CpFe+ group

The situation is the contrary for the electrochemical behavior of the two cycles. These show distinct cyclic voltammograms due to the altered spatial distribution of the three electroactive CpFe groups. The differences in the electrochemistry of 83 and 84 are not dramatic but significant and their interpretation is not straightforward. A cycle with smaller bridging units such as 85, forcing the... 

With CpFe(CO)2CH2C6H5, the base peak corresponds to C5H5FeCH2C6Hs peaks due to the parent and (P—CO)+ are relatively weak, and other ions observed are characteristic of CpFe groups. The pentafluorobenzyl complex, on the other hand, shows a base peak at mje 181, corresponding to C7H2F and the only other significant ions are the parent and C5H5Fe+ (49). 

Scheme 3. Benzylation activation of arenes by the 12-electron CpFe+ and the 13-electron CpFe groups (see also Scheme 4).

Scheme 11.2 One-pot dodecaallylation of hexamethylbenzene (a) induced by the CpFe+ group and (b) hindered rotation of the branches.

Scheme 11.4 Octabenzylation of durene induced by the CpFe+ group (right Fe = T 5-C5H5, PF6 ).

Recently the first examples of complexes between the four-membered amidinato-Group 13 metal(l) heterocycles and transition metal fragments were reported. Complexes of the type CpFe(CO)2[M(X) But(NR)2 ] (M = Al, Ga, In X = Cl, Br R = Pri, Gy) were formed in salt-elimination reactions between Na[CpFe(CO)2] and [But(NR)2]MX2. A series of complexes between the four-membered amidinato-Group 13 metal(l) heterocycles and Group 10 metal(O) fragments have been prepared according to Scheme 35. ... 

Belonging to group (i) are alkylmetal carbonyls and cyclopentadienylmetal alkyl carbonyls of formula RMn(CO)5, CpFe(CO)2R, and CpMo(CO)3R. Solvent dependence of the reaction of MeMn(CO)5 with CjHi,NH2 is illustrated also in Table I. The rate varies markedly with the dielectric constant and with the nucleophilic power of the solvent. For example, on going from dimethylformamide to mesitylene, the rate of insertion is reduced by 10. Similarly, the sequence MeCN > MejCO > THF > CHCI3 > CjHj was reported for the reaction of MeMn(CO)5 with P(0CH2)3CR (R = Me and Et) in various solvents (97). Analogous trends were observed for the insertion reactions of CpFe(CO)2R and CpMo(CO)3R (48, 80, 98). 

Within group (i), square-planar EtPt(CO)(AsPh3)Cl inserts more rapidly than six-coordinate EtIr(CO)2(AsPh3)Cl2. In THE at 40°C, the relative k s are 9 and 1. Comparison of group (ii) alkyl carbonyls reveals the order MeMn(CO)5 > CpMo(CO)3Me > CpFe(CO)2Me. The ratios of the k s are 23 I and 100 1, respectively, in THF at 25° and 50.7°C. The higher reactivity of manganese than of molybdenum is a consequence of the relative entropies, whereas the lowest reactivity of iron is caused by its Jff (Table III). 

On the other hand, the yield of ferrocene in a [CpFe(CO)2]2 matrix (50) is not altered up to 80° C, so that here either Cp transfer is not possible or the position on the Fe atom is blocked by CO groups. It seems plausible to consider a rapid ligand condensation as a very early prethermal competitive reaction. One can thus set up a hypothetical reaction scheme such as [using PhHCr(CO)3 as the matrix compound] ... 

Silicon-transition metal chemistry is a relatively new area. The work of Hein and his associates (1941) on Sn—Co derivatives established the possibility of forming bonds between a Group IVB metal and a transition element 139), but it was another fifteen years before CpFe(CO)2SiMej 203), the first of many silyl derivatives, was synthesized. The interest in these compounds derives from (1) comparison with the corresponding alkyl- and Ge-, Sn-, and Pb- transition metal (M) complexes, including the role of ir-back-bonding from filled d orbitals of M into empty d orbitals on Si (or other Group IVB metal), and (2) expectation of useful catalytic properties from such heteronuclear derivatives. 

Fig. 28. Orientation of orbital with ir-symmetry on CpFe(CO)2 fragment and the orientation of these groups in CpFe(CO)2 3Ga.

We have demonstrated that a series of first row, Group 8 organometallic hydride complexes effect intermolecular hydride addition to coordinated n2-alkene, n2-vinyl ether, and a-alkoxyethy-lidene compounds (64). For example, one equivalent of CpFe(C0)PPh3(H) quantitatively reduces CpFe(CO)2(T12-CH2=CH2)+ to CpFe(C0)2CH2CH3 within one-half hour and leaves... 

Attempts thus far at using the samp Group 8 organometallic hydride complexes as hydride donors to the coordinated CO on CpFe(CO)3+ (1) have been unsuccessful. Reaction of 1 with... 

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