Investigation of putative arene-C-H?π(quasi-chelate ring) interactions in copper(i) crystal structures

Article abstract of DOI:10.1039/c4cc02040e

Evidence for C-H?π(CuCl?HNCS) interactions, i.e. C-H?π(quasi-chelate ring) where a six-membered quasi-chelate ring is closed by an N-H?Cl hydrogen bond, is presented based on crystal structure analyses of (Ph₃P)₂Cu[ROC(S)N(H)Ph]Cl. Similar intramolecular interactions are identified in related literature structures. Calculations suggest that the energy of attraction provided by such interactions approximates 3.5 kcal mol^-1. the Partner Organisations 2014.

Full text of DOI:10.1039/c4cc02040e

ChemComm
View Article Online
View Journal | View Issue
COMMUNICATION
Investigation of putative arene-C–Hꢀꢀꢀp(quasi-chelate
ring) interactions in copper(I) crystal structures†
Cite this: Chem. Commun., 2014,
50, 5984
Chien Ing Yeo,a Siti Nadiah Abdul Halim,a Seik Weng Ng,a Seng Lim Tan,a
Julio Zukerman-Schpector,b Marco A. B. Ferreira*b and Edward R. T. Tiekink*a
Received 19th March 2014,
Accepted 14th April 2014
DOI: 10.1039/c4cc02040e
www.rsc.org/chemcomm
Evidence for C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS) interactions, i.e. C–Hꢀꢀꢀp(quasi- work continues on this phenomenon,6 the role of conjugated or
chelate ring) where a six-membered quasi-chelate ring is closed by an resonance-assisted hydrogen bonded systems, where one of the links
N–HꢀꢀꢀCl hydrogen bond, is presented based on crystal structure within the organic ring is a hydrogen bond rather than a formal
Q
analyses of (Ph3P)2Cu[ROC( S)N(H)Ph]Cl. Similar intramolecular covalent bond, giving rise to quasi-aromatic rings, is less well under-
interactions are identified in related literature structures. Calculations stood.7 Analogous quasi-aromatic rings where one of the constituent
suggest that the energy of attraction provided by such interactions atoms is a metal have received considerably less attention and their
approximates 3.5 kcal molꢁ1
.
putative formation forms the focus of the present communication.
Herein, the observation and theoretical investigation of intra-
Complementing supramolecular synthons based on conventional molecular arene-C–Hꢀꢀꢀp(quasi-chelate rings) interactions in some
hydrogen bonding and coordinate bonds, which remain crucial in (Ph3P)2Cu[ROC(QS)N(H)Ph]Cl complexes are described, as is the
crystal engineering studies, is a myriad of other intermolecular prevalence of analogous interactions in the crystallographic literature.
interactions coming to the fore with the notable example being
The new copper(I) complexes were prepared in response to
halogen bonding.1 Supramolecular association based on p-systems the recently demonstrated anti-cancer potential of platinum8a and
is also well established in all-organic crystal structures and gold8b complexes of thiocarbamides, ROC(QS)N(H)Ar, and the
increasingly, chelate rings are being recognised as being cap- remarkable and selective anti-microbial activity against four
able of forming analogous interactions,2 reflecting their metal- Gram-positive bacteria exhibited by phosphanegold(I) derivatives.8c
loaromatic nature.3 Thus, just as arene rings can associate via The potential of copper(I) complexes as therapeutic agents has
pꢀ ꢀ ꢀp interactions, mixed p(arene)ꢀ ꢀ ꢀp(chelate) interactions can been reviewed recently,9 and so attention was naturally directed to
occur,4a as well as p(chelate)ꢀꢀꢀp(chelate) interactions which are found investigating related phosphanecopper(I) derivatives during which
in up to 40% of certain square planar transition metal complexes and the title complexes, (Ph3P)2Cu[ROC(QS)N(H)Ph]Cl, R = Me (1), Et
exhibit the same attributes as pꢀꢀꢀp interactions involving arene rings, (2) and iPr (3), were synthesised and characterised, including by
such as cooperativity, separation and orientation, i.e. parallel and anti- single crystal X-ray crystallography; see the ESI† for details. Spectro-
parallel.4b As demonstrated by Zaric et al. in their systematic evalua- scopy showed the expected characteristics, with the only feature
´
1
tion of transition metal acetylacetonate crystal structures, chelate rings worth highlighting being the downfield shift of the H resonance
may also function as donors and acceptors of C–Hꢀꢀꢀp interactions due to the acidic proton as the concentration of the solution was
and impart approximately the same energy of stabilisation as for increased, consistent with retention of the N–HꢀꢀꢀCl hydrogen
C–Hꢀꢀꢀp interactions occurring between organic residues.5 While bond in solution (see below), see ESI,† Fig. S1.
