Pyridyl Compounds of Heavier Group 13 and 14 Elements as Ligands

Article pubs.acs.org/Organometallics

Pyridyl Compounds of Heavier Group 13 and 14 Elements as Ligands for Lanthanide Metals Kornelia Zeckert* Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, D-04103, Leipzig, Germany S Supporting Information *

ABSTRACT: Reactivity studies of three different tris(2-pyridyl)stannate derivatives toward the Ln(II) compounds [Ln(Cp*)2(OEt2)] (Ln = Yb, Sm; Cp* = η5-C5Me5) are described. Thus, treatment of [La(Cp)3{Sn(2-py5Me)3Li(thf)}] (Cp = η5C5H5, py5Me = C5H3N-5-Me) with [Yb(Cp*)2(OEt2)] afforded the pentametallic complex [Yb{Sn(2-py5Me)3La(Cp)3}2] (1) with the Yb2+ cation encapsulated by two tris(2-pyridyl)stannate units and two unsupported Sn−La bonds in terminal positions. On the other hand, reaction of the bis(stannate) complex [Yb{Sn(2py3Me)3}2] (py3Me = C5H3N-3-Me) with [Yb(Cp*)2(OEt2)] gave the heteroleptic complex [Yb(Cp*){Sn(2-py3Me)3}] (2). Moreover, two samarium(III) compounds [Sm(Cp*) 2 {MEt 2(2py5Me)2}] with M = Ga (3), In (4) were obtained in a reductive approach. Compounds 1−4 have all been characterized by NMR spectroscopic and X-ray crystallographic studies.

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INTRODUCTION Due to their large ionic radii, lanthanides require sterically demanding ligands to kinetically stabilize the metal centers. Thereby the use of substituted cyclopentadienyl (Cp) ligands led to the discovery of numerous remarkable molecular lanthanide complexes. 1 In the last few decades bulky monoanionic hydrotris(pyrazolyl)borates (Tp, Trofimenko’s scorpionates; Chart 1) have been proven to be highly effective

divalent lanthanide cyclopentadienyl compounds [Ln(Cp*)2(OEt2)] (Ln = Eu, Yb; Cp* = η5-C5Me5) yielded complexes [Ln{Sn(2-pyMe)3}2] with the tris(2-pyridyl)stannate ligand acting as a six-electron N3-donor (Scheme 1). In these complexes, the Ln2+ cation is well separated from the formally negatively charged Sn(II) centers of each stannate unit, whereby the lone pair of electrons is located outside the cavity and hence still attractive for further metal coordination.6,7 In contrast, Sn−Ln metal−metal bond formation occurred in reactions with trivalent lanthanide compounds to give the donor−acceptor complexes [Ln(Cp)3{Sn(2-py5Me)3Li(thf)}] (Ln = La, Yb; py5Me = C5H3N-5-Me)8 (Scheme 1). The latter complexes are members of rare molecular 4f-element compounds featuring unsupported metal−metal bonds.9 Further examples include the Ge−Ln- and Sn−Ln-bonded compounds [Yb(GePh2)4(thf)4],10 [Eu(GePh3)2(dme)3],11 [Ln(Cp)2(GePh3)] (Ln = Er, Yb),12 [Ln(EPh3)2(thf)4] (Ln = Eu, Yb; E = Ge, Sn),13−15 [(SnPh3)(thf)2Yb(μ-Ph)3Yb(thf)3],15 [Yb(SnNep3)2(thf)2] (Nep = 2,2-dimethylpropyl),16 and [Ln{Sn(SnMe3)3}2(thf)4] (Ln = Sm, Yb).17 In 2006 Roesky reported on [(Cp*)2Ln{Al(Cp*)}] (Ln = Eu, Yb), which were the first compounds with group 13 to 4f-element bonds.18 Up to now also few Ga−Ln-19 as well as B−Ln-bonded20 complexes have been described. In addition to the ongoing progress in main-group chemistry, also several compounds with metal−metal bonds between d metals and 4f elements have been reported.21

