Facile Access of Well-Defined Stable Divalent Lead Compounds with

Mar 24, 2009 - Compounds 2 and 3 are the first stable, monomeric lead(II) derivatives involving small alkyl and aryl groups Me and Ph, respectively, s...
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Organometallics 2009, 28, 2563–2567

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Facile Access of Well-Defined Stable Divalent Lead Compounds with Small Organic Substituents Anukul Jana, Sankaranarayana Pillai Sarish, Herbert W. Roesky,* Carola Schulzke, Alexander Do¨ring, and Michael John Institut fu¨r Anorganische Chemie, UniVersita¨t Go¨ttingen, Tammannstrasse 4, 37077 Go¨ttingen, Germany ReceiVed December 9, 2008

The reaction of 1 equiv of β-diketiminate lithium, LLi · OEt2 {L ) HC(CMeNAr)2 (Ar ) 2,6-iPr2C6H3), nacnac ligand} with 1 equiv of PbCl2 in THF afforded the β-diketiminate lead(II) chloride (1) as a yellow compound. Treatment of 1 with stoichiometric amounts of methyl lithium, phenyl lithium, lithium phenylacetylide, and silver triflate resulted in the divalent organolead compounds LPb(II)Me (2), LPb(II)Ph (3), LPb(II)CCPh (4), and LPb(II)OTf (5). Compounds 2 and 3 are the first stable, monomeric lead(II) derivatives involving small alkyl and aryl groups Me and Ph, respectively, supported by the β-diketiminate ligand. Compound 4 is the first alkynyl lead(II) derivative. All compounds (2, 3, 4, 5) were characterized by microanalysis, X-ray crystallography, and 1H, 13C, and 207Pb NMR spectroscopy. Single-crystal X-ray structural analyses indicate that compounds 2-4 are monomeric, and the lead center resides in a trigonalpyramidal environment, whereas 5 has a polymeric structure. The results demonstrate the effectiveness of the β-diketiminate ligand in creating a protected surrounding for the lead atom. Introduction With the resurgence of interest in stable N-heterocyclic carbenes over the years,1 the chemistry of their heavier analogues, silylenes, germylenes, stannylenes, and plumbylenes, has also attracted considerable interest. Organolead chemistry was primarily investigated with compounds of lead in the formal oxidation state IV. In contrast the chemistry of Pb(II) tends to be dominated by compounds with inorganic ligands, and bivalent organolead compounds are relatively rare and their chemistry is poorly explored.2,3 In the literature there are reported some homoleptic plumbylene complexes. The first well-characterized organolead(II) species was the bent sandwich complex Pb(η5C5H5)2,4 and this has been supplemented by a number of related derivatives that have a variety of substituents at the cyclopentadienyl ring.5 For many years, however, Pb[CH(SiMe3)2]2 was the only stable σ-bonded organolead(II) compound.6 But remarkably little is known about the chemistry of smaller heteroleptic organic derivatives such as L′Pb(II)R (L′ ) * To whom correspondence should be addressed. Fax: +49-551-393373. E-mail: [email protected]. (1) (a) Holschumacher, D.; Bannenberg, T.; Hrib, C. G.; Jones, P. G.; Tamm, M. Angew. Chem. 2008, 120, 7538–7542; Angew. Chem., Int. Ed. 2008, 47, 7428-7432. (b) Chase, P. A.; Stephan, D. W. Angew. Chem. 2008, 120, 7543–7547; Angew. Chem., Int. Ed. 2008, 47, 7433-7437. (2) (a) Harrison, P. G. ComprehensiVe Organometallic Chemistry; Pergamon: Oxford, 1984; Vol 2, Chapter 12. (b) Harrison, P. G. ComprehensiVe Organometallic Chemistry II; Elsevier: Amsterdam, 1995; Vol. 2, Chapter 7. (3) Kaupp, M.; Schleyer, P. v. R. J. Am. Chem. Soc. 1993, 115, 1061– 1073. (4) Fischer, E. O.; Grubert, H. Z. Anorg. Allg. Chem. 1956, 286, 237– 242. (5) Jutzi, P.; Burford, N. Chem. ReV. 1999, 99, 969–990. (6) (a) Davidson, P. J.; Lappert, M. F. J. Chem. Soc., Chem.Commun. 1973, 317–322. (b) Davidson, P. J.; Harris, D. H.; Lappert, M. F. J. Chem. Soc., Dalton Trans. 1976, 2268–2274. (c) Burton, N. C.; Cardin, C. J.; Cardin, D. J.; Twamley, B.; Zubavichus, Y. Organometallics 1995, 14, 5708–5710. (d) Stu¨rmann, M.; Weidenbruch, M.; Klinkhammer, K. W.; Lissner, F.; Marsmann, H. Organometallics 1998, 17, 4425–4428.

