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Formation and molecular structure of some molybdenum sulphur complexes
Journal
of the Less-Common
@ Elsevier Sequoia
Metals,
S.A., Lausanne
54 (1977)
- Printed
91 - 99 in the Netherlands
FORMATION AND MOLECULAR STRUCTURE MOLYBDENUM SULPHUR COMPLEXES*
J. DIRAND-COLIN, lnstitut
M. SCHAPPACHER,
Le Bel, Laboratoire
UniuersitJ
Louis Pasteur,
L. RICARD
de Cristallochimie 67070
Strasbourg-Cbdex
91
OF SOME
and R. WEISS
et de Chimie
Structurale
associe’au
CNRS,
(France)
Summary The reaction of dioxomolybdenum( VI) dithiocarbamate (I) with HsS and oxygen was recently shown to yield a novel disulphur complex MoO(Sa)(SaCNPra), (II). Other products of the reaction are sulphur-bridged molybdenum complexes of the type Mo~O~_,S,(~-S~)(S~CNP~~)~. Similarly, (I) reacts with P&e to give essentially the same products and the new asymmetrically bridged complex MoOs(p-O)(p-S)(S,CNPra)a. The yield of (II) is low and other paths to it are being sought. One promising way seemed to be the reaction of Mo(CO)a(S&!NEta)a with S, followed by atmospheric oxidation of the products. Small amounts of (II) are indeed formed. Moreover, small quantities of a green product [Mo(S,O)(SsCNEt,)a] a are isolated. This compound is the first S,O complex to be isolated from the direct reaction of dioxygen with a sulphur species. The unoxidised starting product is tentatively assigned the formula [Mo(S,)dtc,], by analogy with known compounds.
Introduction In contrast to oxomolybdenum complexes, for which a large variety of species with various organic ligands are known [ 11, relatively little is known regarding the formation of analogous sulphur-containing species. Indeed, sulphur yields mainly di-p-sulphido complexes and the only report concerning the formation of terminal sulphur compounds also involves molybdenum(V) complexes of the type MoaOa_,S, (p-S),L,. Diy-sulphido complexes Mo,OaS,La can be obtained from the analogous di-~-0x0 species [2], or alternatively from Mo,0aL4 compounds [3], by reaction with Has. The reaction of MOO,, CS, and amine is said to yield both the former complexes and the unsymmetrical compound MoOS(p-S),dtca [4] from which Mo,S,(p-S),dtc, compounds are obtained by reaction with P4S1,,. In contrast, the reaction of the molybdenum(V1) species MoOa(S,CNR,)s with HaS in *Presented at the Conference on “The Chemistry and Uses of Molybdenum”, University of Oxford, England, 31 August - 3 September, 1976, sponsored by Climax Molybdenum Co. Ltd. and the Chemical Society (Dalton Division).
92 TABLE
1
IR spectra
of reaction
Compounda
products
from MoO~~S~CNPr~)~
IR spectrum WoW
MoO(S2K2
(110
Mo2S4L2 (III) Mo20S,L2 (IV) MozOzS2L2
Wt
aL = S2CNPr,. bPeak positions
and H2S
( cm-l)b WOW
v(MoSb)
535 - 545 530
480 460 470
917
558
940 950 - 970
and assignments
v( S-S)
(v, vibration;
subscript
t, terminal,
and b, bridging
0 or S).
benzene-ethanol mixtures is claimed to yield Mo202(&J)aL2 (R = Bu) and intractable products (R = Pr”) [ 51. The present work was undertaken to obtain a better understanding of some aspects of molybdenum sulphur chemistry and, hopefully, to find new routes to compounds containing terminal molybdenum-sulphur bonds.
Experimental All reactions were conducted at room temperature to avoid possible thermal decomposition of the dithio~b~ato l&and. Solvents were reagent grade and were used as such or dried and degassed by distillation under argon when required. Mo02(S2CNPr2)2, Mo~O~(S~CNP~~)~, MoO(S,CNPr2)2 and Mo(CO),(S,CNEta)s were prepared according to published procedures [5, 61. The latter was dissolved in CHzClz and filtered over Celite to remove NaCl. Reaction of MoU~(S~CNP~~)~ with H2S The dithiocarbamato complex (4g) was dissolved in acetone or CH2C12 and H2S was bubbled through the solution for 1 h. The initially orange solution rapidly became red and, upon standing for two weeks under air, yellowish brown. A preliminary purification of most di-p-bridged complexes can be accomplished by precipitating with E&O. Further purification of the separate fractions is effected by chromatography on silica gel. The blue compound is eluted with 1: 1 toluene-pentane. The di-p-sulphido complexes are separated with mixtures of CH,Cl, and pentane. (II) is diamagnetic (NMR). The four products obtained are listed in Table 1. Reaction of Mo02(S2CNPr2)2 and P,Slo Equimolar amounts (1S:lMo) were reacted as above. In addition to the products obtained with H2S, good yields of Mo,O~S(S~CNP~~)~ were obtained by elution with CH,Cl,-pentane.
93
TABLE
2
Crystal data Compounda
(11)
WI)
(VII)
a@) W) c(A) a(“) Ix”) Y(O) Space group V(“) z
12.033(3) 11.813(3) 19.924(4)
14.142(4) 10.153(3) 8.847(3) 90.58(2) 97.93(2) 108.95(2) Triclinic 5 1187.9 2 624
19.202(4) 11.307(2) 18.609(4)
M
125.04(2) Monoclinic P21/c 2318.8 4 528
aM~Wd(WN~d~ TABLE
95.78(2) Monoclinic P2+ 4019.8 4 944
(II), Mo202(lr-O)(l.l-S)(S2CNPr2)2 (VI), Wo(SsO)(SaCNEta)sls(VII).
