Cp-phosphaferrocene hybrid systems

Racemic aldehyde 2 under similar reaction conditions yielded two diastereo-meric pinacols the configuration of all the products was assigned by X-ray diffraction. On the basis of these results a mechanistic scheme could be proposed to explain the stereochemical course of the coupling reactions [19]. It is assumed that the reaction proceeds via an intermediate titanaoxirane by insertion of a molecule of aldehyde 2 into the Ti—C bond - a proposal that has been put forward recently on the basis of DFT calculations [20]. The pinacol-type coupling products could be employed as bidentate P,P chelate ligands to Mo(CO)4 fragments however analogous experiments carried out with the olefinic derivatives 18 were unsuccessful [19]. 

As an overall cationic species, coordination of complex 24 to metals is feasible, as shown in the reaction with W(CO)s(THF) to produce the respective W(CO)5 complex. The P coordination is evident from the tungsten satellites in the P NMR spectrum [22]. 

with anion 26 under similar reaction conditions only one diastereomeric half-sandwich complex, 27a (R = Me), was observed in the crude product, isolated in high yield after chromatographic workup, and characterized by X-ray diffraction. The relative configuration is such that the two bulky groups - the PPh3 ligand and the Cp Fe moiety - avoid steric interference (Fig. 1.5.6) [24]. 

A couple of subsequent reactions which were carried out with the Cp complex 27 all proceeded diastereoselectively, presumably with retention at Ru. These included exchange of the chloride for an iodide ligand under retention as determined by X-ray diffraction, reaction with NaOMe in MeOH to give the neutral monohydride as a single diastereomer, and removal of the chloride with AgBp4 

The acetonitrile molecules are labile and can be exchanged for other mono- or bidentate ligands such as pyridine or tmeda. With N-(2-dimethylamino)ethylmor-pholine two diastereomers are obtained in excellent yield in a ratio of 3 2 (de 20%), one of which could be characterized by X-ray diffraction analysis. 

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