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An i.r. spectral study on the complexes of arsenic (III), antimony (III) and bismuth (III) with tetramethyl- and tetraethyl-dithiooxamide
spectrochimlca~cta,Vol.20A,pp.1722 to1720. PergamonPresalQ74. PrhtedinNorthern Irehd
An i.r. spectral study on the complexes of arsenic (m>, antimony (III) and bismuth (III) with tetramethyland tetraethyl4ithiooxamide Grow10
ANTONIO C. FABRETTI and GIAN CARLOhILACAN1
PEYRONEL,
Istituto di Chin&a Genersle e Inorganica, University of Modena, 41100Modena, Italy (Received28 Decmbw 1973) Abstract--The following complexee of tetramethyldithiooxamide (Me‘D) and tetraethyldithiooxsmide (E&D) with arsenic (III), antimony (III) and bismuth (III) were prepared: AsLX, (L = MebD, Et,D; X = Cl, Br), SbLXs (L = Me,D, Et,D; X = Cl, Br, I), Bi(Me,D)&Ys (X = Cl, Br), BiEt,DXs (X = Cl, Br, I) and M(Me,D),(ClO,), (M = As, Sb, Bi). The infrared v(CN)and v(CS) and two v(W) bands indicate that the ligands are S,S-coordinated to the metal in a c&position. A third far infraredband, mass-sensitiveand aonstant for the complexes of the 88KI6 metal with both ligands, is attributed to a ring deformation of the structuralunit
Three v(AsX) bands seem to indicate that the AsLX, complexes have a dimeric halogenbridged structure with a deformed octahedral coordination around esch metal atom. Two or three r(MX) bands seem to indicate that the complexes SbLX, and BiEt,DXs have a distorted square pyramidal coordination with the lone electron pair in the sixth octahedral position. No ressonable conclusioncould be reaohedabout the coordinationof the Bi(Me,D),X, complexes.
INTRODUCTION
act as 8,B-chelating ligands with several transition metals [l]. They may also be suitable ligands for the preparation of S&coordinated complexes of non-transition metals. We therefore prepare some complexes of arsenio (III), antimony (III) and bismuth (III) with tetramethyl-(Me,D) and tetraethyl-dithiooxamide (Et,D) and studied them comparatively by infrared and conductometric methods. Infrared data for sulphur-coordinated complexes of these metals are rather poor.
TETRULKYLDITEIOOXAXIDES
EXPERIMENTAL
The preparation of the complexes was carried on with pure chemical grade reagents; acid used: HAo glacial, HC137 %, HBr 48 %, HI 66 %, HClO, 60 %. The compounds JfLX, (N = As, Sb, Bi; L = Me,D, Et&D; X = Cl, Br, I), were prepared mostly by mixing a warm solution of 2 rnM of AsaOI, Sb,Os (BiO)&O, - *II,0 respectively in 4 ml HX to a warm solution of 2 rnM of L in 10 ml of HAc. A yellow crystalline precipitate is formed by cooling or, in the case of the arsenic bromides, by stirring the oil originally formed. In the case of AsEt,DX, (X = Cl, B r ) complexes, 2 mM As,O, and 4 mM Et4D were used in the same volumes of solvents. In the case of BiEt,DX, oomplexes, the following quantities were used: 6 mM (BiO)$O, - gH,O in 6 ml HCl to 2 mM L in 10 ml HAc, [l] G.PEYRONEL,G.C. (1971).
F'ELLACANI,
A.
PIQNEDOLI
1723
and G. BENEYFJX,IWX~.C%~.Acta 6, 263
1724
GIORUIOPEYBONEL,
ANTONIO C. FAB~ETTI
and GLU CABLOPEIJAIJAM
2 m&r(BiO),CO, - iH,O in 4 ml HBr (or HI) to 4 mM L in 15 ml HAc. The compounds Bi(Me,D)J, (X = Cl, Br) were prepared by mixing a solution of 2 rnM --(BiO)&O, - +H,O in 4 ml HX with a solution of 2 rn~ L in 10 HAc. The perchlorates were obtained as follows: -As(Met,D),(ClO,),: by dissolving little by little 2 mM of solid Me,D to a warm solution of 1 mm As,O, in 2 ml HClO, + 4 ml HAc; a microcrystalline yellow product is immediately formed; Sb(Me,D),(ClO,), by adding -_ 7 mildof solid Et,D to a warm solution of 1 mar of Sb,O, in 6 ml HCIOl + 10 ml HAc and stirring; Bi(Me,D),(ClO,), by mixing a solution of 1 mM of (BiO),CO, . P_ #H,O in 4 ml HClO, to a solution of 3 rnMof Me,D in 10 ml HAc; with the addition of ethyl ether, a yellow brown precipitate was obtained after 24 hr. With Et,D no crystalline precipitates, but only orange solutions were obtained. Table
1. Anslyticsl results, found y. and (calo.%), and molar conductivitiesA,( aA1 mol-l cma), mostly in lo* M nitrobeneenesolution
Compound
M
AsMe,DCI, ALlMe.,DBr, ~~~@@u,+ AaEt:DB:* SbMe,DCJ SbMe,DBr, SbMe,DI, sb(=,D),(Cl%),t SbEt,DCl, SbEt,DBr, SbEt,DI, Bi(bfe,D),Cl, Bi(Me,D),Br, Bi(Me~D)#-W)~ BiEt,DCl, BiEt,DBr, BiEt,DI, *N%:
C
H
19.49(20.14) 14*88(14-67)
3*42(3*38) 2*47(2*46)
29.78(29.02) 22*04(21*94) 18*38(17-81) 13*73(13*39) 10*04(10.61)
5.M(4.88) 3*71(3*69) 3*13(2*99) 2*28(2-26) 1*67(1*78)
26.61(26.06) 20*62(20*21) 16*68(16*33) 21*48(21*66) 17*84(17*97)
4*62(4-38) 3*64(3*39) 2*82(2*74) 3*73(3*62) S.OS(3.02)
22.31(21.91) 17.60(17*62) 14*61(14*60)
S*SS(S.SS) 3*14(2*96) 2.54(2*46)
S
X
21*00(21*33)
31*04(31*29) 26.13(26*08) 19*82(20*17) 37*76(38-16) 30*26(30*69) 26*11(26.42)
9*09(9*32); 7 N%:
8*87(8*86); $, IO-*arinDMF;
8*98(9.46) 20*02(20*28)
8.96(8.73) 19.12(19.21) 16~11(16~01) 18.64(18*67) 11.98(11.71) 9*69(9*42) 7*74(7*80)
4 6. lo-4ninaoetone:
29.03(29.76) 48*98(48*84) 11~90(11~79) 2&12(26.72) 43.96(43*83) 26*93(26-31) 44.32(44-68) 66*26(66*09) 11*06(11-21) 23.27(23*10) 40.63(40*37) 62*07(61~81)
10*43(10*27)
