The Development of Ru(II) and Fe(II) Complexes for C-H and H2 Bond Activation

TAYLOR, KATHLEEN H. The Development of Ru(II) and Fe(II) Complexes for C–H and H2 Bond Activation. (Under the direction of Professor T. Brent Gunnoe).

Hydrocarbons serve as the feedstocks for numerous commodity chemicals. Industrial methods to functionalize hydrocarbons in order to convert them into higher value chemicals often involve cost and energy intensive processes. Furthermore, these processes often do not provide high selectivity for the desired products. Thus, the development of a catalytic method to functionalize hydrocarbons with high selectivity and under mild reaction conditions is highly attractive. C–H bond activation, the breaking of a substrate’s C–H bond, is a vital step in hydrocarbon functionalization. The work described in this thesis involves the development and study of octahedral Ru(II) complexes for C–H and H2 bond activation and octahedral Fe(II) complexes for C–H activation and furyl ring-opening.
The Ru(II) complexes of the type {[HC(pz5)3]Ru[P(OCH2)3CEt](py)(NHAr)}[BAr′4] (HC(pz5)3 = tris(5-methyl)pyrazolylmethane, P(OCH2)3CEt = 2,6,7-trioxa-1-phosphabicyclo[2,2,1]octane, py = pyridine, Ar = 4-isopropylphenyl, 4-methylphenyl, phenyl, 4-chlorophenyl, 4-fluorophenyl, BAr′4 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) have been demonstrated to activate H2. Complexes with less basic anilido ligands tend to have faster reaction rates with H2.
The Fe(II) complex Cp*Fe[P(OCH2)3CEt]2Ph (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) is capable of C–H activation of furan and 2-methylfuran via a non-radical mechanism under photolytic conditions to produce Cp*Fe[P(OCH2)3CEt]2(2-furyl) and Cp*Fe[P(OCH2)3CEt]2[2-(5-methylfuryl)]. Under photolytic conditions, both Cp*Fe[P(OCH2)3CEt]2(2-furyl) and Cp*Fe[P(OCH2)3CEt]2[2-(5-methylfuryl)] react with 2-butyne to form the ring-opened complexes Cp*Fe[η5-C5Me4(CH=CHCHO)] and Cp*Fe[η5-C5Me4(CH=CHCOCH3)], respectively. Cp*Fe[P(OCH2)3CEt]2(2-furyl) has been shown to react with several other internal alkynes to form the corresponding furyl ring-opened sandwich complexes.