Amidinatogermylene Complexes of Copper, Silver, and Gold

Nov 6, 2015 - Organometallics , 2015, 34 (22), pp 5479–5484. DOI: 10.1021/acs.organomet. ... [email protected]. Cite this:Organometallics 34, 22, 5479-5...
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Amidinatogermylene Complexes of Copper, Silver, and Gold Lucía Á lvarez-Rodríguez, Javier A. Cabeza,* Pablo García-Á lvarez,* and Diego Polo Departamento de Química Orgánica e Inorgánica-IUQOEM, Universidad de Oviedo-CSIC, E-33071 Oviedo, Spain S Supporting Information *

ABSTRACT: The synthesis of the first amidinatogermylene derivatives of the three coinage metals, including the first silver halide complex containing a germylene ligand of any type, has been achieved by reacting metal chloride precursors with the very bulky amidinatogermylene Ge(tBu2bzam)tBu (tBu2bzam = N,N′-di(tert-butyl)benzamidinate). The reactions of Ge(tBu2bzam)tBu with an equimolar amount of MCl (M = Cu, Ag) led to the tetrameric complexes [M4(μ3-Cl)4{Ge(tBu2bzam)tBu}4] (M = Cu (1) and Ag (2)), which contain a pseudocubane-type M4(μ3-Cl)4 core. A similar reaction with [AuCl(tht)] (tht = tetrahydrothiophene) afforded the linear mononuclear derivative [AuCl{Ge( t Bu 2 bzam) t Bu}] (3). The ionic digermylene derivatives [M{Ge(tBu2bzam)tBu}2][BF4] (M = Cu (4) and Ag (5)) were satisfactorily prepared from the respective reactions of [Cu(MeCN)4][BF4] and Ag[BF4] with two equivalents of Ge(tBu2bzam)tBu. The Ge-bound tert-butyl group of Ge(tBu2bzam)tBu plays an important role in stabilizing compounds 1−5 against hydrolysis, since, under similar reaction conditions, no pure complexes could be isolated from reactions of the same metal precursors with the chlorogermylene Ge(tBu2bzam)Cl.

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INTRODUCTION Heavier tetrylenes (HTs), also known as heavier carbene analogues or group 14 metalylenes, are molecules that contain a heavier group 14 atom in the +2 oxidation state. Although their use as ligands in transition metal (TM) complexes has been known for the last 40 years, they and also their TM complexes are generally very unstable toward oxygen and moisture, and this fact has hampered an ample development of their TM chemistry.1,2 Very recently, amidinatotetrylenes, E(R1NCR2NR3)X (E = heavier group 14 atom, R1NCR2NR3 = amidinato chelating fragment, X = any anionic group), have boosted the TM chemistry of HTs.2 In fact, although the first amidinato-HT− TM complex was reported only seven years ago,3 more than 100 complexes of this type are currently known, and, remarkably, some of them have already been successfully used as catalyst precursors for useful reactions (Sonogashira, Kumada, and Negishi cross-couplings, ketone hydrosilylations, cycloadditions, arene C−H borylations, etc.).4 The current success of amidinato-HTs as ligands can be attributed, among other factors,2 to the fact that their steric and electronic features can be extensively tuned (R1, R2, R3, and X can be a great variety of groups). Despite the notable advance that the TM chemistry of amidinato-HTs has already reached,2 that involving the group 11 metals is still in its initial stages given that, to date, it is represented by only one recent contribution,5 which describes the synthesis and characterization of the copper(I) benzamidinatosilylenes [Cu(tmda){Si(tBu2bzam)X}]OTf (tmda = Me 2 N(CH 2 ) 2 NMe 2 ; t Bu 2 bzam = N,N′-di(tert-butyl)benzamidinate; X = Cl, OtBu, NMe2; OTf = triflate) and [Cu2{μ-Si2(tBu2bzam)2O}2](OTf)2 (Chart 1). © XXXX American Chemical Society

Chart 1. Previously Reported Amidinatotetrylene Derivatives of the Group 11 Metals

The current early stage knowledge of the amidinato-HT chemistry of the coinage metals, our recent successful synthesis of a variety of amidinatogermylene derivatives of manganese,6 ruthenium,7 and cobalt,8 and the fact that the copper,9 silver,9c,10 and gold9f,10a,11 complexes that are hitherto known to contain a neutral germylene ligand are still scarce (Chart 2) prompted us to attempt the synthesis of amidinatogermylene derivatives of the group 11 metals. We now report that the use of a sterically encumbered benzamidinatogermylene, Ge(tBu2bzam)tBu, which has a tertbutyl group directly attached to the germanium atom in addition to having two tert-butyl groups on the N atoms of the benzamidinato fragment, has allowed us to successfully synthesize the first amidinatogermylene complexes of the three group 11 metals, including the first silver halide complexes containing a germylene ligand of any type, and, Received: September 30, 2015

