Organometallics 1995,14, 121-130
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Molecular Structure, Dynamics, and Crystal [BF4] (Arene = Organization of [@-C1)3{(q6-arene)Ru}21 C a s and C6Hme) and a Bonding Study by Extended Hiickel Calculations Fabrizia Grepioni* and Dario Braga Dipartimento di Chimica G. Ciamician, Universita di Bologna, Via Selmi 2, 40126 Bologna, Italy
Paul J. Dyson, Brian F. G. Johnson,*and Fiona M. Sanderson Department of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K.
Maria Jose Calhorda* and Luis F. Veiros Centro de Tecnologia Quimica e Biolbgica, R. da Quinta Grande 6, 2780 Oeiras, Portugal, and Instituto Superior Thcnico, Lisboa, Portugal Received June 8, 1994@ The complexes [Cu-C1)3{(y6-arene)Ru}21+(arene = C&t6, 1, and CsHsMe, 2) have been synthesized by reaction of the appropriate dihydroarene and ruthenium(II1) chloride in ethanol, yielding {(~-C1)2[(q~-arene)RuC1]2}, which then affords the desired product on treatment with aqueous HBFl in trifluoroacetic acid. Single crystal X-ray diffraction data have been collected at 296 and 150 K for 1 (la,and lb, respectively) and at 150 K for 2. Com ound la is monoclinic, space group P21/a, a = 8.4449(6), b = 18.9448(12),c = 10.3154(7)if,/3 = 103.416(4)", V = 1605.3 Hi3, 2 = 4; l b is monoclinic, space group P21/a, a = 8.43(2), b = 18.68(14),c = 10.25(2) p = 104.8(1)", V = 1560.5 Hi3, 2 = 1; 2 is triclinic, space group P i , a = 9.355(5), b = 9.668(4), c = 10.190(4) a = 92.12(3), p = 104.71(4), y = 93.07(3)", V = 888.9 A3, 2 = 2. The hydrogen atoms in 1, as well as the methyl groups in 2, have been found to bend significantly towards the metal atoms. The bonding interactions between the arene fragments and the metals have been studied by means of extended Huckel calculations showing that a 6" bending is required in order to optimize the overlap between the @-C1)3Ru2fragment and the arenes. The molecular structures of both complexes have been investigated in relation with the respective crystal structures. The ion organization in crystalline 1 and 2 has been compared with that in analogous bis(arene) derivatives. The dynamics about equilibrium positions as well as the reorientational motion of the benzene ligands in 1 at the two temperatures have been investigated by means of thermal motion analysis and packing potential energy calculations.
A,
A,
Introduction Chloro-bridged arene diruthenium complexes date back many years. The primary complex, [(areneb RuC1212, from which all subsequent products are derived, was first reported in 1967 for benzene. The complex was obtained from the reaction between cyclohexa-1,3-dieneand ruthenium(II1)chloride in ethano1.l It was later found that virtually any dihydroarene would react under similar conditions to afford the appropriate arene derivatives.2 It is from these species that the complexes described herein, namely [@-C1)3{($-areneb Ru)# (arene = benzene, 1,and toluene, 2) are produced by merely heating with aqueous tetrafluoroboric acid in trifluoroacetic acid. Both types of complexes described above have been the subject of extensive reactivity studies, usually concerning halide ion substitution.
Many of these reactions have been well documented quite recently.3 In this paper, beside reporting the synthesis and spectroscopic characterization of the two title complexes, we investigate in detail the structures of the two cationic complexes in the solid state as well as the structure of the respective crystals. Attention is focused on the relationship between molecular and crystal structures and on the intermolecular organization of the component ions in the crystalline material. The structural features observed in the solid.state are examined in the light of the results of extended Huckel calculations whereas the crystal structures are investigated in terms of intermolecular interactions and anion-cation organization. A similar approach has been used to study the relationship between face-cappingand terminal bonding modes of benzene in neutral ruthenium cluster^.^
Abstract published in Advance ACS Abstracts, November 1, 1994. (1) Winkhans, G.; Singer, H. J. Organomet. Chem. 1967, 7, 487. (2) Bennet, M. A,; Smith, A. K. J.Chem. Soc., Dalton Trans. 1974, 233. @
0276-733319512314-0121$09.00/0 0 1995 American Chemical Society
Grepioni et al.
