Base‐Stabilized Boryl and Cationic Haloborylene Complexes of Iron

Abstract

The synthesis of base-stabilized boryl and borylene complexes is reported. An N-heterocyclic carbene (NHC)-stabilized iron-dihydroboryl complex was prepared by two different routes including methane liberation and salt elimination. A range of base-stabilized iron-dichloroboryl complexes was prepared by addition of Lewis bases to boryl complexes. Base-stabilized, cationic monochloroborylene complexes were synthesized from these boryl complexes by halide abstraction by using weakly coordinating anions.

Activation of boryl-, borylene and metalloborylene complexes by isonitriles

“…In contrast to the high thermodynamic stability displayed by the [(Z 5 -C 5 Me 5 )(OC) 2 FeB(L)Cl 2 ] complexes, 9 the insertion of tBuNC into the Fe-B bond was found to be completely reversible. Upon treatment of 2 with B(C 6 F 5 ) 3 , full conversion to compound 1 and the Lewis acid-base pair (C 6 F 5 ) 3 B-CNtBu was observed by NMR.…”

“…[3][4][5][6][7][8] In recent studies, where the iron dichloroboryl complex [(Z 5 -C 5 Me 5 )(OC) 2 Fe-BCl 2 ] (1) was treated with Lewis-bases including 3,5-lutidine, IMe (:C(NMeCH) 2 ) and PMe 3 , efficient formation of the corresponding Lewis acid-base adducts [(Z 5 -C 5 Me 5 )(OC) 2 Fe-B(L)Cl 2 ] (L = 3,5-lutidine, IMe and PMe 3 ) was observed. 9,10 Similarly, reactions of the borylene complex [(Z 5 -C 5 H 5 )(OC) 2 MnQBtBu] with Lewis bases yielded the acid-base adducts [(Z 5 -C 5 H 5 )(OC) 2 MnQB(L)tBu] (L = lutidine, dimethylaminopyridine, IMe). 11 However, reactions of boryls and borylenes with isonitriles showed different reactivity patterns, which is not altogether surprising, as there are documented differences between the reactivities of isonitriles and Lewis bases such as carbenes, phosphine and amines that extend beyond simple differences in basic strength.…”

Fundamental and Applied Properties of Borocations

“…This disparity was attributed to different equilibrium positions, but borenium cations are definitely present in these mixtures as + 0. 4 ] À , that do not participate in any halide transfer equilibria. According to a combined experimental and computational study, the borylation of activated arenes at 20 C proceeds through a S E Ar mechanism with borenium cations as the key electrophiles [10].…”

“…Current mechanistic hypotheses, limitations and future challenges will also be discussed. Due to space limitations, this article is limited to (i) the condensed phase reactivity of borocations (for gas phase reactivity, see Piers and co-workers [2]), (ii) metal-free borocations (for cationic transition metal borylenes, see references in [4]), and (iii) borocations directly bound to two R groups ( Fig. 1), with R 3 B with peripheral cationic groups also beyond the scope of this review [5].…”

Boron-Based Lewis Acid Transition Metal Complexes as Potential Bifunctional Catalysts

“…Typical electron donor group PMe 3 could also be used to form analogous complex 12c. [35] Although only monodentate boryl complexes were found until now, type B complexes with multidentate chelate ligands should also be able to be designed and synthesized by using the same strategy in the future. After the dissociation of the additional electron donor ligand, type B complexes may be expected to exhibit unique LA-TM catalytic feature.…”