14.2 Carbon-Metal Bonds in Organometallic Compounds 14.1 ORGANOMETALLIC NOMENCLATURE 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. CHa=CHNa (CH;CH2)2Mg H Cyclopropyllithiur Im Dieth Magnesiun When the metal bears a substituent other than carbon. the substituent is treated as if it were an anion and named separately Igl (CH3CH,)2AICI hy magnesium iodide Diethylaluminum chloride PROBLEM 14.1 Both of the following organometallic reagents will be encoun- tered later in this chapter. Suggest a suitable name for eacl (a)(ch3)3CLi SAMPLE SOLUTION (a) The metal lithium provides the base name for(CH3)aCLi The alkyl group to which lithium is bonded is tert-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 IUPAC names 14.2 CARBON-METAL BONDS IN ORGANOMETALLIC COMPOUNDS With an electronegativity of 2.5(Table 14.1), carbon is neither strongly electropositive nor strongly electronegative. When carbon is bonded to an element more electronegative han itself, such as oxygen or chlorine, the electron distribution in the bond is polarized TABLE 14.1 Electronegativities of Some Representative Elements Element Electronegativity odNcH 3.0 3.0 2. 19 mAM 1.6 1.0 Na 0.9 0.8 Back Forward Main MenuToc Study Guide ToC Student o MHHE Website14.1 ORGANOMETALLIC NOMENCLATURE 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 encoun￾tered later in this chapter. Suggest a suitable name for each. (a) (CH3)3CLi (b) SAMPLE SOLUTION (a) The metal lithium provides the base name for (CH3)3CLi. The alkyl group to which lithium is bonded is tert-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 NaCPCH, which is normally referred to as sodium acetylide. Both sodium acetylide and ethynylsodium are acceptable IUPAC names. 14.2 CARBON–METAL BONDS IN ORGANOMETALLIC COMPOUNDS With an electronegativity of 2.5 (Table 14.1), carbon is neither strongly electropositive nor strongly electronegative. When carbon is bonded to an element more electronegative than itself, such as oxygen or chlorine, the electron distribution in the bond is polarized H MgCl CH3MgI Methylmagnesium iodide (CH3CH2)2AlCl Diethylaluminum chloride Li H Cyclopropyllithium CH2 CHNa Vinylsodium (CH3CH2)2Mg Diethylmagnesium 14.2 Carbon–Metal Bonds in Organometallic Compounds 547 TABLE 14.1 Electronegativities of Some Representative Elements Element F O Cl N C H Cu Zn Al Mg Li Na K 4.0 3.5 3.0 3.0 2.5 2.1 1.9 1.6 1.5 1.2 1.0 0.9 0.8 Electronegativity Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website