M 0.4 0.7 dec. 0.4
* A.:$ deo. 1.96 202$ 0.6 0.8 11*8# 1.38 1.69 90 deo. 11 1.36 1.64 l-70
116. IO-‘Yinmethylcellosolve.
The compounds were analysed by standard methods (Table 1). Conductivities were measured with a WTW conductivity bridge. The infrared spectra were recorded in KBr pellets (4000-250 cm-l) or nujol mulls on polythene (600-250 cm-l) with a Perkin-Elmer 621 spectrophotometer and in nujol mulls on polythene (400-60 cm-l) with a Hitachi-Perkin-Elmer FIS3 spectrophotometer. RESULTS AND DISCUSSION The complexes MLX, were obtained for As (X = Cl, Br; L = Me,D, Et,D) It is Sb (X = Cl, Br, I; L = Me,,D, Et,D), Bi (X = Cl, Br, I; L = Et,D). remarkable that Bi(II1) with Me,D only gives the solid complexes B&,X, (X = Cl, Br): this may be due either to the greater basicity of the ligand Me,D [l] or to the possibility that Bi(II1) has a greater coordination number. The greater basicity and the lower steric hindrance of Me&D[l] seems to be responsible for the fact that only Jf(Me,D),(ClO,), complexes may be obtained in the solid state. The low molar conductivities (Table 1) of the halides indicate that these complexes behave in solution as non-electrolytes and that the halide ions are coordinated to the metal.
An i-r. spectral study on the complexes of arsenic (III), antimony (III) and bismuth (III)
1726
Table 2. Principal infrared bands (cm-l) of the lig8nda and their complexes VW) Me,D = L AsLCl, AsLBr, ~L,(ClW, SbLCl, SbLBr, SbLI, SbL,(Cl%), BiL,Cl, BiL*Br, BiL,(ClO,), Et,D = L AaLCl, AaLBr, SbLCl, SbLBr, SbLI, BiLCl, BiLBr, BiLI,
ww
1528 “8 1632 “8 1630 vs 1696 8, 1660 8 1640 VB 1633 “8 1639 vsb 1594 8, 1660 B 1662 VB, 1640 VB 1664 vs. 1643 vs 1686 vs, 1666 vs 1498 “8 1630 sh, 1600 vs 1620 sh, 1604 v8 1608 “S 1640sh,1620ve,1610sh 1636 vs. 1614 VB 1546 sh, 1523 va, 1608 sh 164Osh,1622ve, 1608sh 1640 vs. 1620 vs
828 m 818 ms 816 ms 808 ms 816 ms 814 ms 809 m 807 m 818 m 819m 809 m 869 m 861 m 862 m 863 m 866 m 864 m 868 m 866 m 863 mw
The infrared spectra (Table 2) show that the ligands are sulphur-coordinated to the metal. The band at about 1600 cm-l, which has a high Y(CN) oontribution, is shifted in the complexes to higher energies (5-66 om-l) while the band at 828 or 869 cm-l with a high r(CS) contribution is shifted to lower frequenoies (10-20 cm-l). In the complexes Bi(Me4D),X, and blL,(C104)1, the v(CN) band is split into two or three bands and its increase in wave number is greater than for the oomplexes MLX,. This may indicate that the mesomeria shift N=G-S+ is sensitive both to the difference in the coordination geometry of the ligand molecules to the metal and to the presence of halide ion in the coordination sphere of the metal reducing the electronic shift in the NCS group. Both ligands show many infrared bands in the region below 400 om-l. Some new infrared bands, observed in the spectra of the complexes and due to the complexation, are reported in Tables 3 and 4. At least two Y(MS) bands (Table 3) may be identified for the complexes of the three metals, regardless of their stoichiometry. Their attribution may be considered safe, as they are sufficiently constant for each metal. They are independent of the Table 3. Far infrared bands (cm-‘) attributable to v(MS) modes and ring deformation L = MelD
MLCI,
MLBr,
MLCI,
NLBr,
344 mw 266 m8 179 “S
337 vsb 293 vsb 186 Ins
330 VW 274 “8 208 vs
306-283vsb 243 s
ML,(CIO,)~
ring
332 vab 292 vsb 187 B
332 mb 266 s 187 sb 336 mbP 316 wb 262 m8
312 wb
v(MS)
292 vsb 260 vsb
320 mb 267 mb
ring
146 sb
160 sh
164 vsb
166 vsb
v(MW As
Sb
ML&l,
Bi
MLI,
ML,Br,
330 sb?
