Quasilinear 3d-metal(i) complexes [KM(N(Dipp)SiR₃)₂] (M = Cr–Co) – structural diversity, solution state behaviour and reactivity

Abstract

The synthesis of quasilinear metal(i) silylamides [KM(N(Dipp)SiR3)2] of chromium to cobalt, their diverse speciation in solid state and solution as well as their reactivity towards alkynes are reported.

On the Synthesis and Reduction of Trigonal Halido Bis(silylamido) Metalates of Chromium to Cobalt

“…Similarly, salt‐like compounds, such as KN(SiMe 3 ) 2 or KCH 2 Ph, form interesting at‐complexes (e. g. [KM(CH 2 Ph){N(SiMe 3 ) 2 } 2 ] or [KFe{N(SiMe 3 ) 2 } 3 ]), which evoke distinct reactivities [18,19] . In addition to hexamethyldisilazanides, metal(II) complexes with bulkier silyamide ligands (e. g. −N(SiMe 2 Ph) or −N(Dipp)SiR 3 ) (Dipp=2,6‐di‐ iso ‐propylphenyl) also found their use with a persistent quasilinear geometry [20–25] . In recent reports it was also shown that such divalent 3d‐metal silylamides can be reduced giving linear, monovalent complex anions [22,25–29] .…”

“…In recent reports it was also shown that such divalent 3d‐metal silylamides can be reduced giving linear, monovalent complex anions [22,25–29] . These were employed in bond activation and substrate reduction [19,24,27,29–34] . Here, the unique role of the low‐coordinate environment of the low‐valent metal as well as the weak field of silylamide ligands became evident, causing unusual higher‐spin imido cobalt complexes or metal bound alkyne radical anions [31,33,34] .…”

High‐Spin Imido Cobalt Complexes with Imidyl Radical Character**

“…[12] Given these comparably long C À N imide bonds found for complexes [2] À and [3] À we were curious if this was connected to the unique anionic character of these imido complexes, [46] as nearly all comparable 3dmetal imido complexes are either neutral or cationic. Thus, the overall neutral cobalt(I) complex K[1] [55] was reacted with Dipp-N 3 and Tripp-N 3 which gave the respective complexes K [2] and K [3]. X-Ray analysis revealed (Figure 2) an intriguing direct potassium interaction, as cation coordination to imide metal units (such as Sc 3+ ) is suggested as an important factor in modulating their properties, although direct structural evidence is lacking.…”

Imido Cobalt Complexes with Imidyl Character

“…Together with a low-spin trisphosphinoborate imido iron(II) complex by Brown et al [46] this is a unique feature compared to all other structurally characterized transition metal imido complexes which are either neutral or cationic. As such we reacted the overall neutral cobalt(I) complex [K(CoL2)] [47] with Dipp-N3 and Tripp-N3 which gave the respective imido complexes K [4] and K [5], whose structures were confirmed via X-Ray analysis (Figure 5). In solid state the potassium cation interacts with the aromatic system of the imido ligand, whose coordination sphere is completed either by two diethyl ether molecules (K [4]), or by interaction with the aryl ring of the -N(Dipp)SiMe3 ligand of a neighbouring complex (K [5]) under formation of a polymeric chain.…”