Carbonyl Hypoiodites as Extremely Strong Halogen Bond Donors

This is a sel -a chi ed e sion o an o iginal a icle. This e sion may di e om he o iginal in pagina ion and ypog aphic de ails. Au ho (s): Ti le: Yea : Ve sion: Copy igh : Righ s: Righ s u l: Please ci e he o iginal e sion: CC BY-NC 4.0 h ps://c ea i ecommons.o g/licenses/by-nc/4.0/ Ca bonyl Hypoiodi es as Ex emely S ong Halogen Bond Dono s © 2021 The Au ho s. Angewand e Chemie In e na ional Edi ion published by Wiley-VCH GmbH Published e sion Yu, Shilin; Wa d, Jas S.; T uong, Khai-Nghi; Rissanen, Ka i Yu, S., Wa d, J. S., T uong, K.-N., & Rissanen, K. (2021). Ca bonyl Hypoiodi es as Ex emely S ong Halogen Bond Dono s. Angewand e Chemie, 60(38), 20739-20743. h ps://doi.o g/10.1002/anie.202108126 2021 Halogen Bonding Ca bonyl Hypoiodi es as Ex emely S ong Halogen Bond Dono s Shilin Yu, Jas S. Wa d, Khai-Nghi T uong, and Ka i Rissanen* Abs ac : Neu al halogen-bonded OIN complexes we e p epa ed om in si u o med ca bonyl hypoiodi es and a oma ic o ganic bases. The ca bonyl hypoiodi es ha e a s ongly pola ized iodine a om wi h la ge s-holes han any known uncha ged halogen bond dono . Modula ing he Lewis basici y o he selec ed py idine de i a i es and ca boxyla es leads o halogen-bonded complexes whe e he classical OI···N halogen bond ans o ms mo e in o a halogen-bonded COO···IN+ion-pai (sal ) wi h an asymme ic OIN moie y. X- ay analyses, NMR s udies, and calcula ions e eal he halogen bonding geome ies o he ca bonyl hypoiodi e- based OIN complexes, con i ming ha in he solid-s a e he iodine a om is much close o he N-a om o he py idine de i a i es han i s o iginal posi ion a he ca boxyla e O-a om. Halogen bonding (XB) has become one o he mos s udied non-co alen in e ac ions, mo e speci ically elec ophile- nucleophile in e ac ions, as demons a ed by he apid inc ease o publica ions since 2007.[1–8] Halogen bonding has ecen ly been de ined o occu be ween halogens being elec ophilic and neu al o anionic nucleophiles.[9] Despi e ongoing deba e abou he ue na u e o he halogen bonding,[10–13] i is equen ly used as a non-co alen in e ac ion o cons uc sup amolecula complexes. Owing o he simila i y o he bonding geome ies and di ec ionali y i s kinship wi h hyd ogen bonding is mo e han e iden . Halogen bonding has been success ully applied o con ol he sel - assembly o a mul i ude o hos –gues sys ems (ion-pai ecogni ion, biomolecula /chemical sepa a ions), as well as he syn hesis o unc ional ma e ials (po ous, magne ic, phospho escen , liquid c ys als).[1,2] C ys al enginee ing,[1–4,14] he o igin o halogen bonding, es ablished he di ec ionali y, and speci ici y esul ing in complex s uc u es wi h appealing a chi ec u es. Owing o he demand o e y p ecise design p inciples, hollow capsula molecula assemblies solely based on halogen bonding ha e only e y ecen ly been p e- pa ed.[15,16] Owing o i s na u e, halogen bonding is mo e di ec ional han hyd ogen bonding,[17] ye i is much mo e di icul o s udy in solu ion and has he e o e been demon- s a ed mos ly in he solid-s a e.[18–21] When an elec on is emo ed om he halogen a om, i becomes a posi i ely cha ged ee ion, a halenium ion X+ (X=I, B o Cl). These ca ions can be ega ded as e y s ong bis- unc ional XB dono s, hough he eac i i y o he ee halenium ion e ec i ely p e en s hei use as such. Howe e , by applying sui able Lewis bases in he syn hesis, he halenium ions can be apped in o a [LXL]+complex exhibi ing a h ee-cen e - ou -elec on (3c-4e) bond. Fi s o hese, namely he iodonium bis(py idine) complexes wi h a[N IN]+3c-4e bond, we e epo ed in he 1960s by Hassel e al.,[22] C ich on e al.,[23] and Hague e al.