Catalytic dehydrogenation of dimethylamine borane by group 4 metallocene alkyne complexes and homoleptic amido compounds

Beweries, Torsten; Hansen, Sven; Kessler, Monty; Klahn, Marcus; Rosenthal, Uwe

doi:10.1039/c1dt10366k

Cited by 53 publications

(37 citation statements)

References 26 publications

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“…[94]. The Cp* analogue, however, showed no dehydrocoupling activity, highlighting the importance of sterics in designing systems for dehydrocoupling with early transition metal systems [93].…”

Section: Sigma Complexes Of Amine-boranesmentioning

confidence: 98%

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

Johnson

Hooper

Weller

2015

Synthesis and Application of Organoboron Compounds

125

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Section: Sigma Complexes Of Amine-boranesmentioning

confidence: 98%

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

Johnson

Hooper

Weller

2015

Synthesis and Application of Organoboron Compounds

125

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“…The catalytic dehydrogenation of dimethylamine borane and hydrazine borane by titanocene bis(trimethylsilyl)acetylene complexes was described by Beweries and co-workers (Scheme 61). [74,[86][87][88] Regarding dimethylamine borane the above mentioned 2phosphinoaryloxide titanocene(III) complexes (Scheme 50) were used. [74] These complexes like Cp 2 Ti(O-C 6 H 4 -PR 2 ) and Cp* 2 Ti(O-C 6 H 4 -PR 2 ) (R = iPr, Ph) were investigated and compared to known complexes like Cp 2 Ti(O-C 6 H 4 -Pt-Bu 2 ) from Wass and coworkers [84] with or the compounds Cp 2 Ti(NPh 2 BH 3 ) and Cp 2 Ti(NMe 2 BH 3 ) from Manners et al [85] and Cp 2 Ti(η 2 -btmsa).…”

Section: Catalytic Reactionsmentioning

confidence: 99%

“…These investigations were extended to metallocene alkyne complexes of the type Cp′ 2 M(L)(η 2 -btmsa) (M = Ti, no L, Cp′ = Cp, Cp*; M = Zr, Cp′ = Cp, L = py; M = Zr, Cp′ = Cp*, no L). [86] All these compounds release the alkyne with formation of the highly reactive 14 electron fragments [Cp′ 2 M] as the basic for the catalytic reaction. The best results were obtained with Cp 2 Ti(η 2 -btmsa) and Cp 2 Zr(py)(η 2 -btmsa) after a short reaction time.…”

Section: Catalytic Reactionsmentioning

confidence: 99%

Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes

Rosenthal

2019

Eur J Inorg Chem

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With the 30 years old first example of a stable group 4 metallocene bis(trimethylsilyl)acetylene (btmsa) complex Cp2Ti(η2‐btmsa) a series of similar complexes like Cp′2M(η2‐btmsa) (M = Ti, Zr; Cp′ = Cp, Cp* as η5‐pentamethylcyclopentadienyl and Cp′2 = rac‐(ebthi) as rac‐1,2‐ethylene‐1,1′‐bis(η5‐tetrahydroindenyl) ) represent excellent sources for the generation of the very reactive coordinatively and electronically unsaturated complex fragments [Cp'2M], which were used in many synthetic and catalytic reactions. Examples for this were oresented in several papers and summarized in some reviews. In this update new reactions of group 4 metallocene bis(trimethylsilyl)acetylene complexes towards symmetrically and unsymmetrically α‐dihetero‐substituted alkynes, reactions with other alkynes, di‐ and polyynes to metallacyclopentadienes as well as the conversions of the formed products are summarized. Additionally, novel synthetic applications of the formed metallacyclopentadienes on the basis of the zirconocene bis(trimethylsilyl)acetylene complex Cp2Zr(py)(η2‐btmsa) are highlighted. Reactions with imines, neutral N‐donor ligands, E‐H compounds (E = N, O, P), molecular hydrogen, water, phosphino‐ and aminoboranes, E‐Cl compounds (E = C, P), disilylated germylenes and aryloxy ketones were described. Different self‐assembly reactions to multinuclear complexes by using group 4 metallocene bis(trimethylsilyl)acetylene complexes in C‐C coupling reactions with or without C‐H bond activation to tri‐ or tetranuclear complexes are considered, too. These examples are discussed following the general L‐M‐S principle for stoichiometric and catalytic reactions, whereby different ligands L (L = Cp′ = Cp, Cp*, rac‐ebthi), metals M (M = Ti, Zr, Hf) and substrate substituents S influence the reactivity and the obtained products.

