unidentate nitrogen base polymers

Inorganica Chimica Acta 358 (2005) 4307–4326 www.elsevier.com/locate/ica

Syntheses, structures and vibrational spectroscopy of some unusual silver(I) (pseudo-) halide/unidentate nitrogen base polymers Graham A. Bowmaker a,*, Effendy b,c, Brian W. Skelton b, Neil Somers b, Allan H. White b a

c

Department of Chemistry, University of Auckland, Private Bag 92019, Auckland, New Zealand b Chemistry M313, University of Western Australia, Crawley, WA 6009, Australia Jurusan Kimia, FMIPA Universitas Negeri Malang, Jalan Surabaya 6, Malang 65145, Indonesia Received 22 February 2005; accepted 4 April 2005 Available online 2 June 2005 Dedicated to Professor Hubert Schmidbaur.

Abstract The meagre (structurally defined) array of 1:2 silver(I) (pseudo-)halide:unidentate nitrogen base adducts is augmented by the single-crystal X-ray structural characterization of the 1:2 silver(I) thiocyanate:piperidine (
pip) adduct. It is of the one-dimensional
castellated polymer type previously recorded for the chloride:


Ag(pip)2(l-SCN)Ag(pip)2


a single bridging atom (S) linking successive silver atoms. By contrast, in its copper(I) counterpart, also a one-dimensional polymer, the thiocyanate bridges as end-bound SN-ambidentate:


CuSCNCuSCN


A study of the 1:1 silver(I) bromide:quinoline (
quin) adduct is recorded, as the 0.25 quin solvate, isomorphous with its previous reported
saddle polymer chloride counterpart. Recrystallization of 1:1 silver(I) iodide:tris(2,4,6-trimethoxyphenyl)phosphine (
tmpp) mixtures from py and quinoline (
quin)/ acetonitrile solutions has yielded crystalline materials which have also been characterized by X-ray studies. In both cases the products are salts, the cation in each being the linearly coordinated silver(I) species [Ag(tmpp)2]+, while the anions are, respectively, the discrete [Ag5I7(py)2]2 species, based on the already known but unsolvated [Cu5I7]2 discrete, and the ½Ag5 I7 ð1j1Þ 2 polymeric, arrays, and polymeric ½Ag5 I6 ðquinÞð1j1Þ  . The detailed stereochemistry of the [Ag(tmpp)2]+ cation is a remarkably constant feature of all structures, as is its tendency to close-pack in sheets normal to their P–Ag–P axes. The far-IR spectra of the above species and of several related complexes have been recorded and assigned. The vibrational modes of the single stranded polymeric AgX chains in [XAg(pip)2](1|1) (X = Cl, SCN) are discussed, and the assignments m(AgX) = 155, 190 cm1 (X = Cl) and 208 cm1 (X = SCN) are made. The m(AgX) and m(AgN) modes in the cubane tetramers [XAg(pip)]4 (X = Br, I) are assigned and discussed in relation to the assignments for the polymeric AgX:pip (1:2) complexes, and those for the polymeric [XAg(quin)](1|1) (X = Cl, Br) compounds. The far-IR spectra of [Ag(tmpp)2]2[Ag5I7(py)2] and its corresponding 2-methylpyridine complex show a single strong band at about 420 cm1 which is assigned to the coordinated tmpp ligand in [Ag(tmpp)2]+, and a partially resolved triplet at about 90, 110 and 140 cm1 which is assigned to the m(AgI) modes of the [Ag5I7L2]2 anion. An analysis of this pattern is given using a model which has been used previously to account for unexpectedly simple m(CuI) spectra for oligomeric iodocuprate(I) species.
2005 Elsevier B.V. All rights reserved. Keywords: X-ray crystal structures; Vibrational spectroscopies; Silver(I) complexes

1. Introduction *

Corresponding author. Tel.: +64 93737599x88340; fax: +64 9373 7422. E-mail address: [email protected] (G.A. Bowmaker). 0020-1693/$ - see front matter
2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2005.04.007

Structurally characterized examples of adducts of silver(I) halides with simple unidentate nitrogen bases of 1:2 stoichiometry remain sparse, being confined to that

4308

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

of silver(I) bromide with 3-methyl-pyridine, 3mp, binuclear [(3mp)2Ag(l-Br)2Ag(3mp)2] [1], and the unique one-dimensional
castellated polymer of silver(I) chloride with piperidine (
pip),


Ag(pip)2ClAg(pip)2Cl


[2]; the inclusion of pseudo-halides adds the silver(I) thiocyanate:quinoline (
quin) complex, also a linear polymer with ambidentate end-bound thiocyanate linking successive silver(I) atoms: –Ag(quin)2SCNAg(quin)2SCN– [3]. In all examples, the silver is fourcoordinate. In the present report, we describe a further addition to this array, AgSCN:pip (1:2), its novelty enhanced by the l-S bridging mode of the thiocyanate, recently also recorded but in an array of higher intrinsic symmetry than its pyridine (
py) analogue [4]. The unusual nature of the present complexes, and those below, has encouraged a parallel study of their vibrational spectroscopy, which we also record, taking advantage of the availability of data on similar copper complexes to extend the comparison, the structure of the CuSCN:pip (1:2) array also being recorded herein. Among the great variety of isomeric forms evinced by the adducts of 1:1 stoichiometry of coinage metal(I) halides with unidentate nitrogen bases, the adduct of silver(I) chloride with quin (as its readily desolvating 0.25 quin solvate) remains the sole example of the
saddle polymer [5], a key type in the description of such adducts as solvated fragments of parent halide lattice, consisting of a one-dimensional string of corner-fused faces of a putative face-centred rock-salt parent halide array. In the original record of synthesis and structure determination of that important type, it was noted that the rather less tractable bromide analogue displayed a similar unit cell; with the passage of time we have been successful in achieving a satisfactory determination of that complex also. Comparison with the chloride is desirable, since, despite the ostensibly planar array of the putative rock-salt unit cell face, perturbations induced by the incorporation of different atom sizes and potentially tetrahedral fourcoordinate metal environments, result in substantial deviations from that ideal, which, in the chloride, may be appreciated from the cell projections of [5]. These tendencies should increase as the size of the halide is increased on passing from chloride to bromide and their magnitude relative to tenability of the structural type is of interest. A considerable body of recent work has been concerned with the structural delineation of the nature of various adducts formed between silver(I) salts, AgX, and tertiary phosphine ligands, L = PR3, alone and in the presence of additional unidentate nitrogen base ligands L 0 , derivative of their usage in some instances as crystallization solvents. Although that work was primarily concerned with systems derivative of L = triphenyl- and tricyclohexyl-phosphine, and L 0 = py and pip, more limited essays have been undertaken with other

systems, notably, in the present context, tris(2,4,6-trimethoxyphenyl)phosphine,
tmpp. 1:1 Adducts of the latter, synthesized with AgX, X = Cl, Br [6], are notable in providing examples of P–Ag–X systems containing linear, two-coordinate silver(I); attempts to obtain a similar iodide have thus far been unsuccessful, the only material from the somewhat intractable product to be definitively characterized by a single-crystal Xray study being the ionic ½AgðtmppÞ2 2 þ ½Ag5 I7 ð1j1Þ 2 from acetonitrile [7], the silver(I) atom of the cation being linearly two-coordinate, while the anion is a complex polymer. In view of this result, we have studied some more agreeably crystalline products which we have obtained from some other unidentate nitrogen base solvents, those obtained from py and quin being the subject of room-temperature single-crystal X-ray studies as described hereunder, showing them also to be ionic, with [Ag(tmpp)2]+ cations and novel nitrogen base solvated Ag5Ix species based on oligo- and polymeric anions. Work recorded here and in accompanying and related papers referenced therein frequently involves the crystallization of desired materials from solution in neat liquid nitrogen base. For copper(I) adducts so described, Schlenk (anaerobic) conditions have been used; the silver(I) adducts are less demanding in respect of ambient conditions and satisfactory syntheses may usually be achieved by reaction in the atmosphere, without special precautions regarding its exclusion. Nevertheless, from time to time, its non-exclusion produces perceptible consequences, and we have found this to be particularly so when piperidine is used as solvent, the carbamate salt ((CH2)5NH2)+((CH2)5NCO2) Æ H2O often depositing. (Anal. Calc. for C11H24N2O3: C, 56.88; H, 10.41; N, 12.06. Found: C, 56.6; H, 10.2; N, 11.9%.) Because of its frequent occurrence, we have defined its unit cell dimensions the better to assist its rapid recognition and determined its crystal structure, providing comparison of the anion geometry with that of its sulfur counterpart, previously recorded as its piperidinium salt in two forms different from the present, both being anhydrous [8,9].

2. Experimental 2.1. Synthesis 2.1.1. MSCN:pip (1:2) The colourless crystalline complexes are obtained by slow cooling/evaporation of a solution of the parent thiocyanate in pip, typically 0.1 g in 5 ml, under Schlenk conditions for the copper(I) adduct; the complexes lose pip rapidly in ambient conditions, and their characterization rests on the single-crystal X-ray structure determinations and spectroscopy.