3
Parameters used in data collection and least squares refinement Compounda
(II)
(VI)
(VW
w scan width w scan speed (O min-‘) 28 range (“) Total number of reflections Number of reflections with 0(1)/l > 0.33
0.8 1.0 4 - 60 7318 1511 0.072 0.105 0.08 1.11
1.7 4.0 4 - 40 2414 1249 0.054 0.073 0.08 1.23
0.8 2.0 5 - 55 10037 3480 0.059 0.068 0.06 1.25
R RCd P 191 R fit aFor formulae see Table 2.
Reaction of MoOz(SzCNPr,) and S8 Excess Ss and Mo02(S2CNPr2) yield some (II) when reacted for 3 - 4 d. Prolonged reaction time leads to decomposition into molybdates. MO(V) did not give any identifiable products. Attempted reaction of MoO(S2CNPrz), and Ss under argon gave a bright orange material showing a broad IR absorp tion at 810 cm-‘. This is similar to [MoO(S,CNPr,)s] 2 MosOrs [7]. Some (II) is formed after 3 - 4 d in the presence of 02, using an Mo(IV):S ratio of 1:2. Reaction of Mo(C0)2(S2CNEt2)2 and S, S8 and Mo(C0)2(S2CNEt2) (2S:lMo) were reacted for 30 min in CH2C12. Upon exposure to air, the brownish-yellow solution became greenish. Chromatography of the oxidised solutions is conducted on silica gel. Elution with toluene-pentane gave some yellow product followed closely by the blue product MoO(S,) (S2CNEt2)2. The green product comes last and is eluted with CH2C12. Some traces of a brown unidentified product tend to migrate with the green material. This can be avoided by first adding Et20 to the
94
Fig. 1. Molecular geometry of MoO(S~)(S$NP~~)~
(II).
eluant until the brown product starts to migrate and then using pure CHsCls to effect the remainder of the elution. The green complex was identified as [Mo(SsO)(S,CNEts),] s by X-ray crystallography (see below). It has not yet been possible firmly to identify the unoxidised product or products. Crystal data and structure solutions The crystal structures of three compounds have so far been studied. Compound (II) was crystallised from C,H,-pentane, compound (VI) by evaporation of a CHaCls solution, and compound (VII) from CHsCls-EtsO. Crystals of (VII) contain one CH,Cls molecule of solvation in the asymmetric unit. Crystal data are assembled in Table 2, Intensity data were collected on a Philips P~llOO ~ffractomet~ with MO K, radiation at T = 1. Structure solution and refinement were conducted as previously reported [S] , using anisotropic temperature factors for all atoms. The relevant parameters are listed in Table 3.
Results and discussion Reaction with H,S Previous work in our laboratory had shown that MoO,(S&NPr,)s (I) reacted readily with hydrohalogenic acids (HX) in acetone, CHCls or CH,Cls to yield the novel species MoOXsdtcs [lo]. Despite the ~enco~~ng results obtained by Larson and Moore [5], we decided to reinvestigate the reaction of (I) and H2S in these solvents, since the choice of a solvent may have some bearing on the course of the reaction. Chromatography of the reaction mixture afforded the four products listed in Table 1. Compounds (III) - (V) were readily identified by comparison of their IR spectra with those previously reported; however, no structure could be assigned to product (II). Apart from its remarkable deep blue colour, which first intrigued us, we noticed in its IR spectrum the presence of a weak band at 917 cm-‘, assigned to an MO-O stretch, and a medium strong band at 558 cm-” which was later assigned to an S-S stretch.
95
TABLE
4
Molecular dimensions in MoO(S2)(S&!NPr2)2 Selected
bond
MO-O MooS( 1) MO--S(3) MooS( 4) Bond
angles
O-MO-S(~) 0-MO-S( 2) O-MO-S( 3) O-MO-S(~) c&MO-S( 6) 0-MO-S( 5)
lengths
(II)
(A)
1.667( 13) 2.390( 3) 2.509(4) 2.450( 3) in the environment
99.6(4) 104.2(4) 91.7(4) 102.5(4) 92.4(4) 159.6( 5)
2.010(5) 2.354(5) 2.663(6) 2.522(4)
S(lH(2) MO-S(B) MO-S( 5) MO-S( 6) of the metal
(“)
S(l)-MO-S(~) S( 1 )-MO-S( 6) S( 6)-MO-S( 3) S(3)-MO-S(~) S(4EMo-S(2) S( 1 )-MO-S( 5) S( 2kMo-S( 5)
50.1( 2) 81.2( 2) X7(2) 69.7(2) 76.7( 2) 84.2( 2) 93.6(2)
Fig. 2. Molecular geometry of Mo~O#O)(@)(S&NPr.& (VI). The alkyl chains have been omitted for clarity. Fig. 3. Perspective view of [Mo(S20)(S&NEt2)g]2 (VII). Note the orientation of sulphurbound oxygen with respect to the MogS2 ring.
