I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

1

Regioselectivity of the C-metalation of 6-furylpurine:

importance of directing effects

Indranil Sinha, Alexander Hepp, Birgitta Schirmer, Jutta Kösters, Johannes Neugebauer,

Jens Müller*

I. Sinha, A. Hepp, J. Kösters, J. Müller

Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität

Münster, Corrensstr. 28/30, 48149 Münster (Germany)

Fax: (+49) 251 83 36007

E-mail: mueller.j@uni-muenster.de

Homepage: www.muellerlab.org

I. Sinha, J. Müller

NRW Graduate School of Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstr.

28/30, 48149 Münster (Germany)

B. Schirmer, J. Neugebauer

Organisch-Chemisches Institut and Center for Multiscale Theory and Computation,

Westfälische Wilhelms-Universität Münster, Corrensstr. 40, 48149 Münster (Germany)

Supporting Information

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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Table S1. Selected bond lengths and angles of 1.

Bond length / Å Bond angle / °

Pt1–C3* 2.029(3) C3*–Pt1–N7 90.0(1)

Pt1–N7 2.053(3) C1od–Pt1–N7 91.7(1)

Pt1–C1od 2.267(3) C2od–Pt1–N7 94.3(1)

Pt1–C2od 2.292(3) C1od–Pt1–C3* 159.1(1)

Pt1–C5od 2.159(3) C2od–Pt1–C3* 165.0(1)

Pt1–C6od 2.172(3)

 

Table S2. Selected bond lengths and angles of 2.

Bond length / Å Bond angle / °

Pd1–C3* 1.982(5) C3*–Pd1–N7 89.6(2)

Pd1–N7 2.005(4) N1a–Pd1–N1b 87.2(2)

Pd1–N1a 2.003(5) N1a–Pd1–N7 176.7(2)

Pd1–N1b 2.085(5) N1b–Pd1–C3* 178.8(2)

Pd2–N1 2.006(4) N1–Pd2–N1c 178.1(2)

Pd2–N1c 2.001(4) Cl1–Pd2–N1d 177.6(1)

Pd2–N1d 2.001(5) N1–Pd2–Cl1 88.7(1)

Pd2–Cl1 2.257(1) N1c–Pd2–N1d 91.8(2)

Table S3. Crystallographic data for compounds 1, 2, and 3.

1 2 3

empirical formula C19H20Cl4N4O5Pt C22H25B2ClF8N10OPd2 C10H9ClHgN4O7

formula weight 721.28 867.39 533.25

crystal system Triclinic triclinic triclinic

space group P–1 P–1 P–1

a, b, c / Å 7.0458(3), 13.6789(7),

13.7056(6)

10.6028(9), 12.389(1), 14.154(1)

7.9691(6), 8.4518(6),

11.3366(8)

, , / ° 65.088(1), 79.045(1),

75.100(1)

65.221(2), 85.098(2),

70.440(2)

110.039(2), 96.654(2),

100.234(2)

V / Å3 1152.70(9) 1587.3(2) 692.90(9)

Z 2 2 2

calcd / g cm–3 2.078 1.815 2.556

(MoK) / mm–1 6.590 1.300 11.345

crystal size / mm 0.03 × 0.06 × 0.28 0.04 × 0.14 × 0.21 0.13 × 0.17 × 0.25

temperature / K 153(2) 153(2) 90(2)

min, max / ° 2.77, 30.05 1.92, 27.88 2.63, 30.06

dataset –9:9, –19:19, –19:19 –13:13, –16:16, –18:18 –11:11, –11:11, –15:15

tot., uniq. data 18597, 6683 18302, 7380 7221, 3918

observed data [I > 2(I)] 6374 5911 3837

Nref, Npar 6683, 299 7380, 422 3918, 225

R, wR2, S [I > 2(I)] 0.0267, 0.0703, 1.066 0.0541, 0.1501, 1.160 0.0265, 0.0705, 1.108

min. and max. resd. dens. /

e Å–3

4.58, –1.81 1.86, –1.18 3.35, –1.60

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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Figure S1. Coordination environment of Hg1 in complex 3. The following symmetry operations apply:

a) 1–x, 2–y, 1–z; b) 1–x, 1–y, 1–z; c) 1–x, 1–y, –z; d) –x, 2–y, 1–z.

