Catalytic, <i>Z</i>-Selective, Semi-Hydrogenation of Alkynes with a Zinc–Anilide Complex

Baker, Greg; White, Andrew J. P.; Casely, Ian J.; Grainger, Damian M.; Crimmin, Mark R.

doi:10.1021/jacs.3c02301

Cited by 16 publications

(13 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…But in both cases, no reaction takes place at room temperature, while mild heating leads to the thermal decomposition of [ZnH 2 ] ∞ itself . A σ-bond metathesis between H 2 and the terminal Zn–N HMDS of 1 or the Zn–C Et of 2 could be a possibility . But both 1 and 2 are inert toward H 2 (1 atm), at least up to 60 °C.…”

Section: Results and Discussionmentioning

confidence: 99%

2-Anilidomethylpyridine-Derived Three-Coordinate Zinc Hydride: The Journey Unveils Anilide Backbone’s Reactive Nature

Mandal,

Joshi,

Das

et al. 2023

Inorg. Chem.

View full text Add to dashboard Cite

Low-coordinate heteroleptic zinc hydrides are catalytically important but rare and synthetically challenging. We herein report three-coordinate monomeric zinc hydride on a 2anilidomethylpyridine framework ( NN L). The synthetic success comes through systematically screening a few different routes from different precursors. During the process, the ligand's anilide backbone interestingly appears to be more reactive than Zn's terminal site to electrophilic Lewis and Brønsted acids. The proligand NN LH reacts with [Zn{N(SiMe 3 ) 2 } 2 ] and ZnEt 2 to give [( NN L)ZnA] (A = N(SiMe 3 ) 2 (1), Et(2)). Both are inert to PhSiH 3 and H 2 but react with HBpin only through the internal Zn−N anilide bond to give the borylated ligand NN LBpin (3). The reactions of 1 and 2 with Ph 3 EOH (E = C, Si) afford a series of divergent compounds like [( NN LH)Zn(OSiPh 3 ) 2 ] (4), [Zn 3 (OSiPh 3 ) 4 Et 2 ] (5), and [EtZn(OCPh 3 )] (6). But in all cases, it is invariably the Zn−N anilide bond protonated by the −OH with equal or higher preference than the terminal Zn−N or Zn−C bonds. A DFT analysis rationalizes the origin of such a reactivity pattern. Realizing that an acidfree route might be the key, reacting [( NN L)Li] with ZnBr 2 gives [( NN L)Zn(μ-Br)] 2 (7), which on successively treating with KOSiPh 3 and PhSiH 3 gives the desired [( NN L)ZnH] (8) as a three-coordinate monomer with a terminal Zn−H bond. Estimating the ligand steric in 8 shows the openness in Zn's coordination sphere, a desired criterion for efficient catalysis. This and a positive influence of the pyridyl sidearm is reflected in 8's superior activity in hydroborating PhC(O)Me by HBpin in comparison to Jones' two-coordinate anilido zinc hydride.

show abstract

Section: Results and Discussionmentioning

confidence: 99%

2-Anilidomethylpyridine-Derived Three-Coordinate Zinc Hydride: The Journey Unveils Anilide Backbone’s Reactive Nature

Mandal,

Joshi,

Das

et al. 2023

Inorg. Chem.

View full text Add to dashboard Cite

show abstract

“…Very recently, Crimmin and coworkers reported a zincanilide complex, Zn-15 (Figure 15), that operates as an alkyne semihydrogenation catalyst. [96] This catalyst was applied on a variety of internal and terminal alkynes, using 10 mol% loading in toluene, at 145 °C under 23 bar of H 2 , typically for a duration of 18 h. The corresponding alkenes were obtained in low-to-high yields (9-99 %) and generally high selectivity for the Z isomer (99 : 1 in the majority of cases). This represents the first example of a selective hydrogenation catalyzed by a zinc complex.…”

Section: Hydrogenation Catalystsmentioning

confidence: 99%

“…Finally, a very recent publication by Harder and coworkers demonstrates that the readily-available compound LiAlH 4 , in conjunction with finely-divided metallic iron, can be used as a potent catalyst for the hydrogenation of alkenes and even arenes. [97] The catalytic experiments were typically carried out [96] using a ~1 : 2 LiAlH 4 /Fe mixture at 2.5 mol% loading in the neat substrate, with heating at 120 °C under an initial H 2 pressure of 50 bar. Under these conditions, a number of internal alkenes, both linear and cyclic, as well as arenes, were hydrogenated into the respective alkanes in variable conversions, some reaching quantitative yield.…”

