DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 1951–1956 1951 Synthesis and supramolecular architectures of tetrakis(triorganostannyltetrazoles), including the crystal structure of hydrated 1,2,4,5-tetrakis(triethylstannyltetrazolyl)benzene Sonali Bhandari, Mary F. Mahon and Kieran C. Molloy * Department of Chemistry, University of Bath, Claverton Down, Bath, UK BA2 7AY. E-mail: chskcm@bath.ac.uk Received 4th March 1999, Accepted 26th April 1999 Six tetrakis(triorganostannyltetrazolyl)-alkanes and -benzenes have been prepared by a cycloaddition reaction between SnR3N3 and either 1,2,4,5-(NC)4C6H2, 1,1,3,3-(NC)4C3H4 or 1,3,3,5-(NC)4C5H8.All compounds contain tin in a trans-XYSnR3 environment; in anhydrous compounds the axial co-ordination about tin is exclusively from the tetrazoles (X, Y = N), while hydrated materials may also contain less symmetrical arrangements (X = N; Y = O). The structure of 1,2,4,5-tetrakis(triethylstannyltetrazolyl)benzene dihydrate has been determined and displays a complex three-dimensional network in which each tetrazole acts as at least a bidentate unit.One molecule of water co-ordinates one of the metal centres while the other is embedded in the lattice as a guest. Introduction We have been investigating the structural chemistry of organotin tetrazoles, influenced primarily by the variety of supramolecular lattices which these species generate.1–5 In such compounds the metal centre invariably adopts a trans-N2SnC3 geometry with a near-linear N–Sn–N moiety (established both crystallographically and by Mössbauer spectroscopy) thus acting as a rigid connector between multifunctional azoles.The polydentate nature of each tetrazole leads to a wide variety of supramolecular structures, the nature of which appears to be dependent on the hydrocarbon groups bonded to the tin. Thus, while 1,2-(Et3SnN4C)2C6H4 adopts a non-planar layer structure, its n-butyl analogue, 1,2-(Bu3SnN4C)2C6H4, exhibits a three-dimensional architecture with pores filled by the hydrocarbon groups.4 Other arrangements we have identified include a two-dimensional network of hexamers [1,3,5-(Bu3SnN4C)3- C6H3, 1,3,5-(Bu3SnN4CCH2CH2)3CNO2] 5 and a bilayer structure with channels running in all three directions.3 The latter arises when a flexible alkyl chain is used to link two organotin tetrazoles [1,6-(Bu3SnN4C)(CH2)6]. As the number of organometallic tetrazoles inherent in the molecular motif increases so, potentially, does the complexity of the lattice construct.We now report the syntheses of tetrakis(triorganostannyltetrazolyl)-alkanes and -benzenes as a natural extension of our earlier work on systems containing two and three organostannyl tetrazole moieties. The structure of 1,2,4,5-(Et3SnN4C)4C6H2?2H2O is presented and is the most complex yet of this family of compounds. Results and discussion Synthesis Six triorganotin-substituted tetra-tetrazoles 1–6 have been synthesized using the well established [312] cycloaddition route,2 in which a tetranitrile is heated with a slight excess of the appropriate azide under nitrogen in the absence of any solvent (Scheme 1).Reactions usually reached completion at elevated temperatures (100–170 8C) over one hour. The course of the reaction was followed by the disappearance of the IR bands due to the n(N3) at ª2060 cm21 and n(CN) at ª2250 cm21. The crude products in all cases were recrystallised from methanol.Cooling the methanolic solutions gave gummy materials for 1, 3–6, which needed trituration with hexane to give the respective products in a powder form. Compound 2 crystallised from methanol as