2694 A. K. SINGH et al.

JEOL FX- 100 FT-NMR spectrometer at 99.55 and 25 MHz, respectively. IR spectra (of Nujol mulls between CsI windows or CsI/KBr discs) in the range 2OO-4000 cm- ’ were recorded on a Nicolet 5DX FT- IR spectrometer. Electronic spectra were recorded on a Hitachi UV-vis spectrophotometer model 350. Far IR spectra (up to 50 cm- ‘) in polyethylene were recorded on a Perkin Elmer far IR spectrometer model 1700X.

Synthesis of bis(2-hydroxy-5-methylphenyl)telluride

(1)

A suspension of bis(2-hydroxy-5-methylphenyl) tellurium(W) chloride (4.12 g, 10 mmol), prepared by the published method, in a 50% ethanol-water mixture (25-30 cm3) was treated with hydrazine hydrate (1.5 g, 3 mmol) dissolved in 10-15 cm3 ethanol. The resulting mixture was stirred for 10 min and poured into water. The pale yellow tel- luride was extracted with diethyl ether. The ether extract was washed with water, dried over Na,SO,

and concentrated to dryness. Yield, 65%. After re- crystallization from methanol the m.p. of the pale yellow telluride was 90°C. Found : C, 47.6 ; H, 4.1; Te, 38.1. Calc. for C14H1402Te: C, 47.1; H, 4.1; Te, 37.6%. NMR: ‘H, CDC13, 25°C: 6, 2.20(s, 6H, CH3), 6.85(bs, OH), 6.97-7.36(m, 6H, phenyl). ‘3C{‘H}, CDC13, 25°C: 6, 20.0(CH3), 102.1(C,), 114.o(CJ, 131.3(C,), 131.8(&), 139.9(C,), 154.0(&).

Synthesis of [HgC12 * lln and (PPh3)HgC12. 1

Mercury(I1) chloride (0.27 g, 1 mmol) was refluxed with 1 (0.34 g, 1 mmol) in methanol with stirring for 2-3 h. The yellow precipitate separated out was filtered, washed with methanol and dried in vacua. Yield 80%.

The suspension of HgClz* l(0.5 mmol) in 10 cm3 methanol was mixed with triphenylphosphine (1 mmol) dissolved in methanol (10 cm’). The reaction mixture was refluxed with stirring for 2-3 h. The suspended mercury-complex dissolved. The solu- tion was filtered and the filtrate concentrated to 5-

Table 1. Elemental analysis, m.p. and ‘H NMR data of complexes of 1 and 2

Complex

Analysis : Found (Calc.)(%) m.p. (“C) C H Te Cl Metal Chemical shift (6, ppm) at 25°C”

110

154

142

165

[PdCl(Za-H)], 151

pdC1(2b-H)]2 158

lB-W~-Wl, 142

[PtCl(2a-H)]* 178

[Pt’Wb-HL 160

[PtC1(2c+U 2 164

27.8 (27.4) 20.9

(20.0) 27.6

(28.5) 27.9

(29.1) 30.7

(30.5)

33.5 (34.5) 33.6

(34.8) 36.2

(36.3)

28.2 (28.8) 28.9

(29.4) 29.6

(30.8)

(E) 2.4

(2.7)

(Z)

21.4 (20.7) 16.0

(15.2) 23.4

(23.3) 23.5

(22.1) 22.0

(21.6)

-

11.4 30.8 (11.8) (32.6)

(is) (cc:) 6.5 37.7

(6.5) (36.7)

(Z) ,:tt 34.6

&) (34.0)

- -

- - -

Solubility inadquate for NMR

2.14(s, 6H, CH,), 6.93(bs, OH), 7.01-7.6O(m, 21H, ArH) 2.2(s, 3H, CH,), 6.8-7.8(m, 8H, ArH)

2.3(s, 3H, CH,), 3.7(s, 3H, 0CH3), 6.74.5(m, 7H, ArH) 1.30-l .45(t, 3H, CHB of OEt), 2.2(s, 3H, CH3), 3.8A.O(q, 2H, OCHJ, 6.6-7.8(m, 7H, ArH) 2.2(s, 3H, CHs), 6.8-8.1(m, 8H, ArH)

2.2(s, 3H, CH& 3.9(s, 3H, 0CH3), 6.9-7.2, S.O-S.Z(m, 7H, ArH) 1.3-l .5(t, 3H, CH, of OEt), 2.2(s, 3H, CH& 4.0-4.2(q, 2H, OCH& 6.9-7.9, 8.1-8.2(m, 7H, ArH) 2.3(s, 3H, CHJ, 6.8-8.1(m, 8H, ArH)

2.2(s, 3H, CH3), 3.8(s, 3H, OCHS), 7.0-8.3(m, 7H, ArH) 1.2-1.5(t, 3H, CH, of OEt), 2.2(s, 3H, CHs), 3.9-4.l(q, 2H, OCH& 6.8-8.2(m, 7H, ArH)

“In CDCl, for (Ph3P)(HgCl,. 1) and DMSO-ds for others.