chelating ligand or bulky aryl ligand, and R a small substituent).7,8 The β-diketiminate ligand is a particularly versatile ligand for the stabilization of single-site metal centers with low valence states.9 Recently our group using this ligand reported the synthesis and structure of some heteroleptic germylene, stannylene, and plumbylene complexes.10 Now we are interested in the synthesis of heteroleptic plumbylene derivatives containing small organic substituents. Herein we report on the preparation and characterization of the monomeric LPb(II)Me (2), LPb(II)Ph (3), and LPb(II)CCPh (4) and the polymeric LPb(II)OTf (5) (Tf ) SO2CF3).

Results and Discussion The β-diketiminato-substituted chloroplumbylene LPb(II)Cl (1) was prepared from β-diketiminate lithium, LLi · OEt2, and 1 equiv of PbCl2 in THF. 1 readily reacts with 1.6 molar equiv of MeLi in diethyl ether at -78 °C to give a clear orange solution. The 1H NMR spectroscopic data of the reaction mixture indicate that the desired methyl-substituted plumbylene complex LPb(II)Me (2) is formed nearly quantitatively after warming to (7) (a) Pu, L.; Twamley, B.; Power, P. P. Organometallics 2000, 19, 2874–2881. (b) Hino, S.; Olmstead, M.; Philips, A. D.; Wright, R. J.; Power, P. P. Inorg. Chem. 2004, 43, 7346–7352. (8) (a) Chen, M.; Fulton, J. R.; Hitchcock, P. B.; Johnstone, N. C.; Lappert, M. F.; Protchenko, A. V. Dalton. Trans. 2007, 2770–2778. (b) Yao, S.; Block, S.; Brym, M.; Driess, M. Chem. Commun. 2007, 3844– 3846. (c) Pineda, L. W.; Jancik, V.; Nembenna, S.; Roesky, H. W. Z. Anorg. Allg. Chem. 2007, 633, 2205–2209. (d) Stasch, A.; Forsyth, C. M.; Jones, C.; Junk, P. C. New J. Chem. 2008, 32, 829–834. (9) Nagendran, S.; Roesky, H. W. Organometallics 2008, 27, 457–492. (10) (a) Ding, Y.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G.; Power, P. P. Organometallics 2001, 20, 1190–1194. (b) Ding, Y.; Hao, H.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G. Organometallics 2001, 20, 4806–4811. (c) Ding, Y.; Ma, Q.; Roesky, H. W.; Herbst-Irmer, R.; Uso´n, I.; Noltemeyer, M.; Schmidt, H.-G. Organometallics 2002, 21, 5216– 5220. (d) Pineda, L. W.; Jancik, V.; Roesky, H. W.; Neculai, D.; Neculai, A. M. Angew. Chem. 2004, 116, 1443–1445; Angew. Chem. Int. Ed. 2004, 43, 1419-1421. (e) Pineda, L. W.; Jancik, V.; Starke, K.; Oswald, R. B.; Roesky, H. W. Angew. Chem. 2006, 118, 2664–2667; Angew. Chem., Int. Ed. 2006, 45, 2602-2605.

