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Synthesis and characterization of thioaldehyde hydride derivatives of permethyltantalocene. Investigations of their equilibration with thiolates and the stereochemistry of alkyl migrations from sulfur to tantalum

Nelson, Janet E. and Parkin, Gerard and Bercaw, John E. (1992) Synthesis and characterization of thioaldehyde hydride derivatives of permethyltantalocene. Investigations of their equilibration with thiolates and the stereochemistry of alkyl migrations from sulfur to tantalum. Organometallics, 11 (6). pp. 2181-2189. ISSN 0276-7333. doi:10.1021/om00042a036. https://resolver.caltech.edu/CaltechAUTHORS:20180521-111433261

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Abstract

Permethyltantalocene thioaldehyde hydride complexes, Cp*_2Ta(η^2-S-CHR)H (Cp* = η^5-C_5Me_5; R = H, C_6H_5, CH_2C_6H_5, CH_2CMe_3), have been prepared by treating precursors to [Cp*_2Ta-R'] (e.g. Cp*_2Ta(=C=CH_2)H for R' = CH=CH_22) with the appropriate thiol RCH_2SH. Oxidative addition of the S-H bond leads to the unstable Ta(V) derivatives Cp*_2Ta(R'(H)(SCH_2R). Reductive elimination of R'H is facile, forming [Cp*_2Ta-ScH_2R], which subsequently undergoes β-He limination to yield the thiddehyde hydrides Cp*_2Ta( η^2-S-CHR)H. The results of an X-ray structure determination for Cp*_2Ta( η_2-SC-HCH_2C_6H_5)H are summarized. These permethyltantalocene thioaldehyde hydride complexes are shown to be in rapid equilibrium with the corresponding 16-electron thiolate species [CP*_2Ta-SCH_3R] through a β-H migratory inaertion/elimination process. When they are heated, the permethyltantalocene thiddehyde hydride complexes undergo rearrangement to the thermodynamically favored tautomer, the permethyltantalocene sulfido alkyl Cp*_2Ta(=S)CH_2R. An inverse kinetic deuterium isotope effect observed for Cp*_2Ta(η^2-S-CY_2)Y (Y = H, D) ((k_H)/(k_D) = 0.72 (3) at 138 °C) is indicative of a stepwise process involving to Cp*_2Ta(=S)CY_3. Derivatives of the permethyltantalocene phenylthioacetaldehyde hydride have been prepared from the erythro- and threo-phenethyl-d_2 mercaptan, C_6H_5CHDCHDSH, to elucidate the mechanism of alkyl transfer. The migration has been found to proceed with ≳ 85% retention of stereochemistry at carbon for the migrating phenethyl-d_2 group. The sulfido methyl complex Cp*_2Ta(=S)CH_3 is hydrogenated under forcing conditions to yield methane and CP*~T~(=S)bHu,t this product resists final hydrogenation to Cp*_2TaH_3 and H_2S.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://dx.doi.org/10.1021/om00042a036DOIArticle
Additional Information:© 1992 American Chemical Society. Received September 20, 1991. This work was supported by the National Science Foundation (Grant No. CHE-8901593) and Shell Companies Foundation. We thank Dr. Jay Labinger for helpful discussions, Dr. Andrew Meyers for advice on preparing the labeled thiols, and Roger Quan for carrying out some relevant experiments.
Funders:
Funding AgencyGrant Number
NSFCHE-8901593
Shell Companies FoundationUNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Division of Chemistry and Chemical Engineering8511
Issue or Number:6
DOI:10.1021/om00042a036
Record Number:CaltechAUTHORS:20180521-111433261
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180521-111433261
Official Citation:Synthesis and characterization of thioaldehyde hydride derivatives of permethyltantalocene. Investigations of their equilibration with thiolates and the stereochemistry of alkyl migrations from sulfur to tantalum Janet E. Nelson, Gerard Parkin, and John E. Bercaw Organometallics 1992 11 (6), 2181-2189 DOI: 10.1021/om00042a036
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86500
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:21 May 2018 19:45
Last Modified:15 Nov 2021 20:39

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