ELECTRONIC-STRUCTURE OF A [TC2(MU-O)3CP]N POLYMER WITH A VERY SHORT METAL-METAL BOND

This recently synthesized polymer (with C5Me5) has a very short Tc-Tc distance of 1.867 angstrom. Its electronic structure is discussed by using molecular models and band calculations. The net bonding in a model CpTcO3TcCP- is best described qualitatively as sigma-2(pi-sigma)4-sigma*, i.e. a net bond of approximate order 2.5. The details of the polymer's electronic structure are consistent with this. While bonding in multiply bridged dimers or polymers is never easy to sort out, we think the short Tc-Tc bond is consonant with a multiple metal-metal bond superimposed on an already short Tc-Tc contact enforced by the three bridging oxygens.