10.1021/om801167c CCC: $40.75  2009 American Chemical Society Publication on Web 03/24/2009

2564 Organometallics, Vol. 28, No. 8, 2009 Scheme 1. Synthesis of Compounds 2, 3, 4, and 5

Jana et al.

The well-defined compound LPbPh (3) was obtained in high yield from the reaction of 1 with 1 equiv of PhLi at -78 °C in toluene (Scheme 1). Compound 3 is a yellow solid soluble in benzene, THF, n-hexane, and n-pentane and shows no decomposition on exposure to air for a short period of time. 3 was characterized by 1H, 13C, and 207Pb NMR spectroscopy, EI mass spectrometry, elemental analysis, and X-ray structural analysis. The 1H NMR spectrum of compound 3 shows a singlet at 4.79 ppm for the γ-CH proton and two septets (3.57, 3.20 ppm) corresponding to the CH protons of the iPr moieties. The 207Pb NMR of 3 exhibits a singlet at 2424 ppm. The most abundant ion peak in the EI mass spectrum appeared at m/z 702 for the molecular ion [M]+.

coordination environment of the central Pb atom exhibits the same distorted trigonal-pyramidal geometry as in compound 2 (Figure 3). Interestingly it is noted that the shortest C-C bonds (C1-C2 (1.368(8) Å) and C4-C5 (1.362(9) Å) of the phenyl ring are exactly opposite each other; this may be due to the influence of the Pb substituent. Furthermore, we examined the substitution reactions of 1 with selected nucleophiles in order to prepare other plumbylene derivatives. Treatment of 1 with PhCCLi and AgSO3CF3 resulted in the formation of 4 and 5, respectively (Scheme 1). The addition of PhCCLi to 1 in toluene at -78 °C proceeded smoothly to provide 4 in high yield. Maintaing an n-hexane solution of 4 for one day at -32 °C resulted in yellow crystals suitable for X-ray structural analysis. Compound 4 crystallizes in the triclinic space group P1j, with one monomer in the asymmetric unit. The coordination environment of the central Pb atom exhibits a distorted trigonal-pyramidal geometry (Figure 4). In the 207Pb NMR spectrum the resonance arises at δ ) 1463 ppm, which is different from that of 3 (δ ) 2424 ppm). In the literature there are no reports on compounds containing Pb(II) and acetylide linkages, but there are a few known examples containing Pb(IV) and acetylide substituents.11 The C1-C2 bond distance (1.214(5) Å) of 4 is in the range of a triple bond; therefore we assume that no additional electron density is shifted toward the Pb. The bond angle of Pb1-C1-C2 (159.9(3)°) is smaller than 180°, while the bond angle of C3-C2-C1 (177.0(4)°) is close to linear. Interestingly, replacement of the chloride group by the triflate substituent generates compound 5. The triflate anion (OSO2CF3) has served as an excellent leaving group in nucleophilic displacement reactions.12 Organoplumbylene triflates may act as precursors for further reactions. LPb(II)OSO2CF3 (5) was prepared in toluene solution in high yield as yellow crystals that are soluble in common organic solvents, such as n-hexane and toluene. Compound 5 crystallizes in the triclinic space group P1j (Figure 5). In the unit cell there are two asymmetric species, and each consists of four monomers of 5. The structure of 5 is not identical with those of the related β-diketiminate germanium(II)13 and tin(II) triflates.10a The coordination polymer of 5 is oriented along the b axis of the crystal. There are also empty channels present along the b axis being approximately 11 Å in diameter. Each lead in compound 5 is bound to two oxygen atoms of different triflate ions. One Pb-O bond is always shorter than the (av 2.586 Å) other one (av 2.624 Å). Even the short Pb-O bonds are considerably longer than the sum of the covalent radii of oxygen and lead (2.19 Å). This suggests that all lead oxygen bonds, which constitute essentially the building block of the backbone of the polymeric chain, are based on electrostatic nature rather than covalency. Interestingly for the lead atoms there is always one shorter and one longer bond to oxygen. However this is not the case for the oxygen atoms of one triflate molecule. O4 and O5 bound to S2 both form Pb-O bonds to lead (Pb2 and Pb3) with shorter distances (2.589 and 2.582 Å). In contrast O7 and O8 bound to S3 exhibit longer Pb-O bonds (Pb3 and Pb4), at 2.614 and 2.630 Å. This means that there is an irregularity of the expected sequence of

