2,5-Bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl Complexes of the Heavy Alkaline Earth Metals: Synthesis, Structures, and Hydroamination Catalysis

Abstract

The heteroleptic iodo complexes [(DIP2pyr)MI(THF) n ] (M = Ca, Sr (n = 3); Ba (n = 4); (DIP2pyr)− = 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl) were synthesized by reaction of [(DIP2pyr)K] with anhydrous alkaline earth metal diiodides. All complexes are monomeric in the solid state. A κ3-coordination mode of the (DIP2pyr)− ligand was observed for the strontium and the barium compounds, while the analogous calcium derivative is κ2-coordinated in the solid state. However, VT-1H NMR studies of [(DIP2pyr)CaI(THF)3] indicate a symmetrically coordinated (DIP2pyr)− ligand in solution. Computational studies confirm the different coordination modes in solution and in the solid state. The preferred κ2-coordination mode observed in the solid state might be a result of temperature or/and crystal-packing effects. Furthermore, the calcium and strontium amido complexes [(DIP2pyr)M{N(SiMe3)2}(THF)2] (M = Ca, Sr) were prepared by reaction of [(DIP2pyr)MI(THF) n ] (M = Ca, Sr (n = 3)) with [K{N(SiMe3)2}]. Both compounds were investigated for the intramolecular hydroamination of aminoalkenes. Both catalysts showed a good activity, and the best results were obtained for the calcium complex [(DIP2pyr)Ca{N(SiMe3)2}(THF)2].

Highly Fluorinated Tris(indazolyl)borate Silylamido Complexes of the Heavier Alkaline Earth Metals: Synthesis, Characterization, and Efficient Catalytic Intramolecular Hydroamination

“…This reactivity highlights the highly effective catalytic activity of 1, which, although comparable with the [{N N}Ca(X)(thf)] systems (X = N(SiMe 3 ) 2 or CH(SiMe 3 ) 2 ), [13] outperforms that of the homoleptic complexes [Ca{N(Si- [15] as well as that of the heteroleptic bis(imidazolin-2-ylidene-1-yl)borate-, [23] amino-phenolate-, [22] aminotroponiminate-, [16] pyrrolyl-, [18] and b-diketiminate-based [14,15] amido species. Therefore, compound 1 represents one of the most efficient precatalysts reported to date for the cyclohydroamination of S. When large loadings of 400 and 600 equivalents of aminoalkene were used, the conversion peaked at 85 and 57 % after 27 and 18 min, respectively (TON = 340 and 342, TOF app = 12 and 19 min ).…”

“…With the N-bound aminotroponiminate or 2,5-bis-[N-(aryl)iminomethyl]-pyrrolyl Ca and Sr silylamido complexes, the activity of the catalysts decreased with increasing atomic number of the metal. [16][17][18] Asymmetric versions of these reactions have also been reported. [19][20][21] Some of us have recently described new Ca, Sr, and Ba heteroleptic [(LO)Ae{N(SiMe 2 R) 2 }(thf) x ] (R= H, Me) complexes bearing different types of N-and O-based amino-phenolate ligands (LO À ).…”

Beyond Hydrofunctionalisation: A Well‐Defined Calcium Compound Catalysed Mild and Efficient Carbonyl Cyanosilylation

“…[1][2][3][4] Among variouse arth-abundant elements, organocalcium compounds have recently garnered considerable interest due to their high terrestrial abundance,l ow-cost, non-toxicity regardless of concentration, and biocompatibility.Ar ange of catalytic processes such as hydroamination,h ydrophosphination, hydroboration, hydrosilylation, andt he hydrogenation of C=C, C=Oo rC =N bonds involving hydrocarbon soluble calcium compounds has appeared in recent years throught he studies from an umber of research groups of whom Harder, Hill, Roesky,W esterhausen, Sarazin, and Ward are especially prominent. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] A common feature of all aforementioned reactions is that one of the precursors contains an EÀHb ond that undergoes s-bond metathesis with the organocalcium compoundt og enerate the active catalyst. The latter undergoes an insertion reactionw ith the unsaturated C=Xb ond to generate as peciest hat subsequently reactsw ith another molecule of EÀHt of orm the product and regenerate the catalyst( Scheme 1).…”

Synthesis and Characterization of Strontium Bis(N-isopropylanilide) and Comparison with the Lighter Magnesium and Calcium Congeners

“…Reduction of 1,4-diaryl-1,4-diaza-1,3-butadiene with strontium in THF yielded products with the corresponding bidentate 1,2-bis(amido)ethene base acting as a bidentate ligand [34]. In 2,5-bis(Naryliminomethyl)pyrrolyl complexes of strontium this ligand acts as a tridentate base [35].…”