Synthesis and Structure of the First Terminal Borylene Complexes

Abstract

A nearly linear arrangement is observed for the three atoms in the central W-B-N unit of the tungsten complex [(CO) WBN(SiMe ) ] (1) in the crystal (W-B-N 177.9°; see picture). This compound along with its Cr analogue represent the first examples of terminal borylene complexes with a two-coordinate metal-bound boron atom. The geometries of the axial and equatorial CO groups in 1 are similar, and thus indicate that there is no trans effect of the borylene ligand.

Chemistry of metal – boron double bonds

“…For neutral systems, the crystallographic characterization of aminoborylene systems (OC) 5 M[BN(SiMe 3 ) 2 ] (M ¼ W, 2; Cr, 3) allows comparison of complexes that differ only at the metal centre [39,42]. As expected on the basis of the respective covalent radii, the metal -boron distance in 2 [2.151 (7) [39].…”

“…As expected on the basis of the respective covalent radii, the metal -boron distance in 2 [2.151 (7) [39]. On this basis, alternative descriptions have been discussed for complexes 1 and 21 as nidocarboranes featuring exo MÀ ÀB bonds, since similarly high field 11 B chemical shifts are typically measured for the apical boron atom of such cluster species [8].…”

“…Reflecting the inherent difficulties associated with their synthesis, borylene complexes are still comparatively rare, with the first structurally authenticated complexes featuring the BX in bridging and terminal coordination modes being reported in 1995 [37] and 1998 [38,39], respectively. Notwithstanding this, terminal borylene complexes are of significant interest, both from a structure/bonding perspective (e.g.…”

Structures and Bonding Situation of Iron Complexes of Group‐13 Half‐Sandwich ECp* (E = B to Tl) Based on DFT Calculations

“…Among the spectacular highlights of experimental research are the first isolation of an terminal alane diyl complex [(CO) 4 Fe‐AlCp*],15 then the examples of stable borylene complexes [(CO) 4 Fe‐BCp*],31 and [(CO) 5 W‐BN‐(SiMe 3 ) 2 ],32 the synthesis of the “ferrogallyne” [(CO) 4 FeGaAr*] (Ar*) 2, 6‐(2, 4,6‐triisopropylphenyl)phenyl),33 and the first homoleptic diyl complexes [Ni( E ‐C(SiMe 3 ) 3 ) 4 ] ( E = In34 and E = Ga35). The studies indicate that the nature of the iron group‐13 half‐sandwich bonding in complexes [(CO) 4 Fe‐ E (η 5 ‐C 5 Me 5 )] ( E = B to In) was addressed the theoretical investigation by Macdonald and Cowley 36.…”

Element 5 – Boron

“…[44] H. Braunschweig and co-workers reported the first stable terminal borylene complexes 14 (M ¼ Cr, W; Chart 5). [45] The B-N bond is isosteric and isoelectronic with the C-C bond and many examples of so-called 'BN/CC isosterism' are known. [46] The classic example is borazine 15 (also known as 'inorganic benzene'; Chart 5), the stable B-N analogue of benzene, prepared by a reaction of diborane with ammonia.…”