Strontium Chemistry with Silicone Grease

Abstract

Abstract. Reaction of Sr(2-Me 2 N-α-Me 3 Si-benzyl) 2 ·(THF) 2 with one equivalent of DIPP(H)N-BH-N(H)DIPP (NBN-H 2 , DIPP = 2,6-iPr-phenyl) gave the strontium bora-amidinate complex Sr(NBN)·(THF) 4 . Traces of silicone grease, however, can change the course of the reaction completely and gave the product {Sr[(DIPP)NSiMe 2 O]·THF} 4 (1) in a ca. 25 % yield. Complex 1 is a S 4 symmetric cluster with a Sr 4 O 4 core and four chelating amide side arms. From the mother liquor a second product could be isolated: the

Alkaline Earth Metal Template (Cross‐)Coupling Reactions with Hybrid Disila‐Crown Ether Analogues

“…At this point of the reaction, the alkaline earth metal ion acts as a convex template, in which the open‐chained ligand species is brought into a suitable conformation for ring closure, which is the final step of the presented reactions. We want to emphasize, that such a mechanism was also postulated by Harder in a past work …”

“…We want to emphasize, that such am echanism wasalso postulated by Harder in apast work. [31] Further reactions of SrI 2 with the ligands1 ,2-disila [12]crown-4( IV)a nd 1,2-disila-benzo [12]crown-4 (V)w erep erformed. Both ligands are too small for Sr 2+ + and thus, template-assisted ring opening yieldedn ovel species by intermolecular coupling of the respective crown ether.T he reaction of IV with SrI 2 results in the formation of the first disilanyl-bearing [24]crown-8 ether.…”

“…Nonetheless, the coordination chemistry turned out to be very suitable for early Group 1 and 2 metal ions, especially within disila‐ligands, which provide more suitable bite angles than cyclosiloxanes of D n type (D=Me 2 SiO, n =6, 7) . The nature of a cation, which shall be complexed within siloxane moieties, is preferably hard . In the case of the early alkaline earth‐metal ions, even the commercially available cyclosiloxanes are able to dissolve salts characterized by a high lattice energy and stable complexes were obtained .…”

“…[22][23][24][25][26] The nature of ac ation, which shall be complexed within siloxane moieties, is preferably hard. [13,[27][28][29][30][31] In the case of the early alkaline earth-metal ions, even the commerciallya vailablec yclosiloxanes are able to dissolve salts characterized by ah igh lattice energy and stable complexes wereo btained. [32] Soft cations like Rb + + and Cs + + so far relucteds ilyl ether coordination.…”

Tetranuclear Strontium and Barium Siloxide/Amide Clusters in Metal‐Ligand Cooperative Catalysis

“…For example, the bora‐amidinate complex (NBN)Sr · (THF) 4 {NBN = HB[N(DIPP)] 2 , DIPP = 2,6‐diisopropylphenyl} is active in intramolecular alkene hydroamination (Scheme , top). We also found that reaction of NBN‐H 2 with the dibenzylstrontium reagent Sr(DMAT) 2 · (THF) 2 (DMAT = ortho ‐Me 2 N‐α‐Me 3 Si‐benzyl) in a Schlenk tube with well‐greased joints led to the serendipitous formation of the tetranuclear strontium siloxide/amide cluster 1 ‐Sr that could be isolated in the form of colorless crystals in 24 % yield (Scheme , bottom) . Nucleophilic depolymerization of silicone grease and insertion of the Me 2 SiO‐unit plays a key role in the proposed mechanism .…”