Countercation Effect on CO₂ Binding to Oxo Titanate with Bulky Anilide Ligands

Abstract

This work focuses on nucleophilic activation of CO2 at the anionic terminal oxo titanium tris(anilide) complexes [(Solv)nM][OTi(N[tBu]Ar)3]m with M=Li, Na, K, Mg, MgMe, AlCl2, AlI2; Ar=3,5‐Me2C6H3; Solv=Et2O, THF, 12‐crown‐4, 2,2,2‐cryptand; n, m=1–2. The CO2 binding strength to the terminal oxo ligand of [OTi(N[tBu]Ar)3]− ([1]−) and the stability of the resulting carbonate moiety [O2COTi(N[tBu]Ar)3]− ([2]−) are highly dependent on the Lewis acidity of the countercation. We report herein on CO2 binding as a function of countercation and countercation coordination environment, and comment in this respect on the bottom and upper limits of the cation Lewis acidity. Thermodynamic parameters are provided for oxo complexes with lithium as countercation, that is, [(Et2O)2Li][1] and [(12‐c‐4)Li][1].

Bonding in pentalene complexes and their recent applications

“…Structure-bonding representation of CO2 binding in µ-Z fashion to Ti2Pn † 2. R = Si i Pr3 [40,94]. The only other significant contribution to small molecule activation chemistryprovided by organometallic pentalene complexes comes from recent reports of the permethylpentalene group(IV) metal hydrocarbyl complexes, (η 8 -Pn * )TiR2; R = Me, CH2Ph and (η 8 -Pn * )M(η 3 -C3H5)2; M = Zr, Hf and investigations into their reactions with CO2.…”

Selective Transformation of Nickel‐Bound Formate to CO or C−C Coupling Products Triggered by Deprotonation and Steered by Alkali‐Metal Ions

“…Consistently, after removal of all volatiles a ν CO stretching band ([L t Bu Ni I −CO]) was hardly detectable in the ATR‐IR spectrum of the product mixture, confirming that the reaction of I with TMS‐OTf leads to the generation of CO as a gas. Altogether these investigations thus show, that the contact of I with electrophiles leads to the direct formation of CO, which is of interest also considering that the CO 2 2− ligand in I is derived from formate: Liberation of CO from HOOCH is known to occur in reactions with strong acids, however, there are only rather few examples, where formate coordinated to early transition metals (Ti, [12, 20] W [21] ) releases CO upon deprotonation.…”

“…In particular it is unclear, in which step CO is liberated and what the exact role of the iron ion as a Lewis acid (LA) is. At the same time, knowledge on questions like the latter could form the basis for the rational design of artificial systems, which accomplish the LA‐assisted activation of CO 2 [10–14] …”

“…Recently we reported on the complex [L t Bu Ni(OCO‐ κ 2 O , C )]Li 3 [N(SiMe 3 ) 2 ] 2 , I , (see Scheme 1), which we synthesized from the correspondent η 2 ‐formate precursor [L t Bu NiOOCH], II , via deprotonation with Li[N(SiMe 3 ) 2 ] [18] . Reports on successful formate deprotonation are rather rare [12, 19–21] and the synthesis of I has been the first example where it led to a mononuclear metal complex featuring a side‐on bound CO 2 2− moiety; it was further shown that the same entity emerges from the activation of CO 2 at L t Bu Ni 0 units in the initial step [18, 22, 23] . In the present contribution we now present the results of investigations aiming at a comprehensive understanding of the properties and reactivity of the system [L t Bu Ni(OCO‐ κ 2 O , C )]M 3 [N(SiMe 3 ) 2 ] 2 with variation of the Lewis acidic metal ions M + .…”

“…In particular it is unclear, in which step CO is liberated and what the exact role of the iron ion as aLewis acid (LA) is.A tt he same time,knowledge on questions like the latter could form the basis for the rational design of artificial systems,w hich accomplish the LA-assisted activation of CO 2 . [10][11][12][13][14] In chemical laboratories af requent and (especially in comparison with the C II O 2 2À dianion, sometimes referred to as carbonite) quite stable species formed in the reduction of CO 2 is formate.While formate as well as its corresponding acid are important chemicals and in addition have been considered as fuels, [15][16][17] also their further conversion and thus utilization as chemical building blocks for value-added compounds bears great potential. However,t he chemistry of formate in the coordination sphere of molecular metal complexes is underdeveloped.…”