Manganese Oxidation Catalysts with 2-(2′-Hydroxyphenyl)oxazoline Ligands: Catalyst Intermediates and Degradation Products − Crystal Structure of Bis[{2-(2′-oxazolinyl)phenolato}bis(1-methylimidazole)manganese(III)] Perchlorate

Abstract

Manganese complexes with phox ligands [Hphox = 2-(2Ј-hydroxyphenyl)oxazoline] act as oxidation catalysts with dihydrogen peroxide. Their catalytic efficiency is strongly affected by the presence of a base, such as 1-methylimidazole (1-Meim). The crystal structure of an Mn−phox complex with two axial 1-Meim ligands, [Mn(phox) 2 (1-Meim) 2 ](ClO 4 ), is reported. The [Mn(phox) 2 ] + and [Mn(phox) 2 (1-Meim)] + species have been detected in catalytic reaction mixtures by electrospray mass spectrometry. In the catalytic oxidation of styrene, turnover numbers of 428 and 456 have been ob-

Stereochemical Influence of the Ligand on the Structure of Manganese Complexes: Implications for Catalytic Epoxidations

“…52 A higher reactivity for 1-octene by the present compounds, compared to that of [Mn(phox) 3 ], is expected because the presence of electron-withdrawing substituents is known to result in a higher number of epoxide turnovers for this substrate. 9 However, for other alkenes, the complexes show lower turnover numbers, compared to that of the previously studied [Mn(R-phox) 3 ] catalysts, 22,23 which could be the result of the increased steric bulk on the axial sites.…”

“…Of the substrates tested, cyclohexene results in the highest conversion. In general, the complexes show comparable conversion for cyclooctene and 1-octene, the exception being RS-1, for which the turnovers in cyclooctene (30) are considerably higher than for 1-octene (22). Important to note here is the epoxidation of 1-octene, for which 10 to 23 turnovers in the epoxide product were obtained by the above complexes.…”

“…The unsubstituted Mn−salen complex showed no catalytic conversion of olefins, while the complex containing the tethered imidazole showed almost complete conversions of olefins using dihydrogen peroxide as the oxidant. In the [Mn(phox) 3 ]-catalyzed epoxidations, [Mn(phox) 2 ( N -Meim)] + has been found to be the major species present during catalysis. , Thus, coordination of the nitrogen-containing base has been assumed to be important for oxo transfer.…”

“…The Mn-N and Mn-O (axial carboxylate) distances are similar to those observed in other Mn(III) complexes. [21][22][23]35,36 The hydrogen bonds donated by the diethylammonium protons to the carboxylate groups of the manganese complexes link the molecules into infinite one-dimensional chains running parallel to the a axis. Details of the hydrogen bonding interactions are given in the Supporting Information (Table S1).…”

Stereochemical Influence of the Ligand on the Structure of Manganese Complexes: Implications for Catalytic Epoxidations

“…52 A higher reactivity for 1-octene by the present compounds, compared to that of [Mn(phox) 3 ], is expected because the presence of electron-withdrawing substituents is known to result in a higher number of epoxide turnovers for this substrate. 9 However, for other alkenes, the complexes show lower turnover numbers, compared to that of the previously studied [Mn(R-phox) 3 ] catalysts, 22,23 which could be the result of the increased steric bulk on the axial sites.…”

“…Of the substrates tested, cyclohexene results in the highest conversion. In general, the complexes show comparable conversion for cyclooctene and 1-octene, the exception being RS-1, for which the turnovers in cyclooctene (30) are considerably higher than for 1-octene (22). Important to note here is the epoxidation of 1-octene, for which 10 to 23 turnovers in the epoxide product were obtained by the above complexes.…”

“…The unsubstituted Mn−salen complex showed no catalytic conversion of olefins, while the complex containing the tethered imidazole showed almost complete conversions of olefins using dihydrogen peroxide as the oxidant. In the [Mn(phox) 3 ]-catalyzed epoxidations, [Mn(phox) 2 ( N -Meim)] + has been found to be the major species present during catalysis. , Thus, coordination of the nitrogen-containing base has been assumed to be important for oxo transfer.…”

“…The Mn-N and Mn-O (axial carboxylate) distances are similar to those observed in other Mn(III) complexes. [21][22][23]35,36 The hydrogen bonds donated by the diethylammonium protons to the carboxylate groups of the manganese complexes link the molecules into infinite one-dimensional chains running parallel to the a axis. Details of the hydrogen bonding interactions are given in the Supporting Information (Table S1).…”

