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Metallacyclic Phosphine Complexes and Intramolecular Csp3-H Bond Activation -Synthesis, Characterisation and Catalytic Application

Sjövall, Sven LU (2001)
Abstract (Swedish)
Popular Abstract in Swedish

Katalytisk omvandling av enkla kolväten till mer användbara substanser m.h.a. homogena/lösliga komplex av övergångsmetaller är ett mycket viktigt ämnesområde inom metallorganisk kemi. För att förstå hur processen går till har ett stort antal modellföreningar syntetiserats genom åren där man har studerat hur kol-väte eller kol-kol bindningar kan brytas. Man bör notera att dessa bindningar är mycket starka och reaktionströga, d.v.s. dom metallkomplex som bildas efter bindningsbrytning av ett kolväte kan vara termiskt väldigt stabila. Nyligen har det visat sig att dessa termodynamiskt robusta metallkomplex kan med stor fördel användas i andra katalytiska processer än just bara för transformering av... (More)
Popular Abstract in Swedish

Katalytisk omvandling av enkla kolväten till mer användbara substanser m.h.a. homogena/lösliga komplex av övergångsmetaller är ett mycket viktigt ämnesområde inom metallorganisk kemi. För att förstå hur processen går till har ett stort antal modellföreningar syntetiserats genom åren där man har studerat hur kol-väte eller kol-kol bindningar kan brytas. Man bör notera att dessa bindningar är mycket starka och reaktionströga, d.v.s. dom metallkomplex som bildas efter bindningsbrytning av ett kolväte kan vara termiskt väldigt stabila. Nyligen har det visat sig att dessa termodynamiskt robusta metallkomplex kan med stor fördel användas i andra katalytiska processer än just bara för transformering av kolväten och då i synnerhet för sådana reaktioner där höga reaktionstemperaturer krävs.



Föreliggande avhandling är tillägnad detta gränsnitt mellan studium av bindninsbrytning hos kolväte m.h.a. lösliga komplex av övergångsmetaller och applikation av de resulterande komplexen till katalys i allmänhet. Sammanfattningen bygger på de sju bilagda vetenskapliga artiklarna. I dessa artiklar redogörs det bl.a. hur en serie av olika organiska modellmolekyler för att studera bindningsbrytning av en kolvätebindning har syntetiserats. Då inte alla lösliga komplex av övergångsmetaller klarar av att bindningsbryta en kolvätebindning har en omfattande studie genomförts som har etablerat en tydlig trend hur ett lämpligt metallkomplex ska se ut. För vissa av de organiska modellmolekylerna har uppföljande undersökning visat hur bindningsbrytningen sker i detalj. Teoretiska datorberäkningar har genomförts för att förstå varför vissa organiska modellmolekylerna är lämpliga för att studera bindningsbrytning av en kolvätebindning och varför andra väldigt snarlika är direkt olämpliga. Flera av de syntetiserade modellkomplexen har också använts för att undersöka den välkända katalytiska reaktionen mellan arylhalider och alkener. Under de mest optimala reaktionsbetingelserna kan över 1 miljon produktmolekyler syntetiseras per katalysatormolekyl. Detta faktum, tillsammans med andra observationer i denna avhandling och andra publicerade forskningsresultat, borde snart göra det möjligt att kommersiellt utnyttja denna reaktion. (Less)
Abstract
The work presented in this thesis deals with metallacyclic late transition metal complexes, obtained by intramolecular Csp3-H activation, and the application of such compounds in catalysis. The new hemilabile P,O phosphines N-methyl-N-propionyl-2-(diphenylphosphino)benzylamine (DPPAM), o-(diphenylphosphino)benzoic acid ethyl ester (DPPES), o-(diphenylphosphino)benzoic acid methyl ether (DPPET) and ±-1-(2- diphenylphosphino)phenylethyl propionate (±-DPPMES) and the symmetrical diphosphorus donor ligands cis-1,3-bis[(diphenylphosphino)methyl]-cyclohexane (DPCY), cis-1,3-bis[(di-tertbutylphosphino)methyl]cyclohexane (DTBCY) and cis-1,3-bis[(di-isopropylphosphino)methyl]cyclohexane (DIPCY) have been synthesised, allowing the preparation of a... (More)
The work presented in this thesis deals with metallacyclic late transition metal complexes, obtained by intramolecular Csp3-H activation, and the application of such compounds in catalysis. The new hemilabile P,O phosphines N-methyl-N-propionyl-2-(diphenylphosphino)benzylamine (DPPAM), o-(diphenylphosphino)benzoic acid ethyl ester (DPPES), o-(diphenylphosphino)benzoic acid methyl ether (DPPET) and ±-1-(2- diphenylphosphino)phenylethyl propionate (±-DPPMES) and the symmetrical diphosphorus donor ligands cis-1,3-bis[(diphenylphosphino)methyl]-cyclohexane (DPCY), cis-1,3-bis[(di-tertbutylphosphino)methyl]cyclohexane (DTBCY) and cis-1,3-bis[(di-isopropylphosphino)methyl]cyclohexane (DIPCY) have been synthesised, allowing the preparation of a range of new metallacyclic rhodium(III), iridium(III) and palladium(II) complexes.