326 sbl
v(MS)
248 VB 224 m
246 B 228 sh
ring
122 mb
129 vsb
L = EtaD
JfLI,
29P288 mb 288-280 wb 249 m 246 m
160 s 140 ms
167 vsb
164 vsb
260 s 231 s
266 ma 228 wb
246 m 230 w
127 sb
136 vs
121 V8
367 ml 336 VW? 286 wf 263 228 164 121
s VW vsb VW
1726
ANTONIO C. FABRIKCTI and GIAN CARLOPELLACANI
GIORUIO PEYRONEL,
Table 4. Far infrared bands (cm-l) attributable to v(MX) modes L = MQD v(AsX)
v(SbX)
MLCI,
MLBr,
374 vs 320 vsb
246 vs 224 VW
369 vs 337 vsb
167 m
128 ma
174m
340 vs 292 vsb
230 vs? 202 vs 180 s
ML&l,
MLIs
L = Et,D
164 vsb 130 sh
MLI,
249 vs
227 vs 126 ms
336 vs 209 vs 305-283 vsb 183 s
164 vsb 136 vs
MLasr2
308 sb? v(BiX)
MLBr,
MLCl,
178 vsb
277 vs 211 s 174 vs
166 s
176s 162 s 136 vs
137 s 121 vs 88 w
halide ion coordinated to the metal and correspond very well to the values observed for the perchlorate complexes. The higher and lower frequencies may be assigned to a Y(MS) asymmetric and Y(MS) symmetric mode, respectively. They are mass sensitive as is shown in Fig. 1. The literature has very few data regarding the v(MS) frequencies of these metals in complexes comparable to those here described. A *(BiS) asym. frequency of 271 (vs) cm-l is reported, for instance, for the Bi(II1) tris-W-diethyldithiophosphate (dtp) [2]. This value is greater than those observed at about 260 cm-l for these complexes because the dtp-complex is an “inner” oomplex with a four-membered ring. A third band is observed at 208-179, 166-146 and 127-121 cm-l for the three series of complexes (Table 3) both in the perohlorates and in the halides. For the rinq drf.
,
9(M_S)
,
_/
Sb
Bi
-
/
I
100
200
I 300
cc
Fig. 1. Correlationbetween the v(W) and ring deformation bands of the MeaD and EtaD complexes of As(III), Sb(III), Bi(III). [2] D. M. ADUS and J. B. CORNELI,J. Chem. 5’00. (A), 1299 (1968).
An
i.r. spectralstudy on the complexes of amenio (III), antimony (III) and bismuth (III)
1727
same metal the frequency of this band is independent of tbe ligand and of the coordinated halide ion. This band is also mass-sensitive, as are the Y(MS) bands (Fig. l), and must involve the metal atom. It may therefore be attributed to some -\ M common to all the complexes and is vibrational frequency of the ring 1 C--S7 indicated as “ring deformation”. The new band at 336-326 om-l observed for the Me,D-complexes SbMe,DBr, (mb), Bi(MedD)2XB(X = Cl, Br) (sb) and Bi(Me,D),(ClO& (VW)oannot be attributed to Y(MS) modes, for it is not mass-sensitive and too high for a v(BiS) frequency; nor can it be attributed to y(iUX) modes, particularly in the case of Bi(MelD),XI, which is strong, because it is independent of the halogen and too high for a v(BiX) mode. It could therefore be admitted that this band is a ligand-band activated by complexation depending on the conditions of coordination, which should be most favourable in the case of the Bi(Me&D),X, complexes. For the Bi(Me,D),(ClO,), complex, the new band at 367 (m) cm-l is higher than the Y(AsS) value and cannot be attributed to v(BiS) modes; only the new band at 286 (w)cm-’ could be attributed to v(BiS) modes in view of the multiplicity of the Bi-S bonds in this complex. All the A&X, complexes show three new bands which can be attributed to v(AsX) modes; they regularly decrease from the chloride- to the bromide-derivatives (Table 4) with very close values in the MelD- and Et,D-complexes. Very few arsenio trihalide complexes with a stoichiometry similar to the present oomplexes were studied from a structural point of view. An X-ray structural determination has shown that the complex AsCl, 0bipyridil consists of dimerio moleoules with bridging halogen atoms and no stereochemically active lone pair [3, 41. In the far infrared spectra of the complexes AsX&[X = Cl, Br; L = 2,2’-bipyridil (bipy), IJO-phenanthroline (phen) and o-phenylene-bisdimethylamine (diamine)], the following bands were attributed [3] to arsenic-halogen stretching modes:
x = AsX,*bipy AsX,-phen AsX,&anine
r-31 [31 [3]
Cl
314 s 367 8 365 a
X = Br 285 s 265 zs
but because of the Iow symmetry of the complexes, no firm stereoohemical conclusions were drawn. These v(AsX) values agree well with the frequency of the first v&X) band of the present complexes (Table 4). In the case of the complex anions AsX, Y- (X = Cl or Br ; Y = Cl or Br), the following assignments were x Y I/ made [6] on the basis of a C, symmetry of the structure z---As PX [3] M. J. DEVENEY md M. WEBSTER,J. C&m. Sot. (A), 1843 (1970). [4] J. U. CAMERONand R. C. G. KILLEAN, CT@ Stmet. Cowmun. 1,31 (1972). [6] CL Y. AELIJAH and M. GOLDSTEIN,J,. Chern. Sot. (A), 2590 (1970).
1728
GIOEUIO PEYRONBL, ANTONIO C. FABRETTI and GIANC-0
PELLA~ANI
AsC&,Br-[S-j AsBr,Cl- [S] vswaz&a %,(~X),, VWX) VWY)
378mw 297mah 320vs 266mw
247ah? 236vs, 222sh 208 w ,326mb
Also in this case there is a good correspondence between some of the values listed above and the first two frequencies observed for the present complexes (Table 4). The third band observed for the tetrasubstituted dithiooxamides complexes at 167-174 cm-l for the trichloride and 128-126 for the tribromide may well correspond to some d(MX) modes, but it is probably safer to hypothesize that, since the stoichiometry of the complexes is very similar to the complex A&&-bipy [3, 41, these bands may correspond to Y&X) bridging mode, and that these complexes may have a dimeric halogen-bridged structure of the type
with no stereochemically active lone-pair, and a deformed octahedral coordination. If such a structure is true the following assignment of the three bands could be made : I band = ~,(Asx),, II band = r,,(AsX),, III band = Y(AsX) bridging. The SbX,-complexes show (Table 4) two Y(SbX) bands which have close values for the corresponding Me,D- and E&D-complexes. The Sb(Me,D)Br, complex shows a third band at 230 cm-l which may be attributed to a v(SbBr) mode. These bands are mass-sensitive (Table 4). The frequencies of these bands are in good agreement with those observed for the following SbX,& and SbX&L complexes [X = Cl, Br ; L = y-butyrolactam (BuL), dimethylsulfoxide (DMSO) ; L-L = benzothiazole (BT), S-amino-benzothiazole (ABT), benzimidazole-2-thiol (BIT), benzothiazole-2-thiol (BTT)] SbX,(BuL), [6] SbX,(DMSO), [7] SbX,.BT [S] SbX,.ART [8] SbX,*BIT [8] SbX,*BTT [8] (R) = Reman
x -cc1 330mw, 309mw 300 sb, ~250 s 313 s, 293 s 304s 329s 320s
X = Br 234ms(R), 205 vs(R), 155 s
210 s 212m 213s 212 m
The SbX,(BuL)s [0] and SbX,(DMSO), [7] complexes were interpreted as having a distorted square pyramidal coordination with a stereochemically active electron pair occupying a sixth position, like those established by X-ray analysis for SbC1,2and SbCl,(Ph,AsO), 171. The i.r. band observed [9] for SbCl,(Ph,PO) (272s, 257s cm-l [6] S. T. YUANend S. K. MADAN, Inorg. Chim. Aota 3, 463 (1972). [7] R. P. OERTE~,Spctroohim. Acta 26A, 659 (1970). [S] A. OUCHI, T. TAKEUCEIand I. TAXIKAGA,BUZZ.Chin. Soo. Japan 48,284O (1970). [9] S. MILIOEV and D. HAD&,1morg.iVzcol. Cti. Lett. 7, 746 (1971).