Chart 1. Hydrotris(pyrazolyl)borate (I), Tris(pyrazolyl)tetrelide (II), and Tris(2-pyridyl)stannate (III) Ligands

in stabilizing both di- and trivalent lanthanide ions by a welldefined ligand environment.2 The change of the tripodal motive by switching the bridgehead atom to carbon,3 silicon,4 germanium, or tin5 resulted in anionic ligands, which can provide site-selective coordination by the N-chelating moiety as well as by the lone pair of electrons localized at the bridgehead atom. Recently the synthesis and reactivity of tris(2-pyridyl)stannate compoundscomparable to the pyrazolyl-based group 14 element derivativeshave been investigated. Reactions of their corresponding lithium complexes [Li(thf)Sn(2-pyMe)3] (pyMe = C5H3N-3-Me, C5H3N-5-Me) with © 2013 American Chemical Society

Special Issue: Recent Advances in Organo-f-Element Chemistry Received: November 7, 2012 Published: February 12, 2013 1387

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Organometallics

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Scheme 1. Reactivity of [Li(thf)Sn(pyR)3] toward Organolanthanide Compounds: κ3N vs κ1Sn Coordination

Scheme 2. Synthesis of Compound 1

Herein we report on reactions determined by the siteselective coordination of tris(2-pyridyl)stannate ligands toward di- and trivalent lanthanide ions, with preferred N3-donation of LnII, whereas SnII donation occurs with the more Lewis acidic LnIII. Moreover, we have recently shown that SnII donation can also be applied to the heavier group 13 element tris(alkyl) compounds, which resulted in the adducts [{Li(thf)Sn(2py5Me)3}MEt3] (M = Ga, In).7 Further results include reactivity studies of the latter adducts with the samarocene [Sm(Cp*)2(OEt2)].

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RESULTS AND DISCUSSION The dative Sn−La bond in [La(Cp)3{Sn(2-py5Me)3Li(thf)}]8 appeared to be relatively strong, and thus a salt metathesis reaction enabled the formation of the pentametallic complex [Ln{Sn(2-py5Me)3La(Cp)3}2] (1, Ln = Yb) through encapsulation of the Yb2+ cation by two tris(2-pyridyl)stannate units, with the Sn−La bonds being retained. Treatment of [Yb(Cp*)2(OEt2)] with 2 equiv of [La(Cp)3{Sn(2-py5Me)3Li(thf)}] in toluene immediately resulted in LiCp* elimination (Scheme 2). Filtration and minor concentration of the solution gave 1 as a poorly soluble dark green crystalline solid in good isolated yield (82%). The structure of compound 1, determined by single-crystal X-ray diffraction, is illustrated in Figure 1. The central Yb atom is octahedrally coordinated by six pyridyl nitrogen donor atoms with a staggered arrangement of the pyridine rings around the metal center and negligible twisting of all pyridine rings around the Sn−Cipso bonds (0.1(4)−0.3(3)° for Sn1 and 1.6(4)− 1.9(4)° for Sn2, respectively). The Yb−N distances and the N− Yb−N angles are similar to those in [Yb{Sn(2-py5Me)3}2].6 The Sn−La bonds in 1 of 3.3303(4) Å (La1−Sn1) and 3.3404(4) Å (La2−Sn2) are somewhat longer than in [La(Cp)3{Sn(2-

Figure 1. Molecular structure of 1 with 40% probability ellipsoids. Hydrogen atoms and noncoordinated solvent have been omitted for clarity. Selected distances (Å) and angles (deg): La1−Sn1 = 3.3303(4), La2−Sn2 = 3.3404(4), Yb1···Sn1 = 3.9077(4), Yb1···Sn2 = 3.8832(5), Yb1−N1 = 2.503(3), Yb1−N2 = 2.507(4), Yb1−N3 = 2.488(3), Yb1−N4 = 2.505(4), Yb1−N5 = 2.491(4), Yb1−N6 = 2.482(3), La1−Cg1 = 2.5805(3), La1−Cg2 = 2.5927(3), La1−Cg3 = 2.6123(3), La2−Cg1 = 2.5867(2), La2−Cg2 = 2.5957(4), La2−Cg3 = 2.6416(3), Sn1−C1 = 2.214(4), Sn1−C7 = 2.202(4), Sn1−C13 = 2.207(4), Sn2−C19 = 2.203(4), Sn2−C25 = 2.210(4), Sn2−C31 = 2.214(5); C1−Sn1−C7 = 96.8(1), C1−Sn1−C13 = 98.1(2), C7− Sn1−C13 = 99.1(1), C19−Sn2−C25 = 97.4(2), C19−Sn2−C31 = 98.7(2), C25−Sn2−C31 = 98.0(2), La1−Sn1···Yb1 = 174.53(1), La2−Sn2···Yb1 = 175.61(1), Sn1···Yb1···Sn2 = 176.95(1).

