Gold(III) complexes of dithiooxamide, N,N′-dimethyl-, N,N′-dicyclohexyl-, tetramethyl- and tetraethyl-dithiooxamide

J. inorg, nucl. Chem., 1974, Vol. 36, pp. 1067 1070.PergamonPress. Printedin Great Britain.

GOLD(Ill) COMPLEXES OF DITHIOOXAMIDE, N,N'-DIMETHYL-, N,N'-DICYCLOHEXYL-, TETRAMETHYLAND TETRAETHYL-DITHIOOXAMIDE A. C. FABRETTI, G. C. PELLACANI, G. PEYRONEL and B. SCAPINELLI Istituto di Chimica Gci:erale e lnorganica, University of Modena, Italy (Received 1 June 1973)

Abstract The following new complexes of gold(Ill) with dithiooxamide (DH4), N,N'-dimethyl- (Me2DH2), N,N'-dicyclohexyl- (DCHDH2), tetramethyl- (Me4D) and tetraethyl-dithiooxamide (Et4D) were prepared : [DH4.DH3.Au]CI 2, [MezDH.AuCI21, [DCHDH.AuCIz], [MezDH2.AuBr2]Br, [DCHDH2.AuBr2]Br, [LAuX21 [AHX4] (L = Me4 D, Et4D : X = CI, Br). All complexes are diamagnetic. I.R. spectra show that the complexes of DH4, Me2DH2, DCHDH 2 are S,N-coordinated while those of M%D and Et4D are S,Scoordinated. The far i.r. v(AuN), v(AuS) and v(AuX) bands are tentatively assigned. In DMF solution the [LAuCI2] complexes behave as non-electrolytes, the [LAuBr2]Br and the [LAuXz][AuX4] complexes as 1 : 1 electrolytes. The [DH4. DH3. Au]CI2 complex has a molar conductivity lower than that corresponding to a 2:1 electrolyte, presumably owing to an interaction of the chloride ion with the cationic complex.

INTRODUCTION DITmOOXAMtDEand N,N'-disubstituted dithiooxamides form S,N-coordinated complexes while tetrasubstituted dithiooxamides form S,S-coordinated complexes with d 8 transition metal ions[I-5]. We have extended these previous investigations to the complexes of gold(III) with these three types of ligands using the unsubstituted dithiooxamide (DH4), N,N'-dimethyl- (MezDH2), N,N'-dicyclohexyl- (DCHDHz), tetramethyl- (Me4D) and tetraethyl-dithiooxamide (Et4D).

EXPERIMENTAL The ligands were of pure commercial grade; the tetrasubstituted dithiooxamides were prepared by the method of Hurd et alZ6]. Since it has been demonstrated[I,2] that an acid medium favours the formation of crystalline complexes, strong acids were used at the followingconcentrations : HC1 (37 %), HBr (48 %), HAc glacial. The solid complexes were prepared by adding a solution of a gold(Ill) compound to a solution of the ligand (HL or L) Au(DH3,DH4)CI/: 0.5 mM HAuC14 in 2.5 ml HAc + 1 ml HCI to l m M H L in 50mlHAc; yellow, yield 40";. Au(Me2DH)C12:1 mM HAuCI 4 in 5 ml HAc + 3 ml HCI to 0-5 mM HL in 5 ml HAc, pink, yield 80%. Au(MelDH2)Br a: 0-5 mM Au(OH)3 in 5 ml HAc + 1 ml HBr to 1 mM HL in 5 ml HAc, orange-red, yield 70 %. Au(DCHDH)CI/: 1 mM HAuCI4 in 5 ml HAc + 3 ml HCI to 0.5 mM HL in 30 ml HAc, pink, yield 80%. Au(DCHDHE)Br3:0.5 mM Au(OH)3 in 5 ml HAc + 1 ml HBr to 1 mM HL in 10 ml HAc, orange yellow, yield 75%. Auz(Me4D)Cl6:1 mM HAuC14 in 10 ml HAc + 3 ml HCI to 1 mM L in 20 ml HAc, yellow, yield 20')°; or 1 mM HAuCI 4 in 4 ml HAc + 1.5 ml HC1 to 0.5 mM L in 4 ml HAc, yield 70%. Auz(Me4D)-

