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Synthetic and Structural Studies of Permethylscandocene and Permethyltantalocene Derivatives


St. Clair, Martin A. (1989) Synthetic and Structural Studies of Permethylscandocene and Permethyltantalocene Derivatives. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/192V-TK10.


Cp*₂Sc-H reacts with H₂ and CO at -78°C to yield Cp*₂ScOCH₃. A stepwise reduction of CO to an alkoxide is observed when CO reacts with Cp*₂ScC₆H₄CH₃-p to give the η²-acyl Cp*₂Sc(CO)C₆H₄CH₃-p, which then reacts with H₂ to produce Cp*₂ScOCH₂C₆H₄CH₃-p. Cp*₂ScCH₃ and Cp*₂ScH(THF) react with CO to give uncharuncharacterizable products. Cp*₂ScH and Cp*₂ScCH₃ react with Cp₂MCO (M = Mo, W) to give scandoxycarbenes, Cp₂M=C(CH₃)OScCp*₂, while a wide variety of Cp*₂ScX (X = H, CH₃, N(CH₃)₂, CH₂CH₂C₆H₅) reacts with CpM(CO)₂ (M = Co, Rh) to yield similar carbene complexes. An x-ray crystal structure determination of Cp(CO)Co=C(CH₃)-OScCp*₂ revealed a µ²: η¹, η¹ carbonyl interaction between the Co-CO and Sc.

CO₂ inserts cleanly into Sc-phenyl bonds at -78°C to produce a carboxylate complex, Cp*₂Sc(O₂C)C₆H₄CH₃-p. The structure of this compound was determined by x-ray crystallographic techniques.

Excess C₂H₂ reacts with Cp*₂ScR (R = H, alkyl, aryl, alkenyl, alkynyl, amide) at temperatures below -78°C to form the alkynyl species Cp*₂Sc-C≡C-H, which then reacts with the remaining acetylene to form polyacetylene. Cp*₂Sc-C≡C-H further reacts to yield Cp*₂Sc-C≡C-ScCp*₂. This unusual C₂ bridged dimer was characterized by x-ray crystallography.

Attempts were made to model the C-N bond breaking step of hydrodenitrogenation by synthesizing Cp*₂TaH(η²-H₂C=N(C₆H₄X)) and studying its rearrangement to Cp*₂Ta(=N(C₆H₄X))(CH₃). The 1,2 addition/elimination reactions of Cp*₂Ta(η²-H₂C=N(CH₃)H and Cp*₂Ta(=X)H (X=O, S, NH, N(C₆H₅)) were investigated. Cp*₂Ta(=NH)H was found to react with D₂ to give Cp*₂Ta(=ND)H, implying a nonsymmetric amide-dihydride intermediate for the addition/elimination process. Cp*₂Ta(=S)H and H₂O equilibrate with Cp*₂Ta(=O)H and H₂S, which allowed determination of the difference in bond strengths for Ta=O and Ta=S. Ta=O was found to be approximately 41 kcals/mole stronger than Ta=S.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Scandium, tantalum, carbon monoxide activation
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Bercaw, John E.
Thesis Committee:
  • Bercaw, John E. (chair)
  • Gray, Harry B.
  • Schaefer, William P.
  • Grubbs, Robert H.
Defense Date:22 February 1989
Non-Caltech Author Email:mstclair (AT)
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
Shell Companies FoundationUNSPECIFIED
Record Number:CaltechTHESIS:08262013-094527536
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7941
Deposited By: Benjamin Perez
Deposited On:26 Aug 2013 17:22
Last Modified:26 Oct 2021 21:37

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