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1. Ionization of gold (γ-methoxy)vinyl complexes generates reactive gold vinyl carbene complexes

   https://doi.org/10.1039/c9sc01574d  

   Kim, Nana ; Widenhoefer, Ross A. ( June 2019 , Chemical Science)

   Cationic gold vinyl carbene/allylic cation complexes of the form ( E )-[(L)AuC(H)C(H)CAr 2 ] + OTf − {L = IPr, Ar = Ph [( E )- 5a ], L = IPr, Ar = 4-C 6 H 4 OMe [( E )- 5b ], L = P( t -Bu) 2 o -biphenyl, Ar = 4-C 6 H 4 OMe [( E )- 5c ]} were generated in solution via Lewis acid-mediated ionization of the corresponding gold (γ-methoxy)vinyl complexes ( E )-(L)AuC(H)C(H)C(OMe)Ar 2 at or below −95 °C. Complexes ( E )- 5b and ( E )- 5c were fully characterized in solution employing multinuclear NMR spectroscopy, which established the predominant contribution of the aurated allylic cation resonance structure and the significant distribution of positive charge into the γ-anisyl rings. Complex ( E )- 5b reacted rapidly at −95 °C with neutral two-electron, hydride, and oxygen atom donors exclusively at the C1 position of the vinyl carbene moiety and with p -methoxystyrene to form the corresponding vinylcyclopropane. In the absence of nucleophile ( E )- 5a decomposed predominantly via intermolecular carbene dimerization whereas formation of 1-aryl-5-methoxy indene upon ionization of ( Z )-(IPr)AuC(H)C(H)C(OMe)(4-C 6 H 4 OMe) 2 [( Z )- 6b ] implicated an intramolecular Friedel–Crafts or electrocyclic Nazarov pathway for the decomposition of the unobserved vinyl carbene complex ( Z )-[(IPr)AuC(H)C(H)C(4-C 6 H 4 OMe) 2 ] + OTf − [( Z )- 5b ]. 

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2. Requirements for Late-Stage Hydroboration of Pyridine N-Heterocyclic Carbene Iron(0) Complexes: The Role of Ancillary Ligands

   https://doi.org/10.1021/acs.organomet.1c00307  

   Kiernicki, John J. ; Zeller, Matthias ; Szymczak, Nathaniel K. ( January 2021 , Organometallics)

   null (Ed.)

   A series of zerovalent iron complexes were synthesized that contain allylic substituents attached to a 2,6-bis(imidazol-2-ylidene)pyridine pincer ligand. These species varied in the identity of their ancillary ligands and were used to study the requirements and limitations of late-stage hydroboration. While late-stage ligand functionalization can facilitate the incorporation of Lewis acidic boranes into a ligand scaffold, thereby alleviating Lewis acid/base incompatibilities of the free ligand, we identify and discuss complicating factors that arise from complexes containing labile M–L bonds. 

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3. Bridging cyanides from cyanoiron metalloligands to redox-active dinitrosyl iron units

   https://doi.org/10.1039/C8DT01761A  

   Ghosh, Pokhraj ; Quiroz, Manuel ; Pulukkody, Randara ; Bhuvanesh, Nattamai ; Darensbourg, Marcetta Y. ( January 2018 , Dalton Transactions)