The structure of this compound was solved by X-ray crystallography and the composition of the product was found to be MoO(S2)(S2CNPrs)s (II) [ll].Its geometry is shown in Fig. 1. The environment of the metal is a deformed pentagonal bipyramid with oxygen at an apex and the S2 group located in the equatorial plane. Important geometrical data are listed in Table 4. The formation of a disulphur moiety in the reaction of H2S with a molybdenum(V1) species is surprising. One previous example is the formation of (n-C5H5)NbC1(S,), obtained by reacting (n-C,H,)NbCl,OH with H,S [ 121. However, no indications of the species involved in its formation are available. In the present instance, reduction to molybdenum(V) and possibly molybdenum(IV) is indicated by the observed colour changes. The initially orange solutions quickly become purple and, on standing for a few hours, they acquire a reddish tint. Reduction to molybdenum(IV) is indeed possible
5
of some
di-p-bridged
1.678(2) 1.663(20) 1.71( 3) 1.657(6)
18
19 2
20
21
MogWSgCNJW2
Mo204{SCH2CH(NHg)C0gMe}g
MogWg~SG’(CEt)&
Mo~S~(S~CNBLI;)~
S2CNPr;)2
aNumbers
in parentheses
Mo#UWNB&)2
MogC&%CNEt2)2
Mo20BS(
are maximum
1)
deviations
112.8(9)
110.6(
Ot-M-O,,
from
Avemge angles (“) around the metal in dithiocarbamato
Mog02Sg(SCHgCH(NHg)COgMe)z
1.665(l)
Moot
17
Mo203S(S2CNPr;)g
Ref.
complexes
Bond lengths (A) and bridge angles (“)
Comparison
TABLE
the mean.
109.7(5)
Ot-MO-S,,
complexesa
1.930(18)
1.940(2)
Moob 1.927(11)
2.307(4) 2.801(2)
2.739(
2.804(4)
2.562(3)
2.580(
2.673(3)
MO-MO
108.5(8)
St-MO-S,,
12)
2.29( 2)
2.307(
2.305(5)
MoS,,
1)
1)
106.5(2.0)
106.8(1.5)
106.7(3.0)
Xb-MwSdtc
83.0(7)
83.3( 1)
87.8(4)
MoO,,Mo
74.7( 1)
73.3( 1)
74.8(4)
70.9( 2)
MoShMo
152.9
148.2(3)
148.0( 5)
Basal planes
101.8(2)
103.8(l)
101.8(5)
91.5(7)
91.9( 1)
97.0(l)
X,,-MO-X,,
x
97
TABLE 6 Molecular dimensions in [Mo( S~O)(S~CNEt~)~] 2 (VII) Selected
bond lengths (A)
MO(~)-MO(~) Mo( 1)-S( 1) MO(~)-S( 2) MO(~)-S(4) S(lW(2) S(lW(1) MO(~)-S(9) MO(~)-S(lO) MO(~)-S(ll) MO(~)-S(12)
2.757( 1) 2.468(3) 2.368( 3) 2.391(3) 2.094(5) 1.482(9) 2.485(3) 2.506( 3) 2.549( 3) 2.479( 3)
I~po~~an~ angles in the iVo2(S~0fz S(2kMo(l)-S(4) Mo( 1 )-S( 2)-Mo( 2) S(2~S(l)--O(l) S(l)-MO(~)-S(2) S(2)-S(l)-MO(~) O(l~-S(l~Mo(1)
109.4(2) 70.6( 1) 115.4(4) 51.3(l) 61.9(l) 114.3(4)
Mo( 2)-S( 3) Mo( 2)-S( 2) MO(~)--S(4) Sf3w%41 S(3m2) MO(~)-S(5) MO(~)-S(6) Mo(2kS(7) MO(~)-S(8)
2.476( 3) 2.403(3) 2.363(3) 2.106(4) 1.482(8) 2.535(3) 2.475(3) 2.490( 3) 2.51513)
unit (“) S(2t_Mo(2)-S(4) MO(~)-S(4)-MO(~) S(4)_S(3)-O(2) S(3)-MO(~)-S(4) S(4kS(3Wo(2) O(Z)-S(3 jMo(2)
109.1(2) 70.9( 1) 116.0(4) 51.5( 1) 61.5(l) 114.7(4)
with thiols [ 135. Moreover, the presence of molybdenum(V) in the solutions is indicated by the formation of the di-p-sulphido complexes (III) - (V) [3]. It has been shown that reduction of molybdenum by thiols leads to the formation of ~sulphides R-S-S-R. It is thus tempting to assume that, with Has, some H&S, is formed. This would rapidly be converted to higher sulphanes, along with the formation of Ss [ 141. Any of these may react with the molybdenum species present in the solution to yield (II). The most likely candidate would appear to be Ss. Indeed, molybdenum(IV) is known to give some oxidative addition reactions [ 151, and disulphur complexes of iridium and rhodium were obtained in #is fashion [ 16). Reaction of MoO(S~CNPr~)~ with Ss under argon gave only a poIymolybdate but in the presence of 0s some (II) is obtained. Molybdenum(V) did not give (II) on reaction with Ss. Small amounts of the blue compound were obtained by reacting (I) with an excess of Ss. The reaction of sulphanes with the molybdenum species has not yet been ~ves~gat~. These results show that 0, is required in the formation of (II).
