4856
Chelate Chemistry. V. Metal Chelates Based on Tropolone and Its Derivatives E. L. Muetterties, H. Roesky, and C. M. Wright Contribution No. 1215 from the Central Research Department, Experimental Station, E. I. du Pont de Nemours and Company, Wilmington, Delaware 19898. Receiced June 4, 1966 Abstract : Rare earth tris chelates based on the 7-isopropyltropolone anion are associated and presumably contain seven- or eight-coordinatemetal ions. The degree of associationdrops significantly in going from the large lanthanide cations to the smaller ions such as lutetium(II1). Some of the smaller ions, such as erbium, tend to separate from aqueous solutions as monohydrated tris chelates. Monomolecular formulations were established for the solution state of (chel)2SnC12,(chel),SnCI, and (che1)aNbO with the 7-isopropyltropolone anion ligand. On the other hand, bis(isopropyltropolono)nickel(II) (paramagnetic) is not very soluble in nonbasic solvents and must be significantly associated. Chelate chemistry based on the monothio analog of tropolone is similar to that of the tropolone ion. Eight-coordinate lead and thorium(1V) chelates from thiotropone were readily obtained. Attempts to prepare tencoordinate pentakis chelates like the known Th(tropolonate)6- anion were unsuccessful with the thiotropone anion. Further distinctions between tropolone and thiotropone chemistry arise in nickel(I1) chelates where the thiotropone derivative is diamagnetic and square-planar. Tracer studies of basic hydrolyses of thiotropone cationic chelates identified ligand attack by hydroxyl ion as a significant, but not dominating, hydrolysis course.
T
he preceding in this series presented a fairly detailed characterization of tropolone ion (T) chelates encompassing synthesis, structure, and chemistry. Similarly, the nonmetal chemistry of N,Ndiniethylaminotroponeimine ion (A) has been elaborated;' transition metal chelates derived from this ligand have been extensively investigated.6 For this general class of chelate chemistry, the major areas for exploration that remain are (1) precise geometrical parameters for the various structural classes, six through ten coordinate, (2) information regarding the solution state, particularly the question of molecularity and coordination number, and (3) the character of chelates obtained from sulfur analogs. The first aspect, the structural one, is being explored by Professor J. L. Hoard and co-workers. It is t o the second two topics that this article is addressed. The solubility of neutral tropolone metal chelates is sufficiently low that reliable molecular weight determinations have been precluded for the most part. We have found that isopropyl substitution at the y position imparts much greater solubility to the tropolone chelates and have employed the y-isopropyltropolone (y-thujaplicin) ion (Figure 1) as a probe to establish molecularity for certain structural classes. Additionally, we have instituted a study of the chelate chemistry based on monothio derivatives of tropolone, 2-thiotropone, and of aniinotroponeiniine, aminothiotropone (Figure 1). y-Isopropyltropolone Chemistry. Molecularity of Tropolone Chelates. The extraordinary intractability of the neutral tristropolonates of the larger rare earth ions strongly implicated polymeric lattices through bridging oxygen atoms, i.e., three-coordinate chelate oxygen atoms and seven- or eight-coordinate metal atoms. Characterization of the analogous y-iso(1) E. L. Muetterties and C. M. Wright, J . Ani. Chem. Scc., 86, 5132 (1964). (2) E. L. Muetterties and C. M. Wright, ibid., 87, 21 (1965). (3) E. L. Muetterties and C. M. Wright, ibid., 87, 4706 (1965). (4) E. L. Muetterties, ibid., 88, 305 (1966). (5) E. L. Muetterties, J . Pure Appl. Chem., 10, 54 (1965). (6) D. R . Eaton, A . D. Josey, W. D. Phillips, and R. E. Benson, J . Chem. Phj.s., 39, 3513 (1963), and references therein.
