Marcus Drover - Academia.edu (original) (raw)
Papers by Marcus Drover
Polyhedron, 2015
A novel lithium complex was prepared from the reaction of 1,4-bis(2-hydroxy-3,5-di-tert-butylbenz... more A novel lithium complex was prepared from the reaction of 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)imidazolidine H 2 [O 2 N 2 ] BuBuIm (L1H 2 ) with n-butyllithium to provide the corresponding tetralithium amine-bis(phenolate) complex {Li 2 [L1]} 2 •4THF, 1. Variable temperature 7 Li NMR revealed that this complex is labile in solution, dissociating at elevated temperatures to afford two dilithium entities. Additionally, 7 Li MAS NMR was performed on 1 to provide information regarding the lithium coordination environment in the bulk solid-state. The reactivity of 1 was assessed in the ring-expansion polymerization of ε-caprolactone (ε-CL), which was first order in ε-CL with an activation energy of 50.9 kJmol -1 . Reaction of 1 and a related Li complex (formed in situ) with BiCl 3 afforded hydrolytically unstable bismuth phenolate species, as evidenced by the isolation and structural characterization of [Bi 4 (Cl) 3 (µ -Cl)(µ-O)(O) 2 {[O 2 N 2 ] BuBuPip } 2 ], 2, where [O 2 N 2 ] BuBuPip is the homopiperazine-containing analog of L1.
Journal of Organometallic Chemistry, 2015
Oxidation of the rhodium(I) ethylene complex, [(TPA)Rh(h 2 -CH 2 CH 2 )] þ (1, TPA ¼ N,N,N-tris(2... more Oxidation of the rhodium(I) ethylene complex, [(TPA)Rh(h 2 -CH 2 CH 2 )] þ (1, TPA ¼ N,N,N-tris(2pyridylmethyl)amine) with a selection of nitrene precursors led to formation of N-substituted azarhodacyclobutanes. Appropriate choice of oxidant allowed for selective preparation of one isomer. For example, treatment of 1 with tosyl azide provided isomer 3 exclusively for the first time. Variation of the substituent on the ring-nitrogen was possible e.g., by employing nosyl iodinane precursor 8. Substituted carbamates were also screened, providing two rotamers of isomer type 3. In addition, preliminary reactivity studies revealing the increased chemical reactivity of the product complexes 14 and 15 are presented.
Organometallics, 2015
Reaction of the amidate ligand salts Na[N(Dipp)C(O)R] (R = Ph (1a), tBu (1b); Dipp = 2,6-diisopro... more Reaction of the amidate ligand salts Na[N(Dipp)C(O)R] (R = Ph (1a), tBu (1b); Dipp = 2,6-diisopropylphenyl) with [Rh(NBD)-Cl] 2 (NBD = norbornadiene) proceeds to give the dirhodium(I) complexes [Rh 2 {μ 2 -N,O-N(Dipp)C(O)R} 2 (NBD) 2 ] (R = Ph (2a), tBu (2b)) with variable coordination behavior. For complex 2b, a monomer− dimer equilibrium with the mononuclear complex [Rh{κ 2 -N,O-N(Dipp)-C(O)tBu}(NBD)] (3b) was established for the first time. Precursors 2a,b were treated with PPh 3 and PCy 3 , giving the distorted-square-planar κ 2 -N,O amidates [Rh{κ 2 -N,O-N(Dipp)C(O)R}(PPh 3 ) 2 ] (R = Ph (4a), tBu (4b)) or the κ 1 -O complexes [Rh{κ 1 -O-N(Dipp)C(O)R}(NBD)(PCy 3 )] (R = Ph , tBu (5b)). Initial reactivity screening showed that complex 4b undergoes O 2 activation, providing Ph 3 PO; via the transient peroxo complex 6b, which was characterized in the solution phase. The κ 2 -N,O amidate coordination in 6b has been conclusively established by diagnostic 13 C{ 1 H} NMR spectroscopy.
