Titel Jurca - Academia.edu (original) (raw)
Papers by Titel Jurca
European Journal of Inorganic Chemistry, 2016
Dalton Trans., 2016
The preparation and characterization of a series of divalent 3d transition metal complexes suppor... more The preparation and characterization of a series of divalent 3d transition metal complexes supported by a tridentate planar bis(iminopyridine) ligand are reported. The complexes {2,6-[PhC[double bond, length as m-dash]N(tBu2C6H3)]2C5H3N}MBr2 (M = Mn, Fe, Co, Ni, Cu, Zn), 1-6, were characterized by single crystal X-ray structural studies revealing complexes with pentacoordinate distorted square pyramidal coordination environments. This assembly of complexes provided a unique array for examining the relationship between experimental structure and computed electronic structure. While experimental structural features basically correlated with the Irving-Williams series, some clear deviations were rationalized through the computational analysis. A balance of bis(imino)pyridine/metal with bonding/antibonding π interactions was used to explain the divergent directions of Fe(ii)-N and Co(ii)-N bond lengths. Similarly, orbital details were used to justify the opposing change in Cu-Brap and Cu-Brbas bond lengths. Furthermore, computational analysis provided a unique method to document a surprising low bond order for the M-N bonds of bis(imino)pyridine ligand in this series.
Angewandte Chemie International Edition, Feb 1, 2007
Journal of Organometallic Chemistry, 2016
Dalton transactions (Cambridge, England : 2003), Jan 9, 2015
Polyaminoboranes [N(R)H-BH2]n (: R = H, : R = Me) were pyrolyzed on a range of substrates: silico... more Polyaminoboranes [N(R)H-BH2]n (: R = H, : R = Me) were pyrolyzed on a range of substrates: silicon, metal foils (stainless steel, nickel, and rhodium), and sapphire wafers, as well as on Al2O3 and AlN powders. The pyrolysis of on a Si-wafer resulted in porous nanostructures containing hexagonal-boron nitride (h-BN). In the case of or H3N·BH3 as precursor, using rhodium foil as substrate afforded amorphous B and N-containing nanostructures, and polydisperse spherical nanoparticles, respectively. Switching the substrate to sapphire wafers, as well as to Al2O3 or AlN powders, resulted in formation of crystalline Al5BO9 nanostructures (nanowires, nanotubes, and nanoribbons). For sapphire wafers, the size of the resulting nanowires was influenced by modifying the surface defect density.
Inorganic chemistry, Jan 4, 2015
Although the dehydrogenation chemistry of amine-boranes substituted at nitrogen has attracted con... more Although the dehydrogenation chemistry of amine-boranes substituted at nitrogen has attracted considerable attention, much less is known about the reactivity of their B-substituted analogues. When the B-methylated amine-borane adducts, RR'NH·BH2Me (1a: R = R' = H; 1b: R = Me, R' = H; 1c: R = R' = Me; 1d: R = R' = iPr), were heated to 70 °C in solution (THF or toluene), redistribution reactions were observed involving the apparent scrambling of the methyl and hydrogen substituents on boron to afford a mixture of the species RR'NH·BH3-xMex (x = 0-3). These reactions were postulated to arise via amine-borane dissociation followed by the reversible formation of diborane intermediates and adduct reformation. Dehydrocoupling of 1a-1d with Rh(I), Ir(III), and Ni(0) precatalysts in THF at 20 °C resulted in an array of products, including aminoborane RR'N═BHMe, cyclic diborazane [RR'N-BHMe]2, and borazine [RN-BMe]3 based on analysis by in situ (11)B NMR spectr...
Angewandte Chemie (International ed. in English), Jan 22, 2015
A simple and convergent synthetic strategy used to increase the diversity of the carbodicarbene l... more A simple and convergent synthetic strategy used to increase the diversity of the carbodicarbene ligand framework through incorporation of unsymmetrical pendant groups is reported. Structural analysis and spectroscopic studies of ligands and their Rh complexes are reported. Reactivity studies reveal carbodicarbenes as competent organocatalysts for amine methylation using CO2 as a synthon. A unique BH-activated boron-carbodicarbene complex was isolated as a reaction intermediate, providing mechanistic insight into the CO2 functionalization process.
