Calix[4] - American Chemical

May 8, 2012 - Australian Synchrotron MX1 beamline (3 and 4·2PhMe) at 100 K ... empirically corrected for absorption with SADABS.26 With the MX1...
0 downloads 0 Views 3MB Size
Download PDF
Article pubs.acs.org/Organometallics

Rare-Earth Metalation of Calix[4]pyrrole/Calix[4]arene Free of Alkali-Metal Companions Glen B. Deacon,*,† Michael G. Gardiner,‡ Peter C. Junk,*,† Josh P. Townley,† and Jun Wang†,§ †

School of Chemistry, Monash University, Victoria 3800, Australia School of Chemistry, University of Tasmania, Private Bag 75, Hobart, Tasmania 7001, Australia § School of Chemistry and Material Science, Xiaogan University, Hubei 432000, People's Republic of China ‡

S Supporting Information *

ABSTRACT: The redox transmetalation/protolysis (RTP) reactions of ytterbium or neodymium metal with calix[4]H4 (5,11,17,23-tetra-tert-butylcalix[4]arene-25,26,27,28tetrol) in the presence of bis(pentafluorophenyl)mercury under ultrasonication yielded [LnIII(calix[4]H)(thf)]2 (1, Ln = Yb; 2, Ln = Nd). The characterization of both 1 and 2, including an X-ray single-crystal structural determination for 2, suggests triple deprotonation of the macrocyclic ligand on metalation. The related RTP reaction of H4N4Et8 (meso-octaethylcalix[4]pyrrole) with ytterbium metal and Hg(C6F5)2 at ambient temperature, however, resulted in quadruple deprotonation and afforded the ytterbium(II) calix[4]pyrrolide complex [Yb2(N4Et8)(thf)4] (3) in good yield. Subsequent oxidation of 3 by dioxygen generated the novel tetranuclear ytterbium(III) complex [Yb4(μ-O)2(N4Et8)2(thf)2] (4). The structures of the ytterbium(II) complex 3 and the ytterbium(III) complex 4 incorporate endo (3) and endo/exo (4) pyrrolide sandwich and half-sandwich units, respectively, with metal centers η1 bound by nitrogen and η5 bonded by pyrrolide rings. The RTP reaction of lanthanum metal using diphenylmercury in place of bis(pentafluorophenyl) mercury gave the triply deprotonated and N-confused pyrrolide (with an alkyl substituent of one pyrrolide ring migrated to a β-position) macrocyclic complex [La2(HN3N′Et8)2] (5). The triple deprotonation of the macrocyclic ligand H4N4Et8 was also achieved through its reaction with 3 molar equiv of potassium metal, giving colorless crystals of [{K3(HN4Et8)(thf)(PhMe)2}n] (6). However, an attempt to isolate the corresponding partially deprotonated calix[4]pyrrolide ytterbium(III) complex through the metathesis reaction of potassium precursor 6 with ytterbium triiodide was unsuccessful.

■

Figure 1. (a) H4N4Et8 (meso-octaalkylcalix[4]pyrrole) and (b) calix[4]H4 (5,11,17,23-tetra-tert-butyl-calix[4]arene-25,26,27,28-tetrol).

ligands.2 The tetradeprotonated calix[4]pyrrole ligands tend to have companions of other countercations (e.g., alkali-metal cations) together with Ln3+ to balance the higher negative charge (4−) of the macrocycle ([N4R8]4−). Indeed, the reported alkalimetal-free rare-earth-metal complexes of calix[4]pyrroles are rare.1c,g,k The majority highlight the retention of alkali metals: e.g., [NaLnIII(N4R8)(thf)3],1e [Li3LnII(N4R8)Cl(thf)3],1h and [Li2LnIII2(N4R8)Cl4(thf)4].1f The additional alkali-metal companions are considered to be disadvantageous in the derivatization of rareearth-metal complexes, since they could cause distractions from wanted reactions. These alkali metals could act as additional reaction centers to complicate the chemical reactivity and catalytic activity studies at the rare-earth-metal centers. Surprisingly, little has been explored so far to overcome the phenomenon by using other syntheses which exclude alkali-metal reagents. The modification on calix[4]pyrrole by methylation of a pair of alternate pyrrole rings on nitrogen atoms led to the methylated calix[4]pyrrole H2N4(Me)2R8.3 This afforded the divalent ligand [N4(Me)2R8]2−, which provides ready access to alkalimetal-free rare-earth-metal species and more straightforward derivatization.4 However, the modification on the calixpyrrole

is interesting, due to its resembling the well-known and ubiquitous structural feature of metallocenes from cyclopentadienyl

Received: November 11, 2011 Published: May 8, 2012

INTRODUCTION Octaalkylcalix[4]pyrroles H4N4R8, also called porphyrinogens, have shown a strong ability to stabilize rare-earth metals with a sandwich substructural unit of two η5 bonds between a pair of alternate pyrrolide rings and the metal center (Figure 1).1 This

© 2012 American Chemical Society

3857

dx.doi.org/10.1021/om2011134 | Organometallics 2012, 31, 3857−3864

Organometallics

Article

involves multistep reactions and tedious chromatography to purify the ligand.3 Calix[4]arene macrocycles have obviously experienced a similar situation in their related rare-earth coordination chemistry.5 The research in this field has favored those ligands with substituents on some oxygen atoms on the lower rim: e.g., dianionic di-Oalkylcalix[4]arenes.6 Modifications or functionalization have also been seen often on the upper rim: e.g., p-sulfonatocalix[4]arene.7 In this case, coordination with rare-earth metals often occurs with functional groups rather than phenolic oxygen atoms on the lower rim. Lanthanoid complexes of anionic calix[4]arene without more reactive functional groups and/or modification on the phenolic oxygen atoms are relatively rare species.8 Given the success in using redox transmetalation/protonolysis reactions (RTP reactions) to achieve alkali-metal-free rare-earth-metal compounds for aryloxide-, amide-, (form)amidinate-, pyrazolate-, and cyclopentadienyl-related ligand systems,9 we have started examining RTP reactions for the nonmodified calix[4]arene and calix[4]pyrrole ligand systems that also bear NH/OH atom groups of heterocycles and phenols and report the synthesis and structures of both lanthanoid(II) and -(III) complexes.

■

RESULTS AND DISCUSSION The redox transmetalation/protolysis (RTP) reactions of ytterbium or neodymium metal with calix[4]H4 (5,11,17,23-tetra-tertbutylcalix[4]arene-25,26,27,28-tetrol) in the presence of bis(pentafluorophenyl)mercury were induced by ultrasonication. The reactions approach completion in 3 days, after which time yellow crystalline 1 ([{Ln(calix[4]H)(thf)}2], Ln = Yb) and light blue 2 (Ln = Nd) were isolated in moderate yield (eq 1).

