Synthetic, structural, and reactivity investigations of neutral, cationic, and zwitterionic rhodium(I), iridium(I), and manganese(I) derivatives of phosphorus,nitrogen-substituted indenes.
Date
2007
Authors
Cipot, Judy.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Cationic rhodium and iridium complexes incorporating mixed donor bidentate P,N ancillary ligands are effective in mediating certain homogeneous catalytic reactions. However, two disadvantages of cationic catalysts that potentially limit their synthetic utility include: (1) their poor solubility properties; and (2) the somewhat unpredictable nature of the outersphere counteranion on the catalytic performance of the complex. The development of alternative charge-neutral formally zwitterionic catalysts to overcome these challenges has received some attention, although the range of suitable anionic ligands to support Rh and Ir zwitterionic complexes remains limited. In the research presented in this thesis, a fundamentally new heterobidentate P,N ligand (1-P iPr2-2NMe2-indene, 2-2) has been prepared from readily available starting materials.
The ability of 2-2 to support Mn(I), Rh(I) and Ir(I) neutral and cationic metal fragments has been demonstrated. Interestingly, 2-2 can be deprotonated to form a 10pi-indenide unit (2-2e ) which can coordinate a cationic Rh or Ir fragment in the kappa 2-P,N chelate site to generate entirely new heterobidentate formally zwitterionic complexes. A comparison of the catalytic properties of these zwitterions with their isostructural and isosteric cationic relatives has provided the opportunity to assess the impact of altering only the electronic characteristics of a formally cationic metal fragment. These Rh and Ir zwitterions are effective catalysts for the hydrogenation and hydrosilylation of alkenes; their solubility and reactivity properties are in some instances divergent from and superior to those of more traditional Rh and Ir salts. In addition, these cationic [(kappa2-P,N- 2-2)M(COD)]+X- and zwitterionic (kappa 2-P,N-2-2e)M(COD) complexes represent a complementary family of catalysts for the addition of E-H bonds to alkenes, when issues of catalytic activity/selectivity and solvent compatibility are considered.
Under appropriate reaction conditions, the (kappa2- P,N)M(COD) catalysts (M = Rh, Ir) can be transformed into the corresponding (kappa2-P,O)M(COD) complexes featuring 1-P iPr2-2-O-indene. This neutral kappa2 -P,O-Ir(I) complex 5-2 is able to reduce alkenes under very mild reaction conditions (∼1 atm H2, 22°C) in a range of solvents including hexanes, benzene, THF, CH2Cl 2, and CH3CN. Notably, 5-2 represents the most active neutral Ir(I) alkene hydrogenation catalyst known.
Thesis (Ph.D.)--Dalhousie University (Canada), 2007.
The ability of 2-2 to support Mn(I), Rh(I) and Ir(I) neutral and cationic metal fragments has been demonstrated. Interestingly, 2-2 can be deprotonated to form a 10pi-indenide unit (2-2e ) which can coordinate a cationic Rh or Ir fragment in the kappa 2-P,N chelate site to generate entirely new heterobidentate formally zwitterionic complexes. A comparison of the catalytic properties of these zwitterions with their isostructural and isosteric cationic relatives has provided the opportunity to assess the impact of altering only the electronic characteristics of a formally cationic metal fragment. These Rh and Ir zwitterions are effective catalysts for the hydrogenation and hydrosilylation of alkenes; their solubility and reactivity properties are in some instances divergent from and superior to those of more traditional Rh and Ir salts. In addition, these cationic [(kappa2-P,N- 2-2)M(COD)]+X- and zwitterionic (kappa 2-P,N-2-2e)M(COD) complexes represent a complementary family of catalysts for the addition of E-H bonds to alkenes, when issues of catalytic activity/selectivity and solvent compatibility are considered.
Under appropriate reaction conditions, the (kappa2- P,N)M(COD) catalysts (M = Rh, Ir) can be transformed into the corresponding (kappa2-P,O)M(COD) complexes featuring 1-P iPr2-2-O-indene. This neutral kappa2 -P,O-Ir(I) complex 5-2 is able to reduce alkenes under very mild reaction conditions (∼1 atm H2, 22°C) in a range of solvents including hexanes, benzene, THF, CH2Cl 2, and CH3CN. Notably, 5-2 represents the most active neutral Ir(I) alkene hydrogenation catalyst known.
Thesis (Ph.D.)--Dalhousie University (Canada), 2007.
Keywords
Chemistry, Inorganic.