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Synthesis of dirhenium(I) hexacarbonyl complexes bridged by bis(bidentate) ligands
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Type
Thesis
Author
Kee, Chee Leong
Supervisor
Yan, Yaw Kai
Abstract
The chemistry of dirhenium(I) hexacarbonyl complexes bridged by bis(bidentate) ligands is studied. It includes: (i) studies on the decarbonylation of µ-dithiooxalato-(S,S) bis(pentacarbonylrhenium) and µ-oxalato-(O,O) bis(pentacarbonylrhenium) followed by reaction with different ligands; (ii) synthesis of tetrathiooxalate (tto) complexes using different methodologies; (iii) synthesis of dithiooxamidate (dtox) complexes using [Re(CO)5(OTf)] and dithiooxamide (H2dtox); (iv) synthesis and characterization of 2,2′-bipyrimidine (bpym) and 2,3-bis-(2-pyridyl)pyrazine (dpp) complexes; and (v) cytotoxicity studies on human cancer cells.
The complex [{Re(CO)5}2(µ,η1:η1- C2S2O2)], 1 undergoes thermal decarbonylation to form [Re2(CO)6(µ,η2:η2-C2S2O2)]n, 2 which reacts with trans1,2-bis(diphenylphosphino)ethylene (dppene), 1,1′-bis(diphenylphosphino)ferrocene (dppf), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos), 1,3-bis(diphenylphosphinoamino)benzene (mdpab), 1,4-bis(diphenylphosphinoamino)benzene (p-dpab), 1,3-bis(diphenylphosphino)propane (dppp), triphenylphosphine (PPh3), pyridine (pyr), guanosine (G), pyrazine (pyz) and 4,4′-bipyridine (bpy) to give [Re2(µdppene)(CO)6(µ,η2:η2-C2S2O2)], 3; [Re(µ-dppf)(CO)6(µ,η2:η2-C2S2O2)], 4; [Re2(µ-Xantphos)(CO)6(µ,η2:η2-C2S2O2)], 5; [Re2(µ-m-dpab)(CO)6(µ,η2:η2-C2S2O2)], 6; [Re2(µ-p-dpab)(CO)6(µ,η2:η2-C2S2O2)], 7; [Re2(µdppp)(CO)6(µ,η2:η2-C2S2O2)], 8; anti- [Re(PPh3)2(CO)6(µ,η2:η2-C2S2O2)], 9; anti- [Re(pyr)2(CO)6(µ,η2:η2-C2S2O2)], 10; anti- [Re(G)2(CO)6(µ,η2:η2-C2S2O2)] 11; [{Re2(CO)6(µ,η2:η2-C2S2O2)(µ,η1:η1-pyz)}2], 12 and [{Re2(CO)6(µ,η2:η2-C2S2O2)(µ,η1:η1-bpy)}2], 13 respectively. Isomerization effects of compounds 10 and 13 can be distinguished by 2D NMR spectroscopy.
On the other hand, the reactions of decarbonylated [{Re(CO)5}2(µ,η1:η1-C2O4)] with dppp and [N, N-bis(diphenylphosphinomethyl)amino]pyridine (PNP) give [(η2-dppp)Re(CO)3(µ,η1:η1-C2O4)Re(CO)3(η2-dppp)], 22 and [(η2-PNP)Re(CO)3(µ,η1:η1-C2O4)Re(CO)3(η2-PNP)], 23 respectively. Reaction with dppf gives [Re2(µ-OPPh2(C5H4)Fe(C5H4)PPh2)(CO)6(µ,η2:η2-C2O4)], 24.
The compound [Re2(µ-dppene)(CO)6(µ,η2:η2-C2S4)], 14 is obtained by two different routes, (i) reaction between [Re(thf)3(CO)3]+ and [NEt4]2[C2S4] and (ii) [Re(OH2)3(CO)3]Br and [NEt4]2[C2S4], each followed by reaction of the intermediate formed with dppene. The molecular rectangle [{Re2(CO)6(µ,η2:η2-C2S4)(µ,η1:η1-bpy)}2], 16 can be obtained via reaction between [{Re(CO)5}2(µ,η1:η1-bpy)] and [NEt4]2[C2S4].
