Triarylamminium radical-cation complexes: design and magnetic properties and Base-catalyzed hydrosilylation: mechanism and substrate scope

1. Triarylamminium radical-cation complexes. The detailed study of manganese, copper and nickel metal-radical complexes with triarylamminium ligands was conducted. Stable, neutral and pseudo-octahedral coordination monometallic complexes with simple monodentate 2,2`-bipyridine ligand containing a redox-active N,N`-(4,4`-dimethoxydiphenyl-amino) substituent were synthesized and fully characterized. The one-electron oxidation process and formation of persistent radical-cation complexes was observed by cyclic voltammetry and spectroelectrochemical measurements. Evans method measurements were performed with radical-cation complexes generated by chemical one-electron oxidation with NOPF6 in acetonitrile. The experimental results indicate ferromagnetic coupling between metal and triarylamminium cation in manganese (II) complex and antiferromagnetic coupling in nickel (II) complex. This data is supported by DFT calculations which also lend weight to the  spin polarization mechanism as an operative model for magnetic exchange coupling. Neutral bimetallic complexes with a new ditopic ligand were synthesized and fully characterized, including magnetic and electrochemical studies. Chemical oxidation of these precursor complexes did not generate radical-cations, but dicationic complexes, which was confirmed by UV-vis and EPR-experiments, as well as varied temperature magnetic measurements. DFT calculations for radical-cation complexes are included. A synthetic pathway for polytopic ligand with multiple redox-active triarylamine sites was developed. The structure of the ligand is presumably suitable for -spin polarization exchange model and allows for production of polymetallic complexes having high spin ground states. 2. Base-catalyzed hydrosilylation. A simple reductive base-catalyzed hydrosilation of aldehydes and ketones was adapted to the use of the cheap, safe, and non-toxic polymethylhydrosiloxane (PMHS) instead of the common PhSiH3 and (EtO)3SiH, which present significant cost and safety concerns, respectively. The conversion of silane into pentacoordinate silicate species upon addition of a base was studied in details for the cases of phenyl silane and PMHS and is believed to be essential for the hydrosilylation process. We discovered that nucleophiles (a base or fluoride-anion) induced the rearrangement of PMHS and TMDS into light silanes: MeSiH3 and Me2SiH2, respectively. The reductive properties of PMHS under basic conditions can be attributed to the formation of methyl silane and its conversion into a silicate species. A procedure for the generation of methyl silane and its use in further efficient reductions of aldehydes and ketones has been developed. The protocol was extended to the selective reduction of esters and tertiary amides into alcohols and aldimines into amines with good isolated yields and reduction of heterocyclic compounds was attempted.

Science Complex Opening

Pictured here from left to right are James Gibson, President Emeritus, R. A. Macleod, Board of Trustees, and Dr. Cecil Shaver, former Chancellor, during the 1984 Science Complex opening - an addition to the Mackenzie Chown Complex now simply known as H Block.

Science Complex Opening

Pictured here from left to right are Henry Tomarin, Board of Trustees, St. Catharines Mayor Roy Adams, R. Campbell, Niagara Region chairman, Peter Misener, and R. Misener, Chancellor, during the 1984 Science Complex opening - an addition to the Mackenzie Chown Complex now simply known as H Block.

Science Complex Opening

Dr. Earp unveils a sign at the joint Science Complex opening ceremony and the Academic Staging Building renaming ceremony. The Academic Staging Building was henceforth called the Mackenzie Chown Complex.

Science Complex Opening

Dr. Alan Earp speaks at the opening ceremony for the Science Complex addition in 1984.

Science Complex Opening

Doris Chown speaking at the Science Complex Opening and the unveiling of a sign in conjunction with the renaming of the Academic Staging Building to the Mackenzie Chown Complex.

Science Complex Opening

Robert S. K. Welch celebrates the opening of the new Science Complex wing, an addition to the Mackenzie Chown Complex, as Dr. Alan Earp (pictured behind Welch) and others look on. The new name for the Academic Staging Building was also unveiled. It was renamed after former mayor Mackenzie Chown.

Science Complex Opening

Rather then cutting a piece of red tape with scissors, the Science students at Brock prepared a laser devise to cut through a specially made piece of metallic ribbon for the opening ceremony of the Science Complex addition. Pictured here is Robert Welch with the laser device as he attempts to 'cut' the tape. Unfortunately the device failed and Dr. Earp resorted to cutting the tape with a Swiss Army knife he had on hand.

Greenhouse and Science Complex

The Aumni Greenhouse and the Science Complex in the background.

Complex Model

Mackenzie Chown Complex model.

Complex Model

View of the Mackenzie Chown Complex model from above.

Science Complex Model

A model showing the Mackenzie Chown complex and the H Block addition.

Complex takes shape

View of the progress of the Mackenzie Chown Complex several months into construction.

Science Complex Construction

Initial groundwork taking place during the construction of the addition.

Science Complex Construction

Early groundwork continues during the construction of the addition.