DPPAM, DPPES and DPPET are all capable of intramolecular Csp3-H activation in iridium chemistry, while only the two former can cyclometallate in rhodium chemistry. It is clear that a transition metal from the third row, coordinating electron-releasing spectator ligands and is capable of P,O ring closure is the optimal candidate for insertion into a C-H bond in these ligands. A kinetic investigation of the coordination chemistry of the DPPAM ligand suggests that the oxidative addition of the Csp3-H bond takes place in the plane of the complex via a 14-electron, highly coordinatively unsaturated intermediate. For the ±-DPPMES ligand, which also is set-up for Csp3-Csp3 activation, Csp3-H activation is kinetically preferred, resulting in the first example of transition metal complex capable of breaking a tertiary C-H bond at room temperature. However, if the metal complex coordinating the ±-DPPMES ligand can not achieve a highly coordinatively unsaturated state competing Csp3-O activation occurs, probably as an SN2 reaction.



Of the three diphosphorus donor ligands DPCY, DTBCY and DIPCY, only DTBCY is capable of Csp3-H activation at an electrophilic palladium centre, thus coordinating in a tridentate PCP mer fashion. The other two are coordinated either as a monomeric cis-(P~P)PdII adduct or as a dimeric trans-((P~P)PdII)2 adduct. Density functional modelling of the free ligands suggests that they would have to build up various degrees of strain in order to arrange the candidate Csp3-H bond in the optimal side-on fashion in respect to the metal centre. In the case of the less sterically demanding DPCY and DIPCY ligands, the cyclohexane back bone of the ligand, rather than building up this strain, inverts from diequatorial to diaxial configuration, efficiently suppressing the possibility of C-H activation.



