Diamine Bis(phenolate) M(III) (Y, Ti) Complexes: Synthesis, Structures

Organometallics 2009, 28, 3449–3458

3449

Diamine Bis(phenolate) M(III) (Y, Ti) Complexes: Synthesis, Structures, and Reactivity Sońia Barroso,† Jinlan Cui,‡ Jose´ Manuel Carretas,‡ Adelaide Cruz,‡ Isabel C. Santos,‡ M. Teresa Duarte,† Joaõ P. Telo,† Noe´mia Marques,*,‡ and Ana M. Martins*,† Centro de Quı´mica Estrutural, Instituto Superior Tećnico, AVenida RoVisco Pais, 1049-001 Lisboa, Portugal, and Instituto Tecnolo´gico e Nuclear, 2686-953 SacaVe´m, Portugal ReceiVed February 23, 2009

Reactions of titanium and yttrium trichlorides with 1 equiv of the sodium or potassium salts of the diamine bis(phenolate) H2tBu2O2NN′ (Me2NCH2CH2-(CH2-2-HO-3,5-C6H2tBu2)2) led to formation of [TiCl(tBu2O2NN′)(L)] (L ) THF, 1; py, 2) and [YCl(tBu2O2NN′)(DME)], 3. Reactions of 1 or 3 with MCH2-(2-NMe2)C6H4 and with M[2-(CH2NMe2)C6H4] (M ) Li, K) led to [Ti(tBu2O2NN′)(κ2(CH2C6H4NMe2))], 5, [Y(tBu2O2NN′)(κ2-(CH2C6H4NMe2))], 6, and [Y(tBu2O2NN′)(κ2-(C6H4CH2NMe2))], 7. [Y(tBu2O2NN′)N(SiMe3)2], 4, was obtained from 3 and KN(SiMe3)2, whereas [(Y(tBu2O2NN′)(CH2SiMe3))2(µ4O)(µ3-Li)2], 8, formed from reaction of 3 and LiCH2SiMe3. The reaction of 7 with 1 equiv of CH3CN gave [Y(tBu2O2NN′)(NC(CH3)C6H4CH2NMe2)], 10, which displays a chelating ketimide ligand formed by nitrile insertion in the Y-Ph bond. Further reaction with CH3CN led to [Y(tBu2O2NN′)(κ2(N(H)C(CH3)C(H)C(C6H4CH2NMe2)N(H)], 9, the formation of which involves an imine-enamine tautomerism followed by a second nitrile insertion and 1,3-hydrogen shift. The reaction of 1 with CH3CN gave [TiCl(tBu2O2NN′)(NCCH3)], which upon heating converts to a new paramagnetic species that is likely a chloride-bridged Ti(III) dimer. The EPR study performed reveals that bis(phenolate) Ti(III) complexes do not promote nitrile coupling reactions by electron transfer. The solid state molecular structures of 1-9 revealed that in all the complexes the bis(phenolate) ligand is coordinated to the metal center by the two oxygen atoms and the two nitrogen atoms with trans phenolate arrangement. Introduction In recent years group 3 and group 4 bis(phenolate) metal complexes have deserved considerable interest due to their properties as catalysts of olefin and cyclic ester polymerization.1-10 These studies have shown that the choice of phenolate ring substituents and its combination with extra donor moieties incorporated in the bis(phenolate) scaffolds are decisive for the stabilization of active catalytic species.3,4,11-14 A large variety of ligands, combining C-, N-, O-, S-, and P-based fragments with the bis(phenolate) frame, have been prepared and made evident that chelation has pronounced kinetic and thermodynamic consequences that prevent dimerization and ligand redistribution * Corresponding authors. E-mail: [email protected]. † Instituto Superior Tećnico. ‡ Instituto Tecnolo´gico e Nuclear. (1) Amgoune, A.; Thomas, C. M.; Carpentier, J.-F. Macromol. Rapid Commun. 2007, 28, 693. (2) Busico, V.; Cipullo, R.; Friederichs, N.; Ronca, S.; Togrou, M. Macromolecules 2003, 33, 3806. (3) Capacchione, C.; Proto, A.; Ebeling, H.; Mu¨lhaupt, R.; Mo¨ller, K.; Spaniol, T. P.; Okuda, J. J. Am. Chem. Soc. 2003, 125, 4964. (4) Tshuva, E. Y.; Groysman, S.; Goldberg, I.; Goldschmidt, Z. Organometallics 2002, 21, 662. (5) Gendler, S.; Groysman, S.; Goldschmidt, Z.; Shuster, M.; Kol, M. J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 1136. (6) Lian, B.; Beckerle, K.; Spaniol, T. P.; Okuda, J. Eur. J. Inorg. Chem. 2009, 311. (7) Amgoune, A.; Thomas, C. M.; Roisnel, T.; Carpentier, J.-F. Chem.sEur. J. 2006, 12, 169. (8) Salata, M. R.; Marks, T. J. J. Am. Chem. Soc. 2008, 130, 12. (9) Liu, X.; Shang, X.; Tang, T.; Hu, N.; Pei, F.; Cui, D.; Chen, X.; Jing, X. Organometallics 2007, 26, 2747. (10) Gendler, S.; Segal, S.; Goldberg, I.; Goldschmidt, Z.; Kol, M. Inorg. Chem. 2006, 45, 4783.

processes.15-17 Nevertheless, the studies reported so far did not focus on the reactivity of paramagnetic diamine bis(phenolate) species. The unique Ti(III) complex of this type described in the literature is the zwitterionic complex [Ti(Me2NCH2CH2N(CH2-2-O-3-tBu-5-MeC6H2)2(OiPr)2 · Na(THF)2] obtained by sodium amalgam reduction of the corresponding Ti(IV) bis(phenolate) diamine.18 In view of the reactivity of Ti(III) species in reductive coupling reactions19-22 and the role of redox-active ligands, as amido phenolates and diimine, in “oxidativeaddition” reactions to Zr(IV) recently reported,23-26 we decided to undertake a study of d1 Ti(III) complexes derived from (11) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Organometallics 2001, 20, 3017. (12) Groysman, S.; Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z.; Shuster, M. Organometallics 2004, 23, 5291. (13) Tshuva, E. Y.; Goldberg, I.; Kol, M. Inorg. Chem. 2001, 40, 4263. (14) Ikpo, N.; Butt, S. M.; Collins, K. L.; Kerton, F. M. Organometallics 2009, 28, 837. (15) Liang, L. C.; Chang, Y. N.; Lee, H. M. Inorg. Chem. 2007, 46, 2666. (16) Kawaguchi, H.; Matsuo, T. J. Organomet. Chem. 2004, 689, 4228. (17) Boyd, C. L.; Toupance, T.; Tyrell, B. R.; Ward, B. D.; Wilson, C.; Cowley, A. R.; Mountford, P. Organometallics 2005, 24, 309. (18) Sarazin, Y.; Howard, R. H.; Hughes, D. L.; Humphrey, S. M.; Bochmann, M. Dalton Trans. 2006, 340. (19) Covert, K. J.; Wolczanski, P. T.; Hill, S. A.; Krusic, P. Inorg. Chem. 1992, 31, 66. (20) Agapie, T.; Diaconescu, P. L.; Mindiola, D. J.; Cummins, C. C. Organometallics 2002, 21, 1329. (21) Mendiratta, A.; Cummins, C. C. Inorg. Chem. 2005, 44, 7319. (22) De Boer, E. J. M.; Teuben, J. H. J. Organomet. Chem. 1978, 153, 53. (23) Blackmore, K. J.; Sly, M. B.; Haneline, M. R.; Ziller, J. W.; Heyduk, A. F. Inorg. Chem. 2008, 47, 10522. (24) Stanciu, C.; Jones, M. E.; Fanwick, P. E.; Abu-Oma, M. M. J. Am. Chem. Soc. 2007, 129, 12400.

10.1021/om9001389 CCC: $40.75  2009 American Chemical Society Publication on Web 05/04/2009

3450 Organometallics, Vol. 28, No. 12, 2009

Barroso et al. Scheme 1

Me2NCH2CH2-(CH2-2-HO-3,5-C6H2tBu2)2 and analogous d0 Y(III) complexes in order to compare their reactivity and assess the potential of paramagnetic diamine bis(phenolate) complexes in electron transfer processes.