The molecular structure of 2 is shown in Fig. 1 and features a
tetrahedrally coordinated Cu(I) centre with the environment defined by
one chlorido, a thione-S and two phosphane-P atoms; the maximum
deviation from regular tetrahedral is found in the P1–Cu–P2 angle of
a Department of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia.
E-mail: Edward.Tiekink@gmail.com; Fax: +60 3 7967 4193; Tel: +60 3 7967 6775
b
´
ˆ
Laboratorio de Cristalografia, Estereodinamica e Modelagem Molecular,
125.099(19)1. An intramolecular N–HꢀꢀꢀCl hydrogen bond is formed
closing a (CuClꢀꢀꢀHNCS) quasi-chelate ring, see the ESI,† Table S2 for
geometric details. The interesting feature of the structure is the relative
orientation of one of the phenyl-H atoms which appears to be directed
toward the centre of the aforementioned ring. The separations between
the phenyl-H atom and each of the constituent atoms of the ring are
given in the caption of Fig. 1, and from these data it is evident that the
´
˜
Departamento de Quımica, Universidade Federal de Sao Carlos, C.P. 676,
˜
Sao Carlos, SP, 13565-905, Brazil. E-mail: marcoantbf@gmail.com;
Fax: +55 16 3351 8350; Tel: +55 16 3351 8208
† Electronic supplementary information (ESI) available: Details of synthesis and
the spectroscopic, crystallographic and theoretical characterisation of new and
literature compounds with C–Hꢀ ꢀ ꢀp(ꢀ ꢀ ꢀClCuSCNH) interactions. CCDC 990503–
990505. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c4cc02040e
5984 | Chem. Commun., 2014, 50, 5984--5986
This journal is ©The Royal Society of Chemistry 2014

View Article Online
Communication
ChemComm
Fig. 2 Search protocols for C–Hꢀ ꢀ ꢀp(CuClꢀ ꢀ ꢀHNCS) interactions: d is the
distance between the ring centroid (Cg) of the quasi-chelate ring and
the H atom; V1 is the vector normal to the plane through the ring; a is the
C–Hꢀ ꢀ ꢀCg angle; b is the angle between the V1 and V2 vectors.
Fig. 1 Molecular structure of 2 showing atom labelling and 70% displace-
ment ellipsoids. The C–H*ꢀ ꢀ ꢀCu, Cl1, S1, N1, C1 and H1n separations are
3.12, 3.41, 2.99, 2.63, 2.88 and 2.48 Å, respectively.
phenyl-H atom is not orientated toward any one atom of the ring but
rather to the centre of the quasi-chelate ring. The distance between further probed to seek intramolecular C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS) con-
phenyl-H and the centroid of the quasi-ring is 2.31 Å and the angle is tacts by adding the following restrictions, Fig. 2. The distance, d, from
1471. By analogy with a C–Hꢀꢀꢀp(arene) interaction, this contact can be the ring centroid (Cg) to the H atom is r3.6 Å6a and the C–HꢀꢀꢀCg
represented as C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS).