py5Me)3Li(thf)}] (3.3175(4) Å) but still lie within the sum of the respective covalent radii (Sn−La = 3.46 Å).22 In addition, the Sn atom possesses a trigonal-pyramidal geometry with Cipso−Sn−Cipso angles ranging from 96.8(1) to 99.1(1)°, being more obtuse upon lanthanide metal coordination in compar1388

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ison to the parent lithium stannate adduct [La(Cp)3{Sn(2py5Me)3Li(thf)}]. NMR studies of compound 1 were thwarted by its poor solubility in nonpolar solvents. The 1H NMR spectrum in THF-d8 revealed signals which correspond to the solid-state structure of 1 and additional signals after a period of time, evidencing disintegration in THF solution. In contrast, the Sn− La bond in the parent donor−acceptor complex [La(Cp)3{Sn(2-py5Me)3Li(thf)}] remained intact in THF solution. Hence, the preparation of 1 via a second approachthe subsequent metal coordination of the corresponding Yb(II) precursor [Yb{Sn(2-py5Me)3}2] with [La(Cp)3(thf)]was unsuccessful in either THF or toluene, which for the latter case might be due to the very low solubility of [La(Cp)3(thf)] in nonpolar solvents. In addition, following the approach of subsequent metal coordination for lanthanide bis(stannate) complexes in terminal positions, the treatment of [Yb{Sn(2-py3Me)3}2]7 with a Ln(II) compound, [Yb(Cp*)2(OEt2)], led to a ligand exchange reaction with formation of the heteroleptic complex [Yb(Cp*){Sn(2-py3Me)3}] (2) (Scheme 3). The reaction was unexpected, implying that N3 donation of the tris(2-pyridyl)stannate ligand may be preferred over SnII−LnII bond formation for Ln(II) ions.

Figure 2. Molecular structure of 2 with 40% probability ellipsoids. Hydrogen atoms have been omitted for clarity. Selected distances (Å) and angles (deg): Yb1−N1 = 2.406(2), Yb1−N2 = 2.444(3), Yb1···Sn1 = 3.5298(3), Yb−Cg1 = 2.4047(2), Sn1−C1 = 2.300(3), Sn1−C7 = 2.247(4); C1−Sn1−C7 = 96.5(1), C1−Sn1−C1′ = 99.7(1). Symmetry equivalent atoms are generated by x, −y + 1/2, z.

Ln(C6F5)] (Ln = Eu, Yb; Dmp = 2,6-Mes2C6H3 with Mes = 2,4,6-Me 3 C 6 H 2 ; Tph = 2-TripC 6 H 4 with Trip = 2,4,6-iPr3C6H2),24 [(DIPP-nacnac)YbR(thf)] (DIPP-nacnac = CH{(CMe)(2,6- i Pr 2 C 6 H 3 N)} 2 ; R = N(SiMe 3 ) 2 , CH(SiMe3)2),25,26 [(TptBu,Me)YbI(thf)] (TptBu,Me = hydrotris(3,5tert-butylmethylpyrazolyl)borate),27 or [Ln(Ph2pz)I(thf)4] (Ln = Eu, Yb; Ph2pz = 3,5-diphenylpyrazolate).28 Room-temperature 1H and 119Sn{1H} NMR spectra of complex 2 in toluene-d8 showed signals consistent with its molecular structure in the solid state. However, 2 slowly underwent ligand redistribution in solution to give [Yb{Sn(2py3Me)3}2] and [Yb(Cp*)2] over a period of days. Thereby, the ligand redistribution reaction appears to be much faster in THF than in toluene, which is in contrast with the results of solution studies for [(TpMe2)YbI(thf)2] (TpMe2 = hydrotris(3,5dimethylpyrazolyl)borate).27 It is noteworthy that neither homoleptic nor heteroleptic tris(2-pyridyl)stannate lanthanide(II) complexes could be synthesized in reactions of the lithium tris(2-pyridyl)stannate derivatives with Ln(II) iodides [LnI2(thf)2].29 In comparison, this salt metathesis reaction is a well-established route to gain the corresponding lanthanide(II) tris(pyrazolyl)borates. The formation of the bis(stannate) Ln(II) complexes [Ln{Sn(2-pyMe)3}2] only succeeds via LiCp* elimination, which is, however, limited to the cyclopentadienyl compounds [Ln(Cp*)2(OEt2)] for Ln = Eu, Yb.6,7 The encapsulation appears to be easier for the smaller Yb(II) ion than for the larger Eu(II) ion. The synthesis of analogous bis(stannate) Sm(II) complexes employing the precursor [Sm(Cp*)2(OEt2)] have failed so far. However, in course of our studies we observed enhanced LiCp* elimination with concomitant encapsulation of the Eu2+ cation by the tris(2-pyridyl)stannate unit after previous adduct formation in [{Li(thf)Sn(2-py5Me)3}MEt3] (M = Ga, In).7 Therefore, the samarocene [Sm(Cp*)2(OEt2)] was reacted with the tin to group 13 metal bonded adducts [{Li(thf)Sn(2py5Me)3}MEt3] (M = Ga, In), assuming enhanced reactivity with respect to LiCp* formation. Surprisingly, the reactions

