Modeling the Proposed Intermediate in Alkane Carbon−Hydrogen Bond Activation by Cp*(PMe₃)Ir(Me)OTf:  Synthesis and Stability of Novel Organometallic Iridium(V) Complexes

Abstract

Addition of HX to CH2Cl2 solutions of Cp*IrMe4 (Cp* = η5-C5Me5) at low temperature provided Cp*Ir(Me)3X (X = Cl, 5; X = OSO2CF3 = OTf, 6). Both complexes are very thermally sensitive yet proved to be useful precursors for novel cationic iridium(V) complexes. Treatment of 6 with a variety of trisubstituted phosphines, arsines, and stibines (L) afforded compounds 7−12, [Cp*(L)IrMe3][OTf] (L = PMe3, 7; L = PEt3, 8; L = PPh3, 9; L = AsEt3, 10; L = AsPh3, 11; L = SbPh3, 12). Metathesis of the triflate anion of antimony complex 12 for the tetraphenylborate anion afforded [Cp*(SbPh3)IrMe3][BPh4] (13). The molecular structure of 13 was determined by single-crystal X-ray diffraction analysis. Complex 7 is a potential model for the proposed intermediate on the methane carbon−hydrogen bond activation reaction pathway by Cp*(PMe3)Ir(Me)OTf, and its relevance to this reaction is discussed. Complex 7 decomposed by reductive elimination of MeCp*. The remaining iridium fragment was trapped by added phosphine to form [cis-{PMe3}4IrMe2][OTf] (14) as an impure mixture. Reaction of 6 with excess dppm (dppm = Ph2PCH2PPh2) afforded [cis-{η2-Ph2PCH2PPh2}2IrMe2][OTf] (15). The molecular structure of 15 was determined by single-crystal X-ray structure analysis.

Experimental and Computational Studies of Ruthenium(II)-Catalyzed Addition of Arene C−H Bonds to Olefins

“…3,63-66 Recent reports of Ir(III) systems that activate C-H bonds have prompted speculation on the mechanism of the C-H bond-breaking step of late transition metal systems for which oxidative addition would yield an unusually high formal oxidation state. 41,[67][68][69][70][71][72][73] To assist efforts to discern the C-H activation pathway for catalysis using complex 1, DFT calculations have been employed for benzene C-H activation by the {(Tab)Ru II (CO)(Me)} fragment. Oxidative addition to form the Ru(IV) complex {(Tab)-Ru IV (CO)(Me)(H)(Ph)} (followed by reductive elimination of methane) and a non-oxidative addition reaction with simultaneous C-H bond-breaking and bond-forming have been considered (Scheme 10).…”

The neighboring group effect of fluorine in the tritium labeling of organic substrates with [Cp*(PMe3)IrMe(CH2Cl2)]+[BArf]−, a cationic iridium(III) complex

“…The C-H bond activation of organic substrates with highly active Ir(III) complexes, such as [Cp*(PMe 3 )IrMe(CH 2 3 4 , has been extensively studied, [1][2][3][4][5][6][7][8][9][10][11][12] and the application to tritium and deuterium labeling of both simple organic molecules and more complex pharmaceutical templates has been recently demonstrated by our groups. 13,14 We found that 1 exchanges tritium most easily with the protons of aromatic rings.…”

High Oxidation State Organocobalt Complexes: Synthesis and Characterization of Dihydridodisilyl Cobalt(V) Species

“…[11] Higher oxidation states of first-row metals have been discussed as reactive intermediates, but isolated examples are rare. [12] We showed that cationic cobalt(iii) alkyl complexes [(C 5 Me 5 ){P(OMe) 3 .…”