Investigation of ortho-tellurated phenols 2695

7 cm3. The solid was separated, washed with hexane and recrystallized from chloroform. Yield, 75%. Elemental analysis and ‘H NMR data are given in Table I.

Synthesis of (2-hydroxy-5-methylphenyl)(aryl) tellurium(W) chlorides

I-(Chloromercury)-2-hydroxy-5methylbenzene (10 mmol) and an equimolar amount of aryl- tellurium(W) chloride (aryl = C6H5, 4-MeOCsH4 or 4-EtOCsH4) were refluxed in dry dioxane for 3- 4 h under a dinitrogen atmosphere. The solution was filtered hot and the filtrate cooled to 05°C for 2-3 h. The HgClz - dioxane adduct separated out and was filtered off. The filtrate was concentrated to 5 cm3 and hexane (50 cm3) was added to the concentrate. The white precipitate resulted, which was filtered, washed with cold ethanol, dried and recrystallized from chloroform. Yield, 75-80%. M.p., elemental analyses, ‘H and 13C{ ‘H} NMR (in CDC13 at 25°C) spectra are given below.

a(Ary1 = C,H,) : m.p. 172°C. Found : C, 41.1; H, 3.1; Te, 33.4 ; Cl, 18.7. Calc. for C, ,H, 20Cl,Te : C, 40.8; H, 3.1; Te, 33.4; Cl, 18.5%. NMR (‘H): 6, 2.2(s, 3H, CH3), 6.7-7.2, 7.47.8(m, 9H, ArH+OH); (‘3C{‘H)): 6, 21.3(CH3), l16.2(C3), 123.3(C,‘), 128.6(C3’), 133.1(C5), 133.8(C,), 134.5(C,‘), 139.1(C2’), 141.4(&), 155.2(C2). C, merges with the CZ’ or Cs signal.

b(Ary1 = 4-MeOC,H,): m.p. 184°C. Found: C, 40.1 ; H, 3.4; Te, 31.6; Cl, 17.1. Calc. for ClqH1402C12Te: C, 40.7; H, 3.4; Te, 30.9; Cl, 17.2%. NMR: ‘H: 6, 2.2(s, 3H, CH3), 3.9(s, 3H, OCH,), 6.8-7.2, 8.1-8.2(m, 8H, ArH+OH). ‘3C(‘H) : 6, 21.8(CH3), 55.7(OCH& 115.6(&), 124.2(C), 128.2(C3’), 133.2(&), 133.9(C4), 134.4(C,‘), 139.6(&‘), 141.5(&), 155.0(&). C, merges with the CZ’ or C6 signal.

c(Ary1 = 4-EtOC6H4) : m.p. 167°C. Found : C, 42.8; H, 3.7; Te, 30.0; Cl, 16.6. Calc. for C,SH1602C12Te: C, 42.2; H, 3.7; Te, 29.9; Cl, 16.8%. NMR: ‘H: 6, 1.41.5(t, 3H, CH3 of OEt), 2.2(s, 3H, CH,), 3.74.l(q, 2H, OCH& 6.8-7.2, 8.1- 8.2(m, 8H, ArH+OH). 13C{ ‘H) : 6, 14.5(CH3 of OEt), 21 .4(CH3), 62.1(OCHJ, aryl carbon signals are similar to that of b.

Synthesis of (2-hydroxy-5_methylphenyl)(aryl) telluride (2)

(ZHydroxy-5-methylphenyl)tellurium(IV) chlor- ide (a, b or c) (10 mmol) was suspended in water (100 cm’) and cooled to 05°C. Sodium meta- bisulphite (10 mmol) dissolved in 50 cm3 water or

hydrazine hydrate (10 mmol) in 50 cm3 ethanol was slowly added to the suspension with stirring. The mixture was further stirred for 2-3 h, keeping the temperature below 5°C. The yellow precipitate of the telluride thus formed was filtered, washed sev- eral times with water, dried and recrystallized from chloroform as yellow crystals. Yield, 75-78%. M.p., elemental analyses, ‘H and 13C{‘H} NMR spectra (in CDC13 at 25°C) are given below.