Chemistry-a European Journal, 2014
Rh-containing metallacycles, [(TPA)Rh(III)(κ(2)-(C,N)-CH2CH2(NR)2-]Cl; TPA = N,N,N,N-tris(2-pyrid... more Rh-containing metallacycles, [(TPA)Rh(III)(κ(2)-(C,N)-CH2CH2(NR)2-]Cl; TPA = N,N,N,N-tris(2-pyridylmethyl)amine have been accessed through treatment of the Rh(I) ethylene complex, [(TPA)Rh(η(2)-CH2CH2)]Cl ([1]Cl) with substituted diazenes. We show this methodology to be tolerant of electron-deficient azo compounds including azo diesters (RCO2N=NCO2R; R = Et [3]Cl, R = iPr [4]Cl, R = tBu [5]Cl, and R = Bn [6]Cl) and a cyclic azo diamide: 4-phenyl-1,2,4-triazole-3,5-dione (PTAD), [7]Cl. The latter complex features two ortho-fused ring systems and constitutes the first 3-rhoda-1,2-diazabicyclo[3.3.0]octane. Preliminary evidence suggests that these complexes result from N-N coordination followed by insertion of ethylene into a [Rh]-N bond. In terms of reactivity, [3]Cl and [4]Cl successfully undergo ring-opening using p-toluenesulfonic acid, affording the Rh chlorides, [(TPA)Rh(III)(Cl)(κ(1)-(C)-CH2CH2(NCO2R)(NHCO2R)]OTs; [13]OTs and [14]OTs. Deprotection of [5]Cl using trifluoroacetic acid was also found to give an ethyl substituted, end-on coordinated diazene [(TPA)Rh(III)(κ(2)-(C,N)-CH2CH2(NH)2-](+) [16]Cl, a hitherto unreported motif. Treatment of [16]Cl with acetyl chloride resulted in the bisacetylated adduct [(TPA)Rh(III)(κ(2)-(C,N)-CH2CH2(NAc)2-](+), [17]Cl. Treatment of [1]Cl with AcN=NAc did not give the Rh-N insertion product, but instead the N,O-chelated complex [(TPA)Rh(I)(κ(2)-(O,N)-CH3(CO)(NH)(N=C(CH3)(OCH=CH2))]Cl [23]Cl, presumably through insertion of ethylene into a [Rh]-O bond.
Polyhedron, 2014
Tetranuclear, dinuclear and chain complexes involving some polyfunctional hydrazone and thiocarbo... more Tetranuclear, dinuclear and chain complexes involving some polyfunctional hydrazone and thiocarbohydrazone-based ligands are discussed. Ni(II) and Mn(II) [2 Â 2] grids form with l 2 -S and l 2 -O bridges respectively, and are antiferromagnetically coupled (J = À167(5), À3.59(2) cm À1 respectively).
![Research paper thumbnail of Self-Assembled Ln(III) 4 (Ln = Eu, Gd, Dy, Ho, Yb) [2 × 2] Square Grids: a New Class of Lanthanide Cluster](https://attachments.academia-assets.com/40041159/thumbnails/1.jpg)
](Inorganic Chemistry, 2013
Self-assembly of the Ln(III) ions (Ln = Eu, Gd, Dy, Ho, Yb) into square [2 × 2] grid-like arrays ... more Self-assembly of the Ln(III) ions (Ln = Eu, Gd, Dy, Ho, Yb) into square [2 × 2] grid-like arrays has been readily effected using simple, symmetric ditopic ligands based on a carbohydrazone core. The metal ions are connected via single atom bridges (e.g., μ 2 -O hydrazone , μ 2 -OH, μ 2 -OMe, μ 2 -1,1-N 3 − , μ 4 -O), depending on reaction conditions. The Gd(III) 4 examples exhibit intramolecular antiferromagnetic exchange (−J < 0.11 cm −1 ), and in one Dy(III) 4 example, with a combination of μ 2 -1,1-N 3 − , and μ 4 -O bridges linking adjacent metal ions, SMM behavior is observed. One thermally driven relaxation process is observed in the temperature range 10−25 K (τ 0 = 6.5(1) × 10 −7 s, U eff = 110(1) K) in the presence of an 1800 Oe external field, employed to suppress a second quantum based relaxation process. The extended group of Ln(III) ions which submit to this controlled self-assembly, typical of the transition metal ions, indicates the general applicability of this approach to the lanthanides. This occurs despite the anticipated limitations based on larger ionic radii and coordination numbers, and is an encouraging sign for extension to larger grids with appropriately chosen polytopic ligands.