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is the only pure product that we could isolate from these reactions.12 It is interesting to note that no TM derivatives of Ge(tBu2bzam)Cl have been hitherto characterized as pure products, but the chlorosilylene Si(tBu2bzam)Cl has been often used as a ligand in stable TM complexes.4b,5,13 Two factors can be claimed as responsible for this difference: (a) germanium is larger than silicon and has a higher propensity to expand its coordination; (b) as silicon is more electronegative than germanium, the Ge−Cl and Ge−N bonds of Ge(tBu2bzam)Cl are more polarized than the Si−Cl and Si−N bonds of Si(tBu2bzam)Cl. Thus, in these compounds, the Ge atom is more electrophilic than the Si atom. In addition, the coordination of E(tBu2bzam)Cl (E = Si, Ge) to a TM is expected to increase the electrophilicity of the E atom. Consequently, chlorogermylene−TM complexes should be more susceptible to become involved in hydrolytic processes than similar chlorosilylene−TM complexes. Furhermore, in the case of chlorogermylene−M−Cl (M = Cu, Ag, Au) complexes, the small size of the chloride ligand of the MCl moiety and the low coordination number of the coinage metal should not provide any steric protection to the highly polarized Ge−Cl bond. The strained four-membered GeN2C ring of Ge(tBu2bzam)Cl should also contribute to some extent to the instability of its coinage metal complexes, because some chlorogermylene−M−X complexes (M = Cu, Ag, Au; Chart 2), in which the Ge atom belongs to a less strained five-9a,10b−d or six-membered9c−f,10a ring, have been previously reported. With the above analysis in mind, we reasoned that replacing the Cl atom of Ge(tBu2bzam)Cl with a tert-butyl group would enable the synthesis of the desired amidinatogermylene derivatives of the coinage metals, since the Ge−C bond of Ge(tBu2bzam)tBu should be much less polarized than the Ge− Cl bond of Ge(tBu2bzam)Cl and, additionally, the bulky tertbutyl group should protect the (free or coordinated) Ge atom from attacks of external nucleophiles. Prior to this work, the use of Ge(tBu2bzam)tBu as a ligand has been reported only once, in a paper dealing with amidinatogermylene derivatives of ruthenium carbonyl.7b Ge(tBu2bzam)tBu reacted readily with CuCl and AgCl in toluene at room temperature to give colorless solutions from which the germylene group 11 metal(I) derivatives [M4(μ3Cl)4{Ge(tBu2bzam)tBu}4], M = Cu (1), Ag (2), were isolated in good yields (Scheme 1).

Chart 2. Types of Germylenes Hitherto Used as Ligands in Group 11 Metal Complexes

consequently, to gather the first structural and spectroscopic data of this new family of complexes.

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RESULTS AND DISCUSSION We began this project by studying the reactions of the chlorogermylene Ge(tBu2bzam)Cl with CuCl, AgCl, and [AuCl(tht)] (tht = tetrahydrothiophene) in toluene solvent at room temperature. In all these cases, the starting coinage metal precursors were consumed in less than 1 h. However, even working under dry argon in carefully dried solvents and glassware, we were unable to obtain a pure coinage metal derivative of Ge(tBu2bzam)Cl. In all cases, these derivatives were contaminated with hydrolysis products (1H NMR analysis confirmed the presence of the benzamidinium cation [tBu2bzamH2]+ in the crude reaction mixtures) that we could not eliminate. The benzamidinium salt [tBu2bzamH2]Cl, most probably arising from processes of the type [MCl{Ge(tBu2bzam)Cl}] + H2O → MCl + GeO + [tBu2bzamH2]Cl,

Scheme 1. Synthesis of the Germylene Complexes Described in This Work

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Organometallics X-ray diffraction (XRD) analyses confirmed that, in the solid state, compounds 1 and 2 have the same molecular structure (Figures 1 and 2), which consists of a pseudocubane M4(μ3-

Figure 2. XRD molecular structure of 2 (25% displacement ellipsoids; Me groups and H atoms omitted for clarity). Selected interatomic distances (Å) and angles (deg): Ag1−Cl1 2.619(8), Ag1−Cl3 2.749(8), Ag1−Cl4 2.594(7), Ag1−Ge1 2.424(4), Ge1−C16 2.01(3), Ge1−N1 1.99(2), Ge1−N2 1.94(2), N1−C4 1.43(4), N1− C5 1.31(4), C5−C6 1.51(5), N2−C5 1.24(4), N2−C12 1.50(4); N1− Ge1−N2 64(1), N1−Ge1−C16 105(1), N2−Ge1−C16 105(1), N1− Ge1−Ag1 119.6(7), N2−Ge1−Ag1 116.5(7), C16−Ge1−Ag1 128.3(8), N1−C5−N2 110(3), Cl1−Ag1−Ge1 124.2(2), Cl1−Ag1− Cl3 101.6(2), Cl1−Ag1−Cl4 95.5(2), Cl3−Ag1−Ge1 106.9(2), Cl3− Ag1−Cl4 101.9(2), Cl4−Ag1−Ge1 123.2(2).