122 Organometallics, Vol. 14, No. 1, 1995 Table 1. Selected Bond Lengths (A) and Angles (deg) for 1 la
lb
Ru( 1)-C1( 1) Ru( 1)-C1(2) Ru( 1)-C1(3) Ru(2)-Cl( 1) Ru(2)-C1(2) Ru(2)-C1(3) Ru( 1)-C( 1) Ru( 1)-C(2) Ru(l)-C(3) Ru(1)-C(4) Ru( 1)-C(5) Ru(l)-C(6) Ru(2)-C(7) Ru(2)-C(8) Ru(2)-C(9) Ru(2)-C( 10) Ru(2)-C(ll) Ru(2)-C(12) C(l)-C(2) C(1)-C(6) C(2)-C(3) C(3)-C(4) C(4)-C(5) C(5)-C(6) C(7)-C(8) C(7)-C( 12) C(8)-C(9) C(9)-C(10) C(lO)-C(ll) C(ll)-C(12) B-F(l) B-F(2) B-F(3) B-F(4)
2.45 l(2) 2.422(2) 2.425(2) 2.455(2) 2.423(1) 2.415(2) 2.173(6) 2.169(6) 2.167(6) 2.156(6) 2.165(6) 2.171(6) 2.140(6) 2.172(6) 2.166(6) 2.158(7) 2.164(6) 2.151(7) 1.41(1) 1.42(1) 1.40(1) 1.41(1) 1.40(1) 1.39(1) 1.39(1) 1.38(1) 1.41(1) 1.42(2) 1.38(1) 1.41(1) 1.38(2) 1.37(2) 1.39(2) 1.38(2)
2.454( 1) 2.425( 1) 2.434( 1) 2.458(1) 2.428(1) 2.421(1) 2.167(5) 2.171(5) 2.168(5) 2.167(5) 2.171(5) 2.163(5) 2.155(5) 2.163(5) 2.178(5) 2.178(5) 2.177(5) 2.161(5) 1.392(7) 1.43l(7) 1.415(8) 1.418(8) 1.419(8) 1.402(8) 1.418(8) 1.404(7) 1.394(8) 1.424(10) 1.409(8) 1.427(8) 1.383(8) 1.390(7) 1.410(7) 1.375(7)
Ru( l)-Cl( l)-Ru(2) Ru( 1)-C1(2)-Ru(2) Ru(2)-C1(3)-Ru( 1)
84.10(5) 85.39(5) 85.49(5)
84.0l(4) 85.27(4) 85.22(4)
Anion-cation interaction^,^ hydrogen bonding,6 and van der Waals interactions have been studied in detail.7 These aspects are related to our studies of the factors controlling the crystal engineering of organometallic materiak8 Another aspect of relevance is concerned with the dynamic behavior about equilibrium positions and far from equilibrium of the atoms or atomic groupings in the solid state. Investigatory “tools” such as thermal motion analysis and atom-atom potential energy barrier calculations have been used to estimate the extent of such dynamicsg Results and Discussion Molecular Structure of 1 and 2 in the Solid State. The molecular structures of 1 and 2 have been determined by single-crystal X-ray diffraction measurements at 296 and 150 K for 1 ( l a and lb, respectively) and at 150 K for 2. The two molecules are closely related and will be discussed together. Relevant structural parameters are reported in Tables 1 and 2 for 1 ~
(5) (a)Braga, D.; Grepioni, F.; Milne, P.; Parisini, E. J . Am. Chem. SOC.1993,115,5115. (b) Braga, D.;Grepioni, F. Organometallics 1992, 11, 1256. (6) (a) Braga, D.;Grepioni, F.; Sabatino, P.; Desiraju, G. R. Organometallics 1994,13, 3532. (b) Biradha, K.;Peddireddi, V. R.; Braga, D.; Grepioni, F.; Desiraju, G. R. Submitted for publication. (7) (a)Braga, D.; Grepioni, F. Organometallics 1991,10,1255.(b) Braga, D.; Grepioni, F.; Sabatino, P. J . Chem. SOC.Dalton Trans. 1990, 3137.(c) Braga, D.; Grepioni, F.; Sabatino, P.; Gavezzotti, A. J.Chem. SOC.Dalton Trans. 1992, 1185. (d) Braga, D.; Grepioni, F. Acta Crystallogr. Sect. B 1989, B45, 378. (e) Braga, D.; Grepioni, F. Organometallics 1991,10,2563. (8) Braga, D.;Grepioni F. Acc. Chem. Res. 1994,27,51. (9) Braga, D. Chem. Rev. 1992,92,633.