Polyhedron, 2015
A novel lithium complex was prepared from the reaction of 1,4-bis(2-hydroxy-3,5-di-tert-butylbenz... more A novel lithium complex was prepared from the reaction of 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)imidazolidine H 2 [O 2 N 2 ] BuBuIm (L1H 2 ) with n-butyllithium to provide the corresponding tetralithium amine-bis(phenolate) complex {Li 2 [L1]} 2 •4THF, 1. Variable temperature 7 Li NMR revealed that this complex is labile in solution, dissociating at elevated temperatures to afford two dilithium entities. Additionally, 7 Li MAS NMR was performed on 1 to provide information regarding the lithium coordination environment in the bulk solid-state. The reactivity of 1 was assessed in the ring-expansion polymerization of ε-caprolactone (ε-CL), which was first order in ε-CL with an activation energy of 50.9 kJmol -1 . Reaction of 1 and a related Li complex (formed in situ) with BiCl 3 afforded hydrolytically unstable bismuth phenolate species, as evidenced by the isolation and structural characterization of [Bi 4 (Cl) 3 (µ -Cl)(µ-O)(O) 2 {[O 2 N 2 ] BuBuPip } 2 ], 2, where [O 2 N 2 ] BuBuPip is the homopiperazine-containing analog of L1.
Journal of Organometallic Chemistry, 2015
Oxidation of the rhodium(I) ethylene complex, [(TPA)Rh(h 2 -CH 2 CH 2 )] þ (1, TPA ¼ N,N,N-tris(2... more Oxidation of the rhodium(I) ethylene complex, [(TPA)Rh(h 2 -CH 2 CH 2 )] þ (1, TPA ¼ N,N,N-tris(2pyridylmethyl)amine) with a selection of nitrene precursors led to formation of N-substituted azarhodacyclobutanes. Appropriate choice of oxidant allowed for selective preparation of one isomer. For example, treatment of 1 with tosyl azide provided isomer 3 exclusively for the first time. Variation of the substituent on the ring-nitrogen was possible e.g., by employing nosyl iodinane precursor 8. Substituted carbamates were also screened, providing two rotamers of isomer type 3. In addition, preliminary reactivity studies revealing the increased chemical reactivity of the product complexes 14 and 15 are presented.
Organometallics, 2015
Reaction of the amidate ligand salts Na[N(Dipp)C(O)R] (R = Ph (1a), tBu (1b); Dipp = 2,6-diisopro... more Reaction of the amidate ligand salts Na[N(Dipp)C(O)R] (R = Ph (1a), tBu (1b); Dipp = 2,6-diisopropylphenyl) with [Rh(NBD)-Cl] 2 (NBD = norbornadiene) proceeds to give the dirhodium(I) complexes [Rh 2 {μ 2 -N,O-N(Dipp)C(O)R} 2 (NBD) 2 ] (R = Ph (2a), tBu (2b)) with variable coordination behavior. For complex 2b, a monomer− dimer equilibrium with the mononuclear complex [Rh{κ 2 -N,O-N(Dipp)-C(O)tBu}(NBD)] (3b) was established for the first time. Precursors 2a,b were treated with PPh 3 and PCy 3 , giving the distorted-square-planar κ 2 -N,O amidates [Rh{κ 2 -N,O-N(Dipp)C(O)R}(PPh 3 ) 2 ] (R = Ph (4a), tBu (4b)) or the κ 1 -O complexes [Rh{κ 1 -O-N(Dipp)C(O)R}(NBD)(PCy 3 )] (R = Ph , tBu (5b)). Initial reactivity screening showed that complex 4b undergoes O 2 activation, providing Ph 3 PO; via the transient peroxo complex 6b, which was characterized in the solution phase. The κ 2 -N,O amidate coordination in 6b has been conclusively established by diagnostic 13 C{ 1 H} NMR spectroscopy.