Scheme 3. Synthetic Approach for Compound 2

Single crystals suitable for X-ray diffraction were obtained from toluene. The molecular structure of 2 is shown in Figure 2. Both metal atoms, Yb and Sn, are well separated from each other, although their distance (Yb···Sn = 3.5298(3) Å) is significantly shorter than in [Yb{Sn(2-py3Me)3}2] (3.7475(3) Å) or in the previously described 1 (3.8832(5), 3.9077(4) Å). The Sn−Cipso bond lengths (2.247(4)−2.300(3) Å) within the {Sn(2-py3Me)3}− anion of 2 are very similar to those found in the structure of [Yb{Sn(2-py3Me)3}2] (cf. Sn−Cipso = 2.232(4)− 2.277(4) Å), whereas the Cipso−Sn−Cipso angles (96.5(1)− 99.7(1)°) in 2 are more rigid in comparison to those in the precursor (cf. Cipso−Sn−Cipso 91.4(2)−102.3(2)°). As the formation of thermodynamically favored bis(ligand) Ln(II) complexes [Ln(L)2] is more likely, the number of isolated heteroleptic complexes [Ln(L)X] is comparatively small. Moreover, these complexes often tend to undergo ligand redistribution reactions, which typically result in the homoleptic bis(ligand) complexes [Ln(L)2] and [Ln(X)2].23 Steric protection offered by bulky ligands may prevent this ligand redistribution, as shown e.g. for monomeric [{Dmp(Tph)N3}1389

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[Sm{AlMe(2-py)2O}{AlMe(2-py)3}]2, in which oxidation of SmII to SmIII has occurred together with formation of the new dianionic species [AlMe(2-py)2O]2−.32

proceeded now with deposition of tin metal and formation of the orange complexes [Sm(Cp*)2{MEt2(2-py5Me)2}] (M = Ga (3), In (4)) containing a Sm(III) ion coordinated by an in situ generated novel ligand system based on the heavier group 13 elements gallium and indium. The products 3 and 4 were isolated in moderate to good yields (74% and 68%, respectively) by reacting samarocene with the lithium stannate adducts in a 1:1 stoichiometry (Scheme 4). Although the

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CONCLUSION In summary, reactivity studies of selected tris(2-pyridyl)stannate derivatives toward cyclopentadienyl Ln(II) compounds have been presented, highlighting the versatility of tris(2-pyridyl)stannate ligands in lanthanide chemistry. These led to formation of the pentametallic, mixed-valence complex [Ln{Sn(2-py5Me)3Ln(Cp)3}2] (1) with a divalent lanthanide ion (Ln = Yb) solely coordinated by the pyridine rings of each stannate unit, whereas the more acidic trivalent lanthanide (Ln = La) is bonded through the lone pair of electrons at the tin(II) center. In contrast, the attempted synthesis of a corresponding pentametallic YbII/(YbII)2 complex failed and resulted in a ligand exchange reaction to yield the heteroleptic compound [Yb(Cp*){Sn(2-py3Me)3}] (2). Finally, an enhanced reactivity of tris(2-pyridyl)stannate adducts of the heavier group 13 elements toward samarocene was established, which proceeded with the formation of the Sm(III) complexes [Sm(Cp*)2{MEt2(2-py5Me)2}] (M = Ga (3), In (4)), providing a combination of novel ligand design with metal complexation.

