When is a vertex not a vertex? An analysis of the structures of [MB10H12] metallaboranes

Macgregor, Stuart A.; Wynd, Andrew J.; Moulden, N.; Gould, Robert O.; Taylor, Paul; Yellowlees, Lesley J.; Welch, Alan J.

doi:10.1039/dt9910003317

Cited by 13 publications

(12 citation statements)

References 14 publications

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“…This phenomenon is now quite common for metallaborane clusters containing the L 2 M moiety (where M = Pt or Pd). Examples of “anomalous” electron counts in other platina- and palladaboranes include [5,6-Me 2 -7,7-(PEt 3 ) 2 -7,5,6-PtC 2 B 4 H 4 ] and [7,7-(PMe 2 Ph) 2 -7-PtB 10 H 12 ], [(PPh 3 ) 2 (CO)Os(PhMe 2 P)ClHPtB 5 H 7 ], and [{PhCH 2 NMe 3 } 2 (B 10 H 12 ) 2 Pd]·MeCN and related systems, and attempts have been made to account for the discrepancies in the latter systems using molecular orbital calculations . Again this phenomenon in [7,7-(PMe 2 Ph) 2 -7-PtB 10 H 12 ] may be ascribed to be due to the Pt moiety functioning as a two orbital two electron donor and adopting effectively a square-planar configuration although contributions from higher valence Pt(IV) states have been proposed in these systems. , …”

Section: Resultsmentioning

confidence: 99%

Metallaborane Heteroatom Incorporation Reactions: Metallacarboranes, Metallathiaboranes, and an Iridaazaborane from Iridanonaborane Precursors

1996

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Formation of metallaheteroboranes by insertion of heteroatoms into an existing metallaborane cluster, rather than adding the metal moiety to the heteroborane which is normally the case, has been achieved in the cases of carbon, nitrogen, and sulfur to produce nine-, ten-, and eleven-vertex metallaheteroborane clusters. Thus passage of acetylene through refluxing p-xylene solutions of either arachno-[(PMe3)2(CO)HIrB8H12] (1a) or nido-[(PMe3)2(CO)IrB8H11] (2a) afforded the 11-vertex cluster nido-[9,9,9-(PMe3)2(CO)-9,7,8-IrC2B8H11] (5a) in up to 44% yield. With the cage substituted species arachno-[(PMe3)2(CO)HIrB8H11Cl] (1b), the analogous product is nido-[5-Cl-9,9,9-(PMe3)2(CO)-9,7,8-IrC2B8H10] (5b) and the position of the Cl substituent in the product suggests that the acetylene moiety attacks across the open face of the intermediate nido-iridanonaborane species and that cage rearrangement does not occur during the course of the reaction. Similarly, reaction of 1a with H2S under identical conditions results in the formation nido-[2,2,2-(PMe3)2H-2,6-IrSB8H10] (9a), closo-[2,2,2-(PMe3)2H-2,1-IrSB8H8] (10), and nido-[(PMe3)2HIrS2B8H8] (11a) in overall yields of 13%, 7%, and 20%, respectively. Additionally, refluxing a solution of 1a and anhydrous hydrazine in xylene afforded a 10% yield of the novel iridaazanonaborane nido-[2,2,2-(PMe3)3-2,9-IrNB7H9] (12). The compound is the first metallaazanonaborane cluster to be described, and its formation indicates that methods similar to those used to generate azaboranes may be used on metallaboranes to generate metallazaboranes. In addition to characterization by a combination of 1H, 31P, and 11B NMR and IR spectroscopy and high-resolution mass spectrometry, single-crystal X-ray diffraction studies were carried out on compounds 5a, 9a, 10, and 12.

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Section: Resultsmentioning

confidence: 99%

Metallaborane Heteroatom Incorporation Reactions: Metallacarboranes, Metallathiaboranes, and an Iridaazaborane from Iridanonaborane Precursors

1996

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“…As a result, these two metallaboranes of two different borane-anion charges and OS M have similar shapes that can only be distinguished by careful evaluation of distances or via computerized comparisons [94]. The latter reveal bonding situations in between these two extremes, depending on how many orbitals the M atom can supply [94]. If one (e.g., Au + ), it yields the 2− anion, if three (e.g., Co 3+ ), it yields the 4− anion.…”

Section: Metallaboranesmentioning

confidence: 99%

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Karen

McArdle

Takats

2014

Pure and Applied Chemistry

111

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A generic definition of oxidation state (OS) is formulated: "The OS of a bonded atom equals its charge after ionic approximation". In the ionic approximation, the atom that contributes more to the bonding molecular orbital (MO) becomes negative. This sign can also be estimated by comparing Allen electronegativities of the two bonded atoms, but this simplification carries an exception when the more electronegative atom is bonded as a Lewis acid. Two principal algorithms are outlined for OS determination of an atom in a compound; one based on composition, the other on topology. Both provide the same generic OS because both the ionic approximation and structural formula obey rules of stable electron configurations. A sufficiently simple empirical formula yields OS via the algorithm of direct ionic approximation (DIA) by these rules. The topological algorithm works on a Lewis formula (for a molecule) or a bond graph (for an extended solid) and has two variants. One assigns bonding electrons to more electronegative bond partners, the other sums an atom's formal charge with bond orders (or bond valences) of sign defined by the ionic approximation of each particular bond at the atom. A glossary of terms and auxiliary rules needed for determination of OS are provided, illustrated with examples, and the origins of ambiguous OS values are pointed out. An electrochemical OS is suggested with a nominal value equal to the average OS for atoms of the same element in a moiety that is charged or otherwise electrochemically relevant.

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“…Distances and angles within the [PhCH2NMe3] ÷ cation are quite normal (e.g. Mitchell & Welch, 1987;Wynd & Welch, 1989;Macgregor, Yellowlees & Welch, 1990).…”

Section: B(c)--b(d)--b(e)mentioning

confidence: 99%

“…The precise structures of metallaboranes of the general family MB,oH12 are of current interest because the {B~oH~2} ligand could formally be present in such species as either the nido fragment {BIoHI2} 2-or the arachno fragment {BIoHI2} 4-. The structural differences between these are subtle (the pattern of connectivities is exactly the same), and only recently have they really been successfully delineated via application of the 'root-mean-square misfit' technique (Wynd, 1988;Wynd, Welch & Parish, 1990;Macgregor, Yellowlees & Welch, 1990).…”

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confidence: 99%