Angewandte Chemie (International ed. in English), Jan 2, 2015
Mild thermolysis of Lewis base stabilized phosphinoborane monomers R(1) R(2) PBH2 ⋅NMe3 (R(1) ,R... more Mild thermolysis of Lewis base stabilized phosphinoborane monomers R(1) R(2) PBH2 ⋅NMe3 (R(1) ,R(2) =H, Ph, or tBu/H) at room temperature to 100 °C provides a convenient new route to oligo- and polyphosphinoboranes [R(1) R(2) P-BH2 ]n . The polymerization appears to proceed via the addition/head-to-tail polymerization of short-lived free phosphinoborane monomers, R(1) R(2) P-BH2 . This method offers access to high molar mass materials, as exemplified by poly(tert-butylphosphinoborane), that are currently inaccessible using other routes (e.g. catalytic dehydrocoupling).
Angewandte Chemie, 2015
The catalyst loading is the key to control the molecular weight of the polymer in the iron-cataly... more The catalyst loading is the key to control the molecular weight of the polymer in the iron-catalyzed dehydropolymerization of phosphine-borane adducts. Studies showed that the reaction proceeds through a chain-growth coordination-insertion mechanism.
ChemInform, 2008
Lewis Acid Catalyzed Hydrogenation: B(C6F5)3-Mediated Reduction of Imines and Nitriles with H 2 .... more Lewis Acid Catalyzed Hydrogenation: B(C6F5)3-Mediated Reduction of Imines and Nitriles with H 2 . -The Lewis acid is an efficient catalyst for the direct hydrogenation of imines (I) and the reductive ring-opening of aziridines, such as (III), with H2 under mild conditions. Addition of a bulky phosphine allows the reduction of protected nitriles V). -(CHASE, P. A.; JURCA, T.; STEPHAN*, D. W.; Chem. Commun. (Cambridge) 2008, 14, 1701-1703; Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.; Eng.) -M. Paetzel 33-044
ChemInform, 2008
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Polyhedron, 2012
... Cory M. Widdifield,; Titel Jurca,; Darrin S. Richeson Corresponding author contact informatio... more ... Cory M. Widdifield,; Titel Jurca,; Darrin S. Richeson Corresponding author contact information , E-mail the corresponding author ,; David L. Bryce ... experiments using the 69/71 Ga probe nuclei in multiple magnetic fields clearly establish, via its diagnostic Knight-shifted resonance ...
Organometallics, 2012
This paper describes the synthesis and characterization of trimethylaluminum (2a), dimethylalumin... more This paper describes the synthesis and characterization of trimethylaluminum (2a), dimethylaluminum (3a), and triphenylboron complexes (7) supported by functional aminelinked NHC ligands. The chemical reactivity studies with carbodiimide and isocyanate were preformed with 2a and 3a, illustrating the noninnocent nature in Al−carbene bonding. However, the boron−carbene interaction is quite robust against addition of these substrates even at higher temperature conditions. The subtle difference in chemical reactivity between aluminum and boron is attributed from the metal−carbene bond covalency. Development of the catalytic method for Suzuki−Miyaura coupling utilizing triphenylboron reagent supported by amino-NHC is also presented.
Nature Chemistry, 2013
Catalytic reactions that enable the formation of new bonds to carbon centres play a pervasive rol... more Catalytic reactions that enable the formation of new bonds to carbon centres play a pervasive role in the state-of-the-art synthesis of organic molecules and macromolecules. In contrast, the development of analogous processes as routes to main group compounds and materials has been much slower. Nevertheless, recent advances have led to a broad expansion of this field and now allow access to a wide range of catenated structures based on elements across the p block. These breakthroughs have already impacted areas such as hydrogen storage and transfer, functional inorganic polymers and ceramic thin films. Dehydrogenation and dehydrocoupling processes are particularly well developed and may be mediated by either transition metal or main group catalysts. Such pathways represent an increasingly attractive and convenient alternative to traditional routes, such as salt metathesis and reductive coupling reactions. An overview of this emerging area is presented in this Review with a focus on recent developments and future challenges.