angle is in the range 110 r a r 1801. Although the quasi-ring was not
A similar interaction is found in the R = iPr derivative, 3 restricted to be planar, the angle between the normal of the least-
[phenyl-Hꢀꢀꢀquasi-ring centroid = 2.56 Å and angle at H = 1241; see the squares plane through the six atoms and the C–H vector was restricted
ESI,† Fig. S2 for details], but not in the R = Me analogue, 1, where the to r151 to ensure that the C-bound H atom was approximately plumb
shortest Hꢀꢀꢀquasi-ring centroid distance is 3.41 Å. An overlay dia- to the ring. There were 14 structures,11 out of a possible 91, that
gram, ESI,† Fig. S2c, shows that while the overall molecular structures satisfied these criteria; details are summarised in the ESI,† Table S5.
are similar, the phenyl ring forming the C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS)
Twelve of the hits contain phosphane ligands, with seven having
interaction in 2 and 3 is somewhat splayed in 1; the dihedral angles very similar mononuclear structures with ClP2S donor sets as found
between the relevant phenyl ring and the least-squares plane through for 2 and 3;12b–e,h,j–l,o a simple variation is found in one binuclear
the non-hydrogen atoms of the quasi-chelate ring are 36.5(5), 64.02(5) example having bridging bidentate phosphanes.12f Four binuclear
and 55.25(5)1 for 1, 2 and 3, respectively. It is noted that the quasi-ring structures with monodentate phosphane ligands have S12g,n or Cl12i
in 1 (r.m.s. deviation of the five non-hydrogen atoms = 0.1902 Å) is less bridges. The remaining two structures are thione adducts of
planar than the equivalent rings in 2 and 3 (r.m.s. = 0.0997 and CuCl.12a,m In each case the donor H atom was connected to an
0.0898 Å, respectively). In fact the ring in 1 has a distinct envelope aromatic ring. Values of d were in the range 2.28 to 2.92 Å and the a
conformation with the Cu atom lying 0.6751(11) Å above the least- angles varied from 114 to 1631. The planarity of the quasi-chelate ring
squares plane defined by the remaining four non-hydrogen atoms; is not a factor in the formation of C–Hꢀꢀꢀp(quasi-chelate ring)
see ESI,† Table S3. The other difference between the structures is interactions as rms deviations of the five non-hydrogen atoms from
found in the pattern of Cu–ligand bond lengths (see ESI,† Table S4) so their least-squares plane vary from a low 0.0297 to 0.3374 Å (ESI,†
that in 1, the Cu–Cl1 bond length is significantly longer, by 0.03 Å, Table S5). Nor there is a correlation between the planarity of the quasi-
than those in 2 and 3, and the remaining bond lengths in 1 are chelate ring and the values of d or a. This is hardly surprising as
concomitantly shorter cf. to the equivalent bonds in 2 and 3. This is correlations involving weak interactions are notoriously unreliable.13
not related to the nature of the supramolecular aggregation as
In order to investigate the nature of the C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS)
C–HꢀꢀꢀCl interactions are formed in each of the crystal structures; interaction, DFT-D calculations were performed based on the coordi-
ESI,† Fig. S3–S5. In 1 and 2 C–HꢀꢀꢀCl along with C–Hꢀꢀꢀp(arene) nates of one of the literature crystal structures that feature an
contacts lead to a supramolecular layer and a double chain, respec- intramolecular contact, i.e. 4,12o Fig. 3a. As detailed in the ESI,†
tively. In 3, C–HꢀꢀꢀCl, C–HꢀꢀꢀS and C–Hꢀ ꢀ ꢀp(arene) interactions Gaussian09 was used employing the BP86 functional,14a,b including
lead to a supramolecular chain. The crystal packing in 1–3 was also the D3 version of Grimme’s dispersion correction,14c and the second-
evaluated for phenyl embraces (PE), known to be important in order perturbation theory14d with the def2-TZVP basis set.14e,f Initially,
stabilising the crystal structures of phenyl-rich molecules.10 As sum- the non-covalent interactions were calculated in real space based on
marised in the figure captions, ESI,† Fig. S3–S5, the P1-phosphane, the electron density and its reduced gradient using the NCI approach
i.e. not involved in forming the putative C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS) of Yang et al.15 Referring to Fig. 3b and c, the surfaces are coloured
interactions, participates in sextuple PE whereas the P2–phosphane blue, green and red, correlating with strong attractive, weak attractive
ligand forms parallel quadruple PE interactions in 1, double PE in 2 and strong non-bonded overlap, respectively. The NCI analysis15 gives
but no recognisable pattern is observed in 3.
