Development and Catalytic Activity of Half-Sandwich Ruthenium(II) Complexes Featuring Derivatives of PTA (1,3,5-triaza-7-phosphaadamantane)
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Authors
Eubanks, William L
Issue Date
2025
Type
Dissertation
Language
en_US
Keywords
Alternative Title
Abstract
Two new upper-rim enamine derivatives of 1,3,5-triaza-7-phosphaadamantane (PTA, an air-stableand water-soluble phosphine ligand), PTA=C(p-C6H4
tBu)NH2 and PTA=C(p-C6H4Ph)NH2, were
synthesized by the addition of the corresponding nitriles across the C–Li bond of 1,3,5-triaza-7-
phosphaadamantan-6-yllithium (PTA–Li). Like the parent PTA, these new ligands exhibit excellent
resistance to P-oxidation by atmospheric O2. However, the hydrocarbon groups render them
completely insoluble in water.
A range of cyclopentadienylruthenium(II) complexes containing these ligands and other enamines
made in our group have been synthesized by treatment of [CpRuCl(PPh3)2] with the ligands in
hot toluene under anaerobic conditions. The bright yellow powders that precipitated during these
reactions were analyzed by 31P NMR spectroscopy and found to be the monodentate, mixed-
phosphine complexes [CpRuCl{κ1-PTA=C(Ar)NH2}(PPh3)] rather than the expected bidentate
species [CpRuCl{κ2-PTA–C(Ar)=NH}]. The attempted abstraction of Cl– from the monodentate
complexes with TlPF6 did not induce chelation.
The PTA–enamine complexes [CpRuCl{κ1-PTA=C(Ar)NH2}(PPh3)] were tested as catalysts
for the atom-transfer radical addition of CCl4 to styrene in deuterated toluene, deuterated methanol,
and deuterated acetonitrile. The insolubility of the catalysts in toluene made them ineffective in
that solvent. For methanol and acetonitrile, wherein thecatalysts are slightly soluble at the reaction
temperature of 60◦C, percent conversions (styrene, 24 h) of 50–78% and yields of 4.0–11.5% were
found. Turnover frequencies ranged from 0.17 to 0.48 h−1 at 1 mol% catalyst loading.
Separately, a range of areneruthenium(II) complexes of water-soluble PTA–pyridyl ligands PTA–CH(2-py)OH and PTA–CH(3-py)OH were tested as catalysts for the aqueous-phase aerobic
hydration of benzonitrile. Percent conversions (7 h) ranged from 5% to 90% and turnover frequencies
from 0.2 to 2.6 h−1 at 5 mol% catalyst loading. The best-performing catalyst containing each ligand
was tested against a wider range of nitriles; water-soluble, electron-rich nitriles were found to be the
best substrates.