Journal of the American Chemical Society, 2011
Bis(imino)pyridine pincer ligands in conjunction with two isothiocyanate ligands have been used t... more Bis(imino)pyridine pincer ligands in conjunction with two isothiocyanate ligands have been used to prepare two mononuclear Co(II) complexes. Both complexes have a distorted square-pyramidal geometry with the Co(II) centers lying above the basal plane. This leads to significant spin-orbit coupling for the d(7) Co(II) ions and consequently to slow relaxation of the magnetization that is characteristic of Single-Molecule Magnet (SMM) behavior.
Journal of the American Chemical Society, 2013
Linear diborazanes R3N-BH2-NR2-BH3 (R = alkyl or H) are often implicated as key intermediates in ... more Linear diborazanes R3N-BH2-NR2-BH3 (R = alkyl or H) are often implicated as key intermediates in the dehydrocoupling/dehydrogenation of amine-boranes to form oligo- and polyaminoboranes. Here we report detailed studies of the reactivity of three related examples: Me3N-BH2-NMe2-BH3 (1), Me3N-BH2-NHMe-BH3 (2), and MeNH2-BH2-NHMe-BH3 (3). The mechanisms of the thermal and catalytic redistributions of 1 were investigated in depth using temporal-concentration studies, deuterium labeling, and DFT calculations. The results indicated that, although the products formed under both thermal and catalytic regimes are identical (Me3N·BH3 (8) and [Me2N-BH2]2 (9a)), the mechanisms of their formation differ significantly. The thermal pathway was found to involve the dissociation of the terminal amine to form [H2B(μ-H)(μ-NMe2)BH2] (5) and NMe3 as intermediates, with the former operating as a catalyst and accelerating the redistribution of 1. Intermediate 5 was then transformed to amine-borane 8 and the cyclic diborazane 9a by two different mechanisms. In contrast, under catalytic conditions (0.3-2 mol % IrH2POCOP (POCOP = κ(3)-1,3-(OPtBu2)2C6H3)), 8 was found to inhibit the redistribution of 1 by coordination to the Ir-center. Furthermore, the catalytic pathway involved direct formation of 8 and Me2N═BH2 (9b), which spontaneously dimerizes to give 9a, with the absence of 5 and BH3 as intermediates. The mechanisms elucidated for 1 are also likely to be applicable to other diborazanes, for example, 2 and 3, for which detailed mechanistic studies are impaired by complex post-redistribution chemistry. This includes both metal-free and metal-mediated oligomerization of MeNH═BH2 (10) to form oligoaminoborane [MeNH-BH2]x (11) or polyaminoborane [MeNH-BH2]n (16) following the initial redistribution reaction.
The Journal of Physical Chemistry Letters, 2010
A comprehensive multinuclear solid-state magnetic resonance study of In(I)-and Ag(I)bis(imino)pyr... more A comprehensive multinuclear solid-state magnetic resonance study of In(I)-and Ag(I)bis(imino)pyridine systems is presented. Solid-state 115 In and 109 Ag NMR experiments are utilized to probe the metal cation centers, which are very weakly coordinated to the bis(imino)pyridine ligands. Along with solid-state 15 N NMR data, it is shown that the metal cations interact with the N atoms within the "pocket" of the ligands. Reasonable agreement between the measured and calculated 115 In NMR (electric field gradient and chemical shift) tensors is obtained. The relationship between the electric field gradient tensor and the arrangement of the metal center relative to the encumbered ligand is explored. The insights obtained aid in understanding the structure and bonding in these kinetically stable complexes of unstable metal ions and may assist in the rational design of other encumbered ligands for capturing reactive species.
