Silver(I) acetylides stabilized by η2-alkynes: Synthesis, reaction chemistry and solid state structures

Inorganica Chimica Acta 373 (2011) 93–99

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Silver(I) acetylides stabilized by g2-alkynes: Synthesis, reaction chemistry and solid state structures Heinrich Lang ⇑, Noelia Mansilla, Ron Claus, Tobias Rüffer, Gerd Rheinwald Technische Universität Chemnitz, Fakultät für Naturwissenschaften, Institut für Chemie, Lehrstuhl für Anorganische Chemie, Straße der Nationen 62, 09111 Chemnitz, Germany

a r t i c l e

i n f o

Article history: Received 17 February 2011 Received in revised form 23 March 2011 Accepted 28 March 2011 Available online 3 April 2011 Keywords: Organometallic p-tweezer Acetylide Coordination polymer Titanium Silver

a b s t r a c t Individual synthetic routes to heterobimetallic Ti(IV)–Ag(I) acetylides of type {[Ti](l-r,pC„CR1)2}AgC„CR2 ([Ti] = (g5-C5H4SiMe3)2Ti: R1 = SiMe3: 6, R2 = SiMe3; 7, R2 = Ph. R1 = tBu: 8, R2 = SiMe3; 9, R2 = Ph. [Ti] = (g5-C5H5)2Ti): 10, R1 = tBu, R2 = SiMe3) including (i) the reaction of {[Ti](l-r, pC„CR1)2}AgNO3 ([Ti] = (g5-C5H4SiMe3)2Ti): 1, R1 = SiMe3; 2, R1 = tBu. [Ti] = (g5-C5H5)2Ti: 3, R1 = tBu) with LiC„CR2 (4, R2 = SiMe3; 5, R2 = Ph) and (ii) treatment of [Ti](C„CSiMe3)2 ([Ti] = (g5-C5H4SiMe3)2Ti) (11) with [AgC„CR2] (12, R2 = SiMe3; 13, R2 = Ph) are described. The reactions of 1–3 with 4 or 5 appeared to be sensitive towards stoichiometry because an excess of 4 or 5 resulted in the formation of [(Ag(C„CR2)2)Li(OEt2)]n (14) and [Ti](C„CR1)2. Coordination polymer 14 is also accessible, when, for example, [AgC„CSiMe3] (12) is treated with 1 eq. of LiC„CSiMe3 (4) in diethyl ether. The titanium(IV)–silver(I) acetylides 6–10 are stable in the dark and at low temperature, while on exposure to light and on heating they decompose to give R2C„C–C„CR2 together with [Ti](C„CR1)2 and elemental silver. Complexes 6–10 contain a mono-nuclear AgC„CR2 entity stabilized by the chelate-bonded organometallic p-tweezer molecule [Ti](C„CSiMe3)2, which was evinced by structure determination of 7 in the solid state. In 14 linear [Me3SiC„C–Ag–C„CSiMe3] units are connected by [Li(OEt2)]+ building blocks forming a coordination polymer. Ó 2011 Elsevier B.V. All rights reserved.

1. Introduction

2. Results and discussion

Organo-silver(I) compounds [AgR] (R = organic group) are highly reactive molecules as the inorganic silver(I) salts [AgX] (X = halide, pseudo-halide, amide, thiolate, etc.) are generally encountered to be polynuclear existing either as discrete aggregates or as polymers [1]. Conversion of these species into neutral structural units with a lower nuclearity can be achieved by using bulky groups R [2] or Lewis-bases [3]. So far reported silver(I) acetylides possess a oligomeric or polymeric structure [4] but to the best of our knowledge no structurally characterized monomeric silver(I) acetylides has been described so far. Recently, we reported about the successful use of the organometallic 1,4-diyne [Ti](C„CSiMe3)2 ([Ti] = (g5-C5H5)2Ti, (g5-C5H4SiMe3)2Ti,. . .) as organometallic p-tweezer molecule [5] to stabilize mononuclear metal acetylides [MC„CR] (M = Cu, Au; R = SiMe3, Ph) affording heterobimetallic early-late complexes of type {[Ti](l-r,pC„CSiMe3)2}MC„CR [6]. We herein report on the synthesis, reaction chemistry, and properties of mononuclear silver(I) acetylides stabilized by the bis(alkynyl)titanocene chelating unit.