Maintaining an n-hexane solution of 3 for three days at -30 °C resulted in slightly yellow single crystals suitable for X-ray structural analysis. Compound 3 crystallizes in the monoclinic space group P21/n, with two molecules in the asymmetric unit (Table 1). There are two independent molecules in a unit that differ slightly with respect to distances and angles. The

(11) (a) Pant, B. C.; Davidsohn, W. E.; Henry, M. C. J. Organomet. Chem. 1969, 16, 413–417. (b) Nast, R.; Grouhi, H. J. Organomet. Chem. 1979, 182, 197–202. (c) Van Beelen, D. C.; Wolters, J.; De Vos, D. Main Group Met. Chem. 1998, 21, 55–64. (12) Howells, R. D.; McCown, J. D. Chem. ReV. 1977, 77, 69–92. (13) Yao, S.; Brym, M.; Merz, K.; Driess, M. Organometallics 2008, 27, 3601–3607.

room temperature and stirring for another 3 h (Scheme 1). After extraction with n-hexane, compound 2 can be obtained in the form of yellow crystals in 82% yield. Its composition and constitution are supported by elemental analysis and 1H, 13C, and 207Pb NMR spectroscopy. In addition, the structure of 2 has been confirmed by single-crystal X-ray structural analysis (Table 1, Figure 1). While compound 2 is sensitive to oxygen and moisture, it is indefinitely stable under dry nitrogen atmosphere. Compound 2 represents the first stable β-diketiminate plumbylene complex with the smallest alkyl group. EI-MS of 2 exhibits the monomeric molecular ion peak [M - Me]+. The 1 H NMR spectrum of 2 consists of a singlet resonance (0.55 ppm) for Pb-CH3 that is flanked by 207Pb satellite lines (2J(207Pb-1H) ) 72 Hz). Also the 207Pb NMR spectrum exhibits a singlet resonance (δ ) 3009 ppm) that is very much different from the parent compound [HC(CMeNAr)2PbCl] (Ar ) 2,6iPr2C6H3) (1), where the lead shows a resonance at δ ) 1413 ppm. This change was expected because of the different electronic nature of the substituents on the lead atoms. The other resonances of the 1H NMR spectrum and elemental analyses are in accordance with 2 as formulated. Furthermore we observed that the intermolecular Pb-Pb distance of 4.403 Å (Figure 2) is very much comparable with the Pb-Pb distance (4.129 Å) of weakly dimerized Pb[CH(SiMe3)2]2,6d rather than those (Pb-Pb 2.903-3.527 Å) of the diplumbylenes.7

Facile Access of Stable DiValent Lead Compounds

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Table 1. Crystallographic Data for the Structural Analyses of Compounds 2, 3, 4, and 5 empirical formula CCDC-No. T [K] cryst syst space group a [Å] b [Å] c [Å] R [deg] β [deg] γ [deg] V [Å3] Z Dcalcd [g cm-3] µ [mm-1] F(000) θ range [deg] reflns collected indep reflns data/restraints/params R1, wR2 [I > 2σ(I)]a R1, wR2 (all data)a GoF ∆F(max), ∆F(min) [e Å-3] a

C30H44N2Pb 711352 133(2) triclinic P1j 10.439(2) 11.973(2) 12.424(3) 90.45(3) 107.02(3) 108.52(3) 1399.2(5) 2 1.519 6.048 640 1.72-26.96 12 613 6022 6022/0/313 0.0283, 0.0781 0.0300, 0.0792 1.037 2.935, 1.668