European Journal of Inorganic Chemistry, 2016
Dalton Trans., 2016
The preparation and characterization of a series of divalent 3d transition metal complexes suppor... more The preparation and characterization of a series of divalent 3d transition metal complexes supported by a tridentate planar bis(iminopyridine) ligand are reported. The complexes {2,6-[PhC[double bond, length as m-dash]N(tBu2C6H3)]2C5H3N}MBr2 (M = Mn, Fe, Co, Ni, Cu, Zn), 1-6, were characterized by single crystal X-ray structural studies revealing complexes with pentacoordinate distorted square pyramidal coordination environments. This assembly of complexes provided a unique array for examining the relationship between experimental structure and computed electronic structure. While experimental structural features basically correlated with the Irving-Williams series, some clear deviations were rationalized through the computational analysis. A balance of bis(imino)pyridine/metal with bonding/antibonding π interactions was used to explain the divergent directions of Fe(ii)-N and Co(ii)-N bond lengths. Similarly, orbital details were used to justify the opposing change in Cu-Brap and Cu-Brbas bond lengths. Furthermore, computational analysis provided a unique method to document a surprising low bond order for the M-N bonds of bis(imino)pyridine ligand in this series.
Angewandte Chemie International Edition, Feb 1, 2007
Journal of Organometallic Chemistry, 2016
Dalton transactions (Cambridge, England : 2003), Jan 9, 2015
Polyaminoboranes [N(R)H-BH2]n (: R = H, : R = Me) were pyrolyzed on a range of substrates: silico... more Polyaminoboranes [N(R)H-BH2]n (: R = H, : R = Me) were pyrolyzed on a range of substrates: silicon, metal foils (stainless steel, nickel, and rhodium), and sapphire wafers, as well as on Al2O3 and AlN powders. The pyrolysis of on a Si-wafer resulted in porous nanostructures containing hexagonal-boron nitride (h-BN). In the case of or H3N·BH3 as precursor, using rhodium foil as substrate afforded amorphous B and N-containing nanostructures, and polydisperse spherical nanoparticles, respectively. Switching the substrate to sapphire wafers, as well as to Al2O3 or AlN powders, resulted in formation of crystalline Al5BO9 nanostructures (nanowires, nanotubes, and nanoribbons). For sapphire wafers, the size of the resulting nanowires was influenced by modifying the surface defect density.
Inorganic chemistry, Jan 4, 2015
Although the dehydrogenation chemistry of amine-boranes substituted at nitrogen has attracted con... more Although the dehydrogenation chemistry of amine-boranes substituted at nitrogen has attracted considerable attention, much less is known about the reactivity of their B-substituted analogues. When the B-methylated amine-borane adducts, RR'NH·BH2Me (1a: R = R' = H; 1b: R = Me, R' = H; 1c: R = R' = Me; 1d: R = R' = iPr), were heated to 70 °C in solution (THF or toluene), redistribution reactions were observed involving the apparent scrambling of the methyl and hydrogen substituents on boron to afford a mixture of the species RR'NH·BH3-xMex (x = 0-3). These reactions were postulated to arise via amine-borane dissociation followed by the reversible formation of diborane intermediates and adduct reformation. Dehydrocoupling of 1a-1d with Rh(I), Ir(III), and Ni(0) precatalysts in THF at 20 °C resulted in an array of products, including aminoborane RR'N═BHMe, cyclic diborazane [RR'N-BHMe]2, and borazine [RN-BMe]3 based on analysis by in situ (11)B NMR spectr...
Angewandte Chemie (International ed. in English), Jan 22, 2015
A simple and convergent synthetic strategy used to increase the diversity of the carbodicarbene l... more A simple and convergent synthetic strategy used to increase the diversity of the carbodicarbene ligand framework through incorporation of unsymmetrical pendant groups is reported. Structural analysis and spectroscopic studies of ligands and their Rh complexes are reported. Reactivity studies reveal carbodicarbenes as competent organocatalysts for amine methylation using CO2 as a synthon. A unique BH-activated boron-carbodicarbene complex was isolated as a reaction intermediate, providing mechanistic insight into the CO2 functionalization process.