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

2.1.2. [Ag(tmpp)2]2[Ag5I7(py)2] Æ 2py AgI (1 mmol) and tmpp (1 mmol) were dissolved in py (5 ml), followed by warming to give a clear solution which, on cooling and standing, deposited colourless crystals of the product. Anal. Calc. for C118H142Ag7I7N2O36P4 Æ 2C5H5N: C, 37.59; H, 3.75; N, 1.37. Found: C, 37.6; H, 3.9; N, 1.1%. An isomorphous 2-methylpyridine (2mp) adduct was obtained similarly. 2.1.3. [Ag(tmpp)2][Ag5I6(quin)](1|1) Æ CH3CN AgI (1 mmol) and tmpp (1 mmol) were dissolved in a mixture of quin (5 ml) and acetonitrile (10 ml), followed by warming to give a clear solution which, on cooling and standing, deposited a few colourless crystals of the product whose characterization rests on the structural and spectroscopic studies. 2.2. Spectroscopy Procedural details are described in an accompanying paper [10]. Fresh samples of the complexes obtained from preparative procedures similar to those described above were used. Crystals were removed from the mother liquor and excess liquid was removed with absorbent paper. A mull of the sample was then prepared in the normal way, avoiding any delay that might result in loss of ligand from the complex. Samples prepared in this way usually contained a small amount of excess liquid ligand. 2.3. Structure determinations General procedural details are given in an accompanying paper [10]; full .cif depositions reside with the Cambridge Crystallographic Data Centre, CCDC Nos. 261019–261025. 2.3.1. Crystal/refinement details 2.3.1.1. CuSCN:pip (1:2). C11H22CuN3S, M = 291.9. CCD instrument; T ca. 153 K. Orthorhombic, space ˚, group Pnma ðD16 a = 11.018(2) A 2h ; No: 62Þ, ˚ , c = 5.8964(9) A ˚ , V = 1398 A ˚ 3. Dcalc b = 21.511(3) A (Z = 4) = 1.387 g cm3. lMo = 16.9 cm1; specimen: 0.35 · 0.25 · 0.2 mm; Tmin/max = 0.78. 2hmax = 58; Nt = 15 565; N = 1799 (Rint = 0.026), No = 1654; ˚ 3. R = 0.022, Rw = 0.032. |Dqmax| = 0.49(4) e A (x, y, z, Uiso)H were refined. 2.3.1.2. AgSCN:pip (1:2). C11H22AgN3S, M = 336.3. Single counter instrument, T ca. 295 K. Monoclinic, ˚, space group P21/c ðC 52h ; No: 14Þ, a = 11.373(4) A ˚ , c = 16.862(4) A ˚ , b = 105.56(2), b = 7.713(3) A ˚ 3. Dcalc (Z = 4 f.u.) = 1.567 g cm3. lMo = V = 1425 A 1 15.4 cm ; specimen: 0.41 · 0.59 · 0.40 mm; Tmin,max = 0.47, 0.63. 2hmax = 50; N = 2507, No = 1521; ˚ 3. R = 0.043, Rw = 0.042. |Dqmax| = 0.69(5) e A

4309

2.3.1.3. [Ag4Br4(quin)4](1|1) Æ (C10H9N). C45H35Ag4Br4, M = 1396.9. Single counter instrument, T ca. 295 K. Monoclinic, space group C2/c ðC 62h ; No: 15Þ, ˚ , b = 7.320(1) A ˚ , c = 23.163(8) A ˚, a = 30.55(1) A 3 ˚ b = 122.29(2), V = 4379 A . Dcalc (Z = 4) = 2.119 g cm3. lMo = 52 cm1; specimen: 0.18 · 0.35 · 0.16 mm; Tmin,max = 0.40, 0.47. 2hmax = 55; N = 5040, ˚ 3. No = 2545; R = 0.040, Rw = 0.040. |Dqmax| = 0.7 e A Variata. Cell/coordinate settings follow those of the isomorphous chloride [5]; as in the latter the solvent quin is modelled in space group C2/c as disposed about a centre of symmetry with the nitrogen scrambled over the available sites. 2.3.1.4. [Ag(tmpp)2]2[Ag5I7(py)2] Æ 2py. C118H142Ag7I7N2O36P4 Æ 2C5H5N, M = 4090. Single counter instrument, T ca. 295 K. Orthorhombic, space group ˚ ˚ Pbcn ðD14 2h ; No: 60Þ, a = 22.188(6) A, b = 16.787(1) A, 3 ˚ ˚ c = 39.60(1) A, V = 14 751 A . Dcalc (Z = 4 f.u.) = 1.842 g cm3. lMo = 23.0 cm1; specimen: 0.20 · 0.30 · 0.12 mm; Tmin,max = 0.59, 0.78 (Gaussian correction). 2hmax = 50; N = 12 940, No = 4288; R = 0.054, Rw = ˚ 3. 0.049. |Dqmax| = 0.86 e A Variata. Because of the long axis, data was measured by the x-scan technique; in spite of this, the limited data may be perturbed somewhat by profile overlap effects, as evidenced, perhaps, by a non-positive definite displacement tensor for C(135) (for which the isotropic form was used). Lattice py (No. 2) had very high
thermal motion although site occupancy refinement suggested it to be fully populated. It was refined using isotropic
thermal parameter forms and a constrained angle at C(22); nitrogen assignment from refinement and difference map evidence must be regarded as tentative. Similar material obtained from 2mp as solvent had a ˚, similar primitive orthorhombic unit cell: a = 22.49(1) A ˚ , c = 40.08(2) A ˚ , V = 15 100 A ˚ 3; in view of b = 16.75(1) A the consequent likely similarity of the two structures, the scale of the task and the meagre crystalline sample, a full determination was not proceeded with. 2.3.1.5. [Ag(tmpp)2][Ag5I6(quin)](1|1) Æ CH3CN. C63H73Ag6I6NO18P2 Æ C2H3N, M = 2643.9. Single counter instrument, T ca. 295 K. Triclinic, space group ˚ , b = 15.059(4) A ˚, c= P 1 ðC 1i ; No: 2Þ, a = 20.110(3) A ˚ , a = 70.94(2), b = 88.05(1), c = 87.93(2), 13.373(2) A ˚ 3. Dcalc (Z = 2 f.u.) = 2.187 g cm3. lMo = V = 4014 A 1 35.6 cm ; specimen: 0.03 · 0.32 · 0.10 mm; Tmin,max = 0.71, 0.93 (analytical correction). 2hmax = 45; N = 10 451, No = 4901; R = 0.062, Rw = 0.059. |Dqmax| = ˚ 3. 0.87(4) e A Variata. As modelled in the present cell/space group, silver atom Ag(1) was described as disordered over two sites in an ambivalent coordination mode correlating with alternative nitrogen atom assignment in the

4310

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

quinoline at sites 1 or 5. Site occupancy refinement suggested equivalent disorder and the population of each site was constrained at 0.5 in the final refinement model, with quin sites 1 and 5 modelled correspondingly (isotropic thermal parameters). This, coupled with limited data and high thermal motion in various components of the structure, is probably responsible for some nonpositive definite displacement ellipsoid behaviour at some ring peripheries; the relevant atoms (C(112/6, 125/6)) were modelled with the isotropic form. 2.3.1.6. (C5H12N)(C6H10NO2)(H2O). C11H24N2O3, M = 232.3. Single counter instrument, T ca. 295 K. Tri˚, clinic, space group P  1 ðC 1i ; No: 2Þ, a = 13.534(6) A ˚ ˚ b = 8.093(2) A, c = 6.471(5) A, a = 104.25(5), b = ˚ 3. Dcalc (Z = 2) = 102.54(5), c = 96.89(3), V = 659.2 A 3 1 1.170 g cm . lMo = 0.5 cm ; specimen: 0.41 · 0.31 · 0.71 mm (no correction). 2hmax = 50; N = 2330, ˚ 3. No = 1607; R = 0.043, Rw = 0.049. |Dqmax| = 0.1 e A (x, y, z, Uiso)H were refined.

3. Results and discussion 3.1. Structural studies 3.1.1. The solvated single-stranded polymers The nature of the adducts formed by the dissolution of silver(I) salts in ammonia has been a subject of interest and importance for some centuries, usually described, at least at an elementary level, in terms of the purportedly linear two-coordinate diammine silver(I) cation, [Ag(NH3)2]+. The predominance of this among other [Ag(NH3)n]+ arrays, n 6 4 in aqueous/ammoniacal solution is supported by the crystallization of its salts with oxyanions [11,12] but not, to this point (pseudo-) halides, a significant difficulty in isolating salts of this species being the supposed parallel formation of species such as azides by oxidation of the ammonia by silver(I). More extensive studies have been made using unidentate amines, mostly pyridine bases, many of which, with diverse attributes, may be obtained conveniently liquid under ambient conditions, and usefully behaving, themselves, as crystallization solvents. A parallel chemistry differing in significant ways, not least being ease of oxidation, exists for copper(I) counterparts; in terms of structural chemistry, size and electronic factors also generate significant differences. Among the adducts so obtained for silver(I) (pseudo-) halides, stoichiometries AgX:L (1:1) are readily obtained, AgX:L (1:2), perhaps surprisingly, much less so; the few structurally defined examples that have been described encourage the view that generally, in such species in the presence of halide, linear two-coordinate [AgL2]+ arrays are unlikely, neutral oligo-/polymeric forms [L2AgX](1|1) being the norm with a silver(I) co-ordination number of four. With X = halide, the two complexes

and types described in Section 1 remain the only simple examples, for X = (pseudo-) halide, the two thiocyanate forms and variations. As noted above, much work has been carried out using
planar pyridine bases with trigonal nitrogen; among the diverse sterically hindered variations usually achieved by substitution at the 2-,(6-) position(s), quinoline is a ligand which has presented an unusually high proportion of structural forms which may be considered
anomalous. Complexes of bases with
tetrahedral nitrogen are much less extensively studied, but thus far also show disproportionately unusual behaviour. For 1:2 stoichiometry, for CuX:quin (1:2), we find arrays of the common dimeric form [L2M(l-X)2ML2](Æ nL) for X = Cl [13], Br [13], I [14], while for X = SCN, a single-stranded
expanded helical
split-stair polymer, [(quin)2Cu(l2-SCN)](1|1) [15] obtains; for AgX, the only example, X = SCN, is the isomorphous