Figure 2. Molecular structure of 2·2thf shown with 50% thermal ellipsoids. Lattice thf molecules and all hydrogen atoms connected to carbon atoms are omitted for clarity. Selected distances (Å) and angles (deg): Nd1−O1 = 2.414(3), Nd1#−O1 = 2.325(3), Nd1−O2 = 2.172(3), Nd1−O3 = 2.643(4), Nd1−O4 = 2.147(3), Nd1−O5 = 2.534(3); Nd1−O1−C25 = 109.7(2), Nd1−O2−C26 = 157.6(3), Nd1−O3−C27 = 115.7(3), Nd1−O4−C28 = 159.0(3), O1−Nd1− O3 = 145.54(9), O2−Nd1−O4 = 124.30(11). Symmetry code: for Nd(1)#, 1 − x, 1 − y, 1 − z.

2Ln + 2calix[4]H4 + 3Hg(C6F5)2 + 2thf → [{Ln(calix[4]H)(thf)}2 ] + 6C6F5H + 3Hg Ln = Yb (1), Nd (2)

the calixarene ligand, the Nd1−O3 bond distance (2.643(4) Å) is remarkably longer than those of Nd1−O2 (2.172(3) Å) and Nd1−O4 (2.147(3) Å). It is also significantly longer than those of the bridging phenolate oxygen donors: Nd1−O1 (2.414(3) Å) and Nd1−O1# (2.325(3) Å). The bond length difference is consistent with the oxygen O3, the farthest oxygen donor from the central Nd2O2 core, bearing a proton. Indeed, this was located in the X-ray crystal structure refinement. Further, the Nd1−O3−C27 angle (115.7(3)°) is much more acute than Nd1− O2−C26 (157.6(3)°) and Nd1−O4−C28 (159.0(3)°). These bond length and bond angle relationships are comparable with the corresponding bond lengths and angles in the related sevencoordinate [{Eu(calix[4]H)(dmf)2}2] (e.g., Eu1−O1 = 2.395(6), Eu1−O1# = 2.332(5), Eu1−O2 = 2.143(6), Eu1−O3H = 2.558(6), and Eu1−O4 = 2.150(7) Å).8 Although Eu3+ is smaller than Nd3+,10 the effect on Ln−O distances is offset by the higher coordination number of the Eu complex. The reaction of ytterbium metal with Hg(C6F5)2 and mesooctaethylcalix[4]pyrrole (H4N4Etg) at ambient temperature gave the orange crystalline calixpyrrolide complex [Yb2(N4Et8)(thf)4] (3) in good yield (eq 2).

(1)

Nearly identical IR spectra of 1 and 2 are consistent with the same ligation for each. Greatly diminished O−H stretching bands compared with those of the free ligand in the infrared spectra support a partial deprotonation of calix[4]H4. The paramagnetic effect of the metal prevents 1H NMR characterization of 1, but the identity was confirmed by high-resolution mass spectrometry. However, the 1H NMR resonances of 2, though broad, are assignable and consistent with the above composition. The constitutions of both complexes were further supported by metal analyses, which are a good measure of bulk purity as substantial samples are used. Satisfactory microanalyses could not be obtained for any of the lanthanoid complexes 1−5 by contrast with the K complex 6, suggesting either combustion problems or decomposition during international travel to the analysis service. A specific example of the problem is discussed with 3 (below). An X-ray single-crystal structure reveals that 2 was isolated originally as 2·2thf, but the two thf molecules of crystallization are lost during vacuum drying, as indicated by both the 1H NMR spectrum and the metal analysis. Compound 2 crystallizes in the monoclinic space group P21/c and adopts a dinuclear form (Figure 2). The tetradentate calix[4]arene caps the metal center with its four oxygen donors. One of the phenolate oxygen atoms of each macrocyclic unit bridges two neighboring metals, forming a planar Nd2O2 core. An inversion center lies at the center of this four-memberedring core. A thf molecule completes the coordination sphere of the six-coordinate metal center. Of the Nd−O bonds involving

2Yb + H4N4Et8 + 2Hg(C6F5)2 + 4thf → [Yb2 (N4Et8)(thf)4 ] + 4C6F5H + 2Hg 3

(2)

The divalent ytterbium complex 3 was formed through complete deprotonation of the calix[4]pyrrole ligand with two ytterbium metal atoms stabilized in the macrocyclic cavity (see 3858

dx.doi.org/10.1021/om2011134 | Organometallics 2012, 31, 3857−3864

Organometallics

Article

structural discussion below). 3 is stable under inert gas; however, on exposure to dry air, it undergoes oxidation, forming yellow crystalline 4 (eq 3). 2[Yb2 (N4Et8)(thf)4 ] + O2 → [Yb4 (μ‐O)2 (N4Et8)2 (thf)2 ] + 6thf 4

(3)

In reference to chemistry of the triply deprotonated species HN4Et8 below, there is no metal/proton redistribution between the fully deprotonated and the unprotonated macrocycle when 3 is mixed with H4N4Et8 in C7D8. 1H NMR monitoring of the solution shows that partially deprotonated intermediate species are not detectable. Complex 3 is soluble in benzene/toluene hydrocarbon solvents and moderately soluble in thf. The NMR spectroscopic characterization supports its constitution of calix[4]pyrrolide and coordinated thf ligand molecules with expected correlations visible in 2D (COSY/HMQC) spectra. However, loss of about half of the thf molecules during vacuum drying was evident from the 1H NMR spectrum. The partial solvation loss was further confirmed by metal analysis. An attempted microanalysis of 3 did not correspond with 3−2thf (indicated by Yb analysis and 1H NMR) or 3−4thf but agreed well with desolvated 4, the oxidation product of 3. UV−vis spectroscopy supports the ytterbium(II) identity of the compound with an f−d absorption at ∼400 nm. Complex 4 is not soluble in hydrocarbon solvents, thus preventing solution NMR characterization. The composition was confirmed by high-resolution mass spectrometry. The metal analysis indicated loss of toluene of crystallization on drying. The structures of both complexes 3 and 4 were determined by X-ray single-crystal crystallography (see below). Complex 3 is a dinuclear species and adopts a monomeric form in the solid state (Figure 3). The macrocycle adopts a 1,3alternate conformation. Both ytterbium atoms reside inside the macrocyclic cavity on either side of the average N4 plane, each metal being bound in an η5:η1:η5:η1 manner. Thus, one ytterbium atom features η5 bonding by the pair of alternate pyrrolide units and σ binding by the nitrogen donor atoms of the other pair of alternate pyrrolide units, and the bonding is reversed for the other ytterbium. The exposed face of each metal atom is covered by coordination of a pair of thf molecules, leading to overall 10coordination. The Yb−N bond length (2.643(5) Å) in 3 is shorter than Sm−N (2.748(4) Å) in [Sm2(N4Et8)(thf)4],1g consistent with the metal size difference.10 However, the Yb−centroid(pyr ring) distance (2.753 Å) is close to that in the samarium congener (2.768 Å),1g indicating that the labile η5 bond is controlled by the cavity dimension rather than the Ln2+ size. In comparison with the mononuclear complex [Yb{N4(Me)2Et8}(thf)],4g where the metal sits deeper in the macrocycle, the Yb−N length in 3 is longer (compared with the mean 2.478 Å for the former). The same trend exists also for the Yb− centroid(pyr ring) distance (2.753 Å) of 3, which is longer than those (2.616, 2.644 Å) in the former, the difference lying well outside that expected for the coordination number difference. The YbII···YbII intermetallic distance (3.2503(11) Å) between two divalent atoms is remarkably shorter than those reported for any dinuclear or polynuclear ytterbium(II) and -(III) compounds11 and is much less than twice the metallic radius (1.94 Å)12a or the covalent radius (1.87 Å).12b,c The short intermetallic distance results probably from the constraints imposed on the two metal

