Not solely a spectator: Exploring the chemistry of the CO bond in alkoxide and related ligands

Rhenium(V) Dioxo Complexes with Dihydrobis(pyrazolyl)borates: Synthesis and Reactivity toward Electrophilic Substrates

“…The O(1)−Re−O(2) bond angle (178.8(2)°) indicates that the oxygen from the siloxide is almost trans to the oxo group. The Re−O(1) bond distance (1.688(4) Å) is comparable to the values found in other rhenium(V) complexes with poly(pyrazolyl)borates and is in the usual range for rhenium(V) monooxo complexes. − , The coordination of the siloxide ligand is characterized by a Re−O(2) distance of 1.886(3) Å, which is comparable to and shorter than the values described for [ReOCl 2 (OSiMe 3 )(py) 2 ] (1.889(4) Å) and [(η 5 -C 5 Me 5 )ReCl(OSiMe 3 )(NCH 2 -2-C 5 H 4 N)] (2.020(6) Å), respectively. , These data are consistent with some competition of the siloxide for π bonding with the metal, the Re−OSiMe 3 having bond some multiple character. Each dihydrobis(pyrazolyl)borate defines a six-membered ReN 4 B chelating ring in a typical boat conformation, with the apexes of each boat conformation pointing alternatively toward the oxo and siloxide ligands.…”

“…Each dihydrobis(pyrazolyl)borate defines a six-membered ReN 4 B chelating ring in a typical boat conformation, with the apexes of each boat conformation pointing alternatively toward the oxo and siloxide ligands. The average Re−N bond length of 2.113(5) Å is comparable to the values found in other rhenium monooxo complexes with poly(pyrazolyl)borate ligands. − The siloxide ligand bends (Re−O(2)−Si angle of 160.7(2)°) toward the bidentate ligand which has the boat conformation directed toward the oxo group, certainly to minimize repulsive interactions.

2 ORTEP view of [ReO(OSiMe 3 ){H 2 B(pz) 2 } 2 ] ( 3 ).

…”

Rhenium(V) Dioxo Complexes with Dihydrobis(pyrazolyl)borates: Synthesis and Reactivity toward Electrophilic Substrates

“…The O(1)−Re−O(2) bond angle (178.8(2)°) indicates that the oxygen from the siloxide is almost trans to the oxo group. The Re−O(1) bond distance (1.688(4) Å) is comparable to the values found in other rhenium(V) complexes with poly(pyrazolyl)borates and is in the usual range for rhenium(V) monooxo complexes. − , The coordination of the siloxide ligand is characterized by a Re−O(2) distance of 1.886(3) Å, which is comparable to and shorter than the values described for [ReOCl 2 (OSiMe 3 )(py) 2 ] (1.889(4) Å) and [(η 5 -C 5 Me 5 )ReCl(OSiMe 3 )(NCH 2 -2-C 5 H 4 N)] (2.020(6) Å), respectively. , These data are consistent with some competition of the siloxide for π bonding with the metal, the Re−OSiMe 3 having bond some multiple character. Each dihydrobis(pyrazolyl)borate defines a six-membered ReN 4 B chelating ring in a typical boat conformation, with the apexes of each boat conformation pointing alternatively toward the oxo and siloxide ligands.…”

“…Each dihydrobis(pyrazolyl)borate defines a six-membered ReN 4 B chelating ring in a typical boat conformation, with the apexes of each boat conformation pointing alternatively toward the oxo and siloxide ligands. The average Re−N bond length of 2.113(5) Å is comparable to the values found in other rhenium monooxo complexes with poly(pyrazolyl)borate ligands. − The siloxide ligand bends (Re−O(2)−Si angle of 160.7(2)°) toward the bidentate ligand which has the boat conformation directed toward the oxo group, certainly to minimize repulsive interactions.

2 ORTEP view of [ReO(OSiMe 3 ){H 2 B(pz) 2 } 2 ] ( 3 ).

…”

Assembly of Molybdenum/Titanium μ-Oxo Complexes via Radical Alkoxide C−O Cleavage

“…A C−S bond cleavage process that may be related was reported recently . Alkoxide C−O bond cleavage processes have been summarized …”

Mechanistic Insights into the ReIO2(PPh3)2-Promoted Reductive Coupling of Alcohols

“…We conclude, therefore, that the migratory deinsertion also has a substantial activation barrier probably greater than for homolytic O-R dissociation. Indeed, to our knowledge, proven examples of a metal–alkoxide to oxo-metal alkyl transformation have not been reported . This conversion has been suggested to account for the formation of small amounts of coupling product in molybdate-catalyzed dehydration of benzylic alcohols …”

Rhenium(V) Dioxo Complexes with Dihydrobis(pyrazolyl)borates: Synthesis and Reactivity toward Electrophilic Substrates