Results and Discussion Chemical Studies. The reaction sequence used to prepare all new compounds described in this work is presented in Scheme 1. Treatment of TiCl3(THF)3 with 1 equiv of the sodium derivative of the diamine bis(phenol) Me2NCH2CH2-(CH2-2HO-3,5-C6H2tBu2)2 (H2tBu2O2NN′) in THF led to the synthesis of [TiCl(tBu2O2NN′)(THF)], 1, in 83% yield. Addition of pyridine to a THF solution of 1 results in an immediate color change from orange to purple, indicative of THF replacement and the quantitative formation of [TiCl(tBu2O2NN′)(py)], 2. Similarly, YCl3(THF)2.5 reacts readily with 1 equiv of the potassium salt of H2tBu2O2NN′ in DME at room temperature to yield the corresponding diamine bis(phenolate)monochloride complex [YCl(tBu2O2NN′)(DME)], 3, in high yield. Formation of the monomeric yttrium complex 3 contrasts with the reported synthesis of [Y(tBu2O2NNpy)(µ-Cl)(py)]2 · 3(C6H6),17 with a pyridyl substituent in the donor arm, and emphasizes the importance of the terminal amine bulk on the structure of the (25) Blackmore, K. J.; Lal, N.; Ziller, J. W.; Heyduk, A. F. J. Am. Chem. Soc. 2008, 130, 2728. (26) Blackmore, K. J.; Ziller, J. W.; Heyduk, A. F. Inorg. Chem. 2005, 44, 5559.

compounds obtained. A comparable effect was noticed for the phenolate substituents, whose bulkiness is critical to the formation of mono- or binuclear complexes.13 Complexes 1 and 2 are the first neutral Ti(III) diamine bis(phenolate) reported in the literature. The magnetic susceptibility of 1 and 2 was determined at 25 °C as µeff ) 1.58 µB and µeff ) 1.46 µB, respectively. These values correspond to one unpaired electron per titanium, as expected for d1 metal centers. The EPR spectra of 1 (toluene, 293 K) and 2 (hexane, 90 K) display symmetrical single lines with g ) 1.954 and g ) 1.976, respectively, characteristic of Ti(III). The room-temperature 1H NMR spectra of 3 show one set of resonances for the diamine bis(phenolate) fragment, consistent with a Cs symmetric (tBu2O2NN′) ligand environment, which is not in accordance with the C1 symmetry found in the solid (vide infra) and was indicative of fluxional behavior. In addition the spectrum displays two resonances due to the protons of DME. Variable-temperature studies have shown that on cooling a solution of 3 in toluene-d8, decoalescence of the signals is observed at about -50 °C and each diamine bis(phenolate) ligand resonance splits into two in accordance with C1 symmetry. However, the low-temperature limiting spectrum could not be reached since the resonances due to DME protons remain broad even at -80 °C. The reaction of [YCl(tBu2O2NN′)(DME)] with 1 equiv of KN(SiMe3)2 in THF proceeds readily and yields, after simple workup, [Y(N(SiMe3)2)(tBu2O2NN′)], 4, which was obtained as a white powder in moderate yield. As described for 3, the room-

Ti and Y Diamine Bis(phenolate)

Organometallics, Vol. 28, No. 12, 2009 3451 Scheme 2

temperature 1H NMR spectrum of 4 displays Cs symmetry. On cooling a toluene-d8 solution of 4, all the resonances broaden and at -30 °C the signal assigned to the protons of the NSiMe3 groups splits into two at 0.63 and 0.39 ppm. At -50 °C the resonances of the tBu groups and the aromatic ring protons resolve into a C1 symmetry pattern, but the remaining signals are still poorly resolved. Treatment of [TiCl(tBu2O2NN′)(THF)], 1, and [YCl(tBu2O2NN′)(DME)], 3, with 1 equiv of KCH2-(2-NMe2)C6H4 and LiCH2(2-NMe2)C6H4, respectively, led to [Ti(tBu2O2NN′)(κ2-CH2C6H4NMe2)], 5, obtained in 92% yield as a green microcrystalline solid, and to [Y(tBu2O2NN′)(κ2-(CH2C6H4NMe2))], 6, isolated in 78% yield as a yellow powder. The effective magnetic moment of 5 at 22 °C was determined as µeff ) 1.55 µB, in accordance with the values obtained for 1 and 2. The room-temperature 1H NMR spectrum of 6 shows one set of resonances for the diamine bis(phenolate) fragment, consistent with a Cs symmetric tBu2O2NN′ ligand environment. On lowering the temperature, some of the resonances broadened into the baseline, but a limiting spectrum could not be reached in toluene. Reaction of [YCl(tBu2O2NN′)(DME)], 3, with 1 equiv of Li[2(CH2NMe2)C6H4] led to [Y(tBu2O2NN′)(κ2-(C6H4CH2NMe2))], 7. As for 6, the NMR spectrum of 7 features the required resonances for the protons of the diamine bis(phenolate) fragment consistent with a Cs symmetry and for the protons of the C6H4CH2NMe2 ligand. A similar reaction between [TiCl(tBu2O2NN′)(THF)], 1, and Li[2-(CH2NMe2)C6H4] was performed, but the characterization of a defined species was not possible. The addition of reagents caused a color change from orange to greenish, indicative of the presence of a new Ti(III) species, but all attempts to obtain good elemental analysis or crystals for X-ray diffraction failed. The magnetic susceptibility of the microcrystalline solid formed by cooling a hexane solution of the crude (µeff (14 °C) ) 1.51 µB) and the EPR spectrum in toluene (g ) 1.953) are compatible with the results obtained for the other Ti(III) complexes described (1, 2, and 5). The high instability of this product and, to a lesser extent, the instability of 5 contrast with that of pentacoordinate bis(phenolate) Ti(IV)

complexes27,28 and most likely results from the higher steric bulk of octahedral coordination and the lower metal oxidation state. Chloride metathesis of 3 with LiCH2SiMe3 gave, upon recrystallization from THF, the unusual complex Li2(µ4-O)[Y(tBu2O2NN′)(CH2SiMe3)]2, 8. The 1H and 13C NMR spectra of 8 reveal one set of resonances assigned to the tBu2O2NN′ ligand and the CH2SiMe3, consistent with Cs symmetry. The unequivocal identification of 8 was possible by X-ray diffraction (see below), which shows an unusual µ4-O bridge between two yttrium and two lithium centers. The origin of the oxygen bridge is likely THF, as the maintenance of the trimethylsilyl methane group in the yttrium coordination sphere rules out the possibility of reaction with moisture. We tentatively suggest that the formation of 8 may involve an ate-complex stabilized by (Li(THF)n)+. Related complexes bearing oxygen and lithium bridges have been reported for Sm and Y complexes.29-31 The reaction of 7 with an excess of CH3CN gave [Y(tBu2O2NN′)(κ2-(N(H)C(CH3)C(H)C(C6H4CH2NMe2)N(H)], 9. The proton NMR spectrum of 9 features four resonances for the tBu groups, four resonances for the aromatic phenoxide protons, four resonances for the methylenic NCH2PhOH protons, four signals for the diastereotopic methylenic protons of the NCH2CH2NMe2 chain, and two for the NMe2 groups. This pattern is consistent with a rigid complex in solution with C1 symmetry. Furthermore, the spectrum shows the expected resonances for the CH2C6H4NMe2 group and two additional resonances ascribed to the protons of one methyl and one methine group. This spectrum is consistent with the structure determined by X-ray diffraction analysis (see below) that reveals the formation of a metallacyclic ligand resulting from the insertion/coupling of two CH3CN (27) Gielens, E. E. C. G.; Dijkstra, T.; Berno, P.; Meetsma, A.; Hessen, B.; Teuben, J. H. J. Organomet. Chem. 1999, 591, 88. (28) Fokken, S.; Spaniol, T. P.; Kang, H. C.; Massa, W.; Okuda, J. Organometallics 1996, 15, 5069. (29) Evans, W. J.; Sollberger, M. S.; Hanusa, T. P. J. Am. Chem. Soc. 1988, 110, 1841. (30) Dube, T.; Gambarotta, S.; Yap, G. Organometallics 1998, 17, 3967. (31) Aspinall, H. C.; Tillotson, M. R. Inorg. Chem. 1996, 35, 2163.