Scheme 4. Synthesis of Compounds 3 and 4

mechanism of this reaction remains unclear, the formation of the byproduct Li(2-py5Me) was established by NMR spectroscopic investigations. The 1H NMR spectra of both complexes 3 and 4 are in accordance with the paramagnetic nature of SmIII. X-ray crystallographic analyses of complexes 3 and 4 were carried out. Compounds 3 and 4 have similar structures, in which the samarium(III) ion is coordinated by two cyclopentadienyl ligands and two N-donor atoms of the corresponding bis(2-pyridyl) group 13 metalate ligand (Figure 3). The Sm···M distances are 3.8765(8) Å in 3 and 3.7973(4) Å in 4. This arrangement may be compared to that found for the tetraphenylborate salt [Sm(Cp*)2{(μ-Ph)2BPh2}],30 which contains a BPh4− anion loosely ligated to the metal via long metal−aryl linkages. Heavier group 13 pyridyl compounds have recently attracted attention as ligands in the coordination chemistry of maingroup and transition metals with a focus on tris(pyridyl) derivatives31 related to the tin analogues reported herein. Interestingly, the attempted synthesis of the neutral Sm(II) complex [Sm{AlMe(2-py)3}2] (py = C5H4N) from [Li(thf){AlMe(2-py)3}] resulted in an unexpected formation of dimeric

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EXPERIMENTAL SECTION

General Considerations. All manipulations of air- and moisturesensitive compounds were performed using standard Schlenk line techniques under an atmosphere of dry nitrogen or argon. THF was distilled from Na benzophenone prior to use. Toluene and diethyl ether were dried using an MBraun solvent purification system (SPS800). All solvents were stored over potassium mirror in resealable flasks. NMR spectra were recorded on a Bruker DPX400 spectrometer. Chemical shifts (δ) are referenced to the unified scale by using tetramethylsilane as an internal standard.33 Melting points were determined in sealed glass capillaries under a nitrogen atmosphere and are uncorrected. Mass spectra were recorded using a Thermo Fischer MAT 8230 mass spectrometer. CHN analyses were detected on a Vario EL III CHNS instrument. [Ln(Cp*)2(OEt2)]34 (Ln = Yb, Sm), [La(Cp)3{Sn(2-py5Me)3Li(thf)}],8 [Yb{Sn(2-py5Me)3}2],6 [Yb{Sn(2py3Me)3}2],7 and [{Li(thf)Sn(2-py5Me)3}MEt)3]7 (M = Ga, In) were synthesized according to literature procedures. Preparation of [Yb{Sn(2-py5Me)3La(Cp)3}2] (1). A mixture of [La(Cp)3{Sn(2-py5Me)3Li(thf)}] (0.47 g, 1 mmol) and [Yb(Cp*)2(OEt2)] (0.26 g, 0.5 mmol) in toluene (30 mL) was stirred

Figure 3. Molecular structures of (left) 3 and (right) 4 shown with 40% probability ellipsoids. Hydrogen atoms have been omitted for clarity. Selected distances (Å) and angles (deg) for 3: Sm1−N1 = 2.430(4), Sm1···Ga1 = 3.8765(8), Sm−Cg1 = 2.4512(1), Ga1−C1 = 2.047(6), Ga1−C7 = 2.006(6); C1−Ga1−C1′ = 118.2(3). Symmetry equivalent atoms are generated by −x + 1, y, −z + 3/2. Selected distances (Å) and angles (deg) for 4: Sm1−N1 = 2.442(3), Sm1···In1 = 3.7973(4), Sm−Cg1 = 2.4567(1), In1−C1 = 2.247(4), In1−C7 = 2.197(4); C1−In1−C1′ = 116.7(2). Symmetry equivalent atoms are generated by −x + 1, y, −z + 1/2. 1390

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Table 1. Crystallographic Details of [Yb{Sn(2-py5Me)3La(Cp)3}2] (1), [Yb(Cp*){Sn(2-py3Me)3}] (2), [Sm(Cp*)2{GaEt2(2py5Me)2}] (3), and [Sm(Cp*)2{InEt2(2-py5Me)2}] (4) empirical formula formula mass/amu cryst syst a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 temp/K space group Z μ/mm−1 no. of rflns measd no. of indep rflns Rint final R1 (I > 2σ(I)) final wR2(F2) (all data) CCDC no.