Figure 1. XRD molecular structure of 1 (25% displacement ellipsoids; Me groups and H atoms omitted for clarity; the asymmetric unit contains only one-fourth of the molecule). Selected interatomic distances (Å) and angles (deg): Cu1−Cl1 2.364(2), Cu1−Cl3 2.401(2), Cu1−Cl4 2.549(2), Cu1−Ge1 2.2765(9), Ge1−C16 2.026(6), Ge1−N1 1.992(5), Ge1−N2 1.988(5), N1−C4 1.479(7), N1−C5 1.324(7), C5−C6 1.506(8), N2−C5 1.331(7), N2−C12 1.470(7); N1−Ge1−N2 66.0(2), N1−Ge1−C16 103.8(2), N2−Ge1− C16 103.7(2), N1−Ge1−Cu1 118.8(1), N2−Ge1−Cu1 118.8(1), C16−Ge1−Cu1 128.5(2), N1−C5−N2 109.4(5), Cl1−Cu1−Ge1 127.07(6), Cl1−Cu1−Cl3 101.60(6), Cl1−Cu1−Cl4 92.64(5), Cl3− Cu1−Ge1 119.28(6), Cl3−Cu1−Cl4 96.45(5), Cl4−Cu1−Ge1 112.91(5).

In the case of gold, Ge(tBu2bzam)tBu displaced the tht ligand of [AuCl(tht)], in toluene solvent at room temperature, to give the germylene gold(I) derivative [AuCl{Ge(tBu2bzam)tBu}] (3), which was isolated in 95% yield (Scheme 1). The XRD structure of 3 (Figure 3) confirms the mononuclear nature of this complex and the linear coordination of the chloride and germylene ligands to the gold atom, as is usual for [AuXL] (X = halide; L = neutral two-electron donor ligand) complexes.15 As mentioned in the Introduction, the hitherto known gold(I) germylene complexes are very few (Chart 2),9f,10a,11 and none of them contain an amidinatogermylene. With the purpose of extending the family of amidinatogermylene derivatives of the group 11 metals, we also performed reactions aimed at preparing complexes containing two germylene ligands. The ionic digermylene derivatives [M{Ge(tBu2bzam)tBu}2][BF4], M = Cu (4), Ag (5), were satisfactorily prepared from the respective reactions of [Cu(MeCN)4][BF4] and Ag[BF4] with two equivalents of Ge(tBu2bzam)tBu in toluene at room temperature (Scheme 1). The 1H and 13C NMR spectra of 4 and 5 are almost identical, and the (+)-FAB mass spectrum of 5 clearly shows the [Ag{Ge(tBu2bzam)tBu}2]+ ion as the cation of highest molecular weight. The structure depicted for these complexes in Scheme 1 was confirmed in the case of compound 5 by XRD (Figure 4). This structural determination revealed that, in the solid state, the [BF4]− anion is close to the silver atom (two F atoms are at a distance of 3.02 Å from the Ag atom). This proximity provokes the Ge−Ag−Ge angle to deviate 16.3° from linearity and thus reduce the steric hindrance between the [BF4]− anion and the germylene ligands. P−M−P angles of

Cl)4 core (the faces are distorted rhombs) in which the M and Cl atoms alternate their positions and each M atom is also attached to a terminal amidinatogermylene ligand. This tetrameric structure is rather common for the family of [MXL]n (M = Cu, Ag; X = halide; L = neutral two-electron donor ligand) complexes.14 Only two germylene derivatives of copper(I) halides have been previously reported, namely, [Cu 4 (μ 3 -I) 4 {Ge(2-pyC(SiMe 3 )CPhNSiMe 3 )Cl} 4 ] 9f and [Cu2(μ-I)2{Ge((NDiipCMe)2CH)OtBu}2] (Diip = 2,6-diisopropylphenyl).9d While the former is tetrameric, the latter is a dimer due to the larger volume of its germylene ligand. Germylene derivatives of silver(I) halides are unprecedented. We believe that compounds 1 and 2 maintain their tetrameric nature in solution. Although we have been unable to obtain an informative ESI or FAB mass spectrum of compound 1 (it decomposed in the matrices we used), the (+)-FAB spectrum of 2 (in 3-nitrobenzyl alcohol), although it does not contain the signal of the whole tetranuclear molecular ion [M]+, contains peaks that correspond to trinuclear and binuclear fragments of it, such as [M − 2Cl − Ag{Ge(tBu2bzam)tBu}]+ and [M − Cl−2Ag{Ge(tBu2bzam)tBu}]+. In addition, the respective 1H and 13C{1H} NMR spectra of 1 and 2 are almost identical and confirm the presence of only one type of germylene ligand. C

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The neutral copper(I) compound [CuI{Ge((NiPrCMe)2CH)Me}2]9e and the silver(I) salt [Ag{Ge((NDiipCMe)2CH)C2Ph}2][Ag(C6F5)2]10a are the only hitherto reported mononuclear group 11 metal complexes that contain two germylene ligands.

