Correction: A chelated borinium cation.

Correction for 'A chelated borinium cation' by Christopher Major et al., Dalton Trans., 2024, 53, 10075-10078, https://doi.org/10.1039/D4DT01242A.

A chelated borinium cation.

Two coordinate boron cations are rare. Herein we report the synthesis of [RNSiMe2CH2]2BF (R = Dipp 3, 1-Ad 5) (Dipp = C6H3(iPr)2, Ad = C10H15) via the reaction of BF3 with the corresponding dilithiated diamides. Subsequent abstraction of fluoride provided the corresponding borinium salts, [(RNSiMe2CH2)2B][B(C6F5)4] (R = Dipp 6, 1-Ad 8). While the former was generated, the latter proved isolable and was crystallographically characterized.

Fluorination/Dearomatization of C6F5 Groups: An FLP Route to an Electrophilic Borane and Non-Coordinating Anions.

B(C6F5)3 and the corresponding anion [B(C6F5)4]- are ubiquitous in main group and transition metal chemistry. Known derivatives are generally limited to the incorporation of electron donating substituents. Herein we describe electrophilic fluorination and dearomatization of such species using XeF2 in the presence of BF3 or Lewis acidic cations. In this fashion the anions [HB(C6F5)3]-, [B(C6F5)4]- and [(C6F5)3BC≡NB(C6F5)3]-, are converted to [FB(C6F7)3]-, [B(C6F7)4]-, and [(C6F7)3BC≡NB(C6F7)3]-, respectively. Similarly, the borane adducts (L)B(C6F7)3 (L=MeCN, OPEt3) are produced. These rare examples of electrophilic attack of electron deficient rings proceed as [XeF][BF4] acts as a frustrated Lewis pair effecting fluorination and dearomatization of C6F5 rings.

Triple para-substitution reactions of B(C6F5)3 and [(C6F5)3PF]+ with P(SiMe3)3.

para-Substitution reactions on C6F5 rings of Lewis acids have been exploited to achieve triply substituted derivatives. The reaction of B(C6F5)3 with P(SiMe3)3 ultimately affords the Lewis acid B(C6F4P(SiMe3)2)31. This species binds Lewis bases affording the adducts LB(C6F4P(SiMe3)2)3 (L = MeCN 2, OPEt33, PMe34, PBu35) and reacts with LiMe to give the salt [Li][MeB(C6F4P(SiMe3)2)3]·3THF 6. It also reacts with H2O to give (L)B(C6F4PH2)3 (L = H2O 7, MeCN 8). In an analogous fashion, [(C6F5)3PF][B(C6F5)4] was converted to [FP(C6F4P(SiMe3)2)3] [B(C6F5)4] 9 and subsequently to [(MeO)P(C6F4PH2)3][B(C6F5)4] 10.

Synthesis and Reactivity of the [NCCCO]- Cyanoketenate Anion.

Cyanoketene is a fundamental molecule that is actively being searched for in the interstellar medium. Its deprotonated form (cyanoketenate) is a heterocumulene that is isoelectronic to carbon suboxide whose structure has been the subject of debate. However, the investigation of cyanoketene and its derivatives is hampered by the lack of practical synthetic routes to these compounds. We report the first synthesis of the cyanoketenate anion in [K(18-crown-6)][NCCCO] (1) as a stable molecule on a multigram scale in excellent yields (>90 %). The structure of this molecule is probed crystallographically and computationally. We also explore the protonation of 1, and its reaction with triphenylsilylchloride and carbon dioxide. In all cases, anionic dimers are formed. The cyanoketene could be synthesized and crystallographically characterized when stabilized by a N-heterocyclic carbene. The cyanoketenate is a very useful unsaturated building block containing N, C and O atoms that can now be explored with relative ease and will undoubtedly unlock more interesting reactivity.

Addition and NN bond cleavage of diazo-compounds by phosphino-phosphenium cations.