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“…Regardless, the observation of faster reactivity for less sterically encumbered substrates stands in contrast to the general trend reported for group 4 catalysts. 20,21,23,24 Using compound 1, the dehydrocoupling of t BuNH 2 BH 3 is only achieved with modest yields and several days of heating. This relationship is consistent with (N 3 N)Zr-catalyzed phosphine dehydrocoupling reactions, where reduced catalytic activity for more encumbered substrates was also observed.…”

Section: ■ Introductionmentioning

confidence: 99%

Zirconium-Catalyzed Amine Borane Dehydrocoupling and Transfer Hydrogenation

et al. 2015

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A B S T R A C T : κ 5 -( M e 3 S i N C H 2 C H 2 ) 2 N -(CH 2 CH 2 NSiMe 2 CH 2 )Zr (1) has been found to dehydrocouple amine borane substrates, RR′NHBH 3 (R = R′ = Me; R = t Bu, R′ = H; R = R′ = H), at low to moderate catalyst loadings (0.5−5 mol %) and good to excellent conversions, forming mainly borazine and borazane products. Other z i r c o n i u m c a t a l y s t s , ( N 3 N ) Z r X [ ( N 3 N ) = N -(CH 2 CH 2 NSiMe 2 CH 2 ) 3 , X = NMe 2 (2), Cl (3), and O t Bu (4)], were found to exhibit comparable activities to that of 1. Compound 1 reacts with Me 2 NHBH 3 to give (N 3 N)Zr-(NMe 2 BH 3 ) (5), which was structurally characterized and features an η 2 B−H σ-bond amido borane ligand. Because 5 is unstable with respect to borane loss to form 2, rather than β-hydrogen elimination, and 2−4 do not exhibit X ligand loss during catalysis, dehydrogenation is hypothesized to proceed via an outer-sphere-type mechanism. This proposal is supported by the catalytic hydrogenation of alkenes by 2 using amine boranes as the sacrificial source of hydrogen. ■ INTRODUCTIONApplication of amine boranes in materials science, for hydrogen storage, and in organic synthesis demonstrates the usefulness of these simple Lewis acid−base adducts as materials precursors and chemical reagents. 1−5 The most pointed driver for recent study of amine borane dehydrogenation has been the potential use of these molecules for hydrogen storage, owing to their high hydrogen content by weight and relative ease of hydrogen loss. However, thermal degradation of amine boranes is poorly controlled and time-consuming. 3,6 Thus, catalysts that operate under desirable conditions (i.e., mild temperatures and faster reaction times) to form products in a controlled manner have been sought. Some of the most active catalysts that have been reported are capable of operating at ambient temperatures using rare and expensive group 9 transition metals such as iridium and rhodium. 7−10 This is a highly active field of study, and catalysts from across the periodic table have been reported including transition-metal and main group compounds. 11−19 Group 4 catalysts were some of the earliest studied for amine borane dehydrocoupling and have elicited interest from several groups due to their high reactivity and mechanistic richness. Manners, 20−22 Chirik, 23 Rosenthal, 24 Wass, 25,26 Beweries, 24,27 and Baker 28 have all presented detailed studies of related group 4 metallocene complexes. These independent studies indicate that titanium compounds demonstrate greater activity than their heavier congeners and that increased electron donation and steric pressure from ancillary ligands decrease reactivity. Substrate selectivity was also observed for group 4 metallocenes, which demonstrated high activity for secondary amine borane dehydrocoupling, while these compounds were almost inert toward ammonia borane. The lower activity of these metallocene compounds with NH 3 BH 3 is perhaps due to competing formation of stable amido borane complexes that precipitate out of soluti...

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Catalytic dehydrogenation of dimethylamine borane by group 4 metallocene alkyne complexes and homoleptic amido compounds

Cited by 53 publications

References 26 publications

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

The Catalytic Dehydrocoupling of Amine–Boranes and Phosphine–Boranes

Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes

Zirconium-Catalyzed Amine Borane Dehydrocoupling and Transfer Hydrogenation

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