Highly dissymmetric chelate coordination of 3,4,7,8-tetramethyl-1,10-phenanthroline to CuI(SR)

Article abstract of DOI:10.1039/a708867a

Not only Au^I and Hg^II species but also Cu^I(SR) fragments can bind in a highly dissymmetrical fashion to symmetrical diimine chelate ligands; the 2 + 1 coordination arrangement observed for the metal in two complexes (tmphen)Cu(SR) (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) is characterised by obtuse angles α[N(1)-Cu-S] > 159° and by two very different distances Cu-N(1) and Cu-N(2).

Full text of DOI:10.1039/a708867a

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Highly dissymmetric chelate coordination of
3,4,7,8-tetramethyl-1,10-phenanthroline to CuI(SR)
Andreas F. Stange, Torsten Sixt and Wolfgang Kaim*
Institut fu¨r Anorganische Chemie, Universita¨t Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
6a
Not only AuI and HgII species but also CuI(SR) fragments
can bind in a highly dissymmetrical fashion to symmetrical
diimine chelate ligands; the 2 + 1 coordination arrangement
observed for the metal in two complexes (tmphen)Cu(SR)
[(bpy)Au(PPh3)]PF6 and [(bpy)HgMe]NO3 (Table 1; bpy =
2,2A-bipyridine).6b Ligands, especially thiolates, with steric bulk
may cause a similar distortion from the trigonal geometry of d10
metal centres as has been realized in the T-shaped (Et2O)Z-
7b
(tmphen
=
3,4,7,8-tetramethyl-1,10-phenanthroline) is
nII(SC6H2But3-2,4,6)2 and, in attenuated form, with the
characterised by obtuse angles a[N(1)–Cu–S] > 159° and by
compound (phen)Cu[SSi(OBut)3] (phen = 1,10-phenanthroli-
ne).7b
two very different distances Cu–N(1) and Cu–N(2).
The copper(i) state is characterised by the lack of a clear
preference for specific coordination numbers (CN) or coordi-
nation geometries, the most common arrangements being close
to tetrahedral (CN 4) or trigonal planar (CN 3).1,2 Higher and
lower coordination numbers, in particular CN 2, have also been
documented.2
In probing copper–thiolate–N-chelate ligand chemistry to
mimic the CuA dinuclear electron transfer center of enzymes3
we reacted the a-diimine ligand 3,4,7,8-tetramethyl-1,10-phe-
nanthroline (tmphen)4 with electrolytically5 obtained 2,4,6-tri-
methyl- and 2,6-diphenyl-thiophenolatocopper(i), Cu(SMes)
and Cu(SDpp). The result† was not a di- or tetra-nuclear
arrangement3c,d but mononuclear copper(i) complexes which
could be crystallised for structural characterisation (Figs. 1 and
2).‡
C(115)
C(16)
C(15)
C(114)
C(14)
C(18)
C(17)
C(13)
C(19)
C(112)
C(116)
C(111)
C(12)
C(110)
C(5)
C(113)
N(2)
N(1)
C(11)
C(6)
C(4)
C(9)
Cu
C(8)
C(1)
C(3)
C(7)
C(2)
S
Fig. 1 Molecular structure of the metal complex in (tmphen)Cu(S-
Mes)·0.5C3H6O with atom numbering. Selected bond lengths (Å) and
angles (°): Cu–N(1) 1.976(2), Cu–N(2) 2.159(2), Cu–S 2.1470(8), S–C(1)
1.787(3); N(1)–Cu–N(2) 80.4(1), N(1)–Cu–S 159.13(8), S–Cu–N(2)
120.48(7), C(1)–S–Cu 98.7(1). Cu lies in the S–N(1)–N(2) plane; torsional
angles (°): N(1)–Cu–S–C(1) 2166.96(2), N(2)–Cu–S–C(1) 13.1(1).
Copper(i) does not normally display the same strong
preference for a coordination number of two with linear
coordination geometry as do gold(i) or mercury(ii) centres, yet
the list in Table
1
illustrates that the complexes
(tmphen)Cu(SR) exhibit unusually distorted geometries as
evident from very obtuse angles a and large differences
between the distances Cu–N(1) and Cu–N(2), despite the formal
equivalence of both nitrogen donor sites and the symmetry of
the aryl groups, R (Table 1).
C(15)
C(115)
C(17)
C(114)
C(16)
C(18)
C(13)
C(12)
C(14)
C(112)
C(111)
C(116)
C(31)
C(19)
C(110)
C(113)
N(1)
N(2)
C(11)
Cu
N(1)
C(22)
S
C(6)
C(21)
g
C(1)
C(32)
N(2)
C(2)
M
a
b
X
Fig. 2 Molecular structure of (tmphen)Cu(SDpp) with atom numbering.
Selected bond lengths (Å) and angles (°): Cu–N(1) 1.972(4), Cu–N(2)
2.172(4), Cu–S 2.1687(14), S–C(1) 1.775(5), C(21)–C(22) 1.388(7);
N(1)–Cu–N(2) 79.9(2), N(1)–Cu–S 164.37(12), S–Cu–N(2) 115.68(12),
C(1)–S–Cu 97.8(2). Cu lies 0.026(2) Å over the S–N(1)–N(2) plane;
torsional angles (°): N(1)–Cu–S–C(1) 2136.1(5), N(2)–Cu–S–C(1)
50.2(2).
Gold(i) or mercury(ii) centres which strongly prefer the linear
geometry can be forced to accept a third donor atom via chelate
coordination. Structurally characterised examples related to the
neutral species (tmphen)Cu(SR) include the ionic systems
Table 1 Geometrical parameters for complexes with 2 + 1 coordination arrangement
Complex
a/°
b/°
g/°
M–N(1)/Å
M–N(2)/Å
Ref.
(tmphen)Cu(SDpp)
(tmphen)Cu(SMes)
(phen)Cu[SSi(OBut)3]
[(bpy)Au(PPh3)]+
[(bpy)HgMe]+
164.4
159.1
144.6
157.4
164.0
159.6a
115.7
120.5
133.5
130.4
126.0
—
79.9
80.4
80.9
71.4
69.4
—
1.972
1.976
2.031
2.166
2.236
—
2.172
2.158
2.108
2.406
2.421
—
This work
This work
7(b)
6(a)
6(b)
(Et2O)Zn(SC6H2But3)2
7(a)
a Angle S(1)–Zn–S(2).
Chem. Commun., 1998
469

