This short review describes the synthesis, structural and spectroscopic properties, and reactivity studies of low valent transition metal clusters that contain nitrene/imido ligands. The synthetic routes to these nitrene/imido-capped transition metal clusters (both homometallic and heterometallic) are generalized. Numerous structures of these species have been established by X-ray crystallography in recent decades. Their geometric features, which are governed by the capping ligands and metal atoms, are described, and the1H- and15N-NMR studies of these clusters with (μ3- or μ4-NH) nitrene ligands are highlighted. The different degrees of interaction of nitrogen atoms with metals in μ4-NH and μ3-NH bonding modes result in distinct NMR parameters. The influences of the coordinated ligands and metal atoms on the NH proton signal are also discussed. The electrochemical responses of these clusters are directly related to the nature of the capping ligands, and the addition/reduction of cluster valence electron (CVE) leads to marked changes in the cluster geometry. The μ3-imido capped triruthenium metal clusters are known to be the active intermediates in the reductive carbonylation of nitro-compounds. The proposed catalytic mechanisms are discussed.
- Transition metal cluster
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