Generation of Cationic Two-Coordinate Group-13 Ligand Systems by Spontaneous Halide Ejection: Remarkably Nucleophile-Resistant (Dimethylamino)borylene Complexes

Abstract

Spontaneous ejection of chloride from a three-coordinate boron Lewis acid can be effected by employing very electron rich metal substituents and leads to the formation of a sterically unprotected terminal (dimethylamino)borylene complex that has a short metal-boron bond and remarkable resistance to attack by nucleophilic and protic reagents.

[B(3,5‐C6H3Cl2)4]– as a Useful Anion for Organometallic Chemistry

“…The former is a 12‐electron Rh III fragment that binds arenes (e.g., fluorobenzene) in an η 6 ‐manner, whereas the latter is formally a 12‐electron Rh III centre with a supporting C–C σ‐bond and an agostic C–H interaction. Although the [BAr Cl2 4 ] – anion was originally reported in the open literature by Pacey as the Cs + salt,10 with a refinement in the synthesis by Serwatowski and co‐workers in 2003,11 as far as we are aware it has not been utilised in organometallic chemistry to generate and stabilise potentially reactive metal cations 12. We believe that this anion will be of use to the organometallic and catalysis communities as well as those interested in the structural determination of cationic species given its ease of preparation, attractive solubility properties, lack of anion disorder in the solid‐state, comparable coordinating properties to C 6 H 5 F and [BAr F 4 ] – , and its expedient use in synthesis.…”

“…An approximate coordinating ability can also be established compared with [BAr F 4 ] – and C 6 H 5 F in which [BAr Cl2 4 ] – interacts with very open metal centres more strongly than [BAr F 4 ] – , but is competitive, although more strongly binding, with the weakly coordinating solvent C 6 H 5 F. With less available, albeit reactive, metal centres, e.g., 1 [BAr Cl2 4 ], the coordinating properties of the anions are levelled and neither interact. Indeed in this respect, [BAr Cl2 4 ] – has very recently been used in the isolation of a two‐coordinate‐at‐boron, 18‐valence‐electron, cationic, iron–borylene complex, in which these desirable properties of solubility, ease of synthesis and chemical robustness are further highlighted 12. Of course, in systems in which oxidative addition to a metal centre of aryl chlorides is a straightforward process,15 such as in cross‐coupling reactions,16 these anions might be of less use, although this offers potential opportunities for derivatisation of the anion itself.…”

Synthesis of Base-Stabilized Hydrido(hydroborylene)tungsten Complexes and Their Reactions with Terminal Alkynes To Give η3-Boraallyl Complexes

“…Aldridge et al reported that oxidative addition of a B–H bond of dihydroaminoboranes H 2 BNR 2 (R = i Pr, Cy) to an iridium center and subsequent 1,2-hydride migration triggered by chloride abstraction from the iridium center resulted in the formation of cationic borylene complexes [ fac -Ir­(PMe 3 ) 3 (H) 2 (BNR 2 )]­[BAr F 4 ] . Aldridge et al also reported another approach to the synthesis of cationic borylene complexes [Cp*Fe­(CO) 2 (BMes)] + and [CpFe­(dmpe) 2 (BNMe 2 )] + through halide abstraction from the haloboryl complexes …”

DFT Study on Alkyl‐ and Haloborylene Complexes of Manganese and Rhenium: Structure and Bonding Energy Analysis in [(η5‐C5H5)(CO)2M(BR)] and [(η5‐C5H5)(CO)2M(BX)] (M = Mn, Re; R = Me, Et, iPr, tBu; X = F, Cl, Br, I)

“…The first bridging borylene complexes,3 as well as the only known terminal alkyl borylene complex,4 all partly owe their stability to the properties of the manganese fragment. In terms of transition metal borylene chemistry, twelve structurally characterized neutral terminal transition metal borylene complexes (Scheme )4–14 and nine terminal cationic transition metal borylene complexes (Scheme )15–22 have been reported. Additionally, a number of base‐stabilized adducts formed by the coordination of a Lewis base (main group or transition metal) to the two‐ or three‐coordinate boron center have also been prepared.…”