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ml toluene. After reflux for 1 h the clear brownish solution was filtered hot,
and careful cooling produced 50 mg (24%) of the compound, partially as
single crystals suitable for X-ray diffraction. Correct elemental analysis (C,
300 K
1
H, N). H NMR (CD2Cl2, 300 K): d 2.45 (s, 6 H, 3,8-CH3), 2.70 (s, 6 H,
4,7-CH3), 6.79 (t, J 7.4 Hz, 2 H, aryl-H), 6.96–7.05 (m, 5 H, aryl-H),
7.35–7.50 (m, 6 H, aryl-H), 8.11 (s, 2 H, 5,6-H), 8.40 (br s, 2 H, 2,9-H).
Selective broadening of the resonances was observed upon cooling to 198
K (Fig. 3).
‡
Crystallography: (tmphen)Cu(SMes)·0.5C3H6O: C25H27CuN2S-
·0.5C3H6O, M = 480.16, crystal size 0.4 3 0.4 3 0.4 mm, monoclinic,
space group P21/n (no. 14), a 8.1319(7), b 14.8164(12), c
19.6605(12) Å, b = 98.388(8)°, U = 2343.5(3) Å3, Dc = 1.351 g cm23
253 K
198 K
=
=
=
,
m(Mo-Ka) = 1.039 mm21, F(000) = 994, Wyckoff scans, 6561 measured
reflections, 6156 independent reflections, 5830 reflections used for
refinement, Lorentz polarisation, R = 0.0501 for 4244 reflections with I >
2s(I); 183 K, Siemens P4 diffractometer with graphite monochromator and
Mo-Ka radiation (l = 0.71073 Å). The structure was solved by direct
methods (Siemens SHELXTL-PC) and refined (SHELXL-93) by full-
matrix least squares on F2 (362 parameters). One half equivalent of a
solvent molecule had to be included. Hydrogen atoms were introduced at
calculated positions and refined freely; (tmphen)Cu(SDpp): C34H29CuN2S,
M = 561.19, crystal dimensions 0.4 3 0.4 3 0.3 mm, monoclinic, space
group P21/n (no. 14), a = 11.949(2), b = 13.284(2), c = 17.636(2) Å, b =
104.56(1)°, U = 2709.5(6) Å3, Dc = 1.376 g cm23, m(Mo-Ka) = 0.909
mm21, F(000) = 1168, Wyckoff scans, 6188 measured reflections, 5971
independent reflections, 5499 reflections used for refinement, Lorentz
polarisation, R = 0.0687 for 3490 reflections with I > 2s(I); 183 K,
Siemens P4 diffractometer with graphite monochromator and Mo-Ka
radiation (l = 0.71073 Å). The structure was solved by direct methods
(Siemens SHELXTL-PC) and refined (SHELXL-93) by full-matrix least
squares on F2 (430 parameters). Hydrogen atoms were introduced at
calculated positions and refined freely. CCDC 182/737.
8
7
6
5
d
4
3
2
Fig. 3 Temperature-dependent 1H NMR spectra of (tmphen)Cu(SDpp) in
CD2Cl2 (300, 253 and 198 K, from top to bottom; 250 MHz)
The unsymmetrical coordination of the chelate ligand to the
CuI center as observed in the solid state is probably responsible
for the selective broadening in the 1H NMR spectrum of
(tmphen)Cu(SDpp) (Fig. 3).
These observations suggest a low but non-negligible barrier
for the ‘movement’ of Cu between two equivalent energy
minimum sites, separated by ca. 0.28 Å. No intermolecular
interactions were recognised in the crystal structures which can
be made responsible for this unusual copper(i)–thiolate3c,d,8
coordination arrangement. To rationalise the observed dis-
symmetry we thus invoke the strong s and p donor effect of
thiolate groups SR and the donor substitution of the a-diimine
tmphen.4 There appears to be no need then for full coordination
