Papers by Martin J Hanton
Journal of Molecular Catalysis A: Chemical, 2011
The synthesis of a new tripodal phosphine ligand, N(CH 2 PEt 2 ) 3 , N-TriPhos Et is reported, an... more The synthesis of a new tripodal phosphine ligand, N(CH 2 PEt 2 ) 3 , N-TriPhos Et is reported, and the use of tripodal ligands of this type, N(CH 2 PR 2 ) 3 (R = Ph, Et), in conjunction with ruthenium for the catalysed hydrogenation of dimethyl oxalate (DMO) is reported and contrasted with catalysis using the MeC(CH 2 PPh 2 ) 3 (TriPhos Ph ) ligand. A different order of reaction with respect to the DMO substrate is found, and the rate is slower. A study of the kinetics and mechanism of the hydrogenation of DMO with Ru(acac) 3 /TriPhos Ph is described, along with the effect of different additives to the system. The performance of Ru(acac) 3 /TriPhos Ph /Zn system with unactivated ester substrates is probed and found to proceed significantly slower. Finally, based upon experimental observations, a mechanism is proposed for ester hydrogenation using ruthenium catalysts with tripodal phosphine ligands.
…, Jan 1, 2007
The use of N-heterocyclic carbenes (NHCs) in catalytic transition metal systems has been an activ... more The use of N-heterocyclic carbenes (NHCs) in catalytic transition metal systems has been an active area of research over the last decade. 1 The most successful applications are in the metathesis (Ru catalyst) and C−C coupling (Pd catalyst) reactions. 2 Polydentate NHC ligands in ...
Physical Chemistry Chemical Physics - PHYS CHEM CHEM PHYS, 1999
Organometallics, 2009
ABSTRACT This report examines the replacement of the imine and pyridine functionalities of the ub... more ABSTRACT This report examines the replacement of the imine and pyridine functionalities of the ubiquitous bis(imino)pyridine ligand with various heterocycles. The synthesis of a new class of ligand based around thiazole is described; 2,4-bis[1-(arylimino)ethyl]thiazole (aryl = Ph, 1a; Dipp, 1b) and 2,5-bis[1-(arylimino)ethyl]thiazole (aryl = Ph, 1c; Dipp, 1d) have been prepared in good yield and fully characterized. The coordination chemistry of these ligands with chromium, iron, and cobalt is explored, and the potential of these complexes as ethylene oligomerization initiators is assessed. The chromium complex 2a shows an extremely unusual alternating distribution of higher α-olefin products, which has been previously observed on only one occasion. Both series of products, C4n and C4n+2, show Schulz−Flory behavior but with distinctly different k values. The new ligand 2,5-bis[1-(phenylimino)ethyl]-1-methylpyrrole (1e) is reported along with the attempted synthesis of some corresponding iron complexes. The complexation of chromium by 2,5-bis(phenyliminomethyl)thiophene (1f) is also described, and this material was screened for ethylene oligomerization activity, detailed studies indicating that the ligand may be labile under catalytic conditions. A number of other known heterocyclic ligands incorporating pyrazolyl and benzimidazole functionalities have also been explored with iron, and for the first time their potential to facilitate ethylene oligomerization was assessed. All complexes have been tested via activation with MMAO-3A and AlEt3/[Ph3C][Al(OtBuF)4].
Organometallics, 2008
ABSTRACT The use of AlEt3 (TEA) in combination with [Ph3C][Al(OtBuF)4] (TA) for the activation of... more ABSTRACT The use of AlEt3 (TEA) in combination with [Ph3C][Al(OtBuF)4] (TA) for the activation of a range of bis(imino)pyridine complexes of vanadium, chromium, iron, and cobalt is reported. It is shown that this activator combination successfully replaces MMAO, in some cases showing improvements in terms of activity and productivity. Furthermore, when activities and productivities are considered in terms of the aluminum center (MMAO vs TEA), the true cost driver in the commercialization of most catalyst systems, then in nearly all cases a significant improvement is seen.
Organometallics, 2007
... Robert P. Tooze, † Alexandra MZ Slawin, ‡ Jérémie DA Pelletier, † Martin J. Hanton,* † and Pa... more ... Robert P. Tooze, † Alexandra MZ Slawin, ‡ Jérémie DA Pelletier, † Martin J. Hanton,* † and Paul B. Webb †. Sasol Technology (UK) Ltd., Purdie Building, North Haugh, St. Andrews, KY16 9ST, UK, and School of Chemistry, University of St. Andrews, Purdie Building, St. ...