[24] They ha e a ac ed a lo o a en ion, especially wi hin he halogen bonding communi y and ha e ecen ly been e iewed.[25,26] The iconic example, bis(py idine)iodonium(I) e a luo obo- a e, Ba luengas eagen ,[27] is a mild iodina ion eagen and an oxidan . Ba luengas eagen is a ela i ely s able whi e solid and is soluble in bo h o ganic and aqueous solu ions, and i s applicabili y in o ganic syn hesis has been widely demon- s a ed.[28] E dlyi[29–34] has demons a ed ha he [NIN]+ halogen bond by e y p ecise and comp ehensi e s udies in solu ion, supplemen ed wi h compu a ional calcula ions con- i ming ha he [NIN]+halogen bond is symme ic wi h he iodine a om loca ed in he cen e be ween he N-a oms. The anionic analogue [OIO], iz. dioxoiodane compounds, ha e ecen ly applied as eagen s in o ganic syn hesis.[35] The mos s udied o he Ba luenga- ype halonium ion complexes[36–39] a e he symme ical [NXN]+(X =B o I) complexes.[24,27] Asymme ic he e olep ic halonium com- plexes ha e been p epa ed by E dlyi and co-wo ke s,[30] wi h he help o molecula cle s. Only e y ecen ly he i s un es ained he e olep ic [N1IN2]+complexes ha e been epo ed in he solid-s a e[40] and solu ion.[41] Apa om he abo e men ioned cha ged XB complexes, also neu al NI···N and NI···ON XB complexes a e easily p epa ed om sui able haloimides and halosul onimides as he XB dono s and py idine de i a i es o py idine-N-oxides as he XB accep o s, ex ensi ely s udied by Fou migu[42,43] and Rissanen.[19–21,44] Inspi ed by he abo e-men ioned wo k, we sough o p obe he RCOOI molecules, namely ca bonyl hypoio- di es, as a po en ial new mo i o halogen bond dono s. To he bes o ou knowledge, ca bonyl hypoiodi es which we e s abilized by py idine we e i s s udied by Ca lsohn in his habili a ion in 1932.[45] In 1940s, Kleinbe g, Zinga o and co- wo ke s epo ed he p epa a ion o a se ies o iodine(I) sal s by he eac ion o di e en sil e ca boxyla es and iodine in he p esence o py idine, 2-picoline o 4-picoline as he s abilizing ligand.[46–49] Some o hese sal s we e e ec i ely u ilized as iodina ion eagen s wi h in e es ing an ibac e ial p ope ies.[43] Fu he mo e, he wo known single c ys al [*] D . S. Yu, D . J. S. Wa d, D . K.-N. T uong, P o . K. Rissanen Depa men o Chemis y, Uni e si y o Jy askyla Su on ie 9 B, 40014 Jy skyl (Finland) E-mail: ka i. . issan[email p o ec ed] Suppo ing in o ma ion and he ORCID iden i ica ion numbe (s) o he au ho (s) o his a icle can be ound unde : h ps://doi.o g/10.1002/anie.202108126.  2021 The Au ho s. Angewand e Chemie In e na ional Edi ion published by Wiley-VCH GmbH. This is an open access a icle unde he e ms o he C ea i e Commons A ibu ion Non-Comme cial License, which pe mi s use, dis ibu ion and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed and is no used o comme cial pu poses. A ngewand e Chemi e Communica ions How o ci e: In e na ional Edi ion: doi.o g/10.1002/anie.202108126 Ge man Edi ion: doi.o g/10.1002/ange.202108126 1Angew. Chem. In . Ed. 2021,60, 1 – 6  2021 The Au ho s. Angewand e Chemie In e na ional Edi ion published by Wiley-VCH GmbH These a e no he inal page numbe s! Ü Ü s uc u es mani es ing py idine benzoyl hypoiodi e 1b [named as benzoa o-py idine-iodine(I)] and bis-py idine ph haloyl hypoiodi e [ph hala o-bis(py idine-iodine(I)], we e epo ed 40 yea s ago by Ha l.