Photochemically Induced Reductive Elimination as a Route to a Zirconocene Complex with a Strongly Activated N₂ Ligand

Abstract

The zirconocene dinitrogen complex [{(η(5)-C5Me4H)2Zr}2(μ2,η(2),η(2)-N2)] was synthesized by photochemical reductive elimination from the corresponding zirconium bis(aryl) or aryl hydride complexes, providing a high-yielding, alkali metal-free route to strongly activated early-metal N2 complexes. Mechanistic studies support the intermediacy of zirconocene arene complexes that in the absence of sufficient dinitrogen promote C-H activation or undergo comproportion to formally Zr(III) complexes. When N2 is in excess arene displacement gives rise to strong dinitrogen activation.

Coordination of N2 ligands to lanthanum: the complexes La (N2)1–8

“…An important step in this research was the discovery of the first ruthenium dinitrogen complexes in the 1960s and since then strenuous efforts were made on the synthesis of transition metal dinitrogen complexes [1,2]. Particular attention was paid on coordinatively unsaturated complexes involved in the catalytic reduction of N 2 [3][4][5][6][7].…”

η6‐Arene‐Zirconium‐PNP‐Pincer Complexes: Mechanism of Their Hydrogenolytic Formation and Their Reactivity as Zirconium(II) Synthons

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In particular,Z r II and Hf II species have been found to display spectacular reactivity in the cleavage of dinitrogen,a nd in the further functionali-zationo ft he activated species. Landmark discoveries in this field have been reported by Fryzuk, [20][21][22][23][24][25][26][27][28] Chirik, [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] and coworkers.…”

“…[5,[65][66][67][68][69][70][71][72][73][74][75] For Zr, the latterr oute has been shown to access the reactive [(Cp) 2 Zr II ]s peciese ither by in situ reaction of [(Cp) 2 ZrCl 2 ]w ith alkyl lithiumr eagents or through ligand-induced reductive elimination from hydridoalkyl precursors. [30,32,34,53,57,58] On the other hand, in the absence of Cp ligands, Zr II and Hf II species have been almost exclusively obtained upon treatment of their halide precursorsw ith highly reactive reducing agents, imposing practical limitations on the developmento fthec hemistry of such species. [20,64] Therefore, the development of suitable synthons for divalent complexes of the heavierG roup 4 metals,a llowing for the formation of an M II speciesi ns itu and withoutthe use of an additional reducing agent, is of considerable interestf or this underdevelopeda rea of transition-metal chemistry.P otential candidates for such synthons would be parene speciesi nw hicht he arene ligand may coordinate as either a"conventional" M II -p-ligand or as an arenediido species, giving rise to metalla(IV)-norbornadiene-type structures.…”

Structure and bonding of lanthanide dinitrogen complexes, Ln(N2)1‐8

“…Similar to Ln(N 2 ) 6 , the octa-coordinated La, Ho, and Lu complexes are highly symmetric. They adopt a D 4h structure except for high-spin La(N 2 ) 8 and Lu(N 2 ) 8 . The former species is twisted to D 4d , [29] while for 4 Lu(N 2 ) 8 , no minimum structure was found on the PES.…”

“…[2,3] For the catalytic reduction of N 2 , the coordinative unsaturated metal dinitrogen complexes are of the highest importance, which explains the ongoing considerable interest in them. [4][5][6][7][8][9] These complexes have generally low stability; therefore, they can be synthesized, isolated, and studied only under extreme conditions. A very efficient tool in this research proved to be the matrix isolation technique coupled mostly with vibrational spectroscopy.…”