1·3.5(toluene)

2

3

4

C90.5H94N6Sn2La2Yb 1953.96 monoclinic 23.1975(16) 17.0581(9) 24.398(2) 90.0 116.846(10) 90.0 8614.0(10) 190(2) P21/n 4 2.662 61821 15764 0.0567 0.0422 0.1072 907812

C28H33N3SnYb 703.30 orthorhombic 21.3800(8) 14.6367(6) 8.4907(4) 90.0 90.0 90.0 2657.02(19) 130(2) Pnma 4 4.458 27124 4184 0.0493 0.0243 0.0463 907813

C36H52N2Ga2Sm 732.87 orthorhombic 11.6336(5) 19.3358(7) 15.0814(7) 90.0 90.0 90.0 3392.5(2) 130(2) Pbcn 4 2.533 8994 3477 0.0454 0.0381 0.0986 907814

C36H52N2In2Sm 777.97 orthorhombic 11.9097(2) 19.0579(4) 15.1619(3) 90.0 90.0 90.0 3441.36(11) 130(2) Pbcn 4 2.385 28991 4103 0.0782 0.0346 0.0677 907815

overnight at room temperature. After filtration from precipitated LiCp* the obtained dark brownish solution was concentrated and taken aside, yielding dark green crystals of 1 (0.67 g, 82%). Anal. Calcd (found) for C66H66N6La2Sn2Yb: C, 48.59 (49.00); H, 4.08 (4.09); N, 5.15 (5.17). 1H NMR (THF-d8, 400.1 MHz): δ 1.89 (s, 18H; Me), 5.97 (s, 30H; C5H5), 7.49 (br s, 6H; py), 7.57 (br s, 6H; py), 8.00 (br s, 6H; py) ppm. 119Sn{1H} NMR (THF-d8, 400.1 MHz): δ −120 ppm. MS (EI, 70 eV): m/z (%) 962 [Yb{Sn(2-py5Me)3}2] (10), 334 [La(Cp)3] (22), 269 [La(Cp)2] (78), 204 [La(Cp)] (19), 93 [2py5Me] (44), 65 [Cp] (100). Preparation of [Yb(Cp*){Sn(2-py3Me)3}] (2). To a solution of [Yb{Sn(2-py3Me)3}2] (1.23 g, 1.28 mmol) in toluene (20 mL) was added [Yb(Cp*)2(OEt2)] (0.66 g, 1.28 mmol) in toluene (10 mL). The mixture was stirred overnight at room temperature. Concentration to ca. 5 mL and storage at 4 °C overnight yielded dark brown crystals of compound 2 (1.56 g, 87%). Mp: 186 °C. Anal. Calcd (found) for C28H33N3SnYb: C, 47.82 (47.45); H, 4.73 (4.78); N, 5.97 (6.07). 1H NMR (toluene-d8, 400.1 MHz): δ 2.24 (s, 15H; C5Me5), 2.45 (s, 9H; Me), 6.61 (dd, 3JH−H = 7.6 Hz, 3H; py), 6.84 (d, 3JH−H = 7.6 Hz, 3H; py), 9.63 (d, 3H; py) ppm. 13C{1H} NMR (toluene-d8, 100.6 MHz): δ 11.0 (C5Me5), 23.6 (Me), 120.7 (py), 129.2 (py), 134.7 (py), 137.6 (C5Me5), 144.5 (2JC−Sn = 63.8 Hz; py), 146.5 (3JC−Sn = 20.8 Hz; py), 189.7 (py) ppm. 119Sn{1H} NMR (toluene-d8, 149.2 MHz): δ −251 ppm. Preparation of [Sm(Cp*)2{GaEt2(2-py5Me)2}] (3). A mixture of [{Li(thf)Sn(2-py5Me)3}GaEt3] (0.53 g, 0.78 mmol) and [Sm(Cp*)2(OEt2)] (0.39 g, 0.78 mmol) in toluene (20 mL) was stirred overnight at room temperature. After filtration from precipitated elemental tin the obtained brown solution was concentrated and taken aside, yielding orange crystals of 3 (0.45 g, 74%). Mp: 257 °C. Anal. Calcd (found) for C36H52N2GaSm: C, 59.00 (58.41); H, 7.15 (7.11); N, 3.82 (3.77). 1H NMR (toluene-d8, 400.1 MHz): δ −0.22 (q, 3JH−H = 8.0 Hz, 4H; Ga−CH2CH3), 1.02 (t, 3JH−H = 8.0 Hz, 6H; Ga− CH2CH3), 1.11 (s, 30H; C5Me5), 1.41 (s, 6H; Me), 2.93 (s, 2H; py), 6.16 (d, 3JH−H = 8.0 Hz, 2H; py), 6.39 (d, 3JH−H = 8.0 Hz, 2H; py) ppm. 13C{1H} NMR (toluene-d8, 100.6 MHz): δ 4.1 (Ga−CH2CH3), 12.6 (Ga−CH2CH3), 16.0 (C5Me5), 16.9 (Me), 125.9 (py), 130.0 (py), 135.7 (py), 137.5 (C5Me5), 148.3 (py) 182.8 (Cipso, py) ppm. MS (EI, 70 eV): m/z (%) 706 [M − Et] (87), 600 [Sm(Cp*)2{GaMe(2-pyR)}] (77), 422 [Sm(Cp*)2] (100), 379 [Sm(Cp*)(2-pyR)] (23), 287 [Sm(Cp*)] (88), 244 [Sm(2-pyR)] (46), 69 [Ga] (35).