C35H46N2Pb 711353 133(2) monoclinic P21/n 10.146(2) 31.930(6) 19.622(4) 90 99.34(3) 90 6273(2) 8 1.487 5.404 2816 1.23-25.86 52 523 12 096 12 096/0/710 0.0344, 0.0717 0.0508, 0.0759 0.970 2.109, -1.458

C37H46N2Pb 711354 133(2) triclinic P1j 8.7602(18) 11.529(2) 16.702(3) 75.20(3) 82.28(3) 87.86(3) 1616.1(5) 2 1.492 5.246 728 1.83-26.95 15 407 6979 6979/0/374 0.0257, 0.0487 0.0345, 0.0502 0.996 0.886, -1.002

C30H41F3N2O3PbS 711355 133(2) triclinic P1j 12.684(3) 24.602(5) 25.044(5) 105.80(3) 100.97(3) 93.75(3) 7325(3) 8 1.403 4.706 3072 1.39-25.89 58 828 28 118 28 118/0/1484 0.0525, 0.1022 0.0979, 0.1146 0.890 1.140, -2.024

R1 ) ∑|Fo| - |Fc|/∑|Fo|. wR2 ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]0.5.

alternating short and long bonds. We find instead Pb1-shortS1-long-Pb2-short-S2-short-Pb3-long-S3-long-Pb4-short-S4long-Pb1. Moreover the triflate based on S2 is most tightly bound to its neighboring lead atoms, while the triflate based on S3 in comparison is rather weakly bound. The only other pronounced crystallographic difference between these two triflate molecules is a different arrangement of weak hydrogen bonds between two fluorine atoms each to neighboring isopropyl groups of the nacnac ligands. F8 of the S3 triflate is hydrogen bound to two isopropyl groups of two different nacnac ligands on two different lead atoms (Pb3 and Pb4). F9 is only bound to nacnac isopropyl of Pb4. However, F6 of the S2 triflate is hydrogen bonded to two methyl groups of the same isopropyl group of one nacnac ligand on lead Pb3. F4 is again only bound to one nacnac methyl group of Pb2. F8 of the S3 triflate is therefore bridging two different nacnac ligands via hydrogen bonding and its position might be more constrained. This could be the reason for the longer and accordingly weaker Pb-O bonds of S3 triflate. For the S1 triflate there are only two

Figure 1. Molecular structure of 2. Anisotropic displacement parameters are depicted at the 50% probability level, and all restrained refined hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [deg]: Pb1-C1 2.300(4), Pb1-N1 2.345(3);N1-Pb1-C188.33(13),N2-Pb1-C191.04(13),N1-Pb1-N2 81.44(10).

hydrogen bonds present; both involve F2, which is interacting with two different nacnac ligands on Pb1 and Pb2. The other two fluorines (F1, F3) show no hydrogen bonds. For the S4 triflate three hydrogen bonds are present involving each of the three fluorines (F10, F11, F12). To summarize, each of the four triflate molecules participates in hydrogen bonding with methyl groups of the nacnac ligand via their fluorine atoms, but each does it in a different way, which might cause the inconsistency of the binding to the lead atoms of the polymeric chain. Unlike compounds 2-4, the 1H NMR spectrum of 5 shows only one singlet (δ ) 3.26 ppm) and two doublets for the methyl groups of the iPr substituents. This indicates that either compound 5 rapidly dissociates under formation of the OTf group and reassociates at the Pb center or OTf has a bridging function between two lead atoms, as observed in the solid state structure. In the 207Pb NMR spectrum the resonance arises at δ ) 1334 ppm, which is similar to that of 1 (δ ) 1413 ppm). Also in the 19 F NMR spectrum compound 5 exhibits a singlet resonance (δ ) -76.5 ppm). In Table 2 we have summarized the 207Pb(II)

Figure 2. Unit cell of the 2. Isopropyl groups of the phenyl ring are omitted for clarity.