Figure 3. (a) Molecular structure of 3 shown with 30% thermal ellipsoids. Hydrogen atoms are omitted for clarity, and the bond between the metal and the centroid is shown as a dashed line. Selected distances (Å) and angles (deg): Yb(1)−centroid(ring of N(1)) = 2.753, Yb(1)−O(1) = 2.473(4), Yb(1)#−N(1) = 2.643(5); centroid(ring of N(1))−Yb(1)−centroid(ring of N(1)#) = 152.76, N(1)− Yb(1)#−N(1)# = 110.0(2). Symmetry code: for Yb(1)#, y − 1/4, 1/4 − x, 1 /4 − z; for N(1)# and O(1)#, −x, 1/2 − y, z. (b) ChemDraw structural moiety showing the bonding mode (η5:η1:η5:η1 between Yb and the macrocycle in 3).

centers by the cavity of the calix[4]pyrrole rather than from a specific YbII···YbII interaction. Very short SmII···SmII distances for [Sm2(N4Et8)(OEt2)2] (3.3159(5) Å)1c and [Sm2(N4Et8)(thf)4] (3.4417(9) Å)1g were observed previously. Tetranuclear ytterbium(III) complex 4 adopts a dimeric structure in the solid state (Figure 4). Two endo-cavity-bound eight-coordinate ytterbium centers Yb1, Yb1# are each η5:η1:η1:η1 bound to a macrocycle. A μ3-O2−oxide and a thf molecule also occupy the coordination environment of each endo-cavity-bound ytterbium center. The two exo-cavity-bound ytterbium centers are each sandwiched by two adjacent pyrrolide rings from two different macrocyclic units. Both η5 sandwiched eight-coordinate ytterbium centers Yb2, Yb2# are doubly bridged by two oxygen centers, forming the central four-membered Yb2O2 metallacycle. The Yb−N bond lengths (2.410(4), 2.302(4), and 2.347(4) Å) in ytterbium(III) complex 4 are shorter than those in the mononuclear ytterbium(II) complex [Yb{N4(Me)2Et8}(thf)] (mean 2.478 Å)4g and those in 3 (2.643(5) Å), consistent with 3859

dx.doi.org/10.1021/om2011134 | Organometallics 2012, 31, 3857−3864

Organometallics

Article

that of the eight-coordinate [{Yb(C5H5)(μ2-N2Ph2)(thf)}2] (3.301(3) Å), which is the shortest YbIII···YbIII distance previously reported.11k The similar RTP reactions of neodymium or lanthanum with meso-octaethylcalix[4]pyrrole and Hg(C6F5)2 at ambient temperature gave insoluble and unidentifiable slurries. However, the replacement of bis(pentafluorophenyl)mercury with diphenylmercury in the RTP reaction of lanthanum gave the colorless complex [La2(HN3N′Et8)2] (5) (Figure 5: ChemDraw

Figure 5. ChemDraw structure of (HN3N′Et8)3−.

structure of (HN3N′Et8)3−). The very low yield isolation of 5 prevented characterization other than by X-ray crystallography. The molecular structure of 5 features a dinuclear form with an N-confused pyrrolide ring in each macrocycle unit (Figure 6).

Figure 4. (a) Molecular structure of 4·2PhMe shown with 50% thermal ellipsoids. Hydrogen atoms and lattice toluene molecules are omitted for clarity, and the bond between the metal and the centroid is shown as a dashed line. Selected distances (Å) and angles (deg): Yb(1)−N(1) = 2.410(4), Yb(1)−N(2) = 2.302(4), Yb(1)−N(4) = 2.347(4), Yb(1)−centroid (ring of N(4)) = 2.351, Yb(1)−O(1) = 2.504(4), Yb(1)−O(2) = 2.286(3), Yb(2)−O(2) = 2.216(3), Yb(2)#− O(2) = 2.196(4), Yb(2)−centroid (ring of N(4)) = 2.472, Yb(2)− centroid (ring of N(1)#) = 2.443; N(2)−Yb(1)−N(4) = 161.65(14), centroid (ring of N(4))−Yb(2)−centroid (ring of N(1)#) = 147.78. Symmetry code: for Yb(1)#, Yb(2)#, and N(1)#, 1 −x, −y, −z. (b) ChemDraw moiety structure showing the bonding mode (η5:η1:η1:η1 between Yb(1) or Yb(1)# and the macrocycle in 4·2PhMe).

Figure 6. Molecular structure of 5·4thf shown with 50% thermal ellipsoids. Hydrogen atoms connected to carbon atoms and lattice thf molecules are omitted for clarity, and the bond between the metal and the centroid is shown as a dashed line. Selected distances (Å) and angles (deg): La(1)−centroid(ring of N(1)) = 2.587, La(1)− centroid(ring of N(3)) = 2.685, La(1)−N(2) = 2.501(3), La(1)− N(4) = 2.506(3), La(1)−N(1)# = 2.528(3), centroid(ring of N(1))− La(1)−centroid(ring of N(3)) = 167.86, N(2)−La(1)−N(4) = 130.10(9). Symmetry code: for La(1)# and N(1)#, 2 − x, 1 − y, −z.

different metal radii sizes of different oxidation states and coordination numbers. The mean Yb−O(oxide) bond distance (2.278 Å) is near that in seven-coordinate [Yb4(p-HC6F4NC2H4NEt2)(O)2(CCPh)4(thf)2] also having μ3-O2−ligands (mean 2.190 Å),13 allowing for the coordination number difference. Due to the radius of Yb3+ being smaller than that of Yb2+, each ytterbium(III) atom (Yb(1)/Yb(1)#) sits deep in the cavity and relatively close to the mean plane of the four meso-C centers (0.437(2) Å), in comparison with 3 (1.388(5) Å) and [Yb{N4(Me)2Et8}(thf)] (1.127 Å).4g The metallocene bend angle 147.78° (of exo- Yb(2)/Yb(2)#) between the two macrocycles of dimeric 4 is smaller than that (152.56°) within the macrocycle cavity of monomeric 3. This bonding mode, together with the bridging of two μ3-O centers, brings two eightcoordinate exo- ytterbium(III) centers close (Yb(2)···Yb(2)# = 3.2858(10) Å). The close contact distance is comparable with

