Ein isolierbarer terminaler Imidkomplex des Palladiums und katalytische Implikationen

Abstract

Wir berichten über die erste Isolierung eines terminalen Palladium(II)‐Imidkomplexes und über dessen Reaktivität. Dieses Fragment ist ein Schlüsselintermediat für zahlreiche katalytische Prozesse einschließlich der C‐H‐Aminierungsreaktion. Wir demonstrieren die Aktivierung von H‐H‐, C‐H‐, N‐H‐ und O‐H‐Bindungen unter milden Bedingungen und beleuchten katalytische Anwendungen. Die hohe Reaktivität ist auf die Population des antibindenden höchsten besetzten Molekülorbitals (HOMO) zurückzuführen. Dies führt zu einer einzigartigen Ladungstrennung innerhalb der geschlossenschaligen Imidfunktionalität. Somit ist der N‐Atom‐Transfer nicht zwangsläufig – wie bisher allgemein angenommen – mit der hohen Valenz des Metalls (PdIII, PdIV) oder dem offenschaligen Charakter eines Nitrens assoziiert.

A Terminal Iridium Oxo Complex with a Triplet Ground State

“…[6,7] Beyond Group 9, Milsteins platinum(IV) pincer oxo complex, aseries of nickel imides by Hillhouse and co-workers,a nd ar ecent palladium(II) imide by Munz and co-workers represent the only well documented examples. [8][9][10] Both second/third row complexes exhibit electronic singlet ground states like the tetrahedral Rh/Ir oxo/imido compounds.…”

“…[17] This interpretation is corroborated by detailed analysis of the electronic structure.D FT (B3LYP(V)-D3/def2TZVP) calculations reproduced the short Ir À Ob ond (1.80 )a nd near-linearity of the N-Ir-O angle (179.08 8)f or the 3 A'' spin state.Incontrast, the lowest singlet state exhibits considerable deviation from linearity (157.08 8), as also found computationally for ar elated, isoelectronic singlet Pt IV pincer oxo complex. [9] Thec omputed triplet ground state of 8 is separated from the singlet by as ignificant adiabatic energy gap of 41 kJ mol À1 . [18] TheS OMOs of 8 exhibit predominant IrÀO p*character,resulting in equal spin density distribution over the iridium and oxygen atoms (Figure 3c).…”

A Terminal Iridium Oxo Complex with a Triplet Ground State

“…[2][3][4] Accordingly,p ersistent or even isolable oxo/imido complexes of these metals are particularly rare and only obtained in low coordination numbers (CN < 5), as predicted by the "oxo wall". [8][9][10] Both second/third row complexes exhibit electronic singlet ground states like the tetrahedral Rh/Ir oxo/imido compounds. [6,7] Beyond Group 9, Milsteins platinum(IV) pincer oxo complex, aseries of nickel imides by Hillhouse and co-workers,a nd ar ecent palladium(II) imide by Munz and co-workers represent the only well documented examples.…”

“…[13] Accordingly,t he IrÀOs tretching frequencyo f8 (n = 743 cm À1 ), which was assigned by comparison with the 18 Olabeled isotopologue,i sc onsiderably lower than that of [Ir V O(Mes) 3 ](n = 802 cm À1 ). [9] Thec omputed triplet ground state of 8 is separated from the singlet by as ignificant adiabatic energy gap of 41 kJ mol À1 . Tw oo ft he 1 HNMR signals are almost invariant with temperature over aw ide range (DT = À75 to + 65 8 8C).…”