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The nickelacarboranes [NEt4][2-(η3-C3H4R)-closo-2,1,7-NiC2B9H11] (R = H (1a), Ph (1b)) have been synthesized via reaction between [Na]2[nido-7,9-C2B9H11] and [Ni2(μ-Br)2 (μ3-C3H4R)2] in THF (THF = tetrahydrofuran), followed by addition of [NEt4]CI. Protonation of 1a in the presence of a donor ligand L affords the complexes [2,2-L2-closo-2,1,7-NiC2B9H11] (L = CO (2), CNBut (3)). Addition of PEt3 (1 equiv) to 2 produces quantitative conversion to [2-CO-2-PEt3-closo-2,1,7-NiC2B9H11], 4. Species 2–4 exhibit in solution hindered rotation of the NiL2 fragment with respect to the η5-C2B9 cage unit. Protonation of la in the presence of a diene affords the neutral complexes [2-(η2:η2-diene)-closo-2,1,7-NiC2B9H11] (diene = C5Me5H (5), dcp (6), cod (7), nbd (8), chd (9), and cot (10a); dcp = dicyclopentadiene, cod = 1,5-cyclooctadiene, nbd = norbornadiene, chd = 1,3-cyclohexadiene, and cot = cyclooctatetraene). Variable temperature 1H NMR experiments show that the {Ni(diene)} fragments are freely rotating even at 193 K. A small quantity of the di-cage species [2,2′-μ-(1,2:5,6-η-3,4:7,8-η-cot)-(closo-2,1,7-NiC2B9H11)2] (10b) is formed as a coproduct in the synthesis of 10a. This species can be rationally synthesized by protonation of la and subsequent addition of 10a. [ABSTRACT FROM AUTHOR]

The carborane anion [closo-2-CB10H11]− undergoes a polyhedral expansion reaction with [Co(CO)3(NO)] in tetrahydrofuran (THF) to afford [2-CO-2-NO-closo-2,1-CoCB10H11]−, isolated as the [N(PPh3)2]+ salt 1a. An X-ray diffraction study confirmed that the NO group is linearly bonded to cobalt. The CO ligand in 1a is readily replaced by PPh3 in the presence of Me3NO, or by PEt3 or CNBut directly, to give the species [N(PPh3)2][2-L-2-NO-closo-2,1-CoCB10H11] [L=PPh3 (1b), PEt3 (1c), CNBut (1d)]. Reactions of these anionic complexes with electrophilic reagents are exemplified by treatment of 1c with CF3SO3Me in CH2Cl2–THF to give the neutral, zwitterionic B-THF species [2-NO-2-PEt3-7-O(CH2)4-closo-2,1-CoCB10H10] (3a), and by the reaction of 1b with [CuCl(PPh3)]4 and Tl[PF6] in THF to give bimetallic [2,7,11-{Cu(PPh3)}-7,11-(μ-H)2-2-NO-2-PPh3-closo-2,1-CoCB10H9] (4b). X-ray diffraction analysis of crystals of 4b confirmed the presence of a Co&z.sbnd;Cu bond. [Copyright &y& Elsevier]

Addition of PPh2CI and TI[PF6] to CH2CI2 solutions of [N(PPh3)2][6,6,6-(CO)3-closo-6,1-FeCB8H9] (1) affords the isomeric B-substituted species [6,6,6-(CO)3-n-(PHPh2)-closo-6,1-FeCB8H8] [n = 7 (2a) or 10 (2b)]. Deprotonation (NaH) of the phosphine ligand in 2a, with subsequent addition of [IrCl(CO)(PPh3)2] and TI[PF6], yields the neutral, zwitterionic complex [6,6,6-(CO)3-4,7-μ-{lr(H)(CO)(PPh3)2PPh2}-closo-6,1-FeCB8H7] (3), which contains a B-P-Ir-B ring. Alternatively, deprotonation using NEt3, followed by addition of HC≡CCH2Br, affords [6,6,6-(CO)3-7-(PPh2C≡CMe)-closo-6,1-FeCB8H8] (4). Addition of [Co2(CO)8] to CH2CI2 solutions of the latter gives [6,6,6-(CO)3- -(PPh2-{(μ·η²:η²-C≡CMe)Co2(CO)6})-closo-6,1-FeCB8H8] (5), which contains a {C2CO2} tetrahedron. In the absence of added substrates, deprotonation of the PHPh2 group in compounds 2, followed by reaction of the resulting anions with CH2CI2 solvent, affords [6,6,6-(CO)3-n-(PPh2CH2CI)-closo-6,1-FeCB8H8] [n = 7 (6a) or 10 (6b)] plus [6,6-(CO)2-6,7-μ-{PPh2CH2PPh2}-closo-6,1-FeCB8H8] (7, formed from 2a), of which the latter species possesses an intramolecular B-P-C-P-Fe ring. Addition of Me3NO to CH2CI2 solutions of 2a causes loss of an Fe-bound CO ligand and formation of [6,6-(CO)2-6,7-μ-(NMe2CH2PPh2}-closo-6,1 -FeCB8H8} (8), which incorporates a B-P-C-N-Fe ring. A similar reaction in the presence of ligands L yields [6,6-(CO)2-6-L-7-(PPh2CH2CI)-closo-6,1-FeCB8H8] [L = PEt3 (9) or CNBut (10)], in addition to 8. [ABSTRACT FROM AUTHOR]