The synthesised complexes [Pd(DPCY)(CO2CF3)2] (15) and [Pd(DTBCY) CO2CF3] (16) are highly efficient as catalyst precursors in the olefination of aryl halides. The arylation of methylacrylate with iodobenzene mediated by complex 15 resulted in a turnover number of 1,176, 000 and a mean turnover frequency of 11, 760 h-1, thus 15 is the most efficient diphosphine-palladium(II) precatalyst reported. The key feature of complex 15 is the labile 8-membered chelate, facilitating de-chelation of the catalyst during the catalytic cycle. The catalytic activity of the tridentate PCsp3P complex 16 was shown to be lower than that of 15. However, 16 is very robust and can be recovered unchanged after catalysis. By comparing with the analogous previously reported PCsp2P PdII precatalyst, it is clear that by changing the central carbon donor atom from sp2 to sp3 hybridisation the catalytic efficiency is increased. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof Braunstein, Pierre, Strasbourg, France
organization
publishing date
type
Thesis
publication status
published
subject
keywords
catalysis, Heck, diphosphite, diphosphine, phosphine, cyclometallation, C-C activation, C-O activation, C-H activation, palladium, rhodium, iridium, Inorganic chemistry, Oorganisk kemi
pages
156 pages
publisher
Sven Sjövall, Inorganic Chemistry, Chemical Center, Lund University
defense location
Lecture hall F, Chemical Center
defense date
2001-10-12 15:15
ISBN
91-628-4981-6
language
English
LU publication?
yes
id
606253ff-74cf-4140-bd04-add060355725 (old id 41893)
date added to LUP
2007-10-14 16:47:10
date last changed
2016-09-19 08:45:07
@misc{606253ff-74cf-4140-bd04-add060355725,
  abstract     = {The work presented in this thesis deals with metallacyclic late transition metal complexes, obtained by intramolecular Csp3-H activation, and the application of such compounds in catalysis. The new hemilabile P,O phosphines N-methyl-N-propionyl-2-(diphenylphosphino)benzylamine (DPPAM), o-(diphenylphosphino)benzoic acid ethyl ester (DPPES), o-(diphenylphosphino)benzoic acid methyl ether (DPPET) and ±-1-(2- diphenylphosphino)phenylethyl propionate (±-DPPMES) and the symmetrical diphosphorus donor ligands cis-1,3-bis[(diphenylphosphino)methyl]-cyclohexane (DPCY), cis-1,3-bis[(di-tertbutylphosphino)methyl]cyclohexane (DTBCY) and cis-1,3-bis[(di-isopropylphosphino)methyl]cyclohexane (DIPCY) have been synthesised, allowing the preparation of a range of new metallacyclic rhodium(III), iridium(III) and palladium(II) complexes.<br/><br>
<br/><br>
DPPAM, DPPES and DPPET are all capable of intramolecular Csp3-H activation in iridium chemistry, while only the two former can cyclometallate in rhodium chemistry. It is clear that a transition metal from the third row, coordinating electron-releasing spectator ligands and is capable of P,O ring closure is the optimal candidate for insertion into a C-H bond in these ligands. A kinetic investigation of the coordination chemistry of the DPPAM ligand suggests that the oxidative addition of the Csp3-H bond takes place in the plane of the complex via a 14-electron, highly coordinatively unsaturated intermediate. For the ±-DPPMES ligand, which also is set-up for Csp3-Csp3 activation, Csp3-H activation is kinetically preferred, resulting in the first example of transition metal complex capable of breaking a tertiary C-H bond at room temperature. However, if the metal complex coordinating the ±-DPPMES ligand can not achieve a highly coordinatively unsaturated state competing Csp3-O activation occurs, probably as an SN2 reaction.<br/><br>
<br/><br>
Of the three diphosphorus donor ligands DPCY, DTBCY and DIPCY, only DTBCY is capable of Csp3-H activation at an electrophilic palladium centre, thus coordinating in a tridentate PCP mer fashion. The other two are coordinated either as a monomeric cis-(P~P)PdII adduct or as a dimeric trans-((P~P)PdII)2 adduct. Density functional modelling of the free ligands suggests that they would have to build up various degrees of strain in order to arrange the candidate Csp3-H bond in the optimal side-on fashion in respect to the metal centre. In the case of the less sterically demanding DPCY and DIPCY ligands, the cyclohexane back bone of the ligand, rather than building up this strain, inverts from diequatorial to diaxial configuration, efficiently suppressing the possibility of C-H activation.<br/><br>
<br/><br>
The synthesised complexes [Pd(DPCY)(CO2CF3)2] (15) and [Pd(DTBCY) CO2CF3] (16) are highly efficient as catalyst precursors in the olefination of aryl halides. The arylation of methylacrylate with iodobenzene mediated by complex 15 resulted in a turnover number of 1,176, 000 and a mean turnover frequency of 11, 760 h-1, thus 15 is the most efficient diphosphine-palladium(II) precatalyst reported. The key feature of complex 15 is the labile 8-membered chelate, facilitating de-chelation of the catalyst during the catalytic cycle. The catalytic activity of the tridentate PCsp3P complex 16 was shown to be lower than that of 15. However, 16 is very robust and can be recovered unchanged after catalysis. By comparing with the analogous previously reported PCsp2P PdII precatalyst, it is clear that by changing the central carbon donor atom from sp2 to sp3 hybridisation the catalytic efficiency is increased.},
  author       = {Sjövall, Sven},
  isbn         = {91-628-4981-6},
  keyword      = {catalysis,Heck,diphosphite,diphosphine,phosphine,cyclometallation,C-C activation,C-O activation,C-H activation,palladium,rhodium,iridium,Inorganic chemistry,Oorganisk kemi},
  language     = {eng},
  pages        = {156},
  publisher    = {ARRAY(0xa86eac0)},
  title        = {Metallacyclic Phosphine Complexes and Intramolecular Csp3-H Bond Activation -Synthesis, Characterisation and Catalytic Application},
  year         = {2001},
}