Supporting Information

Structural studies of cesium, lithium/cesium and

sodium/cesium bis(trimethylsilyl)amide (HMDS)

complexes

Ana I. Ojeda-Amador, Antonio J. Martínez-Martínez, Alan R. Kennedy and Charles T.

O'Hara

WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, United Kingdom

Table S1. 1H and 13C δ for LiHMDS, NaHMDS, CsHMDS, (R,R)-TMCDA, TMEDA, PMDETA. Me6TREN and TMEEA in C6D6 at 300 K.

1H C6D613C C6D6

LiHMDS 0.13 (SiCH3) 5.0 (SiCH3)

NaHMDS 0.12 (SiCH3) 6.9 (SiCH3)

CsHMDS 0.21 (SiCH3) (SiCH3)

(R,R)-TMCDA

2.29 (CH3) 40.6 (CH3)2.26 (α-CH) 64.3 (α-CH)

1.75 (β-CH2), 1.60 (γ-CH2) 26.0 (β-CH2)1.01 (β-CH2), 1.01 (γ-CH2) 25.7 (γ-CH2)

TMEDA 

2.12 (CH3) 46.0 (CH3)2.36 (CH2) 58.4 (CH2)

PMDETA2.1187 46.07412.1844 43.2028

2.4839, 2.3620 58.4156, 56.9915

Me6-TREN2.12 46

2.63 (α-CH2), 2.37 (β-CH2) 58.6 (α-CH2), 53.9 (β-CH2)

TMEEA

3.46, 3.44 (CH2)  3.35 (CH2)   3.14 (CH3)   2.76 (CH2)  

Figure S1. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 1.

Figure S2. 13C{1H} NMR spectrum (100.6 MHz, C6D6, 300 K) of isolated crystals of 1.

Figure S3. 7Li NMR (C6D6, 155.5 MHz, 300 K) of isolated crystals of 1.

Figure S4. 133Cs NMR (52.5 MHz, C6D6, 300 K) of isolated crystals of 1.

Figure S5. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 2.

Figure S6. 13C{1H} NMR spectrum (100.6 MHz, C6D6, 300 K) of isolated crystals of 2.

Figure S7. 7Li NMR (52.5 MHz, C6D6, 300 K) of isolated crystals of 2.

Figure S8. 133Cs NMR (52.5 MHz, C6D6, 300 K) of isolated crystals of 2.

Figure S9. 1H NMR variable temperature study of 2 in d8-toluene.

Figure S10. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 3.

Figure S11. 13C{1H} NMR spectrum (100.6 MHz C6D6, 300 K) of isolated crystals of 3.

Figure S12. 133Cs NMR (52.5 MHz, C6D6, 300 K) of isolated crystals of 3.

Figure S13. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 4.

Figure S14. 13C{1H} NMR spectrum (100.6 MHz, C6D6, 300 K) of isolated crystals of 4.

Figure S15. 133Cs NMR (52.5 MHz, C6D6, 300 K) of isolated crystals of 4.

Figure S16. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 5.

Figure S17. 13C{1H} NMR spectrum (100.6 MHz, C6D6, 300 K) of isolated crystals of 5.

Figure S18. 133Cs NMR (52.5 MHz, C6D6, 300 K) of isolated crystals of 5.

Figure S19. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 6.

Figure S20. 13C{1H} NMR spectrum (100.6 MHz, C6D6, 300 K) of isolated crystals of 6.

Figure S21. 133Cs NMR (52.5 MHz, C6D6, 300 K) of isolated crystals of 6.

Figure S22. Variable temperature 1H NMR study of a solution of 6 in d8-toluene from 300 K to 203 K, showing coordination of TMEDA to CsHMDS at 203 K.

Figure S23. 133Cs NMR (52.5 MHz, d8-tol, 300 K) of isolated crystals of 6.

Figure S24. 133Cs NMR (52.5 MHz, d8-tol, 258 K) of isolated crystals of 6.

Figure S25. 133Cs NMR (52.5 MHz, d8-tol, 203 K) of isolated crystals of 6.

300 K

243 K

203 K

Figure S26. Variable temperature 1H NMR study of a d8-toluene solution of TMEDA at 300 K, 243 K and 203 K.

Figure S27. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 7.

Figure S28. 13C{1H} NMR spectrum (100.6 MHz, C6D6, 300 K) of isolated crystals of 7.

Figure S29. 133Cs NMR (52.5, C6D6, 300 K) of isolated crystals of 7.

Figure S30. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 8.

Figure S31. 13C{1H} NMR spectrum (100.6 MHz, C6D6, 300 K) of isolated crystals of 8.

Figure S32. 133Cs NMR (52.5, C6D6, 300 K) of isolated crystals of 8.

Figure S33. 1H NMR (400.1 MHz, C6D6, 300 K) of isolated crystals of 9.

Figure S34. 13C{1H} NMR spectrum (100.6 MHz, C6D6, 300 K) of isolated crystals of 9.

Figure S35. HSQC (400.1 MHz, C6D6, 300 K) of isolated crystals of 9.

Figure S36. HSQC (400.1 MHz, C6D6, 300 K) of isolated crystals of 9.