Angewandte Chemie (International ed. in English), Jan 2, 2015
Mild thermolysis of Lewis base stabilized phosphinoborane monomers R(1) R(2) PBH2 ⋅NMe3 (R(1) ,R... more Mild thermolysis of Lewis base stabilized phosphinoborane monomers R(1) R(2) PBH2 ⋅NMe3 (R(1) ,R(2) =H, Ph, or tBu/H) at room temperature to 100 °C provides a convenient new route to oligo- and polyphosphinoboranes [R(1) R(2) P-BH2 ]n . The polymerization appears to proceed via the addition/head-to-tail polymerization of short-lived free phosphinoborane monomers, R(1) R(2) P-BH2 . This method offers access to high molar mass materials, as exemplified by poly(tert-butylphosphinoborane), that are currently inaccessible using other routes (e.g. catalytic dehydrocoupling).
Angewandte Chemie, 2015
The catalyst loading is the key to control the molecular weight of the polymer in the iron-cataly... more The catalyst loading is the key to control the molecular weight of the polymer in the iron-catalyzed dehydropolymerization of phosphine-borane adducts. Studies showed that the reaction proceeds through a chain-growth coordination-insertion mechanism.
ChemInform, 2008
Lewis Acid Catalyzed Hydrogenation: B(C6F5)3-Mediated Reduction of Imines and Nitriles with H 2 .... more Lewis Acid Catalyzed Hydrogenation: B(C6F5)3-Mediated Reduction of Imines and Nitriles with H 2 . -The Lewis acid is an efficient catalyst for the direct hydrogenation of imines (I) and the reductive ring-opening of aziridines, such as (III), with H2 under mild conditions. Addition of a bulky phosphine allows the reduction of protected nitriles V). -(CHASE, P. A.; JURCA, T.; STEPHAN*, D. W.; Chem. Commun. (Cambridge) 2008, 14, 1701-1703; Dep. Chem., Univ. Toronto, Toronto, Ont. M5S 3H6, Can.; Eng.) -M. Paetzel 33-044
ChemInform, 2008
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Polyhedron, 2012
... Cory M. Widdifield,; Titel Jurca,; Darrin S. Richeson Corresponding author contact informatio... more ... Cory M. Widdifield,; Titel Jurca,; Darrin S. Richeson Corresponding author contact information , E-mail the corresponding author ,; David L. Bryce ... experiments using the 69/71 Ga probe nuclei in multiple magnetic fields clearly establish, via its diagnostic Knight-shifted resonance ...
Organometallics, 2012
This paper describes the synthesis and characterization of trimethylaluminum (2a), dimethylalumin... more This paper describes the synthesis and characterization of trimethylaluminum (2a), dimethylaluminum (3a), and triphenylboron complexes (7) supported by functional aminelinked NHC ligands. The chemical reactivity studies with carbodiimide and isocyanate were preformed with 2a and 3a, illustrating the noninnocent nature in Al−carbene bonding. However, the boron−carbene interaction is quite robust against addition of these substrates even at higher temperature conditions. The subtle difference in chemical reactivity between aluminum and boron is attributed from the metal−carbene bond covalency. Development of the catalytic method for Suzuki−Miyaura coupling utilizing triphenylboron reagent supported by amino-NHC is also presented.
Nature Chemistry, 2013
Catalytic reactions that enable the formation of new bonds to carbon centres play a pervasive rol... more Catalytic reactions that enable the formation of new bonds to carbon centres play a pervasive role in the state-of-the-art synthesis of organic molecules and macromolecules. In contrast, the development of analogous processes as routes to main group compounds and materials has been much slower. Nevertheless, recent advances have led to a broad expansion of this field and now allow access to a wide range of catenated structures based on elements across the p block. These breakthroughs have already impacted areas such as hydrogen storage and transfer, functional inorganic polymers and ceramic thin films. Dehydrogenation and dehydrocoupling processes are particularly well developed and may be mediated by either transition metal or main group catalysts. Such pathways represent an increasingly attractive and convenient alternative to traditional routes, such as salt metathesis and reductive coupling reactions. An overview of this emerging area is presented in this Review with a focus on recent developments and future challenges.