The phosphino-phosphenium cation (PPC) [Ph3PPPh2][GaCl4] reacts as a frustrated Lewis pair to add across the NN bond of (tBuO2CN)2. In contrast, photolytical addition [Ph2ClPPPh2][GaCl4] to (RN)2 results in cleavage of the NN bond affording [Ph2P(µ-NR)2PPh2Cl][GaCl4] (R = Ph 2, C6H4Cl3). While the chloride of 2 is replaced with N3 or CN via reaction with Me3SiN3 or tBuNC respectively, reaction with (C6F5)2BH effects ring opening to give [HN(Ph)PPh2(µ-NPh)PPh2][GaCl4] 7. This reactivity demonstrates that PPCs behave as FLPs to effect either addition or cleavage of NN double bonds.

Boron diamide derivatives containing N-N and N-P molecular fragments.

The cationic and neutral boron-diamide precursors are employed to target the inclusion of N2 and N-P molecular fragments. The species (HCN(Dipp))2BNH25, and (H2CN(Dipp))2BNH26 were prepared. While efforts to oxidize with [NO]+ gave mixtures of products, reactions with N2H4 gave the salts [(HCN(Dipp))2B(NHNH3)][O3SCF3] 7 [(H2CN(Dipp))2B(NHNH3)][O3SCF3] 8. Excess N2H4 gave the neutral species (HCN(Dipp))2B(NHNH2) 9 and (H2CN(Dipp))2B(NHNH2) 10, respectively. The species (H2CN(Dipp))2B(N3) 11 was prepared for comparative purposes. Turning to related NP species, compound 6 was converted to (HCN(Dipp))2B(NHPCl2) 12, while (HCN(Dipp))2BNK(SiMe3) 14 was used to give (HCN(Dipp))2BN(SiMe3)PCl215. Replacement of one of the chlorides gave (HCN(Dipp))2BN(SiMe3)PCl(OSO2CF3) 16 which converts to [(HCN(Dipp))2BNPCl]217. Similarly heating 15 afforded 17. The insights for the synthesis of further boron-N2 and boron-NP derivatives are discussed.

The impact of Lewis acid variation on reactions with di-tert-butyl diazo diesters.

Reactions of (tBuO2CN)2 with Lewis acids and FLPs have previously been shown to prompt the formation of diazene compounds. In this work, we show that the reaction of (tBuO2CN)2 with 9-BBN leads to a bicyclic heterocyclic product (tBuOCO(BBN)CN)21. In contrast, the reactions of (tBuO2CN)2 with BF3 or [Et3Si][B(C6F5)4] lead to the isolation of [tBuNHNH2tBu][BF4] 2 and [tBuN(H)NtBu][B(C6F5)4] 3, respectively. The mechanism for the formation of 2 is probed computationally, demonstrating that steric and electronic considerations of the Lewis acid impact the reaction pathway.

Coordination chemistry and FLP reactivity of 1,1- and 1,2-bis-boranes.

Coordination chemistry and frustrated Lewis pair (FLP) chemistry have been most commonly studied using monodentate Lewis acids. In this paper, we examine the corresponding reactions employing the 1,1- and 1,2-bis-boranes, PhCH2CH(B(C6F5)2)21 and Me3SiCH(B(C6F5)2)CH2B(C6F5)22, respectively. Coordination of isocyanide to these species results in the formation of the products RCH(B(C6F5)2CNtBu)CH2(B(C6F5)2CNtBu) (R = Ph 3, Me3Si 4). The rearrangement of 1 to give the 1,2-bis-borane adduct 3 was probed and attributed to a donor-induced retrohydroboration and subsequent hydroboration. The analogous reaction of 1 is evident in efforts to use the Gutman-Beckett method to assess its Lewis acidity. However, in combination with tBu3P, bis-boranes 1 and 2 form FLPs and react with H2 to give [tBu3PH][PhCH2CH(B(C6F5)2)2(µ-H)] 5a and [tBu3PH][Me3SiCH(B(C6F5)2)CH2(B(C6F5)2)(µ-H)] 6, respectively. Reactions of 1 and 2 with various donors and PhCCH were shown to give deprotonation and addition products, depending on the nature of the base. However, in the case of 1, products resulting from retrohydroboration, and subsequent hydroboration are evident. Several of these alkyne products are crystallographically characterized.

The Lewis superacidic aluminium cation: [(NHC)Al(C6F5)2].