Section: Hydrogenation Catalystsmentioning

confidence: 99%

See 1 more Smart Citation

Catalytic Main‐Group Metal Complexes of Phosphine‐Based Pincer Ligands

Montag

Milstein

2023

Israel Journal of Chemistry

View full text Add to dashboard Cite

Pincer ligand complexes, which appeared nearly five decades ago, have provided a valuable platform for the study of fundamental chemical processes and the development of efficient catalysts for many chemical transformations. These complexes have usually contained transition metal atoms or ions, and their respective pincer ligands have often featured phosphine donor groups, which strongly coordinate to the metal center and allow its steric and electronic properties to be fine‐tuned. The increasing need to develop cost‐effective and sustainable catalytic processes has driven the search for main‐group metals as alternatives to commonly‐used transition metals. In this review, we show that despite the inherent mismatch between phosphines, which are soft Lewis bases, and main‐group metal ions, which are hard Lewis acids, a series of well‐defined phosphine‐based pincer complexes containing Li(I), Na(I), K(I), Mg(II), Ca(II), Zn(II) and Al(III) have been reported, which have proven to be active catalysts for industrially‐relevant transformations.

show abstract

“…Although some heterobimetallic metal–zinc complexes featuring a transition metal ( IV , VI ) − and a main group metal ( V ) , activate dihydrogen (Scheme ), hydrogenation catalysis by zinc complexes remains scarce. After the report of decamethylzincocene [ZnCp* 2 ] (Cp* = η-C 5 Me 5 ) for the hydrogenation of imines by Jochmann and Stephan, Milstein and co-workers reported the hydrogenation of imines and ketones using a zinc pincer complex [(PNP t Bu )ZnMe] ( II ) by metal–ligand cooperation and Crimmin and co-workers demonstrated reversible hydrogen activation as well as alkyne semihydrogenation using the zinc anilide complex [(BDI)ZnNHPh] ( III ) (BDI = [HC{C(CH 3 )N-(2,6- i Pr 2 C 6 H 3 )} 2 ] . While few examples of dihydrogen activation by zinc(II) complexes are known, dinuclear zinc(I) complexes including decamethyldizincocene [Zn 2 Cp* 2 ] (Cp* = η 5 -C 5 Me 5 ) reported by Carmona and co-workers have not been reported to react with dihydrogen.…”

Section: Introductionmentioning

confidence: 99%

Dihydrogen Cleavage by a Zinc–Zinc Bond of a Heteroleptic Dizinc(I) Cation

Mahawar,

Rajeshkumar,

Spaniol

et al. 2024

Inorg. Chem.

View full text Add to dashboard Cite

Oxidative addition of dihydrogen across a metal−metal bond to form reactive metal hydrides in homogeneous catalysis is known for transition metals but not for zinc(I)−zinc(I) bond as found in Carmona's eponymous dizinconene [Zn 2 Cp* 2 ] (Cp* = η 5 -C 5 Me 5 ). Dihydrogen reacted with the heteroleptic zinc(I)−zinc(I) bonded cation [(L 2 )Zn−ZnCp*][BAr 4 F ] (L 2 = TMEDA, N,N,N′,N′-tetramethylethylenediamine, TEEDA, N,N,N′,N′-tetraethylethylenediamine; Ar F = 3,5-(CF 3 ) 2 C 6 H 3 ) under 2 bar at 80 °C to give the zinc(II) hydride cation [(L 2 )ZnH(thf)][BAr 4 F ] along with zinc metal and Cp*H derived from the intermediate [Cp*ZnH]. DFT calculations show that the cleavage of dihydrogen occurs through a highly unsymmetrical transition state. Mechanistic studies agree with a heterolytic cleavage of dihydrogen as a result of the cationic charge and unsymmetrical ligand coordination. To explore the existence of zinc(I) hydride, thermally unstable hydridotriphenylborate complexes of zinc(I) [(L 2 )Zn(HBPh 3 )−ZnCp*] (L 2 = TMEDA, TEEDA; TMPDA, N,N,N′,N′-tetramethyl-1,3-propylenediamine) have been prepared by salt metathesis and were shown to undergo fast exchange with both BPh 3 and [HBPh 3 ] − .

show abstract

Catalytic, Z-Selective, Semi-Hydrogenation of Alkynes with a Zinc–Anilide Complex

Cited by 16 publications

References 65 publications

2-Anilidomethylpyridine-Derived Three-Coordinate Zinc Hydride: The Journey Unveils Anilide Backbone’s Reactive Nature

2-Anilidomethylpyridine-Derived Three-Coordinate Zinc Hydride: The Journey Unveils Anilide Backbone’s Reactive Nature

Catalytic Main‐Group Metal Complexes of Phosphine‐Based Pincer Ligands

Dihydrogen Cleavage by a Zinc–Zinc Bond of a Heteroleptic Dizinc(I) Cation

Contact Info

Product

Resources

About