2.1. Synthesis and reaction behavior

⇑ Corresponding author. Tel.: +49 (0)371 531 21210; fax: +49 (0)371 531 21219. E-mail address: [email protected] (H. Lang). 0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2011.03.069

For the preparation of the alkyne-stabilized silver(I) acetylides 6–10 (Scheme 1, Table 1) two synthesis methodologies have been developed including (i) metathesis of {[Ti](l-r,p-C„CR1)2}AgNO3 ([Ti] = (g5-C5H4SiMe3)2Ti: 1, R1 = SiMe3; 2, R1 = tBu. [Ti] = (g5-C5H5)2Ti: 3, R1 = tBu) with LiC„CR2 (4, R2 = SiMe3; 5, R2 = Ph), and (ii) deaggregation of 1/n[AgC„CR2]n (12, R2 = SiMe3; 13, R2 = Ph) upon addition of the organometallic p-tweezer molecule [Ti](C„CSiMe3)2 ([Ti] = (g5-C5H4SiMe3)2Ti) (11). In this respect, silver(I) nitrates 1–3 were reacted with stoichiometric amounts of in situ prepared lithium acetylides LiC„CR2 (4, 5) at 70 to 0 °C in diethyl ether to produce yellow reaction solutions containing the Ti(IV)–Ag(I) organometallic compounds {[Ti](l - r, p -C„CR 1 ) 2 }AgC„CR 2 ([Ti] = ( g5 -C5 H 4 SiMe 3 )2 Ti: R1 = SiMe3: 6, R2 = SiMe3; 7, R2 = Ph. R1 = tBu: 8, R2 = SiMe3; 9, R2 = Ph. [Ti] = (g5-C5H5)2Ti): 10, R1 = tBu, R2 = SiMe3) (Scheme 1, route (i)). After appropriate work-up, these heterobimetallic transition metal complexes could be isolated as yellow to orange colored solids in yields between 50% and 80% (Table 1, Section 4). An alternative synthesis methodology for the preparation of 6 and 7 involves the treatment of [Ti](C„CSiMe3)2 (11) with 1/n[AgC„CR2]n in a

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H. Lang et al. / Inorganica Chimica Acta 373 (2011) 93–99

R1 C C [Ti] AgNO 3 C C R1 1-3

(i) Li C CR

2

(4, 5)

- LiNO3

R1 C C [Ti] Ag C C R2 C C R1 6 - 10

2

(ii) AgC CR (12, 13)

[Ti]

C C

C C

R1

R1

11

Scheme 1. Synthesis of alkyne-stabilized mononuclear silver(I) acetylides 6–10.

heating toluene solutions containing 6–10 to 80 °C elimination of the appropriate AgC„CR2 building block took place, which by cleavage of the silver-carbon r-bond gave the corresponding 1,3diynes R2C„C–C„CR2 (R2 = SiMe3, Ph) and elemental silver (Scheme 3). An analogous behavior was found for related titanium(IV)–copper(I) and titanium(IV)–gold(I) acetylides [5–8].

Table 1 Synthesis of 6–10. Compounds 6 7 8 9 10 a

[Ti] 5

(g -C5H4SiMe3)2Ti (g5-C5H4SiMe3)2Ti (g5-C5H4SiMe3)2Ti (g5-C5H4SiMe3)2Ti (g5-C5H5)2Ti

R1

R2

Yielda

SiMe3 SiMe3 Bu t Bu t Bu

SiMe3 C6H5 SiMe3 C6H5 SiMe3

80 75 70 73 53

t

2.2. Characterization

Based on 1–3.

The characterization of 6–10 and 14 is based on elemental analysis and spectroscopic studies (IR, 1H, 13C{1H} NMR). The structures of 7 and 14 in the solid state were determined by single X-ray structure analysis. The presence of two C„C stretching frequencies in the IR spectra of 6–10 indicates that besides the mono-nuclear silver acetylide unit AgC„CR2 also g2-coordinated TiC„CR1 alkynes are present, whereby the latter vibrations appear at lower wavenumbers (Section 4). As compared with the free organometallic p-tweezer [Ti](C„CR1)2, [5,8] the mC„C absorptions in 6–10 are shifted to lower frequencies as it is generally observed for the g2-coordination of alkynes to MLn fragments (MLn = transition metal fragment) in which the alkynes act as 2-electron donor ligands [5,9]. The obtained IR-spectroscopic data for 6–10 demonstrate the influence on the change from a weaker to a stronger r-donor group on the g1-bonded acetylide ligands at silver(I), which finally leads to a carbon-carbon triple bond weakening of the g2-C„C units. Thus, in {[Ti](l-r,p-C„CR1)2}AgC„CSiMe3 ([Ti] = (g5-C5H4SiMe3)2Ti; 6, R1 = SiMe3: mC„C = 1941; 8, R1 = tBu: mC„C = 1938 cm1) the former band appears at somewhat lower wavenumbers than in the corresponding derivatives containing r-bonded AgC„CPh units (7, R1 = SiMe3: mC„C = 1944; 9, R1 = tBu: mC„C = 1942 cm1). This behavior can be extended to previously reported heterodinuclear Ti(IV)–M(I) complexes (M = Cu, Au) containing g2-alkyne-stabilized copper(I) and gold(I) acetylides [5–7]. These data show that in the alkyne-to-metal interaction the g2-coordinated C„C triple bonds are weakened more in the case of gold(I) than for copper(I) and silver(I) (e.g., {[Ti](l-r,p-C„CSiMe3)2}MC„CSiMe3: M = Au, mC„C = 1848; M = Cu, mC„C = 1896 ; M = Ag, mC„C = 1941 cm1) [5–7]. Consequently, the back-donation of filled metal orbitals into empty alkyne p⁄ orbitals is stronger in the series gold > copper > silver [5–7]. Likewise, complexes 6–10 present a further mC„C band at 2032 (6), 2017 (7), 2070 (8), 2022 (9) and 2015 cm1 (10), a region typical for metal acetylides, i.e., [AgC„CR] [5,1].