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Figure 3. Molecular structure of 3. Anisotropic displacement parameters are depicted at the 50% probability level, and all restrained refined hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [deg]: Pb1-C1 2.300(5), Pb1-N1 2.319(4);N1-Pb1-C191.12(16),N2-Pb1-C195.22(16),N1-Pb1-N2 82.42(14).

Jana et al.

Figure 5. Molecular structure of 5. Anisotropic displacement parameters are depicted at the 50% probability level, and all restrained refined hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [deg] are Pb1-O1 2.595(6), Pb1-O11 2.638(6), O1-S1 1.450(7); N1-Pb1-O1 87.7(2), N2-Pb1-O1 102.6(2), N1-Pb1-N2 82.0(3). Table 2.

207

Pb NMR Data of Pb(II) β-Diketiminate Compounds

compounda

207

Pb {1H} NMR (δ, ppm)

LPbCl (1) LPbMe (2) LPbPh (3) LPbCCPh (4) LPbOTf (5) LPbOAr1 (Ar1 ) 2,6-tBu2C6H3) LPbN(SiMe3)2 LPbP(SiMe3)2 Pb[N(SiMe3)2]2 a

Figure 4. Molecular structure of 4. Anisotropic displacement parameters are depicted at the 50% probability level, and all restrained refined hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [deg]: Pb1-C1 2.276(3), C(1)-C(2) 1.214(5), C(2)-C(3) 1.442(5), Pb1-N1 2.300(3); N1-Pb1C1 89.04(11), N2-Pb1-C1 90.78(11), N1-Pb1-N2 81.82(9).

NMR data of lead(II) β-diketiminate compounds including Pb[N(SiMe3)2]2.14

Summary In conclusion the results show that small substituents can be introduced at the lead(II) center in terminal positions. The X-ray crystal structure of 2 demonstrates that only in the solid state a weak interaction is observed, whereas compounds 3 and 4 are monomeric under these conditions. Compound 5 exhibits a polymeric chain structure in the solid state and is well soluble in n-hexane and toluene, respectively. Therefore compounds 2-5 are interesting precursors for metathesis reactions. Preliminary results show that 2 and B(C6F5)3 react under salt formation.

Experimental Section All manipulations were performed under a dry and oxygen-free atmosphere (N2) using standard Schlenk techniques or inside an

1413 3009 2424 1463 1334 10408b 18248b -17378b 491614

L ) HC(CMeNAr)2 (Ar ) 2,6-iPr2C6H3).

MBraun MB 150-GI glovebox. All solvents were dried by an MBraun solvent purifying system prior to use. All the chemicals were purchased commercially and used as received. 1H, 13C, 19F, and 207Pb NMR spectra were recorded on a Bruker Avance 500 MHz instrument and referenced to the deuterated solvent in the case of the 1H and 13C NMR spectra. 19F and 207Pb NMR spectra were referenced to CFCl3 and Pb(Me)4 respectively. Elemental analyses were performed by the Analytisches Labor des Instituts fu¨r Anorganische Chemie der Universita¨t Go¨ttingen. EI-MS were measured on a Finnigan Mat 8230 or a Varian MAT CH5 instrument. UV-vis spectra were recorded on a Varian Cary 50 instrument. Melting points were measured in sealed glass tubes with a Bu¨chi melting point B 540 instrument and are not corrected. Synthesis of Compounds 2, 3, and 4. Compounds 2-4 are prepared in a similar way using different organo-lithium reagents. 2: A solution of MeLi in diethyl ether (0.63 mL, 1.6 M) was added drop by drop to a stirred solution of 1 (0.66 g, 1 mmol) in diethyl ether (25 mL) at -78 °C. The reaction mixture was warmed to room temperature and stirred for an additional 3 h. After removal of all the volatiles, the residue was extracted with n-hexane (20 mL) and the resulting solution concentrated to about 10 mL and stored in a -30 °C freezer. Yellow crystals of 2 suitable for X-ray diffraction analysis are formed after two days. Yield: 0.560 g (88%); mp 176 °C. 1H NMR (500 MHz, C6D6): δ 7.12-7.15 (m, 6H, ArH), 4.77 (s, 1H, γ-CH), 3.54 (sept, 2H, CH(CH3)2), 3.43 (sept, 2H, CH(CH3)2), 1.70 (s, 6H, CH3), 1.31 (d, 6H, CH(CH3)2), 1.21 (d, 6H, CH(CH3)2), 1.20 (d, 6H, CH(CH3)2), 1.19 (d, 6H, CH(CH3)2), 0.55 (s, 3H, Pb-CH3) ppm. 13C{1H} NMR (125.75 MHz, C6D6): δ 164.52 (CN), 144.35, 144.30, 142.71, 126.01, 124.21, 124.20 (Ar-C), 99.67 (γ-C), 76.63 (Pb-CH3), 28.64 (CHMe2), 27.49