Reaction between [PPh4][closo-4-CB8H9] and [Ru3(CO)12] in refluxing toluene affords the unprecedented hexaruthenium metallacarborane salt [PPh4][2,3,7-{ Ru(CO)3}-2,6,11 -{Ru(CO)3}-7,11,12-Ru(CO)3}-3,6,1 2-(µ-H)3-2,2,7,7,11,11-(CO)6-closo-2,7,11,1-Ru3CB8H6] (1a), which contains a planar Ru6 'raft' supported by a {CB8} monocarborane cluster. Addition of [CuCI(PPh3)]4 and Tl[PF6] to a CH2CI2 solution of la results in simple cation replacement, forming the analogous [Cu(PPh3)3]+ salt (1b). The phenyl-substituted monocarborane [NEt4][6-Ph-nido-6-CB9H11] reacts with [Ru3(CO)12] in refluxing 1,2-dimethoxyethane to afford the pentaruthenium cluster species [N(PPh3)2]- [2,3,7-{ Ru(CO)3}-3,4,8-{ Ru(CO)3}-7,8-(µ-H)2-1-Ph-2,2,3,3,4,4-(CO)6-hypercloso-2,3,4,1-Ru3CB8H6] (2), after addition of [N(PPh3)2]Cl. Treatment of 2 with [CuCl(PPh3)]4 and Tl[PF6] in CH2CI2 forms the zwitterionic complex [10,12-{exoCu(PPh3)2}-2,3,7-{ Ru(CO)3}-3,4,8-{Ru(CO)3}-7,8,10,12-(µ-H)4-1-Ph-2,2,3,3,4,4-(CO)6-hypercloso-2,3,4,1-Ru3-CB8H4] (3). Substitution of CO by PPh3 with concomitant cation replacement occurs on introduction of [AuCI(PPh3)], Tl[PF6], and PPh3 to a CH2CI2 solution of 2, forming [Au(PPh3)2][2,3,7-{Ru(CO)2PPh3}-3,4,8-{Ru(CO)2PPh3}-7,8-(µ-H)2-1-Ph-2,2,3,3,4,4-(CO)6-hypercloso-2,3,4,1-Ru3CB8H6] (4). Crystallographic studies confirmed the cluster architectures in 1b, 2, and 3. [ABSTRACT FROM AUTHOR]

The docosahedral metallacarboranes 4,4-(PMe2Ph)2-4,1,6-closo-PtC2B10H12, 4,4-(PMe2Ph)2-4,1,10-closo-PtC2B10H12, and [N(PPh3)2][4,4-cod-4,1,10-closo-RhC2B10H12] were prepared by reduction/metalation of either 1,2-closo-C2B10H12 or 1,12-closo-C2B10H12. All three species were fully characterized, with a particular point of interest of the latter being the conformation of the {ML2} fragment relative to the carborane ligand face. Comparison with conformations previously established for six other ML2C2B10 species of varying heteroatom patterns (4,1,2-MC2B10, 4,1,6-MC2B10, 4,1,10-MC2B10, and 4,1,12-MC2B10) reveals clear preferences. In all cases a qualitative understanding of these was afforded by simple MO arguments applied to the model heteroarene complexes [(PH3)2PtC2B4H6]2- and [(PH3)2PtCB5H6]3-. Moreover, DFT calculations on [(PH3)2PtC2B4H6]2- in its various isomeric forms approximately reproduced the observed conformations in the 4,1,2-, 4,1,6-, and 4,1,10-MC2B10 species, although analogous calculations on [(PH3)2PtCB5H6]3- did not reproduce the conformation observed in the 4,1,12-MC2B10 metallacarborane. DFT calculations on (PH3)2PtC2B10H12 yielded good agreement with experimental conformations in all four isomeric cases. Apparent discrepancies between observed and computed Pt-C distances were probed by further refinement of the 4,1,2-model to 1,2-(CH2)3-4,4-(PMe3)2-4,1,2-closo-PtC2B10H10. This still has a more distorted structure than measured experimentally for 1,2-(CH2)3-4,4-(PMe2Ph)2-4,1,2-closo-PtC2B10H10, but the structural differences lie on a very shallow potential energy surface. For the model compound a henicosahedral transition state was located 8.3 kcal mol-1 above the ground-state structure, consistent with the fluxionality of 1,2-(CH2)3-4,4-(PMe2Ph)2-4,1,2-closo-PtC2B10H10 in solution. [ABSTRACT FROM AUTHOR]