Carbon-Metal Bonds in Organometallic Compounds

Organometallic compounds are named as substituted derivatives of metals. The metal is the base name, and the attached alkyl groups are identified by the appropriate prefix. 

When the metal bears a substituent other than carbon, the substituent is treated as if it were an anion and named separately. 

PROBLEM 14.1 Both of the following organometallic reagents will be encountered later in this chapter. Suggest a suitable name for each. 

SAMPLE SOLUTION (a) The metal lithium provides the base name for (CH3)3CLi. The alkyl group to which lithium is bonded is terf-butyl, and so the name of this organometallic compound is tert-butylithium. An alternative, equally correct name is 1,1-dimethylethyllithium. 

An exception to this type of nomenclature is NaC=CH, which is normally referred to as sodium acetylide. Both sodium acetylide and ethynylsodium are acceptable lUPAC names. 

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From the nature of the carbon-metal bonds in organometallic compounds, predict the products of the following reactions. Give your reasoning. 

Let s now turn our attention to the chemical behavior of these organometallic reagents. As mentioned previously, even though the carbon-metal bonds in these compounds are predominantly covalent, they often react as would be predicted for the corresponding carbanion, although the identity of the metal certainly modifies their behavior somewhat. As expected for carbanions whose pATa s would be in the... 

Carbon monoxide and isonitxile, which have an isoelectronic structure and serve as TT-acid ligand on transition metals, form various stable transition metal complexes. One of the most fundamental and important reactions with carbon monoxide and isonitrile in organometallic chemistry is their insertion into the carbon-metal bond of organometallic compounds (Scheme 1). 

The variety of bonding in organometallic compounds is enormous. We focus fairly narrowly here on the types of bonding found between transition metals and carbon and hydrogen atoms and on the interactions between metals and and n bonds between C atoms and C and H atoms. In particular, we seek to understand in some detail the process known as oxidative addition, as shown in reactions (13.1) and (13.2). 

The organic moiety most suitable to establish a stable sigma carbon-metal bond in difficult cases seems to be an electronegative radical such as the phenyl or acetylenic group. Examples of new and interesting phenyl organometallic compounds are triphenylchromium (64), pentaphenyl-antimony, tetraphenyltellurium, and triphenyliodine (134)- Nickel and other metals can be transformed into acetylides (89). 

Predict whether the carbon-metal bond in each of these organometallic compounds is nonpolar cova-... 

Grignard reagents belong to the larger class of substances known as organometallic compounds. The reactivity of these compounds is determined by the polarized nature of the carbon-metal bond in which... 

Predict whether the carbon-metal bond in these organometallic compounds is nonpolar covalent, polar covalent, or ionic. For each polar covalent bond, show the direction of its polarity using the symbols 5-1- and 5-. 

In this Chspter, we undertake our first discussion of a broad class of organic compounds called organometallic compounds, compounds that contain a carbon-metal bond. In recent years, there has been an enormous explosion in our understanding of their chemistry, particularly as stereospecific (and often enantioselective) reagents for synthetic chemistry. We have already seen one example in the Sharpless enantioselective epoxidation of alkenes (Section 11.8D). 

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