a dihydrate in a form suitable for X-ray crystallography. Spectroscopy The 1H and 13C NMR data for compounds 1–6 are largely unexceptional but confirm the formulations shown in Scheme 1. The 13C NMR spectra of all species clearly show the quaternary carbon of the tetrazole at d ca. 160 confirming the result of the cycloaddition reaction; 1J(Sn–C) ª 480 Hz fall within the range for five-co-ordinate tin and the semiempirical relationship derived by Holecek and Lycka 6 for correlating 1J and C–Sn–C angles in butyltin compounds suggests a value of 1248 for compounds 1, 3 and 5, implying a trans-trigonal bipyramidal geometry about the metal centre. The 119Sn NMR spectra of compounds 1–6 exhibit resonances between d 240 and 280.In comparison with previous work on organotin-substituted tetrazoles this indicates a fiveco- ordinate tin.2 For example, the 119Sn chemical shifts of 1,2- [(R3Sn)N4C]C6H4 (R = Et, Bun or Pri), 1,3-[(R3Sn)N4C]C6H4 (R = Et or Bun) and 1,4-[(R3Sn)N4C]C6H4 (R = Bun or Pri) fall within the range of d 240 to 283 and are to low frequency of four-co-ordinated SnBu3(NMe2) (d 36).7 The five-co-ordination at tin could be achieved either via co-ordination of a solvent molecule (as for previously reported triorganostannyl tetrazoles, highly co-ordinating d6-DMSO was required for dissolution of NMR samples) or via formation of an oligomeric species.There is, however, no structural precedent for DMSO co-ordination in the solid state. In addition, the linewidths of the 119Sn resonances are broad (half width at half height, HWHH, ca. 470 Hz). Simple R3SnN4CR9 species exhibit similar spectral characteristics as a result of migration of the tin around the tetrazole nitrogens.2 The Mössbauer spectra for compounds 1–6 have isomer shifts (i.s.) in the range 1.30–1.55 mm s21 and quadrupole splitting (q.s.) between 3.5 and 3.9 mm s21.The former confirms the 14 oxidation state of the tin atom while the latter points towards a trans-trigonal bipyramidal geometry around tin, consistent with the NMR analysis. For comparison, q.s. values of 1,2- [(R3Sn)N4C]C6H4 (R = Et, Bun or Pri), 1,3-[(R3Sn)N4C]C6H41952 J. Chem. Soc., Dalton Trans., 1999, 1951–1956 Scheme 1 (R = Et or Bun) and 1,4-[(R3Sn)NC4]C6H4 (R = Bun or Pri) fall within the narrow range of 3.60–3.86 mm s21.4 The transtrigonal bipyramidal geometry about tin is achieved by axial co-ordination of the tetrazoles, a feature which is common in all published organotin tetrazole structures. Possible exceptions to this may occur, however, in the case of hydrated 2, 4 and 6.In these three cases, both trans-N2SnC3 and trans-NOSnC3 coordinations are possible, the latter arising if the intermolecular NÆSn is replaced by H2OÆSn, and both are consistent with the Mössbauer data.The quadrupole splittings for both possibilities (N2SnC3 vs. NOSnC3) fall within the same range, e.g. q.s. for crystallographically characterised 1,3-bis(tributylstannyltetrazolyl) benzene bis(methanol) is 3.65 mm s21.4 A precedent for simultaneous observation of both tin environments in the same lattice exists in bis(trimethylstannyl)-5,59-azotetrazole for which similar Mössbauer data have also been recorded (q.s.