2,4-Dimethylpentadienyl ligand

A more stable open jr-system is provided by the pentadienyl ligand. The 2,4-dimethylpentadienyl ligand was first used in the generation of homoleptic ( -2,4-Me2C5H5)3U (equation 46). The mixed-ligand uranium(III) complex [K(18-crown-6)][(2,4-Me2C5H5)2U(BH4)2] has been prepared by reaction of (2,4-Me2C5H5)3U with... 

In the lutetium complex one of the 2,4-dimethylpentadienyl ligands is r -bonded to the lutetium while the remaining two interact with the metal in r -fashion. 

In a molecule of (t -C7Hii)3Nd the C-C bond lengths between the carbon atoms in 1,2- and 4,5-positions (the average is 1.37 A) are shorter than the bond lengths between the carbon atoms in 2,3- and 3,4-positions (the average is 1.42 A). Hence, form B is more probable for the 2,4-dimethylpentadienyl ligands. 

In a molecule of Lu(ti -C7Hii)(t -C7Hii)2 one of the 2,4-dimethylpentadienyl ligands is Tj -bonded while two other are Tj -bonded to the Lu atom. Obtained C-C distances show that the r -bonded 2,4-dimethylpentadienyl ligands in the molecule are in form B and the r -bonded ligand exists in form D. 

The arene complexes of the early transition metals represent recent extensions 17-electron class of compounds. Thus, the 18-electron half open chromocene carbonyl complexes, (2, 4-dimethylpentadienyl)CpCrCO and the analogous Cp complex undergo one-electron oxidation with NOBF4 to provide the corresponding cationic 17-electron complexes. These complexes undergo ligand substitution processes ... 

MeC5H5CH2CH2CH(Me)C3H3(Me)], containing a dimeric chelate ligand derived from end-to-end fusion of two 2,4-dimethylpentadienyl groups (Figure 22). ... 

Again, a triple-decker species, B, in which a 2,4-dimethylpentadienyl group serves as the central ligand, may be involved as an Intermediate. The metallabenzene ligand in 27 again serves as a 6e neutral donor, enabling the central ruthenium center (formally a cation) to achieve an 18e count. 

Fig. 9.15 Molecular structures of bis(2,4-dimethylpentadienyl)iron showing the favoured gauche eclipsed conformation of the ligands and of ri -Me2C li )2T]L (L = CO,...

Miscellaneous Complexes.—Bis(2,4-dimethylpentadienyl)iron is found to exist as an open sandwich (24) in which the methyl groups are interlocked and an essentially gauche-eclipsed conformation is adopted. The complex is considered to be a true structural analogue of ferrocene with the pentadienyl ligands being nearly planar and the iron-carbon distances varying from 2.071(3) A (2,4-positions) to 2.084(3) A (3-position) and 2.114(8) A (1,5-positions). 

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