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CONCLUDING REMARKS In comparison with the Ge atoms of Ge(tBu2bzam)Cl and of its TM complexes, which are extremely susceptible to becoming involved in hydrolysis processes, the Ge atoms of Ge(tBu2bzam)tBu and of its TM complexes are less predisposed to be attacked by nucleophiles because, in addition to being sterically shielded by the Ge-bound tert-butyl group, they are less electrophilic. In fact, we have been unable to obtain pure Ge(tBu2bzam)Cl derivatives of the coinage metals, but the use of Ge(tBu2bzam)tBu has allowed us to prepare the first amidinatogermylene derivatives of these metals. While the Ge(tBu2bzam)tBu derivatives of the copper(I) and silver(I) chlorides are tetranuclear (compounds 1 and 2), that of gold(I) chloride is mononuclear (compound 3). The ionic digermylene derivatives [M{Ge(tBu2bzam)tBu}2][BF4], M = Cu (4) and Ag (5), have also been satisfactorily prepared.

Figure 3. XRD molecular structure of 3 (30% displacement ellipsoids; H atoms omitted for clarity). Selected interatomic distances (Å) and angles (deg): Au1−Cl1 2.3205(9), Au1−Ge1 2.3271(4), Ge1−C16 1.977(4), Ge1−N1 1.961(3), Ge1−N2 1.962(3), N1−C4 1.472(5), N1−C5 1.338(5), C5−C6 1.490(5), N2−C5 1.339(5), N2−C12 1.480(5); N1−C5−N2 108.9(3), N1−Ge1−N2 67.4(1), N1−Ge1− C16 108.6(2), N2−Ge1−C16 110.1(2), N1−Ge1−Au1 119.15(9), N2−Ge1−Au1 118.1(1), C16−Ge1−Au1 121.4(1), Cl1−Au1−Ge1 177.41(3).

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EXPERIMENTAL SECTION

General Procedures. Solvents were dried over appropriate desiccating reagents and were distilled under argon before use. All reactions were carried out under argon, using drybox and/or Schlenkvacuum line techniques because all reaction product were very sensitive to air and moisture. All reaction products were vacuum-dried for several hours prior to being weighed and analyzed. The germylenes Ge(tBu2bzam)Cl19 and Ge(tBu2bzam)tBu7b and the group 11 metal complexes [Cu(MeCN)4][BF4],20 [AuCl(tht)],21 and [Au(tht)2][BF4]22 were prepared following published procedures. All remaining reagents were purchased from commercial sources. NMR spectra were run in C6D6 on a Bruker DPX-300 instrument, using the solvent residual protic resonance for 1H [δ(C6HD5) = 7.16 ppm] and the solvent resonance for 13C [δ(C6D6) = 128.1 ppm]. Elemental analyses were obtained from a PerkinElmer 2400 microanalyzer. Lowresolution mass spectra (LRMS) were obtained on a VG Autospec double-focusing mass spectrometer operating in the FAB+ mode; ions were produced with a standard Cs+ gun at about 30 kV; 3-nitrobenzyl alcohol was used as matrix; data given correspond to the most abundant isotopomer of the molecular ion and/or of a fragment thereof. [Cu4(μ3-Cl)4{Ge(tBu2bzam)tBu}4] (1). Ge(tBu2bzam)tBu (0.65 mL of a 0.28 M solution in toluene, 0.182 mmol) was added to a suspension of CuCl (18 mg, 0.182 mmol) in toluene (4 mL), and the mixture was stirred at room temperature for 1 h. The reaction mixture was filtered, and the filtrate was vacuum-dried to give 1 as an off-white solid (77 mg, 92%). Anal. (%) Calcd for C76H128Cl4Cu4Ge4N8 (Mw = 1840.39): C, 49.60; H, 7.01; N, 6.09. Found: C, 49.62; H, 7.12; N, 6.12. 1H NMR (C6D6, 300.1 MHz, 293 K): δ 6.95−6.90 (m, 5 H, 5 CH of Ph), 1.35 (s, 9 H, 3 Me of GetBu), 1.09 (s, 18 H, 6 Me of 2 NtBu) ppm. 13C{1H} NMR (C6D6, 75.5 MHz, 293 K): δ 169.3 (NCN), 135.1 (s, Cipso of Ph), 130.0−127.7 (CHs of Ph), 53.5 (C of NtBu), 32.4 (Me of NtBu), 30.9 (C of GetBu), 28.1 (Me of GetBu) ppm. [Ag4(μ3-Cl)4{Ge(tBu2bzam)tBu}4] (2). Ge(tBu2bzam)tBu (0.56 mL of a 0.28 M solution in toluene, 0.157 mmol) was added to a suspension of AgCl (22 mg, 0.157 mmol) in toluene (4 mL), and the mixture was stirred at room temperature for 1 h. The reaction mixture was filtered, and the filtrate was vacuum-dried to give 2 as a white solid (48 mg, 61%). Anal. (%) Calcd for C76H128Ag4Cl4Ge4N8 (Mw = 2017.68): C, 45.24; H, 6.39; N, 5.55. Found: C, 45 29; H, 6.43; N, 5.51. (+)-FAB LRMS: m/z = 1477 (calcd for [Ag3Cl2{Ge( t Bu 2 bzam) t Bu} 3 ] + 1477.81), 973 (calcd for [Ag 2 Cl{Ge(tBu2bzam)tBu}2]+ 973.39), 829 (calcd for [Ag{Ge(tBu2bzam)tBu}2]+