An i.r. spectralstudyon the complexesof arae& (III), eutimony (III) and bismuth(III)
1729
and SbCl,(Ph&O), (224s, 209s cm-l) are rather low for the antimony-chlorine stretching but they can be accepted in view of the strong bonding between antimony and the ligand, especially PhJsO. For the SbX,-complexes of BT, ABT, BIT, BTT [S] no deilnite structures were proposed. It is likely that the Me,D- and Et,D-complexes of SbXI also have a distorted square pyramidal coordination with the lone pair stereochemically active in a sixth position
In the case of the SbMe,DBr, complex, the three bands could be due to v(SbBr),,,,, v(SbBr),, and Y(SbBr), modes. The possibility of a dimerid halogen-bridged structure has to be excluded owing to the high value of the third band (180 cm-l) the frequency of which is even higher than the y(AsCl) bridging frequency of the complex AsMe,DCl,. In the case of the SbCl,- and SbI,-complexes too, a third band may be masked under the very strong, broad bands indicated in Table 4. The bismuth trihalide complexes correspond to two different stoichiometries: B&X, for L = MerD and BiLX, for L = Et*D. Both types of complexes have a very low conductivity (Table 1)in nitrobenzene solution. This could mean that in the first type of complex either the metal has a seven-coordination [si(S,)&,] or that one ligand molecule is monocoordinated pi(S,, S)X,] or not coordinated [Bi(S,)Cl,]L or that one halide ion is not coordinated in the solid [si(S,)&]X. In this last case, a displacement reaction should occur in solution: [si(S,),X,]+ + X- + [Bi(S,)X,] + L. It is rather d8icult to chose between these different possibilities simply on the basis of the far infrared spectra. In the case of the Bi(Me,D),X, complexes, the far i.r. spectra reveal a strong broad band at 330326 cm-l which seems to be a new activated band of- the ligand, a strong broad band at 308 cm-l, which may correspond to the very strong ligand band at 310 cm-l and in the case of the BiCl,-complex could mask a Y(BiCl) band. For both complexes only one band can be surely considered to be due to a v(BiX) mode. No stereochemical models may be proposed for these complexes. The BiEt,DX, (X = Cl, Br, I) complexes show three mass sensitive bands attributable to v(BiX) modes (Table 4). The band frequencies observed for the trichloride lie in the range of those given for other BiCl,,L, (z = 1, 2, 2.6) complexes (L = y-butyrolactam, dimethylsulfoxide, Ph,PO and Ph,AsO) v(BiX) BiC&(BuL),., BiCl,(Ph,PO) BiCl,(Ph&sO), BiCl,(DMSO), BiBr,(DMSO), (R) = Raman
[6] [Q] [Q] [7] [7]
286 273 289 271 176
ms, 210 vs(R), 196 sh(R) m, 235 s mw m, -250 s(l) vs(R), 160 s, 148 m(R)
1730
Groacno PE~NEL,
ANTONIOC. FABRETTIand GIAN CARLOPELLAUNI
The BuL-complex was considered [6] as a dimer with one BuL acting as a bridging group connecting two BiCl,(Bti),., units in a pseudo-octahedral symmetry. Largely because of the Raman evidence it was assumed that the trans symmetry for the Bi-Cl bonds is the more likely. For the BiCI,(Ph,PO) complex a trigonal bipyramidal arrangement with three chllrine atoms in the equatorial and the ligand and the lone electron pair in the axial position (0, symmetry) was proposed [9]. For the BiCl,(Ph,AsO), complex a polymer octahedral structure was assumed [9] with a trans position of the ligands in the equatorial plane, the octahedra being linked by the axial chlorine atoms. The BiX,(DMSO), complexes were considered [7] isomorphous with the SbBr,[DMSO)B complexes, and their most probable structure was assumed [7] to be based on an octahedron with trans DMSO groups and one position occupied by a non-bonding electron pair. Unfortunately, their far infrared spectra were cut at 250 cm-l and only their Raman spectra are available at lower frequencies. In the BiEt,DX, (X = Cl, Br, I) complexes, the chelating ligand gives in a monomeric structure two cis M-S bonds in agreement with the two Y(MS) observed bands. No model among those cited above could therefore completely interpret their structure. It may reasonably be assumed that the first two r(BiX) bands correspond to the asymmetric and symmetric stretching vibration of two cis BiX bonds in the same plane of the two cis BiS bonds. The third v(BiX) frequency seems to be too high for v(BiX) bridging bonds in view of the Y(AsX) bridging frequencies observed for the same type of As(III)-complexes. It is therefore likely that the third v(BiX) band corresponds to an axial r(BiX) stretching vibration in agreement with a pseudo-octahedral coordination
in which the sixth position is occupied by a lone electron pair. Aokmwledgemenkis Ricerche of Italy.