Reaction with P,SIO In an attempt to obtain a better preparation of (II), compound (I) was reacted with P&e. The yields and range of products obtained are essentially the same as in the HsS reaction. The only difference lies in the formation of a product showing strong IR absorption at 978 cm-’ and 960 cm-‘, indicating the presence of two terminal oxygen atoms. Two additional important bands are present at 714 cm-’ and at 524 cm-“. This suggested the formulation MosO&-O)(&S)(SscNm2)2 (VI). This hypothesis was confirmed by X-ray
98
crystal structure analysis [ 171. The geometry of the molecule is shown in Fig. 2, and some of its molecular dimensions are compared with those of previously known complexes in Table 5. The environments of the metal atoms are deformed square pyramids, as is usual with d&M-bridged molybdenum dithiocarbamato complexes. It is interesting to notice that some dimensions (e.g. the MO-MO distance and the angles in the MosOS ring) have values that are the mean of those reported for the symmetrical complexes. Compound (VI) should be formed at an intermediate stage in the formation of di-p-sulphido complexes. This has now been demonstrated [22]. Reactions of MOM (S, CNE t2)2 and Ss Our interest in the formation of (II) led us to seek new routes to it with potentially higher yields. Molybdenum-disulphur complexes are known, e.g. [CpMoS,] s [23], the polymeric Mo(S,)Cls and MO&C& [24]. This suggested the possibility of obtaining (II) by oxidation of a similar molybdenum(IV) dithiocarbamato species. These considerations led us to react Mo(CO)s(SsCNEta)s and Ss. If [Mo(S,)(S,CNEts)a] s was formed in this reaction, one would indeed expect oxidation at MO to give good yields of (II). The results are both disappointing and surprising. The planned reaction occurs smoothly and is complete in about 30 min. After oxidation of the mixture, however, three major products were obtained: one yellow fraction, identified as MosOSs(SsCNEta)s, some blue product (15%) and a green fraction (10%). The crystal structure of the last fraction was studied to establish the identity of the green compound. The result is shown in Fig. 3. Two Mo(S,CNEt,), moieties are bridged by two SaO molecules. The latter are tridentate, with terminal sulphur atoms bridging the molybdenum atoms and the median one linked to only one metal atom. The two oxygen atoms are cis with respect to the MosSa ring. The Mos(SsO), unit has virtual Ca symmetry. Important molecular dimensions are listed in Table 6. The MO-MO distance (2.757( 1) W) is indicative of a single metal-metal bond. In order to reach an l&electron configuration, the complex is best regarded as containing molybdenum( III) and SaO- anions. While this work was in preparation, the formation of an SsO complex by periodate oxidation of IrS,Cl(dppe) was reported [25]. The formation of [Mo(SsO)(SsCNEts)s] s (VII) by direct dioxygen oxidation of a sulphur species is the first such observation. It would be extremely surprising if oxidation took place at a ligand instead of the metal in a low oxidation state molybdenum complex. It is possible that the species present under argon are not as simple as envisaged. Present efforts are directed at finding suitable separation and crystallisation techniques in order to identify the species present prior to oxidation. It is hoped that this identification will aid in understanding the formation of (VII). References 1 P. C. H. Mitchell, Q. Rev. Chem. Sot., 20 (1966) 103. P. C. H. Mitchell, in P. C. H. Mitchell (ed.), 1st Int. Conf. on the Chemistry and Uses
99
2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
of Molybdenum, Climax Molybdenum Co., London, 1974, p. 1, in J. Less-Common Met., 36 (1974) 3. F. A. Cotton, in P. C. H. Mitchell (ed.), 1st Int. Conf. on the Chemistry and Uses of Molybdenum, Clinax Molybdenum Co., London, 19’74, p. 6, in J. Less-Common Met., 36 (1974) 13. B. Spivack and Z. Dori, Coord. Chem. Rev., 17 (1975) 99. M. G. B. Drew and A. Kay, J. Chem. Sot. A, (1971) 1851. W. E. Newton, J. L. Corbin and J. W. McDonald, J. Chem. Sot. Dalton Trans., (1974) 1044. T. Sakurai, H. Okabe and H. Isoyama, Bull. Jpn. Pet. Inst., 13 (1971) 243. F. W. Moore and M. L. Larson, Inorg. Chem., 6 (1967) 998. R. Barral, C. Bocard, I. S&he de Roth and L. Sajus, Tetrahedron Lett., 17 (1972) 1693. R. Colton, G. R. Scollary and I. B. Tomkins, Aust. J. Chem., 21 (1968) 15. L. Ricard and R. Weiss, unpublished results, 1975. L. Ricard, P. Karagiannidis and R. Weiss, Inorg. Chem., 12 (1972) 2179. W. R. Corfield, R. J. Doedens and J. A. Ibers, Inorg. Chem., 6 (1967) 197. J. Dirand, L. Ricard and R. Weiss, J. Chem. Sot. Dalton Trans., (1976) 278. J. Dirand, L. Ricard and R. Weiss, Inorg. Nucl. Chem. Lett., 11 (1975) 661. P. M. Treichel and G. P. Werber, J. Am. Chem. Sot., 90 (1968) 1753. R. N. Jowitt and P. C. H. Mitchell, J. Chem. Sot. A, (1969) 2632. E. Muller and J. B. Hyne, Can. J. Chem., 46 (1968) 2341. P. W. Schneider, D. C. Bravard, J. W. McDonald and W. E. Newton, J. Am. Chem. Sot., 94 (1972) 8640. A. P. Ginsberg and W. E. Lindsell, Chem. Commun., (1971) 232. J. Dirand-Cohn, L. Ricard and R. Weiss, Inorg. Chim. Acta, 18 (1976) L21 - L22. L. Ricard, C. Martin, R. Wiest and R. Weiss, Inorg. Chem., 14 (1975) 2300. M. G. B. Drew and A. Kay, J. Chem. Sot. A, (1971) 1846. R. Weiss and R. Wiest, unpublished results, 1974. B. Spivack, Z. Dori and E. I. Steifel, Inorg. Nucl. Chem. Lett., 11 (1975) 501. W. E. Newton, personal communication, 1976. W. Beck, W. Danzer and G. Thiel, Angew. Chem. Int. Ed., 12 (1973) 582. J. Marco11 and A. Rabenau, Rev. Chim. Miner., 11 (1974) 607. G. Schmid and G. Ritter, Angew. Chem., 87 (1975) 673.
