Reduction and Hydrogenation of a Diazene by a (β‐Diketiminato)nickel Hydrazide

Abstract

A (β‐diketiminato)nickel(II) hydrazido(1–) complex [LtBuNi(η2‐N2H3)], {1, LtBu = [HC(CtBuNC6H3{iPr}2)2]–} has been obtained by treatment of [LtBuNiBr] with hydrazine. In a reaction of 1 with two equivalents of the azo compound diisopropyl azodicarboxylic ester (adc–OiPr) the Ni(N2H3) entity acts as both a hydrogenating and a reducing agent: diisopropyl hydrazidodicarboxylate (hdc–OiPr) is formed, and more adc–OiPr is reduced by two electrons. The resulting (adc–OiPr)2– is found as a ligand in the ultimate nickel product complex, the trinuclear nickel(II) compound [LtBuNi(μ‐adc–OiPr)Ni(μ‐adc–OiPr)NiLtBu] (2), in which two LtBuNi+ units are linked by a [NiII(adc–OiPr)2]2– moiety. The hypothesis that LtBuNiI species are acting as intermediates was supported by the independent finding that 2 can also be obtained by reaction of [LtBuNi(OEt2)] with adc–OiPr.

Synthesis, Characterization, and Interconversion of β‐Diketiminato Nickel NxHy Complexes

“…[31] Moreover, a band at 1028 cm -1 found for 1b can be assigned to the NN vibration, which could be verified by comparison to the results of frequency calculations (ν NN = 1025 cm -1 ). [31] Moreover, a band at 1028 cm -1 found for 1b can be assigned to the NN vibration, which could be verified by comparison to the results of frequency calculations (ν NN = 1025 cm -1 ).…”

“…The bond is significantly shorter than the corresponding bond in IV [1.478(19) Å]. [31] Typical N-N distances reported in the literature for end-on or end-on bridging N 2 H 2 ligands are 1.17-1.34 Å [35,[44][45][46][47][48][49][50] and for side-on coordinated ligands 1.41-1.47 Å. [33][34][35][36][37][38][39][40]42,43] Scheme 2.…”

“…[31] The solid-state structure revealed a side-on coordination of the anionic hydrazido ligand to the nickel(II) center. [31] The solid-state structure revealed a side-on coordination of the anionic hydrazido ligand to the nickel(II) center.…”

Late Metal Scaffolds that Activate Both, Dinitrogen and Reduced Dinitrogen Species NxHy

“…[168] Interestingly, the same β-diketiminato nickel scaffold also accommodates a variety of other nitrogenous ligands relevant to NH 3 generation, including side-on bonded N 2 H 2 , N 2 H 3 -, N 2 H 4 , and NH 3 ligands (Scheme 13). [171,172] The reaction of a nickel(II) bromide precursor with an excess of hydrazine resulted in the formation of the mononuclear hydrazido(1-) complex [L tBu Ni(η 2 -N 2 H 3 )] (53) and the concomitant precipitation of hydrazinium bromide (N 2 H 5 Br). [171] The same complex can be obtained when the doubly reduced dinitrogen complex 51 is treated with an excess of hydrazine.…”

“…[171,172] The reaction of a nickel(II) bromide precursor with an excess of hydrazine resulted in the formation of the mononuclear hydrazido(1-) complex [L tBu Ni(η 2 -N 2 H 3 )] (53) and the concomitant precipitation of hydrazinium bromide (N 2 H 5 Br). [171] The same complex can be obtained when the doubly reduced dinitrogen complex 51 is treated with an excess of hydrazine. Reaction of the hydrazido complex 53 with the strong base potassium tert-butoxide in the presence of 18-crown-6 (18-c-6) afforded a nickel(II) complex side-on bound diazene ligand trans- [L tBu Ni(η 2 -N 2 H 2 )K(18-c-6)] (52).…”