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Reaction of sodium η-cyclopentadienyldicarbonylferrate(0) with sulfur dioxide. Synthesis of ironsulfur dioxide complexes
57
Journal
if
@ Elkier
Organometallic &hem&&. 145 (1978) 57-68 Sequoia S.A., Lausanne- Printed in The Netherlands
REACTION OF SODIUM +CYCLOPENTADIENYLDICARBONYLFERRATE(O) WITH SULFUR COMPLEXES
DIOXIDE.
SYNTHESIS
OF IRON-SULFUR
DIOXIDE
PGTER REICH-ROHRWIG, ALAN C. CLARK, RAYMOND L. DOWNS- and ANDREW WOJCICKI * The McPherson (U.S.A.)
Chemical
Laboratory,
The Ohio
State
University,
Columbus.
Ohio
43210
(Received August 22nd, 1977)
Sulfur dioxide reacts at -78°C with Na’ [qS-C,H,Fe(C0)2]-, prepared by the reduction of [q5-CsHsFe(CO),], with sodium amalgam in tetrahydrofumn, to g4ve a red solu~on containing a species which can be alkylated with RX to q5-CSH5Fe(CO)2S(0)2R. The alkylation reaction with CH,I affords both $C,H,Fe(CO),S(O),CH, and $-C,H,Fe(CO),I. The nature of this solution and the possible existence of the anion [q5-CSHSFe(CO),SOJ therein are discussed. Upon warming to room temperature and chromatography, the solutions of Na’ [$-CsHsFe(CO),]and SO2 afford the isolable iron-sulfur dioxide complexes, [qS-C,H,Fe(CO),],S0,, [$-C5H,Fe(CO)]z(CO)S02, and I$‘-CSH,Fe(CO),SO,],. The characterization and properties of the first two compounds are described.
Introduction
Sulfur dioxide behaves as a Lewis acid toward a number of low-valent transition metals in complexes. Examples of such interactions are found in Ir[PW$-WJ,~(COKQ 11,213 RhIP(C6H~5)312CI(CO)SO* C1,3], WW,H,),I,(SO,), . C&H8[4], and Pt[P(C6H5)J3S02 * 0.7 SO2 [5]. These complexes contain nonplanar MSOz moieties with a pyramidal configuration about the sulfur, indicative of the presence of a lone pair of valence electrons thereon. Transition metal carbonyl anions undergo reactions with a number of electrophilic reagents, including protic acids, alkyl halides, and various other organic as well as organometallic compounds, especially those containing halogens 163. The anion [$-CsHsFe(CO)J, in particular, has been found to behave as a powerful nucleophile [ 71. The observed high degree of nucleophilicity of
Cr15-C$-&Fe(CO)2r suggested that it would interest readily with SO, to form a l/l adduct, This adduct is expected to exhibit “nonplanar” Fe-SO* bonding, similar in nature to that found for the aforementioned noble metal complexes. The interaction of I$-CSHsFe(CO)Jwith CS2, a weaker electrophile than SO,, to yield [$-CSHSFe(CO)$SZ] was reported very recently [S]. In this paper are described our studies on reaction between Na’ [$-C,H,Fe(CO),] and SO*. As the investigation progressed it became apparent that the reaction in question is quite complex and affords several Fe-SO, products, the nature of which depends on the experimental conditions. Some aspects of this study were communicated earlier [9,10]. Presented herein is a full account. Results and discussion Reaction of Na’ [$4&H5Fe(CO)J with SO2 Gaseous SO, was passed slowly into a tetrahydrofuran solution of an approximately equimolar amount of Na’ [$-CSHjFe(CO)J, prepared by the reduction of [@-C,H;Fe(CO),], with sodium amalgam and cooled to ca. -78°C. The resulting solution v& treated with bis(triphenylphosphine)iminium chloride (PPN’ Cl-) [ll] at -78°C and above in attempts to obtain [PPN]‘[$-CSHjFe(CO)lSO,]. However, none of the additions of PPN’ Cl- resulted in the isolation of a solid with infrared spectroscopic