High resolution multi-nuclear 1 and 2D NMR characterization of stannous halide complexes of Rh(I/III) in aqueous and non-aqueous solutions

Barkhuysen, Shani (2016-03)

Thesis (PhD)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: A detailed high-resolution multi-nuclear NMR study the stannous halide complexes of Rh(I/III) in aqueous and non-aqueous solutions has been undertaken. In this study the series of [RhIII(SnX3)nX6-n]3- (X = Cl-/Br-, n = 1 – 6) anions, the [RhI(SnX3)5]4- (X = Cl-/Br-) and the[RhIIIH(SnX3)5]3- (X = Cl-/Br-) complex anion have been synthesized and characterized bymeans of high-resolution 119Sn NMR spectroscopy in both aqueous and non-aqueous phases.It is shown in this work that, in contrast to the tacitly accepted kinetically labile nature of these Rh(III)-Sn(II) species, these do not undergo rapid inter- and intra-molecular exchange of the SnX3- ligands rapidly on the NMR time scale and are indeed kinetically inert. In aqueous HCl, the 119Sn NMR spectra display up to 9 (of an expected 10) main sets of 119Snresonances split into doublets due to 1J(103Rh-119Sn) (103Rh: I = ½, 100 %) in addition to2J(117/119Sn-119Sn) coupling satellites. A detailed investigation of the resonances at (119Sn) =-278.2 and -202.5 ppm reveals that the 2J(119Sn-119Sn) satellites are not symmetricallydistributed around the respective main signals. The set of resonances at -278.2 ppm was previously assigned to a kinetically labile cis-[RhIII(SnCl3)4Cl2]3- complex anion, whereas thesignal at -202.5 ppm was unassigned. We now find that the 119Sn NMR signals at -278.2 ppmand -202.5 ppm can be assigned to the equatorial and axial isotopomers of cis-RhIII(SnCl3)4Cl2]3-, respectively. This implies that the cis-RhIII(SnCl3)4Cl2]3- complex anion iskinetically inert and results in two resonances due to the observed 119SnCl3- ligand in theaxial (trans toSnCl3-) position not being magnetically equivalent to the 119SnCl3- ligand in theequatorial (trans to Cl-) position. This is supported by a detailed analysis of the 2J(119Sn-119Sn)cis,ax-eq coupling in the various possible isotopomers of this complex, as well as the good agreement between the simulated spectra generated by a computer program gNMR50 and the spectra experimentally recorded. Moreover, the experimental ratio of (νA – νB)/JAB  8.2 suggests second order 2J(119Sn-119Sn) coupling effects accounts for the asymmetrical 2J(119Sn-119Sn)cis,ax-eq satellites. Similarly the 119Sn NMR spectra of other [RhIII(SnCl3)nCl6-n]3- (n = 1 -5)species are consistent with kinetically inert complexes, including the [RhIII(SnCl3)6]3-species detected for the 1st time in solution. The 119Sn NMR signals of all the species in theseries of [RhIII(SnCl3)nCl6-n]3- (n = 1 - 6) complex anions, as well as [RhI(SnCl3)5]4- and the[RhIIIH(SnCl3)5]3- have been correctly assigned. The analogous series of [RhIII(SnBr3)nBr6-n]3- (n = 3 – 5) were prepared and characterized for thefirst time. Investigation of the stannous bromide complexes of rhodium(I/III) in HBr solutions furnished the assignment of 3 new [RhIII(SnBr3)nBr6-n]3- (n = 3 – 5) species. Moreover, thedistinctive isotopomer pairs of these complex anions were assigned. It is thus established that these species, as with the analogous chlorido species, are kinetically inert and do not undergo rapid intra- or inter-molecular exchange on the NMR time-scale. Comparison between the 119Sn NMR parameters of the stannous chlorido and stannous bromido species shows that the 1J(103Rh-119Sn) coupling constant is smaller for the [RhIII(SnBr3)nBr6-n]3- (n = 3 – 5) speciesthan the [RhIII(SnCl3)nCl6-n]3- species which suggests that the 103Rh-SnBr3- bond length islonger than the 103Rh-SnCl3- bond length. 