Na-X bonds

The broken bonds (boldface = dissociated fragment) BDEs (boldface = recommended data reference in parentheses) Methods (reference in  

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Fig. 10. Valence sum around a cation. If the oxygen atoms (from Table X) are closer to the sodium ion, they have a higher bond valence. The bond length (A) is drawn for each Na-- 0 bond along it, and the bond valence is shown on the oxygen atom. Thus, the total negative charge of —1.0 that must surround the Na" for local electroneutrality is divided in accord with the distances.

Reactions of metal carbonyl anions with 1,1- or 1,2-dihaloalkanes also do not yield an alkyl metal product, owing to rapid 1,1- or 1,2-M—X elimination e.g., the reaction of Na[Mn(CO)5] and 1,2-dibromoethane produces MnBrfCO), and C2H4, rather than Mn(CH2CHjBr)(CO)5 or (OC)5MnCH2CH2Mn(CO)s. Reactions of metal carbonyl anions with perfluoroalkyl halides produce metal carbonyl halides, rather than perfluoro-alkyl-metal species. This is because of the reverse polarity of the C—X bond . 

Polar protic solvents like H2O and ROH solvate both cations and anions well, and this characteristic is important for the SnI mechanism, in which two ions (a carbocation and a leaving group) are formed by heterolysis of the C-X bond, The carbocation is solvated by ion-dipole interactions with the polar solvent, and the leaving group is solvated by hydrogen bonding, in much the same way that Na" and Br are solvated in Section 7.8C. These interactions stabilize the reactive intermediate. In fact, a polar protic solvent is generally needed for an SnI reaction. SnI reactions do not occur in the gas phase, because there is no solvent to stabilize the intermediate ions. 

Halogermane reductions by complex hydrides are efficient, preferred methods for germane synthesis " . The complex hydrides used are MBH (M = Li, Na, K) and LiAlH.,. Reduction of Ge—X bonds by this method can be used for any molecule that otherwise is unsusceptible to complex hydride reduction or reaction. Lithium tetrahydroaluminate reduction of chiral halogermanes and alkoxygermanes results in inversion and retention of configuration, respectively. The LiBH., and LiAlH reactions require aprotic solvents, such as EtjO, THF, n-Bu O or glyme ethers. Sodium and K... 

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