Dalton Transactions, 2013
Scandium trichloride complexes with tridentate N(3)- and S(2)N-donor ligands (L(3)) have been syn... more Scandium trichloride complexes with tridentate N(3)- and S(2)N-donor ligands (L(3)) have been synthesised and characterised by IR, (1)H, (13)C{(1)H} and (45)Sc NMR spectroscopy, microanalysis, and solid state and solution XAFS spectroscopy. Catalytic testing of a subset of these complexes with ethene has been undertaken in chlorobenzene with MMAO-3A and PMAO-IP at 60 °C and 40 bar ethene, giving low activity ethene polymerisation. The reactions of these complexes with MeLi and AlMe(3) were studied by (1)H, (13)C{(1)H}, (27)Al and (45)Sc NMR spectroscopy and in situ via Sc K-edge XAFS spectroscopy. Three or four mol. equivalents of MeLi react with [ScCl(3)(Me(3)-tacn)] in THF solution to form [ScMe(3)(Me(3)-tacn)] cleanly, while complexes of type [ScCl(3)(R-SNS)] {R-SNS = HN(CH(2)CH(2)SC(10)H(21))(2)} form two different species proposed to be [ScMe(3)(R-SN(Li)S)] and [ScMe(2)(R-SN(-)S)]. In contrast, in situ(45)Sc NMR and Sc K-edge XAFS spectroscopic studies of the reaction of [ScCl(3)(Me(3)-tacn)] with 10 mol. equivalents of AlMe(3) strongly suggest that alkylation at the Sc(III) centre does not occur, instead retaining the Cl(3)N(3) coordination environment and most likely forming Sc-Cl-AlMe(3) bridging interactions. Similar studies on [ScCl(3)(decyl-SNS)] with 10 mol. equivalents of AlMe(3) are also consistent with this, indicating that alkylation at the Sc centre does not occur except in the presence of co-catalyst [Ph(3)C][Al{OC(CF(3))(3)}(4)] and the α-alkene, hex-1-ene.
Dalton Trans., 2016
9-Amino-9-phosphabicyclo[3.3.1]nonanes, (PhobPNHR&amp... more 9-Amino-9-phosphabicyclo[3.3.1]nonanes, (PhobPNHR'; R = Me or (i)Pr) are readily prepared by aminolysis of PhobPCl and are significantly less susceptible to hydrolysis than the acyclic analogues Cy2PNHR'. Treatment of Cy2PNHMe with Cy2PCl readily gave Cy2PNMePCy2. By contrast, treatment of PhobPCl with PhobPNHMe in the presence of Et3N does not afford PhobPNMePPhob but instead the salt [PhobP([double bond, length as m-dash]NMeH)PPhob]Cl is formed which, upon addition of [PtCl2(NC(t)Bu)2] gives the zwitterionic complex [PtCl3(PhobP([double bond, length as m-dash]NMeH)PPhob)]. The neutral PhobP([double bond, length as m-dash]NMe)PPhob is accessible from PhobNMeLi and is converted to the chelate [PdCl2(PhobPNMePPhob)] by addition of [PdCl2(cod)]. The anomalous preference of the PhobP group for the formation of PPN products is discussed. The unsymmetrical diphos ligands PhobPNMePAr2 (Ar = Ph, o-Tol) are prepared, converted to [Cr(CO)4(PhobPNMePAr2)] and shown to form Cr-catalysts for ethene oligomerisation, producing a pattern of higher alkenes that corresponds to a Schulz-Flory distribution overlaid on selective tri/tetramerisation.
New Journal of Chemistry, 2010
The new ambiphilic ligand Ph 2 P-(1,1 0 -ferrocenyl)-BMes 2 , prepared by sequential lithiation/e... more The new ambiphilic ligand Ph 2 P-(1,1 0 -ferrocenyl)-BMes 2 , prepared by sequential lithiation/electrophilic trapping of 1,1 0 -dibromoferrocene, adopts a monomeric structure free of dative P -B and Fe -B interactions. This flexible phosphineborane and the related o-phenylene bridged system have been evaluated in Rh-catalyzed hydroformylation.
