Steric Effects Dictate the Formation of Terminal Arylborylene Complexes of Ruthenium from Dihydroboranes

Abstract

The steric and electronic properties of aryl substituents in monoaryl borohydrides (Li[ArBH 3 ]) and dihydroboranes were systematically varied and their reactions with [Ru(PCy 3 ) 2 HCl(H 2 )] (Cy:c yclohexyl) were studied, resulting in bis(s)-borane or terminal borylene complexes of ruthenium. These variationsa llowed for the investigationo ft he factors involved in the activationo fd ihydroboranes in the synthesis of terminal borylene complexes. The complexes were studied by multinuclear NMR spectroscopy,m asss pectrometry, X-ray diffractiona nalysis, and density functional theory (DFT) calculations. The experimental and computational results suggest that the ortho-substitution of the aryl groupsi sn ecessary for the formationo ft erminal borylene complexes.Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.

Recent Advances in the Synthesis and Reactivity of Transition Metal σ-Borane/Borate Complexes

“…and Figure 3), 3 while the reactions with dihydroboranes yielded the bis(σ)-borane complexes [(Cy 3 P) 2 RuHCl(η 2 -H 2 BR)] (12b−16b). 27), respectively, was obtained.…”

“…The solid-state structure of 49 displayed the attachment of an alkenylborane unit, {( p -Tol)­C­(H)CH–BC­(Me)­( p -Tol)}, to manganese in an η 4 fashion. The B–C bond length in the {BC­( p -Tol)­(Me)} unit of 49 (1.482(4) Å) is shorter than that in [(Cy 3 P) 2 Ru­(H) 2 (η 2 -H 2 BDur)] (1.5585(5) Å), which suggests its partial double-bond character. Thus, this molecule can be considered an analogue of an η 4 -( E )-butadiene-coordinated manganese complex.…”

“…In recent work, we have investigated the steric and electronic factors required to generate borylene complexes from the corresponding bis­(σ)-borane species via dehydrogenation . A range of dihydridobis­(σ)-borane complexes [(Cy 3 P) 2 Ru­(H) 2 (η 2 -H 2 BR)] ( 12a – 16a ) were isolated from the reactions of [(Cy 3 P) 2 RuHCl­(H 2 )] and lithium trihydroborates (Scheme and Figure ), while the reactions with dihydroboranes yielded the bis­(σ)-borane complexes [(Cy 3 P) 2 RuHCl­(η 2 -H 2 BR)] ( 12b – 16b ) . The Ru–B bond lengths in 12a – 16a (1.944(3)–1.964(3) Å) are similar to that in [(Cy 3 P) 2 Ru­(H 2 )­(η 2 -H 2 BMes)] (1.938(4) Å) (Table ).…”

“…The reaction of [(Cy 3 P) 2 IrH­(Cl) 2 ] with either Li­[BH 3 (Dur)] or Na­[BAr F 4 ]/DurBH 2 yielded the iridium bis­(σ)-borate complex [(Cy 3 P) 2 H 2 Ir­{BH 3 (Dur)}] ( 35 ) (Scheme ). The 1 H NMR signals at −19.83 and −6.37 ppm suggested the presence of Ir–H and Ir– H –B hydride ligands, respectively. The molecular structure of 35 shows the presence of a tetrahedral boron center with an Ir–B distance of 2.237(3) Å, similar to those in related iridium dihydroborate complexes.…”

From trihydroborates to bisborylenes: a route to dinuclear bisborylene complexes

“…8 f Due to the formation of two metal–boron linkages the 11 B NMR resonances of 3a and 4a are remarkably shifted downfield in comparison to ruthenium terminal borylenes (98.8–110.9 ppm). 7 e ,16…”