J. zyxwvutsrqp Am. Chem. zyxwvuts SOC. zyxwvu 1985, 107, 8087-8091 8087 Metallocalixarenes: Syntheses and X-ray Crystal Structures of Titanium( IV), Iron( HI), and Cobalt( 11) Complexes of p-tert-Butylcalix[ 4larene Marilyn M. Olmstead, Gary Sigel, HAkon Hope, Xiaojie Xu, and Philip P. Power* Contribution from the Department of Chemistry, University zyxwvu of California, Davis, California 9561 6. ReceiEed May 17, 1985 Abstract: The reactions of the metal amides [Ti(NMe,),], [Fe{N(SiMe3)2)3], and [(CO{N(S~M~,)~)~)~] with p-tert-butyl- calix[4]areneH4 (1) have resulted in the isolation and structural characterization of the first three a-bonded transition-metal derivatives of a calixarene. Complete exchange of the four -OH protons in 1 with [Ti(NMe,),] gives the complex [[Ti@- zy tert-butylcalix[4]arene)12].6PhMe (2) as orange-red crystals. The conformationally mobile cone configuration of 1 acquires rigidity in the titanium complex which exists in a dimeric form with bridging through one of the ligand oxygens resulting in a distorted tetrahedral coordination at titanium. The reactions of 1 with [Fe(N(SiMe3)2)3] or [(Co(N(SiMe,),],),] are more complex and involve -SiMe, shifts from silylamide groups to a ligand oxygen giving, for iron, an unusual complex of formula zyx [( Fe(NH,)@-tert-b~tylcalix[4]areneOSiMe~))~].3n-C~H~~ (3) and the new cluster [C0~(p-tert-butyIcalix[4]areneOSiMe~)~- (THF)].SPhMe (4) for cobalt. The remarkable inclusion of ammonia (which derives from an -N(SiMe,)2 group) in 3 appears to be unprecedented. The cluster 4 also appears to be unique since it is the only structurally characterized cobalt alkoxide. The crystal data at 140 K, Mo Ka (A = 0.71069 A), are as follows: 2-71 = 12.427 (5) A, b = 13.409 (5) A, c = 18.754 (13) A, zyxwvutsrqp CY = 98.60 (5)", p = 106.26 (4)O, y = 108.33 (3)O, zyxwvutsrqponm Z = 2, space group Pi, R = 0.067; 3-u = 12.815 (10) A, b = 15.061 (13) A, c = 16.870 (10) A, a = 111.67 (6)O, p = 91.66 (6)", y = 111.81 (7)", Z = 2, space group Pi, R = 0.083; 4-a = 10.152 (IO) A, b = 22.551 (11) A, c = 27.142 (11) A, p = 105.02 (3)", Z = 4, space group = P2,/n, R = 0.14. The calixarenes, illustrated by the example in Figure 1, are formed by condensation of p-tert-butylphenol with formaldehyde. They were first prepared by Zinkel and co-workers 40 years ago but they have their origins in the work of von Baeyer during the 1870's.* An important property of calixarenes is that they possess cavities and form molecular complexes with small molecule^.^ It is this characteristic and their ability to transport metal ions through hydrophobic membranes that has caused the current interest in their physical and chemical properties as models for the in vivo reactions of enzymes. It is also thought that the calixarenes may have similarities to the cyclodextrins which are cyclic oligosaccharides and are known to bind metal salts and organic substrates in their central ~avities.~ The work of Gutsche and co-workers has allowed the facile synthesis of a variety of calixarenes in good yield^,^ although the development of their syntheses has a long history.1*2,6 These simple synthetic routes have provided much of the impetus for current investigations. Recent work by Izatt and Christensen has shown that calixarenes are capable of selective ion transport and the formation of neutral complexes with cations thTough proton loss.' Our interest in these compounds stems from work involving transition-metal derivatives of bulky alkoxides such as OC-t-Bu,, which display interesting stoichiometries, coordination numbers, and previously unobserved reactions.*-I0 We therefore wished (1) Zinke, A,; Ziegler, E. Eer. 1944, 778, 264. (2) von Baeyer, A. Eer. 1872, 5, 25, 280, 1096. (3) Alfieri, C.; Dradi, E.; Pochini, A.; Ungaro, R.; Andreetti, G. D. J. Chem. SOC., Chem. Commun. 1983, 1075. Arduini, A,; Pochini, A,; Reverberi, S.; Ungaro, R. J. Chem. SOC., Chem. Commun. 