One-Pot Synthesis of Chiral Organometallic Complexes

“…Chiral oxazolinyl organometallic complexes are very important catalysts in organic chemistry [14][15][16][17][18][19][20][21][22]. Several organometallic complexes containing 2-(2′-hydroxyphenyl) oxazolines are reported in the literature [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. The general approach to the synthesis of metal complexes begins with ligand synthesis, followed by ligand reaction with metal salts to afford organometallic complexes [43].…”

Stereochemical Influence of the Ligand on the Structure of Manganese Complexes: Implications for Catalytic Epoxidations

“…52 A higher reactivity for 1-octene by the present compounds, compared to that of [Mn(phox) 3 ], is expected because the presence of electron-withdrawing substituents is known to result in a higher number of epoxide turnovers for this substrate. 9 However, for other alkenes, the complexes show lower turnover numbers, compared to that of the previously studied [Mn(R-phox) 3 ] catalysts, 22,23 which could be the result of the increased steric bulk on the axial sites.…”

“…Of the substrates tested, cyclohexene results in the highest conversion. In general, the complexes show comparable conversion for cyclooctene and 1-octene, the exception being RS-1, for which the turnovers in cyclooctene (30) are considerably higher than for 1-octene (22). Important to note here is the epoxidation of 1-octene, for which 10 to 23 turnovers in the epoxide product were obtained by the above complexes.…”

“…The unsubstituted Mn−salen complex showed no catalytic conversion of olefins, while the complex containing the tethered imidazole showed almost complete conversions of olefins using dihydrogen peroxide as the oxidant. In the [Mn(phox) 3 ]-catalyzed epoxidations, [Mn(phox) 2 ( N -Meim)] + has been found to be the major species present during catalysis. , Thus, coordination of the nitrogen-containing base has been assumed to be important for oxo transfer.…”

“…The Mn-N and Mn-O (axial carboxylate) distances are similar to those observed in other Mn(III) complexes. [21][22][23]35,36 The hydrogen bonds donated by the diethylammonium protons to the carboxylate groups of the manganese complexes link the molecules into infinite one-dimensional chains running parallel to the a axis. Details of the hydrogen bonding interactions are given in the Supporting Information (Table S1).…”

One-Pot Synthesis of Chiral Organometallic Complexes

“…Chiral oxazolinyl organometallic complexes are very important catalysts in organic chemistry [14][15][16][17][18][19][20][21][22]. Several organometallic complexes containing 2-(2′-hydroxyphenyl) oxazolines are reported in the literature [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. The general approach to the synthesis of metal complexes begins with ligand synthesis, followed by ligand reaction with metal salts to afford organometallic complexes [43].…”

Stereochemical Influence of the Ligand on the Structure of Manganese Complexes: Implications for Catalytic Epoxidations

“…52 A higher reactivity for 1-octene by the present compounds, compared to that of [Mn(phox) 3 ], is expected because the presence of electron-withdrawing substituents is known to result in a higher number of epoxide turnovers for this substrate. 9 However, for other alkenes, the complexes show lower turnover numbers, compared to that of the previously studied [Mn(R-phox) 3 ] catalysts, 22,23 which could be the result of the increased steric bulk on the axial sites.…”

“…Of the substrates tested, cyclohexene results in the highest conversion. In general, the complexes show comparable conversion for cyclooctene and 1-octene, the exception being RS-1, for which the turnovers in cyclooctene (30) are considerably higher than for 1-octene (22). Important to note here is the epoxidation of 1-octene, for which 10 to 23 turnovers in the epoxide product were obtained by the above complexes.…”

“…The unsubstituted Mn−salen complex showed no catalytic conversion of olefins, while the complex containing the tethered imidazole showed almost complete conversions of olefins using dihydrogen peroxide as the oxidant. In the [Mn(phox) 3 ]-catalyzed epoxidations, [Mn(phox) 2 ( N -Meim)] + has been found to be the major species present during catalysis. , Thus, coordination of the nitrogen-containing base has been assumed to be important for oxo transfer.…”

“…The Mn-N and Mn-O (axial carboxylate) distances are similar to those observed in other Mn(III) complexes. [21][22][23]35,36 The hydrogen bonds donated by the diethylammonium protons to the carboxylate groups of the manganese complexes link the molecules into infinite one-dimensional chains running parallel to the a axis. Details of the hydrogen bonding interactions are given in the Supporting Information (Table S1).…”

One-Pot Synthesis of Chiral Organometallic Complexes

“…Chiral oxazolinyl organometallic complexes are very important catalysts in organic chemistry [14][15][16][17][18][19][20][21][22]. Several organometallic complexes containing 2-(2′-hydroxyphenyl) oxazolines are reported in the literature [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. The general approach to the synthesis of metal complexes begins with ligand synthesis, followed by ligand reaction with metal salts to afford organometallic complexes [43].…”