[50] In addi ion o hei syn- hesis,[27] use o s uc u ally ela ed anionic complexes [RCOOI OOCR], which should be con- side ed as he anionic- ype 3c-4e XB complexes wi h wo oxygen a oms as XB accep o s,[25] ha e been u ilized as dynamic axles in he cons uc ion o o axanes.[51] He ein, we epo he in es i- ga ions on neu al OIN com- plexes, ea ed as new examples o halogen-bonded complexes, whe e he ca bonyl hypoiodi es ac as XB dono s. The esul s clea ly show ha ca bonyl hypoiodi es a e e y p omising as s ong halogen bond dono s, gi ing unambiguous NMR spec a and mani es ing e y s ong sal -like cha ac e (a leas in he solid-s a e) whe e he iodine has jumped om he ca boxyl oxygen o he N-a om o he py idine de i a i e o ming a e y s ongly halogen-bonded [RCOO][+IN(py)] ion-pai . The syn hesis ou e o he neu al hypoiodi e OIN complexes is illus a ed in Scheme 1.[47,49] Cha ac e iza ion and de ails o he syn hesis and he NMR s udies o all wel e hypoiodi e complexes (1b,1d,2a–2d,3a,3b,3d,4a,4band 4d) om py idine and i s selec ed de i a i es, sil e ca box- yla es, and elemen al iodine a e p esen ed in he Suppo ing In o ma ion (SI). The 15N NMR chemical shi alues based on he 1H-15N HMBC measu emen s (SI) o he py idinic ni ogen o 2a–2d and ee ligand 2a e summa ized in he Table 1. The complexa ion-induced chemical shi change, DdN, de ined as d(15NOIN)d(15NL), wi h OIN as he halogen-bonded complexes and Las ee 1–4, is e y la ge and mani es s a d ama ic change in he chemical en i onmen o he py idinic N-a om du ing he complexa ion. Wi h inc easing Lewis basici y o he ca boxyla es he DdNinc eases. The s able N-me hyl-DMAP ca ion [2CH3]+, as he PF6sal , has aDdNbe ween 2c and 2d (Table 1). Compa ed wi h he co esponding i luo oace a e sal o DMAP ([2H]TFAc), he hypoiodi e complex 2dhas a much la ge DdN(129.4 s. 85.6 ppm, Table S1), which indica es a bigge inc ease o he elec on densi y a ound py idinic ni ogen in 2d.[52,53] The DdNo h ee benzoa e-based OIN complexes (1b, 2band 3b) was also compa ed, as shown in Table 1. When he nucleophilici y o he used base inc eases, he la ge he 15N NMR chemical shi change. The complex 1bhas he smalles 15N NMR chemical shi change alue, which is s ill bigge han ha o py idinium i luo oace a e ([1H]TFAc) (81.0 s. 70.0 ppm, Table S1). The single c ys als o he complexes 1b,2a,2b,2c,2d,3b, 3d,4a and 4d we e g own ei he om dichlo ome hane o chlo o o m upon slow e apo a ion o by apo di usion o pen ane, die hyl e he o pe oleum e he in o dichlo o- me hane, chlo o o m o ace oni ile. The c ys allog aphic de ails a e p esen ed in he SI (Table S1). The DMAP- (2a, 2b,2c, and 2d) and benzoa e-based (1b,2b, and 3b)O IN complexes will be discussed as wo di ec ly compa able se ies o complexes. The OI bonds o 2a,2b and 2c (Table 1, Figu e 1) a e e y simila o each o he (ca. 2.21 ) and iden ical o he OIO bonds (c . 2.20 ) in he anionic dioxoiodane complexes.[35] The IN bond dis ances (Table 1) o 2a,2b, and 2c a e all equal (ca. 2.23 ) and e y much esemble hose obse ed o p e iously epo ed 3c-4e [NI N]+halogen-bonded iodonium complexes.