Direct insertion of transition metals into polyhedral carboranes. Structurally novel mono-, di-, and trimetallic small cage systems

Miller, Vernon R.; Sneddon, Larry G.; Beer, Don C.; Grimes, Russell N.

doi:10.1021/ja00817a013

Cited by 65 publications

(18 citation statements)

References 2 publications

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“…Description of the Structures. The two molecules are closely related (indeed isomorphous), each species containing a distorted Co3B3 octahedron with a triangular Co3 face bisected -0.027 ( 5) 7 (1) H6 0.001 (4) 0.250 (0) 0.268 (5) 3 (1) 0 The form of the anisotropic thermal parameter is [-(ß / 2 + ß 22k2 + ß33/2 + 012hk + 0l3hl + 023 kl)].…”

Section: Resultsmentioning

confidence: 99%

“…In the case of (C5H5)3-Co3B4H4, an alternative possibility having the capping BH group on the B3 rather than the Co3 face had not been entirely eliminated by the NMR data, but the Co3-capped geometry was strongly favored;8*3 the x-ray result confirms this judgment. 0.14935 (4) 0.16881 (3) 0.10872 (5) 0.00557 (3) 0.00280 (2) 0.00822 (6) 0.00048 (5) -0.00248 (8) -0.00017 (6) Cll 0.0472 (11) 0.2500 (0) -0.320,1 (13) 0.0043 (9) 0.0291 (25) 0.0044 (14) 0.0000 (0) -0.0055 (18) 0.000 (0) C12 0.1074 (13) 0.1653 (12) -0.3125 (11) 0.0232 (14) 0.0318 (14) 0.0107 (11) -0.0355 (20) 0.0156 (22) -0.028 (2) Cl 3 0.2184 (7) 0.2125 (9) -0.2841 (5) 0.0131 (7) 0.0220(17) -0.0063 (4) 0.0098 (15) 0.0050 (9) -0.003 (1) C11A 0.2200(11) 0.2500 (0) -0.3317(6) 0.0104 (10) 0.0494 (33) -0.0121 (5) 0.0000 (0) 0.0082 (11) 0.000 (0) C12A 0.1578 (8) 0.1761 (7) -0.3108 (9) 0.0095 (8) 0.0084 (5) 0.0080 (9) 0.0044 (11) -0.0029 (15) -0.009 (1) C13A 0.0472 (10) 0.1992 (7) -0.3157 (9) 0.0146 (10) 0.0072 (5) 0.0054 (9) 0.0057 (12) -0.0006 (16) -0.004 (1) C21 0.2951 (7) 0.1066 (6) 0.2225 (12) 0.0109 (5) 0.0090 (5) 0.0640 (15) -0.0008 (8) -0.0533 (10) 0.033 (1) C22 0.1814(10) 0.1027 (6) 0.2996 (9) 0.0166 (10) 0.0062 (5) 0.0069 (10) 0.0098 (12) -0.0008 (18) 0.003 (1) C23 0.1033 (10) 0.0484 (7) 0.2118 (11) 0.0161 (11) 0.0068 (5) Co2-Co2'), as are the two kinds of B-B bonds (1.724 (5) Á for B5-B6 vs. 1.716 (6) A for 5-5'). A similar comparison holds for (C5H5)3Co3B4H4, with metal-metal distances of 2.444 (1) A for Col-Co2 and 2.435 (1) A for Co2-Co2', and boron-boron lengths of 1.713 (5) A for B5-B6 and 1.692 (7) A for B5-B5'.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Structures of metalloboron clusters. X-ray studies of octahedral (.eta.5-C5H5)3Co3B3H5 and capped octahedral (.eta.5-C5H5)3Co3B4H4, a boron analog of tricobalt carbon clusters

Pipal¹,

Grimes²

1977

Inorg. Chem.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Structures of metalloboron clusters. X-ray studies of octahedral (.eta.5-C5H5)3Co3B3H5 and capped octahedral (.eta.5-C5H5)3Co3B4H4, a boron analog of tricobalt carbon clusters

Pipal¹,

Grimes²

1977

Inorg. Chem.

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“…[28] There are a number of catalyzed and noncatalyzed approaches to cage reduction/opening processes for large-cage closo-carboranes, but only a few for small C 2 B 4 cage systems. Despite some very interesting, but isolated, reports of reductive cage openings of closo-C 2 B 4 H 6 by Lewis bases, such as (CH 3 ) 3 N, [29] and low-valent metal compounds, [30] the only general, high-yield method of transforming either closo The use of naphthalene in these traditional two-electron reductive cage-opening reactions has several disadvantages. It introduces an additional reagent that must be removed from the reaction mixture before the nido-carborane products can be treated further.…”