The phenomenon of rearrangement of the macrocycle has been encountered previously in calix[4]pyrrolide and relevant transcalix[2]benzene[2]pyrrolide complexes of other rare-earth metals such as Sm1h,14 and Tm.1j The structure features one pair of alternate pyrrolide rings (of N2/N4 or N2#/N4#) σ bonded to a lanthanum center with La−N bond lengths of 2.501(3) and 2.506(3) Å. These distances are expectedly longer than those of smaller metals in N-confused [Sm2(N3N′Et8)2Li2(thf)4] (2.458(6) and 2.455(6) Å)1i and [Tm2(N3N′Et8)2K2(dme)4] (2.385(3) 3860

dx.doi.org/10.1021/om2011134 | Organometallics 2012, 31, 3857−3864

Organometallics

Article

and 2.380(3) Å).1j Both a neutral pyrrole ring (of N3 or N3#) and the N-confused pyrrolide ring (of N1 or N1#) sandwich the nine-coordinate lanthanum center with a metallocene angle of 167.86°. The acidic proton on N(3) of the pyrrole ring was located by difference Fourier synthesis in the crystal structure refinement (Fig. 6). Consistent with this, the Ln−centroid distance of the neutral pyrrole ring (2.685 Å) is about 0.1 Å longer than that of the negatively charged N-confused pyrrolide ring (2.587 Å). The nitrogen atom from a N-confused pyrrolide unit bridges to the adjacent lanthanum metal center through a σ bond (2.528(3) Å). To the best of our knowledge, compound 5 is the first example of partial deprotonation of a calix[4]pyrrole by a rareearth element. The triple deprotonation of calix[4]pyrrole resembles that of the calix[4]arene in 1 and 2. It is not yet fully understood why the N-confused pyrrolide occurs, but it was suggested that transient low-valent rare-earth-metal derivatives play key roles in these macrocyclic rearrangements.1j,14 The RTP reaction of lanthanum with diphenylmercury and calix[4]pyrrole presumably involves transient low-valent lanthanum species on the way to the LaIII product. To further examine the possibility of the triple deprotonation of calix[4]pyrrole without rearrangement of the pyrrolide, further reactions have been carried out in the absence of rare-earth-metal elements. Calix[4]pyrrole reacts with 3 equiv of potassium to give the colorless triply deprotonated product 6 in good yield (eq 4). Compound 6 is soluble in thf but sparsely soluble in hydrocarbon solvents such as toluene and hexane. The characterization by IR and 1H NMR spectroscopy is consistent with triple deprotonation of the ligand with largely diminished N−H absorption (see Figure S1 in the Supporting Information for comparison of IR spectra with H4N4Et8 and 3) and proton resonances. The 1H NMR spectrum at 323 K includes three broad singlet resonances of CH (of pyrrole rings) and CH3 and CH2 (of ethyl groups on meso carbons). At 228 K, the broad singlet resonances, appearing previously at 323 K, are split into multiple resonances, suggesting that the fluxional movement is limited. The NH proton resonance migrates significantly from 6.60 (323 K) to 7.08 ppm (228 K), indicating possible delocalization of the proton on nitrogen atoms at higher temperature, but with more localization occurring at lower temperature as the solid-state structure (see structural discussion below) is approached. The constitution was further supported by microanalysis. The potassium salt 6 is the first case of limited deprotonation of octaalkylcalix[4]pyrroles H4N4R8 by a group 1 metal, differing from reported complete deprotonation.1a,j,15 The limited metalation changes the charge of the ligand from 4− for (N4Et8)4− to 3− for (HN4Et8)3−. However, the reaction of the tripotassium potassium derivative with ytterbium triiodide did not involve transfer of the trivalent ligand.

Figure 7. (a) Molecular structure of 6 shown with 50% thermal ellipsoids. Hydrogen atoms connected to carbon atoms and disorders are omitted for clarity, and the bond between the metal and the centroid is shown as a dashed line. Selected distances (Å) and angles (deg): K(1)−centroid(ring of N(1)) = 2.861, K(1)−centroid(ring of N(3)) = 3.061, K(2)−centroid(ring of N(2)) = 2.851, K(3)− centroid(ring of N(1)) = 2.738, K(3)−centroid(ring of toluene) = 2.993, K(1)−N(2) = 2.815(1), K(2)−N(1) = 2.703(3), K(2)−N(3) = 3.265(3); centroid(ring of N(2))−K(2)−centroid(ring of N(2)#) = 143.05, N(2)−K(1)−N(2)# = 108.90(7), N(1)−K(2)−N(3) = 112.04(7). The K−C(arene) bond lengths are given in the text. Symmetry code: for N(2)#, X, 1/2 − y, z; for K(1)# and C53#/C54#, x − 1, y, z. (b) ChemDraw structural moiety showing bonding modes (η5:η1:η5:η1 and η5) between the macrocycle and endo-bound K(1)/ K(2) and exo-bound K(3) in 6.

previously for ytterbium centers in 3 and the endo-bound potassium atom in [{K2(N4(Me2)Et8)(thf)2}n].16 The exobonded K3 atom is η5 bonded by a single pyrrolide and also has a thf molecule ligated. To complete the coordination sphere, there are close contacts between potassium centers and solvate toluene carbons, where distances shorter than 3.55 Å are considered to be bonding.17−19 One toluene bridges K1# and K2 in a μ-η3:η2 manner, while the other is η6 bound to K3 (Figure 7). The K−C bond lengths between toluene arene carbons and formally 10-coordinate K1 are K1−C53 = 3.39(1), K1−C54 = 3.27(1), and K1−C55 = 3.41(1) Å; with 9coordinate K2, they are K2−C53# = 3.45(1) and K2−C54# = 3.38(1) Å, and with 7-coordinate K3, K3−C(24−29) = 3.22(1)− 3.38(1) Å. These bond lengths are comparable with those in related 9-coordinate [K(η6-PhMe){Ln(tBu2pz)4}] (tBu2pz = 3,5di-tert-butylpyrazolato; Ln = La, six K−C bonds at 3.21(1)− 3.36(1) Å; Ln = Lu, 3.27(1)−-3.33(1) Å);17 7-coordinate [K{N(SiMe2R)2}(η6-PhMe)]2 (R = furyl, 2-methylfuryl; 3.31− 3.41 Å),18 and 8-coordinate [KN(SiMe2Ph)2(η6-PhMe)]2 (3.262(2)−3.532(2) Å).19 Supposedly due to the more unsaturated coordination situation in comparison with endobonded potassium atoms, there are close contacts between the

6K + 2H4N4Et8 + 2thf + 4PhMe → (2/n)[{K3(HN4Et8)(thf)(PhMe)2 }n] + 3H 2 6

(4)

