TY - JOUR

T1 - Rhodium complexes containing arylspiroborates derived from 3,5-di-tert-butylcatechol and their use in catalyzed hydroborations

AU - Geier, Michael J.

AU - Geier, Stephen J.

AU - Halcovitch, Nathan R.

AU - Vogels, Christopher M.

AU - Decken, Andreas

AU - Westcott, Stephen A.

PY - 2013/3/22

Y1 - 2013/3/22

N2 - Tl(acac) reacts quantitatively with B2butcat3 (butcat = 3,5-di-tert-butylcatecholato) to give butcatB(acac) and Tl(Bbutcat 2) (1), the latter of which is soluble in common organic solvents such as THF and dichloromethane. Addition of 1 to a mixture of [RhCl(coe) 2]2 (coe = cis-cyclooctene) and diphosphine in THF gave the thallium bridged dinuclear complexes [(P2)Rh(μ-Cl) 2(μ-Tl)Rh(P2)][Bbutcat2] (2-5, P2 is dppm = 1,1′-bis(diphenylphosphino)methane, dppe = 1,2- bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane and dppb = 1,4-bis(diphenylphosphino)butane) as the only new rhodium containing species. Unsymmetrical binding of the thallium atom is observed in some cases owing to a secondary interaction with the phenyl rings of the phosphine ligands. Mononuclear cationic species of the type [(P2)Rh(NCCH 3)2][Bbutcat2] (6-9) were formed when reactions were carried out in acetonitrile, where preferential binding of the solvent was observed over the bulky arylspiroborate ligand. The zwitterionic species Rh(η6-butcatBbutcat)(P2), 11 and 12, could be generated via a different route, by addition of B2butcat3 to Rh(acac)(P2), but only for the sterically-constrained diphosphines dppm and dppe, respectively. While all new complexes effectively catalyzed the addition of catecholborane to 4-vinylanisole and α-methylstyrene, product distributions suffered from a competing dehydrogenative borylation pathway.

AB - Tl(acac) reacts quantitatively with B2butcat3 (butcat = 3,5-di-tert-butylcatecholato) to give butcatB(acac) and Tl(Bbutcat 2) (1), the latter of which is soluble in common organic solvents such as THF and dichloromethane. Addition of 1 to a mixture of [RhCl(coe) 2]2 (coe = cis-cyclooctene) and diphosphine in THF gave the thallium bridged dinuclear complexes [(P2)Rh(μ-Cl) 2(μ-Tl)Rh(P2)][Bbutcat2] (2-5, P2 is dppm = 1,1′-bis(diphenylphosphino)methane, dppe = 1,2- bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane and dppb = 1,4-bis(diphenylphosphino)butane) as the only new rhodium containing species. Unsymmetrical binding of the thallium atom is observed in some cases owing to a secondary interaction with the phenyl rings of the phosphine ligands. Mononuclear cationic species of the type [(P2)Rh(NCCH 3)2][Bbutcat2] (6-9) were formed when reactions were carried out in acetonitrile, where preferential binding of the solvent was observed over the bulky arylspiroborate ligand. The zwitterionic species Rh(η6-butcatBbutcat)(P2), 11 and 12, could be generated via a different route, by addition of B2butcat3 to Rh(acac)(P2), but only for the sterically-constrained diphosphines dppm and dppe, respectively. While all new complexes effectively catalyzed the addition of catecholborane to 4-vinylanisole and α-methylstyrene, product distributions suffered from a competing dehydrogenative borylation pathway.

KW - Arylspiroborates

KW - Boron

KW - Catalysis

KW - Hydroboration

KW - Rhodium

KW - Zwitterions

U2 - 10.1016/j.poly.2012.06.048

DO - 10.1016/j.poly.2012.06.048

M3 - Journal article

AN - SCOPUS:84875451811

VL - 52

SP - 1181

EP - 1189

JO - Polyhedron

JF - Polyhedron

SN - 0277-5387

ER -