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Inthe context of our longstanding interest in subvalent boroncompounds, we targeted the liberation of a carbene-stabilized borylenefrom a suitable organoboron precursor. For this purpose, we tested7-borabicyclo[2.2.1]hepta-2,5-dienes (or 7-boranorbornadienes in short)obtained from facile [4 + 2] cycloaddition of boroles and alkynes.By formation of a Lewis adduct with an N-heterocyclic carbene (NHC),we intended to block previously reported pericyclic reactions leadingto undesired ring expansion and achieve a cheletropic eliminationof the borylene species instead. Our results presented herein indicatethat coordination of the NHC to 7-boranorbornadienes indeed weakensthe bridgehead boron–carbon bonds. However, ring expansionto form borepine-NHC Lewis adducts remains the favorable reactionpathway. This process is independent of excessive NHC in the reactionmixture, which precludes participation of a free borylene species.As an alternative, an intramolecular mechanism driven mainly by molecularstrain and steric factors is most plausible. Our investigations arebased on spectroscopic measurements and single-crystal X-ray diffractionanalyses. [ABSTRACT FROM AUTHOR]

Heterobimetallic [3]trochrocenophanes with PdCl2andPtCl2bridges were prepared in reasonable yields. The PdCl2species possess, like their Pt analogues, poor solubilitybut can be made more soluble by ligand substitution. By reaction ofPd-bridged [3]trochrocenophanes with MeLi, both Cl atoms can be substitutedby a Me group. Likewise, reaction of Pt-bridged complexes with LiCCPhleads to the expected disubstituted compound. Herein we present thesynthesis of MCl2- and MR2-bridged (M = Pd,Pt; R = Me, CCPh) [3]trochrocenophanes, as well as some solid-statestructures of these [3]trochrocenophanes. [ABSTRACT FROM AUTHOR]

1,2-Dichloro-1,1,2,2-tetra-tert-butyldistannanereacts with 2 equiv of sodium cyclopentadienide to give a bis(cyclopentadienyl)distannane.Subsequent dilithiation with lithium diisopropylamide and reactionswith suitable metal halides yield [(C5H4SntBu2)2MCl2] (M = Ti, Zr,Hf). The group 4 ansa-metallocenes have all beenfully characterized by means of multinuclear NMR spectroscopy, elementalanalysis, and X-ray diffraction. [ABSTRACT FROM AUTHOR]

Preparation of a novel conjugated tetraorganoborate ispresentedin a facile two-step procedure. Successful utilization as a halideabstraction reagent is demonstrated in a metathesis reaction withthe platinum(II) boryl complex [(Cy3P)2Pt(Br)(BC4Ph4)], which was obtained by oxidative additionof 1-bromo-2,3,4,5-tetraphenylborole to a platinum(0) species. Thenovel compounds were investigated by means of spectroscopic and X-raydiffraction techniques. [ABSTRACT FROM AUTHOR]

A number of cationic and neutral η3-furfurylcomplexesof palladium and platinum were prepared, including one with a ligandderived from fructose, 5-chloromethylfurfural. The complexes werestudied by variable-temperature and heteronuclear correlation NMRspectroscopy, as well as single-crystal X-ray crystallography. Analogousη3-thienyl complexes could be prepared and detectedin solution by NMR, but could not be isolated due to facile decomposition. [ABSTRACT FROM AUTHOR]

A reactivity study on a series of platinum boryl complexeswasperformed. The first stable base adducts of cationic haloboryl complexesof the form trans-[Pt{B(Br)(NMe2)}(NCMe)(PCy3)2]쇪 isolated and fully characterized.The dianion [B12Cl12]2–wasintroduced as a weakly coordinating anion to complex chemistry forminga A2X salt. Through the reaction of trans-[Pt{B(Br)(tBu)}Br(PCy3)2]with BBr2tBu, the first highly solubledinuclear platinum boryl complex, [Pt{B(Br)(tBu)}(μ-Br)(PCy3)]2, could be synthesized with concomitant buildupof the corresponding phosphine-borane adduct. In contrast to thisobservation, reaction of trans-[Pt{B(Br)(Mes)}Br(PCy3)2] with BBr3leads to the formationof the cationic borylene complex trans-[Pt(BMes)Br(PCy3)2] abstraction of the bromo ligandbound mutually transto the boryl ligand in the precursorand concomitant buildup of [BBr4]−. Reactionof [Pt(PCy3)2] with BCl3and subsequentabstraction of the platinum-bound chloro ligand enabled the structuralcharacterization of trans-[Pt(BCl2)(PCy3)2], which is isoelectronic with themetal-only Lewis pair trans-[Pt(BeCl2)(PCy3)2]. The bonding situation in both systems wasinvestigated in detail using quantum chemical calculations. A T-shapedcationic complex, trans-[Pt{B(Br)(Fc)}(PiPr3)2], and its precursor trans-[Pt{B(Br)(Fc)}Br(PiPr3)2], both with reduced steric bulk at the phosphine ligandscompared with their PCy3derivatives, were fully characterized. [ABSTRACT FROM AUTHOR]

New borylene-containing metal-onlyLewis pairs based on group 6metals and ruthenium are prepared by a partially reversible borylenetransfer from group 6 borylene complexes [M{BN(SiMe3)2}(CO)5] (M = Mo, W). The complexescontain strong Ru → Mo/W dative interactions. As in a previousreport on related compounds, redissolving these complexes resultedin reversion back to the precursors, enabled by a sacrificial CO donor.It was observed that this reversion process becomes less selectiveas the group 6 metal becomes heavier, leading to greater amounts ofunidentified byproducts as the group is descended. [ABSTRACT FROM AUTHOR]

Five-membered heterocyclic analogues of the well-known η3-allyl and η3-benzyl ligands, e.g., η3-thienyl and η3-furfuryl, have been proposed as catalytic intermediates, yet are poorly understood and have never been structurally confirmed. Herein we characterize an η3-furfuryl complex by multinuclear NMR spectroscopy and crystallography and offer a computational survey of allyl and allyl-like ligands. Crystallographically and computationally, we show that the η3-furfuryl ligand may bind more strongly than corresponding η3-benzyl ligands and is plausible as a catalytic intermediate. Five-membered heterocyclic analogues of the well-known η3-allyl and η3-benzyl ligands, e.g., η3-thienyl and η3-furfuryl, have been proposed as catalytic intermediates, yet are poorly understood and have never been structurally confirmed. Herein we characterize an η3-furfuryl complex by multinuclear NMR spectroscopy and crystallography and offer a computational survey of allyl and allyl-like ligands. Crystallographically and computationally, we show that the η3-furfuryl ligand may bind more strongly than corresponding η3-benzyl ligands and is plausible as a catalytic intermediate. [ABSTRACT FROM AUTHOR]