   Cyanide, as an ambidentate ligand, plays a pivotal role in providing a simple diatomic building-block motif for controlled metal aggregation (M–CN–M′). Specifically, the inherent hard–soft nature of the cyanide ligand, i.e. , hard-nitrogen and soft-carbon centers, is due to electronic handles for binding Lewis acids following the hard–soft acid–base principle. Studies by Holm and Karlin showed structural and electronic requirements for cyanide-bridged (por)Fe III –CN–Cu II/I (por = porphyrin) molecular assemblies as biomimetics for cyanide-inhibited terminal quinol oxidases and cytochrome-C oxidase. The dinitrosyliron unit (DNIU) that exists in two redox states, {Fe(NO) 2 } 9 and {Fe(NO) 2 } 10 , draws attention as an electronic analogy of Cu II and Cu I , d 9 and d 10 , respectively. In similar controlled aggregations, L-type [(η 5 -C 5 R 5 )Fe(dppe)(CN)] (dppe = diphenyl phosphinoethane; R = H and Me) have been used as N-donor, μ-cyanoiron metalloligands to stabilize the DNIU in two redox states. Two bimetallic [(η 5 -C 5 R 5 )(dppe)Fe II –CN–{Fe(NO) 2 } 9 (sIMes)][BF 4 ] complexes, Fe-1 (R = H) and Fe*-1 (R = CH 3 ), showed dissimilar Fe II CN–{Fe(NO) 2 } 9 angular bends due to the electronic donor properties of the [(η 5 -C 5 R 5 )Fe(dppe)(CN)] μ-cyanoiron metalloligand. A trimetallic [(η 5 -C 5 Me 5 )(dppe)Fe II –CN] 2 –{Fe(NO) 2 } 10 complex, Fe*-2 , engaged two bridging μ-cyanoiron metalloligands to stabilize the {Fe(NO) 2 } 10 unit. The lability of the Fe II –CN–{Fe(NO) 2 } 9/10 bond was probed by suitable X-type (Na + SPh − ) and L-type (PMe 3 ) ligands. Treatment of Fe-1 and Fe*-1 with PMe 3 accounted for a reduction-induced substitution at the DNIU, releasing [(η 5 -C 5 R 5 )Fe(dppe)(CN)] and N-heterocyclic carbene, and generating (PMe 3 ) 2 Fe(NO) 2 as the reduced {Fe(NO) 2 } 10 product. 

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4. Structural Evidence for Pnictogen-Centered Lewis Acidity in Cationic Platinum-Stibine Complexes Featuring Pendent Amino or Ammonium Groups

   https://doi.org/10.3390/molecules26071985  

   Rodrigues, Roberta R. ; Gabbaï, François P. ( April 2021 , Molecules)

   null (Ed.)

   As part of our continuing interest in the chemistry of cationic antimony Lewis acids as ligands for late transition metals, we have now investigated the synthesis of platinum complexes featuring a triarylstibine ligand substituted by an o-[(dimethylamino)methyl]phenyl group referred to as ArN. More specifically, we describe the synthesis of the amino stibine ligand Ph2SbArN (L) and its platinum dichloride complex [LPtCl]Cl which exists as a chloride salt and which shows weak coordination of the amino group to the antimony center. We also report the conversion of [LPtCl]Cl into a tricationic complex [LHPt(SMe2)]3+ which has been isolated as a tris-triflate salt after reaction of [LPtCl]Cl with SMe2, HOTf and AgOTf. Finally, we show that [LHPt(SMe2)][OTf]3 acts as a catalyst for the cyclization of 2-allyl-2-(2-propynyl)malonate. 

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5. Realizing Efficient Lead‐Free Formamidinium Tin Triiodide Perovskite Solar Cells via a Sequential Deposition Route

   https://doi.org/10.1002/adma.201703800  

   Zhu, Zonglong ; Chueh, Chu‐Chen ; Li, Nan ; Mao, Chengyi ; Jen, Alex K. ‐Y. ( December 2017 , Advanced Materials)

   Recently, the evolved intermediate phase based on iodoplumbate anions that mediates perovskite crystallization has been embodied as the Lewis acid–base adduct formed by metal halides (serve as Lewis acid) and polar aprotic solvents (serve as Lewis base). Based on this principle, it is proposed to constitute efficient Lewis acid–base adduct in the SnI₂deposition step to modulate its volume expansion and fast reaction with methylammonium iodide (MAI)/formamidinium iodide (FAI) (FAI is studied hereafter). Herein, trimethylamine (TMA) is employed as the additional Lewis base in the tin halide solution to form SnY₂–TMA complexes (Y = I⁻, F⁻) in the first‐step deposition, followed by intercalating with FAI to convert into FASnI. It is shown that TMA can facilitate homogeneous film formation of a SnI₂(+SnF₂) layer by effectively forming intermediate SnY₂–TMA complexes. Meanwhile, its relatively larger size and weaker affinity with SnI₂than FA+ ions will facilitate the intramolecular exchange with FA+ ions, thereby enabling the formation of dense and compact FASnI₃film with large crystalline domain (>1 µm). As a result, high power conversion efficiencies of 4.34% and 7.09% with decent stability are successfully accomplished in both conventional and inverted perovskite solar cells, respectively.

    

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