(AgL2) SCN(AgL2)SCN


[2]. For :NR3, the only example described is with AgCl, the


(AgL2)Cl(AgL2)Cl



castellated polymer [3] (L = pip). For 1:1 stoichiometry, whereas CuCl:quin (1:1) is the common [LM(l3-X)](1|1)
stair polymer [15], the bromide [16] and iodide [14] adducts are of an unusual
basket form [L2M2(l2-X)(l3-X)]2, derivative of the more common
step structure [L4M4X4], otherwise described only for ligands derivative of the heavier pnicogens; while AgCl, Br give the novel
saddle polymer, [(quin)Ag(l3-I)](1|1) is the common
stair polymer [17]. With :NR3 bases, [LAgX]4
cubanes are found for X = Br, I/L = pip [18], X = I/L = morpholine [19], NEt3 [17], while with HNEt2, X = Cl, Br, I [18], provide unique examples of the novel
tube polymer. (With CuI:NEt3 (4:3), the novel
linked cube array is obtained [20].) In this context, greater detail available with new/extended examples of the unusual
castellated and
saddle polymer forms provides an extended platform for meaningful assignments and comparisons of their vibrational spectroscopy. The results of the present room-temperature singlecrystal X-ray study are consistent with formulation of material prepared as above as an AgSCN:pip (1:2) complex in the form of a single stranded one-dimensional polymer (Fig. 1) in which successive silver(I) atoms are linked by bridging sulfur atoms from the thiocyanate groups, the resulting array resembling the
castellated polymer form of the chloride:

S Ag Ag

S

Ag

S Ag

One formula unit, devoid of crystallographic symmetry, comprises the asymmetric unit of the structure. Succes-

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

4311

Fig. 1. [(pip)2Ag(SCN)](1|1): projection of a section of the polymer strand, (a) normal to and (b) through the polymer plane.

sive elements of the polymer strand, which lies parallel to b, are generated from the formula unit, which comprises the asymmetric unit, by the 21-screw operation. The silver atom is four-coordinate, N2Ag(l-S)2, the remainder of the coordination sphere being made up by a pair of pip moieties; the N-functionality of the thiocyanate has no close interactions with metal atoms of adjacent strands. The –Ag(SCN)Ag(SCN)– array is closely planar; for an (NCS)Ag(NCS) unit defining such a plane, v2 is 146, the associated pip nitrogen atoms devi˚ . Parameters of the ating by 1.822(8), 1.89(1) A (AgS)(1|1) strand (Table 1) may be compared with those of the chloride [2] for which Ag–Cl,Cl 0 are 2.524(3), 2.667(3), a considerable asymmetry cf. the equivalence of the present Ag–S,S 0 . Cl–Ag–Cl 0 and Ag–Cl–Ag 0 are, respectively, 107.33(8) and 102.62(9); the angle at the pseudohalogen S atom (135.31(9)) is thus much greater than in the chloride counterpart. X– Ag–N(11,21) (120.3(2), 118.0(2) in the chloride) are much greater than X 0 –Ag–N(11,21) (99.0(2), 102.0(3) in the chloride) in both structures. N–Ag–N in the chloride is 106.9(3). In both the metal atom is equatorial relative to the ligand
chair.

The nature of this metal–thiocyanate polymer appears unique in silver(I) chemistry. In examples previously suggested as a precedent, successive metal atoms are linked by bridging thiocyanates which link through both ends rather than a single sulfur atom, i.e., the thiocyanate functions as an expanded halide. In AgSCN: quin (1:2) [3], the polymer string, although generated by a 21-screw like the present, is helical rather than planar, the helical expanded form of the polymer also being found in various 1:2 CuSCN unidentate N-base examples [15]; a number, however, do exhibit planar backbones in situations where the generator is a unit translation where the polymer lies parallel to a short crystallographic axis. We return to consider the planar nature of the polymer backbone. This functions as a quasi-mirror plane relating the two pip bases coordinated at each silver atom which are quasi-symmetrically thus disposed, as is also the case in the chloride. In the chloride, the two Ag–N distances diverge slightly from equivalence ˚ ); in the present complex, they dif(2.385(8), 2.347(11) A ˚, fer much more substantially and by more than 0.2 A a remarkable peculiarity. In both chloride and

4312

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

Table 1 AgSCN:pip (1:2): selected geometries Atoms

Parameter

Bond distances (A˚) Ag–S,S 0 Ag–N(11,21) C–S, N

2.524(3), 2.667(3) 2.385(9), 2.347(11)

2.508(2), 2.512(2); 2.525(1), 2.639(1); 2.484(1), 2.758(1) 2.315(8), 2.535(8); 2.262(4), 2.397(4); 2.308(3), 2.315(3) 1.573(8), 1.09(1); 1.662(4), 1.161(6); 1.667(4), 1.154(6)

120.3(2), 118.0(2) 99.0(2), 102.0(3) 107.33(8) 106.9(3) 102.62(9)

119.4(2), 118.0(2); 134.05(9), 106.53(9); 1054.9(1), 96.41(9) 98.8(2), 105.5(2); 111.65(8), 102.41(9); 118.6(1), 130.92(9) 112.36(8), 99.55(4), 96.51(4) 100.2(3), 98.9(1), 103.1(1) 135.31(9), 113.65(4), 96.51(4) 112.4(3), 112.2(3); 93.9(1), 103.5(1); 88.7(1), 100.3(1) 178.2(8), 178.6(4); 178.8(4)

Bond angles () S–Ag–N(11,21) S 0 –Ag–N(11,21) S–Ag–S 0 N(11)–Ag–N(21) Ag–S–Ag 0 C–S–Ag, Ag 0 S–C–N

Counterpart values for the py [4] analogue are given in italics (chains 1; 2), while counterpart values for the chloride are given in bold. Primed atoms are related by the generator of the polymer, the 21-screw axis. Torsion angles in the present compound are S,S 0 –Ag–N(11)–C(12,16) 105.7(6), 21.0(6); 16.2(6), 142.9(5); S,S 0 –Ag–N(21)–C(22,26) 113.5(7), 17.9(9); 13.0(8), 144.4(9).

thiocyanate structures, high displacement amplitudes are found, not surprisingly among the pip ligands, where lack of hydrogen-bonding and ligand-ring libration might be expected to contribute substantially. In the present structure, amplitudes are also high within the thiocyanate, not surprisingly at the terminal nitrogen, but rather so at the sulfur. In keeping with the relative instability of the crystal at room temperature, some decomposition was observed during the (rapid) data collection, deterioration of the repetitive standard reflections being about 15% and compensated for by appropriate scaling; given such difficulties, the ultimate residuals might be considered appropriately
normal. It might also be the case that the crystal had undergone some decomposition prior to its insertion in the capillary, but refinement of ligand site occupancies yielded no non-trivial differences from unity. A further possibility is that a weak superlattice may have been overlooked in the initial description of the crystal, while, also possible, but in our view unlikely is NCS rather than SCN bridging in a small proportion of sites, or that a small proportion of a chloride residue has been incorporated instead. A final possibility lies in the possible existence of a form of
isomerism which we have found in a number of other silver(I)/nitrogen base complexes, as yet unrecorded by us in the literature (but see below), in which ligands with long silver(I)–nitrogen bonds may be regarded (within their thermal envelopes) as exhibiting at any given time differing degrees of coordination/ dissociation with/from the neighbouring silver atoms, in turn affecting their interactions with other neighbouring ligands and leading in favourable cases, to resolution and refinement of associated disordered components; unrewarding attempts have been made here to define and refine any such disordered components along the long principal axis of the sulfur atom which lies approximately normal to the polymer plane. The

considerable disparity in the Ag–N(pip) distances, however, perhaps may be indicative of such incipient dissociation. The recently described AgSCN:py (1:2) adduct [4] is also of the form [LAg(l-SCN)](1|1). In that structure we find that, whereas in the present, the (AgSCN)(1|1) spine of the polymer essentially lies in a quasi-mirror plane which relates the two ligands to either side. There the generator of each of the two independent strands of the polymer is a glide plane, so that (AgS)(1|1) lies close to the mirror component, as does one ligand (but which lies quasi-normal to it), but the other ligand and the SCN groups project outwards to either side. The companion [(py)2Cu(SCN)](1|1) structure has quasi-m symmetry like the present, but the (pseudo)-halide now bridges successive metal atoms in expanded form. In this respect, this latter structure closely resembles that of CuSCN:pip (1:2), [(pip)2Cu(SCN)](1|1), a result of the present work, where the crystallographic mirror plane of space group Pnma contains the [Cu(SCN)](1|1) spine and relates the pair of ligands which lie disposed to either side, one half of the formula unit comprising the asymmetric unit of the structure, in a tidily packed array (Fig. 2(b)). Again the metal atom is equatorial on the ligand chair. The geometries of the four MSCN:L (M = Cu, Ag; L = py, pip) arrays are given comparatively in Tables 1 and 2.

3.1.2. The ‘saddle’ polymers, AgX:quin (:quin) (1:1 (:0.25)) The adduct obtained on crystallizing silver(I) bromide from quin is isomorphous with its chloride counterpart, as a
saddle polymer [5], comprising corner-shared faces of the rock-salt structure, with two different types of silver atom, those along the polymer spine in environments of four halides, and those at the periphery N2AgX2

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

4313

Fig. 2. [(pip)2Cu(SCN)](1|1): (a) projection of the polymer strand normal to the crystallographic mirror plane containing the spine and (b) unit cell contents, projected down c.

Table 2 CuSCN:pip (1:2): selected geometries Atoms

Parameter

Bond distances (A˚) Cu–S Cu–N 0 Cu–N(1) S–C N–C

2.3077(5); 2.304(1) 1.942(1); 1.952(2) 2.130(1); 2.065(2), 2.103(2) 1.660(2); 1.656(3) 1.158(2); 1.156(3)

Bond angles () S–Cu–N 0 S–Cu–N(1) N–Cu–N(1) N(1)–Cu–N(100 ) Cu–S–C Cu 0 –N–C S–C–N Cu–N(1)–C(2) Cu–N(1)–C(6)

112.96(5); 112.3(1) 108.79(3); 108.87(8), 112.24(7) 112.42(4); 110.3(1), 111.3(1) 100.74(4); 101.3(1) 103.94(6); 102.6(1) 173.9(2); 171.1(3) 177.1(2); 178.4(3) 116.75(9); 119.3(2), 121.6(2) 111.66(8); 123.8(2), 121.3(2)

Primed atoms are generated by the unit c translation generator of the polymer, doubly primed atoms by the mirror containing the spine. Counterpart values for the py analogue [4] are italicized.

