- Email: [email protected]
The first X-ray crystal structures of cobalt complexes containing monodentate and bridging ethylenediamine ligands
Inorganica Chimica Acta 288 (1999) 53 – 56
The first X-ray crystal structures of cobalt complexes containing monodentate and bridging ethylenediamine ligands Donald A. House 1, Peter J. Steel * Chemistry Department, Uni6ersity of Canterbury, Pri6ate Bag 4800, Christchurch, New Zealand Received 5 September 1998; accepted 4 December 1998
Abstract The X-ray crystal structures of cis-[CoCl(en)2(enH)]Cl(ZnCl4) (1) and rac-m-en[cis-CoCl(en)2]2(ZnCl4)2 (2) are reported. Complex 1 crystallises in the monoclinic space group P21/n with Z = 4, while 2 is in the chiral orthorhombic space group P212121 with Z= 4. These represent the first X-ray crystal structures of cobalt complexes containing either a monodentate or bridging ethylenediamine ligand. The conformations of the en ligands are also discussed. © 1999 Elsevier Science S.A. All rights reserved. Keywords: Crystal structures; Cobalt complexes; Ethylenediamine complexes
1. Introduction Modern coordination chemistry was founded on the pioneering work of Alfred Werner. In the course of formulating his landmark theories on the stereochemistry of transition metal complexes, Werner made extensive use of cobalt complexes of the chelating ligand ethylenediamine (en) [1]. Since that time, cobalt complexes of en have been extensively studied in various contexts [2]. Indeed, a search of the Cambridge Structural Database located over 400 entries for cobalt complexes containing chelating en ligands. However, to our surprise, no entries were found for cobalt complexes with either monodentate or bridging en ligands, despite the fact that both of these modes of coordination to cobalt have been known for some time [3,4]. In fact, cobalt complexes containing monodentate en ligands have been the subject of several physicochemical studies [5]. We now report the first X-ray crystal structures of cobalt complexes containing monodentate and bridging en ligands, in the form of cis-[CoCl(en)2(enH)]Cl(ZnCl4) (1), with a monodentate en, and rac-m-en[cisCoCl(en)2]2(ZnCl4)2 (2), with a bridging en. * Corresponding author. Tel.: +64-3-364 2432; fax: +64-3-364 2110. E-mail address: [email protected] (P.J. Steel) 1 Also corresponding author.
2. Experimental
2.1. Preparations of complexes The complexes were prepared according to the procedures of Alexander and co-workers [3,4], except that they were isolated and recrystallised as tetrachlorozincate salts. These complexes can also be isolated as minor by-products (B3%) from the conventional synthesis of trans-[CoCl2(en)2] + using H2O2 as the oxidant [6].
2.2. X-ray crystallography The crystal data, data collection and refinement parameters for the two structures are listed in Table 1. Data were collected with a Siemens SMART CCD area detector, using graphite monochromatized Mo Ka radi-
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved. PII: S 0 0 2 0 - 1 6 9 3 ( 9 9 ) 0 0 0 3 3 - X
D.A. House, P.J. Steel / Inorganica Chimica Acta 288 (1999) 53–56
54
Table 1 Crystal data, data collection and refinement parameters
Formula M Crystal system ˚) a (A ˚) b (A ˚) c (A b (°) ˚ 3) V (A Space group Z F(000) Dcalc. (g cm−3) Crystal form Dimensions (mm) m (mm−1) Temperature (K) 2umax (°) No. reflections measured Unique reflections No. with I\2s(I) Weighting a/b Parameters wR (all data) R1 [I\2s(I)]
1
2
C6H25Cl6CoN6Zn 518.32 monoclinic 13.3388(13) 11.4463(11) 13.8456(18) 118.694(1) 1854.3(4) P21/n 4 1048 1.857 red block 0.57×0.44×0.23 3.050 158 53 21246 3704 3304 0.0424/1.6687 182 0.0698 0.0239
C10H40Cl10Co2N10Zn2 903.62 orthorhombic 9.9080(2) 13.1080(3) 24.1372(5) 90 3134.8(1) P212121 4 1816 1.915 red prism 0.36×0.31×0.18 3.427 162 52 10843 5528 5410 0.0489/0 307 0.0964 0.0398
˚ ). The structures were solved by ation (l = 0.71073 A direct methods using SHELXS [7], and refined on F 2 using all data by full-matrix least-squares procedures with SHELXTL Version 5.10 [8]. Hydrogen atoms were included in calculated positions with isotropic displacement parameters 1.2 times the isotropic equivalent of their carrier atoms and the torsional orientation of the NH3 hydrogens in 1, deduced from circular Fourier syntheses. The functions minimised were Sw(F o2 − F c2)2,
Fig. 1. Perspective view and atom labelling of the crystal structure of L-cis-[CoCl(en)2(enH)]Cl(ZnCl4) (1).
