Investigations on the Coupling of Ethylene and Alkynes in Tp Me2 Ir Compounds: Water as an Effective Trapping Agent

1 FULL PAPER DOI: 10.1002/chem.200((……)) In es iga ions on he Coupling o E hylene and Alkynes in TpMe2I Compounds: Wa e as an E ec i e T apping Agen Eleu e io Ál a ez,[a] Ma ga i a Paneque,*[a] C is ina M. Posadas,[a] Manuel L. Po eda,*[a] Nu ia Rendón,[a] and Ku Me ei e [b] Abs ac : The eac ion o he bis(e hylene) complex TpMe2I (C2H4)2 (1) (TpMe2 = hyd o is(3,5- dime hylpy azolyl)bo a e) wi h 2 equi . o dime hyl ace ylenedica boxyla e, MeO2CCCCO2Me (DMAD), in CH2Cl2 a 25 ºC gi es he hyd ide- alkenyl species Tp Me2 I H(C(R)=C(R)C(R)=C(R)CH=CH 2 ) (2, R = CO2Me) in high yield. A ca e ul s udy o his sys em has es ablished he ac i e ole o a numbe o in e media es in ou e o 2. The i s o hese is he I (I) complex TpMe2I (C2H4)(DMAD) (4) o med by subs i u ion o one o he e hylene ligands in 1 by a molecule o DMAD. 4 eac s u he wi h ano he equi alen o he alkyne wi h o ma ion o he unsa u a ed me allacyclopen adiene “ Tp Me2 I (C(R)=C(R)C(R)=C(R)) ” which can be apped by added wa e o gi e adduc 7, o eac wi h he C2H4 p esen in solu ion gene a ing complex 2. This las s ep has been shown o p oceed by inse ion o e hylene in o one o he I —C bonds o he me allacyclopen adiene and subsequen -H elimina ion. Complex 1 eac s sequen ially wi h 1 equi . o DMAD and 1 equi . o me hyl p opiola e, HCCCO2Me (MP), in he p esence o wa e , wi h egioselec i e o ma ion o he unsymme ical i idacyclopen adiene Tp Me2 I (C(R)=C(R)C(H)=C(R))(H 2 O) (9). Complex 9 eac s wi h e hylene gi ing a hyd ide-alkenyl complex 10, ela ed o 2, in which he C2H4 has inse ed egiospeci ically in o he I — C(R) bond ha bea s he CH unc ionali y. Hea ing CH2Cl2 solu ions o ei he 2 o 10 allows he o ma ion o he allyl species 3 o 11, espec i ely, by simple s e eoselec i e mig a ion o he hyd ide ligand in o he C alkenyl ca bon and concomi an bond eo ganiza ion o he esul ing o ganic chain. All he compounds desc ibed he ein ha e been cha ac e ized by mic oanalysis, IR, and NMR spec oscopy and o he case o 3, 7, 7·CO, 8·NCMe, 9, 9·NCMe and 10, also by single c ys al X- ay di ac ion s udies. Keywo ds: C-C coupling · i idacyclopen adienes · C2H4 inse ion · C-H ac i a ion · wa e complexes In oduc ion Me allacyclopen adienes[1] a e e y in e es ing o ganome allic species which a e in ol ed, as in e media es, in a numbe o impo an ca aly ic o s oichiome ic p ocesses media ed by ansi ion me al complexes, as is he case o he cyclo ime iza ion o alkynes ( o gi e benzene de i a i es),[2] alkynes-ni iles ( o he syn hesis o py idines),[3] alkynes-ole ins ( o ma ion o cyclohexadienes),[3,4] e c.[1h,5] In his con ibu ion, we epo on he coupling o wo molecules o DMAD (dime hyl ace ylenedica boxyla e, MeO2CC≡CCO2Me) in he TpMe2I sys em (TpMe2 = hyd o is(3,5-dime hylpy azolyl)bo a e),[6] o gi e an i idacyclopen adiene[7] which comple es he 18-elec on me al coun by coo dina ion o a molecule o wa e . Subs i u ion and inse ion eac ions o his complex ha e been in es iga ed, as well as he syn hesis and eac i i y o a ela ed unsymme ical i idacyclopen adiene ha esul s om he egioselec i e coupling o DMAD and MP (MP = me hyl p opiola e, HC≡CCO2Me). Pa o his wo k has been published in p elimina y o m.[8] Resul s and Discussion The addi ion o 2 equi . o DMAD o a solu ion o he bis(e hylene) complex TpMe2I (C2H4)2 (1)[9] in CH2Cl2, a oom empe a u e, p oduces immedia e consump ion o 1 and o ma ion o a new compound, 2, as deduced om he NMR spec a o he eac ion mix u e [Eq. (1)]. The eac ion is s e eospeci ic, and he spec oscopic yield o his species is highe han 85%. The chela ing [a] D . E. Ál a ez, D . M. Paneque, D . C. M. Posadas, P o . D . M. L. Po eda, D . N. Rendón, Ins i u o de In es igaciones Químicas and Depa amen o de Química Ino gánica Consejo Supe io de In es igaciones Cien í icas (CSIC) and Uni e sidad de Se illa A . Amé ico Vespucio 49, Isla de la Ca uja, 41092 Se illa (Spain) Fax: (+34)954460565 E-mail: [email protected] [b] D . K. Me ei e Depa men o Chemis y, Vienna Uni e si y o Technology, Ge eidema k 9/164, A-1060 Vienna (Aus ia) Suppo ing in o ma ion o his a icle is a ailable on he WWW unde h p://www.chemeu j.o g/ o om he au ho . 