A series of new dispiro[fluorene-9',6,9'',12-indeno[1,2b]fluorenes] (DSF-IFs) has been synthesised. These new building blocks for blue-light-emitting devices and electroactive polymers combine indenofluorene (IF) and spirobifluorene (SBF) properties. We report here our synthetic investigations towards these new structures and their thermal, structural, photophysical and electrochemical properties. These properties have been compared to those of IF and SBF. We also report the anodic oxidation of DSF-IFs that leads to the formation of non-soluble transparent three-dimensional polymers. The structural and electrochemical behaviour of these polymers has been studied. The first application of these building blocks as new blue-light-emitting materials in organic light-emitting diodes (OLED) is also reported.

An efficient synthetic route to 2- and 2,7-substituted pyrenes is described. The regiospecific direct C-H borylation of pyrene with an iridium-based catalyst, prepared in situ by the reaction of [{Ir(μ-OMe)cod}(2)] (cod = 1,5-cyclooctadiene) with 4,4'-di-tert-butyl-2,2'-bipyridine, gives 2,7-bis(Bpin)pyrene (1) and 2-(Bpin)pyrene (2, pin = OCMe(2)CMe(2)O). From 1, by simple derivatization strategies, we synthesized 2,7-bis(R)-pyrenes with R = BF(3)K (3), Br (4), OH (5), B(OH)(2) (6), and OTf (7). Using these nominally nucleophilic and electrophilic derivatives as coupling partners in Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig cross-coupling reactions, we obtained 2,7-bis(R)-pyrenes with R = (4-CO(2)C(8)H(17))C(6)H(4) (8), Ph (9), C≡CPh (10), C≡C[{4-B(Mes)(2)}C(6)H(4)] (11), C≡CTMS (12), C≡C[(4-NMe(2))C(6)H(4)] (14), C≡CH (15), N(Ph)[(4-OMe)C(6)H(4)] (16), and R = OTf, R' = C≡CTMS (13). Lithiation of 4, followed by reaction with CO(2), yielded pyrene-2,7-dicarboxylic acid (17), whilst borylation of 2-tBu-pyrene gave 2-tBu-7-Bpin-pyrene (18) selectively. By similar routes (including Negishi cross-coupling reactions), monosubstituted 2-R-pyrenes with R = BF(3)K (19), Br (20), OH (21), B(OH)(2) (22), [4-B(Mes)(2)]C(6)H(4) (23), B(Mes)(2) (24), OTf (25), C≡CPh (26), C≡CTMS (27), (4-CO(2)Me)C(6)H(4) (28), C≡CH (29), C(3)H(6)CO(2)Me (30), OC(3)H(6)CO(2)Me (31), C(3)H(6)CO(2)H (32), OC(3)H(6)CO(2)H (33), and O(CH(2))(12)Br (34) were obtained from 2. These derivatives are of synthetic and photophysical interest because they contain donor, acceptor, and conjugated substituents. The crystal structures of compounds 4, 5, 7, 12, 18, 19, 21, 23, 26, and 28-31 have also been obtained from single-crystal X-ray diffraction data, revealing a diversity of packing modes, which are described in the Supporting Information. A detailed discussion of the structures of 1 and 2, their polymorphs, solvates, and co-crystals is reported separately.

The Ir(III) fragment {Ir(PCy(3))(2)(H)(2)}(+) has been used to probe the role of the metal centre in the catalytic dehydrocoupling of H(3)B⋅NMe(2)H (A) to ultimately give dimeric aminoborane [H(2)BNMe(2)](2) (D). Addition of A to [Ir(PCy(3))(2)(H)(2)(H(2))(2)][BAr(F)(4)] (1; Ar(F) = (C(6)H(3)(CF(3))(2)), gives the amine-borane complex [Ir(PCy(3))(2)(H)(2)(H(3)B⋅NMe(2)H)][BAr(F)(4)] (2 a), which slowly dehydrogenates to afford the aminoborane complex [Ir(PCy(3))(2)(H)(2)(H(2)B-NMe(2))][BAr(F)(4)] (3). DFT calculations have been used to probe the mechanism of dehydrogenation and show a pathway featuring sequential BH activation/H(2) loss/NH activation. Addition of D to 1 results in retrodimerisation of D to afford 3. DFT calculations indicate that this involves metal trapping of the monomer-dimer equilibrium, 2 H(2)BNMe(2) ⇌ [H(2)BNMe(2)](2). Ruthenium and rhodium analogues also promote this reaction. Addition of MeCN to 3 affords [Ir(PCy(3))(2)(H)(2)(NCMe)(2)][BAr(F)(4)] (6) liberating H(2)B-NMe(2) (B), which then dimerises to give D. This is shown to be a second-order process. It also allows on- and off-metal coupling processes to be probed. Addition of MeCN to 3 followed by A gives D with no amine-borane intermediates observed. Addition of A to 3 results in the formation of significant amounts of oligomeric H(3)B⋅NMe(2)BH(2)⋅NMe(2)H (C), which ultimately was converted to D. These results indicate that the metal is involved in both the dehydrogenation of A, to give B, and the oligomerisation reaction to afford C. A mechanism is suggested for this latter process. The reactivity of oligomer C with the Ir complexes is also reported. Addition of excess C to 1 promotes its transformation into D, with 3 observed as the final organometallic product, suggesting a B-N bond cleavage mechanism. Complex 6 does not react with C, but in combination with B oligomer C is consumed to eventually give D, suggesting an additional role for free aminoborane in the formation of D from C.