Table 2 ˚ ) and angles (°) for 1 Selected bond lengths (A ˚) Bond lengths (A Co(1)–N(1) Co(1)–N(3) Co(1)–N(5) N(5)–C(5) C(6)–N(6)
1.968(2) 1.967(2) 1.979(2) 1.482(3) 1.479(3)
Co(1)–N(2) Co(1)–N(4) Co(1)–Cl(1) C(5)–C(6)
1.978(2) 1.970(2) 2.2632(6) 1.533(3)
Bond angles ( °) N(1)–Co(1)–N(3) N(4)–Co(1)–N(1) N(1)–Co(1)–N(2) N(3)–Co(1)–N(5) N(4)–Co(1)–N(5) N(3)–Co(1)–Cl(1) N(4)–Co(1)–Cl(1) N(5)–Co(1)–Cl(1) N(5)–C(5)–C(6)
175.19(8) 93.64(8) 84.71(8) 89.52(8) 89.69(8) 91.47(6) 176.59(6) 88.80(6) 109.83(18)
N(3)–Co(1)–N(4) N(2)–Co(1)–N(3) N(2)–Co(1)–N(4) N(1)–Co(1)–N(5) N(2)–Co(1)–N(5) N(1)–Co(1)–Cl(1) N(2)–Co(1)–Cl(1) C(5)–N(5)–Co(1) N(6)–C(6)–C(5)
85.46(8) 90.58(8) 90.90(8) 95.20(8) 179.41(8) 89.54(6) 90.61(6) 120.22(14) 111.22(19)
with w= [s 2(F o2)+ (aP)2 + bP] − 1, [max(Fo)2 + 2F c2]/3.
where
P=
3. Results and discussion The complex cis-[CoCl(en)2(enH)]Cl(ZnCl4) (1) crystallises in the centrosymmetric monoclinic space group P21/n, the asymmetric unit of which contains a cis-CoCl(en)2(enH) cation, with a tetrahedral tetrachlorozincate and chloride counterions. Fig. 1 shows a perspective view of the cation with the L configuration and atom labelling of the structure. Table 2 lists selected interatomic distances and angles. The structure determination confirms the existence of the monodentate (hypodentate) 2-aminoethylammonium coordination to cobalt. The geometry at cobalt is octahedral (Table 2), the largest deviations from ideal geometry being associated with the normal bite angles of the five-membered chelate rings, which adopt the dl conformation with torsion angles of 9 49.8(3)°. All five Co–N bonds are approximately equal in length. The monodentate enH ligand exists in an anti conformation about the C–C bond [N5–C5–C6–N6= 176.5(2)°] and coordinates to the metal with an anti conformation about the C–N bond [Co1–N5–C6– C6=172.3(2)°], as previously observed in the isostructural complex cis-[CrCl(en)2(enH)]Cl(HgCl4) [9]. This anti–anti arrangement is commonly [10], but not exclusively [11], observed in monodentate complexes of en with other metals. Furthermore, the solid state conformation excludes the possibility of the free –NH3+ group being involved in an intramolecular hydrogen bond, as has previously been proposed [5]. There are no unusually short intermolecular interactions. The complex rac-m-en[cis-CoCl(en)2]2(ZnCl4)2 (2) crystallises in the chiral orthorhombic space group
D.A. House, P.J. Steel / Inorganica Chimica Acta 288 (1999) 53–56
Fig. 2. Perspective view and atom labelling of the crystal structure of L,L-m-en[cis-CoCl(en)2]2(ZnCl4)2 (2).