2 hyd oca byl-alkene ligand in compound 2 o mally esul s om he C—C coupling o wo molecules o DMAD and a inyl agmen , which de i es i sel om one o he e hylene ligands in 1. B NNN NNN I H [I ] = Tp Me2 I = CH 2 Cl 2, 25 °C [I ] R RR R 2 2DMAD [I ] 1 DMAD = RR (1) H -C 2 H 4 R=CO 2 Me Al hough compound 2 is he majo p oduc in his eac ion, a emp s o ob ain an analy ical and spec oscopically pu e sample o i ailed, due o i s slow ans o ma ion in o a new allyl de i a i e 3 (see below). Ei he by c ys alliza ion o by column ch oma og aphy, species 2 is always isola ed as a mix u e wi h 3. Ne e heless, i su i es in solu ion long enough as o be p ope ly cha ac e ized by spec oscopy, ei he in he mix u e wi h 3 o in he c ude p oduc om he eac ion. The p esence o he hyd ide ligand is shown by a high- ield esonance a -16.91 ppm in he 1H NMR spec um, while he π-coo dina ed inyl moie y exhibi s he pa e n o esonances expec ed o a ligand o his ype:[10] h ee mul iple s cen e ed a 6.39, 3.63 and 3.07 ppm, wi h ans and cis 3JHH coupling cons an s o 11.5 and 9.8 Hz, espec i ely (see Expe imen al Sec ion o assignmen s). 13C NMR da a and a ull se o wo-dimension expe imen s a e also in ag eemen wi h he s uc u e p oposed and, in pa icula , he NOESY spec um con i ms he coo dina ion o he ole in o he me al h ough he ace indica ed. Complex 2 cleanly ans o ms in o he alkyl-allyl 3 when solu ions o 2 a e wa med a 60 °C [Eq. (2)], and 3 is also ob ained, in almos quan i a i e yield, when he eac ion depic ed in Eq. (1) is pe o med in CH2Cl2 a 60 °C. The o ma ion o 3 is he nea esul o he s e eospeci ic ans e o he hyd ide ligand o he α-ca bon a om o he alkenyl end o he chela ing ligand in 2. Di e en pa hways could in p inciple be en isaged o his ans o ma ion; ne e heless, we p opose ha i akes place by di ec mig a ion o he hyd ide o he alkenyl ca bon, wi h conce ed o s epwise bond ea angemen along he chain. Compound 3 exhibi s 1H NMR esonances due o he -coo dina ed allyl moie y[9] a 7.07 (CH), 4.09 and 2.94 (CH2) ppm, he co esponding C a oms p oducing signals in he 13C NMR spec um a 91.2 (1JCH = 170 Hz) and 25.2 ppm (1JCH = 155 and 166 Hz) while he emaining allylic ca bon appea s a 53.0 ppm. The I -bonded alkyl ca bon, I — C(H)(CO2Me)R esona es a 12.0 ppm (1JCH = 135 Hz). This compound has been addi ionally cha ac e ized by an X- ay di ac ion s uc u e analysis (see below). 3 CH 2 Cl 2, 60 °C [I ] R RR R 2 H [I ] R RR R H (2) R=CO 2 Me The eac ion shown in Eq. (1) has been moni o ed by NMR, a low empe a u e. When 2 equi . o DMAD a e added o a solu ion o 1 in CD2Cl2 a -40 ºC, he 1 H NMR spec um eco ded immedia ely a e mixing shows quan i a i e o ma ion o a new compound, which has been cha ac e ized by NMR, a 0 ºC, as he I (I) adduc TpMe2I (C2H4)(MeO2CCCCO2Me) (4) [Eq. (3)]. I s 1H and 13C{1H} NMR spec a show local Cs symme y o he TpMe2 ligand and all he p o ons and bo h ca bon nuclei o he e hylene ligand a e equi alen , gene a ing a single in each spec um (3.14 ppm o 1H and 51.1 ppm o 13C{1H}). The 11B{1H} NMR spec um shows a single a 32.5 ppm, and his alue[11] compa es well wi h he co esponding chemical shi eco ded o complex 1 (32.9 ppm), which has been shown p e iously o be a 18-e- species wi h he TpMe2 ligand κ3 coo dina ed bo h in he solid s a e and in solu ion.[9] Compound 4 is gene a ed by subs i u ion o one o he e hylene ligands in 1 by a molecule o DMAD, a p ocess ha also occu s when his de i a i e eac s wi h one equi alen o so Lewis bases (CO and PR3; R3 = Me3, Me2Ph, E 3).[12] These eac ions ha e been p oposed o occu by an associa i e mechanism, by means o a change on he coo dina ion mode o he TpMe2 ligand, om κ3 o κ2.