(Fig. 3). The chloride structure has been described in detail in [5]; comparative geometries of the chloride and bromide are given in Table 3, offering no surprises.

3.1.3. The [Ag(tmpp)2]+ complex salts 3.1.3.1. The cations. As in the structural characterization of the unsolvated parent ½AgðtmppÞ2 2 þ ½Ag5 I7 ð1j1Þ 2 [7], the definition of the nature of the present species, both in stoichiometric and stereochemical detail, rests overwhelmingly on single-crystal X-ray studies; the latter, in the present examples, are more precise than that of the parent, but nevertheless, not without difficulty in respect of disorder and unit cell size as outlined previously and below. The asymmetric unit of each structure comprises an [Ag(tmpp)2]+ cation, as in the above parent; cation symmetries and stereochemistries in each case (Table 4, Fig. 4) are essentially identical to those described previously for the parent and the only other structurally characterized example in the [(py)Ag(CN)2] salt [21] – closely eclipsed phosphorus atom substituents in projection, closely tetrahedral phosphorus atoms, staggered O(Me) arrays with constant Ag


O and O


O substituent contacts representing interlocking oxygens, O(lm2) (2 · 3) about the silver, and substituent rings at the same, constant pitch, are all indicative of a cation of very tightly determined internal disposition. A combination of energetics derived from stability of this cation, perhaps coupled with

4314

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

Table 3 [Ag4X4(quin)4](1|1), X = Cl ([5]), Br (this work): geometrical parameters Atoms

Parameter

Bond distances (A˚) Ag(1)


Ag(3) Ag(2)


Ag(3) Ag(1i)


Ag(3) X(1)


X(2) X(1i)


X(2) Ag(2)–N(11) Ag(2)–N(21) Ag(1)–X(1i) Ag(1)–X(2) Ag(2)–X(1) Ag(2)–X(2) Ag(3)–X(1) Ag(3)–X(2)

3.590(3), 3.685(2) 3.1130(2), 3.089(1) 3.626(3), 3.635(2) 4.311(5), 4.558(1) 4.376(5), 4.685(2) 2.27(1), 2.287(7) 2.28(2), 2.281(6) 2.627(4), 2.713(1) 2.639(4), 2.722(1) 2.725(1), 2.806(1) 2.734(4), 2.787(1) 2.600(4), 2.706(1) 2.603(4), 2.716(1)

Bond angles () X(1i)–Ag(1)–X(2) X(1)–Ag(1)–X(1ii) X(1ii)–Ag(1)–X(2) X(1)–Ag(2)–X(2) X(2)–Ag(1)–X(2iii) N(11)–Ag(2)–N(21) X(1)–Ag(2)–N(11) X(1)–Ag(2)–N(21) X(1)–Ag(3)–X(1iii) X(1)–Ag(3)–X(2) X(1)–Ag(3)–X(2iii) X(2)–Ag(2)–N(21) X(2)–Ag(2)–N(11) X(2)–Ag(3)–X(2iii) Ag(1iv)–X(1)–Ag(2) Ag(1iv)–X(1)–Ag(3) Ag(2)–X(1)–Ag(3) Ag(1)–X(2)–Ag(2) Ag(1)–X(2)–Ag(3) Ag(2)–X(2)–Ag(3)

112.7(1), 114.59(3) 91.5(1), 95.59(5) 125.2(1),119.71(3) 104.3(1), 109.14(4) 92.7(1), 94.53(5) 125.0(5), 122.6(3) 98.9(3), 101.0(2) 111.6(3), 107.8(2) 92.8(1), 95.89(5) 111.9(1), 114.41(3) 124.6(1), 119.56(3) 101.7(3), 105.3(2) 114.0(2), 110.5(1) 94.0(1), 94.82(5) 128.1(1), 121.73(3) 87.9(1), 84.26(4) 72.0(1), 68.13(3) 124.2(1), 119.41(3) 86.6(1), 85.33(4) 71.8(1), 68.28(3)

Transformations of the asymmetric unit: i: x, y + 1, z; ii: 2  x, 1 + y, 1/2  z; iii: 2  x, y, 1/2  z; iv: x, y  1, z.

incapacity of the bulkier iodide to coordinate as [(tmpp)AgX] in the manner of the chloride and bromide, and its ready capability to form stable polyiodoanions, may account for the apparent relative ease of accessibility thus far of these complex salts, cf. (e.g.) [(tmpp)AgI], which has not yet been structurally characterized. The Ag–P distances are intermediate between the (quite divergent) values found in the only other two mononuclear, linear bis(phosphine)silver(I) complexes which have been reported to date: [Ag{P(mes)3}2](PF6) ˚ ) [22], and (
mes = C6H2Me3-2,4,6; Ag–P 2.461(6) A ˚ ) [23]. [Ag{P(CH2CH2CN)3}2](NO3) (Ag–P 2.383(1) A The distance in [Ag{P(mes)3}2]+ is long in comparison with those in other tertiary phosphine complexes of silver, and this has been suggested as consequent on intramolecular overcrowding between mesityl groups on the opposing ligands [22]. The above bond length data are therefore consistent with a decrease in the degree of steric crowding in the order [Ag{P(mes)3}2]+ > [Ag(tmp-

Fig. 3. A section of the AgBr:quin (1:1)
saddle polymer, normal to the
plane of the Ag4Br4 unit.

p)2]+ > [Ag{P(CH2CH2CN)3}2]+. The other component of the asymmetric unit is a suitably charged anionic fragment: one half of [Ag5I7(py)2]2 in the case of the pyridine complex (together with one independent pyridine solvent molecule), one whole [Ag5I6(quin)] section of the one-dimensional polymer in the case of the quinoline complex (together with one independent acetonitrile residue). Unit cell projections, given for the present compounds in Fig. 5, show that in all cases, the cations and anions form alternate layers approximately normal to one of the crystallographic axes, normal to b in the parent, c in the py complex, and a in the quin complex, and also to the P–Ag–P core of cations packed side by side in a manner possibly dictated by a constant ovoidal envelope, that in turn dictated by tight internal packing of the phenyl rings and their substituents, as noted above. In all cases, the P–Ag–P axes of the cations lie (quasi-) parallel within the cation sheet; projection down that vector shows a remarkable and persistent packing array, the energetics of which may also be a determinant of the similarities of these three structures. In the latter context, it is of interest to revisit the structure of AgCN:tmpp (:py) (1:1 (:1)) ” [Ag(tmpp)2][(py)Ag(CN)2] in more detail [21]. It will be observed that packing mode of the cations in two dimenthe sional sheets (Fig. 5) lends itself to partitioning into discrete columns, and such is the disposition, in fact, in the cyanide structure, where in projection down a, a view containing the cations only is similar in aspect to that of the py, quin polyiodide adducts (Fig. 5(e)(i)). Projec-

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

4315

Table 4 [Ag(tmpp)2]+ cation geometrical parameters Atoms


parent


py adduct


quin adduct

[(py)Ag (CN)2]

2.36(2), 2.38(2) 2.36(3), 2.40(3)

2.414(4)

2.411(6)

2.417(2)

2.409(4)

2.426(6)

–

Ag


O(2) (range) Ææ

2.72(5) 3.03(5) 2.89(8)

2.82(1) 2.90(1) 2.87(3)

2.83(1) 2.95(1) 2.88(5)

2.896(5) 2.923(5) 2.91(1)

O(2)


O(2) (intraligand) Ææ

4.29(7) 4.74(8) 4.55(12)

4.42(1) 4.60(1) 4.50(7)

4.38(2) 4.67(2) 4.52(11)

4.492(6) 4.590(7) 4.53(4)

O(6)


O(6) (intraligand) Ææ

2.79(9) 3.11(8) 3.04(9)

2.97(1) 3.16(2) 3.07(6)

2.91(2) 3.25(3) 3.05(11)

2.965(8) 3.130(7) 3.06(7)

O(2)


O(2) (interligand) Ææ

3.36(7) 3.90(10) 3.55(20)

3.39(1) 3.73(1) 3.55(14)

3.37(2) 3.99(2) 3.56(20)

3.525(6) 3.771(8) 3.68(11)

P


O(6) (intraligand) Ææ

3.02(6) 3.21(5) 3.08(6)

3.07(1) 3.10(1) 3.08(1)

3.05(2) 3.11(2) 3.09(2)

3.072(6) 3.089(5) 3.079(7)

P


O(2) (intraligand) Ææ

2.76(5) 2.97(5) 2.86(6)

2.86(1) 2.89(1) 2.87 (1)

2.83(2) 2.93(2) 2.88(3)

2.836(6) 2.860(4) 2.85(1)

175.9(9), 179(1) 108(3) 121(3) 112(3)

177.9(2)

178.5(2)

177.38(7)

109.3(5) 112.0(5) 110.5(9)

109.7(7) 112.4(7) 111(1)

109.0(2) 111.0(2) 110.2(9)

98(4) 113(2) 107(4)

107.5(7) 109.7(7) 108.6(7)

106(1) 111(1) 108(2)

107.6(2) 109.3(3) 108.7(8)

30(1) 35(1) 33(2)

28(1) 38(2) 33(3)

34.8(5) 37.1(5) 36(1)

Bond distances (A˚) Ag–P(1) Ag–P(2)

Bond angles () P(1)–Ag–P(2) Ag–P–C Ææ C–P–C Ææ

Torsion angles () (i) Ag–P–C(n1)–C(n2) 32(4) 44(5) Æiæ 37(3)

Counterpart values are included for the cations of the
parent ½Ag5 I7 ð1j1Þ 2 [7] and the [(py)Ag(CN)2] [21] salts. In the latter salt, the cation is disposed on a crystallographic 2-axis.

tion of the full cell down c, however, shows that the illusion of coplanarity presented by Fig. 5(e)(i) in projection, columns along c, paralis, in fact, made up of lel, but displaced by half a cell in a by virtue of the C-centring of the non-primitive space group C 2/c. 3.1.3.2. The anions 3.1.3.2.1. The pyridine complex. The anionic aggregate in this species is modelled as a discrete [Ag5I7(py)2]2 species (Table 5), disposed on a crystallographic two-fold axis in orthorhombic space group Pbcn. Discrete [M5X7]2 anionic polyhalide coinage metal species

Fig. 4. Projection of the cation of [Ag(tmpp)2]2[Ag5I7(py)2], (a) normal to the P–Ag–P axis and (b) down the P–Ag–P line (P(1) nearest the viewer). The aspects of the same cation in all salts hitherto described structurally [(py)Ag(CN)2] [21], [Ag5I7]2 [7] and [(py)2Ag5I7]2 (this work) are essentially identical (see Table 4).

uncomplexed by additional base have been described for [Cu5X7]2 (X = Br, I) [24–26], both with perturbed/ incipient D5h point symmetry (Fig. 6(a)). The present py complexed ion (Fig. 6(b)) may be fruitfully viewed as being derivative of this prototypical array; the perturbation of a pair of metal atoms cis- oid from the equatorial belt/
plane is enhanced by complexation by the py rather than the more distant second apical I(4) halogen. Conversely, it may be regarded as derivative of solvation of these moieties in the ½Ag5 I7 ð1j1Þ 2 polymer, where such fragments may be recognized as linked (Fig. 6(c)) [7].

