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Rhenium carbonyl complexes with monodentate-coordinated diphosphines
Author
Fan, Wei
Supervisor
Yan, Yaw Kai
Abstract
The amine oxide-assisted decarbonylation of [Re2(CO) sub>10] followed by reaction with excess diphosphine produces the monodentate-coordinated diphosphine complexes [Re2(CO9(η1 -P-P)] the open-bridge dimers [{Re2(CO)9)2(μ-P-P)] [P-P = Ph2P(CH2),PPh2, n = 1-6; trans- 1,2-bis~diphenylphosphino)ethyiene (dppet) and 1-di(c-anisyl)phosphino-3-diphenlylphosphino)ethylene (dadpp)].
Reaction of [Re2(CO)9(n1-P-)] (P-P] = Ph2P(CH2)nPPh2, n = 1-6) with TMNO (trimethylamine N-oxide) yields the close-bridged complexes dieq-[Re2(C0)8(μ-P-P)] and the phosphine oxide complexes [Re2(C0)9{P-P(0))]. The yields of the close-bridge complexes decrease with the increase of the length of the carbon chain of the diphosphines. The yields of the phosphine oxide complexes increase first with the increase of the carbon chain of the diphosphines, with the highest yield obtained with dppp (n = 3). Yields decrease again for diphosphines with n≥4.
The failure to oxidize the free phosphine by TMNO suggests that the formation of phosphine oxide complexes in the reaction of [Re2(CO)9(n1-P-P)] with TMNO is not a straightforward transfer of the oxygen atom from the amine-oxide to the free phosphine group of [Re2(CO)9(n1-P-P)].
Mechanistic studies of the formation of the phosphine oxide complexes were carried out. The results suggest a mechanism which involves the interaction of the free phosphino group in the molecule of [Re2(CO)9(n1-P-P)] with an adjacent CO group.
Studies also show that the perrhenate ion does not play an important part in the formation of the phosphine oxide complexes in the reactions of [Re2(CO)9(n1-P-P)] with TMNO.
Reaction of [Re2(CO)9(n1-P-)] (P-P] = Ph2P(CH2)nPPh2, n = 1-6) with TMNO (trimethylamine N-oxide) yields the close-bridged complexes dieq-[Re2(C0)8(μ-P-P)] and the phosphine oxide complexes [Re2(C0)9{P-P(0))]. The yields of the close-bridge complexes decrease with the increase of the length of the carbon chain of the diphosphines. The yields of the phosphine oxide complexes increase first with the increase of the carbon chain of the diphosphines, with the highest yield obtained with dppp (n = 3). Yields decrease again for diphosphines with n≥4.
The failure to oxidize the free phosphine by TMNO suggests that the formation of phosphine oxide complexes in the reaction of [Re2(CO)9(n1-P-P)] with TMNO is not a straightforward transfer of the oxygen atom from the amine-oxide to the free phosphine group of [Re2(CO)9(n1-P-P)].
Mechanistic studies of the formation of the phosphine oxide complexes were carried out. The results suggest a mechanism which involves the interaction of the free phosphino group in the molecule of [Re2(CO)9(n1-P-P)] with an adjacent CO group.
Studies also show that the perrhenate ion does not play an important part in the formation of the phosphine oxide complexes in the reactions of [Re2(CO)9(n1-P-P)] with TMNO.
Date Issued
1999
Call Number
TA480.R5 Fan
Date Submitted
1999