work received the financial support of the Consiglio Naziomle de&
An i.r. spectral study on the complexes of arsenic (m>, antimony (III) and bismuth (III) with tetramethyland tetraethyl4ithiooxamide Grow10
ANTONIO C. FABRETTI and GIAN CARLOhILACAN1
PEYRONEL,
Istituto di Chin&a Genersle e Inorganica, University of Modena, 41100Modena, Italy (Received28 Decmbw 1973) Abstract--The following complexee of tetramethyldithiooxamide (Me‘D) and tetraethyldithiooxsmide (E&D) with arsenic (III), antimony (III) and bismuth (III) were prepared: AsLX, (L = MebD, Et,D; X = Cl, Br), SbLXs (L = Me,D, Et,D; X = Cl, Br, I), Bi(Me,D)&Ys (X = Cl, Br), BiEt,DXs (X = Cl, Br, I) and M(Me,D),(ClO,), (M = As, Sb, Bi). The infrared v(CN)and v(CS) and two v(W) bands indicate that the ligands are S,S-coordinated to the metal in a c&position. A third far infraredband, mass-sensitiveand aonstant for the complexes of the 88KI6 metal with both ligands, is attributed to a ring deformation of the structuralunit
Three v(AsX) bands seem to indicate that the AsLX, complexes have a dimeric halogenbridged structure with a deformed octahedral coordination around esch metal atom. Two or three r(MX) bands seem to indicate that the complexes SbLX, and BiEt,DXs have a distorted square pyramidal coordination with the lone electron pair in the sixth octahedral position. No ressonable conclusioncould be reaohedabout the coordinationof the Bi(Me,D),X, complexes.
INTRODUCTION
act as 8,B-chelating ligands with several transition metals [l]. They may also be suitable ligands for the preparation of S&coordinated complexes of non-transition metals. We therefore prepare some complexes of arsenio (III), antimony (III) and bismuth (III) with tetramethyl-(Me,D) and tetraethyl-dithiooxamide (Et,D) and studied them comparatively by infrared and conductometric methods. Infrared data for sulphur-coordinated complexes of these metals are rather poor.
TETRULKYLDITEIOOXAXIDES
EXPERIMENTAL
The preparation of the complexes was carried on with pure chemical grade reagents; acid used: HAo glacial, HC137 %, HBr 48 %, HI 66 %, HClO, 60 %. The compounds JfLX, (N = As, Sb, Bi; L = Me,D, Et&D; X = Cl, Br, I), were prepared mostly by mixing a warm solution of 2 rnM of AsaOI, Sb,Os (BiO)&O, - *II,0 respectively in 4 ml HX to a warm solution of 2 rnM of L in 10 ml of HAc. A yellow crystalline precipitate is formed by cooling or, in the case of the arsenic bromides, by stirring the oil originally formed. In the case of AsEt,DX, (X = Cl, B r ) complexes, 2 mM As,O, and 4 mM Et4D were used in the same volumes of solvents. In the case of BiEt,DX, oomplexes, the following quantities were used: 6 mM (BiO)$O, - gH,O in 6 ml HCl to 2 mM L in 10 ml HAc, [l] G.PEYRONEL,G.C. (1971).
F'ELLACANI,
A.
PIQNEDOLI
1723
and G. BENEYFJX,IWX~.C%~.Acta 6, 263
1724
GIORUIOPEYBONEL,
ANTONIO C. FAB~ETTI
and GLU CABLOPEIJAIJAM
2 m&r(BiO),CO, - iH,O in 4 ml HBr (or HI) to 4 mM L in 15 ml HAc. The compounds Bi(Me,D)J, (X = Cl, Br) were prepared by mixing a solution of 2 rnM --(BiO)&O, - +H,O in 4 ml HX with a solution of 2 rn~ L in 10 HAc. The perchlorates were obtained as follows: -As(Met,D),(ClO,),: by dissolving little by little 2 mM of solid Me,D to a warm solution of 1 mm As,O, in 2 ml HClO, + 4 ml HAc; a microcrystalline yellow product is immediately formed; Sb(Me,D),(ClO,), by adding -_ 7 mildof solid Et,D to a warm solution of 1 mar of Sb,O, in 6 ml HCIOl + 10 ml HAc and stirring; Bi(Me,D),(ClO,), by mixing a solution of 1 mM of (BiO),CO, . P_ #H,O in 4 ml HClO, to a solution of 3 rnMof Me,D in 10 ml HAc; with the addition of ethyl ether, a yellow brown precipitate was obtained after 24 hr. With Et,D no crystalline precipitates, but only orange solutions were obtained. Table
1. Anslyticsl results, found y. and (calo.%), and molar conductivitiesA,( aA1 mol-l cma), mostly in lo* M nitrobeneenesolution
Compound
M
AsMe,DCI, ALlMe.,DBr, ~~~@@u,+ AaEt:DB:* SbMe,DCJ SbMe,DBr, SbMe,DI, sb(=,D),(Cl%),t SbEt,DCl, SbEt,DBr, SbEt,DI, Bi(bfe,D),Cl, Bi(Me,D),Br, Bi(Me~D)#-W)~ BiEt,DCl, BiEt,DBr, BiEt,DI, *N%:
C
H
19.49(20.14) 14*88(14-67)
3*42(3*38) 2*47(2*46)
29.78(29.02) 22*04(21*94) 18*38(17-81) 13*73(13*39) 10*04(10.61)
5.M(4.88) 3*71(3*69) 3*13(2*99) 2*28(2-26) 1*67(1*78)
26.61(26.06) 20*62(20*21) 16*68(16*33) 21*48(21*66) 17*84(17*97)
4*62(4-38) 3*64(3*39) 2*82(2*74) 3*73(3*62) S.OS(3.02)
22.31(21.91) 17.60(17*62) 14*61(14*60)
S*SS(S.SS) 3*14(2*96) 2.54(2*46)
S
X
21*00(21*33)
31*04(31*29) 26.13(26*08) 19*82(20*17) 37*76(38-16) 30*26(30*69) 26*11(26.42)
9*09(9*32); 7 N%:
8*87(8*86); $, IO-*arinDMF;
8*98(9.46) 20*02(20*28)
8.96(8.73) 19.12(19.21) 16~11(16~01) 18.64(18*67) 11.98(11.71) 9*69(9*42) 7*74(7*80)
4 6. lo-4ninaoetone:
29.03(29.76) 48*98(48*84) 11~90(11~79) 2&12(26.72) 43.96(43*83) 26*93(26-31) 44.32(44-68) 66*26(66*09) 11*06(11-21) 23.27(23*10) 40.63(40*37) 62*07(61~81)
10*43(10*27)
