Synthesis of mixed-donor amido/amino/siloxo ligands from symmetrical diamidosilylether ligands via a retro-Brook rearrangement and their chromium(ii) complexes

Abstract

The dilithio salts of two chelating diamidosilylether ligands undergo a retro-Brook rearrangement from oxygen to the amido-nitrogen, thereby directly yielding a new mixed-donor amido/amino/siloxo ligand. When reacted with chromium(II), siloxo-bridged dimers and a very strong eta(2)-(N,C(ipso)) arylamido interaction are featured.

Mixed‐Donor Amido–Siloxo Actinide(IV) Halide and Alkyl Complexes with an Aryl Cipso Interaction

“…Instead, an interaction between the C ipso atom of the N ‐aryl group and the thorium centre is observed. This metal–C ipso interaction was also observed in {[ R NNO]Cr} 2 (R = 2,4,6‐Me 3 Ph, 2,6‐ i Pr 2 Ph), the only reported example in which the [ R NNO] 2– ligand has been coordinated to a transition metal centre 10…”

“…Deuterated solvents were distilled from sodium/benzophenone solutions, and three freeze–pump–thaw cycles were performed before use. UCl 4 ,77 ThCl 4 · 2DME,78,79 [NNO]Li 2 9,10 and [NNO]Li 2 9,10 were prepared in accordance with published literature procedures. Pentane was removed in vacuo from LiCH 2 Si(CH 3 ) 3 (1.0 M , Aldrich) prior to use.…”

“…Brook rearrangements have been well studied, although the use of the rearranged products as potential ligands has been essentially overlooked 12,13. We have demonstrated the potential utility of this series of mixed‐donor [ R NNO] 2– ligands through their addition to chromium(II) to yield a series of chromium‐based complexes with unusual structural features 10…”

“…We recently reported a straightforward and facile method for the preparation of a mixed‐donor amido–amino–siloxo ligand in one step by the 1,3‐silyl retro‐Brook rearrangement of a diamido silyl ether ligand 9,10. The lithiation of the easily prepared [(RNHSiMe 2 ) 2 O] {[ R NON]H 2 ; R = n Pr, 2,4,6‐Me 3 Ph, 2,6‐ i Pr 2 Ph, 3,5‐Me 2 Ph, 3,5‐(CF 3 ) 2 Ph}9,11 in tetrahydrofuran (THF) facilitates the rearrangement of [ R NON]Li 2 to yield the new, dianionic, amido–amino–siloxo ligands [RN(Li)SiMe 2 N(R)SiMe 2 OLi] ([ R NNO]Li 2 ; Scheme ) 9,10. This simple one‐pot synthesis provides access to large quantities of nonsymmetrical ligands.…”

Iron(II) complexes of dimethyltriazacyclophane

“…This ipso interaction is likely necessary to stabilize the highly electrophilic 16-electron Fe center. Such an interaction is often observed in early-transition or f-block metal complexes (Tonks et al, 2012;Gountchev & Tilley, 1999;Mü ller-Buschbaum & Quitmann, 2003;Odom et al, 1998;Vlaisavljevich et al, 2013;Haftbaradaran et al, 2005;Evans et al, 1996;Berthet et al, 2008;Arney et al, 1992). To the best of our knowledge, compound 9 is the first structural report on an Fe II Á Á ÁC ipso interaction (Suess & Peters, 2013).…”