Cyclopentadienyl anions bridged in such a way that transition metal derivatives showing variable inter-fragment communication may be obtained. The workhorses were 2 [see publication list refs. 50, 104, 121,122, 133, 134, 136] and 3 [see refs. 97, 98, 99, 100, 103, 111, 112, 113, 118, 125, 128, 138, 140]; for 1 see ref. 124.

Cyclopentadienyl anions and dienes bridged in such a way that transition metal derivatives having a rigid stereochemistry.  For 4 and 6 see publication list refs. 92, 96; for 5 see ref. 106.

6π-Electron ligands featuring a 2+4 splitting of the π system. For 7 see publication list refs. 59, 72, 86, 87, 94, 110; for 8 see refs. 80, 81; for 9 see refs. 85, 107, 110; for 10 see refs. 149, 151.

Hydrotris(pyrazolyl)borate (Tp) anions figure as analogues of cyclopentadienyl anions. Paramagnetic Tp₂M-type compounds derived from 11 and 12 have been synthesized and studied by multinuclear NMR spectroscopy [see publication list ref. 164]. The NMR data have been reproduced theoretically. Ligand 13 leads to paramagnetic polymers [R. Feher, dissertation 1996].