Figure 4. XRD molecular structure of 5 (30% displacement ellipsoids; H atoms omitted for clarity; the asymmetric unit contains only onehalf of the molecule). Selected interatomic distances (Å) and angles (deg): Ag1−Ge1 2.4539(3), Ag1···F2 3.02(2), Ge1−C16 2.007(3), Ge1−N1 1.970(2), Ge1−N2 1.960(2), N1−C4 1.483(4), N1−C5 1.328(4), C5−C6 1.488(4), N2−C5 1.333(4), N2−C12 1.480(4), B1−F1 1.332(5), B1−F2 1.349(5); Ge1−Ag1−Ge1* 163.70(2), N1− C5−N2 108.9(2), N1−Ge1−N2 66.9(1), N1−Ge1−C16 106.7(1), N2−Ge1−C16 106.1(1), N1−Ge1−Ag1 118.68(7), N2−Ge1−Ag1 117.81(7), C16−Ge1−Ag1 125.70(9).

123.25° (M = Cu),16 156.65° (M = Ag),17 and 167.36° (M = Au)18 have been found in the solid state for the salts [M(PPh3)2][BF4], indicating that the ionic character of the BF4···M interaction increases from copper to gold. We also attempted the synthesis of a similar gold(I) digermylene derivative by treating [Au(tht)2][BF4] with two equivalents of Ge(tBu2bzam)tBu and, alternatively, by reacting [AuCl{Ge(tBu2bzam)tBu}] (3) with Ge(tBu2bzam)tBu and Ag[BF4], but in both cases we obtained mixtures of products that we could not separate. D