Figure 1. EPR spectra obtained during a period of time, upon addition of CH3CN to 1.

molecules and the CH2C6H4NMe2 ligand. The reaction was followed by proton NMR. Addition of 1 equiv of CH3CN to a C6D6 solution of 7 showed the quantitative formation of a new species that was identified as [Y(tBu2O2NN′)(NC(CH3)C6H4CH2NMe2)], 10, which contains a ketimide fragment formed by acetonitrile insertion in the Y-C bond. Addition of a second equivalent of CH3CN led to 9. The formation of 9 may be envisaged as represented in Scheme 2. The decisive reaction step is an imine-enamine tautomerism that creates a nucleophilic methylene center through a 1,3-hydrogen shift (i in Scheme 2). Subsequent intramolecular nucleophilic attack on the nitrile carbon and a second γ-H shift, commonly observed when the ketimide fragment is part of a metallacycle, may thus lead to 9.32,33 Similar reactions have been reported to take place in metal-sp3 carbon bonds of zirconocene metallacycles and metal-sp2 bonds of scandium metallocenes.32,34,35 The reaction of [Ti(tBu2O2NN′)(κ2-(CH2C6H4NMe2))], 5, with acetonitrile proved unfruitful. A progressive color change from greenish to red was observed upon CH3CN addition to a toluene solution of 5; nevertheless, it was not possible to isolate any compound resulting from nitrile insertion in the Ti-C bond or resulting from an electron transfer process.22 The reaction of [TiCl(tBu2O2NN′)(THF)], 1, with CH3CN was then performed (Figure 1). In this case the nonexistence of a Ti-C bond excludes the possibility of nitrile insertion, and it was possible to follow the reaction by EPR. A new Ti(III) species with g ) 1.962 forms upon addition of the nitrile. This complex is likely [TiCl(tBu2O2NN′)(CH3CN)] (1/CH3CN). The spectrum shows that at room temperature the two compounds are present in solution and 1/CH3CN is the major species. On heating at 70 °C another Ti(III) complex starts to form with g ) 1.957. On prolonged heating, either 1 or 1/CH3CN is completely converted into the third compound, which is the thermodynamic product and confirms that electron transfer from the titanium to the ligands does not take place. Attempts to characterize this compound have not yet been productive, but we tentatively assign this result to the formation (32) Bercaw, J. E.; Davies, D. L.; Wolczanski, P. T. Organometallics 1986, 5, 450. (33) Doxsee, K. M.; Farahi, J. B.; Hope, H. J. Am. Chem. Soc. 1991, 113, 8889. (34) Bolton, P. D.; Feliz, M.; Cowley, A. R.; Clot, E.; Mountford, P. Organometallics 2008, 27, 6096. (35) Ferreira, M. J.; Martins, A. M. Coord. Chem. ReV. 2006, 250, 118.

Barroso et al.

Figure 2. ORTEP diagram of [TiCl(tBu2O2NN′)(THF)], 1, with 40% probability ellipsoids.

Figure 3. ORTEP diagram of [TiCl(tBu2O2NN′)(py)], 2, with 40% probability ellipsoids.

of a chlorine-bridged Ti(III) dimer that might form upon dissociation of CH3CN and, possibly, NMe2 dissociation favored by heating. The dimerization would thus result from the coordinative insaturation of the transient tetracoordinated Ti center. We are currently working to test this hypothesis. Crystallographic Studies. The molecular structures of complexes 1-9 were determined by single-crystal X-ray diffraction analysis. Crystals of 1 were obtained from hexane at -20 °C with two molecules and one cocrystallized hexane molecule in the unit cell. Crystals of 2 and 5 were obtained from toluene and hexane, respectively. The crystals of 5 were small and had poor diffracting power, so that the diffraction data obtained have low quality. Even so, the structure was unequivocally determined and the data are in agreement with those obtained for the other Ti(III) complexes reported. ORTEP drawings of 1, 2, and 5 are shown in Figures 2-4, respectively. Relevant bond lengths and angles are displayed in Table 1. In all complexes the metal coordination geometry is best described as distorted octahedral. The equatorial plane is defined by O(1), O(2), and N(2) of the bis(phenolate) ligand and the neutral ligand (THF, 1, py, 2, NMe2, 5). The axial positions are occupied by the tripodal nitrogen N(1) and Cl(1) in 1 and 2 and C(71) in 5. All compounds have in common trans-phenolate moieties. In 1 and 2 the titanium atom is slightly away from the equatorial mean square plane (0.1622(19) and 0.1580(13) Å, respectively), while in 5 it is perfectly within the plane (0.0752(24) Å). The Ti-O distances in complexes 1, 2, and 5 are within the range usually found and comparable to others reported for octahedral diamine


Organometallics, Vol. 28, No. 12, 2009 3453

Figure 4. ORTEP diagram of [Ti(tBu2O2NN′)(κ2-CH2C6H4NMe2)], 5, with 40% probability ellipsoids. Table 1. Selected Bond Lengths [Å] and Angles (deg) for 1, 2, and 5 Ti(1)-O(2) Ti(1)-O(1) Ti(1)-N(1) Ti(1)-N(2) Ti(1)-Cl(1) Ti(1)-O(3) Ti(1)-C(71) Ti(1)-N(3) O(1)-Ti(1)-O(2) N(1)-Ti(1)-Cl(1) N(3)-Ti(1)-N(1) C(71)-Ti(1)-N(1) N(3)-Ti(1)-N(2) O(3)-Ti(1)-N(2)

1

2

1.906(3) 1.905(3) 2.277(4) 2.281(4) 2.4182(15) 2.225(3)

1.898(2) 1.904(2) 2.259(3) 2.296(2) 2.4166(11)

167.54(14) 173.95(10)

2.245(3) 166.25(9) 169.31(7) 173.49(10)

5 1.894(4) 1.924(4) 2.386(5) 2.312(5)

Figure 5. ORTEP diagram of [YCl(tBu2O2NN′)(DME)] · 0.5(O2C4H10) (3 · 0.5(O2C4H10)), with 40% probability ellipsoids.

2.276(5) 2.315(6) 163.04(17) 110.38(18) 170.84(18) 173.86(18)

172.23(15)

bis(phenolate) complexes.13,17,18,36,37 The Ti-N distances found in complexes 1 and 2 are in the upper range of Ti-Namine bond lengths typically found in neutral Ti(III) complexes (1.857-2.285 Å),38-40 although they are shorter than in the anionic Ti(III) diamine bis(phenolate) complex [Ti(Me2NCH2CH2N(CH2-2-O-3t Bu-5-MeC6H2)2(OiPr)2 · Na(THF)2]18 (d(Ti-N) 2.357 Å) and in Ti(III) trisamidotriazacycloundecane [Ti(N(Ph)SiMe2)3-tacu], which displays Ti-N bond lengths as long as 2.425 Å.41 In 5, those distances are clearly longer than in 1 and 2. The lengthening of the Ti-N(1) bond, in particular, is noticeable due to the trans effect produced by the alkyl moiety of the CH2PhNMe2. Complex 3 crystallized from a DME solution with two crystallographically independent molecules (3a, 3b) in the unit cell and one DME molecule in the lattice. Colorless crystals of 4 were grown from a toluene/hexane mixture. ORTEP diagrams for 3a and 4 are shown in Figures 5 and 6, respectively and selected bond lengths and angles are given in Table 2. The seven-coordinate yttrium center in 3 is surrounded by two oxygen atoms and two nitrogen atoms from the diamine bis(phenolate) ligand, one chlorine atom, and two oxygen atoms of the DME molecule. The coordination geometry, which is (36) Groysman, S.; Goldberg, I.; Kol, M.; Genizi, E.; Goldschmidt, Z. Inorg. Chim. Acta 2003, 345, 137. (37) Tshuva, E. Y.; Versano, M.; Goldberg, I.; Kol, M.; Weitman, H.; Goldschmidt, Z. Inorg. Chem. Commun. 1999, 2, 371. (38) Barroso, S.; Cui, J. L.; Dias, A. R.; Duarte, M. T.; Ferreira, H.; Henriques, R. T.; Oliveira, M. C.; Ascenso, J. R.; Martins, A. M. Inorg. Chem. 2006, 45, 3532. (39) Bodner, A.; Jeske, P.; Weyhermuller, T.; Wieghardt, K.; Dubler, E.; Schmalle, H.; Nuber, B. Inorg. Chem. 1992, 31, 3737. (40) Dias, A. R.; Martins, A. M.; Ascenso, J. R.; Ferreira, H.; Duarte, M. T.; Henriques, R. T. Inorg. Chem. 2003, 42, 2675. (41) Martins, A. M.; Ascenso, J. R.; de Azevedo, C. G.; Dias, A. R.; Duarte, M. T.; Ferreira, H.; Ferreira, M. J.; Henriques, R. T.; Lemos, M. A.; Li, L.; da Silva, J. F. Eur. J. Inorg. Chem. 2005, 1689.

