Amidinatoamidosilylene–Dibromodiborene

Abstract

The amidinatoamidosilylene [LSiNMe 2 ] [1; L = PhC(NtBu) 2 ] was reacted with B 2 Br 4 (SMe 2 ) 2 in toluene at room temperature to form the bis(silylene)tetrabromodiborane [L{Me 2 N}Si] 2 B 2 Br 4 (2). It was then reacted with excess KC 8 in tetrahydrofuran at room temperature to afford the bis(silylene)dibromodiborene [L{Me 2 N}Si] 2 B 2 Br 2 (3).

N-Phosphinoamidinato Silylene– and Phosphine–Borylborylene Complexes

“…The Wiberg bond index (WBI) suggests that the B2–B1 bond has some double bond characters (WBI: 1.38). It is smaller than that of the bis­(silylene)–diborene compound [L­(Me 2 N)­SiB­(Br)=B­(Br)­Si­(NMe 2 )­L] (WBI: 1.66) . Accordingly, the natural bond orbital (NBO) analysis shows that the B1–B2 π orbital is formed by the overlapping of the B p orbitals and polarized toward the B2 atom (68.9% B2+ 31.1% B1).…”

“…This indicates that the lone pair electrons on the borylene center are delocalized to the vacant p orbital on the boryl center, and hence, compound 2 has a canonical form B (Scheme ). In addition, the B1–Si1 bond length (1.911(9) Å) is shorter than those of the bis­(silylene)–tetrabromodiborane [L­{Me 2 N}­Si] 2 B 2 Br 4 (2.029(2) Å) and the bis­(silylene)–diborene compound [L­(Me 2 N)­SiB­(Br)=B­(Br)­Si­(NMe 2 )­L] (1.961(13) Å) . This indicates that the lone pair electrons on the borylene center is stabilized by the silylene donor.…”

Synthesis and hydrogenation of polycyclic aromatic hydrocarbon-substituted diborenesviauncatalysed hydrogenative B–C bond cleavage

“…For these PAH-substituted diborenes the formation of both 13-Ar and 17-Ar, and eventually both mechanisms, are therefore energetically accessible. Nevertheless, the experimentally observed intermediate 8-Ar, formed by reassociation of PMe 3 to 13-Ar, is in all cases thermodynamically favoured over the direct Competition for the initial C-H or H-H activation is not seen with diborene II, as activating the ortho-methyl C-H bond of the mesityl substituent is energetically less favoured (DG ‡ ¼ 32.3 kcal mol À1 , TS-Mes (12)(13)) than the activation of H 2 (DG ‡ ¼ 28.2 kcal mol À1 , TS-Mes (12)(13)(14)(15)(16)(17), Fig. 9).…”

“…aryl, heteroaryl, alkyl, vinyl, halide, cyanide, hydride)) are most oen synthesised either by the reductive coupling of two LBYX 2 precursors (X ¼ halide), [3][4][5][6][7][8][9][10] or the reduction of 1,2-dihalodiboranes of the form L 2 B 2 Y 2 X 2 . 3,[11][12][13][14] Since the apolar B-B bond of symmetrical diborenes oen makes them relatively unreactive, recent efforts have also focused on synthesising polar, unsymmetrical diborenes by the reduction of unsymmetrically substituted 1,2-dihalodiboranes of the form LL 0 B 2 YY 0 X 2 . [15][16][17][18][19][20] The stereoelectronic nature of the substituents of the B]B double bond greatly inuences its reactivity by tuning the energies (and sometimes localisation) of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO).…”

“…aryl, heteroaryl, alkyl, vinyl, halide, cyanide, hydride)) are most often synthesised either by the reductive coupling of two LBYX 2 precursors (X = halide), 3–10 or the reduction of 1,2-dihalodiboranes of the form L 2 B 2 Y 2 X 2 . 3,11–14 Since the apolar B–B bond of symmetrical diborenes often makes them relatively unreactive, recent efforts have also focused on synthesising polar, unsymmetrical diborenes by the reduction of unsymmetrically substituted 1,2-dihalodiboranes of the form LL′B 2 YY′X 2 . 15–20…”