4316

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

Fig. 5. Unit cell contents of the two anionic complexes, showing (a) the py anionic complex, projected down b and (b) the quin anionic polymer complex, projected down c, with (c) the unsolvated ½Ag5 I7 ð1j1Þ 2 array [7], down c, showing in each case the layers of cations (and anions, as appropriate) within each structure. (d) (i), (ii), the cation arrays for (a) and (b) projected (quasi-)normal to the sheet, showing the cation packing. (e) (i), (ii) gives projections of the structure of [Ag(tmpp)2][(py)Ag(CN)2] from [21] (i) down a (cations only) and (ii) the full structure, down c.

3.1.3.2.2. The quinoline complex. This anion, formulated as ½Ag5 I6 ðquinÞð1j1Þ  (Table 6) is an infinite one-dimensional polymer, parallel to b. Adjoining strands are stacked side by side up c, interleaved with quinoline molecules. The quin is intimately associated with nearby silver atoms Ag(1) in independent strands to either side, the silver atoms being modelled as distributed over a pair of sites Ag(1a, 1b), each with site occupancy 0.5() and separated this time not by a small distance but the width of the polymer, i.e., on this occasion, the silver sites are not similar components of an atom with two choices of a substantially similar environment, but rather, occupancy or not of two sites in distinctly different locations. Assignment of the quin nitrogen is made therefore on the basis of occupancy or otherwise of the nearby silver site – the nitrogen at position 1 of the fused ring system, requires a neighbouring silver atom at site a at a normal bonding dis˚ and, simultaneously no nitrogen at tance of 2.31(3) A site 5 (which must in those circumstances be carbon) and no silver at site b nearby in the neighbouring strand. With nitrogen at site 5, the latter site b must be occu-

pied, while site a of the parent strand is unoccupied. Views of the polymer are shown in Fig. 7, firstly with both sites a, b occupied and modelled with nitrogen atom at both positions 1 and 5, and then with deconvoluted strands showing the two alternatives: silver site a occupied and nitrogen at position 1 and then site b occupied and nitrogen at position 5 of the quinoline ring, the overall structure (and, presumably, the overall strand) being a composite of the two types. Sites a and b are both four-coordinate. As with most such polyhalide aggregates, a number of basic motifs may be identified in both
a and
b types of the present array. The Ag2I2 dimer/rhomb is self-evident; the other important motif is the Ag4I4
cubane or Ag3I4
incomplete cube, completed by the addition of Ag(1a) in the
a polymer. The unit completed by the addition of Ag(1b) is more complex, being essentially a cube in which the Ag(4)– I(4) edge has been splayed by the separation of Ag(4) into Ag(4) and Ag(4 0 ) by the inversion centre, so that the acute corners of four rhombs rather than the usual three meet at I(4). Other descriptions are also possible, e.g., in terms of Ag(3)/Ag(4) separation.

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

4317

Fig. 5 (continued )

3.2. Vibrational spectra The infrared spectra of the pip and quin complexes reported in the present study were recorded in order to investigate further the correlations between the vibrational frequencies and the structures of the complexes as determined by the X-ray studies for these unusual forms. The far-IR spectra of these and some related complexes are shown in Figs. 8–10. The relatively sharp bands above 250 cm1 are assigned to the coordinated ligands, by reference to the spectra of the uncomplexed ligands pip (544 s, 445 w, 429 m, 403 w, 391 w, 248 w) and quin (628 w, 611 s, 478 s, 391 w, 376 m, 181 m

cm1). The bands below 250 cm1 are due to vibrations of the AgX chains or oligomers. Assignments are given in Table 7, and the bases of these assignments are discussed below. The far-IR spectra of the two single-stranded chain polymers [XAg(pip)2](1|1) (X = Cl, SCN) are shown in Fig. 8. These compounds are of particular interest because they contain one of the simplest possible chain-polymer structures, one which is closely related to that observed in AgCN and some of its complexes [27,21]. In the latter case, the CN group acts as a linear bridge between silver atoms in the chain, whereas in the present cases, the Cl and SCN groups act as non-linear

4318

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

Table 5 Core geometry of the [Ag5I7(py)2]2 anion Atoms

Parameter

Bond distances (A˚) Ag(1)–N(1) Ag(1)–I(1) Ag(1)–I(3) Ag(1)–I(4) Ag(2)–I(1) Ag(2)–I(4) Ag(3)–I(2) Ag(3)–I(3) Ag(3)–I(4) Ag(3)–I(4i)

2.35(1) 2.781(2) 2.827(2) 3.060(2) 2.787(2) 2.930(2) 2.810(3) 2.704(3) 2.971(2) 3.195(2)

Bond angles () N(1)–Ag(1)–I(1) N(1)–Ag(1)–I(3) N(1)–Ag(1)–I(4) I(1)–Ag(1)–I(3) I(1)–Ag(1)–I(4) I(3)–Ag(1)–I(4) I(1)–Ag(2)–I(4) I(1)–Ag(2)–I(1i) I(1)–Ag(2)–I(4i) I(4)–Ag(2)–I(4i) I(2)–Ag(2)–I(3) I(2)–Ag(3)–I(4) I(2)–Ag(3)–I(4i) I(3)–Ag(3)–I(4) I(3)–Ag(4)–I(4i) I(4)–Ag(4)–I(4i) Ag(1)–I(1)–Ag(2) Ag(3)–I(2)–Ag(3i) Ag(1)–I(3)–Ag(3) Ag(1)–I(4)–Ag(2) Ag(1)–I(4)–Ag(3) Ag(1)–I(4)–Ag(3i) Ag(2)–I(4)–Ag(3) Ag(2)–I(4)–Ag(3i) Ag(3)–I(4)–Ag(3i)

98.8(4) 103.7(4) 104.6(4) 131.35(9) 109.50(7) 105.71(7) 113.17(4) 112.7(1) 107.87(4) 101.62(9) 123.81(8) 104.76(7) 99.18(6) 111.56(8) 118.21(8) 94.79(6) 66.35(6) 60.06(7) 65.47(6) 61.11(4) 59.49(6) 105.02(6) 77.05(6) 73.60(6) 54.12(6)

Transformation of the asymmetric unit: i: 2  x, y, 1/2  z.

bridging groups. Fig. 11 shows a comparison between the vibrational modes of a linear AgCN chain, and those of the non-linear AgCl chain in [ClAg(pip)2](1|1). A fundamental difference between these cases concerns the number of m(AgX) modes. For the linear AgX chain (X = CN), there is only one m(AgX) mode, m1, despite the fact that there are two inequivalent Ag–X bonds, Fig. 11(a). For the non-linear chain, there are two such modes, m1 and m2, Fig. 11(b). In order to estimate the expected frequencies of these two bands, we use the recently determined relationship between m(AgX) and the AgX bond length r(AgX) [28]. The Ag–Cl bond lengths ˚ [2], and in [ClAg(pip)2](1|1) are 2.524(3), 2.667(3) A these yield m(AgCl) = 201, 152 cm1, respectively. The two strongest (and highest frequency) bands in the region below 250 cm1 occur at 190 and 155 cm1. Since these frequencies agree reasonably well with the predictions based on the bond lengths, they are assigned to

the two expected m(AgCl) modes. The assignment of the several additional bands that are evident in the region below 150 cm1 is less certain. The mode labelled m3 in Fig. 11 can be described as a counter-vibration of the Ag sublattice against the Cl sublattice, and is expected to occur at lower frequencies than the m(AgCl) modes, as this essentially involves a rotation of the AgCl polymer chain. However, this mode can couple with the m(AgN) vibrations, which are also expected to lie below 200 cm1 (see below), and this may explain the complexity of the spectrum in the lower frequency region. The structure of [(NCS)Ag(pip)2](1|1) is slightly more complex than that of the chloride, but it still contains a relatively simple single-stranded Ag(SCN)(1|1) polymer backbone (see above). In contrast to the situation for AgX (X = Cl, Br, I) complexes [28], no relationship has yet been established between m(AgS) and the Ag–S bond length in AgSCN complexes. In fact, the only previously reported assignment of such a mode is in [(NCS)Ag{P(C6H11)3}]2, where m(AgS) = 174 cm1 ˚ [29]. Since the Ag–S bond for r(AgS) = 2.572(3) A ˚) lengths in the present complex (2.508(2), 2.512(2) A are shorter than this, m(AgS) should be greater than 174 cm1. Thus, the band at 208 cm1 is reasonably assignable to m(AgS). The repeat unit in this complex contains two AgS units, so the vibrational modes of the polymer chain are more complex than those depicted for the AgCl complex in Fig. 11(b). However, the two Ag–S bond lengths are nearly equal in this case, so on the basis that the frequency is primarily determined by the bond length, only a single m(AgS) band is expected. Interestingly, application of the formula relating m(AgX) and r(AgX) for X = Cl to the present thiocyanate complex yields m(AgS) = 206 cm1, in excellent agreement with the observed value of 208 cm1. Coordinated pip ligands generally show bands at about the same frequency, or shifted to slightly higher frequencies, relative to those of the uncomplexed ligand. This is the case, for example, for the ligand band at about 445 cm1 (Fig. 8) which also gains significantly in intensity upon coordination of the pip, suggesting a significant degree of coupling with the m(AgN) vibrations. Such vibrations are expected to occur below 200 cm1 (see below), and probably contribute to the general strong absorption intensity observed in that region. The far-IR spectrum of [(SCN)Cu(pip)2](1|1) (Fig. 8(c)) is similar to that of the silver analogue (Fig. 8(b)), but the m(AgS) = 208 cm1 band in the latter compound is replaced by a doublet at 205, 224 cm1. The structures of these two compounds differ in that the thiocyanate in the silver complex is bound in an AgS Ag fashion, whereas the copper complex shows Cu– SCN–Cu bonding (see above). In the latter case, both

