Ruthenium, Rhodium, and Iridium Bis(σ-B−H) Diisopropylaminoborane Complexes

Abstract

The coordination chemistry of diisopropylaminoborane H 2 B-N i Pr 2 with valence isoelectronic metal fragments to form, essentially isostructural, [MH 2 (η 2 :η 2 -H 2 B-N i Pr 2 )(PCy 3 ) 2 ] nþ (M = Ru, n = 0; Rh and Ir, n = 1) has been explored by a combination of X-ray crystallography, NMR spectroscopy, and computational techniques. In the solid state and solution the aminoborane interacts with the metal centers through one four-center four-electron interaction, forming bis(σ-B-H) complexes. The structural data point to tighter interactions between both the Ru and Ir congeners compared to the Rh with significantly shorter M 3 3 3 B distances in the first two. These tighter interactions are mirrored in the spectroscopic data, with the Ru and Ir complexes showing more deshielded 11 B chemical shifts and 1 H M-H-B resonances that are more shielded than observed for the rhodium complex. Analysis of the bonding between metal and borane using the NBO approach is in very good agreement with the variations in the geometrical and spectroscopic parameters. There is overall a stronger interaction between the borane and the metal fragment for neutral Ru compared to cationic Rh, with cationic Ir in an intermediate situation. † Part of the Dietmar Seyferth Festschrift. In honor of Prof. Dr. h.c. mult. Dietmar Seyferth for his outstanding contribution as Editor of Organometallics.

Synthesis and characterisation of ruthenium dihydrogen complexes and their reactivity towards B–H bonds

“…This arrangement is in agreement with a typical "true" (σ-B-H)-bonding to ruthenium reported by Sabo-Etienne et al 13,14 Moreover, H1 can be attributed as a hydride, although the short Ru1-H5 distance of 1.48 (8) Moreover the solid state structure of 11 confirms the bond cleavage of the dimethylamine borane. The reactivity of complex 6 towards THF borane complex or dimethylamine borane, in routes a and b, remains still uncleared, but regarding the borane compounds as Lewis-pairs, it is plausible that THF or dimethylamine is replaced by a stronger Lewis base system (Fig.…”

“…Furthermore the Ru-B distance is 2.19(2) Å and thus in the range of previously reported agostic ruthenium boron complexes. 13,14 Fig. 7 IR spectra of complex 11.…”

“…As a consequence, the transformation of complex 1 into "true" bis(σ-B-H) complexes 2a-c was reported. 13,14 So far, only a small number of "true" σ-borane complexes have been isolated. 14,15 Ruthenium dihydrogen complexes can also be stabilised with pincer ligands, for example complex 3 which was reported by Leitner.…”

“…13,14 So far, only a small number of "true" σ-borane complexes have been isolated. 14,15 Ruthenium dihydrogen complexes can also be stabilised with pincer ligands, for example complex 3 which was reported by Leitner. Complex 3 is capable of H/D exchange, hydrogenation or dehydrogenation and borylation of terminal alkynes.…”

Synthesis of a ruthenium bis(diisopropylamino(isocyano)borane) complex from the activation of an amino(cyano)borane

“…[12][13][14] Their syntheses are restricted to salt elimination from organometallic nucleophiles [M(CO) 5 (CN)] − and suitable haloboranes, 12,13 or to isomerization of the BCN linkage of a B-cyanoborane upon coordination to chromium. 12,14,15 As part of our ongoing program on the chemistry of σ-complexes and more particularly on bis(σ-borane) and agostic borane complexes, [16][17][18][19][20] we addressed the synthesis of the amino(cyano)borane i Pr 2 NBH(CN) (2) and its reactivity with the ruthenium precursor [RuH 2 (η 2 -H 2 ) 2 (PCy 3 ) 2 ] (3). We report here the isolation and the characterization of a new cyano ruthenium bis(isocyano)borane complex.…”