Figure 6. ORTEP diagram of [Y(N(SiMe3)2)(tBu2O2NN′)], 4, with 40% probability ellipsoids.

distorted due to the constrained nature of the κ4-O2NN′ ligand, can be described as a capped octahedron. In molecule 3a the atoms O(1), N(1), and N(2) occupy one triangular face, while O(2), Cl(1), and O(10) form a staggered triangular face on the other side of the central yttrium atom and O(11) is capping the latter face of the octahedron. In 3b the coordination polyhedron is defined by O(3), N(3), N(4) and O(4), Cl(2), O(21), with O(20) in the capping position. Compound 4 adopts a distorted trigonal-bipyramidal geometry, with N(1) and N(3) occupying the axial sites (N(1)-Y-N(3) angle of 154.73(15)°). The average Y-O distances to the phenoxide ligand in 3a and in 3b are slightly longer than the corresponding distance in 4, as expected for a compound with a higher coordination number. The Y-N(1) and Y-N(2) distances in 3a and the Y-N(3) and Y-N(4) in 3b are similar to the corresponding distances in 4. The two TMS groups in the amide ligand of 4 are inequivalent (the Y-N(3)-Si(1) angle is more acute than the Y-N(3)-Si(2) angle by 14.3°) and in accordance with the corresponding resonances in the low-temperature 1H NMR separated by 0.24 ppm. The Y-O and Y-N distances found in 3 and 4 compare with those reported for [Y(tBu2O2NO)(CH2SiMe3)(THF)],42 (42) Cai, C.-X.; Toupet, L.; Lehmann, W.; Carpentier, J.-F. J. Organomet. Chem. 2003, 683, 131.


Barroso et al.

Table 2. Selected Bond Lengths [Å] and Angles (deg) for 3 · 0.5(O2C4H10) and 4 3b Y(2)-O(3) Y(2)-O(4) Y(2)-O(21) Y(2)-O(20) Y(2)-Cl(2) Y(2)-N(3) Y(2)-N(4)

2.137(7) 2.188(8) 2.455(9) 2.622(8) 2.618(4) 2.579(9) 2.617(12)

O(3)-Y(2)-O(4) O(3)-Y(2)-N(3) O(3)-Y(2)-N(4) O(4)-Y(2)-N(3) O(4)-Y(2)-N(4) N(3)-Y(2)-N(4) O(3)-Y(2)-O(21) O(4)-Y(2)-O(21) O(3)-Y(2)-Cl(2) O(4)-Y(2)-Cl(2) N(3)-Y(2)-Cl(2) N(4)-Y(2)-Cl(2) O(21)-Y(2)-Cl(2) O(21)-Y(2)-N(3) O(21)-Y(2)-N(4)

153.7(3) 75.9(3) 92.7(4) 79.9(3) 88.1(4) 68.6(3) 79.4(3) 87.3(3) 94.3(2) 111.7(3) 145.8(3) 79.4(3) 128.7(2) 82.4(3) 150.9(3)

3a Y(1)-O(1) Y(1)-O(2) Y(1)-O(10) Y(1)-O(11) Y(1)-Cl(1) Y(1)-N(1) Y(1)-N(2) Y(1)-N(3) N(1)-Y(1)-N(3) N(2)-Y(1)-N(3) O(1)-Y(1)-O(2) O(1)-Y(1)-N(1) O(1)-Y(1)-N(2) O(2)-Y(1)-N(1) O(2)-Y(1)-N(2) N(1)-Y(1)-N(2) O(1)-Y(1)-O(10) O(2)-Y(1)-O(10) O(1)-Y(1)-Cl(1) O(2)-Y(1)-Cl(1) N(1)-Y(1)-Cl(1) N(2)-Y(1)-Cl(1) O(10)-Y(1)-Cl(1) O(10)-Y(1)-N(1) O(10)-Y(1)-N(2) O(1)-Y(1)-N(3) O(2)-Y(1)-N(3)

2.156(8) 2.166(7) 2.501(8) 2.610(9) 2.611(3) 2.557(9) 2.620(12)

152.6(3) 77.6(3) 92.2(3) 76.4(3) 86.8(3) 69.4(3) 78.8(3) 89.3(3) 93.4(2) 113.2(2) 146.4(2) 78.8(2) 127.7(2) 82.7(3) 151.9(3)

4 2.120(4) 2.134(4)

2.534(4) 2.583(5) 2.325(5) 154.73(15) 91.07(16) 104.27(17) 81.34(14) 98.19(15) 77.56(14) 136.77(14) 69.85(15)

Figure 8. ORTEP diagram of [YtBu2O2NN′)(C6H4CH2NMe2)], 7, with 40% probability ellipsoids. Table 3. Selected Bond Lengths [Å] and Angles (deg) for 6 · (C7H8) and 7 118.85(16) 108.90(15)

[Y(tBu2O2NO)(N(SiHMe2)2)(THF)], [Y(tBu2O2NNpy)(µ-Cl)(py)]2 · 3(C6H6),17 and [Y(adam,MeO2NO)(N(SiHMe2)2)].7,26,42 The Y-Cl and Y-O(DME) are in the ranges where these distances are found in yttrium complexes.43-45 Crystals of 6 · C7H8 and 7 were grown from toluene solutions. Both complexes are six-coordinate by the oxygen and nitrogen atoms of the tBu2O2NN′ ligand and by the carbon and nitrogen atoms of the hydrocarbyl ligand. The coordination geometry in both complexes is best described as distorted octahedral. ORTEP drawings of 6 and 7 are shown in Figures 7 and 8, respectively, and relevant bond lengths and angles are shown in Table 3. The average Y-O distances of 2.1489(19) and 2.1508(19) Å to the phenoxide ligand in 6 and 7, respectively, are similar and are in the range found for 3 and 4. The Y-N(1) and Y-N(2) distances (2.5683(2) and 2.523(2) Å, respectively) in 6 compare with the corresponding distances (2.568(2) and 2.538(2) Å) in 7. The Y-C and Y-N distances to the bidentate hydrocarbyl ligand are similar in both complexes

6 · C7H8 Y(1)-O(1) Y(1)-O(2) Y(1)-N(1) Y(1)-N(2) Y(1)-N(3) Y(1)-C(30) Y(1)-C(37) O(1)-Y(1)-N(3) O(2)-Y(1)-N(3) O(1)-Y(1)-O(2) O(1)-Y(1)-N(1) O(1)-Y(1)-N(2) O(2)-Y(1)-N(1) O(2)-Y(1)-N(2) O(1)-Y-C(30) O(2)-Y-C(30) N(1)-Y-C(30) N(2)-Y-C(30) N(2)-Y-N(3)

2.139(18) 2.1585(19) 2.563(2) 2.523(2) 2.518(2) 2.439(3) 90.45(7) 87.77(7) 146.48(8) 77.37(7) 102.60(7) 80.20(7) 92.31(8) 105.99(9) 104.59(9) 156.22(9) 87.02(9) 155.43(8)

7 Y(1)-O(1) Y(1)-O(2) Y(1)-N(1) Y(1)-N(2) Y(1)-N(3) Y(1)-C(30) Y(1)-C(37) O(1)-Y(1)-(3) O(2)-Y(1)-(3) O(1)-Y(1)-(2) O(1)-Y(1)-(1) O(1)-Y(1)-(2) O(2)-Y(1)-(1) O(2)-Y(1)-(2) O(1)-Y-C(37) O(2)-Y-C(37) N(1)-Y-C(37) N(2)-Y-C(37) N(2)-Y-N(3)

2.1430(19) 2.1586(18) 2.568(2) 2.538(2) 2.503(2) 2.482(3) 90.84(7) 84.94(7) 147.73(8) 77.80(7) 101.21(8) 79.67(7) 92.30(7) 102.97(9) 105.93(8) 160.63(9) 91.19(9) 160.97(8)

(2.439(3) and 2.518(2) Å in 6 and 2.482(3) and 2.503(2) Å in 7) and are in the range found for other yttrium hydrocarbyl complexes.46,47 The structure of Li2(µ4-O)[Y(tBu2O2NN′)(CH2SiMe3)]2 (Figure 9, Table 4) has a square-like Y2Li2 array linked by four oxygen atoms of the (tBu2O2NN′) ligands with a µ4-O ligand lying in the middle of the Y2Li2 plane. The coordination sphere of the yttrium atoms is completed by the two nitrogen atoms of the tBu2 O2NN′ ligand and the carbon atom of the alkyl ligand and displays distorted octahedral geometry. The Y-O, Y-N, and Y-C distances are similar to the corresponding distances in the complexes mentioned above and compare with those found in yttrium complexes reported in the literature.7,17,46,47 The Li-O distances are in the range usually found between Li+ cations and neutral oxygen donor

Figure 7. ORTEP diagram of [YtBu2O2NN′)(CH2C6H4NMe2)](C7H8) (6 · C7H8), with 40% probability ellipsoids.