[12,13] CD 2 Cl 2, -40 °C 2DMAD [I ] 1 [I ] 4 R R (3) R=CO 2 Me Howe e , and unlike o he de i a i es o composi ion TpMe2I (C2H4)(L) (L = CO, PR3)[12] and ela ed Tp species,[13,14] which adop a igid igonal bipy amidal s uc u e wi h he, slowly o a ing in he NMR ime scale, e hylene ligand occupying he equa o ial posi ion, and hence gi ing ise o an AA’BB’ spin sys em in he 1H NMR spec a, compound 4 is luxional, and i s e hylene ligand seems o be as o a ing, e en a -40 ºC. This di e ence can be a ibu ed o he ac ha he e hylene ligand is occupying an axial posi ion in he igonal bipy amid (Fig. 1), whe e he π back dona ion would be weake han when in he equa o ial place.[15] The adop ion o his s uc u e is also suppo ed by a compa ison o he 13C NMR chemical shi o he e hylene ligand in he se ies o compounds TpMe2I (C2H4)(L) (L = PMe3, CO, C2H4 and DMAD) (see Table 1). Fo he case o L = C2H4, all he e hylene ca bon a oms esona e a 26.2 ppm. As al eady epo ed, his compound is luxional, and his signal ep esen s he a e age o he chemical shi s co esponding o he axial and equa o ial posi ions, and hus, he 13C{1H} NMR spec um eco ded o 1 in he solid s a e exhibi s wo signals o he e hylene ligands, a 48 and 5 ppm (axial and equa o ial, espec i ely).[9] P obably, he p e e ence o he DMAD o he equa o ial posi ion in 4 is because i is a be e -accep o han he e hylene ligand. Al hough i can no be deduced om he da a a ailable, i is p oposed ha he DMAD ligand does no o a e a ound he I —DMAD axis, due o i s s ong π-accep o cha ac e . Finally on his espec , he ela ed Tp de i a i e TpI (C2H4)(DMAD)[7c] has also been epo ed o be luxional, and he au ho s sugges a s e eochemis y analogous o he one p oposed he ein o 4. 3 I N N N NN N HB CO 2 Me CO 2 Me Figu e 1. P oposed s uc u e o complex 4. Table 1. Solu ion Chemical Shi s o he 13C Nuclei o he E hylene Ligands in Compounds o Composi ion TpMe2I (C2H4)(L). L PMe3 CO C2H4 DMAD δ C2H4 (ppm) -8.1 0.6 26.2[a] 51.1 [a] 48 and 5 ppm in he solid s a e. Compound 4 is s able up o 10 °C; abo e his empe a u e, and unde he condi ions o Eq. (3), i e ol es o a mix u e o species. Moni o ing he eac ion by 1H NMR a 20 ºC e eals he o ma ion o 2 oge he wi h o he uniden i ied species, al hough hey subsequen ly disappea , and inally 2 is p esen in ca. 90% spec oscopic yield. As we we e unable o di ec ly cha ac e ize any o he in e media e(s) species en ou e o 2, and in o de o ob ain u he in o ma ion abou his sys em, we decided o seek al e na i e ways o p epa e likely in e media es in he o ma ion o 2. In a ecen p elimina y communica ion,[8a] we ha e epo ed ha he i idacyclohep a iene 6, o be desc ibed in ull de ail elsewhe e, is ob ained by he eac ion o he I -dime hylbu adiene de i a i e 5 wi h 3 equi . o DMAD in CH2Cl2 [Eq. (4)]. In e es ingly, he p esence o a la ge excess o wa e (≥ 10 equi .) in he eac ion mix u e p e en s he inco po a ion o he hi d equi alen o alkyne, yielding he wa e s abilized[16] i idacyclopen adiene de i a i e 7 [Eq. (5)], ha ob iously has been o med by he coupling o wo DMAD molecules in he me al coo dina ion sphe e.[7] As expec ed, he wa e ligand p esen in 7 is labile, as demons a ed by he subs i u ion eac ions ca ied ou wi h NCMe and CO, ha yield he co esponding de i a i es 7·NCMe and 7·CO. Wi h excess o DMAD, an inse ion eac ion in o one o he I —C bonds akes place and compound 6 is o med (Scheme 1). All hese me allacyclopen adienes ha e been ully cha ac e ized by spec oscopy (see Expe imen al Sec ion) and in addi ion, he solid- s a e s uc u es o 7 and 7·CO ha e been de e mined by X- ay c ys allog aphy (see below). [I ] [I ] R RR R RR H 2 O CH 2 Cl 2, 60 °C 3DMAD(H 2 O) 6 5 (4) R=CO 2 Me [I ] [I ] H 2 O CH 2 Cl 2, 60 °C 3DMAD,10H 2 O 7 5 R R R R (5) R=CO 2 Me L, 60-90 ºC [I ] L 7·L(L = NCMe, CO) R R R R R=CO 2 Me [I ] H 2 O 7 R R R R [I ] R RR R RR H 2 O 6 DMAD C 6 H 12 100 ºC, 18 h Scheme 1. Syn hesis o complex 7 and i s eac i i y wi h Lewis bases and DMAD. Mo e in e es ing, in he p esen con ex , is he eac ion o 7 wi h e hylene which, a 60 ºC, esul s in he clean o ma