= 3.90 mm s21).8 Broad linewidths for 5 (G = 0.98, 1.07) and 6 (0.83, 1.05 mm s21) are possibly caused by the asymmetry inherent in the tetratetrazole ligands, which in turn may give rise to a combination of diVerent co-ordination modes between tin and the tetrazole nitrogens, e.g. N1 1 N2, N1 1 N3, N1 1 N4, etc. (see numbering in Scheme 1). Crystallography The asymmetric unit of compound 2 consists of three tins of unit occupancy [Sn(2), Sn(4), Sn(5)], two tins which coincide with inversion centres of half occupancy [Sn(1), Sn(3)], along with two separate ligand halves (Fig. 1). Selected bond lengths and bond angles are given in Table 1. The crystallographic symmetry at the two metal centres [Sn(1), Sn(3)] gives rise to disorder with respect to the attached ethyl groups such that only 2 of 6 b-carbons in these groups could be located with any certainty and refined. The overall structural analysis is in no way compromised by these diYculties.All tin environments are trigonal bipyramidal with equatorial ethyl groups. The asymmetric unit contains four trans-N2SnC3 [Sn(1)–Sn(4)] centres and one trans-NOSnC3 centre [Sn(5)]. Both these trigonal bipyramidal tin environments have been found in previously examined tin tetrazoles and are consistent with the spectroscopic interpretation (see above). The axially ligating atoms for the five tins, the N–Sn–N/N–Sn–O bond angles and the modes of co-ordination of the tetrazole ring with respect to the tins are summarised in Table 1.The seven unique Sn–N bond lengths are essentially equivalent within experimental error and the strength of N–Sn bonding is reflected in the proximity of all the N–Sn–N to 1808. The coordination between tetrazole and tin can be described with respect to the metal atom as being either N1 (see Scheme 1 for numbering; for tin, N1, N4 are equivalent) or N2 (N2, N3 are similarly equivalent).The versatility of the tetrazole coordination is reflected in the occurrence of both N1 1 N2 [Sn(2), Sn(4)] and N2 1 N2 [Sn(1), Sn(3)] environments. The N1 1 N2 co-ordination mode has been noted previously in 1,2- (Bu3SnN4C)2C6H4 while the N2 1 N2 mode has been found in 1,2-(Et3SnN4C)2C6H4.4 The gross three-dimensional structure of compound 2 (Fig. 2) is complex but can be broadly described in terms of layers. Propagation along c takes place primarily through the trans- N2Sn(3) [Sn(3) in the asymmetric unit as presented sits on an inversion centre at 0, 0.5, 0], while propagation along a takes place via trans-N2Sn(2) and trans-N2Sn(4).In addition, the lattice is extended in the b direction through the influence of the ligands, which are of two distinct types. The ligand based on C(1) (type A) has an inversion centre at the middle of the C6 ring (0.25, 0.75, 1.0) and is oriented asymmetrically with respect to b. The ligand based on C(7) (type B) has a twofold rotation axis through C(7) and C(10) parallel to b (0, y, 0.25) and is thus symmetrically disposed with respect to this axis.Both ligand types, but particularly those of type A, orchestrate lattice propagation into a third dimension. The pseudo-five-sided, 28-atom rings visible in Fig. 2 containJ. Chem. Soc., Dalton Trans., 1999, 1951–1956 1953 Fig. 1 The asymmetric unit of compound 2, showing the labelling scheme used in the text and Tables. Ellipsoids are at the 30% probability level.three tin atoms [Sn(2)–Sn(4)] and lie approximately in the ac plane. However, these rings are not planar and are tilted with respect to the b axis. They can be viewed as starting and finishing at tetrazoles based on C(5) sharing a common phenylene bridge (type A) and are highlighted in orange in Fig. 3. The tetrazoles labelled 1 or 2 on either side of the type A tetratetrazole are oriented approximately 308 with respect to the ac-plane and facilitate the “top to bottom” nature of these rings in the superstructure.The formation of the three-dimensional lattice is, however, complex as several features contribute to the propagation along b. First, there are two distinct types of