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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General experimental information.

All solvents were dried prior to their use. 9-Methyl-6-furylpurine (H6FP) was synthesized according to a

recently reported procedure.1 ESI-MS spectra were measured on an LTQ Orbitrap XL (Thermo

Scientific, Bremen, Germany), equipped with the static nanospray probe (slightly modified to use self-

drawn glass nanospray capillaries). The elemental analyses were recorded on a Vario EL III CHNS

analyser. NMR spectra were recorded at 300 K on Bruker Avance (I) 400 and Avance (III) 400

spectrometers and referenced to the residual solvent peak ( = 1.94 ppm, CD3CN). Single-crystal X-ray

diffraction data were collected with graphite-monochromated Mo K radiation ( = 0.71073 Å) on a

Bruker D8 Venture diffractometer. The structures were solved by direct methods and were refined by

full-matrix, least squares on F2 by using the SHELXTL and SHELXL-97 programs.2

Synthesis of [Pt(6FP)(cod](ClO4) (1). A suspension of [PtCl2(cod)] (50 mg, 0.13 mmol) and AgNO3 (44

mg, 0.26 mmol) in water (5 mL) was stirred for 18 h in the absence of light at 60 °C. The resulting mixture

was cooled (ice bath) and filtered through celite to remove the AgCl precipitate. The filtrate (pH 3.1) was

added to a solution of H6FP (26 mg, 0.13 mmol) in water (2 mL, pH 5.5) followed by stirring for 18 h at

60 °C, resulting in a final pH of 3.2. The yellow solution was filtered to a solution of NaClO4 (32 mg, 0.26

mmol) in water (2 mL) and stirred for 6 h, resulting in the formation of the desired compound as a yellow

precipitate. Caution! Perchlorate salts of metal complexes with organic ligands are potentially explosive.

The product was isolated by filtration and washed with cold water (5 mL) and diethyl ether (5 mL). Yield:

53 mg, 65%. The complex was crystallized by vapor diffusion crystallization in acetonitrile with

chloroform as antisolvent. After one week, small crystals appeared which proved to be 1 · CHCl3

according to single-crystal X-ray diffraction analysis. 1H NMR (CD3CN, 400 MHz): 9.08 (s, 1H, H2,

1JH,C = 207 Hz), 8.70 (s, 1H, H8, 3JH,Pt = 16.6 Hz, 1JH,C = 214 Hz), 7.88 (d, 1H, H5*), 6.59 (t, 1H, H4*, 3JH,Pt = 20.5 Hz, 1JH,C = 175 Hz), 6.25 (t, 2H, H1 (cod), H2 (cod), 2JH,Pt = 36.3 Hz), 5.78 (t, 2H, H5 (cod),

H6 (cod), 2JH,Pt = 68.8 Hz), 4.00 (s, 3H, CH3), 2.74 (m, 4H, H4 (cod), H7 (cod)), 2.66 (m, 4H, H3 (cod),

H8 (cod)). 13C NMR (CD3CN, 101 MHz): 156.2 (C2), 150.7 (C8, 2JC,Pt = 40.1 Hz), 149.8 (C4), 148.2

(C5*), 145.9 (C6), 144.0 (C2*), 127.3 (C3*), 117.5 (C4*, 2JC,Pt = 30.6 Hz), 122.6 (C5), 111.5 (C1, C2

(cod), 1JC,Pt = 58.6 Hz), 96.4 (C5, C6 (cod), 1JC,Pt = 174.2 Hz), 32.1 (C4, C7 (cod), 2JC,Pt = 16 Hz), 32.0

(C9), 28.7 (C3, C8 (cod), 2JC,Pt = 13.8 Hz). ESI-MS m/z: [M]+ 502.1197 (calcd. 502.1207). Elemental

analysis (%): C 35.7, H 3.4, N 9.2; calcd. for C18H19ClN4O5Pt: C 35.9, H 3.2, N 9.3.