(43) Wang, J.; Sun, H.; Yao, Y.; Zhang, Y.; Shen, Q. Polyhedron 2008, 27, 1977. (44) Williams, C. E.; Sinenkov, M. A.; Fukin, G. K.; Sheridan, K.; Lynam, J. M.; Trifonov, A. A.; Kerton, F. M. Dalton Trans. 2008, 3592. (45) Arndt, S.; Trifonov, A. A.; Spaniol, T. P.; Okuda, J.; Kitamura, M.; Takahashi, T. J. Organomet. Chem. 2002, 647, 158. (46) Marinescu, S. C.; Agapie, T.; Day, M. W.; Bercaw, J. E. Organometallics 2007, 26, 1178.



Figure 9. ORTEP diagram of [(Y(tBu2O2NN′)(CH2SiMe3))2(µ-O)(µ-Li)2], 8, with 40% probability ellipsoids. Table 4. Selected Bond Lengths [Å] and Angles (deg) for 8 and 9 8 Y(1)-O(1) Y(1)-O(2) Y(1)-O(3) Y(1)-N(1) Y(1)-N(2)

2.210(3) 2.250(3) 2.1613(6) 2.544(4) 2.596(4)

Y(1)-Li(1) Y(1)-Li(1)#1 Y(1)-C(31)

90.45(7) 87.77(7) 146.48(8)

O(1)-Y(1)-O(3) O(2)-Y(1)-O(3) O(1)-Y(1)-O(2) O(1)-Y(1)-N(1) O(1)-Y(1)-N(2) O(2)-Y(1)-N(1) O(2)-Y(1)-N(2) O(1)-Y-C(31) O(3)-Y(1)-N(2) N(2)-Y-N(3) C(31)-Y(1)-N(1) N(1)-Y-C(30) N(2)-Y-C(30)

81.99(8) 82.23(8) 154.42(11) 78.85(10) 90.80(11) 81.39(11) 97.36(11) 93.32(14) 160.15(8) 155.43(8) 162.06(14) 156.22(9) 87.02(9)

9 Y(1)-O(1) Y(1)-O(2) Y(1)-N(1) Y(1)-N(2) Y(1)-N(3) Y(1)-N(4) N(3)-C(30) C(30)-C(31) C(31)-C(32) N(4)-C(32)

2.147(2) 2.110(2) 2.595(3) 2.552(3) 2.306(3) 2.377(3) 1.321(5) 1.398(5) 1.392(5) 1.329(5)

O(1)-Y(1)-O(2)

115.79(9) 75.84(9) 94.40(10) 77.17(9) 127.84(10) 146.64(9) 152.24(10) 160.97(8)

O(1)-Y(1)-N(4) N(1)-Y-N(3)

ligands. The [(Y(tBu2O2NN′)(CH2SiMe3)2(O)] moiety is thus best formulated as an ate-Y dimer with a bridging oxo ligand. Diffraction-quality crystals of 9 were obtained by slow evaporation of a hexane solution. The coordination geometry can be described as a distorted octahedron, with the atoms O(1), N(2), and N(3) occupying one triangular face and O(2), N(1), and N(4) forming a staggered triangular face on the other side of the central yttrium atom (Figure 10). Relevant bond lengths and angles are shown in Table 4. The average Y-O bond distance of 2.128(2) Å and the Y-N distances of 2.306(3) and 2.377(3) Å to the phenoxide ligand are in the range found for other bis(phenoxide) yttrium complexes.7,17,47 The bidentate [N(H)C(CH3)C(H)C(C6H4CH2NMe2)N(H)] ligand is symmetrically coordinated to yttrium, as shown by the bond distances Y-N(3) and Y-N(4) (2.306(3) and 2.377(3) Å´, respectively) and the Y-N(3)-C(30) and Y-N(4)-C(32) angles of 132.8(3)° and 130.1(3)°, respectively. In the heterocycle the bond distances N(3)-C(30), C(30)-C(31), C(31)-C(32), and N(4)-C(32) are within the range of values (47) Cai, C.-X.; Toupet, L.; Lhemann, C. W.; Carpentier, J.-F. J. Organomet. Chem. 2003, 683, 131.

Figure 10. ORTEP diagram of [Y(tBu2O2NN′)(κ2-N(H)C(CH3)C(H)C(C6H4CH2NMe2)N(H))], 9, with 40% probability ellipsoids.

typical of single and double bonds, thus reflecting the charge delocalization between all atoms.

Experimental Section General Procedures. All preparations and subsequent manipulations were carried out using standard Schlenk line and drybox techniques in an atmosphere of dinitrogen. THF, toluene, pentane, 1,2-dimethoxyethane, and n-hexane were dried by standard methods and degassed prior to use. Toluene-d8 and benzene-d6 were dried over Na and distilled. 2,4-Di-tert-butylphenol was sublimed prior to use. The bis(phenolate) ligand was prepared by literature procedures.48 TiCl3(THF)349 and YCl3(THF)2.550 were prepared as described in the literature. Nuclear magnetic resonance (NMR) spectra were recorded on a Varian 300 MHz spectrometer. 1H and 13C NMR spectra were referenced internally to residual protio-solvent (1H) or solvent (13C) resonances and reported relative to tetramethylsilane (δ 0). The assessment of proton and carbon resonances has been based on COSY and HSQC experiments. EPR experiments were run in a Bruker EMX EPR spectrometer and calibrated using Perilene+•/H2SO4 as internal standard. The magnetic susceptibility was determined from powder samples of the compounds using a Sherwood Scientific magnetic susceptibility balance based on Evans’ method. Diamagnetic corrections for the diamino-bis(phenolate) ligand were applied. Carbon, hydrogen, and nitrogen analyses were performed in-house using an EA110 CE Instruments automatic analyzer. [TiCl(tBu2O2NN′)(THF)] (1). A solution of H2(tBu2O2NN′) (1.05 g, 2.00 mmol) in THF was added to a suspension of NaH (0.11 g, 4.40 mmol) in the same solvent at -30 °C. The temperature was allowed to rise slowly to room temperature and further stirred for 2 h. The colorless solution of Na2(tBu2O2NN′) obtained was filtered through Celite and added to a suspension of TiCl3(THF)3 (0.74 g, 2.00 mmol) in THF at -80 °C. The mixture was strirred for 4 h and allowed to reach room temperature slowly. The orange solution obtained was evaporated to dryness, and the residue was extracted in Et2O and filtered. Evaporation of the solution to dryness led to a microcrystalline orange solid in 83% yield (1.13 g, 1.67 mmol). Crystals suitable for X-ray (48) Tshuva, E. Y.; Versano, M.; Goldberg, I.; Kol, M.; Weitman, M.; Goldschmidt, Z. Inorg. Chem. Commun. 1999, 2, 371. (49) Manzer, L. E. Inorg. Synth. 1982, 21, 135. (50) Hermann, W. A. Synth. Methods Organomet. Inorg. Chem. 1997, 6, 34.