2a : m.p. 92°C. Found : C, 50.3 ; H, 4.0 ; Te, 40.5. Calc. for C,sH,zOTe: C, 50.1; H, 3.8; Te, 40.9%. NMR : ‘H : 6, 2.2(s, 3H, CH3), 6.7-7.8(m, 9H, ArH + OH). ‘3C(‘H) : 6, 20.4(CH3), 103.1(C,), l14.2(C3, C,‘), 128.9((3,‘), 131.2(C3’), 131.9(C,), 139.8(&), 140.4(&‘), 141.6(&), 154.6(&).

Zb:m.p.98”C.Found:C,49.6;H,4.1;Te,38.0. Calc. for C,,H,,02Te: C, 49.2; H, 4.1 ; Te, 37.3%. NMR: ‘H: 6, 2.2(s, 3H, CH3), 3.8(s, 3H, OCH,), 6.7-6.9, 7.47.5(m, 7H, ArH). ‘3C{‘H): S, 21.0(CH3), 55.6 (OCH& 102.1(C,), 114.3(C3, Cl’), 128.4(C,‘), 131.2(C3’), 131.8(CJ, 139.6(C,), 14O.l(C,‘), 141.4(C,‘), 154.4(C).

2c: m.p. 80°C. Found: C, 50.6; H, 4.5; Te, 36.1. Calc.forC,gH,602Te:C,50.6;H,4.5;Te,35.9%. NMR: ‘H: 6, 1.3-1.4(t, 3H, CH3 of OEt), 2.2(s, 3H, CH3), 3.9-4.O(q, 2H, OCH&, 6&7.5(m, 7H, ArH). 13C{ ‘H} : 6, 14.5(CH, of OEt), 20.8(CH3), 61.8(OCH2), aryl carbons are similar to that of 2b.

Synthesis of mercury(II), palladium(I1) and pla- tinum(I1) complexes of 2

Mercuric chloride (1 mmol) dissolved in 10 cm3 of acetone was added to a solution of 2 (a, b or c) (1 mmol) in acetone (10 cm’) and the mixture was stirred at 40°C for 2 h. The resulting precipitate was filtered, washed with acetone thoroughly and dried in vacua. Yield, 75-80%.

Palladium(I1) complexes were synthesized by stir- ring 2 with (C6HSCN)2PdC12 in chloroform in a manner described above. After stirring 25-30 cm3 of petroleum ether (4060°C) was added to this mixture and the resulting red-brown precipitate was filtered. It was washed with petroleum ether thoroughly and dried in vacua. Yield, 83-85%.

To synthesize platinum(I1) complexes the stirring of a metal ion-ligand mixture was carried out as described above for the mercury complexes, except 2 which was dissolved in acetone and K,PtCI, in water. Thereafter, the volume of mixture was reduced to 5-7 cm3 in vacua. The reddish precipitate was filtered, washed with an acetone-water mixture (1: l), dried and recrystallized from chloroform. Yield, 85-90%.

Elemental analyses, m.p. and ‘H NMR data of all the complexes of 2 are given in Table 1.

2696 A. K. SINGH et al.

RESULTS AND DISCUSSION around 250 cm- ’ in the IR spectrum of this mixed complex further authenticates its formation. The v(OH) was noticed in the IR spectra of all these complexes around 3300-3400 cn- ‘, supporting the ligation of 1 in a bidentate mode.

The reaction of 1 -hydroxy-4-methylbenzene with tellurium tetrachloride always results in an Ar*TeCl, type of compound7 which can easily be reduced with hydrazine to 1. The ortho-mercuration of 1-hydroxy-4-methyl benzene followed by trans- metallation with ArTeCl, results in a good yield of the precursor chloride of 2, which can be reduced to 2 in good yield using Na&05. The OH signal in the ‘H NMR spectrum of 1 is shielded with respect to OH of their precursor chlorides by 1.1 ppm. This may be due to a decrease in the Te c 0 secondary interaction and change in the inductive effect of tellurium, when the chlorides are reduced to tellurides. The OH signal of 2 and its precursor chloride could not be identified separately in the multiplet of phenyl protons with which it merges. However, its shielding on reduction of the precursor chlorides into 2 seems to be lower than that observed in the case of 1, as it does not separate out from the multiplet.