ligands as described above. Secondly, the spirals associated with Sn(2) and Sn(4), the pseudo four-sided rings (Fig. 2), are not planar but are related by the screw axis at 0.25, y, 0.25 which propagates the lattice along b. Thirdly, there is a hydrogen-bonding interaction involving water [O(1)] which is co-ordinated to Sn(5) and N(3).This eVectively anchors the position of the two tetrazoles based on C(4) [via the nitrogens not co-ordinating Sn(1)] and generates a new 26-membered centrosymmetric macrocycle (Fig. 3; highlighted in green but sharing some common atoms with the 28-membered ring shown in orange). Finally, the lattice can also be viewed as an interpenetrating network. The pseudo-eightsided rings comprising of 38 atoms, built from 6 trans-N2Sn units and fragments of two type A and four type B ligands (Fig. 3, blue), have the trans-N2Sn(1) bridge (generated by the inversion centre at 0.25, 0.25, 1.0) involving ligand type A threaded through them. The hydrogen-bonding interactions discussed above result from an interaction between the water molecule [O(1)] coordinated to Sn(5) and N(3) of the lattice neighbour generated by the operation 1 2 x, 1 2 y, 2 2 z [O(1)–N(3): 2.65(2) Å].The distance Sn(5)–O(1) [2.27(1) Å] of compound 2 is comparable to Sn–O of hydrated 1,4-(Bu3SnN4C)2C6H4?H2O [2.368(6) Å].9 There is also a second water molecule [O(2)], not co-ordinated to tin but occupying an interstitial guest site within the lattice, which is hydrogen bonded to both O(1) and N(5) of the symmetry related molecule generated by the 0.5 2 x, 20.5 1 y, z transformation [O(2) ? ? ? O(1) 2.72(2); O(2) ? ? ? N(5) 2.84(2) Å]. This is the first example of a non-metal bound solvent guest in an organotin tetrazole lattice and suggests other inclusion species can be synthesized more rationally.Finally, the hierarchy for nitrogen co-ordination within the tetrazole is evident in the behaviour of the four independent heterocycles within the asymmetric unit (Fig. 1). Tetrazoles based on C(6) and C(11) exhibit N1 1 N3 co-ordination (Table 1; see Scheme 1 for numbering), this being the least sterically demanding combination and the one we have most commonly observed in other organotin tetrazole structures.The tetrazole incorporating C(4) also adopts N1 1 N3 co-ordination, with tin bound to N3 (the primary binding site) and the weaker hydrogen bond relegated to the use of N1. The tridentate tetrazole involving C(5) follows a similar pattern: primary co-ordination to tin using N1 1 N3, followed by the use of N4 for the hydrogen bonds. In summary, N1 1 N3 co-ordination imposes the least1954 J. Chem. Soc., Dalton Trans., 1999, 1951–1956 Fig. 2 The unit cell of compound 2 viewed along b. Colour code: Sn, blue; C, black; N, orange, O, green. Ethyl groups omitted for clarity. steric clash between bulky metal centres, and is the primary mode of tetrazole co-ordination. The use of N1 involves steric clashes with the hydrocarbon group attached to the adjacent carbon but these are less significant than metal–metal interactions which would arise from N2 1 N3 bonding. Hydrogen bonds are subservient to tin co-ordination and involve N1, then N4, for their formation. Conclusion Polyfunctional tetrazoles incorporating four organotin tetrazole units can be synthesized and used to construct complex three-dimensional supramolecular lattice arrangements.The structure of 1,2,4,5-(Et3SnN4C)4C6H2?2H2O has been determined as an example and emphasises the structural versatility of tetrazoles in orchestrating supramolecular architectures. The utility of polytetrazoles in the