The molecular structure of 6 in the solid state adopts a polymeric form, with incorporation of both endo- and exobound potassium atoms in the macrocyclic cavity (Figure 7). The remaining acidic proton of [HN4Et8]3− was located on N3 from difference Fourier synthesis in the crystal structure refinement. Both endo-bound K1 and K2 atoms are alternately η5:η1:η5:η1 bonded by the macrocycle in the cavity, as seen 3861

dx.doi.org/10.1021/om2011134 | Organometallics 2012, 31, 3857−3864

Organometallics

Article

the drybox and introduced continuously at a flow rate of 5 mL min−1. Melting points were determined using a SELBYS electrothermal melting point apparatus in sealed glass capillaries under nitrogen and are uncalibrated. Microanalyses were determined by the Campbell Microanalytical Service, University of Otago, New Zealand, whereas metal analyses were determined by Na2H2edta titration.21 Solvents were dried and distilled over sodium metal or sodium benzophenone ketyl before use. Lanthanoid metals were purchased from Santoku (America Int.) or Tianjiao (Baotou, China) as ingots or rods and stored under nitrogen in a glovebox. Hg(C6H5)2 and K metal were used as received from Aldrich. Hg(C6F5)2,22 p-Bu-t-calix[4]arene,23 H4N4Et8,24 and YbI3(thf)3.525 were prepared according to literature procedures. Synthesis of [Yb(calix[4]H)(thf)]2 (1). In a Schlenk flask containing ytterbium metal filings (0.50 g, 2.9 mmol), bis(pentafluorophenyl)mercury (0.50 g, 0.93 mmol), p-Bu-t-calix[4]arene (0.41 g, 0.63 mmol), and Hg metal (2 drops) was added thf (30 mL). Ultrasonication for 48 h gave a yellow solution that was filtered and concentrated under vacuum to ca. 7 mL. Small yellow crystals grew over 3 days; however, these were unsuitable for X-ray crystallography (0.42 g, 75%). Dec pt: 210 °C. Anal. Calcd for C96H122O10Yb2 (1782.07): Yb, 19.42. Found: Yb, 19.05. HRMS (positive mode): found 1661.6600, C88H106O8Yb2 + Na requires 1661.6563. IR (Nujol mull, cm−1): 3200 w, 1601 m, 1495 s, 1294 m, 1259 m, 1200 m, 1125 m, 1070 m, 1023 m, 892 m, 868 m, 819 m, 795 m, 665 w, 552 w. Synthesis of [{Nd(calix[4]H)(thf)}2] (2). In a Schlenk flask containing neodymium metal filings (0.40 g, 2.8 mmol), bis(pentafluorophenyl)mercury (0.42 g, 0.79 mmol), p-Bu-t-calix[4]arene (0.35 g, 0.54 mmol), and Hg metal was added thf (30 mL). Ultrasonication for 48 h gave a blue solution that was filtered and concentrated under vacuum to ca. 5 mL. Small, pale blue block crystals of 2·2thf grew upon standing for 3 days (0.31 g, 61%). Dec pt: 240 °C. Anal. Calcd for C96H122O10Nd2 (loss of two lattice thf molecules, 1724.47): Nd, 16.73. Found: Nd, 16.70. IR (Nujol, cm−1): 3200 w, 1605 m, 1495 s, 1296 m, 1260 m, 1201 m, 1122 m, 1080 m, 1030 m, 892 m, 868 m, 816 m, 792 m, 665 w, 552 w. 1H NMR (300.13 MHz, C6D6, 303 K): 0.29 (br s, 72H, But), 2.26 (br s, 8H, THF), 2.49 (br s, 8H, THF), 2.97 (s, 16H, CH2), 9.26 (br s, 16H, ArH), 12.08 (br s, 2H, OH), indicating loss of lattice thf. Synthesis of [Yb2(N4Et8)(thf)4] (3). Yb metal powder (1.0 g, 6.0 mmol), Hg(C6F5)2 (2.1 g, 4.0 mmol), and H4N4Et8 (1.1 g, 2.0 mmol) in thf (40 mL) were stirred at ambient temperature for 48 h. The solution was filtered and concentrated to ca. 10 mL in vacuo. The mixture was warmed until the solution was clear. The solution was stored at ambient temperature for 2 days and yielded the target compound as orange rhombus crystals (1.7 g, 73%). Anal. Calcd for C44H64N4O2Yb2 (loss of two thf molecules, 1027.11): C, 51.45; H, 6.28; N, 5.45; Yb, 33.70. Found: Yb, 33.50. Calcd for C36H48N4Yb2 (loss of four thf molecules, 882.90): C, 48.97; H, 5.48; N, 6.35. Calcd for C72H96N8O2Yb4 (4−2thf, 1797.80): C, 48.10; H, 5.38; N, 6.23. Found: C, 47.69; H, 5.30; N, 5.95; IR (Nujol, cm−1): 3091 m, 3077 m, 1594 w, 1485 w, 1356 m, 1324 w, 1271 s, 1246 m, 1159 m, 1134 w, 1037 s, 1020 m, 975 w, 924 m, 888 s, 829 m, 790 w, 757 m. 1 H NMR (300.13 MHz, C7D8, 303 K): 0.86 (t, 3J = 7.50 Hz, 24H, CH3), 1.36 (br s, 8H, CH2, thf), 1.96 (m, 8H, CH2), 2.16 (m, 8H, CH2), 3.53 (br s, 8H, CH2, thf), 6.11 (s, 8H, CH, pyr), also indicating loss of two thf molecules. 13C NMR (75.5 MHz, C7D8, 303 K): 10.2 (CH3), 26.5 (CH2, thf), 30.9 (CH2), 48.1 (C), 70.9 (CH2, thf), 103.5 (CH, pyr), 154.3 (CR, pyr). UV/vis: λmax (log ε) 402 nm (3.08). Attempted Reaction of 3 with H4N4Et8. H4N4Et8 (0.030 g) was added to a solution of 3 (0.030 g) in C7D8 (0.7 mL) in a J. Young valve equipped NMR tube. The mixture was hand shaken until the solution was clear. 1H NMR spectroscopy showed only two starting compounds and no new species formed. Synthesis of [Yb4(μ3-O)2(N4Et8)2(thf)2] (4). In a solution of 3 (0.51 g, 0.44 mmol) in toluene (10 mL) was slowly diffused dry air. The light yellow solid 4·2PhMe precipitated over 3 days (0.21 g, 45%). Anal. Calcd for C80H112N8O4Yb4 (loss of two toluene molecules, 1941.96): Yb, 35.64. Found: 35.95. HRMS (positive mode): found

exo metal center (K3) and ethyl groups on a meso carbon (K3···C7 = 3.218(3) and K3···C6 = 3.384(3) Å). With these agostic interactions included, the overall coordination number of K3 is 9. Related to the triply deprotonated characteristics of calix[4]pyrrole [HN4Et8]3−, the η1 bond K2−N3 length involving the neutral pyrrole ring (3.265(3) Å) is longer than that of negative charged pyrrolide rings (K1−N2 = 2.815(1), K2−N1 = 2.703(2) Å). K1 is η5 bonded to the neutral pyrrole ring with a K−centroid length of 3.061 Å, which is also longer than those of deprotonated pyrrolide (e.g., K1−centroid(ring of N1) = 2.862 Å). The K−N bond lengths of the deprotonated pyrrolide are comparable with those relevant in [{K2(N4(Me2)Et8)(thf)2}n] (2.820(2) and 2.815(2) Å).15 However, these bond lengths are shorter than the mean K−N length of [{K4(N4Bun8)(dme)3}n] (2.906 Å), presumably related to the difference between triple and quadruple deprotonations of the macrocycle.15d