P212121 with a full binuclear cation and two tetrachlorozincate anions in the asymmetric unit. Fig. 2 shows a perspective view and atom labelling of the structure. Table 3 lists selected interatomic distances and angles. The structure determination confirms the presence of the en bridge and reveals that the diastereoisomer isolated from the reaction is the racemic, rather than the meso, isomer. Furthermore, this undergoes spontaneous resolution on crystallisation (conglomerate formation [12]), the crystal selected havTable 3 ˚ ), angles (°) and torsion angles (°) for 2 Selected bond lengths (A ˚) Bond lengths (A Co(1)–N(1) Co(1)–N(3) Co(1)–N(5)a N(5)–C(5) C(6)–N(6) Co(2)–N(8) Co(2)–N(7) Co(2)–Cl(2)
1.965(4) 1.951(4) 2.006(5) 1.460(7) 1.474(6) 1.958(4) 1.960(4) 2.239(1)
Co(1)–N(2) Co(1)–N(4) Co(1)–Cl(1) C(5)–C(6) Co(2)–N(6)a Co(2)–N(9) Co(2)–N(10)
1.960(4) 1.947(4) 2.229(1) 1.507(8) 1.998(4) 1.959(4) 1.970(4)
Bond angles (°) N(4)–Co(1)–N(3) N(3)–Co(1)–N(2) N(3)–Co(1)–N(1) N(4)–Co(1)–N(5) N(2)–Co(1)–N(5) N(4)–Co(1)–Cl(1) N(2)–Co(1)–Cl(1) N(5)–Co(1)–Cl(1) N(5)–C(5)–C(6) C(6)–N(6)–Co(2) N(8)–Co(2)–N(7) N(8)–Co(2)–N(10) N(7)–Co(2)–N(10) N(9)–Co(2)–N(6) N(10)–Co(2)–N(6) N(9)–Co(2)–Cl(2) N(10)–Co(2)–Cl(2)
85.2(2) 89.5(2) 174.0(2) 88.2(2) 179.5(2) 176.3(1) 89.2(1) 90.5(1) 114.2(5) 119.5(3) 84.9(2) 92.3(2) 90.6(2) 91.4(2) 176.9(2) 94.1(2) 86.9(1)
N(4)–Co(1)–N(2) N(4)–Co(1)–N(1) N(2)–Co(1)–N(1) N(3)–Co(1)–N(5) N(1)–Co(1)–N(5) N(3)–Co(1)–Cl(1) N(1)–Co(1)–Cl(1) C(5)–N(5)–Co(1) N(6)–C(6)–C(5) N(8)–Co(2)–N(9) N(9)–Co(2)–N(7) N(9)–Co(2)–N(10) N(8)–Co(2)–N(6) N(7)–Co(2)–N(6) N(8)–Co(2)–Cl(2) N(7)–Co(2)–Cl(2) N(6)–Co(2)–Cl(2)
92.2(2) 92.7(2) 85.0(2) 90.3(2) 95.3(2) 91.4(1) 90.9(1) 121.8(4) 117.0(5) 91.9(2) 174.9(2) 85.6(2) 88.5(2) 92.5(2) 173.9(1) 89.1(1) 92.6(1)
Torsional angles (°) N(1)–C(1)–C(2)–N(2) N(7)–C(7)–C(8)–N(8) a
51.2(5) N(3)–C(3)–C(4)–N(4) 52.0(5) N(9)–C(9)–C(10)–N(10)
N atom of bridging ligand.
