Homoleptic complexes framework

Various potassium metal alkoxides have been structurally characterized. One of the first examples reported was the homoleptic complex [K(/43-OBu )2(/r-OBu )3U2(OBu )4] which has the confacial bioctahedral U2O9 framework with the K ion occupying a pocket between the two uranium(iv) atoms (U-U, 3.631 A). ... 

A large number of structurally characterized bis(trimethylsilyl)amido complexes now exist Table 5 gives a representative selection of monometallic homoleptic compounds, both base-free and with coordinated ethers. Other examples are known with coordinated fiuorobenzenes, isonitriles,methylated pyridines, various amines (TMEDA, PMDTA, TMPDA (Tetra-methylpropylenediamine), BzNMe2 (benzyldimethylamine)), Ph PO, (Bu"0)(Pr )C0, and l,3-(Pr )2-3,4,5,6-tetrahydropyrimid-2-ylidene. Their structures illustrate the complex interactions between metal size, ligand bulk, and molecular structure that exist with these metals. For example, among the alkali metal base-free species, the unsolvated Li derivative crystallizes as a cyclic trimer, whereas the Na salt is found both as a trimer " and as infinite chains of [Na-N(SiMe3)2—] units. The potassium, rubidium, and caesium derivatives exist as discrete dimers in the solid state, constructed around planar [M—N-]2 frameworks. 

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