■

CONCLUSIONS RTP reactions directly from rare-earth-metal elements have been demonstrated to be a practical synthetic route to access rare alkali-metal-free rare-earth-metal species of non-modified calix[4]arene and calix[4]pyrrole systems. Calix[4]H4 can be triply deprotonated readily by RTP reactions with rare-earth elements. For calix[4]pyrrole H4N4Et8, which incorporates four acidic protons, RTP reactions also generated the triply deprotonated product 5 with N-confusion of one pyrrolide of the macrocycle. For ytterbium with a relatively stable divalent state, the RTP reaction of H4N4Et8 generated the completely deprotonated ytterbium(II) complex 3, which is readily oxidized by dry dioxygen, forming an ytterbium(III) oxo complex. The novel structure of the oxide complex 4 displays a partial cone conformation of the macrocycle, accommodating only one metal center in the cavity and the first example of two such macrocyclic units sandwiching rare-earth-metal centers outside the macrocycle cavity. The stoichiometrically controlled reaction with potassium metal provides the triply deprotonated potassium complex 6. However, the metathesis reaction with ytterbium triiodide does not give access to the corresponding partially deprotonated calix[4]pyrrolide−ytterbium complex. The degree of deprotonation of the ligands in all cases corresponded to that expected from the stoichiometry of the reagents, which was dictated by the composition of the intended target molecules. However, it was not possible to protonate [Yb2(N4Et8)(thf)4] (3) with the H4N4Et8 ligand.

■

EXPERIMENTAL SECTION

General Considerations. All compounds were prepared and handled using conventional inert-atmosphere techniques. IR spectra were recorded as Nujol mulls between NaCl plates using either a Perkin-Elmer 1600 Series FTIR instrument or a Perkin-Elmer Spectrum RX I FTIR spectrometer within the range 4000−600 cm−1. Multinuclear NMR spectra were recorded with a Bruker DPX 300 spectrometer. Chemical shifts (in ppm) were referenced to the residual resonances of the deuterated solvents (1H and 13C). UV−vis spectra were collected on a Cary 5G UV−vis spectrophotometer in a 1 mm quartz cell suitable for the handling of air- and moisturesensitive materials. Electrospray ionization mass spectrometry (ESIMS) experiments (HRMS) were obtained on a hybrid tandem quadrupole/time-of-flight (Q-TOF) instrument, equipped with a pneumatically assisted electrospray (Z-spray) ion source (Micromass, Manchester, U.K.) operated in the positive mode.20 The electrospray potential was set to 3 kV, and the extraction cone voltage was usually varied between 30 and 50 V; the samples were dissolved in dry thf in 3862

dx.doi.org/10.1021/om2011134 | Organometallics 2012, 31, 3857−3864

Organometallics

Article

Table 1. Crystal Data and Structure Refinement Details for Complexes 2−6

formula Mr space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z μ (mm−1) ρcalcd (g cm−3) Nτ N (Rint) R1/wR2 (I > 2σ(I)) R1/wR2 (all data) GOF max/min Δe (eÅ−3])

[{Nd(calix[4]H) (thf)}2]·2thf (2·2thf)

[Yb2(N4Et8)2(thf)4] (3)

[Yb4(μ3-O)2(N4Et8)2 (thf)2]·2PhMe (4·2PhMe)

[La2(HN3N′Et8)2]·4thf (5·4thf)

[{K3(HN4Et8)(thf) (PhMe)2}n] (6)

C104H138O12Nd2 1868.62 P21/c 18.4364(5) 10.8024(3) 23.5115(6)) 90 95.3860(10) 90 4661.8(2) 2 1.161 1.331 71 960 10 678 (0.0917) 0.0515/0.1006 0.0883/0.1142 1.044 1.195/−1.056

C52H80N4O4Yb2 1171.28 I41/a 14.669(5) 14.669(5) 30.439(9) 90 90 90 6550(3) 4 2.874 1.188 34 769 2498 (0.0699) 0.0428/0.1114 0.0488/0.1158 1.080 0.825/−1.252

C94H128N8O4Yb4 2126.20 P1̅ 13.983(3) 14.142(3) 14.351(3) 116.30(3) 91.35(3) 119.31(3) 2110.9(8) 1 4.446 1.673 26 728 7488 (0.0769) 0.0342/0.0725 0.0362/0.0735 1.121 1.368/−1.737

C88H130N8O4La2 1641.82 P21/n 15.6071(3) 14.4245(3) 19.1631(4) 90 109.0350(10) 90 4078.19(14) 2 1.088 1.337 34 956 9300 (0.0501) 0.0400/0.0934 0.0519/0.0934 1.027 0.961/−0.726

C54H73N4OK3 911.46 P21/m 10.0771(5) 16.5047(9) 15.2788(8) 90 96.2560(10) 90 2526.0(2) 2 0.311 1.198 16 650 4598 (0.0489) 0.0452/0.1124 0.0560/0.1203 1.048 0.626/−0.373

1801.5293, C72H97N8O2Yb4 requires 1801.5289. IR (Nujol, cm−1): 1323 w, 1286 w, 1205 w, 1153 m, 1131 w, 1051 m, 1017 m, 974 w, 925 m, 869 w, 840 w, 802 w, 756 m, 694 w. Synthesis of [La2(HN3N′Et8)2] (5). La metal powder (0.41 g, 3.0 mmol), Hg(C6H5)2 (1.1 g, 3.0 mmol), and H4N4Et8 (1.1 g, 2.0 mmol) in thf (40 mL) were stirred at 50 °C for 72 h. The solution was cooled to ambient temperature, filtered, and concentrated to ca. 10 mL in vacuo. The solution was stored at ambient temperature for 1 week and yielded colorless crystals. Further crystallization led to crystals of the unreacted H4N4Et8. An X-ray single-crystal structure determination was conducted for 5, but the small number of crystals obtained prevented other characterization. Synthesis of [{K3(HN4Et8)(thf)(PhMe)2}n] (6). Potassium metal (0.47 g, 12.0 mmol) was added to a solution of H4N4Et8 (2.2 g, 4.0 mmol) in thf (60 mL), and the mixture was refluxed for 3 h. The solution was filtered and concentrated to ca. 10 mL in vacuo. After addition of toluene (20 mL), the mixture was warmed until the solution was clear. The solution was stored at ambient temperature for 3 days and yielded the target compound as colorless crystals (2.2 g, 61%). IR (Nujol, cm−1): 3461 m, 3081 m, 3066 m, 1589 w, 1572 w, 1542 w, 1493 m, 1403 m, 1317 m, 1266 s, 1187 m, 1154 w, 1086 w, 1042 s, 1023 s, 970 m, 923 m, 886 s, 834 m, 769 m, 749 m. 1H NMR (300.13 MHz, C4D8O, 323 K): 0.36 (br s, 24H, CH3), 1.54 (s, 4H, CH2, thf), 1.66 (br s, 16H, CH2), 2.11 (s, 6H, CH3), 3.39 (s, 4H, CH2, thf), 5.45 (br s, 8H, CH, pyr), 6.60 (s, 1H, NH, pyr), 6.86−6.92 (m, 10H, CH, tol). 1 H NMR (300.13 MHz, C4D8O, 228 K): 0.15 (m, 12H, CH3), 0.37 (m, 12H, CH3), 1.50−1.76 (m, 20H, CH2, Et + thf), 2.11 (s, 6H, CH3), 3.42 (s, 4H, CH2, thf), 5.31−5.38 (m, 8H, CH, pyr), 6.89−7.03 (m, 10H, CH, tol), 7.08 (s, 1H, NH, pyr). Anal. Calcd for C54H73N4OK3 (911.50): C, 71.16; H, 8.07; N, 6.15. Found: C, 70.22; H, 8.25; N, 6.15. Attempted Reaction of 6 with Ytterbium Triiodide. thf (10 mL) was added to a Schlenk flask charged with 6 (0.45 g, 0.5 mmol) and ytterbium triiodide (0.43 g, 0.5 mmol). The mixture was stirred at 70 °C overnight. The insoluble mixture was not separable. X-ray Crystal Structure Determinations. Crystals were mounted in thin-walled glass capillaries or cryoloops. Intensity data were collected on a Bruker X8 APEX II CCD diffractometer (2·2thf, 5·4thf, and 6) using Mo Kα radiation at 123 K (λ = 0.710 73 Å) or the Australian Synchrotron MX1 beamline (3 and 4·2PhMe) at 100 K (λ = 0.712 Å). With the Bruker SMART system, data sets were empirically corrected for absorption with SADABS.26 With the MX1 beamline, data were collected using the BlueIce27 GUI and processed with the XDS28 software package. The structures were solved by