a conical surface pointing to the mass-centre of the ring, representing
The unusual nature of the C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS) contact unambiguously the p-type interaction. An example of the T-shaped
prompted a search of the Cambridge Structural Database (CSD version benzene-dimer can be seen in Fig. 3b. A similar situation was
5.33)11a for analogous interactions using CONQUEST.11b The initial observed for 4, in which the green region indicates a weak attractive
search comprised seeking a specific arrangement of the Cu, Cl, H, N, interaction as commonly presented in p-stacking interactions.
C and S atoms as well as the presence of a N–HꢀꢀꢀCl hydrogen bond to
Additional calculations were conducted to elucidate the
close the ring: this gave rise to a total of 91 hits. This sub-set was metalloaromaticity of the quasi-chelate ring by calculation of
This journal is ©The Royal Society of Chemistry 2014
Chem. Commun., 2014, 50, 5984--5986 | 5985

View Article Online
ChemComm
Communication
´
´
´
´
4 (a) Z. D. Tomic, D. N. Sredojevic and S. D. Zaric, Cryst. Growth Des.,
´
´
2006, 6, 29; (b) D. N. Sredojevic, Z. D. Tomic and S. D. Zaric, Cryst.
Growth Des., 2010, 10, 3901.
ˇ ´
´
´
´
5 M. K. Milcic, V. B. Medakovic, D. N. Sredojevic, N. O. Juranic and
´
S. D. Zaric, Inorg. Chem., 2006, 45, 4755.
6 (a) E. R. T. Tiekink and J. Zukerman-Schpector, Chem. Commun.,
´
´
ˇ ´
2011, 47, 6623; (b) V. B. Medakovic, G. A. Bogdanovic, M. K. Milcic,
´
´
G. V. Janjic and S. D. Zaric, J. Inorg. Biochem., 2012, 117, 157;
(c) S. K. Singh, M. G. B. Drew and N. Singh, CrystEngComm, 2013,
15, 10255.
7 M. Calvin and K. W. Wilson, J. Am. Chem. Soc., 1945, 67, 2003;
M. Palusiak and T. M. Krygowski, Chem. – Eur. J., 2007, 13, 7996;
A. Filarowski and I. Majerz, J. Phys. Chem. A, 2008, 112, 3119;
H. Karabiyik, R. Sevincek, H. Petek and M. Aygun, J. Mol. Model.,
2011, 17, 1295; Y. V. Novakovskaya, Struct. Chem., 2012, 23, 1253;
H. Karabıyık, H. Karabıyık and N. O. Iskeleli, Acta Crystallogr., Sect.
B, 2012, 68, 71; H. Karabıyık, R. Sevincek and H. Karabıyık, J. Mol.
Struct., 2014, 1064, 135.
Fig. 3 (a) Chemical structure of 4, (b) the gradient isosurface of a T-shaped
benzene-dimer (adapted with permission from Yang et al., J. Chem. Theory
Comput. 2011, 7, 625. Copyright 2014 American Chemical Society), and (c)
the gradient isosurface of 4.
ˆ
8 (a) D. Dolfen, K. Schottler, S.-M. Valiahdi, M. A. Jakupec, B. K. Keppler,
E. R. T. Tiekink and F. Mohr, J. Inorg. Biochem., 2008, 102, 2067;
(b) C. I. Yeo, K. K. Ooi, A. Md Akim, K. P. Ang, Z. A. Fairuz,
S. N. B. A. Halim, S. W. Ng, H.-L. Seng and E. R. T. Tiekink, J. Inorg.
Biochem., 2013, 127, 24; (c) C. I. Yeo, J.-H. Sim, C.-H. Khoo, Z.-J. Goh,
K.-P. Ang, Y.-K. Cheah, Z. A. Fairuz, S. N. B. A. Halim, S. W. Ng,
H.-L. Seng and E. R. T. Tiekink, Gold Bull., 2013, 46, 145.
