Republication or reproduction of this report or its storage and/or dissemination by electronic means isAbstract: Established IUPAC recommendations for the representation of configuration are reviewed briefly, and then methodologies are examined for dealing with regular polyhedra that are typically used when working with coordination numbers greater than 6. More than one method is available and can be used for many such geometries, but the deviations from regular polyhedral geometries that are typically found in such molecules can make it difficult to arrive reproducibly at the same description for a complex using purely objective criteria. Recommendations are made for some geometries of coordination numbers 7, 8, and 9, but not for higher coordination numbers.

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The reaction of [Cp*TaCl 4 ] (1a, Cp* ϭ C 5 Me 5 ) or [CpЈTaCl 4 (THF)] (1b, CpЈ ϭ C 5 MeH 4 ) with PH 2 Fc [Fc ϭ Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 )] and PH 2 CH 2 Fc gives the primary ferrocenylphosphine complexes [Cp R TaCl 4 (PH 2 Fc)] [Cp R ϭ Cp* (2a), CpЈ (2b)] and [Cp R TaCl 4 (PH 2 CH 2 Fc)] [Cp R ϭ Cp* (3a), CpЈ (3b)], respectively. 1 reacts with (PH 2 ) 2 fc [fc ϭ Fe(η 5 -C 5 H 4 ) 2 ] or with the new secondary phosphine PH(CH 2 Fc) 2 to give the ferrocenyl-bridged complexes [{(Cp R TaCl Complexes 1b and 2Ϫ5 were characterised spectroscopically ( 1 H, 13 C, 31 P NMR, MS, IR ) and 1b, 2a, 3a, 4a, and 5a also by X-ray crystallography. The electrochemical behaviour of complexes 3a and 5b exhibits complicated electron transfer processes, which are due to the complex redox activity of the corresponding ferrocenylphosphine ligands PH 2 CH 2 Fc and PH(CH 2 Fc) 2 .

The reaction of [WI 2 (CO) 3 (NCMe) 2 ] with an excess of FcCH 2 PH 2 [Fc ) Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 )] in THF leads to formation of the seVen-coordinate pentanuclear complex salt [WI(CO) 2 (PH 2 CH 2 Fc) 4 ]I (1), while other compounds of the type [MI(CO) 2 L 4 ]I (with M ) Mo, W and L ) PH 2 Fc, PH 2 CH 2 Fc) could not be obtained. The obserVation of this exceptional behaVior was supported by quantum chemical calculations. Compound 1 is stable in the solid state, while an equilibrium between 1, [WI 2 (CO) 2 (PH 2 CH 2 Fc) 3 ], and FcCH 2 PH 2 is ob-serVed in solution. The structure of the cation [WI(CO) 2 (PH 2 -CH 2 Fc) 4 ] + is an almost ideal trapezoidal octahedron, with the two CO ligands sharing one octahedral position.