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

4319

Fig. 6. (a) The [Cu5Br7]2 species of [25] showing its approach to D5h point symmetry and (b) the anion of the present py complex, (i) normal to, and (ii) down the quasi-2 axis. (c) The ½Ag5 I7 2 fragment of the anion of [7] plotted similarly.

m(CuS) and m(CuN) bands should occur with forms similar to those of m1 and m2 in Fig. 11(b). The doublet at 205, 224 cm1 in the copper complex is therefore assigned to the two m(CuX) modes expected for this compound (Table 7). The m(CN) frequencies for the thiocyanate complexes are given in Table 7. The frequency for [(SCN)Cu(pip)2](1|1) (2101 cm1) is very close to those for [(SCN)Ag(quin)2](1|1) (2101 cm1) and 1 [(SCN)Cu(py)2](1|1) (2099 cm ) [4]. In all of these compounds the thiocyanate ligand is bound in an M– SCN–M fashion. In [(NCS)Ag(pip)2](1|1), where the bonding is of the M–S–M type, m(CN) is significantly lower (2094 cm1). For comparison with the results discussed above for [XAg(pip)2](1|1) (X = Cl, SCN), and to further investigate the question of the m(AgN) frequencies, the far-IR spectra of [XAg(pip)]4 (X = Br, I) were recorded, and these are shown in Fig. 9. These complexes have the (hetero-)cubane structure [18]. The vibrational spectra of several series of cubane [XML]4 complexes have been discussed previously, and, although such complexes can display significant departures from ideal Td symmetry, it has been shown that the low frequency spectra can be discussed with reference to the behaviour of the ideal Td M4X4 core [30–33]. For such a unit, the symmetry types and activities of the funda-

mentals are 2A1(R) + 2E(R) + T1() + 3T2(IR, R). These can be approximately divided into contributions from M–X bond stretching m(MX) (A1 + E + T1 + 2T2) and cage deformation (A1 + E + T2). Thus, two IR-active m(AgX) modes, of T2 symmetry, are predicted for the [XAg(pip)]4 complexes, and the bands at 149, 86 cm1 (X = Br) and at 127, 72 cm1 (X = I) (Fig. 9) are assigned to these modes. The positions of these bands agree well with those of the other cubane [LMX]4 complexes studied previously [30–33]. Additional weaker bands are observed at 192 cm1 (X = Br) and 184 cm1 (X = I), and these are assigned to the m(AgN) modes involving the piperidine ligands. This agrees well with the assignment m(CuN) = 176 cm1 that has been made previously for [ICu(py)]4 [31]. The slight increase in m(MN) from the py to the pip complex, despite the increase in the mass from M = Cu to M = Ag, probably reflects the greater base strength of the pip ligand. The far-IR spectra of the two quin complexes [XAg(quin)](1|1) (X = Cl, Br) are shown in Fig. 10. These compounds show a
saddle polymeric structure (see above) that is considerably more complex than those observed for the [XAg(pip)2](1|1) (X = Cl, SCN) or [(SCN)Ag(quin)2](1|1) compounds discussed above. In view of the poor resolution of the spectra in the m(AgX) region below 200 cm1, a detailed

4320

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

Table 6 Core geometry of the ½Ag5 I6 ðquinÞ1j1  anion

Table 6 (continued)

Atoms

Parameter

Bond distances (A˚) Ag(1a)–I(1) Ag(1a)–I(4) Ag(1a)–I(5) Ag(1a)–N(1) Ag(1b)–I(2) Ag(1b)–I(3) Ag(1b)–I(6) Ag(1b)–N(5i) Ag(2)–I(1) Ag(2)–I(2) Ag(2)–I(5) Ag(2)–I(1ii) Ag(3)–I(1) Ag(3)–I(2) Ag(3)–I(3) Ag(3)–I(4) Ag(4)–I(3) Ag(4)–I(4) Ag(4)–I(4iii) Ag(4)–I(6iii) Ag(5)–I(2) Ag(5)–I(4) Ag(5)–I(5) Ag(5)–I(6)

2.872(5) 2.858(5) 2.800(5) 2.31(3) 2.794(6) 3.250(6) 3.222(6) 2.40(3) 2.898(3) 2.888(4) 2.817(3) 2.848(3) 2.875(4) 2.927(3) 2.749(4) 3.005(3) 2.755(3) 2.940(4) 2.965(4) 2.749(4) 2.966(3) 3.141(3) 2.817(4) 2.738(4)

Bond angles () I(1)–Ag(1a)–I(4) I(1)–Ag(1a)–I(5) I(1)–Ag(1a)–N(1) I(4)–Ag(1a)–I(5) I(4)–Ag(1a)–N(1) I(5)–Ag(1a)–N(1) I(2)–Ag(1b)–I(3) I(2)–Ag(1b)–I(6) I(2)–Ag(1b)–N(5i) I(3)–Ag(1b)–I(6) I(3)–Ag(1b)–N(5i) I(6)–Ag(1b)–N(5i) I(1)–Ag(2)–I(2) I(1)–Ag(2)–I(5) I(1)–Ag(2)–I(1ii) I(2)–Ag(2)–I(5) I(2)–Ag(2)–I(1ii) I(5)–Ag(2)–I(1ii) I(1)–Ag(3)–I(2) I(1)–Ag(3)–I(3) I(1)–Ag(3)–I(4) I(2)–Ag(3)–I(3) I(2)–Ag(3)–I(4) I(3)–Ag(3)–I(4) I(3)–Ag(4)–I(4) I(3)–Ag(4)–I(4iii) I(3)–Ag(4)–I(6iii) I(4)–Ag(4)–I(4iii) I(4)–Ag(4)–I(6iii) I(4iii)–Ag(4)–I(6iii) I(2)–Ag(5)–I(4) I(2)–Ag(5)–I(5) I(2)–Ag(5)–I(6) I(4)–Ag(5)–I(5) I(4)–Ag(5)–I(6) I(5)–Ag(5)–I(6) Ag(1a)–I(1)–Ag(2)

104.5(2) 115.5(1) 104.0(6) 106.5(2) 125.5(6) 101.5(6) 97.7(2) 98.9(2) 120.5(7) 138.3(1) 110.7(8) 93.0(7) 103.9(1) 114.18(8) 116.0(1) 102.4(1) 111.01(9) 108.4(1) 103.5(1) 120.1(1) 100.8(1) 106.9(1) 123.2(1) 103.6(1) 105.2(1) 106.1(1) 120.6(1) 111.5(1) 109.5(1) 104.0(1) 117.4(1) 100.5(1) 106.7(1) 99.0(1) 99.8(1) 134.6(1) 63.9(1)

Atoms

Parameter

Bond angles () Ag(1a)–I(1)–Ag(3) Ag(1a)–I(1)–Ag(2iii) Ag(2)–I(1)–Ag(3) Ag(2)–I(1)–Ag(2ii) Ag(3)–I(1)–Ag(2ii) Ag(1b)–I(2)–Ag(2) Ag(1b)–I(2)–Ag(3) Ag(1b)–I(2)–Ag(5) Ag(2)–I(2)–Ag(3) Ag(2)–I(2)–Ag(5) Ag(3)–I(2)–Ag(5) Ag(1b)–I(3)–Ag(3) Ag(1b)–I(3)–Ag(4) Ag(3)–I(3)–Ag(4) Ag(1a)–I(4)–Ag(3) Ag(1a)–I(4)–Ag(4) Ag(1a)–I(4)–Ag(5) Ag(1a)–I(4)–Ag(4iii) Ag(3)–I(4)–Ag(4) Ag(3)–I(4)–Ag(5) Ag(3)–I(4)–Ag(4iii) Ag(4)–I(4)–Ag(5) Ag(4)–I(4)–Ag(4iii) Ag(5)–I(4)–Ag(4iii) Ag(1a)–I(5)–Ag(2) Ag(1a)–I(5)–Ag(5) Ag(2)–I(5)–Ag(5) Ag(1b)–I(6)–Ag(5) Ag(1b)–I(6)–Ag(4iii) Ag(5)–I(6)–Ag(4iii)

69.0(1) 111.1(1) 69.59(9) 63.99(8) 125.60(9) 126.0(1) 62.9(1) 65.2(1) 69.02(9) 71.10(9) 60.91(8) 59.0(1) 81.0(1) 79.0(1) 67.4(1) 134.8(1) 68.1(1) 139.1(1) 72.12(9) 58.11(7) 102.45(9) 106.19(9) 68.5(1) 73.10(9) 65.8(1) 73.7(1) 74.34(9) 62.2(1) 80.0(1) 83.1(1)

Transformations of the asymmetric unit: i: x, y, 1+z; ii: 1  x,  y, 2  z; iii: 1  x, 1  y, 2  z.

analysis is not warranted. However, some degree of analysis is possible, and this is described here in order to demonstrate the relationship to the simpler systems discussed in more detail above. These structures show six independent Ag–X bonds, and the recently established relationship between m(AgX) and r(AgX) [28] yields m(AgX) ranges of 134–173 (mean = 157) cm1 (X = Cl) and 107–130 (mean = 121) cm1 (X = Br). Clearly, the six predicted bands are not resolved due to overlap, but broad bands are observed at 157 and 125 cm1 for X = Cl, Br, respectively. These are close to the mean m(AgX) values estimated above, and so are assigned to the m(AgX) modes in these compounds. The spectra also contain strong bands below 150 cm1 whose origin is probably the same (see above) as that of similar bands observed in the [XAg(pip)2](1|1) polymers (Fig. 8). The band at 154 cm1 in AgBr:quin (1:1) is too high to be assigned to m(AgBr) according to the bond-length criterion, but is at a reasonable position for a m(AgN) mode. The decrease in frequency relative to the m(AgN) mode at 184 cm1 in [BrAg(pip)]4 (Fig. 9) is readily explained on the basis of the lower base strength and greater mass of quin relative to pip.