b b
n
Figure 1. Structures of 1 (a) and 2 (b) in the solid state showing the atomic labeling schemes. Table 2. Selected Bond Lengths (A) and Angles (deg) for 2 Ru(1)-Cl( 1) Ru( 1)-C1(2) Ru( 1)-C1(3) Ru(2)-C1(1) Ru(2)-C1(2) Ru(2)-C1(3) Ru( 1)-C( 1) Ru( 1)-C(2) Ru( 1)-C(3) Ru( 1)-C(4) Ru(l)-C(5) Ru(l)-C(6) Ru(2)-C(8) Ru(2)-C(9) Ru(2)-C( 10) Ru(2)-C(11) Ru(2)-C( 12) Ru(2)-C( 13) Ru( 1)-Cl( 1)-Ru(2) Ru( l)-C1(2)-Ru(2)
2.438(1) 2.419(1) 2.434(1) 2.438(1) 2.420(1) 2.441(1) 2.188(3) 2.167(3) 2.157(3) 2.175(3) 2.154(3) 2.161(3) 2.190(3) 2.163(3) 2.156(3) 2.175(3) 2.160(3) 2.170(3) 84.38(2) 85.19(3)
1.426(5) 1.401(5) 1.403(5) 1.418(6) 1.394(5) 1.421(5) 1.493(5) 1.418(5) 1.415(5) 1.413(5) 1.416(5) 1.411(6) 1.415(6) 1.488(5) 1.378(5) 1.386(5) 1.385(5) 1.385(5) 84.42(3)
and 2, respectively. Sketches of the two molecules are shown in Figure la,b for 1 and 2, respectively. The relevant structural features of the two complexes can be summarized as follows: (i)Both complexes are constituted of two Ru(I1) atoms joined by three bridging chlorine ligands, each Ru-atom also carries an q6-coordinatedarene ligand (benzene in 1, toluene in 2). (ii) The Rw .Ru separation is slightly shorter in the toluene complex than in the benzene derivative L3.275(1)in 2 us. 3.285(1) at 296 and 3.287(1) A at 150 K in 11. (iii) The Ru-atoms are almost equidistant from the plane formed by the bridging C1-atoms;Ru-C1 distances range between 2.415(2) and 2.455(2) A in la, between 2.421(1)and 2.458(1)A in lb, and between 2.419(1) and 2.441(1)A in 2. The Ru-C1-Ru angles vary accordingly [84.10(5)-85.49(5)O in la; 84.01(4)-85.27(4) in lb; 84.38(2)-85.19(3)0 in 21.
Organometallics, Vol. 14, No. 1, 1995 123 a
Table 3. Results of Rigid-Body-Motion Analysis for la, lb, and 2 la (296 K) l b (150 K) 2 (150 K)
c
P
Figure 2. Different conformations of the arene rings in 1 (a) and 2 (b) with respect to the chlorine bridges. In 1 the two benzene rings are almost exactly eclipsed but staggered with respect to the C1-atoms. In 2, the ring carbons and the C1-atoms are eclipsed,while the methyl groups are 120" apart in projection and adopt a pseudo 1,3-arrangement overlapping two C1-atoms.