conventional methods and refined by full-matrix least squares on all F2 data using SHELX97,29 in conjunction with the X-Seed GUI.30 Anisotropic thermal parameters were refined for non-hydrogen atoms (unless otherwise noted), and hydrogen atoms on carbons were calculated and refined with a riding model. Hydrogens on nitrogen/ oxygen atoms were located by difference Fourier synthesis. Crystal data and data collection and refinement details are given in Table 1.

■

ASSOCIATED CONTENT

S Supporting Information *

A figure giving IR spectra of the N−H stretching region for H4N4Et8, {K3(HN4Et8)(thf)(PhMe)2}n], and [Yb2(N4Et8)(thf)4] and CIF files giving crystal data for 2−6. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*Fax: (+61)399054597. E-mail: [email protected] (P.C.J.); [email protected] (G.B.D.). Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank Dr. Florian Jaroschik and Dominique Harakat for running HR MS for compounds 1 and 4. We thank the Australian Research Council and the Education Bureau of Hubei Province, People's Republic of China, for support. Aspects of this research were undertaken on the MX1 beamline at the Australian Synchrotron, Victoria, Australia.

■ ■

DEDICATION Dedicated to the memory of Professor F. Gordon A. Stone, F.R.S., a pioneer of organometallic chemistry. REFERENCES

(1) (a) Jubb, J.; Gambarotta, S.; Duchateau, R.; Teuben, J. H. J. Chem. Soc., Chem. Commun. 1994, 2641. (b) Jubb, J.; Gambarotta, S. J. Am. Chem. Soc. 1994, 116, 4477. (c) Song, J. I.; Gambarotta, S. Angew. Chem., Int. Ed. Engl. 1995, 34, 2141. (d) Campazzi, E.; Solari, E.;

3863

dx.doi.org/10.1021/om2011134 | Organometallics 2012, 31, 3857−3864

Organometallics

Article

Floriani, C.; Scopelliti, R. Chem. Commun. 1998, 2603. (e) Campazzi, E.; Solari, E.; Scopelliti, R.; Floriani, C. Chem. Commun. 1999, 1617. (f) Dubé, T.; Gambarotta, S.; Yap, G. P. A. Organometallics 2000, 19, 121. (g) Dube, T.; Gambarotta, S.; Yap, G. P. A. Organometallics 2000, 19, 817. (h) Guan, J.-W.; Dubé, T.; Gambarotta, S.; Yap, G. P. A. Organometallics 2000, 19, 4820. (i) Dubé, T.; Guan, J.; Gambarotta, S.; Yap, G. P. A. Chem. Eur. J. 2001, 7, 374. (j) Korobkov, I.; Aharonian, G.; Gambarotta, S.; Yap, G. P. A. Organometallics 2002, 21, 4899. (k) Zhou, S.-L.; Wu, S.-H; Zhu, H.; Wang, S.-W.; Zhu, X.-C.; Zhang, L.-J.; Yang, G.-S.; Cuia, D.-H.; Wang, H.-Y. Dalton Trans. 2011, 40, 9447. (2) See reviews: (a) Schumann, H.; Meese-Marktscheffel, J. A.; Esser, L. Chem. Rev. 1995, 95, 865. (b) Evans, W. J.; Davis, B. L. Chem. Rev. 2002, 102, 2119. (3) Jang, Y.-S.; Kim, H.-J.; Lee, P.-H; Lee, C.-H. Tetrahedron Lett. 2000, 41, 2919. (4) (a) Wang, J.; Dick, A. K. J.; Gardiner, M. G.; Yates, B. F.; Peacock, E. J.; Skelton, B. W.; White, A. H. Eur. J. Inorg. Chem. 2004, 10, 1992. (b) Wang, J.; Gardiner, M. G. Chem. Commun. 2005, 12, 1589. (c) Wang, J.; Gardiner, M. G.; Skelton, B. W.; White, A. H. Organometallics 2005, 24, 815. (d) Wang, J.; Amos, R. I. J.; Frey, A. S. P.; Gardiner, M. G.; Cole, M. L.; Junk, P. C. Organometallics 2005, 24, 2259. (e) Davies, N. W.; Frey, A. S. P.; Gardiner, M. G; Wang, J. Chem. Commun. 2006, 46, 4853. (f) Frey, A. S. P.; Gardiner, M. G.; Stringer, D. N.; Yates, B. F. Organometallics 2007, 26, 1299. (g) Dick, A. K. J.; Frey, A. S. P.; Gardiner, M. G.; Hilder, M.; James, A. N.; Junk, P. C.; Powanosorn, S.; Skelton, B. W.; Wang, J.; White, A. H. J. Organomet. Chem. 2010, 695, 2761. (h) Gardiner, M. G.; James, A. N.; Jones, C.; Schulten, C. Dalton Trans. 2010, 39, 6864. (5) Asfari, Z.; Böhmer, V.; Harrowfield, J.; Vicens, J. Calixarenes 2001; Kluwer Academic: Dordrecht, The Netherlands, 2001. (6) See examples: (a) Fedushkin, I. L.; Weydert, M.; Fagin, A. A.; Nefedov, S. E.; Eremenko, I. L.; Bochkarev, M. N.; Schumann, H. Z. Naturforsch., B 1999, 54, 466. (b) Estler, F.; Herdtweck, E.; Anwander, R. Dalton Trans. 2002, 3088. (c) Guillemot, G.; Castellano, B.; Prange, T.; Solari, E.; Floriani, C. Inorg. Chem. 2007, 46, 5152. (7) See examples: (a) Orr, G. W.; Barbour, L. J.; Atwood, J. L. Science 1999, 285, 1049. (b) Dalgarno, S. J.; Raston, C. L. Dalton Trans. 2003, 287. (c) Atwood, J. L.; Barbour, L. J.; Dalgarno, S. J.; Hardie, M. J.; Raston, C. L.; Webb, H. R. J. Am. Chem. Soc. 2004, 126, 13170. (d) Makha, M.; Alias, Y.; Raston, C. L.; Sobolev, A. N. New J. Chem. 2008, 32, 83. (e) Liao, W.-P.; Bi, Y.-F.; Gao, S; Li, D.-Q.; Zhang, H.-J.; Dronskowski, R. Eur. J. Inorg. Chem. 2008, 2959. (8) Furphy, B. M.; Harrowfield, J. M.; Ogden, M. I.; Skelton, B. W.; White, A. H.; Wilner, F. R. J. Chem. Soc., Dalton Trans. 1989, 2217. (9) Deacon, G. B.; Forsyth, C. M.; Nickel, S. J. Organomet. Chem. 2002, 647, 50. (10) Shannon, R. D. Acta Crystallogr., Sect. A 1976, 32, 751. (11) (a) Fedushkin, I. L.; Petrovskaya, T. V.; Girgsdies, F.; Kohn, R. D.; Bochkarev, M. N.; Schumann, H. Angew. Chem., Int. Ed. Engl. 1999, 38, 2262. (b) Lueken, H.; Schmitz, J.; Lamberts, W.; Hannibal, P.; Handrick, K. Inorg. Chim. Acta 1989, 156, 119. (c) Massarweh, G.; Fischer, R. D. J. Organomet. Chem. 1993, 444, 67. (d) Watson, P. L.; Tulip, T. H.; Williams, I. Organometallics 1990, 9, 1999. (e) Freckmann, D. M. M.; Dube, T.; Berube, C. D.; Gambarotta, S.; Yap, G. P. A. Organometallics 2002, 21, 1240. (f) Melman, J. H.; Fitzgerald, M.; Freedman, D.; Emge, T. J.; Brennan, J. G. J. Am. Chem. Soc. 1999, 121, 10247. (g) Karl, M.; Neumuller, B.; Seybert, G.; Massa, W.; Dehnicke, K. Z. Anorg. Allg. Chem. 1997, 623, 1203. (h) Deacon, G. B.; Harris, S. C.; Meyer, G.; Stellfeldt, D.; Wilkinson, D. L.; Zelesny, G. J. Organomet. Chem. 1998, 552, 165. (i) Xie, Z.-W.; Chui, K.-W.; Yang, Q.-C.; Mak, T. C. W.; Sun, J. Organometallics 1998, 17, 3937. (j) Fitzgerald, M.; Emge, T. J.; Brennan, J. G. Inorg. Chem. 2002, 41, 3528. (k) Evans, W. J.; Drummond, D. K.; Chamberlain, L. R.; Doedens, R. J.; Bott, S. G.; Zhang, H.; Atwood, J. L. J. Am. Chem. Soc. 1988, 110, 4983. (12) (a) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Clarendon: Oxford, U.K., 1984. (b) Cordero, B.; Gómez, V.; Platero-Prats, A. E.; Revés, M.; Echeverría, J.; Cremades, E.;

