Siloxide Complexes of Chromium(II), Manganese(II), Cobalt(II), and Chromium(III) Incorporating Potassium(I)

Abstract

Heteroleptic ate complexes of the type K[M{N(SiMe3)2}2{OSi(OtBu)3}] (M = Cr, Mn, Co) were synthesized by adding one equivalent of the potassium salt KOSi(OtBu)3 to the bis(trimethylsilyl)amide precursors [Cr{N(SiMe3)2}2(thf)2], [Mn{N(SiMe3)2}2(thf)] and [Co{N(SiMe3)2}2(thf)], respectively. Surprisingly, the reaction of CrCl3(thf)3 with only two equivalents of KOSi(OtBu)3 yielded the homoleptic ate complex K[Cr{OSi(OtBu)3}4]. The compounds were characterized by elemental analysis and DRIFT spectroscopy as well as X-ray crystallography.

Deciphering the Phillips Catalyst by Orbital Analysis and Supervised Machine Learning from Cr Pre-edge XANES of Molecular Libraries

“…In addition to the square-pyramidal [Cr­(OSi­(O t Bu) 3 ) 3 ] complex [ III.1 ], the trigonal-bipyramidal [Cr­(OSi­(O t Bu) 3 ) 3 THF 2 ] complex [ III.2 ] was synthesized to investigate changes in the pre-edge as a function of the local environment. A more tetrahedral-like environment for the Cr­(III) formal oxidation state [(K + K-222)­(Cr – (OSi­(O t Bu) 3 ) 4 )] [ III.3 ] was obtained by reacting [K + (Cr – (OSi­(O t Bu) 3 ) 4 )] in the presence of Kryptofix-2,2,2 (K-222). The octahedrally coordinated [Cr­(OCHMeCH 2 OMe) 3 ] complex [ III.4 ] was chosen as a representative molecule with O h symmetry.…”

“…We broadened the substrate scope for Cr­(III) complexes by including the square-pyramidal [Cr­(OSi­(O t Bu) 3 ) 3 DME] complex [ III.6 ] and the pseudo-octahedral polyhederal-oligosilsesquioxane [(cC 5 H 9 ) 7 Si 7 O 9 (O) 3 Cr­(THF) 3 ] complex [ III.7 ]. We completed the Cr­(III) series by the analysis of the already known [Na­(Cr­(OSi­(OSi­(O t Bu) 3 ) 4 )] [ III.8 ], [Cr­(acac) 3 ] [ III.9 ], and the dimeric [ o -(Cr­(OSiO t Bu 3 ) 2 ) 2 ] [ III.10 ] complexes. We included [Cr 2 O 3 ], a classical reference compound, into the Cr­(III) series to benchmark with previous studies.…”

Yttrium Siloxide Complexes Bearing Terminal Methyl Ligands: Molecular Models for Ln−CH3 Terminated Silica Surfaces

“…All deuterated solvents were dried over NaK for a minimum of 48 h, and filtered through a filter pipette (Whatman) before use. [Y(AlMe 4 ) 3 ] ( 1 a ), [Y(GaMe 4 ) 3 ] ( 1 b ), [La(AlMe 4 ) 3 ], [K{OSi(O t Bu) 3 }] and [Y{OSi(O t Bu) 3 } 3 ] 2 were synthesized according to literature procedures. It has to be mentioned that the 1 H NMR spectrum of [Y{OSi(O t Bu) 3 } 3 ] 2 , contrary to the literature, showed only two signals at 1.59 and 1.75 ppm in the ratio of 2:1 (400.1 MHz, 26 °C, [D 6 ]benzene) and not three, which is also in accord with the data reported in reference .…”

Chromous siloxides of variable nuclearity and magnetism

“…7–9,13,19 On the other hand, low-valent chromium siloxide complexes have been successfully employed in redox-transformations giving access to high-valent chromium imide complexes 6 or promoting dioxygen activation. 20 Our interest in chromium siloxide complexes was sparked by their potential role as mimics/models of silica-grafted chromium surface species 21 as well as the feasibility of halogenido/siloxy exchange in otherwise difficult to handle chromium reagents ( e.g. , Takai olefination reagent).…”