Br 6 . ½HAc: 2 mM Au(OH)3 in 1 mt HAc + 3 ml HBr in 1 mM L in 4 ml HAc, deep red, yield 70%. Au2(Et,,D)CI6: 1 mM HAuC14 in 10 ml HAc + 3 ml HCI in 1 mM L in 20 ml HAc, yellow, yield 40'~o. Au2(Et4D)Br6:1 mM Au(OH)3 in 4 ml HBr to 1 mM L in 8 ml HAc, deep red, yield 80 04. The compounds could not be recrystallized and were analysed by conventional methods: analytical results are given in Table 1. Molar conductivities were measured at room temperature with a WTW conductivity bridge. Magnetic susceptibilities were measured with the Gouy method at room temperature and corrected for Pascal constants. I.R. spectra were recorded on the solids in KBr pellets I4000~250cm -l) or Nujol mulls on polythene (600-250 cm-1) with a 521 Perkin-Elmer spectrophotometer and in Nujol mulls on polythene (400-60 cm- 1) with a FIS3 Perkin-Elmer spectrophotometer. RESULTS AND DISCUSSION The square planar diamagnetic complexes ofgold(IlI) with dithiooxamide, dimethyl-, dicyclohexyl-, tetramethyl- and tetraethyl-dithiooxamide have different stoichiometries depending on the type of dithiooxamide and of halide ion from which they are formed. In the majority of cases an interpretation of their structure may be tentatively given on the basis of their i.r. spectra. [Au. D H 4 . DH3]CI 2 Several i.r. bands are split in the complex (Table 2) indicating different situations of the N H 2 , CN and CS bonds in the coordinated molecules of the ligand. The splitting of the v(CN) and v(CS) bands into two bands

1067

A.C. FABRETTI,G. C. PELLACANI,G. PEYRONELand B. SCAPINELLI

1068

Table 1. Analytical data; found ~o (calcd. %); molecular conductivity Au (~)-1 mole-1 cm2): 10-3 M DMF solution Compound Au(DH4.DHa)CI 2 Au(Me2DH)CI2 Au(Me2DH2)Br 3 Au(DCHDH)C12 Au(DCHDH2)Br3 Au2(Me4D)CI6 Au2(Me4D)Br6.½HAc Au/(Et4D)C16 Au2(Et4D)Br 6

Au 38.73(38.75) 47.32(47.34) 34.00(33.68) 35-88(35.67) 27.84(27.32) 50.53(50.32) 36.64(36.49) 46.76(46-97) 35.89(35.63)

C 9.55(9.44) 11.84(11.53) 8.30(8-21) 30.31(30.42) 23.85(23.30) 9.19(9.20) 7.77(7.78) 14.53(14.30) 10.86(10.85)

H 1.62(1.59) 1.76(1-94) 1.53(1.38) 4.42(4.38) 3.68(3.35) 1.70(1.55) 1.35(1-31) "5.54(2.39) 1.96(1.81)

C1 13.54(13-95) 16-58(17.04) 12.41(12-84) 27-01(27.15) 24.90(25.35)

AM

P .....

54 13 73 8 73 84 108 88 85

diam. diam. diam. diam. diam. diam. diam. diam. diam.

Table 2. More relevant i.r. bands of the ligands and their complexes

DH 4 AuLHLCI 2 Me2DHz AuLC12 AuHLBr 3 DCHDH2 AuLCI2 AuHLBr 3 Me4D Au2LCI 6 Au2LBr6.½HAc Et4D

Au2LC16 Au2LBr 6

6(NH2)

v(CN)

1580 vs 1595-1570 sb v(NH) 3179 vs 3182 ms, 3151 ms 3150 wb 3158 vs 3125 mw 3174 w, 3140 w v(CN) 1528 vs 1600 vs 1600 vs, 1583 vs 1498 vs 1595-1582 vs 1590 vs

1423 vs 1520 sh, 1404 m v(CN) 1528 vs 1577 vs, 1387 w 1565 s, 1383 mb 1493 vs 1545 vs 1580-1552 s v(CS) 828 m 805 m 804 m 869 m 844 m 843 m

at higher a n d lower energy indicates an S,N coordination of the ligand to the metal[2]. O n e of the two coordinated dithiooxamide molecules (DH3) has lost a p r o t o n by neutralizing one of the positive charges of the metal ion. The molar conductivity (AM = 54 in D M F ) is rather low for a 2:1 complex (A M = 130-170)[7], but similar low conductivities were also observed for the analogousplatinum(II)complexes, [(DH4)2Pt]C12 = 56 [(MezDH2)2Pt]CI 2 = 67 in D M F [ 4 ] , a n d m a y be due to electrostatic interactions between the highly electronegative chloride ions a n d some positive site of the complex cation, or to a weak coordination of the chloride ion to the metal. The v(AuS) frequencies (341 a n d 312 c m - 1 ) are very close to those of the analogous platinum(II) complex [(DH4)2Pt]C12 (338 a n d 308 cm-1)[4] a n d for b o t h metals the v(AuS) frequencies are lower for the DH4complex t h a n for the N,N'-disubstituted a n d tetrasubstituted dithiooxamides[4], owing to the absence, in the unsubstituted dithiooxamide, of the inductive effect of the alkyl-substituents. The broad b a n d at 409 cm -~, assigned to v(AuN) modes is probably superimposed on the b a n d at 407 c m - i of the ligand, but its value is in good agreement with those observed in the other complexes (Table 4). A l t h o u g h v(AuCl) bands occur in this region of the far infrared spectra (Table 3) it seems very unlikely that one of the two

v(CS) 832 vs 866 s, 820 sh v(RN) 1216 sh, 1112 m 1217 ms, 1103 s 1127 s 1195 ms, 1125 s

c0(NH2)

z(NH2)