The complexes [Re2(µ-PP)(CO)6(µ,η2:η2-C2H2N2S2)] (PP = dppene, 17; mdpab, 18, dppf, 19) are synthesized from the decarbonylation of [Re(CO)5(OTf)] in the presence of H2dtox. Compound 17 consists of two isomers; S-cis-[Re2(µdppene)(CO)6(µ,η2:η2-C2H2N2S2)], 17A and S-trans-[Re2(µdppene)(CO)6(µ,η2:η2-C2H2N2S2)], 17B, which can be differentiated by their δ(NH) IR absorption characteristics, and NMR spectra. The analogous reaction between [Re(CO)52oxa) affords [Re2(µdppene)(CO)6(µ,η2:η2-C2H2N2O2)], 20 and [Re2(µ-dppene)2(CO)6(CF3SO3)2], 21.
A series of cationic complexes [Re2(µ-PP)(CO)6(µ,η2:η2-bpym)][BF4]2 (PP = dppp, 25; 1,4- bis(diphenylphosphino)butane (dppb), 26; 1,5-bis(diphenylphosphino)pentane (dpppe), 27; 1,6- bis(diphenylphosphino)hexane (dpph), 28) have also been synthesized from the reaction of [Re(thf)3(CO)3]+ with bpym. These complexes show two maxima at 323 and 472 nm in the UV-vis spectra, indicating the intraligand (IL) and metal-ligand charge transfer (MLCT). No dirhenium complex can be obtained using dpp as ligand. Compounds [ReBr(CO)3(η2-dpp)], 29 and [ReBr(CO)3(η2-dppp)], 30 are obtained from the reaction between [ReBr3(CO)3]2-, dppp and dpp in a solvent mixture (MeOH : THF=1:1) while [Re(CO)3(FBF3)(η2-dpppe)], 31 and [Re(CO)3(FBF3)(η2-dpp)], 32 are formed from the reaction between[Re(thf)3(CO)3]+, dpppe and dpp.
Complexes 3, 4, 5, 9, 10, 14, 17 and [Re2(µ-dppene)(CO)6(µ,η2:η2-C2O4)] (oxdppene) were tested for their cytotoxicity towards two cancer cell lines. Some of the complexes inhibit the growth of MOLT-4 human leukemia cells but none of them show any activity against MCF-7 breast cancer cells.
The complex [{Re(CO)5}2(µ,η1:η1- C2S2O2)], 1 undergoes thermal decarbonylation to form [Re2(CO)6(µ,η2:η2-C2S2O2)]n, 2 which reacts with trans1,2-bis(diphenylphosphino)ethylene (dppene), 1,1′-bis(diphenylphosphino)ferrocene (dppf), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos), 1,3-bis(diphenylphosphinoamino)benzene (mdpab), 1,4-bis(diphenylphosphinoamino)benzene (p-dpab), 1,3-bis(diphenylphosphino)propane (dppp), triphenylphosphine (PPh3), pyridine (pyr), guanosine (G), pyrazine (pyz) and 4,4′-bipyridine (bpy) to give [Re2(µdppene)(CO)6(µ,η2:η2-C2S2O2)], 3; [Re(µ-dppf)(CO)6(µ,η2:η2-C2S2O2)], 4; [Re2(µ-Xantphos)(CO)6(µ,η2:η2-C2S2O2)], 5; [Re2(µ-m-dpab)(CO)6(µ,η2:η2-C2S2O2)], 6; [Re2(µ-p-dpab)(CO)6(µ,η2:η2-C2S2O2)], 7; [Re2(µdppp)(CO)6(µ,η2:η2-C2S2O2)], 8; anti- [Re(PPh3)2(CO)6(µ,η2:η2-C2S2O2)], 9; anti- [Re(pyr)2(CO)6(µ,η2:η2-C2S2O2)], 10; anti- [Re(G)2(CO)6(µ,η2:η2-C2S2O2)] 11; [{Re2(CO)6(µ,η2:η2-C2S2O2)(µ,η1:η1-pyz)}2], 12 and [{Re2(CO)6(µ,η2:η2-C2S2O2)(µ,η1:η1-bpy)}2], 13 respectively. Isomerization effects of compounds 10 and 13 can be distinguished by 2D NMR spectroscopy.