Journal of the American Chemical Society, 2011
Bis(imino)pyridine pincer ligands in conjunction with two isothiocyanate ligands have been used t... more Bis(imino)pyridine pincer ligands in conjunction with two isothiocyanate ligands have been used to prepare two mononuclear Co(II) complexes. Both complexes have a distorted square-pyramidal geometry with the Co(II) centers lying above the basal plane. This leads to significant spin-orbit coupling for the d(7) Co(II) ions and consequently to slow relaxation of the magnetization that is characteristic of Single-Molecule Magnet (SMM) behavior.
Journal of the American Chemical Society, 2013
Linear diborazanes R3N-BH2-NR2-BH3 (R = alkyl or H) are often implicated as key intermediates in ... more Linear diborazanes R3N-BH2-NR2-BH3 (R = alkyl or H) are often implicated as key intermediates in the dehydrocoupling/dehydrogenation of amine-boranes to form oligo- and polyaminoboranes. Here we report detailed studies of the reactivity of three related examples: Me3N-BH2-NMe2-BH3 (1), Me3N-BH2-NHMe-BH3 (2), and MeNH2-BH2-NHMe-BH3 (3). The mechanisms of the thermal and catalytic redistributions of 1 were investigated in depth using temporal-concentration studies, deuterium labeling, and DFT calculations. The results indicated that, although the products formed under both thermal and catalytic regimes are identical (Me3N·BH3 (8) and [Me2N-BH2]2 (9a)), the mechanisms of their formation differ significantly. The thermal pathway was found to involve the dissociation of the terminal amine to form [H2B(μ-H)(μ-NMe2)BH2] (5) and NMe3 as intermediates, with the former operating as a catalyst and accelerating the redistribution of 1. Intermediate 5 was then transformed to amine-borane 8 and the cyclic diborazane 9a by two different mechanisms. In contrast, under catalytic conditions (0.3-2 mol % IrH2POCOP (POCOP = κ(3)-1,3-(OPtBu2)2C6H3)), 8 was found to inhibit the redistribution of 1 by coordination to the Ir-center. Furthermore, the catalytic pathway involved direct formation of 8 and Me2N═BH2 (9b), which spontaneously dimerizes to give 9a, with the absence of 5 and BH3 as intermediates. The mechanisms elucidated for 1 are also likely to be applicable to other diborazanes, for example, 2 and 3, for which detailed mechanistic studies are impaired by complex post-redistribution chemistry. This includes both metal-free and metal-mediated oligomerization of MeNH═BH2 (10) to form oligoaminoborane [MeNH-BH2]x (11) or polyaminoborane [MeNH-BH2]n (16) following the initial redistribution reaction.
The Journal of Physical Chemistry Letters, 2010
A comprehensive multinuclear solid-state magnetic resonance study of In(I)-and Ag(I)bis(imino)pyr... more A comprehensive multinuclear solid-state magnetic resonance study of In(I)-and Ag(I)bis(imino)pyridine systems is presented. Solid-state 115 In and 109 Ag NMR experiments are utilized to probe the metal cation centers, which are very weakly coordinated to the bis(imino)pyridine ligands. Along with solid-state 15 N NMR data, it is shown that the metal cations interact with the N atoms within the "pocket" of the ligands. Reasonable agreement between the measured and calculated 115 In NMR (electric field gradient and chemical shift) tensors is obtained. The relationship between the electric field gradient tensor and the arrangement of the metal center relative to the encumbered ligand is explored. The insights obtained aid in understanding the structure and bonding in these kinetically stable complexes of unstable metal ions and may assist in the rational design of other encumbered ligands for capturing reactive species.