Diphosphine ligand activation studies with organotransition-metal compounds

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Thermolysis of CoRu(CO)7(m -PPh2) (1) in refluxing 1,2-dichloroethane in the presence of the diphosphine ligands 2,3-bis(diphenylphosphino)maleic anhydride (bma) and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) furnishes the new mixed-metal complexes CoRu(CO)4(μ -P-P)(μ -PPh2) [where P-P = bma (3); bpcd (6)], along with trace amounts of the known complex CoRu(CO)6(PPh3)(μ -PPh2) (4). The requisite pentacarbonyl intermediates CoRu(CO)5(μ -P-P)(μ -PPh2) [where P-P = bma (2); bpcd (5)] have been prepared by separate routes and studied for their conversion to CoRu(CO)4(μ -P-P)(μ -PPh2). The complexes 2/3 and 5/6 have been isolated and fully characterized in solution by IR and NMR spectroscopy. The kinetics for the conversion of 2→3 and of 5→6 were measured by IR spectroscopy in chlorobenzene solvent. On the basis of the first-order rate constants, CO inhibition, and the activation parameters, a mechanism involving dissociative CO loss as the rate-limiting step is proposed. The solid-state structure of CoRu(CO)4(μ -bma)(μ -PPh2) (3) reveals that the two PPh2 groups are bound to the ruthenium center while the maleic anhydride π bond is coordinated to the cobalt atom. Thermolysis of the cluster Ru3(CO)12 with the bis(phosphine)hydrazine ligand (MeO)2PN(Me)N(Me)P(OMe)2 (dmpdmh) in toluene at 75°C furnishes the known clusters Ru4(CO)12[μ -N(Me)N(Me)] (9) and Ru3(CO)11[P(OMe)3] (10), in addition to the new cluster Ru3(CO)10(dmpdmh) (8) and the phosphite-tethered cluster Ru3(CO)9[μ -P(OMe)3] (11). The simple substitution product Ru3(CO)10(dmpdmh), a logical intermediate to clusters 9-11, was synthesized by treating Ru3(CO)12 and dmpdmh with Me3NO in CH2Cl2 at room temperature, and independent thermolysis reactions using cluster 8 were shown to yield clusters 9-11. The tetrahedrane cluster FeCo2(CO)9(μ3-S) reacts with the redox-active ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) to give the disubstituted cluster FeCo2(CO)7(bpcd)(μ3-S) as the sole product. This diphosphine-substituted cluster contains a cobalt-bound, chelating bpcd ligand. The solid-state structure has been unequivocally established by X-ray diffraction analysis. Cyclic voltammetric studies on FeCo2(CO)7(bpcd)(μ3-S) reveal the presence of two quasireversible redox responses assigned to the 0/1- and 1-/2- redox couples. The orbital composition of these redox couples has been examined by carrying out extended Hückel MO calculations on the model complex FeCo2(CO)7(H4-bpcd)(μ3-S), with the results being compared to related cluster compounds.

Creator(s): Wang, Jiancheng
Creation Date: December 2000
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UNT Libraries
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UNT Theses and Dissertations
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Publisher Name: University of North Texas
Place of Publication: Denton, Texas
Date(s):
  • Creation: December 2000
  • Digitized: August 2, 2007
Description:

Thermolysis of CoRu(CO)7(m -PPh2) (1) in refluxing 1,2-dichloroethane in the presence of the diphosphine ligands 2,3-bis(diphenylphosphino)maleic anhydride (bma) and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) furnishes the new mixed-metal complexes CoRu(CO)4(μ -P-P)(μ -PPh2) [where P-P = bma (3); bpcd (6)], along with trace amounts of the known complex CoRu(CO)6(PPh3)(μ -PPh2) (4). The requisite pentacarbonyl intermediates CoRu(CO)5(μ -P-P)(μ -PPh2) [where P-P = bma (2); bpcd (5)] have been prepared by separate routes and studied for their conversion to CoRu(CO)4(μ -P-P)(μ -PPh2). The complexes 2/3 and 5/6 have been isolated and fully characterized in solution by IR and NMR spectroscopy. The kinetics for the conversion of 2→3 and of 5→6 were measured by IR spectroscopy in chlorobenzene solvent. On the basis of the first-order rate constants, CO inhibition, and the activation parameters, a mechanism involving dissociative CO loss as the rate-limiting step is proposed. The solid-state structure of CoRu(CO)4(μ -bma)(μ -PPh2) (3) reveals that the two PPh2 groups are bound to the ruthenium center while the maleic anhydride π bond is coordinated to the cobalt atom. Thermolysis of the cluster Ru3(CO)12 with the bis(phosphine)hydrazine ligand (MeO)2PN(Me)N(Me)P(OMe)2 (dmpdmh) in toluene at 75°C furnishes the known clusters Ru4(CO)12[μ -N(Me)N(Me)] (9) and Ru3(CO)11[P(OMe)3] (10), in addition to the new cluster Ru3(CO)10(dmpdmh) (8) and the phosphite-tethered cluster Ru3(CO)9[μ -P(OMe)3] (11). The simple substitution product Ru3(CO)10(dmpdmh), a logical intermediate to clusters 9-11, was synthesized by treating Ru3(CO)12 and dmpdmh with Me3NO in CH2Cl2 at room temperature, and independent thermolysis reactions using cluster 8 were shown to yield clusters 9-11. The tetrahedrane cluster FeCo2(CO)9(μ3-S) reacts with the redox-active ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) to give the disubstituted cluster FeCo2(CO)7(bpcd)(μ3-S) as the sole product. This diphosphine-substituted cluster contains a cobalt-bound, chelating bpcd ligand. The solid-state structure has been unequivocally established by X-ray diffraction analysis. Cyclic voltammetric studies on FeCo2(CO)7(bpcd)(μ3-S) reveal the presence of two quasireversible redox responses assigned to the 0/1- and 1-/2- redox couples. The orbital composition of these redox couples has been examined by carrying out extended Hückel MO calculations on the model complex FeCo2(CO)7(H4-bpcd)(μ3-S), with the results being compared to related cluster compounds.

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Level: Doctoral
Discipline: Chemistry
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Keyword(s): thermolysis | diphosphine ligands | new mixed-metalcomplexes
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UNT Libraries
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UNT Theses and Dissertations
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  • OCLC: 47785437 |
  • ARK: ark:/67531/metadc2665
Resource Type: Thesis or Dissertation
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Access: Use restricted to UNT Community
License: Copyright
Holder: Wang, Jiancheng
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