1:1 molar ratio in diethyl ether as solvent (Scheme 1, route (ii)). However, this synthesis procedure has, when compared with the metathesis route, proven to be less convenient, due to lower yields achieved (Section 4). Heterobimetallic, 6–10 are solid materials soluble in most common organic solvents and can be isolated in analytical pure form, especially using the metathesis process. Nevertheless, several aspects concerning their isolation must be considered: thermal stability, light sensitivity, and stoichiometry. Enhancement of thermal stability is observed for the alkyne-stabilized silver(I) acetylides 6–10 in relation to the parent polynuclear aggregates [AgC„CR2]n. Likewise, when 6–10 are exposed to light, decomposition of these species occurs during hours by precipitation of silver(0) and formation of the appropriate 1,3-diynes R2C„C– C„CR2. Consequently, it is advised to handle 6–10 in the absence of light during all purification steps applied. In addition, the temperature during work-up should best be kept below 0 °C and storing of the appropriate complex at low temperature is recommended, otherwise decomposition takes place (vide supra). Important observations have also been made in relation to the reaction stoichiometry. The presence of unreacted LiC„CR2 (4, 5) in the reaction mixture, even in small amounts, induces the dissociation of the organometallic chelating unit [Ti](C„CR1)2 from silver(I) leading to coordination polymer [(Ag(C„CR2)2)Li(OEt2)]n (14) together with the free organometallic p-tweezer [Ti](C„CR1)2. To prove evidence, we reacted exemplarily 6 with 4 in diethyl ether in the ratio of 1:2. Solely the silver acetylide 14 was obtained together with (g5-C5H4SiMe3)2Ti(C„CSiMe3)2 (11) in 70% isolated yield (Scheme 2). Coordination polymer 14 is independently accessible, when [AgC„CSiMe3] (12) is treated with 1 eq. of LiC„CSiMe3 (4) in diethyl ether as solvent (Scheme 2). Furthermore, the thermal decomposition behavior of heterobimetallics 6–10 was investigated under controlled conditions. Upon

SiMe 3

R1 C C Ag C CSiMe3 [Ti] C C 1 R 6

Ag

Li C CSiMe 3 ( 4) Et 2 O

- 11

SiMe 3 OEt 2 Ag Li Me3 Si

OEt 2 Li

Li C CSiMe 3 (4 )

Me3 Si 14

Scheme 2. Synthesis of 14 from 4 and 6 as well as 4 and 12.

Et 2O

Ag C CSiMe 3

12

H. Lang et al. / Inorganica Chimica Acta 373 (2011) 93–99

R1 C C [Ti] Ag C C R 2 C C R1 6 - 10

ΔT toluene

[Ti]

C C

C

R1 +

C

95

R 2 C C C C R 2 + Ag 0

R1

Scheme 3. Decomposition behavior of 6–10.

Since well-resolved signals for all organic groups could be recorded, the assignment in the 1H and 13C{1H} NMR spectra of 6– 10 could be implemented unambiguously (Section 4). The most striking feature about the 1H NMR spectra is the appearance of either two (7) or one broad signal (8) for the ring protons of the C5H4SiMe3 units in complexes 7 and 8. The characteristic AA0 XX0 resonance pattern typical for C5H4R cyclopentadienyls (R = organic group) is only recorded for complexes 6 and 9 (Section 4). In agreement with the formulation of 6–10 as early-late Ti(IV)– Ag(I) organometallic p-tweezer complexes in which both alkynyl ligands of the bis(alkynyl)titanocene fragment are g2-coordinated to a mononuclear AgC„CR2 moiety is the observation of resonance signals corresponding to the Ca and Cb carbon atoms of the [Ti] (Ca„CbR1)2 and AgCa„CbR2 building blocks in the 13C{1H} NMR spectra (Section 4). The Ca and Cb atoms of the bis(alkynyl)titanocene chelating unit are found between 129 and 170 ppm (6, 165.5, 135.0; 7, 165.0, 134.9; 8, 169.0, 131.6; 9, 170.2, 131.8; 10, 151.3, 129.4 ppm), while for the r-bonded silver acetylides AgCa„CbR2 the appropriate carbons are somewhat shifted to higher field and are observed between 111 and 123 ppm) (Section 4). Another remarkable feature of the 13C{1H} NMR spectra of 6–10 is the coupling of the acetylide carbon atoms of the C„CR1 ligands with the 107 Ag and 109Ag isotopes (for example, 6: R1 = SiMe3, 1JCAg = 9.7 Hz (Ca), 1JCAg = 4.3 Hz (Cb); 7: 1JCAg = 10.8 Hz (Ca), 1JCAg = 3.0 Hz (Cb)) thus indicating that relative strong silver–carbon acetylide bonds exist. This shows that the silver(I) acetylide moiety is well stabilized by the organometallic bis(alkynyl)titanium p-tweezer system [10].