48.8(5) 51.1(6)
55
ing the L,L absolute configuration. All five-membered chelate rings adopt the d conformation (see Table 3 for torsion angles). The geometry at each cobalt centre (Table 3) is similar to that in 1, although it is noteworthy that the two Co–N bond lengths to the bridging en ligand are somewhat longer than those to the chelating en ligands. A consequence of the bridging is that the N–C–C angles in the bridging en ligand are widened considerably (114.2(5), 117.0(5)°), when compared with the comparable angles (109.8(2), 111.2(2)°) in the monodentate case. It thus appears that the effect of bridging is to introduce some stretching in the ligand itself, as seen in both the Co–N distances and N–C–C angles. An interesting feature of the structure is that the bridging en ligand exists in a gauche conformation (N5–C5–C6–N6=69.3(7)°), rather than the more common [13] anti conformation. However, the conformations about the two C–N bonds are both anti (Co1– N5–C5–C6=172.6(4)°; Co2–N6–C6–C5= 162.4(4)°); such differences in internal torsional angles destroy any potential crystallographic 2-fold symmetry within the complex. This anti–gauche–anti arrangement has not been previously observed in any binuclear complexes of en, and leads to an intermetal separation (Co1–Co2) of ˚ . Indeed, the only previously reported exam7.080(1) A ple of a bridging en with a gauche arrangement about the central C–C bond is in the polymeric complex of en with silver(I) perchlorate, but this has a gauche– gauche–gauche arrangement and an intermetal separa˚ [14]. tion of only 3.377(1) A The Co–Cl distances in both 1 and 2 are normal for complexes containing the Co(III)Cl(N)5 chromophore, with the values found in 2 being on the short side of the frequency distribution obtained for 83 compounds of this type [15]. The Zn–Cl distances and Cl–Zn–Cl angles in the ZnCl42 − anions are similar to those previously reported [16].
4. Supplementary material Complete tables of atom coordinates, anisotropic displacement parameters, and bond distances and angles are available from the author P.J. Steel.
References [1] A. Werner, Chem. Ber. 44 (1911) 1887. [2] D.A. House, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty, Comprehensive Coordination Chemistry, vol. 2, Pergamon, Oxford, 1987, p. 23. [3] M.D. Alexander, C.A. Spillert, Inorg. Chem. 9 (1970) 2344. [4] M.D. Alexander, H.G. Kilcrease, J. Inorg. Nucl. Chem. 35 (1973) 1583.
56
D.A. House, P.J. Steel / Inorganica Chimica Acta 288 (1999) 53–56
[5] [6] [7] [8]
H. Ogino, Inorg. Chem. 19 (1980) 1619 and Refs. therein. D.A. House, Helv. Chim. Acta 68 (1985) 1872. G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467. G.M. Sheldrick, SHELXTL, Bruker Analytical X-ray Systems, 1997. [9] D.A. House, V. McKee, W.T. Robinson, Inorg. Chim. Acta 157 (1989) 15. [10] (a) F.P. Fanizzi, G. Natile, L. Maresca, A.M.M. Lanfredi, A. Tiripicchio, J. Chem. Soc., Dalton Trans. (1984) 1467. (b) M. Cavellec, D. Riou, G. Ferey, Eur. J. Solid State Inorg. Chem. 32 (1995) 271. (c) M.I. Khan, R.C. Haushalter, C.J. O’Connor, Cuihong Tao, J. Zubieta, Chem. Mater. 7 (1995) 2807. [11] (a) G. Natile, F.P. Fanizzi, L. Maresca, A.M.M. Lanfredi, A. Tiripicchio, J. Chem. Soc., Dalton Trans. (1985) 1057. (b) A. Arzoumanian, A. Bouraoui, V. Lazzeri, M. Rajzmann, H. Teruel, H. Krentzien, New J. Chem. 16 (1992) 965. (c) L.M.
.
[12]
[13]
[14] [15] [16]
Meyer, R.C. Haushalter, J. Zubieta, J. Solid State Chem. 125 (1996) 200. (a) I. Bernal, J. Chem. Educ. 69 (1992) 468. (b) I. Bernal, J. Cetrullo, F. Somoza, J.S. Rice, R. Lewis, S.S. Massoud, J. Coord. Chem. 38 (1996) 41, and Refs. therein. (a) T. Miyoshi, T. Iwamoto, Y. Sasaki, Inorg. Chim. Acta 6 (1972) 59, and Refs. therein. (b) S.-I. Nishikiori, T. Iwamoto, J. Incl. Phenom. 3 (1985) 283. (c) A. Rabenau, R. Kniep, W. Welzel, Z. Kristallogr. 183 (1988) 179. (d) S. Buchholz, K. Harms, M. Marsch, W. Massa, G. Boche, Angew. Chem., Int. Ed. Engl. 28 (1989) 72. (e) D. Matkovic-Calogovic, M. Sikirica, Z. Kristallogr. 190 (1990) 171. (f) S.H. Yuge, T. Iwamoto, J. Incl. Phenom. 14 (1992) 217. E. Bang, Acta Chem. Scand., Ser. A 32 (1978) 555. D.A. House, Comments Inorg. Chem. 19 (1997) 327. D.A. House, V. McKee, Polyhedron 12 (1993) 2335.