[22,37,40,54,55] A no a- ble excep ion is he 2d whe e he IN bond leng h o 2.173(4)  is much oo sho o be a con en ional 3c-4e halogen bond. The iodine is abou 0.08  close o he py idinic ni ogen in 2d han in a ypical halonium ion [NI N]+complex and 0.04  close han in he NISac-DMAP (2- NISac) (inne )-sal complex epo ed by Fou migu (c . 2.218(2) ).[34] Apa om he sho IN bond in 2d, he OI bond is elonga ed by 0.323  om he 1.989  ob ained om he DFT calcula ions o he hypoiodi e d(SI, Table S1) e sus 2.312(4)  om he SCXRD. This alue is analogous o he s onges I···O halogen bonds obse ed in N-iodosaccha in- py idine-N’-oxide halogen-bonded complexes,[19–21,44] and hus he OI bond in 2d is be e desc ibed as an I···O halogen Scheme 1. Syn hesis o he OIN complexes, wi h DMAP (2) and Ag- benzoa e gi en as an example (2b). Table 1: The OI and IN dis ances om SCXRD and DFTs udies and he 15N NMR chemical shi s o 1b,2,2a–2d,3b,[2CH3]PF6,[2I2]PF6, and 2-NISac. Complex d(OI) [] (XRD/DFT) d(IN) [] (XRD/DFT) d15N[b] [ppm] Dd[c] [ppm] 1b 2.159(5)/2.133 2.299(7)/2.301 148.7 81.0 2––108.6 – 2a 2.203(11)/2.15 2.234(14)/2.27 204.7 96.1 2b 2.210(3)/2.171 2.241(3)/2.247 209.5 100.9 2c 2.21(1)[a]/2.18 2.22(1)[a]/2.24 212.2 103.6 2d 2.312(4)/2.248 2.173(4)/2.189 238.0 129.4 [2CH3]PF6––224.0 115.4 [2I2]PF6––216.1 107.5 2-NISac[42] 2.292(2)[d]/2.314 2.218(2)/2.247 200.8 92.2 3b 2.230(4)/2.164 2.232(4)/2.2.257 202.1 102.5 [a] A e age o ou c ys allog aphically independen complexes in he asymme ic uni . [b] The 1H-15N HMBC NMR chemical shi o py idinic ni ogen in [OIN] complexes o ee ligands in CD2Cl2. [c] The 15N NMR chemical shi change upon complexa ion. [d] (Sac)NI bond leng h. A ngewand e Chemi e Communica ions 2www.angewand e.o g  2021 The Au ho s. Angewand e Chemie In e na ional Edi ion published by Wiley-VCH GmbH Angew. Chem. In . Ed. 2021,60,1–6 Ü Ü These a e no he inal page numbe s! bond. The OIN bond leng hs in he solid-s a e o 2d suppo i s desc ip ion as an ion-pai o he N-iodo-N’,N’- dime hylaminopy idinium ca ion, and a i luo oace a e anion, s abilized by a e y s ong N+I···OC halogen bond. The sho es IN bond o 2.167(4)  was obse ed o complex 4d, and simila ly, he longes IO bond leng h was o 2das p e iously s a ed, hough i ually he same as in 4d(c . 2.308(4) ). Consis en wi h he gene al linea i y o halogen bonds, he angles o he OIN moie ies in all hypoiodi e complexes all wi hin he ange o 172.9(5)–178.1(1) 8 and a e close o he halogen bond angles obse ed o he N-iodosaccha in- py idine-N’-oxide halogen-bonded complexes[19–21,44] han o he s ic ly linea 3c-4e [NIN]+halogen bonds.[22,37,40,54,55] The SCXRD da a o 2a–2d demons a es he dynamic bonding si ua ion o he OIN moie y, wi h sho e IN bond leng hs e lec ing an inc ease in he N-iodopy idinium cha ac e o he py idine de i a i e, concomi an ly wi h an elonga ion o he OI bond leng h e lec ing an inc ease in he anionic cha ac e o he ca boxyla e componen . As expec ed, subs i u ed py idines such as DMAP (2) and 4- pipe idinopy idine (4), ha a e s onge nucleophiles, a e be e able o induce his inc eased N-iodopy idinium cha - ac e in he OIN complexes desc ibed he ein. Es ima ion o he N-iodopy idinium cha ac e is di icul as no N- iodopy idinium ca ion X- ay s uc u e is known (only he N- luo opy idinium ca ion is known).