ion o he al eady desc ibed compound 3 [Eq. (6)], suppo ing he in e mediacy o an i idacyclopen adiene species in he o ma ion o compound 2 (o 3) s a ing om 1 (o 4). Fu he mo e, i e hylene is bubbled h ough a solu ion o 7 in CDCl3, and he mix u e kep a oom empe a u e, NMR moni o ing shows he slow o ma ion o a new species 8 (Scheme 2). Compound 8 is s able a oom empe a u e and o ms me as able solu ions in chlo o o m om whe e i e en ually p ecipi a es and, a e dissolu ion in ace one-d6, could be app op ia ely cha ac e ized by NMR. The mo e cha ac e is ic signals o his compound a e hose co esponding o he wo adjacen CH2 g oups: mul iple s a 3.37, 2.90 (I CH2CH2) and 2.71, 2.17 (I CH2CH2) ppm in he 1H NMR spec um and esonances a 35.5 (I CH2CH2) and -2.6 (I CH2CH2) ppm in he 13C{1H} NMR spec um. P obably, compound 8 is o med ia displacemen o wa e by a molecule o e hylene o gi e A (Scheme 2), ollowed by he inse ion o his ligand in o one o he equi alen I —C bonds. I is wo h o men ion he acili y wi h which he e hylene inse s in o he I —C bond o he p esumed in e media e A. In he case o he ela ed, isolable, compound wi h he unsubs i u ed Tp ligand,[7c] no inse ion was obse ed up o 110 ºC. This is in ag eemen wi h he known dec eased eac i i y o he TpI compounds, as compa ed wi h he ela ed TpMe2I ones, in ac i a ion p ocesses. In he TpMe2I sys em we ha e obse ed cases in which C2H4 easily inse s in o an I —C bond, o example in i s eac ion wi h TpMe2I (C6H5)2(N2),[17] bu also ound complexes ha a e un eac i e in his espec , as he i idacyclopen ene T p Me2 I ( CH 2 C ( Me ) =C ( Me ) CH 2 ) ( C 2 H 4 ) which, upon hea ing, dissocia es he coo dina ed e hylene;[18] o he e y eac i e TpMe2I (H)(CH=CH2)(C2H4), which has been shown o yield a C4 chain by he coupling o he wo C2 ligands, al hough by ollowing a mechanis ic pa hway di e en om he inse ion o e hylene in o he I —C bond.[9] The wa e ligand in 8 is also labile and he co esponding adduc s 8·NCMe and 8·CO a e easily ob ained [Eq. (7)]. These complexes ha e been ully cha ac e ized by spec oscopy and, in addi ion, by an X- ay s udy ca ied ou wi h 8·NCMe (see below). Finally and as expec ed, hea ing solu ions o compound 8 a 40 °C p omo es i s ans o ma ion in o he allyl de i a i e 3 [Eq. (8)]. 4 [I ] H 2 O 7 R R R R CH 2 Cl 2, 60 °C C 2 H 4 3 [I ] R RR R H (6) R = CO 2 Me [I ] H 2 O 7 R R R R20 °C C 2 H 4 [I ] H 2 O R R 8 R R [I ] R R R R A H 2 O CDCl 3 R = CO 2 Me Scheme 2. Fo ma ion o he alkyl-allyl de i a i e 3 and apping o an in e media e as he wa e adduc 8. 8 L,20-60 ºC [I ] H 2 OR R R R 8·L (L =NCMe, CO) [I ] LR R R R R=CO 2 Me (7) 83 40 °C d6-ace one [I ] H2OR R R R [I ] R RR R H (8) R = CO2Me Compounds 7 o 8 we e no de ec ed du ing he cou se o he ans o ma ion depic ed in Eq. (1), and his nega i e e idence is p obably due o he absence o enough H2O in he eac ion mix u e. In ac , i he eac ion is ca ied ou in he p esence o an excess o H2O, compound 7 is o med in almos quan i a i e spec oscopic yield [Eq. (9)] and, despi e o he p esence o he e ol ed e hylene in he eac ion lask, compound 2 is no obse ed. The la ge amoun o wa e s. e hylene compe es e ec i ely o he coo dina ion o i idium, p e en ing he inco po a ion o he ole in. CH 2 Cl 2, 25 °C 2 DMAD, 10 H 2 O [I ] 1 [I ] H 2 O 7 R R R R (9) R = CO 2 Me Conside ing all he obse a ions commen ed so a , he mechanism depic ed in Scheme 3 can be p oposed o he o ma ion o compounds 2 and 3, in which compounds 7 and 8 ha e also been included. F om he expe imen al da a we canno say which o he in e media es A o B (B is depic ed as an unsa u a ed 16-e- I (III) species a he han as ha ing a 18-e- bis(ca bene) I (I) s uc u e[2c,7b]) is o med di ec ly om 4 (in bo h cases we p esume ha he second molecule o DMAD en e s he coo dina ion sphe e in an associa i e p ocess, as is he no m in subs i u ion eac ions o Tp’I (I) species). I B is o med i s , hen he e is a compe ence o coo dina ion o his in e media e, o he e ol ed e hylene ( o gi e A) and he wa e