“…The O(1)−Re−O(2) bond angle (178.8(2)°) indicates that the oxygen from the siloxide is almost trans to the oxo group. The Re−O(1) bond distance (1.688(4) Å) is comparable to the values found in other rhenium(V) complexes with poly(pyrazolyl)borates and is in the usual range for rhenium(V) monooxo complexes. − , The coordination of the siloxide ligand is characterized by a Re−O(2) distance of 1.886(3) Å, which is comparable to and shorter than the values described for [ReOCl 2 (OSiMe 3 )(py) 2 ] (1.889(4) Å) and [(η 5 -C 5 Me 5 )ReCl(OSiMe 3 )(NCH 2 -2-C 5 H 4 N)] (2.020(6) Å), respectively. , These data are consistent with some competition of the siloxide for π bonding with the metal, the Re−OSiMe 3 having bond some multiple character. Each dihydrobis(pyrazolyl)borate defines a six-membered ReN 4 B chelating ring in a typical boat conformation, with the apexes of each boat conformation pointing alternatively toward the oxo and siloxide ligands.…”

“…Each dihydrobis(pyrazolyl)borate defines a six-membered ReN 4 B chelating ring in a typical boat conformation, with the apexes of each boat conformation pointing alternatively toward the oxo and siloxide ligands. The average Re−N bond length of 2.113(5) Å is comparable to the values found in other rhenium monooxo complexes with poly(pyrazolyl)borate ligands. − The siloxide ligand bends (Re−O(2)−Si angle of 160.7(2)°) toward the bidentate ligand which has the boat conformation directed toward the oxo group, certainly to minimize repulsive interactions.

2 ORTEP view of [ReO(OSiMe 3 ){H 2 B(pz) 2 } 2 ] ( 3 ).

…”

Assembly of Molybdenum/Titanium μ-Oxo Complexes via Radical Alkoxide C−O Cleavage

“…A C−S bond cleavage process that may be related was reported recently . Alkoxide C−O bond cleavage processes have been summarized …”

Mechanistic Insights into the ReIO2(PPh3)2-Promoted Reductive Coupling of Alcohols

“…We conclude, therefore, that the migratory deinsertion also has a substantial activation barrier probably greater than for homolytic O-R dissociation. Indeed, to our knowledge, proven examples of a metal–alkoxide to oxo-metal alkyl transformation have not been reported . This conversion has been suggested to account for the formation of small amounts of coupling product in molybdate-catalyzed dehydration of benzylic alcohols …”

Rhenium(V) Dioxo Complexes with Dihydrobis(pyrazolyl)borates: Synthesis and Reactivity toward Electrophilic Substrates

“…The O(1)−Re−O(2) bond angle (178.8(2)°) indicates that the oxygen from the siloxide is almost trans to the oxo group. The Re−O(1) bond distance (1.688(4) Å) is comparable to the values found in other rhenium(V) complexes with poly(pyrazolyl)borates and is in the usual range for rhenium(V) monooxo complexes. − , The coordination of the siloxide ligand is characterized by a Re−O(2) distance of 1.886(3) Å, which is comparable to and shorter than the values described for [ReOCl 2 (OSiMe 3 )(py) 2 ] (1.889(4) Å) and [(η 5 -C 5 Me 5 )ReCl(OSiMe 3 )(NCH 2 -2-C 5 H 4 N)] (2.020(6) Å), respectively. , These data are consistent with some competition of the siloxide for π bonding with the metal, the Re−OSiMe 3 having bond some multiple character. Each dihydrobis(pyrazolyl)borate defines a six-membered ReN 4 B chelating ring in a typical boat conformation, with the apexes of each boat conformation pointing alternatively toward the oxo and siloxide ligands.…”

“…Each dihydrobis(pyrazolyl)borate defines a six-membered ReN 4 B chelating ring in a typical boat conformation, with the apexes of each boat conformation pointing alternatively toward the oxo and siloxide ligands. The average Re−N bond length of 2.113(5) Å is comparable to the values found in other rhenium monooxo complexes with poly(pyrazolyl)borate ligands. − The siloxide ligand bends (Re−O(2)−Si angle of 160.7(2)°) toward the bidentate ligand which has the boat conformation directed toward the oxo group, certainly to minimize repulsive interactions.

2 ORTEP view of [ReO(OSiMe 3 ){H 2 B(pz) 2 } 2 ] ( 3 ).

…”

Assembly of Molybdenum/Titanium μ-Oxo Complexes via Radical Alkoxide C−O Cleavage

“…A C−S bond cleavage process that may be related was reported recently . Alkoxide C−O bond cleavage processes have been summarized …”

Mechanistic Insights into the ReIO2(PPh3)2-Promoted Reductive Coupling of Alcohols

“…We conclude, therefore, that the migratory deinsertion also has a substantial activation barrier probably greater than for homolytic O-R dissociation. Indeed, to our knowledge, proven examples of a metal–alkoxide to oxo-metal alkyl transformation have not been reported . This conversion has been suggested to account for the formation of small amounts of coupling product in molybdate-catalyzed dehydration of benzylic alcohols …”