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

4321

Fig. 7. The polymeric anion of the quinoline complex (a) in totality, projected normal to the axis and (b) the same (i) omitting Ag(1a) (and with appropriate quin assignment), and (ii) omitting Ag(1b) (and with appropriate quin assignment).

The far-IR spectra of [Ag(tmpp)2]2[Ag5I7L2] (L = py or 2mp) are shown in Fig. 12. The bands above 300 cm1 are due to the ligands, and those below 200 cm1 may be assigned to the m(AgI) modes of the anions (see below). The strong band at about 420 cm1 is due to the coordinated tmpp ligand. As discussed previously [9,34,35], the form of the spectrum in this region is characteristic of the type of complex involved. In the molecular adducts [(tmpp)MX] (M = Cu, Ag), three bands are seen in the region 405–450 cm1, whereas in the ionic species [M(tmpp)2]+ a single sharp band is observed in the region 422–428 cm1. The observation of a single band at about 420 cm1 in the spectra of the present compounds is therefore consistent with the ionic structure found from the crystal structure analysis in the case of the L = py complex, and with the postulate that the [Ag(tmpp)2]+ species is also present in the L = 2mp complex. The band at 409 cm1 in the L = py complex is due to the py ligand. The bands below 200 cm1 are similar in wavenumber to those assigned to the m(AgI) modes of other

AgI complexes or iodoargentate(I) anions. Thus, for the
cubane form of [(PPh3)4Ag4I4] m(AgI) = 82, 109 cm1; for the
step form of [(PPh3)4Ag4I4] m(AgI) = 93, 110, 130 cm1 [30]; for the [AgI3]2 ion in [PPh3Me]2[AgI3] m(AgI) = 133 cm1 [36]. In the py complex, there are three incompletely resolved bands at 91, 110, and 139 cm1. This is a simpler pattern than might have been expected on the basis of the relatively complex structure of the anion found in the crystal structure analysis. Thus, a total of 16 IR-active m(AgI) modes is predicted for a structure of C2 symmetry containing 16 AgI bonds. A smaller number of bands is predicted if we start from an idealized D5h [Ag5I7]2 structure containing twenty AgI bonds. This would give rise to four IR-active m(AgI) modes, two ð2E01 Þ involving the equatorial iodine atoms, and two ðE01 þ A002 Þ involving the apical iodine atoms. Distortion of the D5h structure to C2 symmetry, as is observed in the (py)2 adduct would result in a splitting of the E01 modes, giving a total of seven IR bands. This ignores the additional modes which would be activated in the descent from D5h to C2 symmetry.

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

86

149

190 155

4322

127 184

(b)

72

192

Absorbance

(a)

208

Absorbance

(a)

224 205

(b)

600

500

400

300

200

100

-1

Wavenumber/cm

(c)

Fig. 9. The far-IR spectra of [AgX(pip)]4 for (a) X = Br and (b) X = I. Bands due to the small amount of uncomplexed pip ligand that is present in the samples have been removed by subtraction. Bands assigned to m(AgX) and m(AgN) are labelled with their wavenumbers.

600

500

400

300

200

100

Wavenumber/cm-1

(a)

154

125

Absorbance

The observed spectrum of the (py)2 adduct is clearly simpler than this, and suggests the need for an alternative interpretation. A similar situation has previously been observed for iodocuprate(I) ions and their complexes with neutral ligands. For example, the IR spectrum of the [Cu2I4]2 ion in [NEt4]2[Cu2I4] consists of a strong, partially resolved doublet at 161, 173 cm1 [36], close to the value 163 cm1 which is observed for the single E 0 (CuI) mode of the trigonal planar [CuI3]2 ion [36]. The [Cu2I4]2 ion may be considered to consist of two trigonal CuI3 units which share a pair of iodine atoms, and an explanation of the unexpectedly simple IR spectrum of this ion is that this arises from the E 0 m(CuI) mode of the two identical CuI3 units in the structure. The splitting of this band into a doublet is due to the lowering of the local symmetry of each of the CuI3 units from D3h to C2v in the dinuclear complex. The situation in the case of the PPh3 adduct [Cu2I4(PPh3)2]2 appears to be similar in that the IR spectrum of this complex also consists of a strong, partially resolved doublet, the effect of the addition of the neutral ligand

157

Fig. 8. The far-IR spectra of [XM(pip)2](1|1) for (a) X = Cl, M = Ag, (b) X = SCN, M = Ag, and (c) X = SCN, M = Cu. Bands due to the small amount of uncomplexed pip ligand that is present in the samples have been removed by subtraction. Bands assigned to m(AgX) are labelled with their wavenumbers.

(b)

600

500

400

300

200

100

Wavenumber/cm-1 Fig. 10. The far-IR spectra of [XAg(quin)](1|1) for (a) X = Cl and (b) X = Br. Bands assigned to m(AgX) and m(AgN) are labelled with their wavenumbers.

m(AgN)a

[ClAg(pip)2](1|1) [(CNS)Ag(pip)2](1|1) [(SCN)Cu(pip)2](1|1) [(SCN)Ag(quin)2](1|1) [BrAg(pip)]4 [IAg(pip)]4 [ClAg(quin)](1|1) [BrAg(quin)](1|1)

155, 190 208 224, 205

b

91

b

ν1

M X M X

ν2

ν2 + - + M X M X (a)

ν3

M

M X

M

X

141 120 91

M X M X

357

ν1

(a)

422

154

Involving the M–amine bonds. Region obscured by other bands in the spectrum.

139

b

192 184

360

b

86, 149 72, 127 157 125

482

b

2094 2101 2100

b

Absorbance

a

b

m(CN)

110

m(MX)

409

Compound

483

Table 7 Assignments (wavenumbers/cm1) of the m(MX) and m(MN) modes in the IR spectra

4323

425

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

M X

X

(b)

+ + M - M X X

500

400

300

200

Wavenumber/cm

(b)

100

-1

Fig. 11. The vibrational modes of single-strand AgX polymer chains for (a) linear and (b) non-linear bridging X. The ‘‘+’’ and ‘‘’’ symbols refer, respectively, to atomic displacements above and below the plane of the page.

Fig. 12. Far-IR spectra of (a) [Ag(tmpp)2]2[Ag5I7(py)2] and (b) [Ag(tmpp)2]2[Ag5I7(2mp)2].

being simply to shift the doublet to lower wavenumber; the absorption peaks occur at 113, 126 cm1 in this case [37]. An extension of this approach to the present systems is as follows: the idealized D5h [Ag5I7]2 ion may be considered to consist of five tetrahedral AgI4 units which share two pairs of iodine atoms (one equatorial pair and one apical pair). The resulting IR spectrum would then be based on the single T2 m(AgI) mode for each of the five identical AgI4 units in the structure, and this would be split into a triplet due to the fact that the local symmetry of each of these units is lowered from Td to C2v in the pentanuclear complex. This would account for the presence of a partially resolved triplet in the m(AgI) region in the IR spectrum, and this agrees well with the forms of the spectra observed below 200 cm1 for both of the [Ag5I7L2]2 complexes (Fig. 12). The presence of the py or 2mp ligands might be expected to complicate the spectrum further, but reference to the iodocuprate examples discussed above indicates that the only effect of addition of a neutral ligand is an overall downward shift in their band positions, without any change in the splitting pattern. The occurrence of an incompletely resolved triplet in the m(AgI) region over

a relatively narrow frequency range in the IR spectra of the present complexes can thus be explained. Under higher resolution, a more complex pattern would be expected, and there is some evidence of this in the spectrum of the 2mp complex. However, the spectra of the two complexes are quite similar, supporting the view that these compounds have analogous structures. 3.3. Coda A persistent side-product of the reaction of piperidine with atmospheric carbon dioxide, piperidinium 1-piperidinecarbamate monohydrate, crystallizes in a centrosymmetric triclinic array with one formula unit comprising the asymmetric unit of the structure; all hydrogen atoms were located in the refinement process and, although hydrogen-bonding undoubtedly contributes to the stability of the crystal as the monohydrate, the hydrogen distribution is clearly as the formula implies, each hydrogen atom having the above clearly identifiable parent entity; it is not isomorphous with either of the forms of its sulfur analogue [8,9] (not noted in [38] which records a contemporaneous

4324

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

Fig. 13. (a) and (b) Unit cell projections of (pipH)((pip-H)CO2) Æ H2O down b and c. Hydrogen bonding (i.e., OH2, NH2) hydrogen atoms only are included, with the linkages forming the double-stranded array along c shown.

study, harmonious with the present), these being anhydrous. The hydrogen-bonding scheme is straightforward: the pair of water molecule hydrogen atoms serves to bridge a pair of independent oxygen atoms from anions in successive unit cells along c: H(11)


O(211A) 1.85(5); H(12)


O(211B) (x, y, 1 + ˚ , O–H


O being 163(5), 175(3), respecz), 2.03(4) A tively. The strands so created are linked in parallel pairs with inversion related carboxylate groups from adjacent strands linked by the two (NH2) hydrogen atoms of the cation (H(11a)


O(211A), 1.76(3); ˚ ), angles at H(11e)


O(211B) ðx; y ; 1  zÞ, 1.70(3) A the hydrogen atoms N–H


O being 175(2), 172(2), respectively. The resultant columnar array is shown in Fig. 13. Cationic and anionic pip geometries differ, the conjugated attachment of the nitrogen to the CO2 moiety in

the latter resulting in significant changes in associated N(n1)–C(n2,6) distances and the C(n2)–N(n1)–C(n6) angle (Table 8), the remaining bond lengths and angle in the ring being unperturbed, while torsion angles around the ring and, in particular at the nitrogen, perhaps surprisingly show no significant differences. The NCO2 array is substantially planar with significant double bond character in the N–C distance, in turn impinging on the adjacent N–C distances and C–N–C angle within the ring system as mentioned above, and on the CO2  geometry, O–C–O being enlarged above the trigo˚ is enlarged somewhat above nal norm. N–C 1.369(3) A the value found in dithiocarbamate analogues, those found in the piperidinium analogue (both forms) rang˚ ing between 1.333(8)–1.360(8); Æ æ (six values) 1.34(1) A while S–C–S, perhaps surprisingly, is smaller (119.1(4)–120.1(4); Æ æ, 119.7(4)).