700 vs 640 vs 745 mw, 679 vw 648 w, 604 ms v(CS) 867 vs 990 s, 858 ms, 795 ms 991 w, 867 m, 856 sh, 806 s 868 ms 1022 vw, 981 vw 1022 vw, 982 vw, 865 vw

v(AuS) bands m a y be due to v(AuC1) modes of structures like [DH 4 . D H 3 .AuC1]C1 in which one ligand molecule should be m o n o - c o o r d i n a t e d a n d a chloride ion coordinated to the metal. ELAuCI2] and [HLAuBr2]Br (HL = MeeDH2, DCHDH2) These complexes also show a splitting of the v(CN) and v(CS) bands at higher a n d lower frequencies, characteristic of an S,N-coordination. Furthermore, they show new b a n d s at 1200-1220 c m - 1 and 11001130 c m - 1 attributable to v(R-N) frequencies [4] which were consideredE8] as a n indication that in the complexes of the disubstituted dithiooxamides the m e t a l nitrogen b o n d is stronger than the m e t a l - s u l p h u r bond. The m o l a r conductivities of these complexes correspond to those of non-electrolytes for the [LAuCIz] and of 1 : 1 electrolytes (A M = 65-90)[7] for the [LAuBr2]Br complexes. The far i.r. b a n d at 365-375 c m - 1 m a y be attributed to v(AuS) vibration in agreement with other values given in the literature for the Au(III)-S b o n d (Table 4) and the b a n d at 395-400 c m - 1 to v(AuN) vibration, at frequencies m u c h higher than those of the py-Au(III) b o n d a n d a little lower t h a n those given for the [Au(N3)4]- ion (Table 4). A stretching frequency higher for v(AuN) than for v(AuS) accords with the

Gold(Ill) complexes of dithiooxamides

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Table 3. Metal halogen far infrared bands

v6(Eu) Cs[AuCI4] Cs[AuBr,]

vs(B2g)

365 vs, 362 sh 252 vs

[Ph3P.AuCI3] IPh3 P.AuBr3] [Me2tsc.AnCl2]* [Et2tsc.AuCl2]* [Et2dtc.AuBr2] * (Et2dsc.AuBr2]* [(CN)2(py)AuCI] [(CN)z(py)AuBrl EMe2DH.AuCI21 [Me2DH2.AuBr2]Br [DCHDH.AuC121 [DCHDH2.AuBr2]Br [Me4DAuCI2][AuC14] [Me4DAuBr2][AuBr4].½HAc [Et4DAuC12][AuC14] [Et4DAuBrz][AuBr41

v(XAuX)asym

v(XAuX)sym

371 264 331 s 330 s 243 247 v(AuX) 363 vs 250 s 345 s 244 w 351-343 vs -357 vsb 252 vs 360 vs 255 vs

344(?) 222 318 s 317 s 216 222

325 231 326 234 332 223 329 228

187 w v(AuX) 311 202(?)

vv(E,)

v2(h2u)

Ref.

179 vw, 168 vw 108 sh, 100 m

143 m

[9] [9] [ 101 [ 10] [11] Ell] [121 [12]

s ms vs vs ms mw m w

(141 w) (110 s) (139 m) (116 mb) 145 nab 100 w 142 ms 102 mw

[13] [13] This work This work This work This work This work This work This work This work

* tsc = thioselenocarbamato; dtc = dithiocarbamato, dsc = diselenocarbamato. Table 4. Metal nitrogen and metal-sulphur far infrared bands v(AuN) [(Et2dtc)2Au]Br [Et2dtc.AuBr2] [Me2tsc.AuC121 [Me2tsc.AuBr21 [pyAuC13] [pyAuBr3] [Au(N 3)4] [Au.DHg.DH3]CI2 [Me2DH.AuC12] [Me2DH2.AuBrz]Br [DCHDH.AuCI2] [DCHDH2AuBr2]Br [Me4D.AuCI2][AuC141 IMe4D.AuBrE][AuBr4].½HAc [Et4D.AuClzI[AuC14] [Et4D.AuBr2][AuBr4]