Facile Access of Stable DiValent Lead Compounds (CHMe2), 27.21 (CHMe2), 24.91, 24.76, 24.08, 23.99 (Me) ppm. 207 Pb{1H} NMR (104.72 MHz, C6D6): δ 3009 ppm. EI-MS: m/z (%) 625 (100) [M+ - Me]. UV-vis (hexane): λmax 392 nm. Anal. Calcd for C30H44N2Pb (639.88): C, 56.31; H, 6.93; N, 4.38. Found: C, 56.45; H, 7.91; N, 4.40. 3: PhLi (0.52 mL, 1.9 M in di-n-butyl ether) and 1 (0.66 g, 1 mmol). Yield: 0.574 g (82%); mp 158 °C. 1H NMR (500 MHz, C6D6): δ 8.50 (d, 2H, o-Ph), 7.56 (t, 2H, m-Ph), 7.02-7.15 (m, 7H, Ar-H and p-Ph), 7.15 (dd, 1H, p-Ph), 4.79 (s, 1H, γ-CH), 3.57 (sept, 2H, CH(CH3)2), 3.20 (sept, 2H, CH(CH3)2), 1.75 (s, 6H, CH3), 1.36 (d, 6H, CH(CH3)2), 1.24 (d, 6H, CH(CH3)2), 1.06 (d, 6H, CH(CH3)2), 0.51 (d, 6H, CH(CH3)2) ppm. 13C{1H} NMR (125.75 MHz, C6D6): δ 164.40(CN), 145.14, 143.92, 142.34, 137.92, 130.43, 127.80, 127.20, 126.26, 124.67, 124.11 (Ar-C), 98.64 (γ-C), 28.70 (CHMe2), 27.65 (CHMe2), 25.32 (CHMe2), 24.91, 24.76, 24.58, 24.03 (Me) ppm. 207Pb{1H} NMR (104.72 MHz, C6D6): δ 2424 ppm. EI-MS: m/z (%) 702 (100) [M+]. UV-vis (hexane): λmax 393 nm. Anal. Calcd for C35H46N2Pb (701.95): C, 59.89; H, 6.61; N, 3.99. Found: C, 59.62; H, 6.60; N, 3.78. 4: PhCCLi (1.00 mL, 1.0 M in THF) and 1 (0.66 g, 1 mmol). Yield: 0.615 g (88%); mp 155 °C. 1H NMR (500 MHz, C6D6): δ 7.59 (d, 2H, o-Ph), 7.05 (t, 2H, m-Ph), 7.03-7.17 (m, 6H, Ar-H), 6.96 (tt, 1H, p-Ph), 4.87 (s, 1H, γ-CH), 4.08 (sept, 2H, CH(CH3)2), 3.32 (sept, 2H, CH(CH3)2), 1.71 (s, 6H, CH3), 1.47 (d, 6H, CH(CH3)2), 1.30 (d, 6H, CH(CH3)2), 1.22 (d, 6H, CH(CH3)2), 1.16 (d, 6H, CH(CH3)2) ppm. 13C{1H} NMR (125.75 MHz, C6D6): δ 189.25 (CC), 165.01 (CN), 145.42, 143.57, 142.60, 131.93, 126.89, 126.75, 126.47, 124.99, 123.84 (Ar-C), 114.26 (CC), 103.34 (γC), 28.67 (CHMe2), 28.06 (CHMe2), 27.96 (CHMe2), 25.01, 24.55, 24.26, 24.21 (Me) ppm. 207Pb{1H} NMR (104.72 MHz, C6D6): δ 1463 ppm. EI-MS: m/z (%) 726 (100) [M+]. UV-vis (hexane): λmax 382 nm. Anal. Calcd for C37H46N2Pb (725.97): C, 61.21; H, 6.39; N, 3.86. Found: C, 61.65; H, 6.64; N, 3.86. Synthesis of [{HC(CMeNAr)2}Pb(II)OSO2CF3] (Ar ) 2,6iPr2C6H3) (5). A solution of 1 (0.66 g, 1mmol) in toluene (15 mL) was added drop by drop to a stirred suspension of AgOSO2CF3 (0.26 g, 1 mmol) in toluene (10 mL) at room remperature. The solution was stirred for an additional 2 h. After filtration the filtrate was concentrated to about 10 mL and stored in a -30 °C freezer. Yellow crystals of 5 suitable for X-ray diffraction analysis are formed after two days. Yield: 0.690 g (90%); mp 243 °C. 1H NMR (500 MHz, C6D6): δ 6.99-7.12 (m, 6H, Ar-H), 4.88 (s, 1H, γ-CH), 3.26 (sept, 4H, CH(CH3)2), 1.60 (s, 6H, CH3), 1.26 (d, 12H, CH(CH3)2), 1.19 (d, 12H, CH(CH3)2) ppm. 13C{1H} NMR (125.75 MHz, C6D6): δ 165.51 (CN), 144.29, 140.93, 127.70, 124.65 (Ar-

