TY - JOUR
T1 - Multinuclear magnesium hydride clusters
T2 - Selective reduction and catalytic hydroboration of pyridines
AU - Intemann, Julia
AU - Lutz, Martin
AU - Harder, Sjoerd
PY - 2014/10/27
Y1 - 2014/10/27
N2 - Multinuclear magnesium hydride complexes react with pyridine, forming 1,2- and 1,4-dihydropyridide (DHP) complexes. Reaction of PARA3Mg8H10 with pyridine initially formed 1,2-DHP and 1,4-DHP product mixtures which converted at 60 °C into PARA-[Mg(1,4-DHP)]2·(pyridine)2 (PARA = [(2,6-iPr2C6H3)NC(Me)C(H)C(Me)N]2-(p-C6H4)). Reaction of [NN-(MgH)2]2 with pyridine gave exclusive formation of the 1,2-DHP product NN-[Mg(1,2-DHP)]2·(pyridine)2 (NN = [(2,6-iPr2C6H3)NC(Me)CHC(Me)N-]2). Both products were characterized by crystal structure determinations. The unusual preference for 1,2-addition is likely caused by secondary intramolecular interactions based on mutual communication between the metal coordination geometries: an extended network of C-H···C π-interactions and π-stacking interactions is found. Whereas PARA3Mg8H10 is hardly active in magnesium-catalyzed hydroboration of pyridines with pinacolborane, [NN-(MgH)2]2 shows efficient coupling. However, the regioselectivity of the stoichiometric reaction is not translated to the catalytic regime. This result is taken as an indication for a potential alternative mechanism in which magnesium hydride intermediates do not play a role but the hydride is transferred from an intermediate borate complex.
AB - Multinuclear magnesium hydride complexes react with pyridine, forming 1,2- and 1,4-dihydropyridide (DHP) complexes. Reaction of PARA3Mg8H10 with pyridine initially formed 1,2-DHP and 1,4-DHP product mixtures which converted at 60 °C into PARA-[Mg(1,4-DHP)]2·(pyridine)2 (PARA = [(2,6-iPr2C6H3)NC(Me)C(H)C(Me)N]2-(p-C6H4)). Reaction of [NN-(MgH)2]2 with pyridine gave exclusive formation of the 1,2-DHP product NN-[Mg(1,2-DHP)]2·(pyridine)2 (NN = [(2,6-iPr2C6H3)NC(Me)CHC(Me)N-]2). Both products were characterized by crystal structure determinations. The unusual preference for 1,2-addition is likely caused by secondary intramolecular interactions based on mutual communication between the metal coordination geometries: an extended network of C-H···C π-interactions and π-stacking interactions is found. Whereas PARA3Mg8H10 is hardly active in magnesium-catalyzed hydroboration of pyridines with pinacolborane, [NN-(MgH)2]2 shows efficient coupling. However, the regioselectivity of the stoichiometric reaction is not translated to the catalytic regime. This result is taken as an indication for a potential alternative mechanism in which magnesium hydride intermediates do not play a role but the hydride is transferred from an intermediate borate complex.
UR - http://www.scopus.com/inward/record.url?scp=84908635411&partnerID=8YFLogxK
U2 - 10.1021/om500469h
DO - 10.1021/om500469h
M3 - Article
AN - SCOPUS:84908635411
SN - 0276-7333
VL - 33
SP - 5722
EP - 5729
JO - Organometallics
JF - Organometallics
IS - 20
ER -