p esen in he eac ion mix u e ( o gi e 7). On he con a y, i A is he a o ed kine ic species, he coo dina ed e hylene would be dissocia i ely exchanged by H2O unde he eac ion condi ions, be o e C2H4 inse ion in o one o he I —C bonds o he me allacycle akes place. The acili y wi h which his inse ion akes place, and he obse a ion ha , unde ce ain condi ions, he i idacyclohep a iene 6 is obse ed in his eac ion (see below), and o he da a ob ained in ou labo a o y in sys ems ela ed o his one, o be discussed elsewhe e, sugges he ini ial o ma ion o in e media e B. Whiche e is he i s species o med, i is clea ha i is he esul o he oxida i e coupling o wo molecules o DMAD bonded simul aneously o i idium, and his p ocess is likely go e ned by he high endency o he Tp’I (I) de i a i es o oxidize o I (III), and mo e impo an ly by he mu ually cis disposi ion adop ed by hese ligands in he pu po ed in e media e ha also con ains a ac- ype TpMe2-I linkage. This is in ag eemen wi h he expe imen al and heo e ical s udies ca ied ou wi h he sys em [I (PR3)3(alkyne)2]+, which indica e ha he phosphines ha e o occupy a ac disposi ion o he coupling o he wo alkynes o ake place.[7b] Recen ly, i has been epo ed ha a bis(e hylene)i idium(I) de i a i e s abilized by a me ipodal ni ogen dono ligand, eac s wi h DMAD gi ing ise o a s able bis(alkyne)i idium(I) complex, e en in he p esence o NCMe.[19] [I ] 1 DMAD [I ] R R[I ] R R R R [I ] H 2 O R R R R DMAD H 2 O 1 < 10 °C 47 > 10 °C 40 °C C 2 H 4 -H elim. H-mig . C 2 H 4 ins. -C 2 H 4 [I ] R R R R -H 2 O 3 [I ] R RR R H [I ] R R R R B A (?) -C 2 H 4 DMAD > 10 °C (?) [I ] R RR R 2 H C [I ] H 2 O R R 8 R R H 2 O -H 2 O R = CO 2 Me Scheme 3. Mechanism p oposed o he o ma ion o complex 3 om he bis(e hylene) de i a i e 1 and DMAD wi h inclusion o all he in e media e species isola ed. 5 In o de o comple e his s udy, some deu e a ion expe imen s ha e been ca ied ou . Fi s , we ha e p epa ed, a low empe a u e, complex 4 by addi ion o 1 o only one equi alen o DMAD, o add a e wa ds an excess (≥ 6 equi .) o DMAD-d6. A e wa ming a 60 °C, compound 3-d6 is o med and he co esponding 1H NMR spec um exhibi s esonances o he ou CO2Me g oups o in ensi y hal o he obse ed in compound 3 [Eq. (10)]. This indica es ha 4 does no in e change wi h ee DMAD, and also e lec s he symme y o he in e media es A and B. Secondly, we ha e ound ha wo equi alen CO2Me g oups p esen in 7 can be selec i ely eplaced by CO2CD3 by a anses e i ica ion p ocess in CD3OD, ca alyzed by acid. Al hough no con i med, i is highly p obable, on s e ic g ounds, ha he deu e a ed posi ions a e hose shown in Scheme 4. When 7-d6 is subjec ed o eac ion wi h C2H4, no sc ambling o he labels is obse ed, as wo CO2Me esonances a e absen in he 1H NMR spec a o compound 3-d6, p obably hose shown in Scheme 4. This expe imen ules ou any in e con e sion be ween he i idacyclopen adiene and a bis(alkyne)I (I) species [Eq. (11)] and his is in acco d wi h he indings obse ed in a ela ed sys em.[7a] 3-d 6 CD 2 Cl 2, 60 °C >6 DMAD-d 6 [I ] 4 R R [I ] R-d 1.5 R-d 1.5 R-d 1.5 R-d 1.5 H (10) R = CO 2 Me [I ] H2O 7 R R R R [I ] H2O 7-d6 R R-d3 R-d3 R CD3OD H+ 3-d6 [I ] R R-d3 R-d3 R H C2H4 60 ºC R = CO2Me Scheme 4. Pa ial deu e a ion o complex 7 by a anses e i ica ion eac ion in CD3OD. [I ] H 2 O 7 R R R R (11) [I ] R R R R D R = CO 2 Me Men ion has o be done o he di e en eac i i y obse ed when he eac ion o compound 1 is ca ied ou , in solu ion a 60 ºC, wi h 3 equi . o DMAD, and whe e, unde he app op ia e condi ions, he i idacyclohep a iene 6 is gene a ed. This esul is almos independen on he sol en employed (C6H12, CH2Cl2 o CHCl3), bu s ongly depends on he condi ions o he eac ion. Thus, i i is ca ied ou in deu e a ed chlo o o m o dichlo ome hane (in cyclohexane he s a ing ma e ial is no soluble enough), in a NMR ube, compound 3 is o med in almos quan i a i e spec oscopic yield (>90%). By con as , i he eac ion is pe o med, s a ing wi h he same amoun o compound and sol en in a much bigge