development of such structures is, however, limited by the increasing lack of solubility which accrues as more tetrazoles are incorporated into the ligands.Experimental Spectra were recorded on the following instruments: JEOL GX270 (1H, 13C NMR), GX400 (119Sn NMR), Perkin-Elmer 599B (IR). Details of our Mössbauer spectrometer and related procedures are given elsewhere.10 Isomer shift data are relative to CaSnO3. For all compounds, infrared spectra were recorded as Nujol mulls on KBr plates and all NMR data were recorded on saturated solutions in DMSO-d6.Syntheses The tributyltin and triethyltin azides were prepared by the literature methods.11 The method of Belsky 12 was used to prepare 1,3,3,5-pentanetetracarbonitrile.12 All other reagents were of commercial origin (e.g. Aldrich) and used without further purification. CAUTION: owing to their potentially explosive nature, all preparations of and subsequent reactions with organotin azides were conducted under an inert atmosphere behind a rigid safetyJ.Chem. Soc., Dalton Trans., 1999, 1951–1956 1955 Table 1 Selected structural data for compound 2a Tin Sn–N/Å N–Sn–N/8 Tin co-ordination a Tetrazole Tetrazole co-ordination b 12 34 5 d Sn(1)–N(1) 2.36(1) Sn(2)–N(8) 2.43(1) Sn(2)–N(9) 2.37(1) Sn(3)–N(13) 2.40(1) Sn(4)–N(6) 2.42(1) Sn(4)–N(15) 2.39(1) Sn(5)–N(11) 2.42(1) Sn(5)–O(1) 2.27(1) N(1)–Sn(1)–N(19) 180 N(9)–Sn(2)–N(8) 176.3(4) N(13)–Sn(3)–N(139) 180 N(6)–Sn(4)–N(15) 179.2(4) N(11)–Sn(5)–O(1) 175.6(5) N2 1 N2 N1 1 N2 N2 1 N2 N1 1 N2 N1 C(4) C(5) C(6) C(11) N1 1 N3 c N1 1 N2 1 N4 c N1 1 N3 N1 1 N3 a See Scheme 1 for numbering; with respect to tin, N1, N4 and N2, N3 are equivalent pairs.b See Scheme 1 for numbering. c Atom N1 involved in hydrogen bonding. d Tin co-ordinated to N, O. Fig. 3 A stereoscopic view of the unit cell of compound 2 highlighting the formation of 28- (orange), 26- (green) and 38-atom (blue) rings. Ethyl groups omitted for clarity.screen. None of the tetrazoles synthesized showed any tendancy to detonate at temperatures up to their melting points (ca. 200 8C). Syntheses 1,2,4,5-Tetrakis(tributylstannyltetrazolyl)benzene 1. A mixture of tributyltin azide (2.89 g, 8.7 mmol) and 1,2,4,5- tetracyanobenzene (0.39 g, 2.12 mmol) was heated under N2 at 120 8C for 45 min. The reaction mixture formed a white solid at this temperature, which was then dissolved in hot methanol. Hot filtration aVorded a green solution, which on cooling produced a green gum, which was then washed with hexanes to give 1 as a green powder (0.99 g, 30%), mp 210 8C (decomp.) [Found (Calc.for C29H55N8Sn2): C, 46.2 (47.2); H, 7.30 (7.20); N, 14.9 (15.1)%]. NMR [(CD3)2SO]: 1H, d 8.49 (s, 1 H, H3 of C6H2), 8.10 (s, 1 H, H6 of C6H2), 1.45 (m, 24 H, SnCH2CH2CH2CH3), 1.20–1.30 (m, 48 H, SnCH2CH2CH2CH3) and 0.77 [m, 36 H, (CH2)3CH3]; 13C, d 159.9 (CN4), 134.2 (C3,6 of C6H2), 117.7 (C1,2,4,5 of C6H2), 27.7 (SnCH2CH2CH2CH3), 26.5 [Sn(CH2)2- CH2CH3], 18.4 [SnCH2(CH2)2CH3], 13.5 [(CH2)3CH3], 2J[13CH2–117,119Sn] 77.2 (unresolved), 3J[13CH2–117,119Sn] 28.6 Hz (unresolved); 119Sn, d 248.6. 119mSn Mössbauer (mm s21): i.s. = 1.50; q.s. = 3.67. IR (cm21, KBr disk ): 3406, 2957, 2924, 2872, 2856, 1658, 1618, 1464, 1417, 1377, 1358, 1292, 1217, 1157, 1080, 1047, 1026, 879, 769, 700, 679, 524 and 432. 