Section: Reductive Cage-opening Process With Concomitant Metalation Omentioning

confidence: 99%

Recent Advances in the Chemistry of Metallacarboranes

Hosmane

Maguire

2003

Eur J Inorg Chem

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Most carborane derivatives of the icosahedral (C2B10) or small cage (C2B4) systems are formed by varying the groups on the cage carbon atoms. This is usually accomplished in the original carborane synthesis by treating substituted acetylenes with either the decaborane(14) or pentaborane(9) precursors to give directly carboranes that have adjacent carbon atoms in the cage (“carbon atoms adjacent”). The larger cages are obtained as closo‐icosahedra, while the small‐cage C2B4 carboranes have nido structures as well as a cage geometry in which the carbon atoms are separated by a boron atom. Although these “carbon atoms apart” or nido‐2,4‐(CR)2B4H6 carboranes are thermodynamically more stable and are more symmetric than the “carbon atoms adjacent” isomers, they have not been as well studied, mainly because they must be synthesized from their “carbon atoms adjacent” analogues through a sequential series of oxidative cage‐closure/reductive cage‐opening reactions. We have concentrated much of our recent research on the reactivity patterns of C(cage)‐appended alkyl‐ and silylamido, alkyloxo, alkylphosphido, and alkylthio derivatives of the “carbon atoms apart” carboranes. We have also sought to develop a safe, bench‐scale preparation of small‐cage carboranes that does not require isolating and handling dangerous and toxic carborane precursors such as pentaborane(9). This microreview discusses the latest developments towards such a process and the subsequent reaction chemistry of the “carbon atoms apart” carboranes. ((© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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“…In contrast, little is known of the smallest members of the metallacarborane family, for example, 6‐vertex closo ‐MC 2 B 3 polyhedra. The first such species were prepared in the 1970s2, 3 by thermal insertion of metal reagents into closo ‐1,5‐C 2 B 3 H 5 , a relatively inaccessible small carborane. To date, fewer than half a dozen 6‐vertex closo ‐metallacarboranes have been reported,2–4 and just one crystal structure of a closo ‐MC 2 B 3 system is available 3.…”

Section: Methodsmentioning

confidence: 99%

“…The first such species were prepared in the 1970s2, 3 by thermal insertion of metal reagents into closo ‐1,5‐C 2 B 3 H 5 , a relatively inaccessible small carborane. To date, fewer than half a dozen 6‐vertex closo ‐metallacarboranes have been reported,2–4 and just one crystal structure of a closo ‐MC 2 B 3 system is available 3. In principle, such clusters should be accessible by the oxidation of nido ‐LMC 2 B 3 H 5 2− open‐cage dianions having 16 skeletal electrons, generating neutral 14‐electron closo ‐LMC 2 B 3 H 5 species as predicted from simple electron‐counting arguments (Wade's rules) 5.…”

Section: Methodsmentioning

confidence: 99%

nido↔closo Interconversion of Six-Vertex Metallacarboranes: Access to CoC2B3 and CoC2B4 Clusters with Nonadjacent Carbon Atoms

2001

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Metallacarborane chemistry has been well developed for 12-vertex (icosahedral) and 7-vertex (pentagonal bipyramidal) clusters and, to a lesser extent, for other systems having 8 to 14 vertices. [1] In contrast, little is known of the smallest members of the metallacarborane family, for example, 6-vertex closo-MC 2 B 3 polyhedra. The first such species were prepared in the 1970s [2, 3] by thermal insertion of metal reagents into closo-1,5-C 2 B 3 H 5 , a relatively inaccessible small carborane. To date, fewer than half a dozen 6-vertex closometallacarboranes have been reported, [2±4] and just one crystal structure of a closo-MC 2 B 3 system is available. [3] In principle, such clusters should be accessible by the oxidation of nido-LMC 2 B 3 H 5 2À open-cage dianions having 16 skeletal electrons, generating neutral 14-electron closo-LMC 2 B 3 H 5 species as predicted from simple electron-counting arguments (Wades rules). [5] However, no such conversion has been reported experimentally, and earlier attempts to do this in our laboratory were unsuccessful; our experience has been that oxidants sufficiently strong to remove two electrons tend to degrade the cage structure.It seemed possible that this problem might be circumvented by modifying the cluster to make it easier to oxidize. Here we report an application of this approach, in which a tribrominated nido-1,2,3-MC 2 B 3 cage with adjacent carbon atoms undergoes oxidative closure to form the desired closo system. This product in turn can be converted into 7-vertex closo-and 6-vertex nido-metallacarboranes having nonadjacent carbon atoms, families that have heretofore been difficult to access.Deprotonation of the 4,6-dichloro-or dibromo-nido-cobaltacarboranes [6] 2 a or 2 b (Scheme 1) with sodium hydride in THF, followed by addition of 2-bromo-2-nitropropane and Scheme 1. Synthesis of 3 a and 3 b as well as the thermal rearrangement of 3 a to form a mixture of isomers 4 a and 4 a'.

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Direct insertion of transition metals into polyhedral carboranes. Structurally novel mono-, di-, and trimetallic small cage systems

Cited by 65 publications

References 2 publications

Structures of metalloboron clusters. X-ray studies of octahedral (.eta.5-C5H5)3Co3B3H5 and capped octahedral (.eta.5-C5H5)3Co3B4H4, a boron analog of tricobalt carbon clusters

Structures of metalloboron clusters. X-ray studies of octahedral (.eta.5-C5H5)3Co3B3H5 and capped octahedral (.eta.5-C5H5)3Co3B4H4, a boron analog of tricobalt carbon clusters

Recent Advances in the Chemistry of Metallacarboranes

nido↔closo Interconversion of Six-Vertex Metallacarboranes: Access to CoC2B3 and CoC2B4 Clusters with Nonadjacent Carbon Atoms

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