Figure S37. 133Cs NMR (52.5, C6D6, 300 K) of isolated crystals of 9.

1H DOSY NMR studies1H DOSY (Diffusion-Ordered Spetroscopy) NMR experiments were performed on a Bruker

AVANCE 400 MHz NMR spectrometer at 300 K operating at 400.1 MHz for 1H under

TopSpin (version 2.0, Bruker Biospin, Karlsruhe) and equipped with a BBFO-z-atm probe

with actively shielded z-gradient coil capable of delivering a maximum gradient strength of

54 G cm-1. A Bruker pulse program dstegp3s with a double stimulated echo gave Diffusion-

ordered NMR data. Sine-shaped gradient pulses were used with a duration of 4 ms together

with a diffusion period of 100 ms. Gradient recovery delays of 200 μs followed the

application of each gradient pulse. Fourir transformation generates pseudo-2D data by of the

time-domain data. DOSY plot were generated by use of DOSY processing module of

TopSpin. Diffusion coefficients were calculated by fitting intensity data to the Stejskal-

Tanner expression. Accurate Molecular Weight and aggregation state of compounds present

in solution was determine by using external calibration curves with normalized diffusion

coefficients as reported by Stalke.1 The number of species present in solution was obtained by

using the diffusion coefficients for the signals corresponding to the corresponding compound.

Samples preparation for DOSY NMR studies: d8-Toluene solutions of compounds 4, 6, 8

and 9 with a concentration of between 15-50 mM were prepared and added into an NMR tube

containing equimolar amounts of TMS as internal standard to carry out 1H NMR studies

presented herein.

1H DOSY NMR study of 2 in d8-toluene at 300 K

Figure S38. 1H DOSY NMR of 2 in d8-toluene at 300 K.

Dref = Diffusion Coefficient Internal Reference (TMS) [m2/s]

Dx = Diffusion Coefficient Analyte [m2/s]

LogDx,norm = normalized Diffusion Coefficient Analyte

Calculation of logDx,norm allows to estimate MWs of analytes from their diffusion coefficients.

Table S2. Diffusion coefficients for the internal reference (TMS) and for the species present in d8-toluene solution. Calculation of logDx,norm.

Dref TMS (m2s-1) Dx (m2s-1) LogDx,norm

2.149E-9 9.268 E-10 -9.1098

The diffusion coefficient value obtained for 2 in d8-toluene from 1H DOSY NMR study was

compared to the diffusion coefficients of the homometallic species LiHMDS (Table S4) and

CsHMDS (Table S6) in the same deuterated solvent. The diffusion coefficient for 2 appears

in a middle way between the diffusion coefficients obtained from the homometallic

counterparts building 2.

1H DOSY NMR study of 3 in d8-toluene at 300 K

Figure S39. 1H DOSY NMR of 3 in d8-toluene at 300 K

Table S3. Diffusion coefficients for the internal reference (TMS) and for the species present in d8-toluene solution. Calculation of logDx,norm.

Dref TMS (m2s-1) Dx (m2s-1) LogDx,norm

2.016E-9 8.654E-10 -9.1118

The diffusion coefficient value obtained for 3 in d8-toluene from 1H DOSY NMR study was

compared to the diffusion coefficients of the homometallic species NaHMDS (Table S5) and

CsHMDS (Table S6) in the same solvent. The diffusion coefficient for 3 appears in a middle

way between the diffusion coefficients obtained from the homometallic counterparts building

3.

1H DOSY NMR study of LiHMDS in d8-toluene at 300 K

Figure S40. 1H DOSY NMR of LiHMDS in d8-toluene at 300 K.

Table S4. Diffusion coefficients for the internal reference (TMS) and for the species present in d8-toluene solution. Calculation of logDx,norm.

Dref TMS (m2s-1) Dx (m2s-1) LogDx,norm

2.353E-9 1.255E-9 -9.0175

1H DOSY NMR study of NaHMDS in d8-toluene at 300 K

Figure S41. 1H DOSY NMR of NaHMDS in d8-toluene at 300 K

Table S5. Diffusion coefficients for the internal reference (TMS) and for the species present in d8-toluene solution. Calculation of logDx,norm.

Dref TMS (m2s-1) Dx (m2s-1) LogDx,norm

2.003E-9 8.875E-10 -9.0980

1H DOSY NMR study of CsHMDS in d8-toluene at 300 K

Figure S42. 1H DOSY NMR of CsHMDS in d8-toluene at 300 K

Table S6. Diffusion coefficients for the internal reference (TMS) and for the species present in d8-toluene solution. Calculation of logDx,norm.

Dref TMS (m2s-1) Dx (m2s-1) LogDx,norm

2.097E-9 8.764E-10 -9.1234

1H DOSY NMR study of 6 in d8-toluene at 300 K

Figure S43. 1H DOSY NMR of 6 in d8-toluene at 300 K

Table S7. Diffusion coefficients for the internal reference (TMS) and for the species present in d8-toluene solution. Calculation of logDx,norm.