Journal of the American Chemical Society
88:21
propyltropolone chelates clearly vindicates this view. Despite the presence of the solubilizing isopropyl groups, the tris chelates of the metal ions lanthanum through terbium(II1) are insoluble in all common solvents. The behavior of the smaller ions varies. Holmium and erbium(II1) tris chelates separate from an aqueous triethylamine solution as monohydrates and may represent seven- or eight- (polymeric) coordinate structures. Vacuum drying at 80" of the erbium chelate obtained from an aqueous anionic solution gives an anhydrous phase, which is intractable and isomorphous with the lanthanum (through terbium) chelate as judged by comparison of X-ray powder patterns. The infrared spectra of all the insoluble tris chelates are very similar. A soluble, anhydrous form of the erbium tris chelate was also isolated. It is identical with the anhydrous tris chelate of lutetium(II1) based on infrared and X-ray criteria. Molecular weight studies of the soluble erbium and lutetium chelates in nonpolar solvents indicate an association that approximates a trimer. The molecularity of the tris chelate based on a-isopropyltropolone and lutetium(II1) is trimeric in a variety of solvents. Like the anhydrous nickel(I1) acetylacetonate which is trimeric, the nickel(I1) derivative of y-isopropyltropolone must also be associated; it has only slight solubility in organic solvents such as chloroform. Nuclear magnetic resonance studies clearly show that this nickel compound is paramagnetic. The isopropyl proton resonances are shifted to high field and are broad; the aromatic protons were not detected, presumably because of line broadening from electron-spin relax a ti on. Tin halides react with tropolone t o give T2SnX2 and further replacement of halide can be effected only by tropolone ion going in discrete steps t o T3SnX and finally to T4Sn.'37 The chemistry of y-isopropyltropolone is analogous. Cessation of exchangt: at the (7) We have now found that the reaction of tetraphenyltin and tropolone at elevated temperatures is the simplest and cleanest route to TaSn. This method is similar to that used by I: Co, 19.6; C, 55.7; H, 3.32. Found: Co, 19.5; C, 55.8; H, 3.51. There were similarities in the X-ray powder patterns of the sublimed cobalt and nickel tropolonates, but there were no similarities between the pattern of these two and that of the copper tropolonate. Preparation of Pd(C7H50&. A solution of KZPdCI, (1.6 g, 0.005 mole) in 60 ml of water was added to a solution of tropolone (1.2 g, 0.01 mole) in 30 ml of ethanol to give an orange precipitate. The crude product was recrystallized from a mixture of acetonitrile, dichloromethane, and chloroform. The orange crystals were vacuum dried at 70" for 24 hr, mp 330-370" dec. Anal. Calcd for Pd(C,H60&: Pd, 30.6; C, 48.2; H, 2.87. Found: Pd, 30.7; C. 48.2; H, 2.82. Preparation of Zn(C,H50&. Zinc chloride (1.4 g, 0.01 mole), dissolved in a minimum of a 50:50 mixture of ethanol and water, was added to a solution of tropolone (3.7 g, 0.03 mole) in 100 ml of methanol to give a clear solution. The solution was evaporated and the solid residue was recrystallized from a hot ethanol-water mixture. Anal. Calcd for Zn(C7HsOz)2: Zn, 21.2; C, 54.7; H, 3.25. Found: Zn,21.7; C,55.2; H, 3.30. Preparation of Pb(C7HsOZ)2. Tropolone (1.2 g, 0.01 mole) and lead acetate trihydrate (7.6 g, 0.02 mole) were added to 30 ml of water and 40 ml of methanol. The mixture was heated to reflux and ethanol was added to give a clear solution. On cooling, orangeyellow crystals were obtained. These were recrystallized from a hot mixture of methanol and water, mp 23G232". Anal. Calcd for Pb(C7Hj02)2: Pb, 46.2; C, 37.5; H, 2.23; mol wt, 449.2. Found: Pb, 46.3; C, 37.5; H, 2.25; mol wt, 841 (vaporpressure osmometer in dichloromethane, extrapolated to infinite dilution).
