Technetium compounds cyclopentadienyl complexes

Cyclopentadienyl (Cp) complexes (see Cyclopentadienyl) are known for almost all the metals of the periodic chart, including technetium. The compounds with transition metals usually possess covalent jt Cp M bonding. The nature of the metal Cp bond is multiple. The <7-bond is formed from the overlap of an empty d orbital of Tc with one of the frUed jt bonding molecular orbital on Cp with good symmetry. Back-donation is usually also present from the filled d orbitals of Tc to one of the empty n molecular orbitals on Cp. These molecules are usually called sandwich compounds (see Sandwich Compound), when there are two Cp ligands bonded to the metal, or half-sandwich complexes (see Half-sandwich Complexes) when only one Cp ligand is present. 

The formation of the hydrides may proceed via bis(jr-cyclopentadienyl)-metal halide complexes, since compounds such as (ir-CeH ReCU+CI-and (t-CjHOjWCU are known and are readily reduced to the neutral hydrides on treatment with lithium aluminum hydride 64) (Eq. 5). Treatment of technetium tetrachloride with sodium cyclopentadiene does not give a hydride analogous to that of rhenium. Molecular weight determina-... 

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