Dref TMS (m2s-1)

Dx SiMe3

in 6 (m2s-1)Dx

TMEDA in 6 (m2s-1)

Dx 6 (m2s-1)

Dx free TMEDA (m2s-

1)

Dx CsHMDS (m2s-1)

2.178E-9 9.583E-10 1.805E-9 6.11E-10 2.00E-9 8.764E-10

The different values obtained for the diffusion coefficients of the HMDS and TMEDA

ligands in 6 is an indicative that the two moieties are not part of the same molecule in arene

solvents. The expected diffusion coefficient for free TMEDA presents a value of 2.00E-9, a

bigger diffusion coefficient than that obtained for TMEDA in 6 (Dx TMEDA = 1.805E-9). In

this line, the diffusion coefficient for the HMDS group in 6 (Dx SiMe3 = 9.583E-10) is

bigger than the expected diffusion coefficient for 6 (6.11E-10). This result is in agreement

with a competition between the bidentate ligand (TMEDA) and molecules of solvent (d8-

toluene) to coordinate the cesium cation. Thus, the smaller diffusion coefficient obtained for

the TMEDA signal in 6 compared to the expected value for free TMEDA suggests that the

ligand is coordinating to the cesium atom and thus the molecular weight of the species in

solution is higher than that of the free ligand. For the same reason, the higher diffusion

coefficient obtained for the SiMe3 group in 6 compared to the expected for 6, is due to de-

coordination of the ligand from the cesium cation explained by a coordination competition

stablished with the solvent, and giving a species in solution with a smaller molecular weight.

1H DOSY NMR study of 8 in d8-toluene at 300 K

Figure S44. 1H DOSY NMR of 8 in d8-toluene at 300 K

Table S8. Diffusion coefficients for the internal reference (TMS) and for the species present in d8-toluene solution. Calculation of logDx,norm

Dref TMS (m2s-1)

Dx SiMe3 in 6 (m2s-1)

Dx Me6TREN in 6 (m2s-1)

Dx CsHMDS·Me6TREN (m2s-1)

Dx Me6TREN (m2s-1)

2.037E-9 9.038E-10 1.0148E-9 6.92E-10 1.240E-9

The different values obtained for the diffusion coefficients of the HMDS and Me6TREN

ligands conforming 8 is an indicative that the two moieties are not part of the same molecule

in arene solvents. The expected diffusion coefficient for free Me6TREN presents a value of

1.24E-9, a bigger diffusion coefficient than that obtained for Me6TREN in 8 (Dx Me6TREN =

1.014E-9). In this line, the diffusion coefficient for the HMDS group in 8 (Dx SiMe3 =

9.038E-10) is bigger than the expected diffusion coefficient for CsHMDS·Me6TREN

(6.92E-10). This result is in agreement with a competition between the tetradentate ligand

(Me6TREN) and molecules of solvent (d8-toluene) to coordinate the cesium cation. Thus, the

smaller diffusion coefficient obtained for the Me6TREN signal in 8 compared to the expected

value for free Me6TREN suggests that the ligand is coordinating to the cesium atom and thus

the molecular weight of the species in solution is higher than that of the free ligand. For the

same reason, the higher diffusion coefficient obtained for the SiMe3 group in 8 compared to

the expected for 8, is due to de-coordination of the ligand from the cesium cation explained

by a coordination competition stablished with the solvent, and giving a species in solution

with a smaller molecular weight.

1H DOSY NMR study of 9 in d8-toluene at 300 K

Figure S45. 1H DOSY NMR of 9 in d8-toluene at 300 K

Table S9. Diffusion coefficients for the internal reference (TMS) and for the species present in d8-toluene solution. Calculation of logDx,norm

Dref TMS (m2s-1) Dx SiMe3 (m2s-1)

Dx TMEEA (m2s-1) Dx 9 (m2s-1)

Dx free TMEEA

(m2s-1)

2.074E-9 8.755E-10 8.351E-10 6.930E-10 1.030E-9

The different values obtained for the diffusion coefficients of the HMDS and TMEEA

ligands conforming 9 is an indicative that the two moieties are not part of the same molecule

in arene solvents. The expected diffusion coefficient for free TMEEA presents a value of

1.030E-9, a bigger diffusion coefficient than that obtained for TMEEA in 9 (Dx TMEEA =

8.351E-10). In this line, the diffusion coefficient for the HMDS group in 9 (Dx SiMe3 =

8.755E-10) is bigger than the expected diffusion coefficient for 9 (6.93E-10). This result is in

agreement with a competition between the heptadentate ligand (TMEEA) and molecules of

solvent (d8-toluene) to coordinate the cesium cation. Thus, the smaller diffusion coefficient

obtained for the TMEEA signal in 9 compared to the expected value for free TMEEA

suggests that the ligand is coordinating to the cesium atom and thus the molecular weight of

the species in solution is higher than that of the free ligand. For the same reason, the higher

diffusion coefficient obtained for the SiMe3 group in 9 compared to the expected for 9, is due

to de-coordination of the ligand from the cesium cation explained by a coordination

competition stablished with the solvent, and giving a species in solution with a smaller

molecular weight.

References

1. Neufeld, R.; Stalke, D., Chem. Sci. 2015, 6, 3354-3364.