The first X-ray crystal structures of cobalt complexes containing monodentate and bridging ethylenediamine ligands Donald A. House 1, Peter J. Steel * Chemistry Department, Uni6ersity of Canterbury, Pri6ate Bag 4800, Christchurch, New Zealand Received 5 September 1998; accepted 4 December 1998
Abstract The X-ray crystal structures of cis-[CoCl(en)2(enH)]Cl(ZnCl4) (1) and rac-m-en[cis-CoCl(en)2]2(ZnCl4)2 (2) are reported. Complex 1 crystallises in the monoclinic space group P21/n with Z = 4, while 2 is in the chiral orthorhombic space group P212121 with Z= 4. These represent the first X-ray crystal structures of cobalt complexes containing either a monodentate or bridging ethylenediamine ligand. The conformations of the en ligands are also discussed. © 1999 Elsevier Science S.A. All rights reserved. Keywords: Crystal structures; Cobalt complexes; Ethylenediamine complexes
1. Introduction Modern coordination chemistry was founded on the pioneering work of Alfred Werner. In the course of formulating his landmark theories on the stereochemistry of transition metal complexes, Werner made extensive use of cobalt complexes of the chelating ligand ethylenediamine (en) [1]. Since that time, cobalt complexes of en have been extensively studied in various contexts [2]. Indeed, a search of the Cambridge Structural Database located over 400 entries for cobalt complexes containing chelating en ligands. However, to our surprise, no entries were found for cobalt complexes with either monodentate or bridging en ligands, despite the fact that both of these modes of coordination to cobalt have been known for some time [3,4]. In fact, cobalt complexes containing monodentate en ligands have been the subject of several physicochemical studies [5]. We now report the first X-ray crystal structures of cobalt complexes containing monodentate and bridging en ligands, in the form of cis-[CoCl(en)2(enH)]Cl(ZnCl4) (1), with a monodentate en, and rac-m-en[cisCoCl(en)2]2(ZnCl4)2 (2), with a bridging en. * Corresponding author. Tel.: +64-3-364 2432; fax: +64-3-364 2110. E-mail address: [email protected] (P.J. Steel) 1 Also corresponding author.
2. Experimental
2.1. Preparations of complexes The complexes were prepared according to the procedures of Alexander and co-workers [3,4], except that they were isolated and recrystallised as tetrachlorozincate salts. These complexes can also be isolated as minor by-products (B3%) from the conventional synthesis of trans-[CoCl2(en)2] + using H2O2 as the oxidant [6].
2.2. X-ray crystallography The crystal data, data collection and refinement parameters for the two structures are listed in Table 1. Data were collected with a Siemens SMART CCD area detector, using graphite monochromatized Mo Ka radi-
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved. PII: S 0 0 2 0 - 1 6 9 3 ( 9 9 ) 0 0 0 3 3 - X
D.A. House, P.J. Steel / Inorganica Chimica Acta 288 (1999) 53–56
54
Table 1 Crystal data, data collection and refinement parameters
Formula M Crystal system ˚) a (A ˚) b (A ˚) c (A b (°) ˚ 3) V (A Space group Z F(000) Dcalc. (g cm−3) Crystal form Dimensions (mm) m (mm−1) Temperature (K) 2umax (°) No. reflections measured Unique reflections No. with I\2s(I) Weighting a/b Parameters wR (all data) R1 [I\2s(I)]
1
2
C6H25Cl6CoN6Zn 518.32 monoclinic 13.3388(13) 11.4463(11) 13.8456(18) 118.694(1) 1854.3(4) P21/n 4 1048 1.857 red block 0.57×0.44×0.23 3.050 158 53 21246 3704 3304 0.0424/1.6687 182 0.0698 0.0239
C10H40Cl10Co2N10Zn2 903.62 orthorhombic 9.9080(2) 13.1080(3) 24.1372(5) 90 3134.8(1) P212121 4 1816 1.915 red prism 0.36×0.31×0.18 3.427 162 52 10843 5528 5410 0.0489/0 307 0.0964 0.0398
˚ ). The structures were solved by ation (l = 0.71073 A direct methods using SHELXS [7], and refined on F 2 using all data by full-matrix least-squares procedures with SHELXTL Version 5.10 [8]. Hydrogen atoms were included in calculated positions with isotropic displacement parameters 1.2 times the isotropic equivalent of their carrier atoms and the torsional orientation of the NH3 hydrogens in 1, deduced from circular Fourier syntheses. The functions minimised were Sw(F o2 − F c2)2,
Fig. 1. Perspective view and atom labelling of the crystal structure of L-cis-[CoCl(en)2(enH)]Cl(ZnCl4) (1).