249, 239 255 437~426 409 msb, 312 mb 400 ms 397 m 396 m 395 mw

appearance in all these complexes of v(RN) bands which indicate that the A u - N is stronger than the A u - S b o n d [8]. Two other b a n d s in the region 325-350 c m - 1 for the chlorides a n d 230-245 c m - 1 for the bromides (Table 3) m a y be assigned to the two v(AuX) frequencies characteristic for a A u X 2 cis configuration in the structures [LAuC12]a n d [LAuBr2]Br. The presence of a b a n d at 140 cm -1 for the chlorides a n d at l l 0 - 1 1 6 cm -1 for the bromides (Table 3) could suggest the existence in the complexes of [ A u X 4 ] - ions, as in the third class of c o m p o u n d s (Table 4), in structures like (a) [L2AunI][AuCI4] or (b) [(HL)EAul][AuC14] for the chlorides and (c) [(HL)zAuBr2][AuBr4] for the bromides. However, the structures (a) a n d (b) could n o t explain the b a n d at

v(AuS)

Ref.

378 378 384 m 375 m

[ 12] [12] [11] [11] [141 [ 14] [ 14] This work This work This work This work This work This work This work This work This work

341 sb 369 m 366 mb 376 m 376 mw 390 m, 357 vsb 384 m, 360 m 383 m, 352 sh 381 m, 358 w

325 c m - 1 which is absent in the [AuC14]- ion, a n d the very low molar conductivity in D M F , corresponding to that of non-electrolytes. In the cationic complex [(HL)2AuBr2] + of the structure (c) the ligand molecules should be m o n o - c o o r d i n a t e d to the metal, presumably through the sulphur-atom. In such a case neither the splitting of the v(CN) a n d v(CS) b a n d s nor the existence of b o t h v(AuN) a n d v(AuS) b a n d s could be justified.

[LAuX2][AuX4](L

= Me4D, Et4D; X = CI, Br)

The i.r. spectra of these complexes are very similar a n d show an increase in the v(CN) a n d a decrease in the v(CS) frequencies, indicating a sulphur-coordination of the ligand to the metal[l]. The m o l a r conductivities

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A. C. FABRETTI,G. C. PELLACANI,G. PEYRONELand B. SCAPINELLI

(Table 1) correspond to those of 1:1 electrolytes[7]. Two far i.r. b a n d s at 380-390 and 350-360 cm -1 (Table 4) m a y be assigned to v(AuS) frequencies, as expected for a S2-coordination in a C2v symmetry[4]. The b a n d s at 142-145 c m - 1 for the chlorides and 1 0 ~ 102 cm -1 for the bromides correspond very well to those observed (Table 3) for the [ A u X 4 ] - ions. The bands at 329-332 c m - 1 for the chlorides a n d at 252255 cm -1 for the bromide m a y be assigned to the v(XAUX)syra mode of the cation [LAuX2] +, while the very strong b a n d at 357-370 c m - 1 for the chlorides and 252-255 c m - ~ for the bromides may be due to b o t h the [AuX4]- and [LAuX2] + ions (Table 3). Acknowledgement This work was supported by financial aid from the Consiglio Nazionale delle Ricerche of ltaly. REFERENCES

1. G. Peyronel, G. C. Pellacani, A. Pignedoli and G. Benetti, lnorg. Chim. Acta 5, 263 (1971). 2. G. Peyronel, G. C. Pellacani and A. Pignedoli, lnorg. Chim. Acta 5, 627 (1971).

3. A. C. Fabretti, G. C. Pellacani and G. Peyronel, J. inorg. nucl. Chem. 33, 4247 (1971). 4. G. C. Pellacani, G. Peyronel and A. C. Fabretti, Gazz. chim. ital. 102, 11 (1972). 5. G. Peyronel, A. C. Fabretti and G. C. Pellacani, J. inorg. nucl. Chem. 35, 973 (1973). 6. R. N. Hurd, G. De La Mater, G. C. McElheny, R. J. Turner and V. H. Wallingford, J. org. Chem. 26, 3980 (1961). 7. W. J. Geary, Coord. chem. Rev. 7, 81 (1971). 8. H. O. Desseyn, W. A. Jacob and M. A. Herman, Spectrochim. Acta 25A, 1685 (1969). 9. A. Sabatini, L. Sacconi and U. Schettino, lnorg. Chem. 3, 1775 (1964). 10. D. R. Williamson and M. C. Baird, J. inorg, nucl. Chem. 34, 3393 (1972). 11. N. Sonoda and T. Tanaka, J. inorg, nucl. Chem. 35, 1145 (1973). 12. J. G. M. Van der Linden and W. P. Nijssem Z. anorg. allg. Chem. 392, 93 (1972). 13. T. Boschi, B. Crociani, L. Cattalini and G. Marangoni, J. chem. Soc. (A), 2408 (1970). 14. J.R. Ferraro, Low-frequency Vibrations of lnorganic and Coordination Compounds, pp. 208, 235. Plenum Press, New York (1971).