of the Less-Common
@ Elsevier Sequoia
Metals,
S.A., Lausanne
54 (1977)
- Printed
91 - 99 in the Netherlands
FORMATION AND MOLECULAR STRUCTURE MOLYBDENUM SULPHUR COMPLEXES*
J. DIRAND-COLIN, lnstitut
M. SCHAPPACHER,
Le Bel, Laboratoire
UniuersitJ
Louis Pasteur,
L. RICARD
de Cristallochimie 67070
Strasbourg-Cbdex
91
OF SOME
and R. WEISS
et de Chimie
Structurale
associe’au
CNRS,
(France)
Summary The reaction of dioxomolybdenum( VI) dithiocarbamate (I) with HsS and oxygen was recently shown to yield a novel disulphur complex MoO(Sa)(SaCNPra), (II). Other products of the reaction are sulphur-bridged molybdenum complexes of the type Mo~O~_,S,(~-S~)(S~CNP~~)~. Similarly, (I) reacts with P&e to give essentially the same products and the new asymmetrically bridged complex MoOs(p-O)(p-S)(S,CNPra)a. The yield of (II) is low and other paths to it are being sought. One promising way seemed to be the reaction of Mo(CO)a(S&!NEta)a with S, followed by atmospheric oxidation of the products. Small amounts of (II) are indeed formed. Moreover, small quantities of a green product [Mo(S,O)(SsCNEt,)a] a are isolated. This compound is the first S,O complex to be isolated from the direct reaction of dioxygen with a sulphur species. The unoxidised starting product is tentatively assigned the formula [Mo(S,)dtc,], by analogy with known compounds.
Introduction In contrast to oxomolybdenum complexes, for which a large variety of species with various organic ligands are known [ 11, relatively little is known regarding the formation of analogous sulphur-containing species. Indeed, sulphur yields mainly di-p-sulphido complexes and the only report concerning the formation of terminal sulphur compounds also involves molybdenum(V) complexes of the type MoaOa_,S, (p-S),L,. Diy-sulphido complexes Mo,OaS,La can be obtained from the analogous di-~-0x0 species [2], or alternatively from Mo,0aL4 compounds [3], by reaction with Has. The reaction of MOO,, CS, and amine is said to yield both the former complexes and the unsymmetrical compound MoOS(p-S),dtca [4] from which Mo,S,(p-S),dtc, compounds are obtained by reaction with P4S1,,. In contrast, the reaction of the molybdenum(V1) species MoOa(S,CNR,)s with HaS in *Presented at the Conference on “The Chemistry and Uses of Molybdenum”, University of Oxford, England, 31 August - 3 September, 1976, sponsored by Climax Molybdenum Co. Ltd. and the Chemical Society (Dalton Division).
92 TABLE
1
IR spectra
of reaction
Compounda
products
from MoO~~S~CNPr~)~
IR spectrum WoW
MoO(S2K2
(110
Mo2S4L2 (III) Mo20S,L2 (IV) MozOzS2L2
Wt
aL = S2CNPr,. bPeak positions
and H2S
( cm-l)b WOW
v(MoSb)
535 - 545 530
480 460 470
917
558
940 950 - 970
and assignments
v( S-S)
(v, vibration;
subscript
t, terminal,
and b, bridging
0 or S).
benzene-ethanol mixtures is claimed to yield Mo202(&J)aL2 (R = Bu) and intractable products (R = Pr”) [ 51. The present work was undertaken to obtain a better understanding of some aspects of molybdenum sulphur chemistry and, hopefully, to find new routes to compounds containing terminal molybdenum-sulphur bonds.
Experimental All reactions were conducted at room temperature to avoid possible thermal decomposition of the dithio~b~ato l&and. Solvents were reagent grade and were used as such or dried and degassed by distillation under argon when required. Mo02(S2CNPr2)2, Mo~O~(S~CNP~~)~, MoO(S,CNPr2)2 and Mo(CO),(S,CNEta)s were prepared according to published procedures [5, 61. The latter was dissolved in CHzClz and filtered over Celite to remove NaCl. Reaction of MoU~(S~CNP~~)~ with H2S The dithiocarbamato complex (4g) was dissolved in acetone or CH2C12 and H2S was bubbled through the solution for 1 h. The initially orange solution rapidly became red and, upon standing for two weeks under air, yellowish brown. A preliminary purification of most di-p-bridged complexes can be accomplished by precipitating with E&O. Further purification of the separate fractions is effected by chromatography on silica gel. The blue compound is eluted with 1: 1 toluene-pentane. The di-p-sulphido complexes are separated with mixtures of CH,Cl, and pentane. (II) is diamagnetic (NMR). The four products obtained are listed in Table 1. Reaction of Mo02(S2CNPr2)2 and P,Slo Equimolar amounts (1S:lMo) were reacted as above. In addition to the products obtained with H2S, good yields of Mo,O~S(S~CNP~~)~ were obtained by elution with CH,Cl,-pentane.
93
TABLE
2
Crystal data Compounda
(11)
WI)
(VII)
a@) W) c(A) a(“) Ix”) Y(O) Space group V(“) z
12.033(3) 11.813(3) 19.924(4)
14.142(4) 10.153(3) 8.847(3) 90.58(2) 97.93(2) 108.95(2) Triclinic 5 1187.9 2 624
19.202(4) 11.307(2) 18.609(4)
M
125.04(2) Monoclinic P21/c 2318.8 4 528
aM~Wd(WN~d~ TABLE
95.78(2) Monoclinic P2+ 4019.8 4 944
(II), Mo202(lr-O)(l.l-S)(S2CNPr2)2 (VI), Wo(SsO)(SaCNEta)sls(VII).