Compound 1 reacts with HgC12 forming a com- plex of stoichiometry [HgCl(l-H)] which has defied all attempts to identify its structure, presumably due to its polymeric nature as it does not dissolve in any organic solvent. However, on refluxing its suspension in methanol with an equimolar amount of PPh,, a complex [Ph,PHgCl(l-H)] results which is soluble in polar organic solvents. The ‘H NMR spectrum of this complex exhibits an OH signal which is negligibly downfield than that of 1. The aromatic protons of 1 on complexation with mer- cury undergo deshielding (0.14.2 ppm), indicating the involvement of tellurium in coordination. Thus, 1 behaves as a mu-negative bidentate ligand in this complex (Structure A). Most probably it also does so in the complex [HgCl(l-H)] and mercury completes the expected four-coordination number with the chlorine or oxygen of the OH group of the neigh- bouring molecule, which ultimately results in poly- merization. It appears that in the absence of free OH most probably the extended polymerization is not sustained. This has been supported by the absence of a v(Hg-Cl(termina1)) band ’ ’ around 300 cm-’ in the IR spectrum of [HgCl(l-H)], whereas this band appears in the IR spectrum of [Ph, PHgCl(l-H)] at 3 15 cm- ’ which supports Structure A for this compound. The occurrence of v(Te-C)”

Since of the two OH groups present in 1 only one participates in its ligation with metal ions, it was thought worthwhile to examine the ligation of 2 because the extended polymerization, complicating the structure of wgCl(l-H)], due to the presence of an additional OH group would be avoided. Com- pound 2 reacts with mercury(II), palladium(I1) and platinum(H) forming complexes of stoichiometry [MCI(ZH)]. In the ‘H NMR of 2 the OH signal was found merged with phenyl, as indicated by enhanced integration of these protons with respect to that of CH3. On complexation such an enhance- ment was absent, indicating the loss of an OH pro- ton on ligation. The aryl protons were deshielded (0.1-0.8 ppm) when 2 ligated with palladium(I1) and platinum(I1). The deshielding was small in the case of the mercury complex (co.3 ppm). These observations after taking into account the solvent effect also suggest that in all three complexes 2 coordinates through tellurium ; the Hg-Te bond is weaker than the Pd/Pt-Te bond and, therefore, the magnitude of deshielding differs. To complete the coordination number four the species having stoichiometry [MCI(Z-H)] most probably dimerize, as depicted in Structure B. Most probably the geometry of ligands around mercury(I1) is tetra- hedral. The coordination number of M as four has been supported in the case of platinum/ palladium(I1) by the electronic spectra of their complexes in DMSO, which exhibit a band around 27 kK, characteristic of square planar geometry around the metal ion. The dimeric form- ulation of Struct. B has been supported by the pres- ence of v(M-Cl(bridging)) bands” around 200, 250 and 270 cm-’ in the IR spectra of the mer- cury(II), palladium(I1) and platinum(I1) complexes, respectively. The v(Te-C) undergoes a red shift (- 10-15 cm- ‘) on complexation of 2 with pal- ladium/platinum(II). This further supports the involvement of tellurium in chelation. The occur- rence of only one v(M-Cl-M) band in the IR spectra of all three complexes suggests that the

M. Hg,?d or Pl

(B) (A)

Investigation of ortho-tellurated phenols 2697

structures of [Pd/PtC1(2-H)], are centrosymmetric (Struct. B).

Acknowledgement-We thank CSIR (India) for the research grant to carry out this work.

REFERENCES

1. S. Ahrland, J. Chatt and N. R. Davies, Q. Rev. Chem. Sot. 1958, 12, 165.

2. R. G. Pearson, J. Am. Chem. Sot. 1963,85,3533. 3. A. K. Singh, V. Srivastava and B. L. Khandelwal,

Polyhedron 1990,9,495 and 85 1. 4. B. L. Khandelwal, A. K. Singh, V. Srivastava, D. C.

Povey and G. W. Smith, Polyhedron 1990,9,2041. 5. A. K. Singh, S. Thomas and B. L. Khandelwal, J.

Coord. Chem. 1990,21,71.

6. N. I. Al-Salim and W. T. McWhinnie, Znorg. Chim. Acta 1989, 1552131.

7. B. L. Khandelwal, K. Kumar and K. Raina, Synth. React. Met.-Org. Chem. 1981, 11, 65.

8. K. J. Irgolic and R. A. Zingaro, Organomet. React. 1971,2, 117.

9. L. G. Makarova and A. N. Nesmeyanov, The organic chemistry of mercury compounds, in Methods of Elementary Organic Chemistry (Edited by A. N. Nesmeyanov and K. A. Kocheshkov), Vol. 4, Ch. 5, p. 94. North Holland, Amsterdam (1967).

10. F. H. Kruse, R. E. Sanftner and J. F. Suttle, Analyt. Chem. 1953, 25, 500; A. I. Vogel, A Text Book of Quantitative Inorganic Analysis, 3rd edn. Longmans, London (1961).

11. K. Nakamoto, Infrared and Raman Spectra of Znor- ganic and Coordination Compounds, 4th edn, pp. 199-324. John Wiley and Sons, New York (1986).

12. K. J. Irgolic, The Organic Chemistry of Tellurium, p. 325. Gordon and Breach, New York (1974).