An Organometalllic Ni^IV Complex That Participates in Competing Transmetalation and C(sp²)–O Bond-Forming Reductive Elimination Reactions

Abstract

This communication describes the synthesis of an organometallic NiIV complex bearing a labile trifluoroacetate (OTFA) ligand via the oxidation of a NiII precursor with PhI­(OTFA)2. Intramolecular C­(sp2)–O bond-forming reductive elimination from this NiIV complex is relatively slow, requiring 6 h at 70 °C to reach completion. In contrast, transmetalation with TMSCF3 occurs within just 1 h at room temperature to generate a NiIV–CF3 complex. These studies show that intermolecular reactions such as transmetalation can be competitive with intramolecular reductive elimination processes at NiIV centers.

Impact of Oxidation State on Reactivity and Selectivity Differences between Nickel(III) and Nickel(IV) Alkyl Complexes

“…[5a,c] Furthermore,i nner-sphere C-(sp 2 ) À OAcc oupling is not competitive in this system, likely because of the low lability of the MeCN ligand, which precludes acetate coordination to the Ni IV center. An innersphere mechanism has been proposed for the vast majority of carbon-carbon and C(sp 2 )-heteroatom coupling reactions at Pt IV , [19] Pd IV , [4] Pd III , [20] Ni IV , [21] and Ni III centers. [3,22] In contrast, the Ni III analogue 1-Ni III+ reacts to selectively form the C À C coupled product 3 in either the presence or absence of the acetate nucleophile.T hese results demonstrate that the oxidation state of high-valent Ni can play ak ey role in dictating both the mechanism and selectivity of the favored reductive elimination process in these systems.W hile this study focuses on model complexes,o ngoing investigations in our lab are probing the generality of obtaining complementary bond-forming reactions by manipulating the oxidation state of high-valent Ni intermediates.I ft hese observations prove general, they are likely to find broader applications in catalysis.…”

Aerobic C–C and C–O bond formation reactions mediated by high-valent nickel species

“…[10][11][12][13][14][15][16][17][18][19][20] By comparison, stoichiometric and catalytic Ni-mediated C-heteroatom bond formation reactions have been developed mostly in the past two decades. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] In the past several years we have employed tetradentate pyridinophane ligands to stabilize uncommon organometallic Pd III/IV and Ni III/IV complexes, [37][38][39][40][41][42][43][44] which can undergo C-C and C-heteroatom bond formation reactions. In addition, we have recently reported the use of the ligand 1,4,7-trimethyl-1,4,7triazacyclonane (Me 3 tacn) to stabilize high-valent Ni III/IV complexes that undergo C-C and C-heteroatom bond formation reactions.…”

Nickelaelektro‐katalysierte C‐H‐Alkoxylierung mit sekundären Alkoholen: oxidationsinduzierte reduktive Eliminierung an Nickel(III)

“…Letztlich wird das hochvalente Intermediat Ni IV -I vom Alkohol 2 koordiniert, einhergehend mit einer nachfolgenden Deprotonierung und reduktiven Eliminierung,wobei das alkoxylierte Produkt 3 freigesetzt wird (Abbildung S21). [27] Die 6-Methylchinolin-Gruppe konnte leicht entfernt werden, wodurch ein effizienter Zugang zu Benzamiden 4, Benzoesäuren 5 oder aromatischen Aldehyden 6 ermçglicht wird (Schemata S15-S17).…”