Partially and Fully Reversible Solvation-Controlled Borylene Swapping and Metal-Only Lewis Pair Formation

Abstract

New borylene-containing metal-only Lewis pairs based on group 6 metals and ruthenium are prepared by a partially reversible borylene transfer from group 6 borylene complexes [M{BN­(SiMe3)2}­(CO)5] (M = Mo, W). The complexes contain strong Ru → Mo/W dative interactions. As in a previous report on related compounds, redissolving these complexes resulted in reversion back to the precursors, enabled by a sacrificial CO donor. It was observed that this reversion process becomes less selective as the group 6 metal becomes heavier, leading to greater amounts of unidentified byproducts as the group is descended.

Complexation and Release of N-Heterocyclic Carbene-Aminoborylene Ligands from Group VI and VIII Metals

“…The unique robustness and purely σ-donor nature of these M–B linkages (Figure , right) is highly reminiscent of NHC-metal complexes. Indeed, reaction of 2 with the cationic coinage metal species [(IDipp)­CuOTf] results in the formation of the “metal-only Lewis pair” (MOLP) − species 6 (Scheme ), Figure ) where a Fe–Cu bond has been formed. This observation stands in contrast to known metalloborylene reactivity with coinage metals, where coordination to the borylene M–B π-bond has been described .…”

Reactivity of Transition-Metal Borylene Complexes: Recent Advances in B–C and B–B Bond Formation via Borylene Ligand Coupling

“…This intrinsic electronic distinction between amino- and alkyl-/arylborylenes differentiates their chemical reactivity. Reactivity studies have shown that group 6 aminoborylenes serve as an excellent source for the borylene [:BR] fragment, which allows direct boron functionalization of both organic − and organometallic substrates. ,− One particularly useful application of this chemistry is in the synthesis of new terminal and bridging borylene complexes. The first terminal bis­(borylene) [(η 5 -C 5 Me 5 )­Ir­{BN­(SiMe 3 ) 2 } 2 ] ( 2 ) was synthesized (Scheme , A ) by adding 2 equiv of the chromium aminoborylene complex [(OC) 5 CrBN­(SiMe 3 ) 2 ] ( 1 ) as a borylene source to 1 equiv of the iridium carbonyl complex [(η 5 -C 5 Me 5 )­Ir­(CO) 2 ] under photolytic conditions …”

Steric Control between Neutral Metal-Only Lewis Pairs and Metal-Stabilized Gallenium and Gallinium Cations

“…When we began our work in this field, perhaps the most well-studied subset of MOLPs was that featuring zerovalent group 8 donors (M 0 L n , M = Fe, Ru, Os) and transition metal acceptors, thanks to extensive work by the groups of Pomeroy, Mak, and Dixneuf (and subsequently also Krossing). , However, MOLPs featuring zerovalent group 8 donors and simple main-group Lewis acids were at that time unknown. After our discovery that gallium trihalides form stable Lewis adducts with pentacoordinate Fe 0 complexes, we began a systematic study of MOLPs of the form [L n Fe 0 /L n Ru 0 →GaX 3 ]. , Using a range of different donor ligands bound to the group 8 metal centers, we were able to establish trends in the Lewis basicity of Fe 0 and Ru 0 complexes by comparisons of M–Ga bond distances, sums of X–Ga–X angles, and computationally derived bond dissociation energies.…”