3
Parameters used in data collection and least squares refinement Compounda
(II)
(VI)
(VW
w scan width w scan speed (O min-‘) 28 range (“) Total number of reflections Number of reflections with 0(1)/l > 0.33
0.8 1.0 4 - 60 7318 1511 0.072 0.105 0.08 1.11
1.7 4.0 4 - 40 2414 1249 0.054 0.073 0.08 1.23
0.8 2.0 5 - 55 10037 3480 0.059 0.068 0.06 1.25
R RCd P 191 R fit aFor formulae see Table 2.
Reaction of MoOz(SzCNPr,) and S8 Excess Ss and Mo02(S2CNPr2) yield some (II) when reacted for 3 - 4 d. Prolonged reaction time leads to decomposition into molybdates. MO(V) did not give any identifiable products. Attempted reaction of MoO(S2CNPrz), and Ss under argon gave a bright orange material showing a broad IR absorp tion at 810 cm-‘. This is similar to [MoO(S,CNPr,)s] 2 MosOrs [7]. Some (II) is formed after 3 - 4 d in the presence of 02, using an Mo(IV):S ratio of 1:2. Reaction of Mo(C0)2(S2CNEt2)2 and S, S8 and Mo(C0)2(S2CNEt2) (2S:lMo) were reacted for 30 min in CH2C12. Upon exposure to air, the brownish-yellow solution became greenish. Chromatography of the oxidised solutions is conducted on silica gel. Elution with toluene-pentane gave some yellow product followed closely by the blue product MoO(S,) (S2CNEt2)2. The green product comes last and is eluted with CH2C12. Some traces of a brown unidentified product tend to migrate with the green material. This can be avoided by first adding Et20 to the
94
Fig. 1. Molecular geometry of MoO(S~)(S$NP~~)~
(II).
eluant until the brown product starts to migrate and then using pure CHsCls to effect the remainder of the elution. The green complex was identified as [Mo(SsO)(S,CNEts),] s by X-ray crystallography (see below). It has not yet been possible firmly to identify the unoxidised product or products. Crystal data and structure solutions The crystal structures of three compounds have so far been studied. Compound (II) was crystallised from C,H,-pentane, compound (VI) by evaporation of a CHaCls solution, and compound (VII) from CHsCls-EtsO. Crystals of (VII) contain one CH,Cls molecule of solvation in the asymmetric unit. Crystal data are assembled in Table 2, Intensity data were collected on a Philips P~llOO ~ffractomet~ with MO K, radiation at T = 1. Structure solution and refinement were conducted as previously reported [S] , using anisotropic temperature factors for all atoms. The relevant parameters are listed in Table 3.
Results and discussion Reaction with H,S Previous work in our laboratory had shown that MoO,(S&NPr,)s (I) reacted readily with hydrohalogenic acids (HX) in acetone, CHCls or CH,Cls to yield the novel species MoOXsdtcs [lo]. Despite the ~enco~~ng results obtained by Larson and Moore [5], we decided to reinvestigate the reaction of (I) and H2S in these solvents, since the choice of a solvent may have some bearing on the course of the reaction. Chromatography of the reaction mixture afforded the four products listed in Table 1. Compounds (III) - (V) were readily identified by comparison of their IR spectra with those previously reported; however, no structure could be assigned to product (II). Apart from its remarkable deep blue colour, which first intrigued us, we noticed in its IR spectrum the presence of a weak band at 917 cm-‘, assigned to an MO-O stretch, and a medium strong band at 558 cm-” which was later assigned to an S-S stretch.
95
TABLE
4
Molecular dimensions in MoO(S2)(S&!NPr2)2 Selected
bond
MO-O MooS( 1) MO--S(3) MooS( 4) Bond
angles
O-MO-S(~) 0-MO-S( 2) O-MO-S( 3) O-MO-S(~) c&MO-S( 6) 0-MO-S( 5)
lengths
(II)
(A)
1.667( 13) 2.390( 3) 2.509(4) 2.450( 3) in the environment
99.6(4) 104.2(4) 91.7(4) 102.5(4) 92.4(4) 159.6( 5)
2.010(5) 2.354(5) 2.663(6) 2.522(4)
S(lH(2) MO-S(B) MO-S( 5) MO-S( 6) of the metal
(“)
S(l)-MO-S(~) S( 1 )-MO-S( 6) S( 6)-MO-S( 3) S(3)-MO-S(~) S(4EMo-S(2) S( 1 )-MO-S( 5) S( 2kMo-S( 5)
50.1( 2) 81.2( 2) X7(2) 69.7(2) 76.7( 2) 84.2( 2) 93.6(2)
Fig. 2. Molecular geometry of Mo~O#O)(@)(S&NPr.& (VI). The alkyl chains have been omitted for clarity. Fig. 3. Perspective view of [Mo(S20)(S&NEt2)g]2 (VII). Note the orientation of sulphurbound oxygen with respect to the MogS2 ring.