The aluminium salt [(NHC)Al(tol)(C6F5)2][B(C6F5)4], (NHC = C3H2(N(iPr2C6H3))2) is shown to behave as a Lewis superacid as it abstracts fluoride from [SbF6]-. It also acts as a Lewis acid catalyst for hydrosilyation, hydrodefluorination and Friedel-Crafts reactions.

B(C6F5)3-catalyzed hydrogermylation of enones: a facile route to germacycles.

Organogermacycles are important skeletons for medicinal chemistry and materials. Herein, we reported a B(C6F5)3 mediated domino hydrogermylation reaction of enones with dihydrogermanes, affording 21 variants of organogermacycle compounds. These germacyclic compounds were obtained in good to excellent yields (up to 99% yield) under mild reaction conditions.

Borane catalyzed transesterification of tert-butyl esters using α-aryl α-diazoesters.

The B(C6F5)3-catalyzed transesterification of a series of 3-alkenyl-oxindoles and other unsaturated tert-butyl esters with aryl-diazo esters is reported. This protocol is facile and generally high yielding proceeding under mild conditions and is remarkably chemoselective leaving the CC bonds intact.

Phosphino-Phosphination Reactions: Frustrated Lewis Pair Reactivity of Phosphino-Phosphonium Cations with Alkynes.

The phosphino-phosphonium cations of the form [R3 PPR'2 ]+ are labile and provide access to the constituent Lewis acidic and Lewis basic fragments. This permits frustrated Lewis pair-type addition reactions to alkynes, affording unprecedented phosphino-phosphination reactions and giving cations of the form [cis-R3 PCHC(R'')PR'2 ]+ . This reactivity is further adapted to prepare several examples of a rare class of dissymmetric cis-olefin-linked bidentate phosphines.

Correction: Stannyl phosphaketene as a synthon for phosphorus analogues of ß-lactams.

Correction for 'Stannyl phosphaketene as a synthon for phosphorus analogues of ß-lactams' by Yong-an Luo et al., Chem. Commun., 2023, https://doi.org/10.1039/d3cc03117a.

Stannyl phosphaketene as a synthon for phosphorus analogues of ß-lactams.

The reaction of the stannyl phosphaketene (Nacnac)SnPCO 1 (Nacnac = CH{(CMe)(2,6-iPr2C6H3N)}2) with B(C6F5)3 produced the 1,4-addition product of (Nacnac)SnPCO(B(C6F5)3). However, the corresponding reactions in the presence of dimethyl maleate, diisopropyl fumarate or diethyl-but-2-ynedioate gave [2+2] addition yielding four-membered phosphacycles, ((Nacnac)Sn(MeO2C))CHPC(OB(C6F5)3)CH(CO2Me), [(C6F5)3B)PC(OSn)C(CO2Me)CH(CO2Me)]2, (Nacnac)Sn(iPrO2C)CC(OAl(C6F5)3)P[CH(CO2iPr)CH2(CO2iPr)]CH(CO2iPr), and (Nacnac)SnP (EtO2CCC(CO2Et))CO(B(C6F5)3), respectively. In contrast, the corresponding reaction of phenylacetylene gave the FLP-addition product (Nacnac)SnOC(P)C(Ph)CH(B(C6F5)3). Collectively, this reactivity demonstrates that the stannyl phosphaketene 1 can act as a synthon for P-analogues of ß-lactam derivatives.

NOVELTY AND PHYLOGENETIC RELATIONSHIPS WITHIN THE SERENDIPEIDAE (CESTODA: "TETRAPHYLLIDEA").