Journal of the American Chemical Society
/
88:21
Preparation of Hg(C7HKh)z. The procedure described above for lead tropolonate was followed with mercuric acetate as the reagent. Anal. Calcd for Hg(C7H60&: Hg, 46.5; C, 38.0; H, 2.16. Found: Hg, 44.3; C , 37.9; H, 2.13. Hydrolysis of the mercuric tropolonate in deuterium oxide led to no introduction of deuterium into the aromatic C-H positions of the tropolone hydrolysate. Thus, there was no evidence for mercury-carbon bonding in this tropolone derivative. Preparation of Ni(C?HjOS)2. A slurry of thiotropone (1.05 g, 0.0076 mole) in 200 ml of methanol was added to a solution of nickel acetate tetrahydrate (0.95 g, 0.0038 mole) in 75 ml of water and 50 ml of methanol; a black solid immediately separated. The slurry was stirred for a period of 1 hr and then filtered. The solid was recrystallized twice from a mixture of acetonitrile and chloroform and then dried at 100" (0.01 mm). The deep violet crystals melted at 276-280" with decomposition. Anal. Calcd for N ~ ( C T H ~ O S )C, ~ : 50.5; H, 3.02; S, 19.2. Found: C, 50.5; H, 3.02; S, 19.3. The bis chelate sublimed with some degradation under vacuum above 200". Preparation of (C7HjOS)~B4PF6-. Boron tribromide (2.5 g, 0.01 mole) was slowly added from a hypodermic syringe through a serum cap to a flask containing thiotropone (2.7 g, 0.02 mole) in 200 ml of dichloromethane. Triethylamine (4 ml) was added, and the reaction mixture was taken to dryness by vacuum evaporation. The residue was dissolved in chloroform, carbon black was added, and the slurry was refluxed, filtered, and then diluted with benzene. On concentration the yellow filtrate yielded yellow crystals, which were collected and dissolved in a water-methanol mixture. To this solution was added a concentrated solution of ammonium hexafluorophosphate to give a yellow solid. The solid was recrystallized from acetonitrile and then recrystallized again from a mixture of acetonitrile and toluene. The crystalline material was dried at 80" (0.01 mm) for 1 hr, mp 163-165". Anal. Calcd for (CiHjOS)2B+PF6-: C, 39.1; H, 2.35; S, 14.9; F, 26.5. Found: C, 38.0, 39.6; H,2.81, 2.91; S, 14.5; F,26.2. Preparation of Salts of Ge(C7HaOS)3i. Thiotropone (4.14 g, 0.030 mole) was slurried in 150 ml of acetonitrile and germanium tetrachloride (2.1 g, 0.01 mole) was added to give a yellow precipitate. The slurry was warmed until mild reflux conditions were achieved, then 25 ml of chloroform was added. The slurry was then filtered while hot to give a yellow solid, mp 290" (dec). Anal. Calcd for (CiH50S)2GeCI2: C, 40.3; H. 2.40; S, 15.4; Ge, 17.4; CI, 17.0. Found: C,41.1; H,2.61; S, 15.6; Ge, 16.6; C1, 17.0. Triethylamine (4 ml) was added to a slurry of (C7HsOS)2GeCl? (4.0 g) and thiotropone (1.4 g) in 250 ml of acetonitrile. To the reaction slurry was added 35 ml of chloroform and then the slurry was warmed to reflux for 3 hr. After cooling to room temperature, 30 ml of dimethyl sulfoxide was added and the slurry was stirred for about 16 hr. The solution was filtered, and the solid was added to a refluxing mixture of 70 ml of methanol, 70 ml of ethanol, and 70 ml of water. The slurry was filtered while hot and to the filtrate was added ammonium hexafluorophosphate to give a yellow-brown solid. Anal. Calcd for (C;HjOS)3Ge-PF6-: C, 40.1; H, 2.39; S, 15.3; F, 18.1. Found: C,41.7; H, 2.86; S , 15.1; F, 18.2. Preparation of (C71-IjOS)3SnCl. Thiotropone (5.5 g. 0.04 mole) was added to a solution of tin tetrachloride (2.6 g, 0.01 mole) in 350 ml of acetonitrile. A yellow precipitate formed on addition of the thiotropone. The solid was collected by filtration, washed with acetonitrile, and vacuum dried (5.04 g yield). This product, (C7H50S)2SnC12, was identical with that obtained from tliiotropone and trichlorophenyltin. The