Boranes. XXXIV. Preparation of some nido-dicarbanonaborane(11)'s and nido-dicarbadecaborane(12)'s

Abstract

Octaborane(12) reacts with acetylene in diethyl ether to give a 65% yield of a mixture of «/¿o-dicarbanonaborane(ll), B7C2Hn, and w'cfo-dicarbadecaborane(12), 802 2( members of the B"C2H"+4 series of carboranes. Boron-11 nmr spectra suggest that B7C2Hn is the first example of a carborane containing an integral -BH2 group. The reaction of B8H12 with 2-butyne in diethyl ether produces B7C2H9(CH3)2 and B8C2Hi0(CH3)2 in 78% yield. Boron-11 and pmr evidence suggests that B7C2H9(CH3)2 differs in structure from B7C2Hn and contains its "extra" hydrogens in two distinct bridging locations. B8C2Hi2 and B8C2H10(CH3)2 appear to be in the decaborane( 14) geometry, carbon atoms occupying the 5,6 positions. One minor product of this reaction is a new 2,3 isomer of closo-B5C2H5(CH3)2. Reactions of B8Hi2 with other acetylenes are mentioned. Reactions of /z-nonaborane( 15) with C2H2 and with 2-butyne are discussed. he members of the B"C2H"+4 series of nido carboranes for n = 43 and = 94 have proven to be precursors to numerous interesting and, in some cases, potentially commercially useful compounds. Pyrolysis of B4C2H8 generates the closo carboranes 1,5-B3C2H5, l,6-B4C2He, and 2,4-B5C2H7,5 the latter of

The Additive Nature of Energy Penalties in 10‐Vertex nido‐(Car)boranes

“…This characteristic feature is accompanied by the distortion of the cluster structure in such a way that the 3k carbon atom lies almost in the plane of the 4k vertices [5,7,8,10, see Figure 2a, CC (3)(4)(5)]. This distortion counteracts the destabilization of the CC relationship and results in a diminished E inc [CC (3)(4)(5)].…”

“…In the presence of extra hydrogen atoms, however, some more rules are needed. Figure 3 shows the 6,9-and 5,7-isomers of C 2 B 8 H 12 [6,7] and their dianions. [8,9] …”

“…nido-5,6-C 2 B 8 H 12 (JD) and nido-5,7-C 2 B 8 H 12 (JA) represented the first case of skeletal isomers in nido-carboranes. [7] A large number of C 2 B 8 H 12 isomers (Table 5) was computed in order to obtain a reliable structural increment system for 10-vertex nidocarboranes. Calculated (HF/6-31G*) geometries for nido-6,9-C 2 B 8 H 12 (JM) and nido-6,9-C 2 B 8 H 12 (JS) have been reported before.…”

Ten-vertex dicarbaboranes from nido -5,6-C 2 B 8 H 12

“…nido-[7,8-C 2 B 9 H 12 ] À þ Fe 3þ þ 3H 2 O / nido-5,6-C 2 B 8 H 12 þ B(OH) 3 þ Fe 2þ þ 3½ H 2 (1) Isolated were also minor products from this reaction identified as nido-4,5-C 2 B 7 H 11 (yield 4.5%, later formulated [11] as arachno-4,5-C 2 B 7 H 13 ) and nido-5,6-C 2 B 8 H 11 -10-X compounds (X ¼ Cl and. Reaction (1) has been just recently optimized by minimizing the losses of 1 due to its hydrolysis in the hexane solution during the preparation.…”

“…An alternative route to 1 and its C-substituted derivatives is based on heating 4-L-arachno-B 9 H 13 compounds (L ¼ OEt 2 [17] and SMe 2 [7]) with alkynes R 1 R 2 C 2 (R 1 , R 2 ¼ H, Me, and Ph substituents), (yields 34e60%) (Scheme 2, path A): 4-L-arachno-B 9 H 13 þ R 1 R 2 C 2 / 5,6-R 1 R 2 -nido-5,6-C 2 B 8 H 10 þ L.BH 3 (2)…”