properties expected for [PPN]‘[$-C,H,Fe(CO),SOJ. There was no evidence of such metathesis,and the isolated materials were those likely originating horn oxidation and/or decomposition of the iron carbony anions (vide infm) *_ In subsequent experiments, reaction mixtures of SO2 and Na’ [q’-C,H,Fe(CO),]- in tetrahydrofruan at ca -78°C were allowed to warm to approximately room temperature, whereupon they acquired a dark reddish-brown color. Depending on the ratio of SO2 to Na’ [$-C,H,Fe(CO)J employed, different products were isolated when solvent was removed and the residue was chromatographed as described in the Experimental section. When the ratio of SO, to Na’ [$-C5H5Fe(CO),]was 1.511, work-up of the reaction mixture afforded [$-C,HsFe(CO),] 2 and two red solids, characterized (vide infra) as [$-C,H,Fe(CO),]zSO,, a major product, and [$-C,H,Fe(CO)],(CO)SO,, a minor product. With a much higher, 30/l ratio of SO2 to Na’ [r$C&Fe(CO)J, the isolated products were [q5-C5H,Fe(CO)J2, [g5-C,H,Fe(CO)&30,, and the dithionite complex [$-C5H,Fe(CO),S0J2. The properties of the sulfur dioxide complexes [$-CSHSFe(CO)J,SO, and [$-CSH5Fe(CO)]2(CO)SO,, both characterized by X-ray crystallography [9,12,13], are described in this paper, whereas the characterization and properties of [$-C,H,Fe(CO)=SO& [lo] will be treafed together with those of other, recently synthesized dithionite complexes in a separ&tepublication [ 141. The dinuclear [$-CsHsFe(CO),],SO, (I) is reasonably stable in the solid; however, its solutions in benzene, CHC& or acetone decompose quite rapidly when exposed to air. An attempted sublimation at 110°C (0.15 To@ for 17 h afforded *
The anion C+-C,H~e
59
only [$-C,H,Fe(CO),], in 66% yield. Likewise, heating [~5-CSH,Fe(CO),],S02 in tetrahydrofuran at reflux for 2 h resulted in the formation of [$-CsHsFe(CO),], (60% yield). This mode of decomposition and the apparent lack of volatility of [$-C5H5Fe(C0)J2SOz both accordwith its observed mass spectrum, which is essentially that of [$-CjHjFe(CO),] 2 [15].
The complex was characterized by elemental analysis and an osmometric molecular weight determination (Table l), and its structure (I) was determined by X-ray crystallography [9,12]. A salient feature of the structure is the presence of sulfur dioxide as an unsupported bridging ligand attached to the iron atoms at short Fe-S bond distances of 2.28 A. Such short bond lengths suggest considerable Fe-to-S r-bonding in these linkages. The infrared v(SOJ absorptions, listed in Table 1, appear to support the above structural feature. The values of 1135 and 993 cm-’ are appreciably lower than those reported for the v(S0,) absorptions of metal carbonyl and related complexes containing either terminally bound SO* or bridging SOz in conjunction with a metal-metal bond. However, they are comparable to the v(SO*) values of other metal carbonyl complexes that incorporate SO* as an unsupported bridging group. These frequencies are given in Table 2. Other factors being equal, a sulfur dioxide ligand bonded to two metals would be expected to receive more n-electron density than an SO, linked to only one metal, thus accounting for its lower v(SOz). The second red complex, [$-C,H,Fe(CO)]2(CO)SO~ (II), a decomposition product of [$-C,H,Fe(C0)J1S02 in solution, was isolated in low and erratic yields from the reaction mixtures of SO, and Na’ [~5-CjH,Fe(CO)J_ The compound crystallizes as large octahedra which, however, undergo