[56] In he 3c-4e [NI N]+halogen-bonded symme ic halonium complex [2I 2]PF6, he ela i e N-iodopy idinium cha ac e can be con- side ed o be 50% (NI: 2.250 , NN: 4.500 ),[36,40,57] while o he [2I]+ca ion he IN bond dis ance can only be ob ained wi h compu a ional me hods (SI, sec ion 3). The DFT compu ed alue o he IN bond dis ance in [2I]+is 2.042 . Using hese wo alues and he SCXRD measu ed I N dis ances, he ela i e N-iodopy idinium cha ac e can be es ima ed o he Fou migu epo ed 2-NISac complex[34] (56.5%), 2d (67.6%), 3d (62.4%) and 4d (69.1%) in he solid-s a e. Due o he dynamic na u e[51] o he OIN moie y in solu ion, no clea co ela ion abou he N-iodopy - idinium cha ac e in he solid-s a e and in solu ion can be gi en. When keeping he i luo oace yl hypoiodi e moie y cons an bu changing he py idine moie y, namely complexes 2d,3d, and 4d, no appa en di e ences in he halogen bonding geome ies we e obse ed, as in all complexes he OI(2d: 2.312(4) , 3d: 2.282(5) , 4d: 2.308(4)) , he IN bond dis ances (2d: 2.173(4) , 3d: 2.194(5) , 4d: 2.167- (4) ) and he OIN angles (2d: 175.5(2) 8 ,3d: 172.1(2) 8 , 4d: 175.0(1) 8 ) a e e y simila . This is e y likely due o he ac ha all 2,3and 4a e e y s ong Lewis bases and ac as e y s ong XB dono s enhancing he ion-pai o ma ion in he solid-s a e. Fo compa ison o he halogen bonding geome ies om he SCXRD and DFT calcula ions (SPARTAN’18,[58] M06- 2X, de 2-TZVP) wi h non-pola sol en model (DCM) we e pe o med. The de ailed expe imen al SCXRD and calcu- la ed DFT geome ies a e gi en in SI (Table S1). The DFT calcula ed bond geome ies a e ex emely close o hose expe imen ally de e mined by SCXRD. This is a con incing p oo ha he compu a ional alues ob ained o he non- single c ys alline complexes a e easible and can be used o discuss he dynamic bonding beha io o he OIN sys em. The hypoiodi es a–dshowed no end on he OI bond dis ance as in all cases i is 1.99  (DFT, Table S1). D as ic elonga ion o he OI bond occu s du ing he OIN complex o ma ion as he OI bond ge longe by 0.17– 0.34 , and co espondingly he IN bonds sho en (Table S1). The N···O dis ance in all OIN complexes also emains i ually unchanged (4.43–4.48 ). The molecula elec os a ic su ace po en ial maps (MEPS, Figu e 2) o he hypoiodi es a–d e eal e y la ge s-holes, anging om +170.41 kJmol1(a) o +234.55 kJmol1(d). Due o he s ong pola izing powe o he ca boxyla e moie y hese alues a e la ge when compa ed o some common s ong halogen bond dono s like i luo - oiodome hane (+139.50 kJmol1), iodoace ylene (+165.47 kJmol1), ICl (+182.41 kJmol1) and N-iodosac- cha in (+226.36 kJmol1) (SI, Figu e S75). Figu e 1. The X- ay c ys al s uc u es o 2a,2b,2c and 2d ( op o bo om; he mal ellipsoids a 50% p obabili y).[59] Figu e 2. The elec os a ic po en ial su aces and he Vs,max (kJmol1) alues calcula ed a he M06-2X/6–311+G(3d ,2p) le el on he 0.001 a.u. molecula su aces o a–d. A ngewand e Chemi e Communica ions 3Angew. Chem. In . Ed. 2021,60, 1 – 6  2021 The Au ho s. Angewand e Chemie In e na ional Edi ion published by Wiley-VCH GmbH www.angewand e.o g These a e no he inal page numbe s! Ü Ü While he asymme ic OIN halogen-bonded hypoiodi e complexes a e s able (wi h a ew excep ions) unde no mal condi ions, hey can be p one o exchange eac ions o he co esponding posi i ely cha ged [LIL]+(L =Lewis base) halonium complex in he p esence o excess Lewis base, depending on he s eng h o he Lewis base and he ca boxyla e used. This is unambiguously p o en by a i a ion expe imen moni o ed by 1H NMR in d2-DCM (Figu e 3). The OIN hypoiodi