This thesis presented the synthesis and reactivity of metal complexes for the
hydrophosphination of alkenes and dehydrocoupling of phosphines. The mechanism of
these metal-catalyzed P-H activation reactions was explored. Half-sandwich Cp*Ru complexes (Cp*= 1,2,3,4,5-pentamethylcyclopentadienyl)
were developed as catalysts for hydrophosphination, based on the previous work in the
Rosenberg group. Cp*Ru phosphido complexes, Ru(h 5 -Cp*)(PR2 )(PR2 H)2 (Ru-1) were
found to be the vital intermediates for the hydrophosphination. Preliminary mechanistic
studies also indicate that the catalyst resting state is Ru(h5 -Cp*)(PR2 )(PR2 H)(P) (P =
hydrophosphination product) and intramolecular P-H bond cleavage is turnover-limiting.
These investigations provide sufficient parallels to our established chemistry of the indenyl
analogues to imply that conjugate addition of metal phosphido at alkene plays a significant
role in these half-sandwich catalytic systems. The increased steric crowding at the Cp*Ru
fragment and P-basicity/nucleophilicity of its phosphido complexes lead to a 30-fold
increase in the hydrophosphination activity in the Cp* system compared to the indenyl
catalysts.
A half-sandwich Co catalyst, Co(h 5 -Cp*)I 2 (CO) (Co-1), was also developed for
hydrophosphination along the lines of the conjugate addition mechanism. Similar to the
Cp*Ru system, the substrate scope for alkene is limited to electron-deficient alkene.
However, the Cp*Co catalyst significantly expands the substrate scope for phosphines
(PR2 H and PRH 2 , R = alkyl and aryl). A detailed mechanistic study on the Cp*Co system
was performed. The results show that the Co-catalyzed hydrophosphination occurs through
iv
an outer-sphere mechanism and the stoichiometric formation of diphosphine is a critical
catalyst activation step.
Since the side product diphosphine was formed during the Co-catalyzed
hydrophosphination, using complex Co-1 as a catalyst for dehydrocoupling phosphines
was investigated. The preliminary studies reveal the role of base and Cp* ligand in the
catalysis. Additionally, the study highlights the importance of removing dihydrogen
throughout the process. Thus, hydrogen acceptors (HA) were used to facilitate the
dehydrocoupling reactions. Last, the novel P-H activation process between Cp*Co
complexes [Co(h5 -Cp*)(NCCH 3 ) 3 ][SbF 6 ] 2 (Co-5) and excess PPh2 H was investigated
through various analytical techniques. / Graduate / 2023-09-08
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/14255 |
| Date | 22 September 2022 |
| Creators | Yang, Jin |
| Contributors | Rosenberg, Lisa |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
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