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Organometallics 830.07), 469 (calcd for [Ag{Ge(tBu2bzam)tBu}]+ 468.97). 1H NMR (C6D6, 300.1 MHz, 293 K): δ 7.35 (m, 1 H, 1 CH of Ph) 7.14−6.90 (m, 4 H, 4 CH of Ph), 1.35 (s, 9 H, 3 Me of GetBu), 1.14 (s, 18 H, 6 Me of 2 NtBu) ppm. 13C{1H} NMR (C6D6, 75.5 MHz, 293 K): δ 169.0 (NCN), 135.1 (s, Cipso of Ph), 129.9−127.5 (CHs of Ph), 53.7 (C of NtBu), 32.5 (Me of NtBu), 31.6 (C of GetBu), 27.8 (Me of GetBu) ppm. [AuCl{Ge(tBu2bzam)tBu}] (3). Ge(tBu2bzam)tBu (0.28 mL of a 0.28 M solution in toluene, 0.078 mmol) was added to a suspension of [AuCl(tht)] (25 mg, 0.078 mmol) in toluene (4 mL), and the mixture was stirred at room temperature for 1 h. The initial white color changed to light purple, indicating the presence of some gold nanoparticles. The reaction mixture was filtered, and the filtrate was vacuum-dried to give 3 as an off-white solid (44 mg, 95%). Anal. (%) Calcd for C19H32AuClGeN2 (Mw = 593.52): C, 38.45; H, 5.43; N, 4.72. Found: C, 38.51; H, 5.48; N, 4.69. (+)-FAB LRMS: m/z = 559 (calcd for [Au{Ge(tBu2bzam)tBu}]+ 558.07). 1H NMR (C6D6, 300.1 MHz, 293 K): δ 7.03−6.75 (m, 5 H, 5 CH of Ph), 1.10 (s, 9 H, 3 Me of GetBu), 0.79 (s, 18 H, 6 Me of 2 NtBu) ppm. 13C{1H} NMR (C6D6, 75.5 MHz, 293 K): δ 163.7 (NCN), 133.0 (Cipso of Ph), 131.0−127.7 (CHs of Ph), 53.8 (C of NtBu), 31.9 (Me of NtBu), 30.9 (C of GetBu), 27.0 (Me of GetBu) ppm. [Cu{Ge(tBu2bzam)tBu}2][BF4] (4). Ge(tBu2bzam)tBu (0.45 mL of a 0.35 M solution in toluene, 0.158 mmol) was added to a solution of [Cu(MeCN)4][BF4] (25 mg, 0.079 mmol) in toluene (4 mL), and the mixture was stirred at room temperature for 1 h. The reaction mixture was vacuum-dried to give compound 4 as an off-white solid (23 mg, 92%). Anal. (%) Calcd for C38H64BCuF4Ge2N4 (Mw = 872.55): C, 52.31; H, 7.39; N, 6.42. Found: C, 52.37; H, 7.43; N, 6.46. 1H NMR (C6D6, 300.1 MHz, 293 K): δ 7.65 (m, 1 H, 1 CH of Ph), 7.09−6.97 (m, 4 H, 4 CH of Ph), 1.42 (s, 9 H, 3 Me of tBu), 1.12 (s, 18 H, 3 Me of 2 tBu) ppm. 13C{1H} NMR (C6D6, 75.5 MHz, 293 K): δ 169.2 (NCN), 135.20 (s, Cipso of Ph), 129.9−127.5 (CHs of Ph), 53.3 (C of NtBu), 32.4 (Me of NtBu), 31.3 (C of GetBu), 28.6 (Me of GetBu) ppm. [Ag{Ge(tBu2bzam)tBu}2][BF4] (5). Ge(tBu2bzam)tBu (1.29 mL of a 0.28 M solution in toluene, 0.360 mmol) was added to a suspension of Ag[BF4] (35 mg, 0.180 mmol) in toluene (4 mL), and the mixture was stirred at room temperature for 1 h. The reaction mixture was filtered, and the filtrate was vacuum-dried to give compound 5 as an off-white solid (137 mg, 83%). Anal. (%) Calcd for C38H64AgBF4Ge2N4 (Mw = 916.87): C, 49.78; H, 7.04; N, 6.11. Found: C, 49.82; H, 7.12; N, 6.09. (+)-FAB LRMS: m/z = 829 (calcd for [Ag{Ge(tBu2bzam)tBu}2]+ 830.07), 469 (calcd for [Ag{Ge(tBu2bzam)tBu}]+ 468.97). 1H NMR (C6D6, 300.1 MHz, 293 K): δ 8.07 (m, 1 H, 1 CH of Ph), 7.04−6.91 (m, 4 H, 4 CH of Ph), 1.33 (s, 9 H, 3 Me of GetBu), 1.15 (s, 18 H, 6 Me of 2 NtBu) ppm. 13C{1H} NMR (C6D6, 75.5 MHz, 293 K): δ 170.8 (NCN), 134.4 (s, Cipso of Ph), 130.4−127.5 (CHs of Ph), 53.8 (C of NtBu), 32.3 (Me of NtBu), 31.4 (C of GetBu), 27.8 (Me of GetBu) ppm. X-ray Diffraction Analyses. Crystals of [tBu2bzamH2]Cl, 1·C6D6, 2·C7H8, 3, and 5 were analyzed by X-ray diffraction. A selection of crystal, measurement, and refinement data is given in Table S1 of the Supporting Information. Diffraction data were collected on an Oxford Diffraction Xcalibur Onyx Nova single-crystal diffractometer. Empirical absorption corrections were applied using the SCALE3 ABSPACK algorithm as implemented in CrysAlisPro RED23 (for [tBu2bzamH2]Cl, 1·C6D6, 3, and 5) and XABS224 (for 2·C7H8). The structures were solved using SIR-97.25 Isotropic and full matrix anisotropic leastsquares refinements were carried out using SHELXL-2014.26 The hydrogen atoms of the NH groups of [tBu2bzamH2]Cl were located in Fourier maps. The remaining hydrogen and deuterium (for the solvent molecule of 1·C6D6) atoms of all compounds were set in calculated positions and refined riding on their parent atoms. The data of 2·C7H8 were of poor quality [R1 (on F, I > 2σ(I)) = 0.113], probable due to (a) a very weakly diffracting crystal (no diffraction observed above 2θ = 120°), (b) twining problems (which could not be satisfactorily resolved), and/or (c) extensive positional disorder (see below). The solvent molecules of 1·C6D6 were disordered about centers of symmetry and required restraints on their geometrical and thermal

parameters. The methyl groups C21, C36, C38, C41, C56, and C76 of the tert-butyl groups of 2·C7H8 were found disordered over two positions in ratios of 55:45, 67:33, 67:33, 63:37, 54:46, and 53:47, respectively, and restraints were applied on their thermal and geometrical parameters. All non-hydrogen atoms were refined anisotropically, except the carbon atoms of the disordered solvent molecules of 1·C6D6 and of the disordered methyl groups and solvent molecule of 2·C7H8, which were kept isotropic because of their tendency to give nonpositive definite ellipsoids. The WINGX program system27 was used throughout the structure determinations. CCDC deposition numbers: 1428300 ([tBu2bzamH2]Cl), 1428301 (1·C6D6), 1428302 (2·C7H8), 1428303 (3), and 1428304 (5).

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.5b00828. Crystal, acquisition, and refinement XRD data; a view of the XRD structure of [tBu2bzamH2]Cl; 1H and 13C{1H} NMR spectra (PDF) X-ray crystallographic data (CIF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail (J. A. Cabeza): [email protected]. ́ ́ lvarez): [email protected]. *E-mail (P. Garcia-A Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work has been supported by MINECO-FEDER (CTQ2013-40619P and RYC2012-10491) and Principado de Asturias (GRUPIN14-009) research grants. We also thank the University of Oviedo and MINECO for predoctoral fellowships to L.A.-R. and D.P., respectively.