sealed lask (hence wi h much bigge a mosphe e olume), bo h 3 and 6 a e o med, in ca. 1:1 a io. This seems o indica e ha he i idacyclopen adiene in e media e B o Scheme 3 is less eac i e owa ds DMAD han owa ds e hylene (as men ioned be o e, he H2O adduc 7 eac s wi h C2H4 a 25 ºC, while i s eac ion wi h DMAD equi es much highe empe a u es), and his may be due o he lesse endency o he I (III) in e media e (al eady elec on de icien ) o bind he alkyne, less elec on-dona ing han e hylene. A his poin i seems app op ia e o make ano he compa ison wi h he ela ed sys em o he unsubs i u ed Tp ligand, TpI (C2H4)2- DMAD (Scheme 5).[7c] In his case, he i s s ep is also he o ma ion o he I (I) adduc Tp(C2H4)(DMAD), a compound ha is s able a oom empe a u e, and ha when hea ed in ace oni ile o o he sol en s like THF o ms an i idacyclopen -2-ene, by oxida i e coupling o e hylene and DMAD. This coupling is no obse ed in he case o he co esponding TpMe2 de i a i e 4, which, as al eady men ioned, decomposes a >10 ºC in he p esence o 1 equi . o C2H4 and 1 equi . o DMAD o gi e 2 (in he absence o DMAD 4 e ol es by a inylic C—H ac i a ion p ocess o be epo ed elsewhe e). I DMAD is p esen , he Tp-i idacyclopen ene s uc u e can be ans o med, unde app op ia e condi ions, in o an i idacyclopen adiene analogous o ou p oposed in e media e A. As al eady men ioned, his compound is e y s able and highly eluc an o expe ience e hylene inse ion in o he I —C bonds o he me allacycle, no ans o ma ion aking place e en a 100 ºC, his ac highligh ing once mo e he highe eac i i y o he TpMe2 de i a i es in compa ison wi h he Tp ones. I R R R R I O R R TpI R R THF 60 ºC Tp Tp DMAD C 6 H 6 , 60 ºC oluene-d 8 100 ºC, 13 h no eac ion R = CO 2 Me Scheme 5. Fo ma ion o an i idacyclopen -2-ene and an i idacyclopen adiene in he sys em TpI -C2H4-DMAD. We ha e also s udied he eac ion o compound TpMe2I (C2H4)(DMAD) (4) wi h me hyl p opiola e (MP), a e minal alkyne. In p inciple, a eac i i y simila o ha obse ed o DMAD could be ad anced, al hough he asymme y o MP may gi e ise o wo di e en coupled egioisome s. Also, he p esence o he e minal C—H bond in MP could p omo e C—H ac i a ion eac ions.[20,21] The sequen ial addi ion o 1, a low empe a u e, o 1 equi . o DMAD and 1 equi . o MP in he p esence o added wa e (10 equi .), p oduces selec i ely, upon wa ming o oom empe a u e, he i idacyclopen adiene 9 [Eq. (12)] in which he CH o he MP occupies a  posi ion in he ing, as deduced by i s 1H NMR chemical shi o 7.75 ppm (in his kind o I -complexes an alkenyl CH in  posi ion would gi e a signal u he down ield, e en a 10 ppm).[20] As expec ed, he wa e ligand in 9 is labile, and he compounds 9·NCMe and 9·CO a e eadily syn hesized by i s 6 eac ion wi h an excess o L [Eq. (13)]. The new i idacyclopen adienes ha e been ully cha ac e ized by mic oanalysis and spec oscopy (IR, 1H and 13C NMR s udies) and in addi ion, he solid-s a e s uc u e o 9 and 9·NCMe ha e been de e mined by X- ay c ys allog aphy (see below). [I ] H2O 9 R H R R 1 DMAD [I ] 1 [I ] 4 R R THF -20 °C 1 MP, >10 H2O THF25 °C (12) -20 ºC R = CO2Me [I ] H 2 O 9 R H R R [I ] L 9·L (L=NCMe, CO) R H R R L, 25 ºC R=CO 2 Me (13) Complex 9 eac s wi h e hylene, a oom empe a u e, wi h he egio- and s e eoselec i e o ma ion o he hyd ido-ole in de i a i e 10 (Scheme 6). In his case, he o ma ion o his kind o species seems o be e y a o able, since he pu po ed in e media e i idacyclohexadiene ela ed o 8 has no been obse ed, e en in he p esence o excess o added wa e . Sequen ial addi ion o DMAD and MP o compound 1, in he absence o wa e , a low empe a u e, ollowed by s i ing a 25 ºC o 15 min, also yields complex 10, in almos quan i a i e yield. Unlike 2, 10 is e y s able, can be p ope ly pu i ied, and i has been comple ely cha ac e ized, including an X- ay s uc u e de e mina ion (see below), which i mly es ablishes ha he inse ion o he e hylene has aken place egioselec i ely in o he I —C bond o 9 adjacen o he C—H unc ionali y. In acco d wi h he high s abili y o his de i a i e, isome iza ion o he co esponding allyl de i a i e 11 equi es qui e o cing condi ions [Eq (15)]. The NMR da a ob ained o his compound a e in ag eemen wi h he s uc u e depic ed, bu he compound expe iences some kind o luxional p ocess, p obably con o ma ional in o igin, which is esponsible o he b oadening o some o he esonances, in bo h 1H and 13C{1H} NMR spec a (see Expe imen al Sec ion). 