Synthesis of [Pd2(6FP)(MeCN)4Cl](BF4)2 (2). A solution of PdCl2 (40 mg, 0.23 mmol) and AgBF4 (86

mg, 0.44 mmol) in acetonitrile (7 mL) was stirred for 18 h in the absence of light at 60 °C. The resulting

mixture was cooled (ice bath) and filtered through celite to remove the precipitated AgCl. The filtrate

was added to a solution of H6FP (86 mg, 0.43 mmol) in acetonitrile (2 mL) and was stirred for 18h at

60 °C. The solution turned yellow, and the solvent was removed in vacuo. The resulting solid was

washed with CH2Cl2 (5 mL) and diethyl ether (5 mL), affording the product as a yellow precipitate. Yield:

94 mg. The complex was crystallized by vapor diffusion crystallization in acetonitrile with chloroform as

antisolvent. After a week, small crystals appeared which proved to be 2 · 2 CH3CN, according to single

crystal X-ray diffraction analysis. 1H NMR (CD3CN, 400 MHz): 8.96 (s, 1H, H2, 1JH,C = 220 Hz), 8.93

(s, 1H, H8, 1JH,C = 224 Hz), 8.09 (d, 1H, H5*), 6.98 (t, 1H, H4*), 4.09 (s, 3H, CH3). 13C NMR (CD3CN,

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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101 MHz): 153.2 (C8), 153.0 (C5*), 150.7 (C4), 150.5 (C6), 148.0 (C2), 136.6 (C3*), 134.2 (C2*), 123.2

(C4*), 121.5 (C5), 32.8 (C9). 11B NMR (CD3CN, 128 MHz): –1.2. 19F NMR (CD3CN, 376 MHz): –

151.6. As a side product (ca. 30% by NMR), a mononuclear C-metalated complex tentatively assigned

as [Pd(6FP)(MeCN)2](BF4) was formed. 1H NMR (CD3CN, 400 MHz): 9.31 (s, 1H, H2, 1JH,C = 216 Hz),

8.75 (s, 1H, H8), 8.30 (d, 1H, H5*), 7.01 (t, 1H, H4*), 3.99 (s, 3H, CH3). 13C NMR (CD3CN, 101 MHz):

156.0 (C2), 151.0 (C8), 150.0 (C5*), 149.5 (C4), 146.1 (C6), 138.4 (C2*), 129.4 (C3*), 123.0 (C5), 122.2

(C4*), 32.3 (CH3). ESI-MS m/z: [Pd(6FP)(CH3CN)]+ 345.9916 (calcd. 345.9920).

Synthesis of [Hg2(6FP)2](ClO4)2 · 4 H2O (3). To a solution of H6FP (30 mg, 0.15 mmol) in water (5 mL,

pH 5.4), a solution of Hg(ClO4)2 (30 mg, 75 mol) in water (2 mL, pH 2.2) was added, and the resulting

solution was stirred for 18 h at 60 °C. Caution! Perchlorate salts of metal complexes with organic ligands

are potentially explosive. After a while, a colorless precipitate occurred in the initially clear reaction

mixture. The product was isolated by filtration (solution pH: 3.0) and washed with cold water (5 mL) and

diethyl ether (5 mL). Yield: 68 mg, 79%. After two weeks, small crystals suitable for single-crystal X-ray

diffraction analysis were obtained from a mixture of CD3CN and D2O, which proved to be 3. 1H NMR

(CD3CN, 400 MHz): 9.14 (s, 1H, H8), 9.05 (s, 1H, H2, 1JH,C = 210 Hz), 7.88 (d, 1H, H3*), 7.04 (t, 1H,

H4*, 3JH,Hg = 35 Hz), 4.04 (s, 3H, CH3). 13C NMR (CD3CN, 101 MHz): 170.8 (C5*), 154.9 (C2), 152.7

(C4), 151.9 (C8), 149.1 (C2*), 145.4 (C6), 117.7 (C3*), 125.6 (C4*, 2JC,Hg = 371 Hz), 119.8 (C5), 32.4

(CH3) ppm. ESI-MS m/z: [Hg(6FP)(H6FP)]+ 601.1025 (calcd. 601.1024).

