From mixed group 13 cations [M(AlCp*)₃]⁺ (M = Ga/In/Tl) to an Al₄⁺ cluster

Abstract

AlCp*-complexes with transition metals have shown to be highly reactive and enable C–H or Si–H bond activation. Yet, complexes of AlCp* with low-valent main-group metals are scarce. Here, we report...

Low‐Valent MxAl3Cluster Salts with Tetrahedral [SiAl3]+and Trigonal‐Bipyramidal [M2Al3]2+Cores (M=Si/Ge)

“…For compounds 3 A / 3 B , bands assigned to the stretching vibrations of the Si−Al bonds in the SiAl 3 ‐cluster, the tetrahedral breathing modes, were detected at 454 cm −1 and 463/461 cm −1 (see Supporting Information, Figure S29). These values compare well to M−Al stretching vibrations reported for the cationic complexes of type [M(AlCp*) 3 ] + (M=Al, [25] Ga‐Tl [31] ) but are higher compared to the Raman band of [(AlCp*) 4 ] ( =378 cm −1 ). This indicates a higher strength of the M−Al bonds in the intermetallic compounds compared to the Al−Al bonds in tetrameric [(AlCp*) 4 ].…”

“…This observation points to a fluxional behaviour of the η 1 ‐coordinated Cp* ligand at silicon, but suggests that any exchange of Cp* ligands between silicon and the aluminium centres is slow on the NMR time scale. [30] The 27 Al NMR resonance of the cationic part of 3 A / 3 B at −37.0 ppm is more low‐field shifted compared to those of the related [M(AlCp*) 3 ] + (M=Al, Ga, In, Tl)[ 25 , 31 ] as well as to [(AlCp*) 4 ] (Figure 1b ). Moreover, the silicon atom gives rise to a signal at δ 29 Si=+57.9 ppm (cf.…”

Low‐Valent MxAl3Cluster Salts with Tetrahedral [SiAl3]+and Trigonal‐Bipyramidal [M2Al3]2+Cores (M=Si/Ge)

“…For compounds 3 A / 3 B , bands assigned to the stretching vibrations of the Si−Al bonds in the SiAl 3 ‐cluster, the tetrahedral breathing modes, were detected at 454 cm −1 and 463/461 cm −1 (see Supporting Information, Figure S29). These values compare well to M−Al stretching vibrations reported for the cationic complexes of type [M(AlCp*) 3 ] + (M=Al, [25] Ga‐Tl [31] ) but are higher compared to the Raman band of [(AlCp*) 4 ] ($${\tilde{v}}$$ =378 cm −1 ). This indicates a higher strength of the M−Al bonds in the intermetallic compounds compared to the Al−Al bonds in tetrameric [(AlCp*) 4 ].…”

“…This observation points to a fluxional behaviour of the η 1coordinated Cp* ligand at silicon, but suggests that any exchange of Cp* ligands between silicon and the aluminium centres is slow on the NMR time scale. [30] The 27 Al NMR resonance of the cationic part of 3 A/3 B at À 37.0 ppm is more low-field shifted compared to those of the related [M(AlCp*) 3 ] + (M = Al, Ga, In, Tl) [25,31] as well as to [(AlCp*) 4 ] (Figure 1b). Moreover, the silicon atom gives rise to a signal at δ 29 Si = + 57.9 ppm (cf.…”

Cationic dialanes with fluxional π-bridged cyclopentadienyl ligands

“…The starting point for the synthesis of novel cationic dialanes was the reactivity study of Schnöckels [(AlCp*) 4 ] towards cyclopentadienylgermanium 18 and -tin 19 cations [MCp][F{Al(OR F ) 3 } 2 ] (M = Ge, Sn, R F = C(CF 3 ) 3 ), sparked by our discovery of mixed low-valent group 13 complex salts. 20 Reaction of [MCp] + salts with 0.25 [(AlCp*) 4 ] yielded a mixture of various compounds from which single crystals of the asymmetric aluminocenium cation [Al(Cp)(Cp*)][F{Al(OR F ) 3 } 2 ] grew (ESI†). Interestingly, addition of 0.5 equivalents of [(AlCp*) 4 ] yielded an elusive π-cyclopentadienyl bridged dialane [Cp(AlCp*) 2 ][F{Al(OR F ) 3 } 2 ] 1A as a colourless crystal (eqn (1), ESI†).…”