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Silyl-Hydrosilane Exchange at a Magnesium Triphenylsilyl Complex Supported by a Cyclen-Derived NNNN-Type Macrocyclic Ligand

Silyl-Hydrosilane Exchange at a Magnesium Triphenylsilyl Complex Supported by a Cyclen-Derived NNNN-Type Macrocyclic Ligand

Lara E Lemmerz, Valeri Leich, Daniel Martin, Thomas P Spaniol, Jun Okuda

Inorg Chem. 2017 Dec 18;56(24):14979-14990.

PMID: 29192769

Abstract:

The magnesium triphenylsilyl complex [(Me3TACD)Mg(SiPh3)] (2) was synthesized from magnesium bis(triphenylsilyl) [Mg(SiPh3)2(THF)2]·THF (1; THF = tetrahydrofuran) and the NNNN-type macrocyclic amidotriamine proligand (Me3TACD)H ((Me3TACD)H = Me3[12]aneN4 = 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane). Treating 2 with AlR3 (R = Me, Et) gave the magnesium triphenylsilyl complexes with "blocked" amido function [(Me3TACD·AlR3)Mg(SiPh3)] (3a: R = Me; 3b: R = Et). Instead of forming a Mg-H bond upon reaction with dihydrogen or hydrosilanes, 2 and 3a,b underwent rapid silyl-silane exchange with hydrosilanes. Treating the ethyl complex [(Me3TACD·AlEt3)MgEt] with H3SiPh gave [(Me3TACD·AlEt3)MgH] (4), albeit not in a reproducible manner. The silyl-hydrosilane exchange allows access to other magnesium silyls of the type [(Me3TACD)Mg(SiR'3)] (5a: SiR'3 = SiH2Ph; 5b: SiR'3 = SiHPh2) and [(Me3TACD·AlR3)Mg(SiR'3)] (6a: SiR'3 = SiH2Ph, R = Me; 6b: SiR'3 = SiH2Ph, R = Et; 7a: SiR'3 = SiHPh2, R = Me; 7b: SiR'3 = SiHPh2, R = Et). The reaction of 2 with H2SiMePh in THF at room temperature resulted in an equilibrium (Keq ≈ 1). Protonolysis of 2 with Brønsted acids (HX) 2,5-di-tert-butylphenol, phenylacetylene, acetophenone, aniline, and triethylammonium chloride each gave a compound [(Me3TACD)Mg(X)] with the conjugated base coordinated at the magnesium along with HSiPh3. The magnesium silyls 1, 2, and 7b as well as the magnesium hydride 4 contain a distorted square-pyramidal magnesium center according to single-crystal X-ray diffraction.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
LS777114	(12-Dodecylphosphonic acid)triethylammonium chloride			Price

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