(iv) Ru-C distances are fairly constant and comparable in the two complexes [ranges: 2.14(1)-2.17(1) la; 2.155(5)-2.178(5) lb; 2.154(3)-2.190(3) A in 21; the longest distances in 2 are associated with the ring atoms carrying the methyl groups [Ru(l)-C(l) 2.188(3), Ru(2)-C(8) 2.190(3) AI. (v) The arene rings in 1 and 2 have different conformations with respect to the chlorine bridges. In 1 the two benzene rings are almost exactly eclipsed, but are staggered with respect to the C1-atoms (see Figure 2a). In 2, on the other hand, the ring carbons and the C1atoms are eclipsed, while the methyl groups are 120" apart in projection and adopt apseudo 1,3-arrangement overlapping (see Figure 2b) two C1-atoms. "he conformational aspect of these molecules will be discussed in more detail in the crystal structure section. (vi) Although only a neutron diffraction study can afford an unequivocal location of H-atoms, an interesting feature shared by 1 and 2 is revealed by the X-ray diffraction data. Both the C-H and the C-Me bonds bend towards the metal atoms from the planes defined by the c6 rings. The high quality of the diffraction data allowed direct location of all the H-atoms including those of the methyl groups. The H-atom location is more precise in the 150 K data sets. The average deviation of the H-atoms from the mean least-square plane of the rings towards the metal atom is 0.07, and 0.04 A in la; 0.08,0.09 A in lb; C(7) 0.09, H-atoms 0.10; C(14) 0.09; H-atoms 0.9 A in 2. The mean Ru-C(arene) are in la, Ru(1)-C 2.17(1), Ru(2)-C 2.16(1) A; in lb, Ru(1)-C 2.168(5), Ru(2)-C 2.169(5)A; and in 2,2.167(3), Ru(2)-C 2.169(3) A.
Model 1 (Whole Molecule) 60.4 21.1 7.3 3.3 4.7 2.2
29.1 3.0 2.1
Model 2.1 (Ru and First Ring C Atoms) 52.1 21.3 6.1 2.8 4.5 1.3
20.6 3.5 2.4
Model 2.2 (Ru and Second Ring C Atoms) 77.5 36.0 7.4 2.6 5.5 1.o
31.4 3.7 3.0
Model 2.3 (Ru and C1 Atoms) 61.7 21.4 7.8 3.9 5.4 2.5
30.8 3.6 2.9
(vii) The ring planes are nearly parallel in 2, whereas they form an angle of 3.9" in l a which increases to 4.3" on passing from room temperature to 150 K. (viii) A slight, but significant C-C bond length alternation is observed in complex 1 (see Table 11, the "short" bonds being those trans to the C1-bridges, whereas in 2 there is no systematic alternation nor there is any symmetry pattern conforming to the mirror symmetry of the toluene ligands. The molecular structures of 1 and 2 are related to that of the bis(cymene) complex [OL-C~)B{(~-CH~.C~H*.CH( C H ~ ) ~ ) R U ] ~ I [ Bwhich P ~ ~ Ialso , contains three C1-bridges and two y6-arenefragments bound to the Ru(I1)atoms,1° and to the neutral complex OL-Cl)2{RuCl(y6-C6Mes))z which presents only two C1-atoms in bridging position while the other two are terminally bound.ll Thermal Motion Analysis. The dynamic behavior of the arene rings about equilibrium positions will now be discussed. The available anisotropic displacement parameters (the anisotropic Us) were used to carry out a rigid-body motion analysis based on the libration (L), translation (T) and correlation, or roto-translation (S) tensors (TLS approach12 In order to evaluate the mean-square amplitudes for the arenes motion around equilibrium, thermal motion analysis was performed with the program THMA1112cand the results are summarized in Table 3. A rigid body motion was first assumed to describe the motion about equilibrium of the whole molecules la, lb and 2 (model 1 in Table 3). In all cases the overall librational motion is strongly anisotropic, the value of the L1 component being one order of magnitude larger than those of La and L3. In the case of molecule 1 the librational motion decreases appreciably with temperature on passing from 60.4 to 21.1 deg2. The maximum libration axis L1 is almost coincident with the molecular axis, i.e. the axis passing through the two ruthenium atoms. The translational motion, on the contrary, is fairly isotropic, therefore the eigenvalues of the three (10) Tocher, D. A.; Walkinshaw, M. D. Acta Crystallogr., Sect. B