of a third donor atom to the electron-rich copper(i) centres,
leaving the inevitably close second nitrogen atom N(2) of the
chelate ligand as a lesser coordinated donor centre to result in
the observed coordination number 2 + 1.
1 H. tom Dieck and L. Stamp, Z. Naturforsch., Teil B, 1990, 45, 1369;
M. J. Begley, P. Hubberstey, C. E. Russell and P. H. Walton, J. Chem.
Soc., Dalton Trans., 1994, 2483; A. Mu¨ller, H. Bo¨gge and U.
Schimanski, Inorg. Chim. Acta, 1980, 45, L249.
2 C. E. Holloway and M. Melnik, Rev. Inorg. Chem., 1995, 15, 147.
3 (a) H. Bertagnolli and W. Kaim, Angew. Chem., 1995, 107, 847; Angew.
Chem., Int. Ed. Engl., 1995, 34, 771; (b) W. Kaim and J. Rall, Angew.
Chem., 1996, 108, 47; Angew. Chem., Int. Ed. Engl., 1996, 35, 43; (c)
A. F. Stange, E. Waldho¨r, M. Moscherosch and W. Kaim, Z.
Naturforsch., Teil B, 1995, 50, 115; (d) A. F. Stange, K.-W.
Klinkhammer and W. Kaim, Inorg. Chem., 1996, 35, 4087.
4 A. Klein, W. Kaim, E. Waldho¨r and H.-D.Hausen, J. Chem. Soc., Perkin
Trans. 2, 1995, 2121.
Notes and References
5 M. C. Chakravorti and G.V. B. Subrahmanyan, Coord. Chem. Rev.,
1994, 135/136, 65.
* E-mail: kaim@iac.uni-stuttgart.de
† Synthesis: Arylcopper(i) precursors were obtained by electrolysing5
solutions of the thiophenols9,10 in acetonitrile–2 mmol dm23 NBu4ClO4 in
a cell containing a copper anode.
6 (a) W. Clegg, Acta Crystallogr., Sect. B, 1976, 32, 2712; (b) A. J. Canty,
A. Marker and B. M. Gatehouse, J. Organomet. Chem., 1975, 88, C31;
A. J. Canty and A. Marker, Inorg. Chem., 1976, 15, 425.
7 (a) P. P. Power and S. C. Shoner, Angew. Chem., 1990, 102, 1484;
Angew. Chem., Int. Ed. Engl., 1990, 29, 1403; (b) B. Becker, W.
Wojnowski, K. Peters, E.-M. Peters and H. G. von Schnering,
Polyhedron, 1992, 11, 613.
8 M. D. Janssen, D. M. Grove and G. van Koten, Prog. Inorg. Chem.,
1997, 46, 97.
9 P. J. Blower, J. R. Dilworth, J. P. Hutchinson and J. A. Zubieta, J. Chem.
Soc., Dalton Trans., 1985, 1533.
(2,4,6-Trimethylthiophenolato)(3,4,7,8-tetramethyl-1,10-phenanthrol-
ine)copper(i) was prepared by adding 250 mg (1.18 mmol) of the
thiolatocopper precursor to a suspension of 278 mg (1.18 mmol) tmphen in
20 ml toluene. After reflux for 2.5 h the clear brownish solution was filtered
hot, cooling produced 352 mg (62%) of (tmphen)Cu(SMes)·C7H8. Single
crystals suitable for X-ray diffraction were obtained from acetone as
(tmphen)Cu(SMes)·0.5C3H6O (correct C, H, N elemental analysis). 1H
NMR (CD2Cl2, 300 K): d 2.16 (s, 6 H, Mes-4-CH3), 2.41 (s, 24 H, tmphen-
3,8-CH3 and Mes-2,5-CH3), 2.65 (s, 6 H, tmphen-4,7-CH3), 6.66 (s, 4 H,
Mes-3,5-H), 8.03 (s, 4 H, tmphen-5,6-H), 8.34 (s, 4 H, tmphen-2,9-H).
(2,6-Diphenylthiophenolato)(3,4,7,8-tetramethyl-1,10-phenanthrol-
ine)copper(i) was prepared by adding 120 mg (0.37 mmol) of the
thiolatocopper precursor to a solution of 87 mg (0.37 mmol) tmphen in 25
10 P. T. Bishop, J. R. Dilworth, T. Nicholson and J. Zubieta, J. Chem. Soc.,
Dalton Trans., 1991, 385.
Received in Basel, Switzerland, 12th June 1997; revised manuscript
received 2nd December 1997; 7/08867A
470
Chem. Commun., 1998