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326 Table 8 Non-hydrogen geometries (pipH)+((pip-H)CO2) Æ H2O Atoms

Parameter

Bond distances (A˚) N(n1)–C(n2) N(n1)–C(n6) C(n2)–C(n3) C(n5)–C(n6) C(n3)–C(n4) C(n5)–C(n4) N(21)–C(211) C(211)–O(211A) C(211)–O(211B)

1.481(4), 1.447(4) 1.481(3), 1.443(3) 1.509(4), 1.507(4) 1.506(4), 1.505(5) 1.504(5), 1.496(4) 1.486(5), 1.509(4) –, 1.369(3) –, 1.260(3) –, 1.252(3)

Bond angles () C(n2)–N(n1)–C(n6) N(n1)–C(n2)–C(n3) N(n1)–C(n6)–C(n5) C(n2)–C(n3)–C(n4) C(n6)–C(n5)–C(n4) C(n3)–C(n4)–C(n5) C(211)–N(21)–C(22) C(211)–N(21)–C(26) N(21)–C(211)–O(211A) N(21)–C(211)–O(211B) O(211A)–C(211)–O(211B)

112.7(2), 114.1(2) 110.2(3), 110.8(2) 110.2(2), 111.1(2) 111.7(2), 112.3(2) 111.5(3), 111.3(3) 110.9(3), 110.4(2) –, 121.9(2) –, 122.2(2) –, 118.1(2) –, 118.2(2) –, 123.6(2)

Torsion angles () (atoms denoted by number only, N italicized) n5–n4–n3–n2 54.7(4), 53.0(4) n4–n3–n2–n1 54.4(4), 53.2(3) n3–n2–n1–n6 56.0(3), 55.1(3) n3–n2–n1–n11 –, 139.8(2) n2–n1–n11–O(n11A) –, 173.5(2) n2–n1–n11–O(n11B) –, 8.0(3) n3–n4–n5–n6 55.4(3), 53.3(3) n4–n5–n6–n1 56.0(3), 54.5(3) n5–n6–n1–n2 56.8(3), 56.1(3) n5–n6–n1–n11 –, 138.8(3) n6–n1–n11–O(n11A) –, 9.6(3) n6–n1–n11–O(n11B) –, 171.9(2) The two values in each entry are for n = 1, 2 (cation, anion), respec˚ , respectively, from the tively. C(22, 26) deviate by 0.147(4), 0.181(4) A anion NCO2 plane (v2 = 14.8).

4. Conclusions The consolidation, with fresh examples, of a number of (oligo-)/polymeric silver(I)/(pseudo-) halide structural types, has provided a platform for a similar consolidation of our understanding of their vibrational spectroscopy. The ready crystallization of a number of complex anions of this type with [Ag(tmpp)2]+ cations has led to a recognition of common motivic dispositions of the latter, both internally and in respect of their crystallization in twodimensional sheets, the P–Ag–P cation axes disposed normal to these, in a well-defined manner with possibilities for some degree of control of crystal
architecture.

References [1] P.C. Healy, N.K. Mills, A.H. White, J. Chem. Soc., Dalton Trans. (1985) 111.

4325

[2] P.C. Healy, J.D. Kildea, A.H. White, Aust. J. Chem. 41 (1988) 417. [3] N.K. Mills, A.H. White, J. Chem. Soc., Dalton Trans. (1984) 229. [4] H. Krautscheid, N. Emig, N. Klaassen, P. Seringer, J. Chem. Soc., Dalton Trans. (1998) 3071. [5] N.K. Mills, A.H. White, J. Chem. Soc., Dalton Trans. (1984) 225. [6] L.-J. Baker, G.A. Bowmaker, D. Camp, Effendy, P.C. Healy, H. Schmidbaur, O. Steigelmann, A.H. White, Inorg. Chem. 31 (1992) 3656. [7] L.-J. Baker, G.A. Bowmaker, Effendy, B.W. Skelton, A.H. White, Aust. J. Chem. 45 (1992) 1909. [8] A. Wahlberg, Acta Crystallogr., Sect. B 36 (1980) 2099 (monoclinic (
b) form). [9] A. Wahlberg, Acta Crystallogr., Sect. B 37 (1981) 1240 (orthorhombic (
a) form). [10] G.A. Bowmaker, Effendy, K.C. Lim, B.W. Skelton, D. Sukarianingsih, A.H. White, Inorg. Chim. Acta 358 (2005) 4342. [11] For example, U. Zachwieja, H. Jacobs, Z. Krist. 201 (1992) 207 ([Ag(NH3)2]2(SO4)) and references therein to the nitrate and perchlorate. [12] Note also the determination of [Ag(NH3)3](NO3) recorded in U. Zachwieja, H. Jacobs, Z. Anorg. Allg. Chem. 571 (1989) 37. [13] J.C. Dyason, L.M. Engelhardt, P.C. Healy, C. Pakawatchai, A.H. White, Inorg. Chem. 24 (1985) 1950. [14] N.P. Rath, E.M. Holt, K. Tanimura, J. Chem. Soc., Dalton Trans. (1986) 2303. [15] P.C. Healy, C. Pakawatchai, R.I. Papasergio, V.A. Patrick, A.H. White, Inorg. Chem. 23 (1984) 3769. [16] P.C. Healy, B.W. Skelton, A.F. Waters, A.H. White, Aust. J. Chem. 49 (1991) 1049. [17] P.C. Healy, N.K. Mills, A.H. White, Aust. J. Chem. 36 (1983) 1851. [18] L.M. Engelhardt, S. Gotsis, P.C. Healy, J.D. Kildea, B.W. Skelton, A.H. White, Aust. J. Chem. 42 (1989) 149. [19] G.B. Ansell, J. Chem Soc., Perkin Trans. 2 (1976) 104. [20] P.C. Healy, C. Pakawatchai, C.L. Raston, W.B. Skelton, A.H. White, J. Chem. Soc., Dalton Trans. (1983) 1905. [21] G.A. Bowmaker, Effendy, J.C. Reid, C.E.F. Rickard, B.W. Skelton, A.H. White, J. Chem. Soc., Dalton Trans. (1998) 2139. [22] E.C. Alyea, G. Ferguson, A. Somogyvari, Inorg. Chem. 21 (1982) 1369. [23] C.W. Liu, H. Pan, J.P. Fackler Jr., G. Wu, R.E. Wasylishen, M. Shang, J. Chem. Soc., Dalton Trans. (1995) 3691. [24] H. Hartl, F. Mahdjour-Hassan-Abadi, Angew. Chem., Int. Ed. Engl. 23 (1984) 378. [25] S. Andersson, S. Jagner, J. Crystallogr. Spectrosc. Res. 18 (1988) 591, a number of similar but less-closely related discrete species ([Cu4I6]2, [Cu4I7]3) have recently been reported in [26]. [26] J.A. Rusanova, K.V. Domasevitch, O.Yu. Vassilyeva, V.N. Kokozay, E.B. Rusanov, S.G. Nedelko, O.V. Chukova, B. Ahrens, P.R. Raithby, J. Chem. Soc., Dalton Trans. (2000) 2175. [27] G.A. Bowmaker, B.J. Kennedy, J.C. Reid, Inorg. Chem. 37 (1998) 3968. [28] G.A. Bowmaker, Effendy, J.D. Kildea, A.H. White, Aust. J. Chem. 50 (1997) 577. [29] G.A. Bowmaker, Effendy, P.J. Harvey, P.C. Healy, B.W. Skelton, A.H. White, J. Chem. Soc., Dalton Trans. (1996) 2449. [30] B.-K. Teo, D.M. Barnes, Inorg. Nucl. Chem. Lett. 12 (1976) 681. [31] G.A. Bowmaker, R.J. Knappstein, S.F. Tham, Aust. J. Chem. 31 (1978) 2137. [32] G.A. Bowmaker, P.C. Healy, Spectrochim. Acta A 44 (1988) 115. [33] G.A. Bowmaker, Effendy, R.D. Hart, J.D. Kildea, A.H. White, Aust. J. Chem. 50 (1997) 653.

4326

G.A. Bowmaker et al. / Inorganica Chimica Acta 358 (2005) 4307–4326

[34] G.A. Bowmaker, J.D. Cotton, P.C. Healy, J.D. Kildea, S. bin Silong, B.W. Skelton, A.H. White, Inorg. Chem. 28 (1989) 1462. [35] L.-J. Baker, G.A. Bowmaker, R.D. Hart, P.J. Harvey, P.C. Healy, A.H. White, Inorg. Chem. 33 (1994) 3925.

[36] G.A. Bowmaker, G.R. Clark, D.A. Rogers, A. Camus, N. Marsich, J. Chem. Soc., Dalton Trans. (1984) 37. [37] G.A. Bowmaker, Wang Jirong, R.D. Hart, A.H. White, P.C. Healy, J. Chem. Soc., Dalton Trans. (1992) 787. [38] H. Jiang, I. Novak, J. Mol. Struct. 645 (2003) 177.