Protonations with HX X Cl or I

Treatment of the alkylidyne(cyclopentadienyl)metal species 4 with halo-acids (HX X = Cl, Br, I) has been described in Section I. The carbene- or acyl-ligated metal complexes so formed are stabilized by coordination to the metal of the halide ion intrinsically involved in the protonation reaction, thus highlighting the important difference between employing HX and HBF4 Et20 in the protonations. 

This difference in behavior is even more pronounced when the metalla-carbaborane salts 1 are protonated with HX acids, as once again the polyhedral c e becomes intimately involved in the reactivity. Thus, treatment of dichloromethane solutions of lb, la, or If with aqueous HI yields, within seconds, the salts [Y][c/o o-l,8-Me2-l l-(CH2R)-2-I-2,2,2-(CO)3-2,l,8-WC2B,Hg] (R = Me, 35a CjH4Me-4, 35b CjH40Me-2, 35c) (32,39). The salt 35d was likewise prepared from la and aqueous (or dry 

NEt4CI (excess), THF, 5 days or NEt4CI (excess), THF, U.V., 3 hours 

The synthetic utility of the salts 35 is further demonstrated by treatment of 35b with the alkynes PhC=CR (R = Ph or Me), followed by addition of AgBp4. These reactions afford the complexes [c/o50-l,8-Me2-l 1-(CH2C6H4Me-4)-2 ( PhC2R 2,2-(CO)2-2,1,8-WC2B,Hg] (R = Ph, 

42a Me, 42b), respectively, by abstraction of the halide and coordination of the alkyne to the metal vertex of the polyhedron (39). This vertex also loses a molecule of CO leaving the alkyne to act as a 4e donor to the metal, but the icosahedron is otherwise unaltered. This synthesis may also be used to generate dimetal species, by substitution of the alkyne molecule with an alkylidyne-metal complex in the reaction (43). Thus the products obtained by treating 35b (Y = NMe3Ph or AsPh4) respec- 

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