3456 Organometallics, Vol. 28, No. 12, 2009 diffraction were obtained from hexane at -20 °C. µeff(20 °C) ) 1.46 µB. Anal. Calcd for C42H72N2O4Cl: C 67.05; H 9.64; N 3.72. Found: C 67.05; H 10.40; N 3.91. [TiCl(tBu2O2NN′)(py)] (2). The initial procedure described for 1 was used to prepare 2. After addition of TiCl3(THF)3, pyridine (0.40 mL, 5 mmol) was added to the reaction mixture. The temperature was allowed to attain room temperature and a purple solution formed. The solvent was evaporated to dryness and the residue was extracted in Et2O, filtered, and evaporated to dryness, leading to a purple crystalline solid in 89% yield (1.22 g, 1.78 mmol). Crystals suitable for X-ray diffraction were obtained from toluene at -20 °C. EPR (3 × 10-3 M in hexane, 90 K): g ) 1.976. µeff(20 °C) ) 1.58 µB. Anal. Calcd for C39ClH59N3O2Ti: C, 67.21; H, 8.99; N, 6.35. Found: C, 67.09; H, 9.27; N, 6.06. [Y(tBu2O2NN′)Cl(DME)] (3). Addition of a solution of K2tBu2 ( O2NN′) (2.89 g, 4.81 mmol) in 1,2-dimethoxyethane (DME) to a solution of YCl3(THF)2.5 (1.81 g, 4.81 mmol) in the same solvent at room temperature resulted, after stirring overnight, in a white suspension. After separation of the potassium chloride, the solvent was removed under vacuum, giving a white solid, which was further washed with hexane. Yield: 80% (2.84 g, 3.85 mmol). X-ray quality crystals of 3 were grown by slow concentration of a DME solution. 1H NMR (δ, ppm, C6D6): 7.67 (2H, d, JHH ) 2.4 Hz, 4-C6H2tBu2), 7.15 (d, 2H, d, JHH ) 2.4 Hz, 6-C6H2tBu2), 4.08 (d, 2H, JHH ) 12.6 Hz, NCH2Ph), 3.29 (4H, NCH2CH2N(CH3)2 + 4H, CH3OCH2CH2OCH3), 3.18 (s, 6H, CH3OCH2CH2OCH3), 2.91 (d, 2H, JHH ) 12.6 Hz, NCH2Ph), 2.02 (s, 6H, N(CH3)2), 1.77 (s, 18H, 3-C6H2tBu2), 1.45 (s, 18H, 5-C6H2tBu2). 1H NMR (δ, ppm, tol-d8): 7.61 (d, 2H, JHH ) 2.4 Hz, 4-C6H2tBu2), 7.15 (d, 2H, JHH ) 2.4 Hz, 6-C6H2tBu2), 4.06 (d, 2H, JHH ) 12.6 Hz, NCH2Ph), 3.29 (4H, NCH2CH2N(CH3)2 + 4H, CH3OCH2CH2OCH3), 3.18 (s, 6H, CH3OCH2CH2OCH3), 2.89 (d, 2H, JHH ) 12.6 Hz, NCH2Ph), 2.03 (s, 6H, N(CH3)2), 1.76 (s, 18H, 3-C6H2tBu2), 1.45 (s, 18H, 5-C6H2tBu2). 1H NMR (δ, ppm, tol-d8, -70 °C): 7.70, 7.61 (1H, 1H, 4-C6H2tBu2), 7.26, 7.21 (1H, 1H, 6-C6H2tBu2), 4.05, 3.97 (d, d, 1H, 1H, JHH ) 12.6 Hz, JHH ) 12.6 Hz, NCH2Ph), 3.30 (br, 4H, NCH2CH2N(CH3)2 + 4H, CH3OCH2CH2OCH3), 3.02, 2.98 (3H, 3H, CH3OCH2CH2OCH3), 2.83, 2.78 (d, d, 1H, 1H, JHH ) 12.6 Hz, JHH ) 12.6 Hz, NCH2Ph), 2.24, 2.17 (3H, 3H, N(CH3)2), 1.91, 1.76 (s, s, 9H, 9H, 3-C6H2tBu2), 1.53, 1.52 (s, s, 9H, 9H, 5-C6H2tBu2). 13C(1H) NMR (δ, ppm, C6D6): 160.9 (2-C6H2tBu2), 137.1 (5-C6H2tBu2), 136.6 (3-C6H2tBu2), 125.5 (6-C6H2tBu2), 125.1 (4-C6H2tBu2), 124.5 (1-C6H2tBu2), 70.4 (CH2 of DME), 65.9 (NCH2Ph), 59.9 (CH3OCH2CH2OCH3), 59.6 (NCH2CH2NMe2), 50.4 (NCH2CH2NMe2), 47.1 (N(CH3)2), 35.6 (3-C6H2(CMe3)2), 34.3 (5-C6H2(CMe3)2), 32.2 (5-C6H2(CMe3)2), 30.5 (3-C6H2(CMe3)2). Anal. Calcd for C38ClH64N2O4Y: C, 61.90, H, 8.75, N, 3.80. Found: C, 61.51, H, 8.40, N, 3.87. [Y(tBu2O2NN′)(N(SiMe3)2] (4). To a solution of [Y(tBu2O2NN′)Cl(DME)] (0.88 g, 1.20 mmol) in THF was added a solution of KN(SiMe3)2 (0.24 mg, 1.20 mmol) in the same solvent at room temperature. After stirring overnight the potassium chloride was separated by centrifugation and the solvent removed under vacuum. Yield: 82% (0.76 g, 0.92 mmol). 1H NMR (δ, ppm, C6D6): 7.55 (d, 2H, JHH ) 2.7 Hz, 4-C6H2tBu2), 6.96 (d, 2H, JHH ) 2.7 Hz, 6-C6H2tBu2), 3.58 (br, 4H, NCH2Ph), 2.17 (m, 4H, NCH2CH2N(CH3)2), 1.76 (s, 6H, N(CH3)2), 1.67 (s, 18H, 3-C6H2tBu2), 1.40 (s, 18H, 5-C6H2tBu2), 0.45 (s, 18H, N(Si(CH3)3)2). 1H NMR (δ, ppm, tol-d8): 7.54 (d, 2H, JHH ) 2.7 Hz, 4-C6H2tBu2), 6.94 (d, 2H, JHH ) 2.7 Hz, 6-C6H2tBu2), 3.49, 3.27 (d, d, 2H, 2H, JHH ) 12.6 Hz, JHH ) 12.6 Hz, NCH2Ph), 2.17 (m, 4H, NCH2CH2N(CH3)2), 1.76 (s, 6H, N(CH3)2), 1.68 (s, 18H, 3-C6H2tBu2), 1.40 (s, 18H, 5-C6H2tBu2), 0.45 (s, 18H, N(Si(CH3)3)2). 1H NMR (δ, ppm, told8, -70 °C): 7.63, 7.56, (1H, 1H, 4-C6H2tBu2), 7.24, 6.67 (1H, 1H, 6-C6H2tBu2), 4.16, 4.05, 2.84, 2.65 (1H, 1H, 1H, 1H, NCH2Ph), 2.17 (m, 4H, NCH2CH2N(CH3)2), 1.78, 1.69 (s, s, 9H, 9H, 3-C6H2tBu2), 1.54, 1.38 (s, s, 9H, 9H, 5-C6H2tBu2), 0.63, 0.39 (s, s,

Barroso et al. Table 5. Crystallographic Data for 1, 2, and 5 1 2(C38H62ClN2O3Ti) · 3(C4H10O) fw 1578.85 temp (K) 150(2) cryst syst triclinic space group P1j a (Å) 9.7830(12) b (Å) 17.268(2) c (Å) 27.901(4) R (deg) 94.657(4) β (deg) 90.273(5) γ (deg) 90.228(4) V (Å3) 4697.7(11) Z, Dcalc (g cm-3) 2, 1.116 µ(mm-1) 0.279 reflns measd 49 190 unique reflns [R(int)] 17 155 [0.0499] obsd reflns [I > 2σ(I)] 11 407 R1 0.0894 wR2 0.2496 empirical formula

2

5

C39H59ClN3O2Ti C43H66N3O2Ti 685.24 150(2) monoclinic P21/c 16.634(7) 17.251(6) 15.664(4) 90 117.842(17) 90 3975(2) 4, 1.145 0.317 28 518 7246 [0.1285] 3530 0.0538 0.1198

704.89 150(2) triclinic P1j 10.046(4) 11.641(5) 18.246(8) 99.007(17) 90.674(18) 104.869(18) 2033.9(15) 2, 1.151 0.248 27 411 6986 [0.1667] 3392 0.0965 0.2879