11 [I ] R RH R H [I ] H 2 O 9 R H R R [I ] R RH R 10 H C 2 H 4 CH 2 Cl 2 25 °C CH 2 Cl 2 80 °C 24 h R = CO 2 Me Scheme 6. Consecu i e o ma ion o complexes 10 and 11 om he i idacyclopen adiene 9 and C2H4. X-Ray di ac ion s udies Table 2 p esen s c ys al da a and da a collec ion de ails o all compounds analyzed in his sec ion. Complex 3: Figu e 2 shows an ORTEP iew o a molecule o 3 while Table 3 gi es selec ed bond leng hs and angles. The sp3 ca bon a om bonded o i idium o ms an i idium-ca bon bond wi h a leng h o 2.12 Å, a alue ypical o an I —C single bond.[22] The η3- allyl—I in e ac ion is cha ac e ized by I —C bond dis ances o I — C(1), 2.16; I —C(2), 2.10 and I —C(3), 2.18 Å and he C(1)— C(2)—C(3) angle o 121.4º is clea ly in acco d wi h almos pu e sp2 hyb idiza ion a he C(2) ca bon. INSERT TABLE 2 HERE Figu e 2. X- ay s uc u e o complex 3 ( he mal ellipsoids d awn a he 50% p obabili y le el). Table 3. Selec ed bond leng hs [Å] and angles [º] o complex 3 I —N(6) 2.214(2) I —C(2) 2.098(2) I —C(3) 2.181(2) C(5)—C(6) 1.507(3) I —C(1) 2.164(2) C(3)—C(4) 1.482(3) I —N(2) 2.139(2) C(2)—C(3) 1.442(3) I —C(6) 2.118(2) C(1)—C(2) 1.411(3) I —N(4) 2.106(2) C(4)—C(5) 1.366(3) N(2)—I —N(6) 87.61(7) C(1)—C(2)—C(3) 121.4(2) N(4)—I —N(2) 90.68(7) C(2)—C(3)—C(4) 116.4(2) N(4)—I —N(6) 80.62(7) C(5)—C(4)—C(3) 118.5(2) C(6)—I —C(1) 87.48(9) C(4)—C(5)—C(6) 117.4(2) C(6)—I —C(3) 79.86(8) C(5)—C(6)—I 110.06(15) C(1)—I —C(3) 69.86(9) C(2)—C(3)—I 67.21(12) 7 Complexes 7 and 7·CO: In Figu es 3 and 4, he molecula s uc u es o complexes 7 and 7·CO a e ep esen ed, while Table 4 collec s selec ed bond leng hs and angles. The i s compound c ys allized wi h ca. 1.25 molecules o addi ional wa e which o m hyd ogen bonds wi h he I —OH2 moie y. The i idacyclopen adiene uni s in 7 and 7·CO a e almos plana , cha ac e ized by C—I —C bi e angles o 79.3 and 78.6º, espec i ely, and all he I —C bond dis ances all be ween 2.00 and 2.06 Å as expec ed o sp2 ca bons.[22] In e es ingly, o complex 7 he I —N(py azolyl) bond ans wi h espec o he ha d wa e ligand is sho e (2.03 Å) han he o he wo (2.16 Å a .) bu his e ec is a he diminished in 7·CO. Figu e 3. X-Ray s uc u e o complex 7 ( he mal ellipsoids d awn a he 50% p obabili y le el). Figu e 4. X-Ray s uc u e o complex 7·CO ( he mal ellipsoids d awn a he 20% p obabili y le el. Table 4. Selec ed Bond Leng hs (Å) and Angles (deg) o Complexes 7 and 7·CO. 7 7·CO I —N(12) 2.171(5) 2.151(3) I —N(22) 2.157(5) 2.128(3) I —N(32) 2.035(4) 2.111(3) I —C(42) 2.001(6) 2.055(4) I —C(52) 2.037(6) 2.067(4) I —L 2.091(3) 1.852(4) C(42)—C(43) 1.368(8) 1.358(6) C(43)—C(53) 1.463(9) 1.463(5) C(52)—C(53) 1.375(8) 1.355(6) C(42)—I —C(52) 79.3(2) 78.64(16) C(42)—I —L 90.19(19) 85.45(17) C(52)—I —L 87.72(18) 84.99(17) Complex 8·NCMe: Figu e 5 shows an ORTEP iew o his compound and Table 5 collec s selec ed bond leng hs and angles. The I —C(alkenyl) dis ance (2.02 Å) compa es well wi h hose commen ed o he i idacyclopen adienes 7 and 7·CO while he co esponding I —CH2 is longe a 2.09 Å. In u n, his la e bond is sligh ly sho e han he I —C(alkyl) p esen in complex 3 which suppo s a CO2Me subs i uen . O he h ee I —N(py azolyl) bonds, he one ans wi h espec o he NCMe is sho e (2.05 Å) han he o he wo (2.16 Å a .), and in ha way he ace oni ile beha es like he H2O ligand, ano he ha d dono , in 7. 