On the other hand, the reactions of decarbonylated [{Re(CO)5}2(µ,η1:η1-C2O4)] with dppp and [N, N-bis(diphenylphosphinomethyl)amino]pyridine (PNP) give [(η2-dppp)Re(CO)3(µ,η1:η1-C2O4)Re(CO)3(η2-dppp)], 22 and [(η2-PNP)Re(CO)3(µ,η1:η1-C2O4)Re(CO)3(η2-PNP)], 23 respectively. Reaction with dppf gives [Re2(µ-OPPh2(C5H4)Fe(C5H4)PPh2)(CO)6(µ,η2:η2-C2O4)], 24.
The compound [Re2(µ-dppene)(CO)6(µ,η2:η2-C2S4)], 14 is obtained by two different routes, (i) reaction between [Re(thf)3(CO)3]+ and [NEt4]2[C2S4] and (ii) [Re(OH2)3(CO)3]Br and [NEt4]2[C2S4], each followed by reaction of the intermediate formed with dppene. The molecular rectangle [{Re2(CO)6(µ,η2:η2-C2S4)(µ,η1:η1-bpy)}2], 16 can be obtained via reaction between [{Re(CO)5}2(µ,η1:η1-bpy)] and [NEt4]2[C2S4].
The complexes [Re2(µ-PP)(CO)6(µ,η2:η2-C2H2N2S2)] (PP = dppene, 17; mdpab, 18, dppf, 19) are synthesized from the decarbonylation of [Re(CO)5(OTf)] in the presence of H2dtox. Compound 17 consists of two isomers; S-cis-[Re2(µdppene)(CO)6(µ,η2:η2-C2H2N2S2)], 17A and S-trans-[Re2(µdppene)(CO)6(µ,η2:η2-C2H2N2S2)], 17B, which can be differentiated by their δ(NH) IR absorption characteristics, and NMR spectra. The analogous reaction between [Re(CO)52oxa) affords [Re2(µdppene)(CO)6(µ,η2:η2-C2H2N2O2)], 20 and [Re2(µ-dppene)2(CO)6(CF3SO3)2], 21.
A series of cationic complexes [Re2(µ-PP)(CO)6(µ,η2:η2-bpym)][BF4]2 (PP = dppp, 25; 1,4- bis(diphenylphosphino)butane (dppb), 26; 1,5-bis(diphenylphosphino)pentane (dpppe), 27; 1,6- bis(diphenylphosphino)hexane (dpph), 28) have also been synthesized from the reaction of [Re(thf)3(CO)3]+ with bpym. These complexes show two maxima at 323 and 472 nm in the UV-vis spectra, indicating the intraligand (IL) and metal-ligand charge transfer (MLCT). No dirhenium complex can be obtained using dpp as ligand. Compounds [ReBr(CO)3(η2-dpp)], 29 and [ReBr(CO)3(η2-dppp)], 30 are obtained from the reaction between [ReBr3(CO)3]2-, dppp and dpp in a solvent mixture (MeOH : THF=1:1) while [Re(CO)3(FBF3)(η2-dpppe)], 31 and [Re(CO)3(FBF3)(η2-dpp)], 32 are formed from the reaction between[Re(thf)3(CO)3]+, dpppe and dpp.
Complexes 3, 4, 5, 9, 10, 14, 17 and [Re2(µ-dppene)(CO)6(µ,η2:η2-C2O4)] (oxdppene) were tested for their cytotoxicity towards two cancer cell lines. Some of the complexes inhibit the growth of MOLT-4 human leukemia cells but none of them show any activity against MCF-7 breast cancer cells.
Date Issued
2006
Call Number
QD474 Kee
Date Submitted
2006