Table 2 ˚ ) and angles (°) for 1 Selected bond lengths (A ˚) Bond lengths (A Co(1)–N(1) Co(1)–N(3) Co(1)–N(5) N(5)–C(5) C(6)–N(6)
1.968(2) 1.967(2) 1.979(2) 1.482(3) 1.479(3)
Co(1)–N(2) Co(1)–N(4) Co(1)–Cl(1) C(5)–C(6)
1.978(2) 1.970(2) 2.2632(6) 1.533(3)
Bond angles ( °) N(1)–Co(1)–N(3) N(4)–Co(1)–N(1) N(1)–Co(1)–N(2) N(3)–Co(1)–N(5) N(4)–Co(1)–N(5) N(3)–Co(1)–Cl(1) N(4)–Co(1)–Cl(1) N(5)–Co(1)–Cl(1) N(5)–C(5)–C(6)
175.19(8) 93.64(8) 84.71(8) 89.52(8) 89.69(8) 91.47(6) 176.59(6) 88.80(6) 109.83(18)
N(3)–Co(1)–N(4) N(2)–Co(1)–N(3) N(2)–Co(1)–N(4) N(1)–Co(1)–N(5) N(2)–Co(1)–N(5) N(1)–Co(1)–Cl(1) N(2)–Co(1)–Cl(1) C(5)–N(5)–Co(1) N(6)–C(6)–C(5)
85.46(8) 90.58(8) 90.90(8) 95.20(8) 179.41(8) 89.54(6) 90.61(6) 120.22(14) 111.22(19)
with w= [s 2(F o2)+ (aP)2 + bP] − 1, [max(Fo)2 + 2F c2]/3.
where
P=
3. Results and discussion The complex cis-[CoCl(en)2(enH)]Cl(ZnCl4) (1) crystallises in the centrosymmetric monoclinic space group P21/n, the asymmetric unit of which contains a cis-CoCl(en)2(enH) cation, with a tetrahedral tetrachlorozincate and chloride counterions. Fig. 1 shows a perspective view of the cation with the L configuration and atom labelling of the structure. Table 2 lists selected interatomic distances and angles. The structure determination confirms the existence of the monodentate (hypodentate) 2-aminoethylammonium coordination to cobalt. The geometry at cobalt is octahedral (Table 2), the largest deviations from ideal geometry being associated with the normal bite angles of the five-membered chelate rings, which adopt the dl conformation with torsion angles of 9 49.8(3)°. All five Co–N bonds are approximately equal in length. The monodentate enH ligand exists in an anti conformation about the C–C bond [N5–C5–C6–N6= 176.5(2)°] and coordinates to the metal with an anti conformation about the C–N bond [Co1–N5–C6– C6=172.3(2)°], as previously observed in the isostructural complex cis-[CrCl(en)2(enH)]Cl(HgCl4) [9]. This anti–anti arrangement is commonly [10], but not exclusively [11], observed in monodentate complexes of en with other metals. Furthermore, the solid state conformation excludes the possibility of the free –NH3+ group being involved in an intramolecular hydrogen bond, as has previously been proposed [5]. There are no unusually short intermolecular interactions. The complex rac-m-en[cis-CoCl(en)2]2(ZnCl4)2 (2) crystallises in the chiral orthorhombic space group
D.A. House, P.J. Steel / Inorganica Chimica Acta 288 (1999) 53–56
Fig. 2. Perspective view and atom labelling of the crystal structure of L,L-m-en[cis-CoCl(en)2]2(ZnCl4)2 (2).
