Low-Valent Organometallic Compounds
Low-valent main and transition metal compounds are an exciting research field in the area of organometallic chemistry. Cluster compounds have structural and chemical properties that make them interesting from a technological point of view as well as from the perspective of a basic researcher. Oligomeric metal clusters, which are connected by metal-metal bonds and kinetically stabilized by an organic ligand shell, are intermediates between the molecular world and the "bulk" material. The interesting question is: How many metal atoms are needed (or how large must be a cluster) to model the properties of the "bulk" material.
In the range of the low-valent main group element compounds, the compounds especially of the group 13 (Al, Ga) and 14 (Si, Ge) were investigated in the past. The cluster [Al77(N(SiMe3)2)20]2- and [Ga84(NTMS2)20]x- (x = 3, 4) synthesized by the Schnöckel group are among the largest structurally characterized metalloid cluster compounds.[1,2] In addition to such large cluster compounds, low-valent compounds containing much less metal atoms, were synthesized, in particular neutral MI and MII of the type [MR]x and R2M-MR2. These compounds are not only interesting target compounds, but are also expected to show a diverse chemistry.
In the last decade, base-stabilized molecules have received agrowing interest. In particular N-heterocyclic carbenes (NHC) were found to stabilize unforeseen compounds such as (NHC)2Si2, formally containing a Si2 molecule with Si=Si double bond andSi atoms in the formal oxidation state 0. Since this initial report, several interesting main group element compounds of this type with interesting bonding properties have been reported.
We are interested for some time in the synthesis, structure and reactivity of low-valent group 12 (Zn), low-valent group 13 (Al, Ga, In) and low-valent group 15-compounds (Sb, Bi).
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