2.3. X-ray diffraction study The molecular structure of complexes 7 and 14 in the solid state has been verified by X-ray diffraction analysis (Figs. 1 and 2). Most significant bond lengths (Å) and angles (°) are listed in the caption of the appropriate Figure, while crystallographic parameters are presented in Table 2 (Section 4). The silver atom Ag1 in 7 is tri-coordinated by the chelating organometallic 1,4-diyne Ti(C„CSiMe3)2 and the r-bonded acetylide PhC„C. The structure analysis of 7 reveals the characteristic features of g2-alkyne stabilized group-11 metal species of general type {[Ti](l-r,p-C„CR)2}MX ([Ti] = (g5-C5H5)2Ti, (g5-C5H4SiMe3)2Ti; M = Cu, Ag, Au; X = mono-dentate inorganic, organic or organometallic ligand) with M in a planar surrounding [5–7,11– 13]. For a more specific discussion of tendencies concerning heterobimetallic organometallic p-tweezer complexes see reference [5]. Upon g2-coordination of the titanium alkynyl ligands to the low-valent AgC„CPh entity a bond lengthening of the C„C triple bonds from 1.214(6) and 1.203(9) [11] in the non-coordinated tweezer molecule [5,12] to 1.238(3) and 1.234(3) Å in 7 is observed. The bite angle C1–Ti1–C6 is considerably reduced (93.25(9)°) compared to the analogous angle in [Ti](C„CSiMe3)2 (102.8(2)°) [5,8a]. The latter effects are enhanced in the series Cu < Ag < Au for complexes {[Ti](l-r,p-C„CSiMe3)2}MC„CR2 (M = Cu, R2 = SiMe3; M = Ag, R2 = Ph (7); M = Au, R2 = SiMe3). Thus, bite angles of 88.54(14), 93.25(9)° and 95.5(4)° are encountered for the respective Cu(I), Ag(I) and Au(I) species. Another effect of the tweezer-like coordination is the characteristic trans-bending of

Fig. 1. The molecular structure (ORTEP diagram, 50% probability level) of 7 with the atom numbering scheme. Hydrogen atoms are omitted for clarity. Selected bond distances (Å) and bond angles (°): Ti1–C1 2.119(2); Ti1–C6 2.111(2); C1–C2, 1.238(3); C6–C7, 1.234(3); C2–Si1, 1.855(2); C7–Si2, 1.857(3); Ag1–C1, 2.295(2); Ag1–C2, 2.395(2); Ag1– C6, 2.317(2); Ag1–C7, 2.392(2); Ag1–C27, 2.083(3); C27–C28, 1.207(4); C1–Ti1–C6, 93.25(9); Ti1–C1–C2, 170.3(2); C1–C2–Si1, 168.1(2); Ti1–C6–C7, 168.9(2); C6–C7–Si2, 169.4(2); Ag1–C27–C28, 177.4(3); C27–C28–C29, 179.4(3). Molecule 7 crystallized in the monoclinic space group C2.

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Fig. 2. ORTEP diagram (25% probability level) of a selected part of the 1D coordination polymer 14 with the atom numbering scheme. Hydrogen and disordered atoms are omitted for clarity. Selected bond distances (Å) and bond angles (°): Ag1–C1: 2.05(2). Ag1–C1C: 2.05(2). C1–C2:1.22(3). Li1–C1: 2.26(5). Li1–C2: 2.46(5). Li1–O1: 1.94(6). Ag1–Li1: 3.193(17) C1–Ag1–C1C: 173(4)°. Li1–Ag1–Li1C: 140.9(17)°. Ag1–C1–C2: 173(5)°. C1–C2–Si1: 172.0(17)°. Symmetry operations used to generate equivalent atoms. A: x, y, z  1. B: x + 2, y, z + 1. C: x + 2, y, z + 2. D: x, y, z + 1. E: 1  x, y, 2  z.

Table 2 Crystal and intensity collection data for 7 and 14.