The structure of this compound was solved by X-ray crystallography and the composition of the product was found to be MoO(S2)(S2CNPrs)s (II) [ll].Its geometry is shown in Fig. 1. The environment of the metal is a deformed pentagonal bipyramid with oxygen at an apex and the S2 group located in the equatorial plane. Important geometrical data are listed in Table 4. The formation of a disulphur moiety in the reaction of H2S with a molybdenum(V1) species is surprising. One previous example is the formation of (n-C5H5)NbC1(S,), obtained by reacting (n-C,H,)NbCl,OH with H,S [ 121. However, no indications of the species involved in its formation are available. In the present instance, reduction to molybdenum(V) and possibly molybdenum(IV) is indicated by the observed colour changes. The initially orange solutions quickly become purple and, on standing for a few hours, they acquire a reddish tint. Reduction to molybdenum(IV) is indeed possible
5
of some
di-p-bridged
1.678(2) 1.663(20) 1.71( 3) 1.657(6)
18
19 2
20
21
MogWSgCNJW2
Mo204{SCH2CH(NHg)C0gMe}g
MogWg~SG’(CEt)&
Mo~S~(S~CNBLI;)~
S2CNPr;)2
aNumbers
in parentheses
Mo#UWNB&)2
MogC&%CNEt2)2
Mo20BS(
are maximum
1)
deviations
112.8(9)
110.6(
Ot-M-O,,
from
Avemge angles (“) around the metal in dithiocarbamato
Mog02Sg(SCHgCH(NHg)COgMe)z
1.665(l)
Moot
17
Mo203S(S2CNPr;)g
Ref.
complexes
Bond lengths (A) and bridge angles (“)
Comparison
TABLE
the mean.
109.7(5)
Ot-MO-S,,
complexesa
1.930(18)
1.940(2)
Moob 1.927(11)
2.307(4) 2.801(2)
2.739(
2.804(4)
2.562(3)
2.580(
2.673(3)
MO-MO
108.5(8)
St-MO-S,,
12)
2.29( 2)
2.307(
2.305(5)
MoS,,
1)
1)
106.5(2.0)
106.8(1.5)
106.7(3.0)
Xb-MwSdtc
83.0(7)
83.3( 1)
87.8(4)
MoO,,Mo
74.7( 1)
73.3( 1)
74.8(4)
70.9( 2)
MoShMo
152.9
148.2(3)
148.0( 5)
Basal planes
101.8(2)
103.8(l)
101.8(5)
91.5(7)
91.9( 1)
97.0(l)
X,,-MO-X,,
x
97
TABLE 6 Molecular dimensions in [Mo( S~O)(S~CNEt~)~] 2 (VII) Selected
bond lengths (A)
MO(~)-MO(~) Mo( 1)-S( 1) MO(~)-S( 2) MO(~)-S(4) S(lW(2) S(lW(1) MO(~)-S(9) MO(~)-S(lO) MO(~)-S(ll) MO(~)-S(12)
2.757( 1) 2.468(3) 2.368( 3) 2.391(3) 2.094(5) 1.482(9) 2.485(3) 2.506( 3) 2.549( 3) 2.479( 3)
I~po~~an~ angles in the iVo2(S~0fz S(2kMo(l)-S(4) Mo( 1 )-S( 2)-Mo( 2) S(2~S(l)--O(l) S(l)-MO(~)-S(2) S(2)-S(l)-MO(~) O(l~-S(l~Mo(1)
109.4(2) 70.6( 1) 115.4(4) 51.3(l) 61.9(l) 114.3(4)
Mo( 2)-S( 3) Mo( 2)-S( 2) MO(~)--S(4) Sf3w%41 S(3m2) MO(~)-S(5) MO(~)-S(6) Mo(2kS(7) MO(~)-S(8)
2.476( 3) 2.403(3) 2.363(3) 2.106(4) 1.482(8) 2.535(3) 2.475(3) 2.490( 3) 2.51513)
unit (“) S(2t_Mo(2)-S(4) MO(~)-S(4)-MO(~) S(4)_S(3)-O(2) S(3)-MO(~)-S(4) S(4kS(3Wo(2) O(Z)-S(3 jMo(2)
109.1(2) 70.9( 1) 116.0(4) 51.5( 1) 61.5(l) 114.7(4)
with thiols [ 135. Moreover, the presence of molybdenum(V) in the solutions is indicated by the formation of the di-p-sulphido complexes (III) - (V) [3]. It has been shown that reduction of molybdenum by thiols leads to the formation of ~sulphides R-S-S-R. It is thus tempting to assume that, with Has, some H&S, is formed. This would rapidly be converted to higher sulphanes, along with the formation of Ss [ 141. Any of these may react with the molybdenum species present in the solution to yield (II). The most likely candidate would appear to be Ss. Indeed, molybdenum(IV) is known to give some oxidative addition reactions [ 151, and disulphur complexes of iridium and rhodium were obtained in #is fashion [ 16). Reaction of MoO(S~CNPr~)~ with Ss under argon gave only a poIymolybdate but in the presence of 0s some (II) is obtained. Molybdenum(V) did not give (II) on reaction with Ss. Small amounts of the blue compound were obtained by reacting (I) with an excess of Ss. The reaction of sulphanes with the molybdenum species has not yet been ~ves~gat~. These results show that 0, is required in the formation of (II).