rather rapid decomposition on the surface upon exposure to air. This relatively low stability may account for the poor analytical data shown in Table 1. The mass spectrum of [$-C,H,Fe(CO)],(CO)SO,, like that of [$-CSHSFe(C0),],S02, is almost identical with the spectrum of [$-C,H,Fe(C0)J2 1151, indicating decomposition during the measurement. The structure II of this complex was elucidated unambiguously by X-ray crystallography 1133. The molecules contain bridging CO and SO, ligands and possess an overall cis geometry. The presence of a bridging CO is mdicated by infrared absorptions at 1817(sh) and 1807 cm-’ (Table 1). The v(SOz) absorptions at 1185,1175,1045 and 1037 cm-’ occur at higher frequencies than those for [$-CsH,Fe(C0)J2S0,, which, as stated earlier, empirically accords with the presence of a metal-metal bond in the tricarbonyl complex. The complex [7;1’-CSH,Fe(CO)],(CO)SO, joins a growing family of $-cyclopentadienyliron carbonyls that adopt one or both of the isomeric structures IIIa (cis) and IIIb (Pans). This group includes members with L = L’ = CO [16,17], L = L’ = CS [lS], L = CO and L’ = Ge(CH,), [19], L = L’ = CNR [20,21], and
D,OBS 5,OBS (BJSS)
w32) 1136,w3 1186,1175, 1046,1037
WO)
2027s,2016vs, lI)BBa, 1lltiavs o 204Ovs, lDOiSm~a, 1817(sh), lS07m-8 d
111NMR (f,mm) b
DIOXIDE COMPLEXES
40.46 (40.23) 38,0-36.5 (40.04)
C
2.01 (2.41) 2.18-2.27 (2.68)
11
AnalysL (Found (calcd.)) (9b)
7,76 (7.67) 6.71-7.00 (9.22)
S
(3W
,,
(418) 819,538
416
”
Mol. wt. (Pqk&(calcd,))
__ _.
-. -. -.
-. .^ __ __
__
._ - -
-
-- _ _,_
E(X)2--I;‘e(CO)2(~5.C~H5), dopendlne on tho conformation, * WC13 aOhthxL
-
__
.-
-. -
__
--
a Nujol mull except 88 noted, Abbrevlntlons: w, vary strona; 8, strong; m, modlum; (sh) shoulder. b CDC13 or (IWotontPd6) solution and taunothylsllane as an internal standard. Abbroviatlon: 8, etnglet. ’ Simple E&P thoorotical conoideratlons urodict 2, 3 or 4 IR-actlvo V&O) absorptionsalor comploxos of the typo T~~*C~H~(CO)~FO--
[05-C5R51Fe(CC)12(CC)SC2
[~5*CS~&(CC)212SC2
IR
Complex
(cm-l) a
DATA FOR IRON-SULFUR
PHYSICAL AND ANALYTICAL
TABLE 1
,
‘,
,‘,
61 TABLE
2
INFRARED
~_ V
OF SOME
METAL-SULFUR
DIOXIDE
COMPLEXES
Complex
Type o
V(SOz)
~‘~sH~
A Lg.‘,21
~6C
A
1135.993 1078.1072.984 1138.980
This work C333
1138.978
1341
1185.1175. 1045.1037 1210.1196.1049
This work
C
A
c(CRJ)4N32C
A B Cl31
B C301 C L311 C CC321 C' c31 C' [21
(cm-‘)
b
1282d 1253d 1258.1105-1093 1214.1188.1057= 1198.1185.104%c
Reference
r.341
=
c231 E351 C361 c371 ml Cl1
o A = unsupported SO2 bridge: B f SOzbridge and M-M bond: C = terminal SO2. planar MSO?: C' = terminal SO2. nonplaaax MS02. Structures determined by X-my techniques are referenced. b In Nujoi mull except as noted_ c KBr pellet. a Benzene solution.
L = CO and L’ = CNR 1211, inter alia. The infrared spectra of the L = L’ = CO complexes, in particular, have been thoroughly investigated in several solvents,
(II) and an assignment of the v(C0) bands was made to the two isomeric species 1221. By analogy with this assignment, the v(C0) absorptions at 2040, 1995, and 1807 cm-’ in CHC13 solution (Table 1) may be attributed to the cis isomer of [$-C,-H,Fe(CO)],(CO)SO,, which appears to be the sole species in the isolated solid. The origin of the shoulder at 1817 cm-’ is uncertain_ It may well be that some tmns-[as-CSHsFe(CO)] 2(CO)SOI? exists in solution, for its infrared terminal Y(CO) absorption would probably overlap with the band at 1995 cm-’ [22].
