A Stable Neutral Diborene Containing a BB Double Bond

Wang, Yu‐Zhong; Quillian, Brandon; Wei, Pingrong; Wannere, Chaitanya S.; Xie, Yaoming; King, R. B.; Schaefer, Henry F.; Schleyer, Paul von Ragué; Robinson, Gregory H.

doi:10.1021/ja075932i

Cited by 520 publications

(419 citation statements)

References 23 publications

(39 reference statements)

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“…This can be attributed to the decrease in the length of the boron-boron bond (3: 1.602(2) Å) which falls in the normal range of B=B double bonds in base-stabilized diborenes. [15][16][17][18][19][20][21] As a result of the increase in bond order in the ansa bridge, the Ct− To elucidate the effect of both the cis-configuration and the molecular strain on the physical properties of diborene 3, we carried out a series of analytical and computational studies. The unstrained trans-diborenes of the general formula [(L)RB=BR(L)] (L = Lewis base) were used as a reference to which the properties and reactivity of the cyclic diborene 3 were compared.…”

Section: Abstract: Unsaturated Bridges That Link the Two Cyclopentadimentioning

confidence: 99%

Dibora[2]ferrocenophane: A Carbene‐Stabilized Diborene in a Strained cis‐Configuration

et al. 2016

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Metallocenes with bridged cyclopentadienyl ligands, commonly named ansa metallocenes or metallocenophanes, have emerged as a class of organometallic compounds with an exceptionally wide and diverse range of applications.[1] Among other applications, ansa metallocenes are employed as catalyst precursors in the industrial production of polyolefins [2] and as monomers for ring-opening polymerization to form functional metallopolymers.[3] Their versatility and usefulness stems largely from the fact that their physical properties, and hence reactivity, can be tuned through structural modifications of the ligand framework. For instance, unsaturated two-atom bridges have been developed to increase the configurational rigidity [4] as well as the molecular strain of metallocenophanes, but also to add additional functionality to the metallocene fragment. In part due to difficulties encountered in their synthesis, these types of bridges are relatively rare and only a handful of these have been successfully incorporated into the ferrocene structure, as shown in Figure 1 (I-V). The first examples involved bridging aromatic rings, such as an ortho-phenylene (I), [5,6] a cyclobutadiene cobalt (II) [6] and a ruthenacyclopentadiene fragment (III). [7] Whereas the focus of the initial studies was on synthesis and structural features, the vinylene-bridged dicarba[2]ferrocenophanes IV and V have been developed as candidates for ring-opening metathesis polymerization (ROMP) to produce conjugated metal-containing polymers. [8][9][10] As shown by the groups of Tilley and Manners, such strained ferrocenophanes can indeed undergo ROMP with Schrock-and Grubbs-type catalysts to form conjugated metallopolymers. [9,10] Although homo-and heteronuclear multiple bonding is common for other p-block elements, especially the second-period elements, [11] unsaturated ansa bridges in metallocenophanes are to date restricted to carbon. By capitalizing on the isoelectronic relationship between Lewis base-stabilized diborenes, [(L)RB=BR(L)] (L = Lewis base), [12,13] and olefins, R2C=CR2, we sought to prepare the first ansa metallocene with a heteroatomcontaining multiple bond in the bridge. Herein, we describe the successful synthesis of a strained dibora[2]ferrocenophane (VI), in which the bridging diborene moiety is forced to adopt a cis rather than the prevailing trans configuration. The effects of changing the regiochemistry, as well as the interrelationship between the strain and properties of the diborene are addressed.[a]Prof.

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Section: Abstract: Unsaturated Bridges That Link the Two Cyclopentadimentioning

confidence: 99%

Dibora[2]ferrocenophane: A Carbene‐Stabilized Diborene in a Strained cis‐Configuration

et al. 2016

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“…The system composed of trivalent lanthanide precursors LnZ3 (Z represents a monoanionic ligand) and KC8 developed by Evans proved successful in reducing dinitrogen to form stable lanthanide dinitrogen complexes with the general formula (Z2Ln)2(- 2 : 2 -N2) (Evans et al, 2005 et al, 2013a). The strategy of using KC8 as a reductant was also employed in main group chemistry to obtain structurally fascinating and fundamentally important molecules such as Wang et al, 2007) and LSi=SiL (Wang et al, 2008) …”