Empirical formula Formula weight Temperature (K) Wavelenght (Å) Crystal system Space group a (Å) b (Å) c (Å) b (°) V (Å3) qcalc (g cm3) F(0 0 0) Crystal dimensions (mm3) Z Maximum, minimum transmission Absorption coefficient (l, mm-1) Scan range (°)

7  CH2Cl2

14

C35H51AgCl2Si4Ti 810.79 173(2) 0.71073 monoclinic P21/c 20.6348(6) 12.2482(3) 16.7342(4) 105.1120(10) 4083.13(18) 1.319 1680 0.6  0.3  0.25 4 0.724838, 0.528890 0.945 1.95–26.00

C14H28AgSi2OLi 383.35 243(2) 0.71073 monoclinic C2 22.0004(13) 7.5957(5) 6.0174(2) 99.266(2) 992.44(9) 1.283 396 0.2  0.1  0.1 2 0.917171, 0.690590 1.127 1.88–26.00

25  h  14 15  k  15 20  l  20 23575 8029 0.0341

27  h  14 9  k  4 7  l  7 2480 1119 0.0299

8029/7/388 1.024 0.0308, 0.0703 0.0452, 0.0747 0.704, 0.590

1119/91/98 1.042 0.0336, 0.0777 0.0390, 0.0808 0.495, 0.506

Index ranges

Total reflections Unique reflections R(int) Data/restraints/parameters Meter Goodness-of-fit on F2 R1,a wR2a [I  2r(I)] R1,a wR2a (all data) Maximum, minimum peak in final Fourier map (e Å3)

Column 1: Abs. structure param. [15]; Column 2: - ; Column 3: 0.0(3). a R1 = [R(||Fo|  |Fc|)/R|Fo|); wR2 = [R(w(Fo2  Fc2)2)/R(wFo4)]1/2. S = [Rw(Fo2  Fc2)2]/(n  p)1/2. n = number of reflections, p = parameters used.

the Ti–C„C–Si units as result of the p-bonding of the bis(alkynyl)titanoceneentity to silver(I) [5–7]. The carbon–carbon triple

bond of the AgC„CPh building block (C27–C28) with 1.207(3) Å appears in the expected range [1]. The silveracetylide 14 crystallizes in the monoclinic space group P21/c. Arrangements of polymeric 14 in the crystal lattice are illustrated in Fig. 3. Polymeric 14 can be understood as novel lithium salt of a silver(I) bis(acetylide), being formally composed of the anionic [Ag(C„CSiMe3)2] and cationic [Li(OEt2)]+ fragments. So far, two structurally closely related polymeric complexes have been described, setup by anionic [Ag(C„CR)2] (R = SiMe3 (15), Ph (16)) and cationic [Ag(PMe3)2]+ moieties [4]. The coordination around the [Ag(C„CR)2] silver center of 16 is precisely linear, whereas that of 15 and 14 deviates from linearity. With a C2 rotational axis going through Ag1 the C1–Ag1–C1C bond angle of 14 amounts to 173(4)° compared to 15 with 177.5° [4]. The Ag–C distances of the r-bonded acetylide ligands of 14 are with 2.05(2) Å in the same range as those ones observed for 15 (2.035(8) Å and 2.065(8) Å) and 16 (2.040(13) Å) [4]. In contrast to 15 and 16, where [Ag(PMe3)2]+ fragments acting as bridging units by reciprocal contacts to the C„C triple bonds of [Ag(C„CR)2] units, in 14 the cationic [Li(OEt2)]+ building blocks play this role. The C„C triple bond distance of 14 is with 1.22(3) Å in the same range as observed for 15 (1.194(10) Å to 1.216(9) Å) and 16 (1.208(18) Å) [4]. For both, 15 and 16 an unsymmetrical p-bonding of the acetylides towards the silver(I) ions has been observed. For 14 the same structural behavior is found, an unsymmetrical p-bonding of the acetylides, however, towards the lithium ions, although the two different bond lengths Li1–C1 (2.26(5) Å) and Li1–C2 (2.46(5) Å) are not significantly different. This unsymmetrical bonding is characteristic for complexes possessing [M(C„CR)2(l-Li(OEt2)] structural motifs (e.g., Li–Ca = 2.21(2) Å versus Li–Cb = 2.82(2) Å and Li–Ca = 2.260(13) Å versus Li–Cb = 2.354(13) Å) [9], although the difference between the Li–Ca and Li–Cb bond lengths is very remarkable. In this context it is interesting to refer to [((Me3Si)2HC)2Al(C„CSiMe3)2(l-Li)] [9] with an unsolvated lithium ion capped by two acetylide ligands of which the two Li–C distances are different (Li–Ca = 2.217(5) Å, Li–Cb = 2.425(6) Å). In addition, a comparatively short AgLi contact has been observed for 14 (Fig. 2). The distance Ag1Li1 is with 3.193(17) Å significantly shorter than the sum of the van-der-Waals radii (3.54 Å).

H. Lang et al. / Inorganica Chimica Acta 373 (2011) 93–99

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Fig. 3. Graphical illustration of the orientation of selected polymeric chains of 14 to each other with respect to the unit cell in two different views. All hydrogen atoms are omitted; of disordered atoms only one position is shown.

Surprisingly, there is up to now only one report describing unsually short AgLi contacts. Chiang et al. describe for [Ag3Li2Ph6] anions a AgLi distance of 2.76(2) Å [9a]. The datively-bonded diethyl ether molecule to Li1 has a O–Li bond distance of 1.94(6) Å which is comparable to datively bonded Et2O molecules of {(Et2O)Li(tBu3SiC„C)2}Hf(C„CSitBu3)3(OEt2) (dLi–O = 1.91(2) Å) [9].

