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Reactions of Oxygen Containing Ligands in the Coordination Sphere of Permethylhafnocene and Permethyltantalocene


Asselt, Allan van (1987) Reactions of Oxygen Containing Ligands in the Coordination Sphere of Permethylhafnocene and Permethyltantalocene. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/PF6E-KV88.


A series of terl-butylperoxide complexes of hafnium, Cp*2Hf(R)(OOCMe3) (Cp* = ((η5-C5Me5); R = Cl, H, CH3, CH2CH3, CH2CH2CH3, CH2CH2CH2CH3, CH2CHMe2, CH=CHCMe3, C6H5, meta-C6H3(CH2)2) and Cp*(η5-C5(CH3)4CH2CH2CH2)Hf(OOCMe3), has been synthesized. One example has been structurally characterized, Cp*2Hf(OOCMe3)CH2CH3 crystallizes in space group P21/c, with a = 19.890(7)Å, b = 8.746(4)Å, c = 17.532(6)Å, β = 124.987(24)°, V = 2498(2)Å3, Z = 4 and RF = 0.054 (2222 reflections, I > 0). Despite the coordinative unsaturation of the hafnium center, the terl-butylperoxide ligand is coordinated in a mono-dentate ligand. The mode of decomposition of these species is highly dependent on the substituent R. For R = H, CH2CH3, CH2CH2CH3, CH2CH2CH2CH3, CH2CHMe2 a clean first order conversion to Cp*2Hf(OCMe3)(OR) is observed (for R CH2CH3, ΔHǂ = 19.6 kcal•mol-1, ΔSǂ = -13 e.u.). These results are discussed in terms of a two step mechanism involving η2-coordination of the terl-butylperoxide ligand. Homolytic O-O bond cleavage is observed upon heating of Cp*2Hf(OOCMe3) R (R = C6H6, meta-C6H3(CH3)2). In the presence of excess 9,10-dihydroanthracene thermolysis of Cp*2Hf(OOCMe3)C6H6 cleanly affords Cp*2Hf(C6H6)OH and HOCMe3 (ΔHǂ = 22.6 kcal•mol-1, ΔSǂ = -9 e.u.). The O-O bond strength in these complexes is thus estimated to be 22 kcal•mol-1.

Cp*2Ta(CH2)H, Cp*2Ta(CHC6H5)H, Cp*2Ta(C6H4)H, Cp*2Ta(CH2=CH2)H and Cp*2Ta(CH2=CHMe)H react, presumably through Cp*2Ta-R intermediates, with H2O to give Cp*2Ta(O)H and alkane. Cp*2Ta(O)H was structurally characterized: space group P21/n, a= 13.073(3)Å, b = 19.337(4)Å, c = 16.002(3)Å, β = 108.66(2)°, V = 3832(1)Å3, Z = 8 and RF = 0.0672 (6730 reflections). Reaction of terlbutylhydroperoxide with these same starting materials ultimately yields Cp*2Ta(O)R and HOCMe3. Cp*2Ta(CH2=CHR)OH species are proposed as intermediates in the olefin hydride reactions. Cp*2Ta(O2)R species can be generated from the reaction of the same starting materials and O2. Lewis acids have been shown to promote oxygen insertion in these complexes.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
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:
  • Collins, Terrence J. (chair)
  • Bercaw, John E.
  • Gray, Harry B.
  • Dougherty, Dennis A.
Defense Date:8 June 1987
Non-Caltech Author Email:vanassea (AT)
Funding AgencyGrant Number
Record Number:CaltechTHESIS:02192014-152435840
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8087
Deposited By: Benjamin Perez
Deposited On:20 Feb 2014 16:44
Last Modified:21 Dec 2019 03:08

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