P212121 with a full binuclear cation and two tetrachlorozincate anions in the asymmetric unit. Fig. 2 shows a perspective view and atom labelling of the structure. Table 3 lists selected interatomic distances and angles. The structure determination confirms the presence of the en bridge and reveals that the diastereoisomer isolated from the reaction is the racemic, rather than the meso, isomer. Furthermore, this undergoes spontaneous resolution on crystallisation (conglomerate formation [12]), the crystal selected havTable 3 ˚ ), angles (°) and torsion angles (°) for 2 Selected bond lengths (A ˚) Bond lengths (A Co(1)–N(1) Co(1)–N(3) Co(1)–N(5)a N(5)–C(5) C(6)–N(6) Co(2)–N(8) Co(2)–N(7) Co(2)–Cl(2)
1.965(4) 1.951(4) 2.006(5) 1.460(7) 1.474(6) 1.958(4) 1.960(4) 2.239(1)
Co(1)–N(2) Co(1)–N(4) Co(1)–Cl(1) C(5)–C(6) Co(2)–N(6)a Co(2)–N(9) Co(2)–N(10)
1.960(4) 1.947(4) 2.229(1) 1.507(8) 1.998(4) 1.959(4) 1.970(4)
Bond angles (°) N(4)–Co(1)–N(3) N(3)–Co(1)–N(2) N(3)–Co(1)–N(1) N(4)–Co(1)–N(5) N(2)–Co(1)–N(5) N(4)–Co(1)–Cl(1) N(2)–Co(1)–Cl(1) N(5)–Co(1)–Cl(1) N(5)–C(5)–C(6) C(6)–N(6)–Co(2) N(8)–Co(2)–N(7) N(8)–Co(2)–N(10) N(7)–Co(2)–N(10) N(9)–Co(2)–N(6) N(10)–Co(2)–N(6) N(9)–Co(2)–Cl(2) N(10)–Co(2)–Cl(2)
85.2(2) 89.5(2) 174.0(2) 88.2(2) 179.5(2) 176.3(1) 89.2(1) 90.5(1) 114.2(5) 119.5(3) 84.9(2) 92.3(2) 90.6(2) 91.4(2) 176.9(2) 94.1(2) 86.9(1)
N(4)–Co(1)–N(2) N(4)–Co(1)–N(1) N(2)–Co(1)–N(1) N(3)–Co(1)–N(5) N(1)–Co(1)–N(5) N(3)–Co(1)–Cl(1) N(1)–Co(1)–Cl(1) C(5)–N(5)–Co(1) N(6)–C(6)–C(5) N(8)–Co(2)–N(9) N(9)–Co(2)–N(7) N(9)–Co(2)–N(10) N(8)–Co(2)–N(6) N(7)–Co(2)–N(6) N(8)–Co(2)–Cl(2) N(7)–Co(2)–Cl(2) N(6)–Co(2)–Cl(2)
92.2(2) 92.7(2) 85.0(2) 90.3(2) 95.3(2) 91.4(1) 90.9(1) 121.8(4) 117.0(5) 91.9(2) 174.9(2) 85.6(2) 88.5(2) 92.5(2) 173.9(1) 89.1(1) 92.6(1)
Torsional angles (°) N(1)–C(1)–C(2)–N(2) N(7)–C(7)–C(8)–N(8) a
51.2(5) N(3)–C(3)–C(4)–N(4) 52.0(5) N(9)–C(9)–C(10)–N(10)
N atom of bridging ligand.
48.8(5) 51.1(6)
55
ing the L,L absolute configuration. All five-membered chelate rings adopt the d conformation (see Table 3 for torsion angles). The geometry at each cobalt centre (Table 3) is similar to that in 1, although it is noteworthy that the two Co–N bond lengths to the bridging en ligand are somewhat longer than those to the chelating en ligands. A consequence of the bridging is that the N–C–C angles in the bridging en ligand are widened considerably (114.2(5), 117.0(5)°), when compared with the comparable angles (109.8(2), 111.2(2)°) in the monodentate case. It thus appears that the effect of bridging is to introduce some stretching in the ligand itself, as seen in both the Co–N distances and N–C–C angles. An interesting feature of the structure is that the bridging en ligand exists in a gauche conformation (N5–C5–C6–N6=69.3(7)°), rather than the more common [13] anti conformation. However, the conformations about the two C–N bonds are both anti (Co1– N5–C5–C6=172.6(4)°; Co2–N6–C6–C5= 162.4(4)°); such differences in internal torsional angles destroy any potential crystallographic 2-fold symmetry within the complex. This anti–gauche–anti arrangement has not been previously observed in any binuclear complexes of en, and leads to an intermetal separation (Co1–Co2) of ˚ . Indeed, the only previously reported exam7.080(1) A ple of a bridging en with a gauche arrangement about the central C–C bond is in the polymeric complex of en with silver(I) perchlorate, but this has a gauche– gauche–gauche arrangement and an intermetal separa˚ [14]. tion of only 3.377(1) A The Co–Cl distances in both 1 and 2 are normal for complexes containing the Co(III)Cl(N)5 chromophore, with the values found in 2 being on the short side of the frequency distribution obtained for 83 compounds of this type [15]. The Zn–Cl distances and Cl–Zn–Cl angles in the ZnCl42 − anions are similar to those previously reported [16].
