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Synthetic and structural studies of permethylscandocene and permethyltantalocene derivatives

Citation

St. Clair, Martin A. (1989) Synthetic and structural studies of permethylscandocene and permethyltantalocene derivatives. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:08262013-094527536

Abstract

Cp*_2Sc-H reacts with H_2 and CO at -78°C to yield Cp*_2ScOCH_3. A stepwise reduction of CO to an alkoxide is observed when CO reacts with Cp*_2ScC_6H_4CH_3-p to give the η^2-acyl Cp*_2Sc(CO)C_6H_4CH_3-p, which then reacts with H_2 to produce Cp*_2ScOCH_2C_6H_4CH_3-p. Cp*_2ScCH_3 and Cp*_2ScH(THF) react with CO to give unchar- uncharacterizable products. Cp*_2ScH and Cp*_2ScCH_3 react with Cp_2MCO (M = Mo, W) to give scandoxycarbenes, Cp_2M=C(CH_3)OScCp*_2, while a wide variety of Cp*_2ScX (X = H, CH_3, N(CH_3)_2, CH_2CH_2C_6H_5) reacts with CpM(CO)_2 (M = Co, Rh) to yield similar carbene complexes. An x-ray crystal structure determination of Cp(CO)Co=C(CH_3)- OScCp*_2 revealed a µ^2: η^1, η^1 carbonyl interaction between the Co-CO and Sc.

CO_2 inserts cleanly into Sc-phenyl bonds at -78°C to produce a carboxylate complex, Cp*_2Sc(O_2C)C_6H_4CH_3-p. The structure of this compound was determined by x-ray crystallographic techniques.

Excess C_2H_2 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 C_2 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(η^2-H_2C=N(C_6H_4X)) and studying its rearrangement to Cp*_2Ta(=N(C_6H_4X))(CH_3). The 1,2 addition/elimination reactions of Cp*_2Ta(η^2- H_2C=N(CH_3)H and Cp*_2Ta(=X)H (X=O, S, NH, N(C_6H_5)) were investigated. Cp*_2Ta(=NH)H was found to react with D_2 to give Cp*_2Ta(=ND)H, implying a nonsymmetric amide-dihydride intermediate for the addition/elimination process. Cp*_2Ta(=S)H and H_2O equilibrate with Cp*_2Ta(=O)H and H_2S, 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
Defense Date:22 February 1989
Non-Caltech Author Email:mstclair (AT) coe.edu
Record Number:CaltechTHESIS:08262013-094527536
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:08262013-094527536
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7941
Collection:CaltechTHESIS
Deposited By: Benjamin Perez
Deposited On:26 Aug 2013 17:22
Last Modified:27 Aug 2014 18:42

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