Reactivity of a dihydroboron species: synthesis of a hydroborenium complex and an expedient entry into stable thioxo- and selenoxo-boranes

Abstract

The reaction of a recently synthesized dihydroboron species complexed with bis(phosphinimino)amide, LBH2 (), (L = [N(Ph2PN(2,4,6-Me3C6H2))2](-)) with 3 equivalents of BH2Cl·SMe2 or one equivalent of BCl3 affords the first stable monohydridoborenium ion, [LBH](+)[HBCl3](-) () that is stable without a weakly coordinating bulky anion. Compound can also be prepared directly by refluxing LH with 3 equivalents of BH2Cl·SMe2. Interestingly, reaction of LBH2 () with elemental sulfur and selenium involves oxidative addition of S and Se into B-H bonds and subsequent release of H2S (or H2Se) from the intermediate LB(SH)2 (or LB(SeH)2) species forming stable compounds with terminal boron-chalcogen double bonds LB[double bond, length as m-dash]S () and LB[double bond, length as m-dash]Se (). The electronic structures of compounds , and were elucidated by high resolution mass spectrometry, multi-nuclear NMR and single crystal X-ray diffraction studies. Ab initio calculations on are in excellent agreement with its experimental structure and clearly support the existence of the boron-sulfur double bond.

Electronically Unsaturated Three‐Coordinate Aluminum Hydride and Organoaluminum Cations

“…The single crystal X‐ray structural analysis of 4 revealed a three‐coordinate arrangement around Al atom, which in turn is a part of N 3 P 2 Al six‐membered puckered ring (Figure ) . Two terminal N atoms of the ligand and a Me group are bonded to the Al atom in a trigonal planar arrangement (see the Supporting Information; detailed structural description of 4 and Table S1 for crystallographic data).…”

Fine‐Tuning of Lewis Acidity: The Case of Borenium Hydride Complexes Derived from Bis(phosphinimino)amide Boron Precursors

“…The presence of as uitable strong donor ligand can facilitatet he stabilizationo ft he positivec harge on the boron atom. The [(BODI-PY)BH] + [B(C 6 F 5 ) 4 ] À complex (A)b ased on the dipyrromethane ligandw as the first structurally characterizedm onocationic borenium hydride complex [14] followed by the dihydrido borenium cation [15] [(Ph 3 P) 2 CBH 2 ] + [HB(C 6 F 5 ) 3 ] À (B), the bis(phosphinimino)amide-supported borenium hydride complex (C), [16] and more recently ad icationic hydrido boron complex stabilized by carbodicarbene(D). [17] In light of the scarcity of well-characterized borenium hydride speciesi nthe literature, we werei nterested in the synthesiso fn ew derivatives of this type and exploring their Lewis acid behavior.T herefore, in the present work we report the synthesis and characterization of as eries of boreniumh ydride cations.O ur approachr elies on i) Lewis acid mediated hydride abstraction and ii)ani ndirect approach that involves hydridechloridee xchange followed by chloride abstraction.I nb oth the approaches the strong donor bis(phosphinimino)amide ligand plays av ery important role in supportingt he three-coordinated cationic boronc enter.…”

“…The presence of a suitable strong donor ligand can facilitate the stabilization of the positive charge on the boron atom. The [(BODIPY)BH] + [B(C 6 F 5 ) 4 ] − complex ( A ) based on the dipyrromethane ligand was the first structurally characterized monocationic borenium hydride complex followed by the dihydrido borenium cation [(Ph 3 P) 2 CBH 2 ] + [HB(C 6 F 5 ) 3 ] − ( B ), the bis(phosphinimino)amide‐supported borenium hydride complex ( C ), and more recently a dicationic hydrido boron complex stabilized by carbodicarbene ( D ) …”

Cycloosmathioborane Compounds: Other Manifestations of the Hückel Aromaticity

“…The most noticeable feature of the triangle is the B−S distance of 1.782(6) Å, which suggests a significant double-bond character. It is only about 0.03 Å longer than the B−S bond length reported in the manganese complex Mn(η 5 25 and about 0.07 Å longer than that found in the cation SB{κ 2 26 species reported as the first ones featuring a BS double bond. The three-membered rings of 3 and 4 resemble that of the intermediate recently proposed by Braunschweig and co-workers for reaction of the alkylborylene complex Mn(η 5 -C 5 H 5 )(B t Bu)(CO) 2 with SPPh 3 , which yields the metathesis product Mn(η 5 -C 5 H 5 )(CO) 2 (PPh 3 ).…”