4. Supplementary material Complete tables of atom coordinates, anisotropic displacement parameters, and bond distances and angles are available from the author P.J. Steel.
References [1] A. Werner, Chem. Ber. 44 (1911) 1887. [2] D.A. House, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty, Comprehensive Coordination Chemistry, vol. 2, Pergamon, Oxford, 1987, p. 23. [3] M.D. Alexander, C.A. Spillert, Inorg. Chem. 9 (1970) 2344. [4] M.D. Alexander, H.G. Kilcrease, J. Inorg. Nucl. Chem. 35 (1973) 1583.
56
D.A. House, P.J. Steel / Inorganica Chimica Acta 288 (1999) 53–56
[5] [6] [7] [8]
H. Ogino, Inorg. Chem. 19 (1980) 1619 and Refs. therein. D.A. House, Helv. Chim. Acta 68 (1985) 1872. G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467. G.M. Sheldrick, SHELXTL, Bruker Analytical X-ray Systems, 1997. [9] D.A. House, V. McKee, W.T. Robinson, Inorg. Chim. Acta 157 (1989) 15. [10] (a) F.P. Fanizzi, G. Natile, L. Maresca, A.M.M. Lanfredi, A. Tiripicchio, J. Chem. Soc., Dalton Trans. (1984) 1467. (b) M. Cavellec, D. Riou, G. Ferey, Eur. J. Solid State Inorg. Chem. 32 (1995) 271. (c) M.I. Khan, R.C. Haushalter, C.J. O’Connor, Cuihong Tao, J. Zubieta, Chem. Mater. 7 (1995) 2807. [11] (a) G. Natile, F.P. Fanizzi, L. Maresca, A.M.M. Lanfredi, A. Tiripicchio, J. Chem. Soc., Dalton Trans. (1985) 1057. (b) A. Arzoumanian, A. Bouraoui, V. Lazzeri, M. Rajzmann, H. Teruel, H. Krentzien, New J. Chem. 16 (1992) 965. (c) L.M.
.
[12]
[13]
[14] [15] [16]
Meyer, R.C. Haushalter, J. Zubieta, J. Solid State Chem. 125 (1996) 200. (a) I. Bernal, J. Chem. Educ. 69 (1992) 468. (b) I. Bernal, J. Cetrullo, F. Somoza, J.S. Rice, R. Lewis, S.S. Massoud, J. Coord. Chem. 38 (1996) 41, and Refs. therein. (a) T. Miyoshi, T. Iwamoto, Y. Sasaki, Inorg. Chim. Acta 6 (1972) 59, and Refs. therein. (b) S.-I. Nishikiori, T. Iwamoto, J. Incl. Phenom. 3 (1985) 283. (c) A. Rabenau, R. Kniep, W. Welzel, Z. Kristallogr. 183 (1988) 179. (d) S. Buchholz, K. Harms, M. Marsch, W. Massa, G. Boche, Angew. Chem., Int. Ed. Engl. 28 (1989) 72. (e) D. Matkovic-Calogovic, M. Sikirica, Z. Kristallogr. 190 (1990) 171. (f) S.H. Yuge, T. Iwamoto, J. Incl. Phenom. 14 (1992) 217. E. Bang, Acta Chem. Scand., Ser. A 32 (1978) 555. D.A. House, Comments Inorg. Chem. 19 (1997) 327. D.A. House, V. McKee, Polyhedron 12 (1993) 2335.