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Figure 6. Asymmetric unit of 5. Isopropyl groups of the phenyl ring are omitted for clarity. C), 109.57 (γ-C), 28.60 (CHMe2), 27.81 (CHMe2), 26.23 (CHMe2), 24.63 (Me) ppm. 19F{1H} NMR (188.28 MHz, C6D6): δ -76.5 ppm. 207 Pb{1H} NMR (104.72 MHz, C6D6): δ 1334 ppm. EI-MS: m/z (%) 774 (100) [M+]. UV-vis (hexane): λmax 333 nm. Anal. Calcd for C30H41F3N2O3PbS (774.26): C, 46.56; H, 5.34; N, 3.62; S, 4.14. Found: C, 46.79; H, 5.42; N, 3.60; S, 4.16. Crystallographic Details for Compounds 2, 3, 4, and 5. Suitable crystals of 2, 3, 4, and 5 were mounted on a glass fiber, and data were collected on an IPDS II Stoe image-plate diffractometer (graphite-monochromated Mo KR radiation, λ ) 0.71073 Å) at 133(2) K. The data were integrated with X-Area. The structures were solved by direct methods (SHELXS-97)15 and refined by full-matrix least-squares methods against F2 (SHELXL97).15 In 5 there are some toluene molecules. We have omitted the reflections caused by toluene using the Squeeze routine of the Platon software.16 Therefore toluene is not refined in the structure since it is deleted from the reflection file. All non-hydrogen atoms were refined with anisotropic displacement parameters. Crystallographic data are presented in Table 1.

Acknowledgment. This work was supported by the Deutsche Forschungsgemeinschaft. Supporting Information Available: X-ray data for 2, 3, 4, and 5 (CIF). This material is available free of charge via the Internet at http://pubs.acs.org. OM801167C (14) Wrackmeyer, B. J. Magn. Reson. 1985, 61, 536–539. (15) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122. (16) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.