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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Figure S2. 1H NMR spectrum of complex 1.

Figure S3. 13C NMR spectrum of complex 1.

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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Figure S4. 1H NMR spectrum of complex 2.

Figure S5. 13C NMR spectrum of complex 2.

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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Figure S6. 1H NMR spectrum of complex 3.

Figure S7. 13C NMR spectrum of complex 3.

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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Figure S8. Experimental and computed ESI mass spectrum of complex 1.

Figure S9. Experimental and computed ESI mass spectrum of complex 2.

Figure S10. Experimental and computed ESI mass spectrum of complex 3.

I. Sinha, A. Hepp, B. Schirmer, J. Kösters, J. Neugebauer, J. Müller Regioselectivity of the C-metalation of 6-furylpurine: importance of directing effects

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References

1. Sinha, I.; Kösters, J.; Hepp, A.; Müller, J., Dalton Trans. 2013, 42, 16080-16089.

2. Sheldrick, G. M., Acta Cryst. 2008, A64, 112-122.

Collection of calculated thermodynamical data and computational details

All calculations have been performed with the TURBOMOLE 6.51 suite of programs. Whenever available

experimental crystal structures were used as starting points for the geometry optimizations. The structures

have been optimized with the hybrid-GGA functional PBE02 applying the D3-dispersion correction with Becke-

Johnson damping (denoted as (BJ)).3,4 This method has been shown to yield very accurate results for transition

metal catalyzed activation reactions.5 The large Gaussian-AO basis set def2-TZVP6 with the corresponding

relativistic effective core potentials (def2-ECP) for Hg7 and the RI approximation8,9 have been used.

All values given below are electronic energies in kcal/mol without ZPVE. The stabilization of the ionic molecules

by solvation is neglected here — this effect is estimated to be small for the reactions under consideration as it

should be of comparable magnitude for reactands and products and thus cancels out in the relative energies.

References

[1] TURBOMOLE, version 6.5, R. Ahlrichs et. al., Universitat Karlruhe 2013; see http://www.turbomole.com.[2] C. Adamo and V. Barone, J. Chem. Phys., 1999, 110, 6158–6170.[3] S. Grimme, J. Antony, S. Ehrlich and H. Krieg, J. Chem. Phys., 2010, 132, 154104.[4] S. Grimme, S. Ehrlich and L. Goerigk, J. Comput. Chem., 2011, 32, 1456–1465.[5] M. Steinmetz and S. Grimme, ChemistryOpen, 2013, 2, 115–124.[6] F. Weigend and R. Ahlrichs, Phys. Chem. Chem. Phys., 2005, 7, 3297–3305.[7] D. Andrae, U. Haeussermann, M. Dolg, H. Stoll and H. Preuss, Theor. Chim. Acta, 1990, 77, 123.[8] K. Eichkorn, O. Treutler, H. Ohm, M. Haser and R. Ahlrichs, Chem. Phys. Lett., 1995, 240, 283–289.[9] C. Hattig and F. Weigend, J. Chem. Phys., 2000, 113, 5154.

Birgitta SchirmerJohannes Neugebauer

Organisch-Chemisches Institut und Center for Multiscale Theory and Computation (CMTC)Westfalische Wilhelms-Universitat MunsterCorrensstr. 40D-48149 Munster

