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Weakly interacting solvation spheres surrounding a calixarene-protected tetrairidium carbonyl cluster: contrasting effects on reactivity of alkane solvent and silica support

Palermo, Andrew P. and Zhang, Shengjie and Hwang, Son-Jong and Dixon, David A. and Gates, Bruce C. and Katz, Alexander (2018) Weakly interacting solvation spheres surrounding a calixarene-protected tetrairidium carbonyl cluster: contrasting effects on reactivity of alkane solvent and silica support. Dalton Transactions, 47 (38). pp. 13550-13558. ISSN 1477-9226.

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The tetrairidium carbonyl cluster Ir_4L_3(CO)_9 (L = tert-butyl-calix[4]arene(OPr)_3(OCH_2PPh_2) (Ph = phenyl; Pr = propyl)) on a partially dehydroxylated silica support undergoes hydrogen activation at a rate and with a mechanism different from those pertaining to the cluster in alkane solution. These results are unobvious in view of the sterically bulky ligands protecting the cluster and the nearly identical CO band frequencies in the infrared spectra characterizing the supported and dissolved Ir_4L_3(CO)_9, both before reaction and during reaction involving decarbonylation in the presence of either helium or H_2 (and H2 reacted with the clusters to form hydrides with the same Ir–H band frequencies for clusters in alkane solvent and supported on silica). The initial rates of CO loss from the supported clusters in the presence of helium were the same as those in the presence of H_2. The comparison demonstrates that the rate-determining step for hydride formation on the silica-supported cluster is CO dissociation. In contrast, the comparable dissociation of CO from the cluster in n-decane solution requires a higher temperature, 343 K, and is at least an order of magnitude slower than when the clusters were supported on silica. CO dissociation is not the rate-determining step for hydrogen activation on the cluster in n-decane, as the rate is influenced by reactant H_2 as well.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Palermo, Andrew P.0000-0002-3297-6820
Hwang, Son-Jong0000-0002-3210-466X
Dixon, David A.0000-0002-9492-0056
Gates, Bruce C.0000-0003-0274-4882
Katz, Alexander0000-0003-3487-7049
Additional Information:© 2018 The Royal Society of Chemistry. The article was received on 09 Apr 2018, accepted on 23 Aug 2018 and first published on 24 Aug 2018. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Awards DE-FG02-04ER15513 (AP, BCG) and DE-FG02-05ER15696 (AK). The NMR facility at the California Institute of Technology was supported by the National Science Foundation (NSF) under Grant Number 9724240 and partially supported by the MRSEC Program of the NSF under Award Number DMR-520565. This work was also supported in part by the DOE Office of Science, BES, under the DOE BES Catalysis Center Program by a subcontract from Pacific Northwest National Laboratory (KC0301050-47319). DAD also thanks the Robert Ramsay Chair Fund of The University of Alabama for support. There are no conflicts to declare.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-04ER15513
Department of Energy (DOE)DE-FG02-05ER15696
Pacific Northwest National LaboratoryKC0301050-47319
University of AlabamaUNSPECIFIED
Issue or Number:38
Record Number:CaltechAUTHORS:20180912-082303681
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89553
Deposited By: Tony Diaz
Deposited On:12 Sep 2018 16:56
Last Modified:03 Oct 2019 20:17

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