e complex 2d (Figu e 3a) was i a ed wi h DMAP o p obe he displacemen o he TFAc anion. Gi en ha DMAP is a s ong nucleophile, i would be expec ed o eplace he TFAc anion o o m he [2I2]+ halonium complex. This indeed happens as, wi h he inc eas- ing amoun o DMAP, he signals o DMAP in 2d (g een colo ) g adually diminish, while new peaks (blue colo ) eme ge o he symme ic [2I2]+halonium complex (Fig- u e 3b– ). The 1H NMR spec um o a sepa a ely p epa ed [2I2]PF6halonium complex is shown in Figu e 3h o e e ence. A wo equi alen s o 2(Figu e 3g), i was obse ed ha he signals o 2d had nea ly comple ely disappea ed. In conclusion, a se ies o halogen-bonded OIN hypo- iodi e complexes ha e been syn hesized, and hei solid-s a e s uc u es in es iga ed, o p obe he dependency be ween he OI and IN bond leng hs and he Lewis basici y o he N- dono . The solid-s a e s udies e ealed ha hese OIN complexes can be desc ibed as a new class o halogen-bonded complexes, namely as a e y s ongly bound ion-pai com- p ised om an iodopy idinium ca ion and an anion de i ed om he espec i e acid used. The 1H–15N HMBC NMR s udies e eal a d as ic change in he chemical shi o he py idinic ni ogen a om in he complexes, especially hose om s ong acids, esul ing in a s able halogen-bonded complex. The compu a ional calcula ions suppo hei cha - ac e iza ion, e ealing e y la ge s-holes o he pa en hypoiodi es. The Vs,max alue (+234.55 kJmol1) o he i luo oace yl hypoiodi e su passed ha o he p e iously s onges neu al halogen bond dono molecule, N-iodosac- cha in (+226.36 kJmol1). The exchange eac ions o he hypoiodi e complex 2d (COOIN(2)) wi h excess o 2 esul s in he co esponding posi i ely cha ged [2I2]+ halonium complex, wi h COOas he anion. 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Sci. 2020,11, 7979–7990. [58] SPARTAN’18, Wa e unc ion Inc, I ine, Ca 92612, USA, 2018. [59] Deposi ion Numbe s 2068106 ( o 1b), 2068107 ( o 2a), 2068108 ( o 2b), 2068109 ( o 2c), 2068110 ( o 2d), 2068111 ( o 3b), 2068112 ( o 3d), 2068113 ( o 4a), and 2068114 ( o 4d) con ain he supplemen a y c ys allog aphic da a o his pape . These da a a e p o ided ee o cha ge by he join Camb idge C ys allog aphic Da a Cen e and Fachin o ma- ionszen um Ka ls uhe Access S uc u es se ice www.ccdc. cam.ac.uk/s uc u es. Manusc ip ecei ed: June 18, 2021 Accep ed manusc ip online: July 16, 2021 Ve sion o eco d online: && &&,&&&& A ngewand e Chemi e Communica ions 5Angew. Chem. In . Ed. 2021,60, 1 – 6  2021 The Au ho s. Angewand e Chemie In e na ional Edi ion published by Wiley-VCH GmbH www.angewand e.o g These a e no he inal page numbe s! Ü Ü Communica ions Halogen Bonding S. Yu, J. S. Wa d, K.-N. T uong, K. Rissanen* &&&& —&&&& Ca bonyl Hypoiodi es as Ex emely S ong Halogen Bond Dono s Ca bonyl hypoiodi es possess e y s ongly pola ized iodine a oms, includ- ing wha is now he la ges known s-hole o a neu al compound, and ac as s ong halogen bond dono s. When s ong Lewis bases, o example DMAP, a e used as halogen bond accep o s, he iodine a om, o all in en s and pu poses, ans e s om he oxygen o ni ogen a om o gi e an ion-pai o he gene al o m [RCOO]- [I+N(DMAP)] wi h an O···IN halogen bond. A ngewand e Chemi e Communica ions 6www.angewand e.o g  2021 The Au ho s. Angewand e Chemie In e na ional Edi ion published by Wiley-VCH GmbH Angew. Chem. In . Ed. 2021,60,1–6 Ü Ü These a e no he inal page numbe s!