9 C. Santini, M. Pellei, V. Gandin, M. Porchia, F. Tisato and
C. Marzano, Chem. Rev., 2014, 114, 815.
10 I. Dance and M. Scudder, Chem. – Eur. J., 1996, 2, 481; M. Scudder
and I. Dance, J. Chem. Soc., Dalton Trans., 1998, 329.
isotropic nucleus-independent chemical shifts (NICS(ꢁ1)ISO
,
NICS(0)ISO and NICS(1)ISO) at the centroid of 4, using the BP86,
B3LYP and B3PW91 functionals.16a,b The magnetic criterion of
aromaticity was not satisfied, with values in the range of ꢁ1.32 to
0.32 Å. The model complex 40, i.e. without any phenyl rings, and fully
optimized at BP86-D/def2-TZVP, leads to a similar conclusion (ESI,†
Fig. S6). Despite their non-aromatic character, these new synthons
can form non-covalent interactions in a similar fashion to truly
aromatic rings. Support for this is found in the analysis of the
molecular orbitals (MO) of both 4 and 40. As seen in ESI,† Fig. S7,
three MOs present an alignment between the p orbitals of N, C, Cl
and S, and the d orbital of Cu, forming a quasi-p-system. Further-
more, estimation of the interaction energy of C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS)
was made using the optimal geometries (BP86-D/def2-TZVP) for a
model system, C2H2ꢀꢀꢀ40, removing the basis set superposition error
(BSSE) by counterpoise (CP) correction.16c Referring to the ESI,†
Fig. S8, single point calculations were performed at r(HꢀꢀꢀO) distances
between 2.2 and 3.0 Å, for three positions in the ring, presenting an
average energy at the optimal separation of 3.5 kcal molꢁ1 at MP2 and
M062X-D, and 4 to 5 kcal molꢁ1 at B3LYP-D and B3PW91-D. For all
calculated positions, the interactions are attractive.
11 (a) F. H. Allen, Acta Crystallogr., Sect. B, 2002, 58, 380; (b) I. J. Bruno,
J. C. Cole, P. R. Edgington, M. Kessler, C. F. Macrae, P. McCabe,
J. Pearson and R. Taylor, Acta Crystallogr., Sect. B, 2002, 58, 389.
12 (a) J. T. Lenthall, K. M. Anderson, S. J. Smith and J. W. Steed, Cryst.
˜
Growth Des., 2007, 7, 1858; (b) T. S. Lobana, R. Sharma, A. Castinieras
and R. J. Butcher, Z. Anorg. Allg. Chem., 2010, 636, 2698; (c) D. Li, W.-
J. Shi, T. Wu and S. W. Ng, Acta Crystallogr., Sect. E, 2004, 60, m776;
˜
(d) T. S. Lobana, P. Kaur, A. Castineiras, P. Turner and T. W. Failes,
Struct. Chem., 2008, 19, 727; (e) N. J. M. Sanghamitra, M. K. Adwankar,
A. S. Juvekar, V. Khurajjam, C. Wycliff and A. G. Samuelson, Indian
J. Chem., Sect. A, 2011, 50, 465; ( f ) P. Aslanidis, P. J. Cox, S. Divanidis
and P. Karagiannidis, Inorg. Chim. Acta, 2004, 357, 4231;
(g) S. K. Hadjikakou, P. Aslanidis, P. Karagiannidis, D. Mentzafos
and A. Terzis, Polyhedron, 1991, 10, 935; (h) T. S. Lobana, P. K. Bhatia
and E. R. T. Tiekink, J. Chem. Soc., Dalton Trans., 1989, 749;
˜
(i) T. S. Lobana, R. Sharma, A. Castineiras, G. Hundal and
R. J. Butcher, Inorg. Chim. Acta, 2009, 362, 3547; ( j) T. S. Lobana,
˜
S. Khanna, G. Hundal, R. J. Butcher and A. Castineiras, Polyhedron,
2009, 28, 3899; (k) N. Gunasekaran, P. Ramesh, M. N. G. Ponnuswamy
and R. Karvembu, Dalton Trans., 2011, 40, 12519; (l) T. S. Lobana,
R. Sultana and G. Hundal, Polyhedron, 2008, 27, 1008; (m) M. K. Rauf,
Imtiaz-ud-Din, A. Badshah, M. Gielen, M. Ebihara, D. de Vos and
S. Ahmed, J. Inorg. Biochem., 2009, 103, 1135; (n) P. Karagiannidis,
S. K. Hadjikakou, P. Aslanidis and A. Hountas, Inorg. Chim. Acta,
1990, 178, 27; (o) R. Singh and S. K. Dikshit, Polyhedron, 1995,
14, 1799.
