Complexes of O-Donors

The yellow acetylacetonate contains octahedrally coordinated rhodium (Rh-0 1.992 A O-Rh-O 95.3°) [83], 

The corresponding tri- and hexa-fluoroacetylacetonates may be similarly prepared. The stability of the acetylacetonate is such that not only can it be resolved on passage through a column of D-lactose, but the enantiomers retain their integrity on nitration or bromination. 

Extended refluxing of hydrated RhCl3 with excess oxalate leads to the tris complex, the potassium salt crystallizing as orange-red crystals with Rh-O 2.000-2.046 A. 

Rh(C204)3 was resolved by Werner as the strychnine salt but other ions, such as Coen3+ and Niphen3+, have been used more regularly for this [84]. 

The dinuclear rhodium(II) acetate is described in section 2.8.2 the dinuclear structure is retained on one-electron oxidation, but when ozone is used as the oxidant, a compound with a trinuclear Rh30 core is formed, analogous to those formed by Fe, Cr, Mn and Ru. (It can also be made directly from RhCl3.) 

The bond lengths make a more regular octahedron than in the d5 ruthenium analogue, possibly partly a consequence of the symmetrical electron distribution in the d6 Rh3+ ion (Table 2.4) [85]. 

Complexes of O-donors are relatively rare, explicable by the soft nature of the divalent ions. A telling indication is that sulphoxide ligands will only bind through O if steric effects make S-bonding impractical. The most important complexes are diketonates and carboxylates (for the aqua ions see section 3.5). 

There is significant metal-metal bonding in the platinum compound, whose geometry involves a square of platinum atoms another important difference is that the coordination geometry is square planar in palladium acetate but octahedral in the platinum analogue. Different oligomers exist in solution, broken down by adduct formation. Palladium(II) acetate may be obtained as brown crystals from the following reaction [65]  

The importance of palladium acetate lies in its ability to catalyse a wide range of organic syntheses functionalizing C-H bonds in alkanes and in aromatics, and in oxidizing alkenes. It has been used industrially in the 

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A number of neutral complexes of O-donor Lewis bases have been made, such as ten-coordinate tra s-Ce(N03)4(Ph3P0)2 and octahedral CeCUL2 [L = Ph3 PO, Ph3AsO,... 

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