Organometallics, 2012
The chromium(III) complexes of the type L 1 CrXY (L 1 = 1-(2,6-diisopropylphenyl)-3-[β-(4,7-dimet... more The chromium(III) complexes of the type L 1 CrXY (L 1 = 1-(2,6-diisopropylphenyl)-3-[β-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidene, X, Y = Cl, 2a-Cl; X = Cl, Y = Me, 2a-Me; X = Cl, Y = Ph, 2a-Ph; X, Y = benzyl, 2a-Bz) and L 2 CrCl 2 (L 2 = 1-(2,6-diisopropylphenyl)-3-[γ-(4,7-dimethylindenyl)propyl]-imidazol-2-ylidene, 2b-Cl) have been prepared and characterized by analytical and diffraction methods. The salts [L 1 CrCl(THF)] + [BAr F 4 ] − and [L 2 CrCl(THF)] + [BAr F 4 ] − (Ar F = 3,5-bis(trifluoromethyl)phenyl) were also characterized, having been obtained by abstraction of chloride, or indirectly a methyl, from 2a-Cl or 2a-Me, and 2b-Cl, by NaBAr F 4 , respectively. Reaction of 2a-Bz with 1 equiv of [H(Et 2 O) 2 ][BAr F 4 ] in THF gave the thermally unstable salt [L 1 Cr(Bz)(THF)] + [BAr F 4 ], [2a-Bz] + [BAr F 4 ]
Organometallics, 2009
... 5. Overett, MJ; Blann, K.; Bollmann, A.; de Villiers, R.; Dixon, JT; Killian, E.; Maumela, MC... more ... 5. Overett, MJ; Blann, K.; Bollmann, A.; de Villiers, R.; Dixon, JT; Killian, E.; Maumela, MC; Maumela, H ... Atanas K. Tomov, Juan J. Chirinos, Richard J. Long, Vernon C. Gibson, and Mark RJ Elsegood. Journal of the American Chemical Society 2006 128 (24), pp 77047705. ...
Organometallics, 2004
In this context, the Grubbs first-generation catalyst 1 is generally incompatible with olefin fee... more In this context, the Grubbs first-generation catalyst 1 is generally incompatible with olefin feedstocks derived from Fischer−Tropsch 7 conversion of synthesis gas, since it displays poor thermal stability and short lifetimes at low catalyst loadings. For example, complex 1 has a lifetime of only ...
Organometallics, 2007
ABSTRACT Dimethylindenyl-functionalized N-heterocyclic carbene complexes of titanium(IV), titaniu... more ABSTRACT Dimethylindenyl-functionalized N-heterocyclic carbene complexes of titanium(IV), titanium(III), zirconium(IV), and vanadium(III) were prepared from potassium indenylcarbenes by salt elimination reactions. X-ray diffraction studies revealed that in the complexes the ligand adopts a bidentate coordination mode. Alkanolysis of a dimethylindene-functionalized imidazolium salt with Y(CH2SiMe3)3(THF)2 gave rise to a dimeric yttrium bromo alkyl in which the ligand adopts a bidentate coodination mode. Aminolysis of the fluorene-functionalized imidazolium salts with {[Cr(N(SiMe3)2)2(THF)2} led to chromium(II) complexes in which the ligand adopts a monodentate binding mode via the N-heterocyclic carbene end with dangling fluorene groups.
Organometallics, 2009
ABSTRACT
Organometallics, 2013
The synthesis and full characterization of the unprecedented open-shell Cr(II) benzyl organometal... more The synthesis and full characterization of the unprecedented open-shell Cr(II) benzyl organometallic complexes [Cr(NHC) 2 (benzyl) 2 ] (2) and [Cr(NHC*)(benzyl) 2 ] (3) (NHC = N,N′-diisopropylimidazol-2-ylidene; NHC* = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) from [Cr(benzyl) 3 (THF) 3 ] and [CrCl 2 (THF) 2 ]/[Mg(benzyl) 2 ], respectively, uncovered unusually acute angles (93°in 2 and 76°in 3) at the sp 3 benzylic C of the coordinated benzyl ligands. Detailed theoretical analyses (DFT and CASPT2) of the four-and three-coordinate Cr(II) species were performed to elucidate the physical origin of the benzyl bending and led to the recognition of a noncovalent, intramolecular polarization-induced metal−arene (PIMA) interaction as being responsible for it. The energetic contribution from a single PIMA interaction is estimated to be ca. 50 kJ/mol. A comparison with the origin of the angular distortions in the d 0 [Zr(benzyl) 4 ] complex will also be presented. Sharing the common origin of an induced-dipole charge density scheme with intermolecular anion−π interactions, the intramolecular PIMA interaction concept involving a transition metal unpaired d electron and arene−π orbitals can be viewed as an extension of intermolecular anion−π interactions and leads to remarkable quantitative prediction of the observed structural distortions. PIMA interactions may manifest themselves in diverse structural and dynamic phenomena and have broad implications in chemical sciences.
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Papers by Martin J Hanton