Barragán, F.; Alvarez, S. Dalton Trans. 2008, 21, 2832. (c) The most recent article about van der Waals radii does not include rareearth metals: Nag, S.; Banerjee, K.; Datta, D. New J. Chem. 2007, 31, 832. (13) Deacon, G. B.; Forsyth, C. M.; Junk, P. C.; Wang, J. Chem. Eur. J. 2009, 15, 3082. (14) Ilango, S.; Vidjayacoumar, B.; Gambarotta, S. Dalton Trans. 2010, 39, 6853. (15) (a) De Angelis, S.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J. Chem. Soc., Dalton Trans. 1994, 2467. (b) Jubb, J.; Berno, P.; Hao, S.; Gambarotta, S. Inorg. Chem. 1995, 34, 3563. (c) Guan, J.; Dubé, T.; Gambarotta, S.; Yap, G. P. A. Organometallics 2000, 19, 4820. (d) Bonomo, L.; Solari, E.; Scopelliti, R.; Floriani, C. Chem. Eur. J. 2001, 7, 1322. (16) Wang, J.; Gardiner, M. G.; Peacock, E. J.; Skelton, B. W.; White, A. H. Dalton Trans. 2003, 161. (17) Deacon, G. B.; Delbridge, E. E.; Evans, D. J.; Harika, R.; Junk, P. C.; Skelton, B. W.; White, A. H. Chem. Eur. J. 2004, 10, 1193. (18) Evans, L. T. J.; Cloke, F. G. N.; Coles, M. P.; Hitchcock, P. B. Inorg. Chim. Acta 2007, 360, 1258. (19) Evans, W. J.; Rego, D. B.; Ziller, J. W. Inorg. Chem. 2006, 45, 3437. (20) Daniels, D. P.; Deacon, G. B.; Harakat, D.; Jaroschik, F.; Junk, P. C. Dalton Trans. 2012, 41, 267. (21) (a) Cosgriff, J. E.; Deacon, G. B.; Gatehouse, B. M. Aust. J. Chem. 1993, 46, 1881. (b) Cosgriff, J. E.; Deacon, G. B.; Gatehouse, B. M.; Lee, P. R.; Schumann, H. Z. Anorg. Allg. Chem. 1996, 622, 1399. (22) Deacon, G. B.; Forsyth, C. M.; Wilkinson, D. L.; Lawrenz, E. T. In Synthetic Methods of Organometallic and Inorganic Chemistry; Herrman, W. A, Ed.; Thieme: New York, 1997; Vol. 6, pp 48−51. (23) Gutsche, C. D. Calixarenes: An Introduction, 2nd ed.; RSC Publishing: Tucson, AZ, 2008. (24) Rothemund, P.; Gage, C. L. J. Am. Chem. Soc. 1955, 77, 3340. (25) Izod, K.; Liddle, S. T.; Clegg, W. Inorg. Chem. 2004, 43, 214. (26) Sheldrick, G. M. SADABS: Program for Scaling and Absorption Correction of Area Detector Data; Universität Göttingen, Göttingen, Germany, 1997. (27) McPhillips, T. M.; McPhillips, S. E.; Chiu, H. J.; Cohen, A. E.; Deacon, A. M.; Ellis, P. J.; Garman, E.; Gonzalez, A.; Sauter, N. K.; Phizackerley, R. P.; Soltis, S. M.; Kuhn, P. J. J. Synchrotron Radiat. 2002, 9, 401. (28) Kabsch, W. J. Appl. Crystallogr. 1993, 26, 795. (29) Sheldrick, G. M. SHELXL-97 Program for Crystal Structure Refinement; Universität Göttingen, Göttingen, Germany, 1997. (30) Barbour, L. J. J. Supramol. Chem. 2001, 1, 1.

3864

dx.doi.org/10.1021/om2011134 | Organometallics 2012, 31, 3857−3864