Nanoduplicibothrium n. gen. is erected for the subgroup containing the smallest members of the "tetraphyllidean" family Serendipeidae with bothridia fused lengthwise in 2 pairs that lack both a distinct row of posterior loculi and a cephalic peduncle. Two new species in this genus are described. These are Nanoduplicibothrium leanneae n. gen. n. sp. from Rhinoptera bonasus off South Carolina and Nanoduplicibothrium megaphallum n. sp. from Rhinoptera jayakari off Mozambique. Two species currently assigned to Duplicibothrium are transferred to the new genus as Nanoduplicibothrium paulum n. comb and Nanoduplicibothrium jillae n. comb. and the diagnosis of Duplicibothrium is emended so that it aligns with the revised membership of the group. Duplicibothrium bilai n. sp. is also described from R. jayakari off Mozambique. The description of these species provides formal names for 3 species included in previously published molecular phylogenetic work under the provisional names Duplicibothrium n. sp. 2, Duplicibothrium n. sp. 4, and Duplicibothrium n. sp. 5, respectively. Erection of the new genus substantially reduces the number of instances of congeners in the family parasitizing the same host species because in most instances the pairs of species now represent 1 species each in Nanoduplicibothrium and Duplicibothrium. Sequence data for the D1-D3 region of the 28S rDNA gene were generated for Serendip for the first time from an undescribed species from Aetomylaeus asperrimus collected off Panama. This finding also expands the known host associations of the Serendipeidae beyond the Rhinopteridae to include a species of Myliobatidae. A maximum-likelihood phylogenetic analysis of all species of serendipeids for which data for the D1-D3 region of the 28S rDNA gene are available confirms the reciprocal monophyly of Nanoduplicibothrium, Duplicibothrium, and Serendip. The phylogenetic placement of the fourth genus in the family-the monotypic Glyphobothrium-remains to be determined.

Electron-deficient cyclopropenium cations as Lewis acids in FLP chemistry.

Cyclopropenium cations incorporating electron deficient substituents are Lewis acidic despite the presence of π-electrons. The chloride and electron affinities are examined computationally and experimentally, respectively. These cations form classic Lewis acid-base adducts with PPh3, while sterically demanding phosphines yield frustrated Lewis pairs (FLPs) which participate in FLP additions. Depending on the basicity of the phosphine used, addition to alkynes or alkyne deprotonation is observed. In either case, new C-C bonds are formed, thus extending the utility of the concept of FLP chemistry to these delocalized π-cations.

Frustrated Lewis pair chemistry of CO.

Transition metal species readily capture and react with CO as the metal can act both as an acceptor and donor of electron density. In contrast, such a situation is less common in the main group and thus far fewer examples of main group CO adducts and their subsequent reactivity have been studied. In this review, we focus on the application of the concept of Frustrated Lewis Pairs (FLPs) to develop main group chemistry of CO. Specifically, we address reactions of FLPs that illustrate the ability to capture CO in addition to subsequent reactivity involving reduction with a variety of reagents. These developments illustrate that the donation and acceptance of electron density provided by FLPs is an alternative strategy to advance the reactivity of CO. Such insights augur well for future advances in the homogeneous chemistry of CO.

Reactivity of frustrated Lewis pairs with BOC protected diazocarboxylates: FLP capture of diazene.

Reactions of (tBuO2CN)2 with FLPs are examined. B(C6F5)3 interacts with the carbonyl oxygen atoms inducing loss of CH2CMe2; however, in the presence of basic donors, the protons are intercepted affording the salts [Hbase]2 [((C6F5)3BO2CN)2] (base = tBu3P 1, NC5H2Ph32, HNC5H6Me43). In contrast, in the presence of (o-Tol)3P, a proton transfers to the diazo-N atom affording (o-Tol)3PN(CO2tBu)NHB(C6F5)34. Further addition of B(C6F5)3 to 4 prompts loss of olefin CH2CMe2 and CO2 affording (o-Tol)3PNHNHB(C6F5)35. The course of these reactions is examined by extensive DFT calculations. The nature of 5 is consistent with the FLP reduction of a diazene fragment.

Reactive FLP-alkyne addition products: a route to anionic and zwitterionic phosphines.

Combination of a phosphinidene precursor, B(C6F5)3 and 4-ethynyltoluene afforded the FLP addition product, Et2N(C14H10)PC(Tol)CH (B(C6F5)3) 2. Compound 2 reacted with halides, pseudo-halides or Me3SiSPh to provide a facile route to the salts of anionic phosphines while reaction with PEt3 gave the zwitterion Et3PCHC(SiMe3)P(NEt2)C(Tol)CHB(C6F5)38. This latter species reacted with an alkyne to give a phosphine donor with both olefin-linked cationic and anionic substituents.