11

O

N

N N

N

O

N

N N

N

O

N

N N

N

+Hg

O

N

N N

N

Hg+

O

N

N N

N

Hg+

0 kcal/mol -1.5 kcal/mol -23.9 kcal/mol

6FP1-α-Hg 6FP1-β'-Hg 6FP1-β-Hg

H6FP2

O

N

N N

N

Hg+

O

N

N N

N

Hg+

O

N

N N

N

+Hg

0 kcal/mol -0.8 kcal/mol -11.9 kcal/mol

N- H6FP2 N

N

-H6FP2

H6FP2-

0 kcal/mol 1.0 kcal/mol

6FP2-α-Hg-H6FP2 6FP2-β'-Hg-H6FP2 6FP2-β-Hg-H6FP2

O

N

N N

N

Hg

O

N

NN

N

Hg

3H6FP1

O

N

N N

N

Hg+

O

N

N N

N

Hg+

O

N

N N

N

+Hg

+5.4 kcal/mol +4.6 kcal/mol -6.2 kcal/mol

N- H6FP1 N

H6FP1 -N

6FP2-α-Hg-H6FP1 6FP2-β'-Hg-H6FP1 6FP2-β-Hg-H6FP1

-H6FP1

5* 4*

3*1*

2*

1

2

3

8

9

76

β' α

β

+0.8 kcal/mol +0.01 kcal/mol -15.9 kcal/mol

6FP2-α-Hg 6FP2-β'-Hg 6FP2-β-Hg

2+

Fig. S11: Compilation of all calculated structures and their electronic energies (gas phase, without ZPVE, in kcal/mol)

relative to the first compound in each box. Numbering for H6FP according to main part of the manuscript.

12

Conformational Considerations

Two conformations are conceivable for the ligand H6FP, one in which the oxygen atom of the furyl moiety is

turned towards the N1 in the purine – denoted H6FP1 from here on – and a second one in which it is turned

towards N7 in the purine – denoted H6FP2. For the separate ligand the former is only slightly more stable by

approx. 1 kcal/mol.

The mercury ion can activate three different C-H bonds in the furyl moiety, the bond α to the oxygen (on C5*),

and the two bonds in β position. Since these two bonds are not equivalent, the position denoted C4* is referred

to as β’.

Due to the complexity of the system a model system was applied in which additional possible ligands of the

mercury dication (water, ClO−4 ) are omitted. If a separate mercury dication activates one of these bonds in

the H6FP molecule, the conformations given in the second box in Fig. S11 are obtained. The relative energies

show that α- and β’-activation are more or less isoenergetic given the error in the method of about 1-2 kcal/mol.

The activation in β position is most favoured as here the cation is stabilized by the lone pair of the spatially

close nitrogen atom N7.

Fig. S12: Calculated structures of 6FP1-β-Hg (left) and 3 (right; coordination depicted by dashed line).

Comparing the energies of two molecules of 6FP1-β-Hg to the energy of the dimer 3 reveals that the two

intermolecular, linear coordinations to N7 in the dimer are by 37.7 kcal/mol more stable than two intramolec-

ular coordinations to N7. The direct formation of 3 from two molecules of 6FP2-α-Hg by coordinating each

Hg cation to the N7 lone pair of the other molecule linearly even amounts to an electronic reaction energy of

−87.0 kcal/mol. These values do not include additional contributions from solvation of the ions, but we estimate

this effect to be small for this reaction and to approximately cancel out since it occurs for reactants as well as

products.

To avoid the intramolecular stabilization effect a model system was created which is closer to the experimen-

tally found dimer 3. In this model system the mercury ion activates a C-H bond in one H6FP molecule while

interacting with the N7-lone pair of a second H6FP molecule. In this way an intermolecular stabilization is

achieved and a linear coordination similar to the one found in 3 is possible.

Since in the dimer both ligands are in the conformation of H6FP2 these were also adapted for the model sys-

13

tem. The resulting energies are given in the third box in Fig. S11. For this model system activation in the α

position is calculated to be the least favourable, β’ is again close in energy while the preferred β position is

about 12 kcal/mol more stable. Closer inspection of the structure with β-activation reveals additional coordina-

tion of Hg to N1 of the activated molecule as well as to the furyl-O in the coordinated ligand as the source of

this stabilization (compare Figs. S13 and S15).

The electronic reaction energy for the formation of 6FP2-α-Hg-H6FP2 from H6FP2 and 6FP2-α-Hg is strongly

negative by −72.8 kcal/mol suggesting a large stabilization from the coordination to another ligand molecule

(β’: −72.7 kcal/mol; β: −67.9 kcal/mol).

Since the interaction between the Hg ion and the oxygen of the coordinated H6FP2 molecule is present in

all three conformers and only relative energies between the conformers are discussed the effect of this coor-

dination to oxygen can be expected to cancel out. The distances for bonds and interactions can be found in

Table S4 below. Table S5 compiles the Wiberg bond indices (WBI) of these contacts and reveals the stabilizing

interactions with N1 and O to be small as compared to the strength of the interaction with N7 and the covalent

single bond to the activated carbon.