M 0.4 0.7 dec. 0.4
* A.:$ deo. 1.96 202$ 0.6 0.8 11*8# 1.38 1.69 90 deo. 11 1.36 1.64 l-70
116. IO-‘Yinmethylcellosolve.
The compounds were analysed by standard methods (Table 1). Conductivities were measured with a WTW conductivity bridge. The infrared spectra were recorded in KBr pellets (4000-250 cm-l) or nujol mulls on polythene (600-250 cm-l) with a Perkin-Elmer 621 spectrophotometer and in nujol mulls on polythene (400-60 cm-l) with a Hitachi-Perkin-Elmer FIS3 spectrophotometer. RESULTS AND DISCUSSION The complexes MLX, were obtained for As (X = Cl, Br; L = Me,D, Et,D) It is Sb (X = Cl, Br, I; L = Me,,D, Et,D), Bi (X = Cl, Br, I; L = Et,D). remarkable that Bi(II1) with Me,D only gives the solid complexes B&,X, (X = Cl, Br): this may be due either to the greater basicity of the ligand Me,D [l] or to the possibility that Bi(II1) has a greater coordination number. The greater basicity and the lower steric hindrance of Me&D[l] seems to be responsible for the fact that only Jf(Me,D),(ClO,), complexes may be obtained in the solid state. The low molar conductivities (Table 1) of the halides indicate that these complexes behave in solution as non-electrolytes and that the halide ions are coordinated to the metal.
An i-r. spectral study on the complexes of arsenic (III), antimony (III) and bismuth (III)
1726
Table 2. Principal infrared bands (cm-l) of the lig8nda and their complexes VW) Me,D = L AsLCl, AsLBr, ~L,(ClW, SbLCl, SbLBr, SbLI, SbL,(Cl%), BiL,Cl, BiL*Br, BiL,(ClO,), Et,D = L AaLCl, AaLBr, SbLCl, SbLBr, SbLI, BiLCl, BiLBr, BiLI,
ww
1528 “8 1632 “8 1630 vs 1696 8, 1660 8 1640 VB 1633 “8 1639 vsb 1594 8, 1660 B 1662 VB, 1640 VB 1664 vs. 1643 vs 1686 vs, 1666 vs 1498 “8 1630 sh, 1600 vs 1620 sh, 1604 v8 1608 “S 1640sh,1620ve,1610sh 1636 vs. 1614 VB 1546 sh, 1523 va, 1608 sh 164Osh,1622ve, 1608sh 1640 vs. 1620 vs
828 m 818 ms 816 ms 808 ms 816 ms 814 ms 809 m 807 m 818 m 819m 809 m 869 m 861 m 862 m 863 m 866 m 864 m 868 m 866 m 863 mw
The infrared spectra (Table 2) show that the ligands are sulphur-coordinated to the metal. The band at about 1600 cm-l, which has a high Y(CN) oontribution, is shifted in the complexes to higher energies (5-66 om-l) while the band at 828 or 869 cm-l with a high r(CS) contribution is shifted to lower frequenoies (10-20 cm-l). In the complexes Bi(Me4D),X, and blL,(C104)1, the v(CN) band is split into two or three bands and its increase in wave number is greater than for the oomplexes MLX,. This may indicate that the mesomeria shift N=G-S+ is sensitive both to the difference in the coordination geometry of the ligand molecules to the metal and to the presence of halide ion in the coordination sphere of the metal reducing the electronic shift in the NCS group. Both ligands show many infrared bands in the region below 400 om-l. Some new infrared bands, observed in the spectra of the complexes and due to the complexation, are reported in Tables 3 and 4. At least two Y(MS) bands (Table 3) may be identified for the complexes of the three metals, regardless of their stoichiometry. Their attribution may be considered safe, as they are sufficiently constant for each metal. They are independent of the Table 3. Far infrared bands (cm-‘) attributable to v(MS) modes and ring deformation L = MelD
MLCI,
MLBr,
MLCI,
NLBr,
344 mw 266 m8 179 “S
337 vsb 293 vsb 186 Ins
330 VW 274 “8 208 vs
306-283vsb 243 s
ML,(CIO,)~
ring
332 vab 292 vsb 187 B
332 mb 266 s 187 sb 336 mbP 316 wb 262 m8
312 wb
v(MS)
292 vsb 260 vsb
320 mb 267 mb
ring
146 sb
160 sh
164 vsb
166 vsb
v(MW As
Sb
ML&l,
Bi
MLI,
ML,Br,
330 sb?