9H, 9H, N(Si(CH3)3)2). 13C(1H) NMR (δ, ppm, C6D6): 160.7 (2C6H2tBu2), 137.7 (5-C6H2tBu2), 136.3 (3-C6H2tBu2), 125.8 (6-C6H2t Bu2), 124.4 (4-C6H2tBu2), 124.0 (1-C6H2tBu2), 61.6 (NCH2Ph)), 58.1 (NCH2CH2NMe2), 51.8 (NCH2CH2NMe2), 47.7 (N(CH3)2), 35.5 (3-C6H2(CMe3)2), 34.2 (5-C6H2(CMe3)2), 32.1 (5-C6H2(CMe3)2), 30.7 (3-C6H2(CMe3)2), 6.0 (s, Si(CH3)3). Anal. Calcd for C40H72N3O2Si2Y: C, 62.22, H, 9.40, N, 5.44. Found: C, 62.21, H, 9.37, N, 5.20. [Ti(tBu2O2NN′)(K2-CH2C6H4NMe2)] (5). A solution of LiCH2(2-NMe2)C6H4 (0.14 g, 1.00 mmol) in toluene was added to a solution of [TiCl(tBu2O2NN′)(THF)] (0.68 g, 1.00 mmol) in the same solvent, at -70 °C. The temperature was allowed to rise slowly to room temperature, and the solution was further stirred overnight. The green solution obtained was evaporated to dryness, and the residue was extracted in hexane and filtered off. Evaporation of the solvent to dryness led to 5 as a green microcrystalline solid in 92% yield (0.65 g, 0.92 mmol). Crystals suitable for X-ray diffraction analysis were grown from hexane at -20 °C. µeff (20 °C) ) 1.55 µB. Anal. Calcd for C43H66N3O2Ti: C, 73.27, H, 9.44, N, 5.96. Found: C, 69.66, H, 9.65, N, 5.54 (attempts to obtain good elemental analysis were hampered by the extreme instability of the compound). [Y(tBu2O2NN′)(K2-CH2C6H4NMe2) (6). A solution of LiCH2-(2NMe2)C6H4 (0.054 g, 0.38 mmol) in THF was added at room temperature to a solution of Y(tBu2O2NN′)Cl(DME) (0.28 g, 0.38 mmol) in the same solvent. The mixture was stirred overnight, and the solvent was evaporated to dryness to give a cream powder. After washing with hexane the compound was extracted in toluene and filtered. Removal of the solvent under vacuum led to a pale yellow powder in 78% yield (0.22 g; 0.30 mmol). Diffractionquality crystals were grown by slow evaporation of a toluene solution. 1H NMR (δ, ppm, C6D6): 7.62 (d, 1H, JHH ) 7.5 Hz, C6H4CH2NMe2), 7.55 (d, 2H, JHH ) 2.4 Hz, 4-C6H2tBu2), 7.27 (d, 1H, JHH ) 7.5 Hz, C6H4CH2NMe2), 7.18 (t, 1H, C6H4CH2NMe2), 7.04 (d, 2H, JHH ) 2.4 Hz, 6-C6H2tBu2), 6.93 (t, 1H, C6H4CH2NMe2), 4.10 (s, 2H, CH2C6H4NMe2), 3.80, 2.85 (d, d, 2H, 2H, JHH ) 12.3 Hz, JHH ) 12.3 Hz, NCH2Ph), 2.80 (s, 6H, N(CH3)2), 2.19, 1.91 (m, 2H, 2H, NCH2CH2N(CH3)2), 1.66 (s, 6H, N(CH3)2), 1.50 (s, 18H, 3-C6H2tBu2), 1.44 (s, 18H, 5-C6H2tBu2). Anal. Calcd for C43H66N3O2Y: C, 69.24, H, 8.92, N, 5.63. Found: C, 68.90, H, 8.51, N, 5.71. [Y(tBu2O2NN′)(K2-C6H4CH2NMe2) (7). To a solution of [YCl(tBu2O2NN′)(DME)] (0.53 g, 0.72 mmol) in THF was added dropwise a solution of Li[2-(CH2NMe2)C6H4] (0.10 g, 0.72 mmol) in THF at room temperature, and the solution was stirred for 5 h. The resulting solution was evaporated to give a cream powder, which was extracted into toluene and filtered, and the solution was evaporated to dryness to give a white powder. Yield: 0.53 g (99%).



Table 6. Crystallographic Data for 3 · 0.5(O2C4H10), 4, 6 · (C7H8), 7, 8, and 9 empirical formula fw temp (K) cryst syst, space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z, Dcalc (g cm-3) µ(mm-1) reflns measd unique reflns [R(int)] obsd reflns [I > 2σ(I)] R1 wR2

3 · 0.5(O2C4H10)

4

6

7 · C7H8

8

9

C80H138Cl2N4O10Y2 1564.66 130(2) triclinic P1j 12.782(5) 17.655(6) 19.626(8) 89.74(3) 88.63(2) 85.35(2) 4413(3) 2, 1.178 1.422 43 837 14 343 [0.1518] 7514 0.1366 0.3593

C40H72N32O2Si2Y 772.10 148(2) monoclinic Cc 19.0586(9) 24.5350(13) 10.4449(6) 90 111.207(3) 90 4553.3(4) 4, 1.126 1.366 11 007 5980 [0.0707] 4711 0.0523 0.1043

C43H66N3O2Y 745.90 150(2) monoclinic P21/n 7416(4) 20.4043(7) 17.4481(5) 90 100.166(2) 90 4114.6(2) 4, 1.204 1.454 36 635 7800 [0.0910] 5052 0.0434 0.0886

C50H74N3O2Y 838.03 150(2) monoclinic P21/n 11.6585(4) 17.8023(6) 23.0721(10) 90 100.487(2) 90 4708.6(3) 4, 1.182 1.278 43 907 8609 [0.0830] 5944 0.0451 0.0973

C76H130Li2N4O5Si2Y2 1427.72 108(2) monoclinic C2/c 21.905(6) 18.189(5) 20.000(5) 90 105.134(17) 90 7 692(4) 4, 1.233 1.582 80 574 7016 [0.1448] 3875 0.0534 0.1089

C47H72N5O2Y 828.01 150(2) triclinic P1j 11.2064(4) 15.2939(5) 16.0307(6) 115.518(2) 91.676(2) 111.069(2) 2257.74(14) 2, 1.218 1.333 17 228 7943 [0.0672] 5629 0.0551 0.1116

Diffraction-quality crystals were grown by slow evaporation of a toluene solution. 1H NMR (δ, ppm, C6D6): 7.72 (d, 1H, JHH ) 4.2 Hz, C6H4CH2NMe2), 7.45 (d, 2H, JHH ) 2.4 Hz, 4-C6H2tBu2), 7.26 (t, 1H, C6H4CH2NMe2), 7.20 (d, 1H, JHH ) 4.2 Hz, C6H4CH2NMe2), 7.18 (br, 1H, C6H4CH2NMe2), 7.08 (d, 2H, JHH ) 2.4 Hz, 6-C6H2tBu2), 4.16 (s, 2H, C6H4CH2NMe2), 3.89, 2.83 (d, d, 2H, 2H, JHH ) 12.3 Hz, JHH ) 12.3 Hz, NCH2Ph), 2.46 (s, 6H, N(CH3)2), 2.25, 2.10 (m, 2H, 2H, NCH2CH2N(CH3)2), 1.79 (s, 6H, N(CH3)2), 1.55 (s, 18H, 3-C6H2tBu2), 1.45 (s, 18H, 5-C6H2tBu2). 13 C(1H)NMR (δ, ppm, C6D6): 161.8 (2-C6H2tBu2), 148.2, 138.6, 128.3, 126.1, 125.9, 125.6 (C6H4CH2NMe2), 137.5 (5-C6H2tBu2), 136.5 (3-C6H2tBu2), 126.2 (6-C6H2tBu2), 125.0 (4-C6H2tBu2), 126.0 (1-C6H2tBu2), 68.1 (C6H4CH2NMe2), 65.4 (NCH2Ph), 60.3, 48.7 (NCH2CH2N(CH3)2), 46.6 (N(CH3)2), 45.5 (N(CH3)2), 35.7 (3C6H2(CMe3)2), 34.6 (5-C6H2(CMe3)2), 32.6 (5-C6H2(CMe3)2), 30.9 (3-C6H2(CMe3)2). Anal. Calcd for C43H66N3O2Y · C7H8: C, 71.66, H, 8.90, N, 5.01. Found: C, 70.06, H, 8.68, N, 4.95. Li2(µ4-O)[Y(tBu2O2NN′)(CH2SiMe3)]2 (8). To a solution of [YCl(tBu2O2NN′)(DME)] (0.40 g, 0.54 mmol) in THF was slowly added a solution of LiCH2SiMe3 (0.05 g, 0.54 mmol) in the same solvent, at room temperature. After stirring for 5 h the solution was evaporated to dryness and the residue extracted in toluene and filtered. Removal of the solvent gave a white powder, which was recrystallized from THF to give 8. Yield in crude product, based on Y: 0.38 g (49%). 1H NMR (δ, ppm, C6D6): 7.61 (d, 2H, JHH ) 2.4 Hz, 4-C6H2tBu2), 7.12 (d, 2H, JHH ) 2.4 Hz, 6-C6H2tBu2), 3.74 (d, 2H, JHH ) 12.3 Hz, NCH2Ph), 2.87 (d, 2H, JHH ) 12.3 Hz, NCH2Ph), 2.28, 2.10 (2H, 2H, NCH2CH2N(CH3)2), 1.79 (s, 18H, 3-C6H2tBu2), 1.71 (6H, N(CH3)2), 1.45 (s, 18H, 5-C6H2tBu2), 0.50 (s, 9H, Si(CH3)3), -0.42 (2H, CH2SiMe3). 13C(1H) NMR (δ, ppm, C6D6): 161.7 (2-C6H2tBu2), 136.9 (5-C6H2tBu2), 136.4 (3-C6H2tBu2), 125.6 (6-C6H2tBu2), 124.6 (4-C6H2tBu2), 113.2 (1-C6H2tBu2), 65.4 (NCH2Ph), 60.0, 48.4 (NCH2CH2N(CH3)2), 46.3 (N(CH3)2), 35.7 (3-C6H2(CMe3)2), 34.2 (5-C6H2(CMe3)2), 32.2 (5-C6H2(CMe3)2), 30.6 (3-C6H2(CMe3)2), 25.1 (CH2SiMe3), 4.9 (Si(CH3)3). Anal. Calcd for C76H130Li2N4O5Si2Y2: C, 63.94, H, 9.18, N, 3.92. Found: C, 63.64, H, 9.16, N, 3.99. [Y(tBu2O2NN′)(K2-N(H)C(CH3)C(H)C(C6H4CH2NMe2)N(H))] (9). Excess CH3CN (0.028 g, 0.672 mmol) was added to a solution of [Y(tBu2O2NN′)(C6H4CH2N(CH3)2)], (0.125 g, 0.168 mmol) in toluene at room temperature. The color of the solution changed to yellow immediately. Stirring was continued overnight. The resulting solution was evaporated under vacuum to give a cream powder, which was extracted into hexane. Diffraction-quality crystals were obtained by slow evaporation of a hexane solution. Yield: 0.138 g (99.2%). 1H NMR (δ, ppm, THF-d8): 7.70 (d, 1H, JHH ) 7.24 Hz, C6H4CH2N(CH3)2), 7.52 (m, 1H, C6H4CH2N(CH3)2), 7.42 (m, 1H, C6H4CH2N(CH3)2), 7.40 (m, 1H, C6H4CH2N(CH3)2), 7.34, 7.33 (m, 2H, 4-C6H2tBu2), 7.04, 7.02 (m, 2H, 6-C6H2tBu2), 4.79 (s, 1H,