Iiowevt$ if tbi$ isomer does exist, it must be present in low concentrations as infe&d from the relative-intensities of the-Y(CO) bands at 2040 and 1995 cm‘-‘_ It is worthy of note-that only one $-C&H5 signaloccurs in the ‘H NMR spectraof the complex in CDC13 or_acetone-d,+ Detailed studies on ci.+tr&~ isomerism in [$-C,H,Fe(CO)],(CO)SO, were not undertaken because of a rather low stability of the complex in solution. Attempts
at tmpping
[qs-CJ&Fe(CO)~S027_
Unsuccessful &$empts at isolation of [r15-CSH,Fe(CO)zS0,] from tetrahydrofuransolution by the addition of PPN+ Cl- (vide supra) led to experiments aimed at trapping the above anion with various alkylating reagents, particularly with CHJ_ These reactions were conducted by adding the alkyl halide (or another alkylating reagentj to a tetrahydrofuran solution of Na+ [$-C,HsFe(CO)J tid SO, prepared at low temperatures (generally -78OC). The reaction conclitions and the results of these experiments are summarked in Table 3. Focussing on the data from the ma&ions that utilized CH31, it is of interest that both $-C&H,Fe(CO),I and ~5-C,H5Fe(CO),S(0),CH3 were isolated as products. In those experiments where the quantities of the two iron dicarbonyl products were determined, the yield of the S-sulfinato complex (46%) substantially exceeded that of the iodo complex (<15%). The formation of q*-CsH,Fe(CO)J may appeal surprising and suggestive that the iron csrbonyl-ysulfur dioxide precursor of the isolated products is not [$-C,H,Fe(CO),SO,]-. This is because metal carbonyl anions generally react with alkyl halides to afford the alkylmetal carbonyls, but not the corresponding metal carbonyl halides [S]. Since the presumed [q5-C,H,Fe(CO),SOJ appears to undergo conversion to the isolable [$-CSHsFe(CO)JtSO+ under the experimental conditions that parallel those of the alkylation, reactions of this dinuclear complex with CH,I were examined to shed more light on the origin of the products. The reaction (eq. I), conducted neat and in tetrahydrofuransolution, pro[~S-C,H,Fe(CO),],SO,
+ CHJ + $-C,HsFe(CO)2S(0)1CH3
+ ~s-C,H,Fe(CO),I
ceeded at a reasonable rate upon heating to afford good yields of $-C,H,Fe(CO),I (54-56s) and much lower yields of $-CSH,Fe(C0)2S(0),CH, (21-26%). Thus it appears that [$-CSHSFe(C0)J2S02 is not the primary source of the S-sulfinato product formed by the al&+&ion of the solutions of Na’ [q5-CSHsFe(CO)J and SO, at low temperatures. Whether the anion [$-C,H,Fe(CO)$OJ is the principal precursor of the S-sulfinate cannot be stated with certainty. However, this may well be so for the following reasons. Reactions of CH,I with tetrahydrofuran solutions of Na’ [$-CSHsFe(CO),]and equimolar SO* yield very little, if