Bis- and Tris(2-oxobenzimidazolyl)hydroborato Complexes of Sodium and Thallium: New Classes of Bidentate and Tridentate Oxygen Donor Ligands

Abstract

A series of bis- and tris(oxobenzimidazolyl)hydroborato compounds, namely, [Bo]Na and [To]-Na (R = Me, Bu, Ad), which feature uncommon sterically demanding LX [O] and LX [O] donor ligands, have been obtained via the reactions of NaBH with 1-R-1,3-dihydro-2H-benzimidazol-2-ones. Evidence that the alkyl substituents are suitably located to have a significant impact on the coordination environment is provided by the observation that the methyl derivative [To]Na(κ-diglyme) exhibits κ-coordination of the diglyme, whereas the t-butyl and adamantyl derivatives, [To]Na(κ-diglyme) and [To]Na(κ-diglyme), exhibit κ-coordination. The [Bo] and [To] ligands also allow for isolation of discrete mononuclear thallium compounds, [Bo]Tl and [To]Tl, for which the steric demands of the ligands have been quantified in terms of both cone angle and buried volume concepts.

Organometallic Zirconium Compounds in an Oxygen-Rich Coordination Environment: Synthesis and Structural Characterization of Tris(oxoimidazolyl)hydroboratozirconium Compounds

“…Mass spectra were obtained on a Jeol JMS-HX110H tandem double-focusing mass spectrometer with a 10 kV accelerating voltage equipped with a fast-atom-bombardment ion source. CpZrCl 3 and Cp 2 ZrCl 2 were obtained from Sigma-Aldrich, while Zr­(CH 2 Ph) 4 and [To R ]­M (M = Na, Tl) , were prepared by literature methods. Caution!…”

“…Despite the formal analogy between [CpCo­{P­(O)­(OR) 2 } 3 ] and [Tp R,R′ ] ligands, however, an important distinction is that the different placement of the R substituents results in the [O 3 ] ligands being much less sterically demanding than [Tp R,R′ ]. Therefore, since sterically demanding ligands are often advantageous for supporting metal centers with uncommon coordination environments, we recently introduced a new class of L 2 X [O 3 ] ligands that are based on oxoimidazolyl donors, namely, tris­(oxoimidazolyl)­hydroborato, [To R ] . In addition, we have also reported related bis­(oxoimidazolyl)­hydroborato ligands, [Bo R ], which provide complementary LX [O 2 ] donor arrays.…”

Synthesis and Structural Characterization of Copper Complexes Containing “R-Substituted” Bis-7-Azaindolyl Borate Ligands

“…In 2008, we suggested that this new set of ligands be termed “flexible scorpionates” [ 6 , 7 ] since the consequences of this extra atom in each of the heterocycles change their properties and potential reactivity quite significantly [ 8 , 9 , 10 ]. A range of heterocycles has now been utilized to generate flexible scorpionate ligands based on sulfur [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], nitrogen [ 17 , 18 , 19 , 20 , 21 ], phosphine [ 22 , 23 ], oxygen [ 24 , 25 ] and other donors [ 26 , 27 ]. To the best of our knowledge, there are only a small number of complexes reported containing nitrogen-based flexible scorpionate ligands.…”