326 sbl
v(MS)
248 VB 224 m
246 B 228 sh
ring
122 mb
129 vsb
L = EtaD
JfLI,
29P288 mb 288-280 wb 249 m 246 m
160 s 140 ms
167 vsb
164 vsb
260 s 231 s
266 ma 228 wb
246 m 230 w
127 sb
136 vs
121 V8
367 ml 336 VW? 286 wf 263 228 164 121
s VW vsb VW
1726
ANTONIO C. FABRIKCTI and GIAN CARLOPELLACANI
GIORUIO PEYRONEL,
Table 4. Far infrared bands (cm-l) attributable to v(MX) modes L = MQD v(AsX)
v(SbX)
MLCI,
MLBr,
374 vs 320 vsb
246 vs 224 VW
369 vs 337 vsb
167 m
128 ma
174m
340 vs 292 vsb
230 vs? 202 vs 180 s
ML&l,
MLIs
L = Et,D
164 vsb 130 sh
MLI,
249 vs
227 vs 126 ms
336 vs 209 vs 305-283 vsb 183 s
164 vsb 136 vs
MLasr2
308 sb? v(BiX)
MLBr,
MLCl,
178 vsb
277 vs 211 s 174 vs
166 s
176s 162 s 136 vs
137 s 121 vs 88 w
halide ion coordinated to the metal and correspond very well to the values observed for the perchlorate complexes. The higher and lower frequencies may be assigned to a Y(MS) asymmetric and Y(MS) symmetric mode, respectively. They are mass sensitive as is shown in Fig. 1. The literature has very few data regarding the v(MS) frequencies of these metals in complexes comparable to those here described. A *(BiS) asym. frequency of 271 (vs) cm-l is reported, for instance, for the Bi(II1) tris-W-diethyldithiophosphate (dtp) [2]. This value is greater than those observed at about 260 cm-l for these complexes because the dtp-complex is an “inner” oomplex with a four-membered ring. A third band is observed at 208-179, 166-146 and 127-121 cm-l for the three series of complexes (Table 3) both in the perohlorates and in the halides. For the rinq drf.
,
9(M_S)
,
_/
Sb
Bi
-
/
I
100
200
I 300
cc
Fig. 1. Correlationbetween the v(W) and ring deformation bands of the MeaD and EtaD complexes of As(III), Sb(III), Bi(III). [2] D. M. ADUS and J. B. CORNELI,J. Chem. 5’00. (A), 1299 (1968).
An
i.r. spectralstudy on the complexes of amenio (III), antimony (III) and bismuth (III)
1727
same metal the frequency of this band is independent of tbe ligand and of the coordinated halide ion. This band is also mass-sensitive, as are the Y(MS) bands (Fig. l), and must involve the metal atom. It may therefore be attributed to some -\ M common to all the complexes and is vibrational frequency of the ring 1 C--S7 indicated as “ring deformation”. The new band at 336-326 om-l observed for the Me,D-complexes SbMe,DBr, (mb), Bi(MedD)2XB(X = Cl, Br) (sb) and Bi(Me,D),(ClO& (VW)oannot be attributed to Y(MS) modes, for it is not mass-sensitive and too high for a v(BiS) frequency; nor can it be attributed to y(iUX) modes, particularly in the case of Bi(MelD),XI, which is strong, because it is independent of the halogen and too high for a v(BiX) mode. It could therefore be admitted that this band is a ligand-band activated by complexation depending on the conditions of coordination, which should be most favourable in the case of the Bi(Me&D),X, complexes. For the Bi(Me,D),(ClO,), complex, the new band at 367 (m) cm-l is higher than the Y(AsS) value and cannot be attributed to v(BiS) modes; only the new band at 286 (w)cm-’ could be attributed to v(BiS) modes in view of the multiplicity of the Bi-S bonds in this complex. All the A&X, complexes show three new bands which can be attributed to v(AsX) modes; they regularly decrease from the chloride- to the bromide-derivatives (Table 4) with very close values in the MelD- and Et,D-complexes. Very few arsenio trihalide complexes with a stoichiometry similar to the present oomplexes were studied from a structural point of view. An X-ray structural determination has shown that the complex AsCl, 0bipyridil consists of dimerio moleoules with bridging halogen atoms and no stereochemically active lone pair [3, 41. In the far infrared spectra of the complexes AsX&[X = Cl, Br; L = 2,2’-bipyridil (bipy), IJO-phenanthroline (phen) and o-phenylene-bisdimethylamine (diamine)], the following bands were attributed [3] to arsenic-halogen stretching modes:
x = AsX,*bipy AsX,-phen AsX,&anine
r-31 [31 [3]
Cl
314 s 367 8 365 a
X = Br 285 s 265 zs
but because of the Iow symmetry of the complexes, no firm stereoohemical conclusions were drawn. These v(AsX) values agree well with the frequency of the first v&X) band of the present complexes (Table 4). In the case of the complex anions AsX, Y- (X = Cl or Br ; Y = Cl or Br), the following assignments were x Y I/ made [6] on the basis of a C, symmetry of the structure z---As PX [3] M. J. DEVENEY md M. WEBSTER,J. C&m. Sot. (A), 1843 (1970). [4] J. U. CAMERONand R. C. G. KILLEAN, CT@ Stmet. Cowmun. 1,31 (1972). [6] CL Y. AELIJAH and M. GOLDSTEIN,J,. Chern. Sot. (A), 2590 (1970).
1728
GIOEUIO PEYRONBL, ANTONIO C. FABRETTI and GIANC-0
PELLA~ANI
AsC&,Br-[S-j AsBr,Cl- [S] vswaz&a %,(~X),, VWX) VWY)
378mw 297mah 320vs 266mw
247ah? 236vs, 222sh 208 w ,326mb
Also in this case there is a good correspondence between some of the values listed above and the first two frequencies observed for the present complexes (Table 4). The third band observed for the tetrasubstituted dithiooxamides complexes at 167-174 cm-l for the trichloride and 128-126 for the tribromide may well correspond to some d(MX) modes, but it is probably safer to hypothesize that, since the stoichiometry of the complexes is very similar to the complex A&&-bipy [3, 41, these bands may correspond to Y&X) bridging mode, and that these complexes may have a dimeric halogen-bridged structure of the type
with no stereochemically active lone-pair, and a deformed octahedral coordination. If such a structure is true the following assignment of the three bands could be made : I band = ~,(Asx),, II band = r,,(AsX),, III band = Y(AsX) bridging. The SbX,-complexes show (Table 4) two Y(SbX) bands which have close values for the corresponding Me,D- and E&D-complexes. The Sb(Me,D)Br, complex shows a third band at 230 cm-l which may be attributed to a v(SbBr) mode. These bands are mass-sensitive (Table 4). The frequencies of these bands are in good agreement with those observed for the following SbX,& and SbX&L complexes [X = Cl, Br ; L = y-butyrolactam (BuL), dimethylsulfoxide (DMSO) ; L-L = benzothiazole (BT), S-amino-benzothiazole (ABT), benzimidazole-2-thiol (BIT), benzothiazole-2-thiol (BTT)] SbX,(BuL), [6] SbX,(DMSO), [7] SbX,.BT [S] SbX,.ART [8] SbX,*BIT [8] SbX,*BTT [8] (R) = Reman
x -cc1 330mw, 309mw 300 sb, ~250 s 313 s, 293 s 304s 329s 320s
X = Br 234ms(R), 205 vs(R), 155 s
210 s 212m 213s 212 m
The SbX,(BuL)s [0] and SbX,(DMSO), [7] complexes were interpreted as having a distorted square pyramidal coordination with a stereochemically active electron pair occupying a sixth position, like those established by X-ray analysis for SbC1,2and SbCl,(Ph,AsO), 171. The i.r. band observed [9] for SbCl,(Ph,PO) (272s, 257s cm-l [6] S. T. YUANend S. K. MADAN, Inorg. Chim. Aota 3, 463 (1972). [7] R. P. OERTE~,Spctroohim. Acta 26A, 659 (1970). [S] A. OUCHI, T. TAKEUCEIand I. TAXIKAGA,BUZZ.Chin. Soo. Japan 48,284O (1970). [9] S. MILIOEV and D. HAD&,1morg.iVzcol. Cti. Lett. 7, 746 (1971).