1982,B38,3083 (11) McCormick, F. B.; Cleason, W. N. Acta Crystallogr., Sect. C 1988,C44,603. (12) (a) Dunitz, J. D.; Schomaker, V.; Trueblood, K. N. J. Phys. Chem. 1988,92,856.(b)Dunitz, J. D.; Maverick, E. F.; Trueblood, K. N. Angew. Chem. Int. Ed. Engl. 1988,27,880. (c) Trueblood, K. N. THMA11. Thermal Motion Analysis. University of California, Los
Angeles, CA, 1987.
124 Organometallics, Vol. 14, No. 1, 1995
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Grepioni et al.
m a
Figure 3. Comparison of the ADP of the two independent benzene rings in 1 at 296 and 150 K. translational components are not reported in Table 3. Because of the delocalized nature of the arene-metal bonding interactions, however, the motion of these molecules as rigid bodies represents an obvious appro~imation.~ A more realistic model for the dynamics about equilibrium positions can be attained if the arene fragments are allowed independent motion. Three alternative models were then tested to analyze the motion of the three separate fragments formed by the two Ru atoms and the first arene (model 2.11, the second arene (model 2.21, and the three C1 atoms (model 2.3). As in the case of model 1, attention is focused on the extent of librational motion about the three librational axes. The results are summarized in Table 3. It can be appreciated that, while model 1 describes fairly accurately the motion around equilibrium of the fragment Ru2C13 in all molecules (compare with model 2.31, the librational motion of the benzene and toluene rings around the Ru-Ru axis is better described if the two rings are treated separately (model 2.1 and 2.2) in each molecule. In summary, the results collected in Table 3 show that in both 1 and 2 the first arene ligand moves more than the second, while when model 1is used this difference is “averaged in the librational motion of the whole molecule. Potential energy barrier calculations (see section below) also indicate that the two rings differ in their reorientational motion. The anisotropic displacement parameters (ADP)of the two independent benzene rings in 1 and their variation with temperature are shown in Figure 3. The reduction of the ADP on passing from 296 K to 150 K is indicative of a true librational motion, and excludes the presence of some kind of static disorder. Similar behavior has been observed in many other instances. It is worth recalling here, as an example, the variable temperature structural analysis of the benzene complexes (C6H6)c r ( c 0 ) a~and ~ ~of ( C ~ H G ) M O ( C O ) ~ . ~ ~ ~ Discussion of the Crystal Structures of 1 and 2 and Related Materials. The organization of anions and cations in the crystal structure is now described. Emphasis will be given to the patterns of intermolecular interactions observed in crystalline 1 and 2 and on the relationship between these crystal structures and those of related complexes. (13) (a)Wang,Y.;Angermund,K.;Goddard,R.;&-tiger,C.J.Am. Chem. Soc. 1987, 109, 587. (b) Biirgi, H.-B.;Raselli,A.;Braga, D.; Grepioni,F.Acta Cystallogr., Sect. B 1992, B48, 428. (14) fa)Desiraju,G.R.Acc. Chem. Res. 1991,24, 290.
Figure 4. Intermolecular C1-H-C broken lines) in crystalline 2.
interactions (filled
Table 4. Intermolecular Contacts in la, l b and 2a intermolecular Cl.**H (A) C-Ha C1 contact (