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REFERENCES

(1) For recent reviews on the general chemistry of HTs, including coordination chemistry, see: (a) Cabeza, J. A.; García-Á lvarez, P.; Polo, D. Eur. J. Inorg. Chem. 2015, in press (DOI: 10.1002/ejic.201500855). (b) Marschner, C. Eur. J. Inorg. Chem. 2015, 2015, 3805−3820. (c) Blom, B.; Gallego, D.; Driess, M. Inorg. Chem. Front. 2014, 1, 134− 148. (d) Blom, B.; Stoelzel, M.; Driess, M. Chem. - Eur. J. 2013, 19, 40−62. (e) Roesky, H. W. J. Organomet. Chem. 2013, 730, 57−62. (f) Ghadwal, R. S.; Azhakar, R.; Roesky, H. W. Acc. Chem. Res. 2013, 46, 444−456. (g) Yao, S.; Xiong, Y.; Driess, M. Organometallics 2011, 30, 1748−1767. (h) Asay, M.; Jones, C.; Driess, M. Chem. Rev. 2011, 111, 354−396. (i) Mandal, S. K.; Roesky, H. W. Chem. Commun. 2010, 46, 6016−6041. (j) Kira, M. Chem. Commun. 2010, 46, 2893−2903. (k) Nagendran, S.; Roesky, H. W. Organometallics 2008, 27, 457−492. (l) Zabula, A. V.; Hahn, F. E. Eur. J. Inorg. Chem. 2008, 2008, 5165− 5179. (m) Waterman, R.; Hayes, P. G.; Tilley, T. D. Acc. Chem. Res. 2007, 40, 712−719. (n) Leung, W.-P.; Kan, K.-W.; Chong, K.-H. Coord. Chem. Rev. 2007, 251, 2253−2265. (o) Kühl, O. Coord. Chem. Rev. 2004, 248, 411−427. (p) Okazaki, M.; Tobita, H.; Ogino, H. Dalton Trans. 2003, 493−506. (q) Gehrhus, B.; Lappert, M. F. J. Organomet. Chem. 2001, 617−618, 209−223. (r) Haaf, M.; Schmedake, T. A.; West, R. Acc. Chem. Res. 2000, 33, 704−714. (s) Tokitoh, N.; Okazaki, R. Coord. Chem. Rev. 2000, 210, 251−277. E