An i.r. spectralstudyon the complexesof arae& (III), eutimony (III) and bismuth(III)
1729
and SbCl,(Ph&O), (224s, 209s cm-l) are rather low for the antimony-chlorine stretching but they can be accepted in view of the strong bonding between antimony and the ligand, especially PhJsO. For the SbX,-complexes of BT, ABT, BIT, BTT [S] no deilnite structures were proposed. It is likely that the Me,D- and Et,D-complexes of SbXI also have a distorted square pyramidal coordination with the lone pair stereochemically active in a sixth position
In the case of the SbMe,DBr, complex, the three bands could be due to v(SbBr),,,,, v(SbBr),, and Y(SbBr), modes. The possibility of a dimerid halogen-bridged structure has to be excluded owing to the high value of the third band (180 cm-l) the frequency of which is even higher than the y(AsCl) bridging frequency of the complex AsMe,DCl,. In the case of the SbCl,- and SbI,-complexes too, a third band may be masked under the very strong, broad bands indicated in Table 4. The bismuth trihalide complexes correspond to two different stoichiometries: B&X, for L = MerD and BiLX, for L = Et*D. Both types of complexes have a very low conductivity (Table 1)in nitrobenzene solution. This could mean that in the first type of complex either the metal has a seven-coordination [si(S,)&,] or that one ligand molecule is monocoordinated pi(S,, S)X,] or not coordinated [Bi(S,)Cl,]L or that one halide ion is not coordinated in the solid [si(S,)&]X. In this last case, a displacement reaction should occur in solution: [si(S,),X,]+ + X- + [Bi(S,)X,] + L. It is rather d8icult to chose between these different possibilities simply on the basis of the far infrared spectra. In the case of the Bi(Me,D),X, complexes, the far i.r. spectra reveal a strong broad band at 330326 cm-l which seems to be a new activated band of- the ligand, a strong broad band at 308 cm-l, which may correspond to the very strong ligand band at 310 cm-l and in the case of the BiCl,-complex could mask a Y(BiCl) band. For both complexes only one band can be surely considered to be due to a v(BiX) mode. No stereochemical models may be proposed for these complexes. The BiEt,DX, (X = Cl, Br, I) complexes show three mass sensitive bands attributable to v(BiX) modes (Table 4). The band frequencies observed for the trichloride lie in the range of those given for other BiCl,,L, (z = 1, 2, 2.6) complexes (L = y-butyrolactam, dimethylsulfoxide, Ph,PO and Ph,AsO) v(BiX) BiC&(BuL),., BiCl,(Ph,PO) BiCl,(Ph&sO), BiCl,(DMSO), BiBr,(DMSO), (R) = Raman
[6] [Q] [Q] [7] [7]
286 273 289 271 176
ms, 210 vs(R), 196 sh(R) m, 235 s mw m, -250 s(l) vs(R), 160 s, 148 m(R)
1730
Groacno PE~NEL,
ANTONIOC. FABRETTIand GIAN CARLOPELLAUNI
The BuL-complex was considered [6] as a dimer with one BuL acting as a bridging group connecting two BiCl,(Bti),., units in a pseudo-octahedral symmetry. Largely because of the Raman evidence it was assumed that the trans symmetry for the Bi-Cl bonds is the more likely. For the BiCI,(Ph,PO) complex a trigonal bipyramidal arrangement with three chllrine atoms in the equatorial and the ligand and the lone electron pair in the axial position (0, symmetry) was proposed [9]. For the BiCl,(Ph,AsO), complex a polymer octahedral structure was assumed [9] with a trans position of the ligands in the equatorial plane, the octahedra being linked by the axial chlorine atoms. The BiX,(DMSO), complexes were considered [7] isomorphous with the SbBr,[DMSO)B complexes, and their most probable structure was assumed [7] to be based on an octahedron with trans DMSO groups and one position occupied by a non-bonding electron pair. Unfortunately, their far infrared spectra were cut at 250 cm-l and only their Raman spectra are available at lower frequencies. In the BiEt,DX, (X = Cl, Br, I) complexes, the chelating ligand gives in a monomeric structure two cis M-S bonds in agreement with the two Y(MS) observed bands. No model among those cited above could therefore completely interpret their structure. It may reasonably be assumed that the first two r(BiX) bands correspond to the asymmetric and symmetric stretching vibration of two cis BiX bonds in the same plane of the two cis BiS bonds. The third v(BiX) frequency seems to be too high for v(BiX) bridging bonds in view of the Y(AsX) bridging frequencies observed for the same type of As(III)-complexes. It is therefore likely that the third v(BiX) band corresponds to an axial r(BiX) stretching vibration in agreement with a pseudo-octahedral coordination
in which the sixth position is occupied by a lone electron pair. Aokmwledgemenkis Ricerche of Italy.
work received the financial support of the Consiglio Naziomle de&