For the sake of comparison the conformers 6FP2-Hg-H6FP1 have been investigated as well. In this model sys-

tem a stabilization by the furyl oxygen is not possible as it faces away from the mercury ion. At the same time,

steric hinderance enforces a twist in the furyl-purine leading to a dihedral angle of 39.4◦, 39.6◦ and 36.1◦ for

α, β’ and β, respectively. Thus, the bigger π-system in the original, planar ligand is weakened or even split into

two separate, smaller π-systems for furyl und purine. Accordingly, all 6FP2-Hg-H6FP1 structures are slightly

higher in energy than their 6FP2-Hg-H6FP2 counterparts. In compound β a coordination to N1 stabilizes the

molecule even further (compare Fig. S16).

While the presented systems all originate from activation of a CH-bond by a mercury cation, a reasonable

structure for the coordination of a separate mercury ion to N7 in H6FP could not be obtained.

14

Tab. S4: Geometry data of the investigated structures - bond lengths in A and dihedral angles between furyl and purinesystem in degrees. In all molecules of the types 6FP2-Hg-H6FP1 and 6FP2-Hg-H6FP2 only the dihedral of theN-coordinated ligand is given as the CH-activated ligand is planar.The dimer 3 is centrosymmetric, thus the valuesfor both corresponding bonds are identical.

system Hg–C Hg–N7 Hg–N1 Hg–O dihedral angleA A A A degrees

6FP1-α-Hg 2.078 – – – 0.46FP2-α-Hg 2.079 – – – 7.8

6FP2-α-Hg-H6FP2 2.005 2.097 – 2.733 0.36FP2-α-Hg-H6FP1 2.003 2.104 – – 39.4

6FP1-β’-Hg 2.047 – – – 0.26FP2-β’-Hg 2.050 – – – 7.4

6FP2-β’-Hg-H6FP2 2.006 2.104 – 2.725 0.046FP2-β’-Hg-H6FP1 2.005 2.111 – – 39.6

6FP1-β-Hg 2.041 2.230 – – 0.16FP2-β-Hg 2.007 2.461 – – 0.03

6FP2-β-Hg-H6FP2 2.017 2.107 2.714 2.771 13.16FP2-β-Hg-H6FP1 2.015 2.109 2.748 – 36.1

3 2.017 2.075 – 2.794 0.03

Tab. S5: Wiberg bond indices of the significant bonds in all investigated structures. The dimer 3 is centrosymmetric, thusthe values for both corresponding bonds are identical.

system Hg–C Hg–N7 Hg–N1 Hg–O

6FP1-α-Hg 0.93 – – –6FP2-α-Hg 0.94 – – –

6FP2-α-Hg-H6FP2 1.02 0.47 – 0.076FP2-α-Hg-H6FP1 1.05 0.47 – –

6FP1-β’-Hg 1.03 – – –6FP2-β’-Hg 1.01 – – –

6FP2-β’-Hg-H6FP2 0.97 0.46 – 0.086FP2-β’-Hg-H6FP1 1.00 0.46 – –

6FP1-β-Hg 1.02 0.40 – –6FP2-β-Hg 1.02 0.28 – –

6FP2-β-Hg-H6FP2 0.98 0.46 0.17 0.086FP2-β-Hg-H6FP1 0.98 0.46 0.16 –

3 0.97 0.52 – 0.08

15

Fig. S13: Calculated structure of the model system 6FP2-α-Hg-H6FP2 showing the additional coordination to the furyloxygen of the non-activated ligand (coordination depicted by dashed lines).

Fig. S14: Calculated structure of the model system 6FP2-α-Hg-H6FP1 (coordination depicted by dashed lines).

16

Fig. S15: Calculated structure of the model system 6FP2-β-Hg-H6FP2 showing the additional coordination to the N1 in theactivated and the furyl oxygen in the coorinated ligand (coordination depicted by dashed lines).

Fig. S16: Calculated structure of the model system 6FP2-β-Hg-H6FP1 (coordination depicted by dashed lines).

17