Polyoxoanion-supported catalyst precursors. Synthesis and characterization of the iridium(I) and rhodium(I) precatalysts [(n-C{sub 4}H{sub 9}){sub 4}N]{sub 5}Na{sub 3}[(1,5-COD)M{center_dot}P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}] (M = Ir, Rh)
- Univ. of Oregon, Eugene, OR (United States)
- Bend Research, Inc., OR (United States)
- Colorado State Univ., Fort Collins, CO (United States); and others
The reaction of the triniobium-substituted polyoxometalate [(n-C{sub 4}H{sub 9}){sub 4}N]{sub 9}P{sub 2}W{sub 15}Nb{sub 3}O{sub 62} with an equimolar amount of [Ir(1,5-COD)(CH{sub 3}CN){sub 2}]BF{sub 4} or [Rh(1,5-COD)(CH{sub 3}CN){sub 2}]BF{sub 4} (1,5-COD = 1,5-cyclooctadiene) leads to the formation of the air-sensitive polyoxometalate-supported organometallic complexes [(1,5-COD)Ir{center_dot}Pr{sub 2}W{sub 15}Nb{sub 3}O{sub 62}]{sup 8{minus}}, 1, and [(1,5-COD)Rh{center_dot}P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}]{sup 8{minus}}, 2. These complexes were isolated as their mixed 5[(n-C{sub 4}H{sub 9}){sub 4}N]{sup +}/3Na{sup +} salts and have been characterized by {sup 1}H, {sup 13}C, {sup 31}P, and {sup 183}W NMR spectroscopy as well as IR spectroscopy, sedimentation-equilibrium molecular-weight measurements, and complete elemental analyses. Additional studies of 1 by {sup 17}O NMR demonstrate that the iridium binds in overall average C{sub 3v}(pseudo) symmetry to the {open_quotes}Nb{sub 3}O{sub 9}{sup 3{minus}}{close_quotes} minisurface (pseudo due to the 2-fold axis in 1,5-COD and thus the local C{sub s} symmetry at iridium). For 2, the results of the {sup 17}O NMR studies are definitive in showing that 2 can also be successfully {sup 17}O-enriched in the niobium-oxygen sites. However, the {sup 17}O NMR data subsequently acquired for 2 require the formulation of two or more (possibly rapidly interconverting) support-site isomers in solution. These {sup 17}O NMR results provide direct evidence for the M-ONb{sub 2} bonding between [(1,5-COD)M]{sup +} (M = Ir, Rh) and P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}{sup 9{minus}} in solution, where catalysis beginning with 1 and 2 as a precatalyst has been demonstrated.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 451274
- Journal Information:
- Inorganic Chemistry, Vol. 34, Issue 6; Other Information: PBD: 15 Mar 1995
- Country of Publication:
- United States
- Language:
- English
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