1,2,4,5-Tetrakis(triethylstannyltetrazolyl)benzene dihydrate 2. A mixture of triethyltin azide (0.92 g, 3.71 mmol) and 1,2,4,5-tetracyanobenzene (0.15 g, 0.84 mmol) was heated under N2 at 105 8C for 30 min.The reaction mixture formed a white solid at this temperature, which was washed with hexanes and dried in vacuo. The resultant white powder, which was partially soluble in methanol, was extracted in this solvent using a Soxhlet apparatus. Hot filtration aVorded a clear solution, which on cooling at room temperature produced colourless crystals (0.59 g, 56%), mp 200 8C [Found (Calc. for C17H33- N8OSn2): C, 33.5 (33.9); H, 5.32 (5.53); N, 17.8 (18.6)%].NMR [(CD3)2SO]: 1H, d 8.0 (s, 2 H, H3,6 of C6H2), 0.8–1.4 (m, 60 H, CH2CH3); 13C, d 160.2 (CN4), 131.1 (C3,6 of C6H2), 129.3 (C1,2,4,5 of C6H2), 9.7 (CH2CH3), 9.1 (CH2CH3), 1J[13C–117,119Sn] 478 (unresolved), 2J[13C–117,119Sn] 34.9 Hz (unresolved); 119Sn, d 243.2. 119mSn Mössbauer (mm s21): i.s. = 1.50; q.s. = 3.76. IR (cm21, KBr disk ): 3661, 3061, 2924, 2870, 1637, 1479, 1460, 1427, 1377, 1190, 1074, 1057, 1022, 997, 729, 698, 661, 524 and 447. 1,1,3,3-Tetrakis(tributylstannyltetrazolyl)propane 3. A mixture of tributyltin azide (2.07 g, 6.23 mmol) and 1,1,3,3- tetrapropanecarbonitrile (0.18 g, 1.30 mmol) was heated while stirring under N2 at 130 8C for half an hour. An orange-brown glass was formed at this temperature, which was dissolved in1956 J. Chem. Soc., Dalton Trans., 1999, 1951–1956 hot methanol. Hot filtration resulted in a yellow solution, which, on cooling, gave a yellow gummy substance.The yellow gum, when washed with hexanes, gave compound 3 as a yellow powder (0.43 g, 24%), mp 195 8C [Found (Calc. for C55H112- N16Sn4): C, 44.8 (44.0); H, 7.61 (7.58); N, 15.2 (14.9)%]. NMR [(CD3)2SO]: 1H, d 1.48 (m, 24 H, SnCH2CH2CH2CH3), 1.2–1.3 (m, 48 H, SnCH2CH2CH2CH3) and 0.78 [m, 36 H, (CH2)3CH3]; 13C, d 163.0 (CN4), 27.7 (SnCH2CH2CH2CH3), 26.4 [Sn(CH2)2- CH2CH3], 18.1 [SnCH2(CH2)2CH3], 13.5 [(CH2)3CH3], 2J[13C– 117,119Sn] 76 Hz (unresolved); 119Sn, d 250.2. 119mSn Mössbauer (mm s21): i.s. = 1.47; q.s. = 3.65. IR (cm21, KBr disk): 3420, 2957, 2924, 2872, 2855, 2073, 1653, 1635, 1464, 1377, 1342, 1292, 1155, 1126, 1026, 960, 879, 679 and 611. 1,1,3,3-Tetrakis(triethylstannyltetrazolyl)propane dihydrate 4. Prepared as for compound 3 using triethyltin azide (1.83 g, 7.38 mmol) and 1,1,3,3-tetrapropanecarbonitrile (0.26 g, 1.81 mmol). Yellow powder (1.75 g, 80%), mp 205 8C (decomp.) [Found (Calc. for C31H68N16O2Sn4): C, 31.8 (31.8); H, 5.68 (5.86); N, 19.0 (19.1)%].NMR [(CD3)2SO]: 1H, d 1.0–1.3 (m, 60 H, CH2CH3); 13C, d 163.5 (CN4), 10.1 (CH2CH3), 10.0 (CH2CH3), 1J[13C–117,119Sn] 478 Hz (unresolved); 119Sn, d 245.1. 119mSn Mössbauer (mm s21): i.s. = 1.53; q.s. = 3.87. IR (cm21, KBr disk): 3406, 3182, 2949, 2870, 2735, 1458, 1421, 1379, 1199, 1126, 1016, 956 and 684. 1,3,3,5-Tetrakis(tributylstannyltetrazolyl)pentane 5. Prepared as for compound 3 using tributyltin azide (2.13 g, 6.42 mmol) and 1,3,3,5-tetracyanopentane (0.26 g, 1.5 mmol).Yellow powder (1.56 g, 70%), mp 209 8C [Found (Calc. for C57H116N16Sn4): C, 45.6 (44.1); H, 7.73 (7.46); N, 14.9 (14.7)%]. NMR [(CD3)2SO]: 1H, d 2.50–2.80 [m, 4 H, C(CH2CH2)2], 1.48 (m, 24 H, SnCH2CH2CH2CH3), 1.20–1.25 (m, 48 H, SnCH2- CH2CH2CH3) and 0.76 [m, 36H, (CH2)3CH3]; 13C, d 160.0 (CN4), 27.7 (SnCH2CH2CH2CH3), 26.4 [Sn(CH2)2CH2CH3], 18.1 [SnCH2(CH2)2CH3], 13.5 [(CH2)3CH3], 1J[13C–117,119Sn] 476 (unresolved), 2J[13C–117,119Sn] 75.4 Hz (unresolved); 119Sn, d 253.5. 119mSn Mössbauer (mm s21): i.s. = 1.47; q.s. = 3.59. IR (cm21, KBr disk): 3387, 2957, 2924, 2872, 2856, 1655, 1589, 1464, 1400, 1377, 1342, 1292, 1251, 1226, 1080, 1049, 1026, 962, 879, 771, 748, 679, 611, 515 and 453. 