any, [$-C5H,Fe(CO),],S0, when the solutions are allowed to warm to approximately room temperature. This indicates that CH,I quite effectively traps either [~5-C5H5Fe(CO),],S0, or a precursor thereof- The low temperatures employed in these reactions, along with considerations of reactivity of CHjI toward various iron carbonylsuifur dioxide complexes, both suggest that the trapped species is either [q5-C,H,Fe(CO),SOJ or one with similar expected chemical properties. The reaction of Na’
21.4 mmol over 80 mln at -78’C, stir 100 min nt -7S’C, wnrm f for 26 min
41.6 mmol over G,Gh at -7E°C, wnrm f for 2.G h 20 mm01 at -70 to -GO’C
20 mm01 st -7O’C
VI
VII
VIII
IX
21.1 mm01 of (CII3O)$$O2, stirr 22 h 100 mmol of CII3Br nt -70 to --GoOc, stir 22 I1 et -70 to -GO’C, stir B h nt -20 to -13Oc 20 mm01 of CeH.jCII2Cl nt -7occ, stir GO11at -70 to -43Oc
40,l mmol of CH31 nt -78’C, stir 105 h, warm for 3,S 11 20 mmol of CH$ at -7O’C, stirr 11 h nt -70 to -3O’C 48 mlnO1 Of p-CH$&&S0@~3, stir 21 I1
30 mm01 of CH$, 6th 12 h 32,l mmol of CH31, 6th 1G h
48 mm01 of CH31, stir 21 h
Addition of RX ’
lG9b ~~C~II~PC(CO)~S(O)~CH~C~II~; no IR evidcncc of r$C5115Fc(CO)2Cl
46% t75-C~I~~Pc(Co)~s(o)~CM~, iB% q5-c5Hs~e(c0)21 2% ~5-CSHsPe(CO)2S(O)2CH3, c11~-c5~15Pc(c0)212s02, [qs~C~H~Fe(CO)12(CO)S02 No SR evidence of ~~“-C~HSPC(CO)~S(O)~CH~; [~~~C~I~~FC(CO)~J~SO~,[~5-C~~I~Pe(CO)1~(CO)SO~ GO9iJ~5-C~I~~I~c(Co)~s(o)~CH3; no IR cvidcncc of $CSH#c(CO)2Br
469b t15-CSHSPe(CO)2S(0)2CI~~, 4% BQl~H~Pe(CO)21 18.4% $.CSH~F~(CO)~S(O)~CH~~ 26.1% ~~.CSH~FC(CO)~S(O)~CH~ ‘I, [~s~C~~I~Pe(CO)2]2S02 22.4% q5CgH5Fe(C0)2S(0)2CH3 g
Products ‘I ‘1 ’
__ __ _. .
--
._ -
___
_
__
. .
.-
_ _ . . -_ -_
-
_ __
--
’ From 10 mmol nf [7$C~H5lk(CO)212. ’ Followh~g “ndditlon of SO$‘. ’ [~5C~HsIQ(CO)2)2 wns obtnlncd in nll cxperirnents. ’ The formotion of SC~H$c(C0)21 wns not cxnminccl in cxpcrimcnts II, III, nut1 IV. ’ Other, minor products were nlso detected upon chromntogrnphy but were not fully charncterbcd. ‘) After the cooling bath hnd bccn removed, the rcnction flnslc wns mnintnhicd at room tcmpcruturc. g Possible losses sustnincd through coprccipitation with NaI.
V
20 mmol over 4 h at -78eC, stir 1 11at -7&l”c 20 mm01 at’-70’C
21.4 mm01 over 80 min nt -78’C, stir 100 miu at -78’C, warm r for 26 miu 28.4 mmol over 4 h at -7E°C,wnrm f for 1 11 41.6 mmol over 3 h ut -78’C, worm ‘for 0 h
Addition of SO2
IV
II III
I
mcnt
Experi-
REACTIONS OF Nn+ [~5~C5115P~(C0)2]- ’ WITH SOg-RX IN TETRAHYDROFURAN
TABLE 3
64
[$-C,H,Fe(CO),] with C’H,I to give q5-C5H,Fe(C0)&H,, followed by SO, insertion (eq, Z), a reasonable alternative to the above proposal, may be readily Na’ [qS-C$I,Fe(CO),] q5-C,H,Fe(CO),CH,
+ Cl-&I + $-C,H,Fe(CO)&H,
+ NaI