DOI: 10.1021/acs.organomet.5b00828 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics (2) For a review that comprehensively covers the transition metal chemistry of amidinatotetrylenes published up to the end of 2014, see: Á lvarez-Rodríguez, L.; Cabeza, J. A.; García-Á lvarez, P.; Polo, D. Coord. Chem. Rev. 2015, 300, 1−28. (3) Jones, C.; Rose, R. P.; Stasch, A. Dalton Trans. 2008, 2871−2878. (4) For examples of amidinato-HT−TM complexes as catalyst precursors, see: (a) Gallego, D.; Inoue, S.; Blom, B.; Driess, M. Organometallics 2014, 33, 6685−6697. (b) Blom, B.; Enthaler, S.; Inoue, S.; Irran, E.; Driess, M. J. Am. Chem. Soc. 2013, 135, 6703− 6713. (c) Someya, C. I.; Haberberger, M.; Wang, W.; Enthalter, S.; Inoue, S. Chem. Lett. 2013, 42, 286−288. (d) Gallego, D.; Brück, A.; Irran, E.; Meier, F.; Kaupp, M.; Driess, M. J. Am. Chem. Soc. 2013, 135, 15617−15626. (e) Wang, W.; Inoue, S.; Enthaler, S.; Driess, M. Angew. Chem., Int. Ed. 2012, 51, 6167−6171. (f) Brück, A.; Gallego, D.; Wang, W.; Irran, E.; Driess, M.; Hartwig, J. F. Angew. Chem., Int. Ed. 2012, 51, 11478−11482. (5) Tan, G.; Blom, B.; Gallego, D.; Driess, M. Organometallics 2014, 33, 363−369. (6) Cabeza, J. A.; García-Á lvarez, P.; Pérez-Carreño, E.; Polo, D. Inorg. Chem. 2014, 53, 8735−8741. (7) (a) Cabeza, J. A.; Fernández-Colinas, J. M.; García-Á lvarez, P.; Pérez-Carreño, E.; Polo, D. Inorg. Chem. 2015, 54, 4850−4861. (b) Á lvarez-Rodríguez, L.; Cabeza, J. A.; García-Á lvarez, P.; PérezCarreño, E.; Polo, D. Inorg. Chem. 2015, 54, 2983−2994. (c) Cabeza, J. A.; Fernández-Colinas, J. M.; García-Á lvarez, P.; Polo, D. RSC Adv. 2014, 4, 31503−31506. (d) Cabeza, J. A.; García-Á lvarez, P.; Polo, D. Dalton Trans. 2013, 42, 1329−1332. (8) Cabeza, J. A.; García-Á lvarez, P.; Pérez-Carreño, E.; Polo, D. Chem. - Eur. J. 2013, 20, 8654−8663. (9) (a) Yadav, D.; Siwatch, R. K.; Sinhababu, S.; Nagendran, S. Inorg. Chem. 2014, 53, 600−606. (b) West, J. K.; Fondong, G. I.; Noll, B. C.; Stahl, B. C. Dalton Trans. 2013, 42, 3835−3842. (c) Zhao, N.; Zhang, J.; Yang, Y.; Zhu, H.; Li, Y.; Fu, G. Inorg. Chem. 2012, 51, 8710−8718. (d) Ferro, I.; Hitchcock, P. B.; Coles, M. P.; Fulton, J. R. Inorg. Chem. 2012, 51, 1544−1551. (e) Arii, H.; Nakadale, F.; Mochida, K. Organometallics 2009, 28, 4909−4911. (f) Leung, W.-P.; So, C.-W.; Chong, K.-H.; Kan, K.-W.; Chan, H.-S.; Mak, T. C. W. Organometallics 2006, 25, 2851−2858. (g) York, J. T.; Young, W. B., Jr.; Tolman, W. B. Inorg. Chem. 2006, 45, 4191−4198. (10) (a) Zhao, N.; Zhang, J.; Yang, Y.; Cheng, G.; Zhun, H.; Roesky, H. W. Organometallics 2013, 32, 762−769. (b) Dias, H. V. R.; Ayers, A. E. Polyhedron 2002, 21, 611−618. (c) Ayers, A. E.; Dias, H. V. R. Inorg. Chem. 2002, 41, 3259−3268. (d) Dias, H. V. R.; Wang, Z. Inorg. Chem. 2000, 39, 3890−3893. (11) (a) Cabeza, J. A.; Fernández-Colinas, J. M.; García-Á lvarez, P.; Polo, D. Inorg. Chem. 2012, 51, 3896−3903. (b) Matioszek, D.; Kocsor, T.-G.; Castel, A.; Nemes, G.; Escudié, J.; Saffon, N. Chem. Commun. 2012, 48, 3629−3631. (12) The X-ray structure and the 1H and 13C{1H} NMR spectra of [tBu2bzamH2]Cl are provided in the Supporting Information. (13) (a) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Hey, J.; Krause, L.; Stalke, D. Dalton Trans. 2013, 42, 10277−10281. (b) Blom, B.; Driess, M.; Gallego, D.; Inoue, S. Chem. - Eur. J. 2012, 18, 13355− 13360. (c) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Hey, J.; Stalke, D. Chem. - Asian J. 2012, 7, 528−533. (d) Azhakar, R.; Ghadwal, R. S.; Roesky, H. W.; Wolf, H.; Stalke, D. J. Am. Chem. Soc. 2012, 134, 2423−2428. (e) Azhakar, R.; Roesky, H. W.; Holstein, J. J.; Dittrich, B. Dalton Trans. 2012, 41, 12096−12100. (f) Azhakar, R.; Sarish, S. P.; Roesky, H. W.; Hey, J.; Stalke, D. Inorg. Chem. 2011, 50, 5039−5043. (g) Sen, S. S.; Kritzler-Kosch, M. P.; Nagendran, S.; Roesky, H. W.; Beck, T.; Pal, A.; Herbst-Irmer, R. Eur. J. Inorg. Chem. 2010, 2010, 5304−53011. (h) Tavčar, G.; Sen, S. S.; Azhakar, R.; Thorn, A.; Roesky, H. W. Inorg. Chem. 2010, 49, 10199−10202. (14) See, for example, the XRD structures of [M4(μ3-Cl)4(PPh3)4] (M = Cu,14a Ag14b): (a) Churchill, M. R.; Kalra, K. L. Inorg. Chem. 1974, 13, 1065−1071. (b) Chen, F.; Oh, S.-W.; Wasylishen, R. E. Can. J. Chem. 2009, 87, 1090−1101.

(15) See, for example, the XRD structure of [AuCl(PPh3)]: Baenziger, N. C.; Bennett, W. E.; Soboroff, D. M. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1976, B32, 962−963. (16) Lippard, S. J.; Melmed, K. M. Inorg. Chem. 1967, 6, 2223−2228. (17) Bachman, R. E.; Andretta, D. F. Inorg. Chem. 1998, 37, 5657− 5663. (18) Wang, J.-C. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1996, C52, 611−613. (19) Nagendran, S.; Sen, S. S.; Roesky, H. W.; Koley, D.; Grubmüller, H.; Pal, A.; Herbst-Irmer, R. Organometallics 2008, 27, 5459−5463. (20) Kubas, G. J. Inorg. Synth. 1979, 19, 90−92. (21) Usón, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1989, 26, 85−91. (22) Oberbeckmann-Winter, N.; Braunstein, P.; Welter, R. Organometallics 2005, 24, 3149−3157. (23) CrysAlisPro RED, version 1.171.37.35; Oxford Diffraction Ltd.: Oxford, UK, 2014. (24) Parkin, S.; Moezzi, B.; Hope, H. J. Appl. Crystallogr. 1995, 28, 53−56. (25) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giacovazzo; Guagliardi, A.; Moliterni, A. G. C.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 1999, 32, 115−119. (26) SHELXL-2014: Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, A64, 112−122. (27) WINGX, version 1.80.05: Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837−838.

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DOI: 10.1021/acs.organomet.5b00828 Organometallics XXXX, XXX, XXX−XXX