1,3,3,5-Tetrakis(triethylstannyltetrazolyl)pentane hydrate 6. Prepared as for compound 3 using triethyltin azide (1.72 g, 6.9 mmol) and 1,3,3,5-tetracyanopentane (0.25 g, 1.5 mmol). Yellow powder (1.17 g, 68%), mp 206 8C (decomp.) [Found (Calc.for C33H68N16Sn4?H2O): C, 33.3 (33.5); H, 5.78 (5.92); N, 19.0 (18.9)%]. NMR [(CD3)2SO]: 1H, d 1.04–1.50 (m, 60 H, CH2CH3) and 2.48–2.55 [m, 4 H, C(CH2CH2)2]; 13C, d 161.5 (CN4), 121.9 [(CN4)2C], 38.2 [(CN4)2C(CH2)2(CH2)2], 21.9 [(CN4)2C(CH2)2(CH2)2], 10.9 [CH2CH3], 10.8 (CH2CH3), 1J[13C–117,119Sn] 482 Hz (unresolved); 119Sn, d 251.8. 119mSn Mössbauer (mm s21): i.s. = 1.43; q.s. = 3.63. IR (cm21, KBr disk): 2949, 2850, 1637, 1458, 1400, 1196, 1130, 1016, 962 and 682.X-Ray crystallography Suitable crystals of 1,2,4,5-tetrakis(triethylstannyltetrazolyl)- benzene dihydrate 2 were grown from methanol at room temperature. A crystal of approximate dimensions 0.25 × 0.25 × 0.3 mm was used for data collection. Crystal data. C34H66N16O2Sn4, M = 1205.79, monoclinic, a = 30.070(3), b = 14.241(2), c = 25.259(2) Å, b = 105.28(1)8, U = 10434(2) Å3, space group C2/c, Z = 8, Dc = 1.535 g cm23, m(Mo-Ka) = 1.936 mm21, F(000) = 4784.Crystallographic measurements were made at 293(2) K on a CAD4 automatic four-circle diVractometer in the range 2.17 < q < 23.928. Data (8368 reflections) were corrected for Lorentz-polarisation eVects and also for linear decay of the crystal during data collection. In the final least squares cycles all Sn, O and N atoms along with carbons 1–11 were allowed to vibrate anisotropically. Ethyl carbons were refined isotropically as a consequence of disorder of these groups which naturally arises from the site symmetry of the associated centres [Sn(1) and Sn(3)].Associated a-carbons were refined with half site occupancies but only two b-carbons could be reliably located and refined around these two metal centres. Hydrogen atoms were included at calculated positions where relevant on nondisordered ethyl groups. The hydrogen atoms on the water molecules could not be located with any reliability and were not modelled. The solution of the structure (SHELXS 86)13 and refinement (SHELXL 93)14 converged to a conventional [i.e.based on 4244 reflections with Fo > 4s(Fo)] R1 = 0.0628 and wR2 = 0.1451. Goodness of fit = 1.043. The maximum and minimum residual densities were 0.944 and 21.086 e Å23 respectively. CCDC reference number 186/1442. See http://www.rsc.org/suppdata/dt/1999/1951/ for crystallographic files in .cif format. Acknowledgements We thank the University of Bath for financial support in the form of a studentship (to S. B.). References 1 R. J. Deeth, K. C. Molloy, M. F. Mahon and S. Whitaker, J. Organomet. Chem., 1992, 430, 25. 2 S. J. Blunden, M. F. Mahon, K. C. Molloy and P. C. Waterfield, J. Chem. Soc., Dalton Trans., 1994, 2135. 3 A. Goodger, M. Hill, M. F. Mahon, J. G. McGinley and K. C. Molloy, J. Chem. Soc., Dalton Trans., 1996, 847. 4 M. Hill, M. F. Mahon, J. G. McGinley and K. C. Molloy, J. Chem. Soc., Dalton Trans., 1996, 835. 5 M. Hill, M. F. Mahon and K. C. Molloy, J. Chem. Soc., Dalton Trans., 1996, 1857. 6 J. Holecek and A. Lycka, Inorg. Chim. Acta, 1986, 118, L15. 7 B. Wrackmeyer, Annu. Rep. NMR Spectrosc., 1985, 16, 73. 8 M. F. Mahon, K. C. Molloy and S. F. Sayers, unpublished results. 9 S. Bhandari, Ph.D. Thesis, University of Bath, 1998. 10 K. C. Molloy, T. G. Purcell, K. Quill and I. Nowell, J. Organomet. Chem., 1984, 267, 237. 11 W. T. Reichle, Inorg. Chem., 1964, 3, 237. 12 I. Belsky, J. Chem. Soc., Chem. Commun., 1977, 237. 13 G. M. Sheldrick, SHELXS 86, A Computer Program for Crystal Structure Determination, University of Göttingen, 1986. 14 G. M. Sheldrick, SHELXL 93, A Computer Program for Crystal Structure Refinement, University of Göttingen, 1993. Paper 9/01737B