Date of Award

Spring 5-15-2015

Author's School

Graduate School of Arts and Sciences

Author's Department

Chemistry

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

This dissertation focuses on the systematic synthesis of ¬bis-azapentadienyl-ruthenium-phosphine complexes. The synthetic approach involves the treatment of Cl2Ru(PPh3)3 with potassium tert-butylazapentadienide reagent. The reactivity of this parent compound with other 2e- donor ligands is investigated. These resultant complexes' reactivity with triflic acid is also studied.

Treatment of Cl2Ru(PPh3)3 with potassium tert-butylazapentadienide produces [(1,2,3-η3)-5-tert-butylazapentadienyl]2Ru(PPh3)2 (1). Compound 1 undergoes single substitution of one of the triphenylphosphines when treated with PMe3, dmpe, P(OMe)3, CNCMe3, CO, and PEt3 at room temperature, resulting in [(1,2,3-η3)-5-tert-butylazapentadienyl]2Ru(PPh3)(L) (2, L = PMe3; 3, L= dmpe; 4, L = P(OMe)3; 5, L = CNCMe3; 6, L = CO; 7, L = PEt3). By increasing the reaction time of 1 with PEt3, double substitution of both triphenylphosphines occurs, resulting in [(1,2,3-η3)-5-tert-butylazapentadienyl]2Ru(PEt3)2 (8). Compounds 1 - 8 possess a pseudo-octahedral geometry where both ancillary ligands sit trans to the C3's of the azapentadienyl ligands. Compounds 1 - 4, 7 and 8 exhibit a ligand orientation in which both ancillary ligands sit in the mouth of each azapentadienyl ligand, denoted as mC3/mC3. In contrast, 5 exhibits a ligand arrangement where the PPh3 sits in the mouth of one azapentadienyl ligand while CNCMe3 sits on the backbone of the other azapentadienyl ligand.

Other double substitution reactions occur when 1 is treated with PMe3, P(OMe)3, and dmpe in THF at reflux, resulting in [(1,2,3-η3)-5-tert-butylazapentadienyl]2Ru(L)x (9, L = PMe3, x = 2; 10, L = P(OMe3), x = 2; 11, L = dmpe, x = 1). Compounds 9 and 10 exist in solution as an equilibrium mixture of two structural isomers. The two isomers in solution have either a mC3/mC3 or mC3/bC1 ligand orientation.

Treatment of 8, 9 and 10 with triflic acid results in dicationic products, {[(1,2,3-η3)-(CH2CHCHCH=N(H)(CMe3)]2Ru(L)2}2+(-O3SCF3)2 (12, L = PEt3; 13, L = PMe3; 14, L = P(OMe)3), in which both azapentadienyl nitrogen atoms have been protonated. The protonated product, 12, shows a ligand conversion from mC3/mC3 (seen in 8) to mC3/bC3. Upon protonation, 9 and 10 each convert to a single isomer, 12 and 13, respectively. Like 12, compound 13 possesses a mC3/bC3 orientation while 14 has a ligand orientation in which the azapentadienyl ligands appear to be mC3/mC3. Treatment of 2, 4 and 5 with triflic acid results in multiple isomers of the diprotonated {[(1,2,3-η3)-CH2CHCHCH=N(H)(CMe3)]2Ru(PPh3)(L)}2+(-O3SCF3)2 (15, L = PMe3; 16, L = P(OMe)3; 17, L = CNCMe3). All of the compounds have been characterized, in part, by NMR spectroscopy, and the structures of 2, 4, 5, 7, 8, and 12 have been confirmed by single-crystal X-ray diffraction.

Language

English (en)

Chair and Committee

John R Bleeke

Committee Members

Bill Buhro, Liviu Mirica, Sophia Hayes, Nigam Rath

Comments

Permanent URL: https://doi.org/10.7936/K79S1P7R

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