1984, 981. McKervey, M. A,; Seward, E. M.; Ferguson, G.; Ruhl, B.; Harris, S. J. Ibid. 1985, 388. (4) Noltemeyer, M.; Saenger, W. J. Am. Chem. SOC. 1980, 102, 2710. (5) Gutsche, C. D. Acc. Chem. Res. 1983, 16, 161. Gutsche, C. D. Top. Curr. Chem. 1984, 123, 1. Gutsche, C. D.; Dhawan, B.; No, K. H.; Mu- thukrishran J. Am. Chem. SOC. 1981, 103, 3782. (6) Smith, B. H. 'Bridged Aromatic Compounds;" Academic Press: New York, 1964. Patrick, T. B.; Egan, P. A. J. Org. Chem. 1977, 42), 382. Cornforth, J. W.; Morgan, E. D.; Potts, K. T.; Rees, R. W. Tetrahedron 1973, 29, 1659. (7) Izatt, R. M.; Lamb, J. D.; Hawkins, R. T.; Brown, P. R.; Izatt, S. R.; Christensen, J. J. J. Am. Chem. SOC. 1983, 105, 1782. (8) Hvoslef, J.; Hope, H.; Murray, B. D.; Power, P. P. J. Chem. SOC., Chem. Commun. 1983, 1438. Murray, B. D.; Power, P. P. J. Am. Chem. SOC. 1984, 106, 701 I. Hope, H.; Murray, B. D.; Power, P. P. Ibid. 1985, 107, 169. (9) Lubben, T. V.; Wolczanski, P. T. J. Am. Chem. SOC. 1985, 107, 701. Chamberlain, L.; Rothwell, I. P.; Huffman, J. C. Inorg. Chem. 1984, 23, 2575. Lubben, T. V.; Wolczanski, P. T.; Van Duyne, G. D. Organometallics 1984, 23, 917. (10) Williams, I. D.; Pedersen, S. F.; Sharpless, K. B.; Lippard, S. J. J. Am. Chem. SOC. 1984, 106, 6430. to synthesize transition-metal derivatives of calixarenes to examine any unusual coordination and reactivity which these ligands might induce. For simplicity we have limited our initial work to the synthesis of neutral transition-metal derivatives of p-tert-butyl- calix[4]areneH4 (l), Figure 1. In this paper we describe the synthesis and characterization of the first transition-metal de- rivatives of p-tert-butylcalix[4] areneH,. Experimental Section General Procedures. All reactions were performed under N2. Solvents were distilled over Na/K metal and degassed at least twice before use. Anhydrous Ti[N(CH3)2]4 (Alfa) was used as purchased. p-tert-Butyl- calix[4]areneH4 (1),5 tris(bis(trimethylsilyl)amido}iron(III) (Fe[N- (SiMe,),],)," and bis(bis(trimethylsilyl)amido]cobalt(II) [(Co[N- (SiMe3)2]2)2]1z were prepared by literature procedures. IH NMR data were recorded on a Nicolet NT-200 Spectrometer operating at 200 MHz. IR data were recorded on a Perkin-Elmer 180 spectrometer. [ (Tilp - tert -butylcalix[4]arene}) ,)6PhMe (2). A solution of Ti [ N (C- H3)J4 (1.90 mmol, 0.43 g) in toluene (20 mL) was added to a slurry of ligand 1 (1.54 mmol, 1.00 g) in toluene (30 mL). After the solution was stirred for 1 h, 1 dissolved completely, giving a clear orange solution. Slow cooling gave the product as red-orange crystals; 0.69 g, 65%, mp > 360 "C. [{Fe(NH3)(p-tert-butylcalix[4]areneOSiMe3)}2]~3n -C6HI4 (3). This synthesis was similar to that described for 2. A solution of Fe[N- (SiMe3)2]3 (0.77 g, 1.43 mmol) in n-hexane (20 mL) was added slowly to a slurry of 1 (0.70 g 1.08 mmol) in toluene (30 mL). The ligand dissolved immediately, yielding a brownish-red solution. The reaction was stirred at 60 "C for 1 h and filtered. Reduction of volume and slow cooling afforded the product 3 as red-brown crystals; 0.18 g, 2l%, mp > 360 "C. [Co,@-tert-b~tylcalix[4]areneOSiMe~)~THF].5PhMe (4). In a similar manner, addition of a solution of Co[N(SiMe,),], (3.1 mmol, 1.16 g) in 50/50 toluene/hexane (40 mL) gave no initial reaction. The mixture was heated to reflux and concentrated to one-half its original volume. De- gassed T H F (20 mL) was added and the mixture allowed to cool slowly under refrigeration. Brownish-red crystals were obtained in low (ca. 5%) yields. X-ray Crystallographic Studies. All X-ray data were collected with a Syntex P2, diffractometer equipped with a locally modified Syntex LT-1 low-temperature device. Calculations were carried out on a Data General Eclipse Computer with use of the SHELXTL program system. Structures 2 and 3 were solved by direct methods whereas structure 4 was solved by the Patterson technique. In each case, an absorption correction was applied.') Scattering factors and corrections for anom- (1 1) Bradley, D. C.; Copperthwaite, R. C. Inorg. Synth. 1978, 18, 112. (12) Burger, H.; Wannagat, U. Monarsh. Chem. 1964, 95, 1099. 0002-7863/85/ l507-8087$0l.50/0 0 1985 American Chemical Society