119Sn NMR spectroscopy showed that the kinetically inert [RhIII(SnCl3)nCl6-n]3- (n = 1 - 6) and [RhIIIH(SnCl3)5]3- complex anions, together with the [RhI(SnCl3)5]4-, are extracted into non-aqueous solutions using methyl isobutyl ketone (MIBK) and methyltrioctylammonium chloride (AQ336) in chloroform. With a Rh:Sn mole ratio of more than 1:10, the [RhIIIH(SnCl3)5]3- complex anion predominates the non-aqueous solutions, howeveradditional signals are always observed. A detailed 1H and 119Sn NMR study of the isotopologues and isotopomers of the [RhIIIH(SnCl3)5]3- species extracted into MIBK wasundertaken. From the 119Sn NMR spectrum, and with the aid of gNMR50 to simulate thespectra, two isotopomers (axial 119SnCl3- and equatorial 119SnCl3-) and six isotopologues wereassigned and characterized. Twelve respective isotopologues and isotopomers were assigned in the 1H NMR spectrum of the [RhIIIH(SnCl3)5]3- complex anion. However, this was onlyachieved with the aid of a simulated 1H NMR spectrum with gNMR50, wherein the 1H NMRparameters were used to record a indirectly detected 103Rh,1H HMQC NMR spectrum for thisspecies and the δ(103Rh) was determined to be -1191 ppm. This is the first 103Rh chemicalshift value reported for these Rh(III)-Sn(II) species. Decreasing the stannous(II)chloride concentration, and thus the Rh:Sn mole ratio, in the aqueous phase results in the disappearance of the [RhIIIH(SnCl3)5]3- complex anion, accompanied by the formation ofmore 119Sn NMR signals upfield of the hydrido species. These species correspond well to thekinetically inert species in the aqueous phase and is assigned accordingly. A detailed isotopologue/isotopomer study of all the species observed in the non-aqueous phases resulted in the assignment of 7 possible species: [RhIII(SnCl3)nCl6-n]3- (n = 2 – 6), including the[RhIII(SnCl3)6]3- species not previously observed, [RhIIIH(SnCl3)5]3- and [RhI(SnCl3)5]4-. Moreover, 5 isotopomer pairs, as well as the respective isotopologues, for these species were identified and assigned for the first time.

AFRIKAANSE OPSOMMING: „n In-diepte hoë-resolusie, multi-kern KMR studie van die tin(II)halied komplekse van Rh(I/III) in beide waterige en nie-waterige oplossings is onderneem. Tydens hierdie studie is die reeks [Rh(SnX3)nX6-n]3- (X = Cl-/Br-, n = 1 – 6) kompleksanione, die [Rh(SnX3)5]4- (X = Cl-/Br-) kompleksanioon en die [RhH(SnX3)5]3- (X = Cl-/Br-) kompleks anioon met hoë-resolusie 119Sn KMR in beide waterige en nie-waterige oplossings geïdentifiseer en gekarakteriseer. Daarenbowe is bewys dat, in teenstelling met die stilswyend aanvaarde stereo-chemies nie-rigiede aard van die Rh(III)-Sn(I) spesies, hierdie spesies nie vinnige inter- en intra-molekulêre uitruiling van die SnX3- (X = Cl- or Br-) ligande op die KMR tydskaal ondergaan nie en dus dat hieride spesies wel stereo-chemies rigied is. In waterige soutsuur oplossings word tot nege (van die verwagte tien) hoof stelle 119Sn seine, elkeen verdeel in dublette weens 1J(103Rh-119Sn) (103Rh: I = ½, 100 %) en omring met 2J(117/119Sn-119Sn) satelliete, in die 119Sn KMR spektra vertoon. „n Meer in diepte ondersoek van die 119Sn seine by -278.2 en -202.5 ppm het onthul dat die 2J(119Sn-119Sn) satelliete nie simmetries rondom die hoof seine versprei is nie. Die 119Sn KMR sein by -278.2 ppm was voorheen toegeskryf aan „n stereo-chemies rigiede cis-[RhIII(SnCl3)4Cl2]3- kompleksanioon, terwyl die sein by -202.5 ppm nie geïdentifiseerd was nie. Tydens hierdie studie is egter gewys dat die 119Sn KMR seine by -278.2 ppm en -202.5 ppm aan die ekwatoriale en aksiale isotopomere van die cis-[RhIII(SnCl3)4Cl2]3- kompleksanioon onderskeidelik toegeskryf kan word. Dit impliseer dus dat die cis-[RhIII(SnCl3)4Cl2]3- kompleksanioon stereo-chemies rigied is en gevolglik dat twee afsonderlike seine verkry word vir die isotopomere waarin die waargenome SnCl3- ligande in die aksiale (cis aan Cl-) en ekwatoriale (trans aan Cl-) posisies is, aangesien hierdie twee 119Sn atome nie magneties ekwivalent is nie. Hierdie toeskrywing word ondersteun deur „n gedetailleerde analise van die 2J(119Sn-119Sn)cis,ax-eq koppeling in die verskillende moontlike isotopomere van hierdie kompleks, sowel as simulasies van die verwagte spektra met behulp van „n rekenaar program, gNMR50, wat goed ooreenstem met