+ SO, + q5-C,H,Fe(CO),S(O),CH,
(2)
dismissed from the reported kinetic data 1231 and from the following additional experiments_ First, there is nc observable reaction between $-C5HSFe(CO),CH,C,H, and SO2 under the conditions that mirror those of Experiment IX in Table 3. Second, as reported previously [24], reaction of Na* [$-C,H,Fe(CO)J with SO, followed by BrCH2GCCH, yields qS-CSH,Fe(CO),S(0)#H,~CCH,, whereas q*-C,H,Fe(CO),CH,eCCH, and SO, afford q5-C,H,Fe(CO)&=C(CH,)S(O)OCH,. Third, the interaction of ClCH,CH=C(CH,), with a mixture of Na’ [$-CSHsFe(CO)J and SO, affords $-C5H,Fe(CO),S(0),CH,CH=C(CH,), exclusively, but q5-CsHsFe(C0)&H2CH=C(CH,), and SO2 yield the two isomers $-C,H,Fe(CO),S(0)&H,CH=C(CH,)2 and q5-CsH,Fe(~)2S(0)2C(CH,),CH= CH, [25]_ The formation of both qS-C5HSFe(C0)2S(0)2CH3 and q5-C5HSFe(CO)tI in the reactions under discussion may indicate that these products are derived in part from [$-C,H,Fe(CO),],SO, and CHJ. Alternatively however, the interaction between [q’-CSH,Fe(CO),SOJ ( or a species with similar expected reactivity) and CHsI may be a free radical one, affording both the iodo and S-sulfinato complexes. An earlier study [26] of the reaction of a tetrahydrofuran solution of Na’ ]q*-C,H,Fe(CO)J and SO, with optically active BrCH(CH&,H, * revealed complete loss of stereochemistry upon the formation of q5-C,H,Fe(CO),S(0)&H(CH,)C6H5. This would seem to indicati a free radical pathway, a mechanism consistent with the nature of the products obtained in the alkylation reactions described herein. Notwithstanding uncertainties in the identity of the reactive iron carbonylsulfur dioxide species, the solutions of Na’ [$-C,H,Fe(CO)J and SO2 serve as ?Iuseful reagent for the preparation of iron S-sulfinates that are inaccessible via the SO2 insertion reaction 124,251. Very likely they possess a wider synthetic utility, which, however, still remains to be explored. Sumlmary of reactions In conclusion, we wish to present a summary of reasonable pathways leading to the formation of various ironsulfur dioxide produck investigated in this work. These pathways are depicted in Scheme 1. Because of the complexity of the reaction system Na’ [q5-CSH,Fe(CO),]
and SQ, parts of the scheme are admittedly speculative_ Moreover, no attempt was made to present all possible reactions; only those thought to be essential m-the formation of various observed products are included. The identity cf Ghe oxidizing Bgent [0] is unknown; it may be SO*, as air was excluded from these solutions. The species $-CSHSFe(CO)zS02 may undergo loss of SO* by analogy
*
The erperimenhl
conditions
Na+ [?$CsHsFe
for this
reaction
were
similar
+ SO2 with ClCH2CH=C(CH&
to those employed f251.
