Recent studies have extended the chemical principles' of boron hydrides to include boron-boron bonds between polyhedra or polyhedral fragments2 and rearrangements3 4 of boron frameworks. We report here results, suggesting new areas of research, including a condensation reaction to form B20H18-' from BioH,0-o, a substitution reaction on BioH,0-2 to form BoH90H-2, a suggestion of polyhedral isomerization, the presence of essentially covalent metal bonds to B in BloH1o-2, and a new type of free radical.The B2,H18-2 Ion.-Reaction of dilute aqueous BloHio(HNEt3)2 solutions with 1eCl3 yields nearly white crystals of B2eH,8(HNEt3)2, insoluble in cold water but soluble in several polar organic solvents, melting with decomposition at 175-1740C, and having a density of 0.941 gm cm-3. The rough molecular weight of 420 from the vapor pressure depression of CH30H solutions allowed the number of molecules per unit cell of the crystal to be fixed at two and led to the crystallographically determined molecular weight of 437 i: 2 in agreement with the expected value of 439. Moreover, the ion is centrosymmetric, since the space group is P21/a. The B1' nuclear magnetic resonance (NMR) spectrum ( Fig. 1) is related to that2 of BcH10-' in a way which suggests that one apex' B atom and one equatorial B atom of each Bo unit are involved in the formation of B20H18-. The only structure' consistent with the present valence theory is now being tested by X-ray diffraction methods in this laboratory. The ultraviolet spectrum has intense bands at 293 and 230 my, neither of which is present in the BoHlo -2 spectrum in noticeable intensity.The chemical reaction 2B0oH10-2 + 4Fe+3 B20H18-2 + 4Fe+2 + 2H+ goes to 95 per cent yield in aqueous solution with slight excess of Fe +3. Analytical results for the HNEt3+ salt and the NMe4+ salt (mp > 300°C) are shown in Table 1.The BoH9OH-2 Ion.-A quantitative reaction of B2oH18(HNEt3)2 with aqueous base, B2oH18(HNEt3)2 + 40H -> 2BXH9OH-2 + 2NEt3 + 2H20, establishes a substituted BHio -2 ion. The salt K2B,,HOH 2H20 loses water at room temperature to form a stable monohydrate (Table 1) but is stable as high as 300°C except for further loss of H20. The BioHO9H-2 ion may be the same as that prepared by quite different methods by Knoth et al.,5 whose research we became aware of after completion of our own. Polyhedral Isomerization.-Upon initial deuteration in strong acid, BioHlo-is apex5 substituted. Also, when freshly prepared, BioH90H-2 is apex substituted.The large high field doublet, initially like7 that in BioH1o , of the B"1 NMR spectrum becomes unsymmetrical after a few hours at room temperature, thus suggesting an apparent partial migration of the substituent. A probable transformation process is shown in Figure 2. If this process is more general, it may occur in B12HIOX2-2, where two X atoms on adjacent B atoms may wander to nonadjacent 729