die eksperimenteel verkreide spektra. Verder dui die eksperimenteel verkreide verhouding van (νA - νB) / JAB  8,2 daarop dat die asimmetriese 2J(119Sn-119Sn)cis,eq-ax satelliete toegeskryf kan word aan tweede orde 2J(119Sn-119Sn) koppelingseffekte. Net so is die 119Sn KMR spektra van ander [RhIII(SnCl3)nCl6-n]3- (n = 1 - 5) spesies ook in ooreenstemming met stereo-chemies rigiede komplekse, insluitende die van die [RhIII(SnCl3)6]3- spesies, wat vir die eerste keer in oplossings geïdentifiseer en gekarakteriseer is. Die 119Sn KMR seine van die reeks [RhIII(SnCl3)nCl6-n] 3- (n = 1-6) anione, sowel as [RHI(SnCl3)5]4- en die [RhIIIH(SnCl3)5]3- is korrek toegedien. Tydens hierdie studie is die reeks [RhIII(SnBr3)nBr6-n]3- (n = 3 - 5) spesies is vir die eerste keer voorberei en gekarakteriseer deur middel van hoë-resolusie 119Sn KMR. Ondersoek van die tin(II)bromied komplekse van rodium(I/III) in HBr oplossings het gelei to die toedeling van 3 nuwe [RhIII(SnBr3)nBr6-n]3- (n = 3 - 5) spesies. Daarenbowe is die isotopomeerpare (119SnBr3- trans tot SnBr3- of trans tot Br-) van elk van hierdie kompleksanione geïdentifeseer en gekarakteriseer. Dit is dus vasgestel dat hierdie spesies, soos gevind met die ooreenstemmende chloried spesies, stereo-chemies rigied is en nie vinnige intra- of inter-molekulêre uitruiling op die KMR tydskaal ondergaan nie. Vergelyking tussen die 119Sn KMR parameters van die tin(II)chloride en tin(II)bromide Rh(III) spesies toon dat die 1J(103Rh-119Sn) koppelings-konstante kleiner is vir die [RhIII(SnBr3)nBr6-n]3- (n = 3 - 5) spesies as vir die [RhIII(SnCl3)nCl6-n]3- spesies wat daarop dui dat die 103Rh-SnBr3- bindingslengte langer is as die 103Rh-SnCl3- bindingslengte. 119Sn KMR spektroskopie het getoon dat die stereo-chemies rigiede [RhIII(SnCl3)nCl6-n]3- (n = 1 - 6) en [RhIIIH(SnCl3)5]3- komplekse anione, asook die [RhI(SnCl3)5]4- spesies, in metiel iso-butiel ketoon (mibk) en metiel tri-oktiel ammonium chloried (Aliquat-336 of AQ336) in chloroform in geekstraeer word. Alhoewel die [RhIIIH(SnCl3)5]3- kompleksanioon die oorheersende spesies in die nie-waterige oplossings is wanneer 'n Rh:Sn molverhouding van meer as 1:10 gebruik is, word daar altyd steeds addisionele seine waargeneem. 'n Gedetailleerde 1H en 119Sn KMR studie van die isotopoloë en isotopomere van die [RhIIIH(SnCl3)5]3- spesies in MIBK is onderneem. Vanaf die verkrygde 119Sn KMR spektrum, en met die hulp van gNMR50 om die spektra te simuleer, is twee isotopomere (aksiale (trans tot Cl-) 119SnCl3- en ekwatoriale (trans tot SnCl3-) 119SnCl3-) en ses isotopoloë geïdentifiseer en gekarakteriseer. Daarteenoor is twaalf onderskeie isotopoloë en isotopomere in die 1H KMR spektrum van die [RhIIIH(SnCl3)5]3- kompleksanion geïdentifiseer. Die karakterisering van hierdie isotopoloe en isotopomere was egter slegs moontlik met die hulp van 'n gNMR50 gesimuleerde 1H KMR spectrum. Die 1H KMR parameters is gebruik vir „n indirekte metode om 103Rh te analiseer: 103Rh, 1H “HMBK” KMR. Die 103Rh, 1H KMR spektrum vir hierdie spesies het een sein getoon met δ(103Rh) = -1191 dpm. Dit is die eerste 103Rh chemiese verskuiwing waarde wat vir hierdie Rh(III)-Sn(II) spesies berig is. Die vermindering van die Rh:Sn molverhouding in die waterige fase het tot gevolg gehad dat die [RhIIIH(SnCl3)5]3- kompleksanioon minder word, terwyl meer 119Sn KMR seine veld-op van die hydrido spesies gevorm word. Hierdie spesies stem goed ooreen met die stereo-chemies rigiede spesies in die waterige fase en is dienooreenkomstig toegedien. 'n Gedetailleerde isotopoloog/isotopomeer studie van al die waargeneem in die nie-waterige fases spesies gelei het tot die toedeling van 7 moontlike spesies: [RhIII(SnCl3)nCl6-n]3- (n = 2 - 6), insluitend die [RhIII(SnCl3)6]3- spesies nie voorheen waargeneem is nie, [RhIIIH(SnCl3)5]3- en [RhI(SnCl3)5]4-. Verder is daar 5 isotopomeerpare, asook die onderskeie isotopoloë vir hierdie spesies geïdentifiseer vir die eerste keer.

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