In summary, experimental and theoretical evidence has been
presented for attractive (ca. 3.5 kcal molꢁ1) intramolecular
C–Hꢀꢀꢀp(CuClꢀꢀꢀHNCS) interactions which occur in approximately
15% of the copper(I) structures where they may potentially form.
The Brazilian authors thank FAPESP (2013/02311-3 to
M.A.B.F.), CNPq (305626/2013-2 to J.Z.-S. and 477944/2013-2
to M.A.B.F.) and CAPES (808/2009-3 to J.Z.-S.) for financial
support. Calculations were performed at CENAPAD-SP. This
research is also supported by High Impact Research MoE
Grant UM.C/625/1/HIR/MoE/SC/12 from the Ministry of Higher
Education Malaysia.
13 (a) J. D. Dunitz and R. Taylor, Chem. – Eur. J., 1997, 3, 89;
(b) J. Zukerman-Schpector and E. R. T. Tiekink, CrystEngComm,
2009, 11, 2701.
14 (a) A. D. Becke, Phys. Rev. A, 1988, 38, 3098; (b) J. P. Perdew, Phys. Rev.
B, 1986, 33, 8822; (c) S. Grimme, J. Antony, S. Ehrlich and H. Krieg,
J. Chem. Phys., 2010, 132, 154104; (d) M. Head-Gordon, J. A. Pople and
M. J. Frisch, Chem. Phys. Lett., 1988, 153, 503; (e) D. Feller, J. Comput.
Chem., 1996, 17, 1571; ( f ) K. L. Schuchardt, B. T. Didier, T. Elsethagen,
L. Sun, V. Gurumoorthi, J. Chase, J. Li and T. L. Windus, J. Chem. Inf.
Model., 2007, 47, 1045.
´
15 (a) E. R. Johnson, S. Keinan, P. Mori-Sanchez, J. Contreras-Garcia,
Notes and references
A. J. Cohen and W. Yang, J. Am. Chem. Soc., 2010, 132, 6498;
´
1 A. Priimagi, G. Cavallo, P. Metrangolo and G. Resnati, Acc. Chem.
Res., 2013, 46, 2686.
2 The Importance of Pi-Interactions in Crystal Engineering: Frontiers in
(b) J. Contreras-Garcıa, E. R. Johnson, S. Keinan, R. Chaudret,
J.-P. Piquemal, D. N. Beratan and W. Yang, J. Chem. Theory Comput.,
2011, 7, 625.
Crystal Engineering, ed. E. R. T. Tiekink and J. Zukerman-Schpector, 16 (a) P. R. Schleyer, C. Maerker, A. Dransfeld, H. Jiao and N. J. R. E.
ˇ ´
Hommes, J. Am. Chem. Soc., 1996, 118, 6317; (b) M. K. Milcic,
John Wiley and Sons, Singapore, 2012.
3 H. Masui, Coord. Chem. Rev., 2001, 219–221, 957; F. Feixas,
´
´
B. D. Ostojic and S. D. Zaric, Inorg. Chem., 2007, 46, 7109;
(c) S. F. Boys and F. Bernardi, Mol. Phys., 1971, 19, 553.
`
E. Matito, J. Poater and M. Sola, Wiley Interdiscip. Rev., 2013, 3, 105.
5986 | Chem. Commun., 2014, 50, 5984--5986
This journal is ©The Royal Society of Chemistry 2014