3. Conclusion Straightforward high-yield synthesis methodologies including the reaction of {[Ti](l-r,p-C„CR1)2}AgNO3 ([Ti] = (g5-C5H4SiMe3)2Ti; R1 = SiMe3, tBu. [Ti] = (g5-C5H5)2Ti; R1 = tBu) with lithium acetylides LiC„CR2 (R2 = SiMe3, Ph) and treatment of [Ti](C„CSiMe3)2 with 1/n[AgC„CR2]n (R2 = SiMe3, Ph) are described. The newly prepared heterobimetallic{[Ti](l-r,pC„CR1)2}AgC„CR2 species ([Ti] = (g5-C5H4SiMe3)2Ti, (g5C5H5)2Ti); R1 = SiMe3, tBu; R2 = SiMe3,Ph) feature a mono-nuclear AgC„CR2 entity which is stabilized by the chelating effect of the organometallic p-tweezer [Ti](C„CR1)2 thus giving rise to an 16valence electron count at silver. The appropriate bis(alkyne) silver(I) acetylides are compared to [AgC„CR]n species remarkable stable. The planar surrounding at silver(I) was confirmed by single X-ray structure determination. 13C{1H} NMR spectroscopy revealed that stable silver-carbon bonds exist as evidenced from 13C–107Ag and 13C-109Ag coupling constants indicating that the silver acetylide unit also remains in solution in the organometallic p-tweezer system. Thermal treatment of {[Ti](l-r,p-C„CR1)2}AgC„CR2 produced in terms of a redox reaction the corresponding 1,3-diynes R2C„C–C„CR2 together with elemental silver, as expected also the free tweezer molecule [Ti](C„CR1)2 could be isolated. In addition, the formation and solid-state structure of coordination polymer [(Ag(C„CR2)2)Li(OEt2)]n obtained from heterobimetallic {[Ti](l-r,p-C„CSiMe3)2}AgC„CSiMe3 and LiC„CSiMe3 or by the reaction of (Ag(C„CSiMe3) with LiC„CSiMe3 is discussed. This coordination polymer is one of the rare examples of structurally characterized silver(I) bis(acetylides) with lithium ions acting

unprecedentedly as connecting ions spanning [Ag(C„CSiMe3)2] units to give an one-dimensional polymeric chain.

4. Experimental 4.1. General methods All reactions were carried out under an atmosphere of nitrogen using standard Schlenk techniques. Tetrahydrofuran, diethyl ether and n-pentane were purified by distillation from sodium/benzophenone ketyl; toluene from sodium. Infrared spectra were recorded with a Perkin–Elmer FT-IR spectrometer Spectrum 1000. 1 H NMR spectra were recorded with a Bruker Avance 250 spectrometer operating at 250.130 MHz in the Fourier transform mode; 13 C{1H} NMR spectra were recorded at 62.860 MHz. Chemical shifts are reported in d units (parts per million) downfield from tetramethylsilane with the solvent as reference signal (1H NMR: CDCl3, d = 7.26; 13C{1H} NMR: CDCl3, d = 77.16). Microanalyses were performed by the Institute of Organic Chemistry, Chemnitz, University of Technology. 4.2. Reagents Starting materials [Ti](C„CR1)2 (R1 = SiMe3, tBu; [Ti] = (g5C5H5)2Ti), (g5-C5H4SiMe3)2Ti)) [8], {[Ti](l-r,p-C„CR1)2}AgNO3 (1, 2) [8e] and [AgC„CR2] (R2 = SiMe3, [5e] C6H5 [5i]) were prepared according to published procedures. All other chemicals were commercially purchased and used without further purification. 4.2.1. Synthesis of {(g5-C5H5)2Ti)(l-r,p-C„CtBu)2}AgNO3 (3) To [Ti](C„CtBu)2 (0.35 g, 1.02 mmol) dissolved in 25 mL of tetrahydrofuran [AgNO3] (0.17 g, 1.02 mmol) was added in a single portion at 25 °C. After stirring the reaction mixture for 3 h at this temperature it was filtered through a pad of Celite. All volatile materials were removed under reduced pressure and the remaining residue was washed with 3  5 mL portions of n-pentane and