crude tin complex was slurried in a mixture of 350 ml of acetonitrile and 50 ml of ethanol. Thiorropone (1.6 g) was added to the slurry followed by 3 ml oftriethylamine to yield a deep red-brown slurry. The slurry was stirred for 16 hr and then concentrated to about three-fourths volume. The solid was collected by filtration and vacuum dried, mp 195" (dec). Anal. Calcd for (C7H50S)3SnCI: C, 44.5; H, 2.66; S, 17.0; Sn, 20.9; CI, 6.28. Found: C, 43.0; H, 2.68; S, 17.4; Sn, 20.3; CI, 5.90. Preparation of Sn(CiH50S)2C12. A solution of trichlorophenyltin (3.02 g, 0,010 mole) in 50 ml of chloroform was added to a solution of thiotropone (4.14 g, 0.030 mole) in 60 ml of chloroform. A small amount of yellow precipitate sppeared. Approximately 160 ml of acetonitrile was added to the reaction slurry which was then warmed to reflux for 1 hr. During this time a considerable amount of solid separated from solution. Then 50 ml of dioxane was added and the solution was warmed to reflux and filtered while hot. The greenish solid was added to 2 1. of a solution containing approximately 60% acetonitrile, 30% methanol, 8 % ethanol, and 2% dimethyl sulfoxide. The slurry was heated to reflux and
/ November 5, 1966
4861 filtered while hot. The filtrate on concentration gave a yellow solid which was dried at 80" (0.01 mm), mp 375-377" dec. Anal. Calcd for Sn(C7H60S)2C12: C, 36.3; H, 2.16; S, 13.8; C1, 15.3. Found: C,36.5; H,2.31; S, 14.1; C1,14.8. Preparation of Pb(C7Hj0S)4. A slurry of lead tetraacetate (1.6 g, 0.0036 mole) in 200 ml of benzene was added to a solution of thiotropone (2.3 g, 0.016 mole) in 150 ml of benzene. An orange precipitate immediately appeared. The reaction slurry was warmed t o 60" for a period of 10 min, cooled, and then filtered. The orange solid was dried at 80" (0.01 mm), mp 202.5" dec. Anal. Calcd for Pb(C7HsOS)4: Pb, 27.4; C, 44.5; H, 2.65; S, 16.9. Found: Pb, 27.8; C,43.8; H , 2.88; S, 17.1. Attempted recrystallization of the tetrakis chelate from dimethyl sulfoxide led t o degradation t o the lead(1I) chelate. Dissolution of the tetrakis chelate in dimethyl sulfoxide at about 40" yielded a dark solution. This was filtered into toluene, and petroleum ether was added to give two phases. After several minutes an orange solid separated out at the interface. This was collected and dried at 80" (0.01 mm), mp 255-257". Anal. Calcd for Pb(C7HSOS)2: Pb, 43.0; C, 35.0; H, 2.18; S, 13.3. Found: Pb, 43.0; C, 35.2; H,2.26; S,14.0. Preparation of Th(C7HjOS)d. Thiotropone (2.6 g, 0.019 mole) was added to a solution of thorium nitrate tetrahydrate (2.76 g, 0.005 mole) in 40 ml of water and 80 ml of methanol. An orange precipitate separated and the slurry was stirred for a period of 1 hr. The solid was collected by filtration and vacuum dried. Attempts to sublime part of the crude product under vacuum were unsuccessful. Decomposition occurred at approximately 290" under vacuum. The remaining crude product was dissolved in warm dimethyl sulfoxide and filtered while hot. The filtrate was diluted with methanol and water to yield an orange solid which was dried at 80" (0.01 mmj; discoloration begins about 235", no evidence of melting below 400". Anal. Calcd for Th(C7H50S)4.0S(CH3)2: Th, 27.0; C, 42.0; H, 3.03; S, 18.7. Found: Th, 27.4; C, 42.6; H, 3.37; S,18.7. The dimethyl sulfoxide complex of Th(C7H50S)4(1.0 g, 0.0012 mole) was added to a solution of lithium hydroxide (0.1 g, 0.04 mole) and thiotropone (0.6 g, 0.004 mole) in 50 ml of water, 75 ml of methanol, and 50 ml of acetonitrile. The reaction slurry was heated to reflux for a period of 1.5 hr. The slurry was filtered while hot and a yellow insoluble material was vacuum dried at 80" (0.01 mm). Anal. Calcd for Th(C7HS0S)4: Th, 29.7; C, 43.1; H,2.58. Found: Th,29.8; C,43.0; H,2.52; Li,
