1. C-H Functionalization: Shilov Chemistry
Allegra Liberman-Martin, Levi Moore, Drexel Proctor, and Giselle Sullivan
Chem 165: Organometallic Chemistry
Fall 2009

2. Methane Utilization Current methane conversion methods are indirect
Synthesis gas method
Goal: Direct conversion of methane to methanol
Challenging aspect: increasing reactivity of oxidation products
Comparing Bond Dissociation Energies (BDEs):
BDE(C-H, methane) = 104 kcal/mol
BDE(C-H, methanol) = 93 kcal/mol

3. Radical Chain Oxidation of Alkanes vs. Oxenoid Mechanism
RH + O2  R• + HOO•
R• + O2  ROO•
ROO• + RH  ROOH + R•
Dioxygen causes initiation and propagation of chains.
ROOH + Mn  Mn+1 + RO- + •OH
Compounds of transition metals can also participate in the
propagation of radicals. The radical mechanism is a 1e- process.
Oxenoid Mechanism
RH + 2e- + 2H+ + O2  ROH + H2O
Hydroxylation of C-H bond of a hydrocarbon coupled with oxidation of electron donors.
Requires interaction with a metal core, either in a synthesized catalyst or an enzyme.
The oxenoid mechanism is a 2e- process, and does not involve the formation of radicals.
Both major systems currently in use proceed through an oxenoid type mechanism.
Muradov, N. Z.; Shilov, A. E.; Shteinman, A. A., Reac. Kin. and Cat.Lett. 1975, 2,
Shilov, A.E.; Shteinman A.A. Acc. Chem. Res. 1999, 32, 763, 771.

4. Shilov System
First transition metal system for alkane functionalization
Catalytic in Pt(II), but requires stoichiometric Pt(IV)
Because methyl undergoes nucleophilic attack by both water and chloride ions in solution, both CH3OH and CH3Cl are generated
Luinstra, G. A.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 1993, 115,
Lunistra, G. A.; Wang, L.; Stahl, S. S.; Labinger, J. A.; Bercaw, J. E. J. Organomet. Chem. 1995, 504,

5. Shilov System - Rate Determining Step
Two steps in question:
Methane uptake
methane platinum complex precursor for C–H
C-H activation
Rate Determining Step: methane uptake
Associative vs. dissociative pathway
Ligand dependency (see respective rate laws)
uptake of CH4 to the platinum center results in amethane platinum complex that serves as a precursor for C–H activation with a C–H bond coordinated in a g2-conformation
to the metal.
Zhu, H.; Ziegler, T. J. Organomet. Chem , 4486.

6. Shilov System: Methane Uptake
Associative mechanism for methane uptake
Dissociative mechanism for methane uptake
Zhu, H.; Ziegler, T. J. Organomet. Chem , 4486.

7. Catalytica Systems
85% selectivity for methyl bisulfate
50% conversion of methane
81% selectivity for methyl bisulfate
89% conversion of methane
In both cases, an additional step to hydrolyze methyl bisulfate to methanol is necessary.
Periana, R. A.; Taube, D. J.; Evitt, E. R.; Loffler, D. G; Wentreck, P. R.; Voss, G.; Masuda, T. Science 1993, 259,
Periana, R. A.; Taube, D. J.; Gamble, S.; Taube, H.; Satoh, T.; Fuhii, H. Science 1998, 280,

8. Vanadate Catalysis Vanadate/pyrazine-2-carboxylic acid catalysis
Less extreme reaction conditions
Industrial impact for C-H functionalization
Forms methanol, formic and acetic acid
Süss-Fink, G.; Stanislas, S.: Shul'pin, G.B.; Nizova, G.V. Appl. Organomet. Chem. 2000, 14,

9. Gold in the Shilov Reaction System
Au(I) is isoelectronic with Hg(II); Au(III) with Pt(II)
Selenic acid (H2SeO4) used as oxidant, rather than Pt(IV)
Methane converts to methyl bisulfate, which is hydrolyzable to methanol
De Vos, D. E.; Sels, B. F. . Angew. Chem. Int. Ed. 2004, 44,  

10. Construction of MOF
Wanted to construct a heterogeneous catalyst for Shilov reaction
Used Gd and Pt(BPDC)Cl2 in MOF
Catalytic site structure retained
Image (Figure 1, p. 2057) from “Design, synthesis, and characterization of a Pt-Gd metal-organic framework containing potentially catalytically active sites.” Szeto, K. C.; Kongshaug, K. O.; Jakobsen, S.; Tiset, M.; and Lillerud, K. P.  Royal Soc. Chem. 2008,
Szeto, K. C.; Kongshaug, K. O.; Jakobsen, S.; Tiset, M.; and Lillerud, K. P.  Royal Soc. Chem. 2008,

11. Formation of Lactones
Best with typical Shilov Pt(II) catalyst and Pt(IV) oxidant (60%yield)
Second best with Cu(II) oxidant (56%yield with 3 eq.)
Can be monomers for organic synthesis, materials science, polymers, or biological molecules
Lee, J. M., and Chang, S. Tetra. Lett. 2006, 47,