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There have been a number of approaches developed for the catalyzed dehydrogenation of amine-boranes as potential dihydrogen sources for hydrogen storage applications in recent years. Key advances in this area have been recently made thanks to catalytic and stoichiometric studies. In this Minireview, the fate of amine-boranes upon coordination to a metal center is discussed with a particular emphasis on B-H activation pathways. We focus on the few cases in which coordination of the resulting dehydrogenated product could be achieved, which includes the coordination of aminoborane, the simplest unit resulting from dihydrogen release of ammonia-borane.

Starting from RuHCl(H2)(PCy3)2, a terminal ruthenium mesitylborylene complex was obtained via double B-H bond activation of mesitylborane and concomitant release of dihydrogen, such a process being remarkably reversible.

The new borane complex RuH2(η2:η2-H2BMes)(PCy3)2 (2) can be isolated in good yield by reaction of H2BMes with RuH2(η2-H2)2(PCy3)2 (1) or alternatively, by reacting the chloro dihydrogen complex RuHCl(η2-H2)(PCy3)2 (3) with lithium mesitylborohydride. 2 has been fully characterized by NMR and X-ray diffraction crystallography. A DFT/B3PW91 analysis shows that in 2, the H2BMes group is coordinated to the {RuH2(PCy3)2} fragment through two geminal σ-B−H bonds. This coordination involves σ-donation to the ruthenium and π back-bonding from the ruthenium to the vacant p orbital of the boron. These two geminal σ-B−H bonds are responsible for the short Ru−B distance (1.938 (4) Å by X-ray, 1.957 Å by DFT).

Hydrogen, the simplest element in the periodic table, plays a tremendous role in organic and inorganic chemistry. For years, it was inconceivable that dihydrogen could be bound to a metal center without breaking the H-H bond. Thus, oxidative addition of H(2) was universally recognized as a key elementary step in hydrogenation processes. In 1984, Kubas and co-workers reported the first example of a complex in which dihydrogen was coordinated to a metal center without breaking of the H-H bond. This opened a new area in coordination chemistry: sigma-complexes were born, complementing the well-known Werner-type family of complexes. Since then, hundreds of stable dihydrogen complexes have been isolated, and their properties have been investigated in detail. By comparison, very little information is available for the analogous class of sigma-borane complexes, in which sigma-H-B bonds are complexed to a metal (in the manner of H-H bonds in sigma-dihydrogen complexes). Since the first example published in 1996 by Hartwig and co-workers, very few sigma-borane complexes have been isolated. Scientists have maintained a continuous interest in catalytic hydrogenation reactions. Almost a century ago, in 1912, Paul Sabatier, the father of the hydrogenation process, received the Nobel prize, and the selection of Noyori and Knowles in 2001 for their studies on enantioselective catalyzed hydrogenations amply demonstrates the ongoing importance of the field. Moreover, during the past decade, dihydrogen has attracted considerable attention as a possible "fuel of the future". This endeavor has furthered interest in sigma-borane complexes, as more and more evidence links their chemistry to that of amine-borane derivatives. Indeed, ammonia-borane (NH(3)BH(3)) is attracting significant interest for hydrogen storage applications. One of the main limitations is the lack of reversibility associated with the production of dehydrogenated (BNH)(x) materials. Of major importance will be a better understanding of the coordination of H(2) to a metal center, and more generally of the coordination of H-E bonds (E = B, C), which are likely to play a critical role in the reversible dehydrogenation process. In this Account, we review our recent results in the field of dihydrogen and borane activation, with a specific focus on the problem of reversible dehydrogenation pathways. We concentrate on the chemistry of ruthenium complexes incorporating two sigma-ligands: either two dihydrogen or two sigma-B-H bonds. We describe our synthetic strategies to prepare such unusual structures. Their characterization is discussed in detail, highlighting the importance of an experimental and theoretical approach (NMR, structural, and theoretical studies). Some catalytic applications are discussed and put into context, and their reactivity toward reversible hydrogen release is detailed.