(NC(PhCH2N(CH3)2)CHC(CH3)NH), 4.35, 3.97, 3.58, 3.17 (d, 4H, JHH ) 12.3 Hz, NCH2Ph), 3.73 (s, 2H, C6H4CH2N(CH3)2), 2.76 (br, 2H, NCH2CH2N(CH3)2), 2.39, 2.38, 2.35 (s, s, s, 3H, 3H, 6H, N(CH3)2), 2.27 (br, 2H, NCH2CH2N(CH3)2), 2.21 (s, 3H, (NC(PhCH2N(CH3)2)CHC(CH3)NH), 1.65, 162 (s, s, 9H, 9H, 3-C6H2tBu2), 1.46, 1.44 (s, s, 9H, 9H, 5-C6H2tBu2). 13C(1H) NMR (δ, ppm, THF-d8): 170.9, 168.8 (NC(PhCH2N(CH3)2)CHC(CH3)NH), 163.2, 162.7 (2-C6H2tBu2), 143.7 (C6H4CH2NMe2), 136.5, 136.2 (5-C6H2tBu2), 135.6, 135.4 (3-C6H2tBu2), 131.6, 129.8, 128.8, 128.3, 127.8 (C6H4CH2NMe2), 126.3, 126.1 (6-C6H2tBu2), 123.9, 123.8 (4-C6H2tBu2), 125.1 (1-C6H2tBu2), 94.3 (NC(PhCH2N(CH3)2)CHC(CH3)NH), 61.9 (C6H4CH2NMe2), 67.1, 64.5 (NCH2Ph), 60.5, 51.9 (NCH2CH2N(CH3)2), 48.1, 46.0, 45.1 (N(CH3)2), 35.9, 35.8 (3-C6H2(CMe3)2), 34.5, 34.5 (5-C6H2(CMe3)2), 32.6, 32.4 (5C6H2(CMe3)2), 31.3, 30.7 (3-C6H2(CMe3)2), 26.8 (NC(PhCH2NMe2)CHC(CH3)NH). Anal. Calcd for C47H72N5O2Y: C, 68.18, H, 8.76, N, 8.46. Found: C, 68.02, H, 8.53, N, 8.07. 1

H NMR Data for [Y(tBu2O2NN′)(K2-NC(CH3)C6H4CH2NMe2] (10). 1H NMR (δ, ppm, C6D6): 7.91 (m, 1H, C6H4CH2NMe2), 7.54 (d, 2H, JHH ) 2.7 Hz, 4-C6H2tBu2), 7.24 (m, 1H, C6H4CH2NMe2), 7.13 (m, 1H, C6H4CH2NMe2), 7.10 (m, 1H, C6H4CH2NMe2), 7.06 (d, 2H, JHH ) 2.7 Hz, 6-C6H2tBu2), 3.75 (d, 2H, JHH ) 9.6 Hz, NCH2Ph), 3.72 (d, 2H, JHH ) 9.6 Hz, NCH2Ph), 2.41 (2H, NCH2CH2N(CH3)2), 2.25 (s, 6H, N(CH3)2), 2.10 (2H, NCH2CH2N(CH3)2), 1.65 (s, 6H, N(CH3)2), 1.50 (s, 18H, 3-C6H2tBu2), 1.46 (s, 3H, NdC(CH3)), 1.44 (s, 18H, 5-C6H2tBu2). General Procedures for X-ray Crystallography. Pertinent details for the individual compounds can be found in Tables 5 and 6. Crystallographic data for compounds 1-9 were collected using graphite-monochromated Mo KR (R ) 0.71073 Å) on a Bruker AXS-KAPPA APEX II area detector diffractometer equipped with an Oxford Cryosystem open-flow nitrogen cryostat, and data were collected at 150 K. Cell parameters were retrieved using Bruker SMART software and refined using Bruker SAINT on all observed reflections. Absorption corrections were applied using SADABS.51 The structures were solved by direct methods using either SHELXS97,52 SIR 97,53 or SIR200454 and refined using full-matrix least(51) SADABS: Area-Detector Absorption Correction; Siemens Industrial Automation, Inc., Madison, WI, 1996. (52) Sheldrick, G. M. SHELXL-97: A program for refining crystal structures; Univ. of Go¨ttingen: Germany, 1998. (53) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Sparna, R. J. Appl. Crystallogr. 1999, 32, 115. (54) Burla, M. C.; Caliandro, R.; Camalli, M.; Cascarano, G.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Sparna, R. J. Appl. Crystallogr. 2005, 38, 381.

3458 Organometallics, Vol. 28, No. 12, 2009 squares refinement against F2 using SHELXL-97.52 All programs are included in the package of programs WINGX-version 1.64.05.55 Crystals of 1 have been obtained from Et2O at -20 °C with two molecules and one cocrystallized solvent molecule in the unit cell. One of the molecules presents disorder in one tBu fragment, which was modeled and gave 40% and 60% occupancy. The same complex was isolated from hexane,56 and the data collected are not included here due to strong disorder in the crystal. Complexes 2 and 5 were obtained from toluene and hexane, respectively. Crystals of 5 have low quality and poor diffracting power, presenting disordered tBu moieties (40/60%). Crystals of 3 have low quality and poor diffracting power; even so, the structure was unequivocally determined and is in agreement with the remaining characterization data. In compounds 4 and 7 high anisotropic displacement parameters were found in one of the tBu substituents, and a disorder model was applied refining anisotropically and converging to occupancies of 50/50% and 80/20%, respectively. In compound 8, high anisotropic displacement parameters were found in two of the tBu substituents, and a disorder model was (55) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565. (56) From hexane, the complex crystallizes in the triclinic system, space group P, with cell parameters a ) 9.865(3) Å, b ) 17.448(4) Å, c ) 28. 461(6) Å, R ) 78.799(13)°, β ) 83.304(11)°, γ ) 88.800(11)°, V ) 4772(2) Å3.

Barroso et al. applied refining anisotropically and converging to occupancies of 54/46% and 61/39%, respectively. All non-hydrogen atoms were refined anisotropically (except in 5 due to the poor quality of the crystal), and all hydrogen atoms were placed in idealized positions and allowed to refine riding on the parent carbon atom. The molecular structures were drawn with ORTEP3 for Windows.57 Data for complexes 1-9 were deposited in CCDC under the deposit numbers CCDC 720956-720964 and can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.uk/data_request/cif.

Acknowledgment. The authors thank Fundaçaõ para a Cieˆncia e a Tecnologia, Lisbon, Portugal, for funding (PTDC/ QUI/66187/2006, SFRH/BD/28762/2006). Supporting Information Available: Tables with atomic coordinates of all optimized species. X-ray crystallographic data for compounds 1-9 are available as an electronic file in cif format. This material is available free of charge via the Internet at http://pubs.acs.org. OM9001389 (57) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.

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