand-assisted proton shuttle processes

TY - JOUR

T1 - Mechanistic insight into the ruthenium-catalysed anti-Markovnikov hydration of alkynes using a self-assembled complex

T2 - A crucial role for ligand-assisted proton shuttle processes

AU - Breit, Bernhard

AU - Gellrich, Urs

AU - Li, Timothy

AU - Lynam, Jason M.

AU - Milner, Lucy M.

AU - Pridmore, Natalie E.

AU - Slattery, John M.

AU - Whitwood, Adrian C.

PY - 2014

Y1 - 2014

N2 - A combined computational and experimental study is presented that investigates the mechanism of the anti-Markovnikov hydration of phenylacetylene by [Ru(η5-C5H5)(6-DPPAP)(3-DPICon)] + (where 6-DPPAP = 6-(diphenylphosphino)-N-pivaloyl-2-aminopyridine) and 3-DPICon = 3-diphenylphosphinoisoquinolone). The proposed mechanism, modelled using density functional calculations, involves an initial alkyne-vinylidene tautomerism, which occurs via a ligand-assisted proton shuttle (LAPS) mechanism. Intramolecular ligand assistance from the 6-DPPAP and 3-DPICon ligands, particularly the basic nitrogen of 6-DPPAP, is also involved in subsequent stages of the mechanism and three LAPS processes in total are observed. The self-assembled ligand backbone helps to create a water-binding pocket close to the metal centre, which facilitates nucleophilic attack of water at the vinylidene α-carbon and mediates protonation and deprotonation of subsequent acyl and vinyl intermediates. Experimental evidence is also presented for a novel non-productive catalyst deactivation pathway, which appears to arise from an initial lactam-lactim tautomerism of the 3-DPICon ligand followed by coupling with a vinylidene. This journal is

AB - A combined computational and experimental study is presented that investigates the mechanism of the anti-Markovnikov hydration of phenylacetylene by [Ru(η5-C5H5)(6-DPPAP)(3-DPICon)] + (where 6-DPPAP = 6-(diphenylphosphino)-N-pivaloyl-2-aminopyridine) and 3-DPICon = 3-diphenylphosphinoisoquinolone). The proposed mechanism, modelled using density functional calculations, involves an initial alkyne-vinylidene tautomerism, which occurs via a ligand-assisted proton shuttle (LAPS) mechanism. Intramolecular ligand assistance from the 6-DPPAP and 3-DPICon ligands, particularly the basic nitrogen of 6-DPPAP, is also involved in subsequent stages of the mechanism and three LAPS processes in total are observed. The self-assembled ligand backbone helps to create a water-binding pocket close to the metal centre, which facilitates nucleophilic attack of water at the vinylidene α-carbon and mediates protonation and deprotonation of subsequent acyl and vinyl intermediates. Experimental evidence is also presented for a novel non-productive catalyst deactivation pathway, which appears to arise from an initial lactam-lactim tautomerism of the 3-DPICon ligand followed by coupling with a vinylidene. This journal is

UR - http://www.scopus.com/inward/record.url?scp=84903825113&partnerID=8YFLogxK

U2 - 10.1039/c4dt00712c

DO - 10.1039/c4dt00712c

M3 - Article

AN - SCOPUS:84903825113

SN - 1477-9226

VL - 43

SP - 11277

EP - 11285

JO - Dalton Transactions

JF - Dalton Transactions

ER -