Preparation of [Sm(Cp*)2{InEt2(2-py5Me)2}] (4). A mixture of [{Li(thf)Sn(2-py5Me)3}InEt 3] (0.84 g, 1.24 mmol) and [Sm(Cp*)2(OEt2)] (0.61 g, 1.24 mmol) in toluene (20 mL) was stirred overnight at room temperature. After filtration from precipitated elemental tin the obtained reddish brown solution was concentrated and taken aside, yielding orange crystals of 4 (0.66 g, 68%). Mp: 229 °C. Anal. Calcd for C36H52N2InSm (found): C, 55.58 (55.34); H, 6.74 (6.65); N, 3.60 (3.42). 1H NMR (toluene-d8, 400.1 MHz): δ −1.13 (q, 3 JH−H = 8.0 Hz, 4H; In−CH2CH3), 0.51 (t, 3JH−H = 8.0 Hz, 6H; In− CH2CH3), 0.99 (s, 30H; C5Me5), 2.55 (s, 6H; Me), 5.59 (s, 3JH−H = 8.0 Hz, 2H; py), 6.49 (d, 3JH−H = 8.0 Hz, 2H; py), 11.22 (s, 2H; py) ppm. 13C{1H} NMR (toluene-d8, 100.6 MHz): δ −0.1 (In−CH2CH3), 13.2 (In−CH2CH3), 16.2 (C5Me5), 18.2 (Me), 113.5 (py), 130.4 (py), 136.1 (py), 137.5 (C5Me5), 155.9 (py) 178.6 (Cipso, py) ppm. X-ray Crystallographic Studies of 1−4. Single crystals were obtained as described above with the synthetic procedures. The crystals were coated with a perfluoropolyether, picked up with a glass fiber, and mounted in the cooled nitrogen stream of the diffractometer. The crystallographic data were collected on a Xcalibur-S diffractometer (Oxford Diffraction) with Mo Kα radiation (λ = 0.71073 Å). The structures were solved by the direct or Patterson method and refined on F2 by full-matrix least squares (SHELX97)35 using all unique data. All non-hydrogen atoms are anisotropic, with H atoms included in calculated positions (riding model). Crystal data and details of the data collections and refinement are given in Table 1. One cyclopentadienyl group and one methyl group in 1 are disordered. Their carbon atoms were refined in split positions.

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ASSOCIATED CONTENT

S Supporting Information *

CIF files giving crystallographic data for 1−4. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The author declares no competing financial interest. 1391

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ACKNOWLEDGMENTS The author thanks the Deutsche Forschungsgemeinschaft (DFG) for generous financial support.

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