Reaction with P,SIO In an attempt to obtain a better preparation of (II), compound (I) was reacted with P&e. The yields and range of products obtained are essentially the same as in the HsS reaction. The only difference lies in the formation of a product showing strong IR absorption at 978 cm-’ and 960 cm-‘, indicating the presence of two terminal oxygen atoms. Two additional important bands are present at 714 cm-’ and at 524 cm-“. This suggested the formulation MosO&-O)(&S)(SscNm2)2 (VI). This hypothesis was confirmed by X-ray
98
crystal structure analysis [ 171. The geometry of the molecule is shown in Fig. 2, and some of its molecular dimensions are compared with those of previously known complexes in Table 5. The environments of the metal atoms are deformed square pyramids, as is usual with d&M-bridged molybdenum dithiocarbamato complexes. It is interesting to notice that some dimensions (e.g. the MO-MO distance and the angles in the MosOS ring) have values that are the mean of those reported for the symmetrical complexes. Compound (VI) should be formed at an intermediate stage in the formation of di-p-sulphido complexes. This has now been demonstrated [22]. Reactions of MOM (S, CNE t2)2 and Ss Our interest in the formation of (II) led us to seek new routes to it with potentially higher yields. Molybdenum-disulphur complexes are known, e.g. [CpMoS,] s [23], the polymeric Mo(S,)Cls and MO&C& [24]. This suggested the possibility of obtaining (II) by oxidation of a similar molybdenum(IV) dithiocarbamato species. These considerations led us to react Mo(CO)s(SsCNEta)s and Ss. If [Mo(S,)(S,CNEts)a] s was formed in this reaction, one would indeed expect oxidation at MO to give good yields of (II). The results are both disappointing and surprising. The planned reaction occurs smoothly and is complete in about 30 min. After oxidation of the mixture, however, three major products were obtained: one yellow fraction, identified as MosOSs(SsCNEta)s, some blue product (15%) and a green fraction (10%). The crystal structure of the last fraction was studied to establish the identity of the green compound. The result is shown in Fig. 3. Two Mo(S,CNEt,), moieties are bridged by two SaO molecules. The latter are tridentate, with terminal sulphur atoms bridging the molybdenum atoms and the median one linked to only one metal atom. The two oxygen atoms are cis with respect to the MosSa ring. The Mos(SsO), unit has virtual Ca symmetry. Important molecular dimensions are listed in Table 6. The MO-MO distance (2.757( 1) W) is indicative of a single metal-metal bond. In order to reach an l&electron configuration, the complex is best regarded as containing molybdenum( III) and SaO- anions. While this work was in preparation, the formation of an SsO complex by periodate oxidation of IrS,Cl(dppe) was reported [25]. The formation of [Mo(SsO)(SsCNEts)s] s (VII) by direct dioxygen oxidation of a sulphur species is the first such observation. It would be extremely surprising if oxidation took place at a ligand instead of the metal in a low oxidation state molybdenum complex. It is possible that the species present under argon are not as simple as envisaged. Present efforts are directed at finding suitable separation and crystallisation techniques in order to identify the species present prior to oxidation. It is hoped that this identification will aid in understanding the formation of (VII). References 1 P. C. H. Mitchell, Q. Rev. Chem. Sot., 20 (1966) 103. P. C. H. Mitchell, in P. C. H. Mitchell (ed.), 1st Int. Conf. on the Chemistry and Uses
99
2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
of Molybdenum, Climax Molybdenum Co., London, 1974, p. 1, in J. Less-Common Met., 36 (1974) 3. F. A. Cotton, in P. C. H. Mitchell (ed.), 1st Int. Conf. on the Chemistry and Uses of Molybdenum, Clinax Molybdenum Co., London, 19’74, p. 6, in J. Less-Common Met., 36 (1974) 13. B. Spivack and Z. Dori, Coord. Chem. Rev., 17 (1975) 99. M. G. B. Drew and A. Kay, J. Chem. Sot. A, (1971) 1851. W. E. Newton, J. L. Corbin and J. W. McDonald, J. Chem. Sot. Dalton Trans., (1974) 1044. T. Sakurai, H. Okabe and H. Isoyama, Bull. Jpn. Pet. Inst., 13 (1971) 243. F. W. Moore and M. L. Larson, Inorg. Chem., 6 (1967) 998. R. Barral, C. Bocard, I. S&he de Roth and L. Sajus, Tetrahedron Lett., 17 (1972) 1693. R. Colton, G. R. Scollary and I. B. Tomkins, Aust. J. Chem., 21 (1968) 15. L. Ricard and R. Weiss, unpublished results, 1975. L. Ricard, P. Karagiannidis and R. Weiss, Inorg. Chem., 12 (1972) 2179. W. R. Corfield, R. J. Doedens and J. A. Ibers, Inorg. Chem., 6 (1967) 197. J. Dirand, L. Ricard and R. Weiss, J. Chem. Sot. Dalton Trans., (1976) 278. J. Dirand, L. Ricard and R. Weiss, Inorg. Nucl. Chem. Lett., 11 (1975) 661. P. M. Treichel and G. P. Werber, J. Am. Chem. Sot., 90 (1968) 1753. R. N. Jowitt and P. C. H. Mitchell, J. Chem. Sot. A, (1969) 2632. E. Muller and J. B. Hyne, Can. J. Chem., 46 (1968) 2341. P. W. Schneider, D. C. Bravard, J. W. McDonald and W. E. Newton, J. Am. Chem. Sot., 94 (1972) 8640. A. P. Ginsberg and W. E. Lindsell, Chem. Commun., (1971) 232. J. Dirand-Cohn, L. Ricard and R. Weiss, Inorg. Chim. Acta, 18 (1976) L21 - L22. L. Ricard, C. Martin, R. Wiest and R. Weiss, Inorg. Chem., 14 (1975) 2300. M. G. B. Drew and A. Kay, J. Chem. Sot. A, (1971) 1846. R. Weiss and R. Wiest, unpublished results, 1974. B. Spivack, Z. Dori and E. I. Steifel, Inorg. Nucl. Chem. Lett., 11 (1975) 501. W. E. Newton, personal communication, 1976. W. Beck, W. Danzer and G. Thiel, Angew. Chem. Int. Ed., 12 (1973) 582. J. Marco11 and A. Rabenau, Rev. Chim. Miner., 11 (1974) 607. G. Schmid and G. Ritter, Angew. Chem., 87 (1975) 673.