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dried in oil pump vacuum to give 3 as a yellow solid. Yield: 0.52 mg (1.02 mmol, 100% based on AgNO3). Anal. Calc. for C22H28AgNO3Ti (510.20): C, 51.78; H, 5.54. Found: C, 51.61; H, 5.72%. IR (NaCl, cm1): 1998, mC„C; 1377, mNO3. 1H NMR (CDCl3): d 1.34 (s, 18 H, tBu), 6.19 (bs, 10 H, C5H5). 13C{1H} NMR (CDCl3): d 30.4 (C(CH3)3), 32.1 (C(CH3)3), 112.7 (C5H5), 118.7 (TiC„Cb), 154.2 (TiCa„C). 4.2.2. Synthesis of heterobimetallic 6–10 4.2.2.1. Method A. To trimethylsilylacetylene (0.05 mL, 0.38 mmol) dissolved in 20 mL of diethyl ether was added n-BuLi (0.15 mL, 2.5 M in hexane, 0.38 mmol) in a single portion at 0 °C. The resulting reaction mixture was stirred for 10 min and was than subsequently cooled to 70 °C. Afterwards, {[Ti](l-r,pC„CSiMe3)2}AgNO3 (1: 260 mg, 0.38 mmol; 2: 249 mg, 0.38 mmol, 3: 194 mg, 0.38 mmol) was added in a single portion and the temperature was allowed to reach 0 °C during 1 h. Please, notice that stirring in the dark is necessary, otherwise decomposition giving elemental silver and the corresponding 1,3-diyne is observed. After filtration through a pad of Celite, the remaining residue was washed with ice-cold n-pentane to afford 6 as yellow to orange solids. Yield: 6, 220 mg (0.305 mmol, 80% based on 1); 7, 207 mg (0.285 mmol, 75% based on 1); 8, 184 mg (0.266 mmol, 70 % based on 2); 9, 193 mg (0.278 mmol, 73% based on 2); 10, 110 mg (0.261 mmol, 53 % based on 3). 4.2.2.2. Method B. To a tetrahydrofuran solution containing 150 mg (0.29 mmol) of 11 was added 55 mg (0.27 mmol) of [AgC„CSiMe3] (12) in a single portion. The reaction mixture was stirred for 3 h at 0 °C in the dark until a clear solution was obtained. Afterwards, the reaction mixture was filtered through a pad of Celite and all volatiles were removed in oil pump vacuum. The remaining residue was thoroughly washed with ice-cold n-pentane and was then dried in oil-pump vacuum to give complex 6 as a yellow solid (110 mg, 0.15 mmol, 56% based on 12). An analogous procedure was applied in the synthesis of complex 7 (Yield: 105 mg, 0.145 mmol, 50% based on 13). 4.3. Analytic Data of 6–10 4.3.1. Complex 6 Anal. Calc. for C31H53AgSi5Ti (721.92): C, 51.58; H, 7.40. Found: C, 51.48; H, 7.38%. IR (NaCl, cm1): 2032, mC„CAg; 1941, mC„CTi. 1H NMR (CDCl3): d 0.15 (s, 9 H, SiMe3), 0.28 (s, 18 H, SiMe3), 0.39 (s, 18 H, SiMe3), 5.97 (pt, JHH = 2.2 Hz, 4 H, C5H4), 6.13 (pt, JHH = 2.2 Hz, 4 H, C5H4). 13C{1H} NMR (CDCl3): d 0.5 (SiMe3), 1.2 (SiMe3), 1.6 (SiMe3), 115.3 (C5H4), 117.6 (C5H4), 122.8 (Ci/C5H4), 123.6 (AgC„Cb). The resonance signal for Ag–Ca could not detected under the measurement conditions applied.135.0 (d, 1JCAg = 4.3 Hz, TiC„Cb), 165.5 (d, 1JCAg = 9.7 Hz, TiCa„C). 4.3.2. Complex 7 Anal. Calc. for C34H49AgSi4Ti (725.86): C, 56.26; H, 6.80. Found: C, 56.18; H, 6.80%. IR (NaCl, cm1): 2017, mC„CAg; 1944, mC„CTi. 1H NMR (CDCl3): d 0.29 (s, 18 H, SiMe3), 0.44 (s, 18 H, SiMe3), 6.04 (bs, 4 H, C5H4), 6.18 (bs, 4 H, C5H4), 7.10–7.45 (m, 5 H, C6H5). 13C{1H} NMR (CDCl3): d 0.6 (SiMe3), 1.2 (SiMe3), 113.5 (AgCa„C), 115.3 (C5H4), 117.8 (C5H4), 123.2 (Ci/C5H4), 123.7 (AgC„Cb), 125.4 (Ci/ C6H5) 128.2 (C6H5), 128.8 (C6H5), 131.9 (C6H5), 134.9 (d, 1 JCAg = 3.0 Hz, TiC„Cb), 165.0 (d, 1JCAg = 10.8 Hz, TiCa„C). 4.3.3. Complex 8 Anal. Calc. for C33H53AgSi3Ti (689.79): C, 57.46; H, 7.74. Found: C, 57.31; H, 7.65%. IR (NaCl, cm1): 2070, mC„CAg; 1938, mC„CTi. 1H NMR (CDCl3): d 0.16 (s, 9 H, SiMe3), 0.29 (s, 18 H, SiMe3), 1.49 (s, 18 H, tBu), 6.04 (bs, 8 H, C5H4). 13C{1H} NMR (CDCl3): d 0.1 (SiMe3),

