Selected Molecular Structures

In this section the structural details of a selected number of compounds are given in greater detail. 

In this Section a few structures have been selected and the structural results and authors comments have been given in greater detail. No attempt has been made to cover all classes of ligand or to give a group-by-group survey. 

In the tantalum-aikylidyne complex Ta(i7 -C8Me8XCPh)(PMe8)aCl (4) the Ta—C triple bond distance is 1.849(8) A and the Ta—C —angle is 171.8(6)°. The geometry about the tantalum is best described as a four-legged piano stool.  

A titanium complex, carbonyl bis( / -cyclopentadienyl)(j -diphenylacetylene)-titanium (5) has been structurally characterized. The Ti—C distances to the acetylene are 2.107(7) and 2.230(7) A, respectively. The long central Ti—C bond is thought to be caused by the proximity of the carbonyl group. Another titanium complex containing a ketene bonded to the metal has had its structure 

The structure of ( -C8Me4Et)2V(CCCeH2Me3) has been determined and provides a value for the V —C(j/ ) distance viz. 2.032(13) A. It is also noteworthy that the plane of the benzene ring and the co-ordination plane of the vanadium (taking the centroids of the two C5 rings and Cl as our defining points) 

The structure determination of (CsHgjaWCCO), provides the first definite example of a molecule containing a bent ligand. The angle between the 

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Polylithium organic compounds Syntheses and selected molecular structures... 

Figure 2.14 Absorption of ultraviolet by selected molecular structures.

Table 14 Selected molecular structure parameters (In A and degrees) for the minimum structures of heteroles HEC4H4 at the MP2 and B3LYP level of theory...

I, 2, and S of this series. The tabulation is intended to be comprehensive and in order to make the structural information more accessible a set of cross reference tables, based upon metal and ligand type, is included (Section 3). Section 4 contains a table of metal - metal bond distances and notes on selected molecular structures are presented in Section 5. 

The attachment of an alkyl group to a selected molecular structure is called alkylatioii. We will encounter this method of forming carbon—carbon bonds repeatedly in later chapters dealing with other functional groups. Alkylation is one of the fundamental reactions used to construct complex structures. 

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