Section: Reaction Conditions For Reduction Chemistrymentioning

confidence: 99%

Rare Earth Arene-Bridged Complexes Obtained by Reduction of Organometallic Precursors

Huang

Diaconescu

2014

Including Actinides

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Rare earth chemistry has witnessed remarkable advances in recent years. In particular, ancillary ligands other than cyclopentadienyl derivatives have been introduced to the organometallic chemistry and their complexes exhibit distinct reactivity and properties compared to the metallocene or half-sandwiched analogues. The present chapter reviews arene-bridged rare earth complexes with an emphasis on those compounds obtained by reduction reactions. A particular emphasis is placed on rare earth complexes supported by 1,1′-ferrocenediyl diamides since they show the most diverse chemistry with arenes: fused arenes, such as naphthalene and anthracene, formed inverse-sandwiched complexes, in which the arene is dianionic; weakly conjugated arenes, such as biphenyl, p-terphenyl, and 1,3,5-triphenylbenzene, were unexpectedly reduced by four electrons and led to 6-carbon, 10- electron aromatic systems; on the contrary, (E)-stilbene, which has a carbon-carbon double bond between the two phenyl rings, could only be reduced by two electrons, which were located on the carbon-carbon double bond instead of the phenyl rings.

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“…First isolated by Robinson and co-workers, NHC-supported 1,2-dihydrodiborenes, (IDip)2B2H2 (1) and (IMes)2B2H2 (2) (IDip = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), were obtained from the reduction of (IDip)BBr3 with KC8, alongside the corresponding tetrahydrodiboranes(6), (IDip)2B2H4 and (IMes)2B2H4, both resulting from hydrogen atom abstraction from the reaction solvent by radical intermediates (Scheme 1). [21] There has, however, been no report of a rational selective synthetic route toward 1,2-dihydrodiborenes. In light of the facile hydrogenation of digermynes [10] attempts were made to hydrogenate diboryne 3a, (IDip)2B2, [22] in order to access the corresponding 1,2-dihydrodiborene, 1 (Scheme 2a).…”

mentioning

confidence: 99%

“…The boron-bound hydrides were located in the difference Fourier map and freely refined. Like its NHC analogue, 1, [21] compound 7 presents a planar (C1B1H1)2 core with the hydrides in trans-conformation but, unlike 1, the structure is C2-symmetric. 0.9 Å longer than that of the parent diboracumulene, 5, [24] indicating a substantial reduction in π-backbonding.…”

mentioning

confidence: 99%

“…S16 for the crystal structure of 4b), [18] underwent slow hydrogenation to (SIDep)2B2H2 (6) at 80 o C over a period of two days (Scheme 2b), as evidenced by the disappearance of the diboryne 11 B NMR resonance at 55.9 ppm and the appearance of a broad resonance at 28.1 ppm, similar to that observed for 1. [21] The 1 H NMR BH resonance at ca. 2.6 ppm was found to overlap with the ethyl CH2 multiplet and was later confirmed by 2 H NMR spectroscopy in the deuterated species, (SIDep)2B2D2, obtained from the reaction of 4b with ultrapure D2.…”

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confidence: 99%

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Uncatalyzed Hydrogenation of First‐Row Main Group Multiple Bonds

Arrowsmith

Böhnke

Braunschweig

et al. 2016

Chemistry A European J

104

109

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Room temperature hydrogenation of an and a CAAC-supported diboracumulene 3,5, Since the pioneering work of Sabatier over a century ago [1] catalytic hydrogenation has become the most used reaction type in industrial chemical synthesis [2] and still constitutes one of the most active research areas in chemistry. While the vast majority of industrial hydrogenation processes are based on well-established heterogeneous late transition metal catalysts (Pt, Pt, Rh, Ru, Ni) [2] the last decade has seen a revival of the field with the advent of metal-free frustrated Lewis pair catalysts capable of activating H2 [4] and transfer hydrogenation [5] for the reduction of polar multiple bonds.

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A Stable Neutral Diborene Containing a BB Double Bond

Cited by 520 publications

References 23 publications

Dibora[2]ferrocenophane: A Carbene‐Stabilized Diborene in a Strained cis‐Configuration

Dibora[2]ferrocenophane: A Carbene‐Stabilized Diborene in a Strained cis‐Configuration

Rare Earth Arene-Bridged Complexes Obtained by Reduction of Organometallic Precursors

Uncatalyzed Hydrogenation of First‐Row Main Group Multiple Bonds

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