0.9 (SiMe3), 31.2 (C(CH3)3), 31.9 (C(CH3)3), 113.2 (AgCa„C), 115.2 (C5H4), 117.8 (C5H4), 119.3 (Ci/C5H4), 121.8 (AgC„Cb), 131.6 (TiC„Cb), 169.0 (TiCa„C). 4.3.4. Complex 9 Anal. Calc. for C36H49AgSi2Ti (693.71): C, 62.33; H, 7.12. Found: C, 62.05; H, 7.05%. IR (NaCl, cm1): 2022, mC„CAg; 1945, mC„CTi. 1H NMR (CDCl3): d 0.33 (s, 18 H, SiMe3), 1.18 (s, 18 H, tBu), 6.12 (pt, JHH = 2.4 Hz, 4 H, C5H4), 6.63 (pt, JHH = 2.4 Hz, 4 H, C5H4), 7.13– 7.50 (m, 5 H, C6H5). 13C{1H} NMR (CDCl3): d 0.9 (SiMe3), 31.2 (C(CH3)3), 31.9 (C(CH3)3), 113.2 (AgCa„C), 115.2 (C5H4), 117.8 (C5H4), 119.3 (Ci/C5H4), 121.8 (AgC„Cb), 125.3 (Ci/C6H5) 128.8 (C6H5), 129.2 (C6H5), 131.6 (TiC„Cb), 132.6 (C6H5), 169.0 (TiCa„C). 4.3.5. Complex 10 Anal. Calc. for C27H37AgSiTi (545.43): C, 59.46; H, 6.84. Found: C, 59.30; H, 6.90%. IR (NaCl, cm1): 2015, mC„CAg; 1962, mC„CTi. 1H NMR (CDCl3): d 0.15 (s, 9 H, SiMe3), 1.46 (s, 18 H, tBu), 5.93 (bs, 10 H, C5H5). 13C{1H} NMR (CDCl3): d 0.3 (SiMe3), 28.9 (C(CH3)3), 31.1 (C(CH3)3), 109.6 (C5H5), 111.3 (AgC„Cb). The resonance signal for AgCa„C could not detected under the measurement conditions applied 129.4 (TiC„Cb), 151.3 (TiCa„C). 4.3.6. Synthesis of coordination polymer 14 4.3.6.1. Method A reaction of 4 with 6. To trimethylsilyl acetylene (0.05 mL, 0.38 mmol) dissolved in 20 mL of diethyl ether was added n-BuLi (0.15 mL, 2.5 M in hexane, 0.38 mmol) in a single portion at 0 °C. The resulting reaction mixture was stirred for 10 min and was than subsequently cooled to 70 °C. Afterwards, complex 6 (260 mg, 0.38 mmol) was added in a single portion and the temperature was allowed to reach 0 °C during 1.5 h. Subsequently filtration of the reaction mixture through a pad of Celite, concentrationof the eluateto 10 mL and crystallization at 20 °C afforded colorless crystals of 14 (111 mg, 2.5 mmol 70% based on 6). 4.3.6.2. Method B reaction of 4 with 12. n-BuLi (1.40 mL, 2.5 M in hexane, 3.5 mmol) was added dropwise to a solution of HC„CSiMe3 (50 mL, 3.5 mmol) in diethyl ether (20 mL) at 0 °C. After stirring the reaction mixture for 10 min it was cooled to 70 °C and 718 mg (3.5 mmol) of [AgC„CSiMe3] (12) was added in a single portion. The reaction mixture was stirred for 1.5 h while the temperature reached 0 °C and was than filtered through a pad of Celite. The eluate was concentrated to 10 mL and allowed to crystallize at 20 °C to afford colorless crystals of 14 (1.11 g, 2.5 mmol 70% based on 12). Anal. Calc. C14H28AgLiOSi2 (383.35): C, 43.86; H, 7.36. Found: C, 43.79; H, 7.42%. IR (NaCl, cm1): 1991, mC„CAg; 1965, mC„CTi.1H NMR (CDCl3): d 0.27 (s, 18 H, SiMe3), 1.15 (t, 6 H, 3JHH 7.5 Hz, Et2O), 3.55 (q, 4 H, 3JHH 7.5 Hz, Et2O). 13C{1H} NMR (CDCl3): d1.2 (SiMe3), 15.2 (CH2CH3), 65.8 (CH2CH3), 93.0 (AgC„C), 121.8 (C„CSiMe3). 4.3.7. X-ray structure determination of 7 and 14 The structures of 7 and 14 in the solid state were determined from single-crystal X-ray diffraction. Single crystals of 7 and 14 suitable for X-ray diffraction studies were obtained by cooling a saturated diethyl ether solution containing 7 or 14 to 20 °C. Data collection was performed on a Bruker SMART CCD diffractometer using Mo Ka radiation. Crystallographic data of 7 and 14 are given in Table 2. The structures were solved by direct methods (SHELX 97) [13]. An empirical absorption correction was applied. The structures were refined by the least-squares method based on F2 with all reflections [14]. All non-hydrogen atoms were refined anisotropically; the hydrogen atoms were placed in calculated positions.

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