Chemistry-a European Journal, 2014
Rh-containing metallacycles, [(TPA)Rh(III)(κ(2)-(C,N)-CH2CH2(NR)2-]Cl; TPA = N,N,N,N-tris(2-pyrid... more Rh-containing metallacycles, [(TPA)Rh(III)(κ(2)-(C,N)-CH2CH2(NR)2-]Cl; TPA = N,N,N,N-tris(2-pyridylmethyl)amine have been accessed through treatment of the Rh(I) ethylene complex, [(TPA)Rh(η(2)-CH2CH2)]Cl ([1]Cl) with substituted diazenes. We show this methodology to be tolerant of electron-deficient azo compounds including azo diesters (RCO2N=NCO2R; R = Et [3]Cl, R = iPr [4]Cl, R = tBu [5]Cl, and R = Bn [6]Cl) and a cyclic azo diamide: 4-phenyl-1,2,4-triazole-3,5-dione (PTAD), [7]Cl. The latter complex features two ortho-fused ring systems and constitutes the first 3-rhoda-1,2-diazabicyclo[3.3.0]octane. Preliminary evidence suggests that these complexes result from N-N coordination followed by insertion of ethylene into a [Rh]-N bond. In terms of reactivity, [3]Cl and [4]Cl successfully undergo ring-opening using p-toluenesulfonic acid, affording the Rh chlorides, [(TPA)Rh(III)(Cl)(κ(1)-(C)-CH2CH2(NCO2R)(NHCO2R)]OTs; [13]OTs and [14]OTs. Deprotection of [5]Cl using trifluoroacetic acid was also found to give an ethyl substituted, end-on coordinated diazene [(TPA)Rh(III)(κ(2)-(C,N)-CH2CH2(NH)2-](+) [16]Cl, a hitherto unreported motif. Treatment of [16]Cl with acetyl chloride resulted in the bisacetylated adduct [(TPA)Rh(III)(κ(2)-(C,N)-CH2CH2(NAc)2-](+), [17]Cl. Treatment of [1]Cl with AcN=NAc did not give the Rh-N insertion product, but instead the N,O-chelated complex [(TPA)Rh(I)(κ(2)-(O,N)-CH3(CO)(NH)(N=C(CH3)(OCH=CH2))]Cl [23]Cl, presumably through insertion of ethylene into a [Rh]-O bond.
Polyhedron, 2014
Tetranuclear, dinuclear and chain complexes involving some polyfunctional hydrazone and thiocarbo... more Tetranuclear, dinuclear and chain complexes involving some polyfunctional hydrazone and thiocarbohydrazone-based ligands are discussed. Ni(II) and Mn(II) [2 Â 2] grids form with l 2 -S and l 2 -O bridges respectively, and are antiferromagnetically coupled (J = À167(5), À3.59(2) cm À1 respectively).
Inorganic Chemistry, 2013
Self-assembly of the Ln(III) ions (Ln = Eu, Gd, Dy, Ho, Yb) into square [2 × 2] grid-like arrays ... more Self-assembly of the Ln(III) ions (Ln = Eu, Gd, Dy, Ho, Yb) into square [2 × 2] grid-like arrays has been readily effected using simple, symmetric ditopic ligands based on a carbohydrazone core. The metal ions are connected via single atom bridges (e.g., μ 2 -O hydrazone , μ 2 -OH, μ 2 -OMe, μ 2 -1,1-N 3 − , μ 4 -O), depending on reaction conditions. The Gd(III) 4 examples exhibit intramolecular antiferromagnetic exchange (−J < 0.11 cm −1 ), and in one Dy(III) 4 example, with a combination of μ 2 -1,1-N 3 − , and μ 4 -O bridges linking adjacent metal ions, SMM behavior is observed. One thermally driven relaxation process is observed in the temperature range 10−25 K (τ 0 = 6.5(1) × 10 −7 s, U eff = 110(1) K) in the presence of an 1800 Oe external field, employed to suppress a second quantum based relaxation process. The extended group of Ln(III) ions which submit to this controlled self-assembly, typical of the transition metal ions, indicates the general applicability of this approach to the lanthanides. This occurs despite the anticipated limitations based on larger ionic radii and coordination numbers, and is an encouraging sign for extension to larger grids with appropriately chosen polytopic ligands.