8 Figu e 5. X-Ray s uc u e o complex 8·NCMe ( he mal ellipsoids d awn a he 20% p obabili y le el. Table 5. Selec ed bond leng hs [Å] and angles [º] o complex 8·NCMe I —N(12) 2.164(4) C(41)—C(42) 1.545(6) I —N(22) 2.157(4) C(42)—C(52) 1.496(6) I —N(32) 2.049(3) C(53)—C(62) 1.477(6) I —C(41) 2.091(4) C(52)—C(53) 1.368(6) I —C(63) 2.025(4) C(62)—C(63) 1.354(6) I —N(71) 1.976(3) N(71)—C(72) 1.133(5) N(22)—I —N(12) 84.47(13) C(62)—C(63)—I 127.6(3) N(32)—I —N(12) 88.30(13) C(42)—C(41)—I 117.3(3) N(32)—I —N(22) 89.85(16) C(52)—C(42)—C(41) 110.6(4) C(63)—I —C(41) 94.02(17) C(53)—C(52)—C(42) 121.8(4) N(71)—I —C(41) 92.68(18) C(52)—C(53)—C(62) 122.4(4) N(71)—I —C(63) 90.91(16) C(63)—C(62)—C(53) 124.4(4) Complex 9: The s uc u e o his complex is shown in Figu e 6, while selec ed bond leng hs and angles a e collec ed in Table 6. Once again he i idacyclopen adiene ing is almos plana and he I —N(py azolyl) bond ans o he H2O is sho e (2.04 Å) han he o he wo (2.15 Å a .). As commen ed in sec ion Resul s, he I — C(alkenyl) bond ha suppo s he CH unc ionali y is mo e eac i e agains C2H4 inse ion han he o he simila one p esen in his molecule. F om he co esponding bond dis ances, 2.04 s. 2.02 Å, i may be concluded ha he i s bond is sligh ly weake han he second and his may be he eason o he di e en eac i i y. Howe e , we ha e ound ha me hyl p opiola e inse s in o he ing o 9 wi h he opposi e egioselec i i y.[23] Figu e 6. X-Ray s uc u e o complex 9 ( he mal ellipsoids d awn a he 40% p obabili y le el). Table 6. Selec ed Bond Leng hs (Å) and Angles (deg) o complex 9. I —N(1) 2.142(3) I —O(1) 2.103(2) I —N(3) 2.041(3) C(16)—C(17) 1.363(5) I —N(5) 2.155(3) C(17)—C(18) 1.464(4) I —C(16) 2.021(3) C(18)—C(19) 1.357(4) I —C(19) 2.039(3) C(16)-I (1)-C(19) 79.45(12) C(16)-I (1)-N(1) 177.72(11) C(16)-I (1)-N(3) 93.49(11) C(19)-I (1)-N(1) 99.04(11) C(19)-I (1)-N(3) 96.87(11) O(1)-I (1)-N(1) 89.46(10) C(16)-I (1)-O(1) 88.74(11) C(16)-I (1)-N(5) 97.52(12) C(19)-I (1)-O(1) 86.28(11) C(19)-I (1)-N(5) 172.68(11) N(3)-I (1)-O(1) 176.43(10) O(1)-I (1)-N(5) 86.99(10) 9 Complex 9·NCMe: An ORTEP iew o his molecule is shown in Figu e 7 and selec ed bond leng h and angles a e collec ed in Table 7. These a e e y simila o hose ound in 9 and will no be commen ed wi h he excep ion o he wo I —C(alkenyl) bond dis ances. In e es ingly, and in compa ison wi h 9, o he ca bon ha suppo s he CH g oup he I —C dis ance is much longe (2.03 Å) han he o he one (1.97 Å). Figu e 7. X-Ray s uc u e o complex 9·NCMe ( he mal ellipsoids d awn a he 30% p obabili y le el). Table 7. Selec ed bond leng hs [Å] and angles [º] o complex 9·NCMe I —N(22) 2.158(5) I —N(61) 1.991(5) I —N(12) 2.157(5) C(41)—C(53) 1.410(9) I —N(32) 2.044(4) C(52)—C(53) 1.364(8) I —C(42) 2.033(5) C(41)—C(42) 1.351(8) I —C(52) 1.974(7) N(61)—C(62) 1.144(7) N(12)-I -N(22) 82.98(17) C(52)-I -C(42) 77.1(2) N(32)-I -N(12) 89.91(17) C(53)-C(52)-I 118.6(5) N(32)-I -N(22) 88.38(18) C(41)-C(42)-I 114.6(4) N(61)-I -C(42) 87.8(2) C(42)-C(41)-C(53) 115.8(6) C(52)-I -N(61) 87.3(2) C(52)-C(53)-C(41) 111.5(6) Complex 10: The molecula s uc u e o his compound is shown in Figu e 8, while selec ed bond leng h and angles a e collec ed in Table 8. The I —C(41) bond dis ance a 2.02 Å is in he expec ed ange o an I —C(alkenyl) species while, o he ole in bonded o I , he C(45)—C(46) sepa a ion o 1.49 Å is much close o he co esponding o a single C—C bond (1.54 Å) han o a double one (1.34 Å), and his p obably e lec s a qui e s ong I - ole in bond. Figu e 8. X-Ray s uc u e o complex 10 ( he mal ellipsoids d awn a he 40% p obabili y le el). Table 8. Selec ed Bond Leng hs (Å) and Angles (deg) o complex 10 I —N(12) 2.193(2) I —H(1I) 1.600 I —C(45) 2.180(3) C(44)—C(45) 1.495(4) I —N(22) 2.162(2) C(42)—C(43) 1.460(4) I —C(46) 2.138(3) C(45)—C(46) 1.391(5) I —N(32) 2.090(2) C(41)—C(42) 1.363(4) I —C(41) 2.015(3) C(43)—C(44) 1.343(4) N(22)-I -N(12) 87.79(9) C(46)-I (1)-C(45) 37.56(13) N(32)-I -N(12) 88.19(9) C(42)-C(41)-I 129.1(2) N(32)-I -N(22) 82.82(9) C(44)-(45)-I 116.8(2) C(41)-I -H(1I) 94.7(14) C(41)-C(42)-C(43) 123.4(3) C(41)-I -C(46) 92.93(13) C(44)-C(43)-C(42) 127.1(3) C(41)-I -C(45) 90.64(12) C(43)-C(44)-C(45) 126.0(3) C(45)-I -H(1H) 69.5(10) C(46)-C(45)-C(44) 123.0(3)