for
the
reactionof
65 SCHEME
1
[+CSHSFe(CO),]-=
[$-CSHSFe(CO),SO,]-
q5-C,H,Fe(CO),
1 q5-C5H5Fe(C0)$302
co1
1
dimerize
dime&e 1
[$-C5H,Fe(CO),S0J2
I~5-GH5Fe(C%12 11
C~S-WWdC0M2~02 1
-CO
[$-C5H5Fe(CO)]z(CO)SO~ with the reported [27] lability of metal carbonyl radicals_ Coupling between the radicals $-CSH5Fe(C0)2 and $-C5H5Fe(C0)&102 would then account for the formation of [$-C,H,Fe(CO),],, [s’-C5H5Fe(CO),],SOl, and [$-C5H5Fe(C0)1‘SOJ2. The complex [$-C5H5Fe(CO)J2S02 does not arise directly from [q5C,H,Fe(CO),], and SO*, since we have shown that such an insertion reaction does not proceed at temperatures up to 25°C. However, it is worthy of note that reaction between [$-C5HsFe(CO)z]z and SO, at 40°C led to the isolation of a polynuclear (~5-C5H5)4Fe4(CO),(SO~)~ upon work-up [28] *_ Experimental Reactions were conducted in an atmosphere of nitrogen, which was also used routinely in the handling of organometallic compounds_ Florisil(60-100 mesh) and Ventron or Woelm alumina, deactivated with Hz0 (generally 6%), were employed in chromatographic separations and purifications_ Anhydrous grade SO2 was purified as described previously [243. Tetrahydrofuran (THF) was freshly distilled from CaH, or LiAlH, under nitrogen. All other chemicals
and solvents procured commercially were reagent grade or equivalent quality and were used without further purification. Melting points were obtained on a Thomas-Hoover capillary melting point apparatus and are uncorrected. Proton NMR spectra were taken on a Varian Associates A-60 or _4-60A spectrometer. Infrared (IR) spectra were recorded on a Pa&in-Elmer 337 or Beckman IR-9 spectrophotometer using polystyrene film for calibration. Mass spectra were recorded by Mr. CR. Weisenberger on
an A.E.I. Model MS-9 spectrometer at 70 eV. Molecular weights were measured on a Mechrolab Model 301-A vapor pressure osmometer in CHCls solution. Elemental analyses and some molecular weights were obtained by Galbraith Laboratories, Inc., Knoxville, Tenn., and Pascher Mikroanalytisches Laboratorium, Bonn, Germany. * the po&bfity that [q5-C5H.9e(CO)~3-$30~ ‘+ecovcred” [$-C5HSFe(CO).& cannot employed
in the work-up.
was formed in this reaction but decomposed to the be ruled out because of the rather high temper&-ares
66
Reactioza of Na’ [q5-C&T$&CO)J with SO2 A, THF-solution (120 ml) of Na’ [~5-CSH5Fe(CO),r, prepared from 1.77 g (5.0 mmol) of [q5-CSH,-Fe(CO),], and freed from excess sodium amalgam and mercury, was cooled to ca. -78k and treated with 0.96 g (15 mmol) of SOS dissolved in 20 ml of THF over a period of 10 min. The cooling bath was removed and the reaction mixture was allowed to warm to room temperature in 45-60 min. The solvent was evaporated in vacua at room temperature, the residue was dissolved in CHCIB, and the resulting solution was filtered through Florisil. The Florisil &as washed with acetone and the combined wash and filtrate were evaporated to dryness. The residue was dissolved in minimum CHC13 and chromatographed on a 2;7 X 25 cm column of Florisil. Chloroform eluted off a purple band containing [~5-C,H,Fe(CO),],, 10/l CHClJacetone removed a narrow red band of [~5-C5H,Fe(CO),(CO)S0,, and then acetone removed another red band of [q5-C,H,Fe(CO)],(CO)SO,, and then acetone removed another red dryness, the residue was dissolved in minimum CHC&, filtered, and the product was precipitated by the addition of per&me at 0°C. The yields of [q5-C,H,Fe(CO)],(CQ)SO* and [~5-C5H,-Fe(C0)2]zS02, dec. 142”C, were 0.04 (2%) and 0.4-0.6 g (29-30%), respectively. Physical and analytical data for these complexes are furnished in Table 1. Reaction between Na’ [n5-C,H,Fe(CO)J and SO, in THF was also carried out exactly as described above, but with a much larger, 7.0 g (110 mmol) amount of SO+. Chromatography on Florisil afforded a purple band containing [q5C,H,Fe(CO)I]z (0.36 g), which was eluted off with CHCIJ, an orange band ( E~5-C,H5Fe(CO),SO_], 2) removed with 5/l CHClJacetone, and a red band (Cr15-C5H~Fe(CO)211SO~)removed with acetone. The yields of [q5-C5H5Fe(CO),SO& and [$-C5H5Fe(CO),]zSOz were 0.40 (17%) and 0.14 g (7%), respectively. Reaction of Na’ [q5-CJT$e(CO)J with SO2 followed by CHJ A representative alkylation reaction of a mixture of Na’ [q5-CSH5Fe(CO)J and SOi is described below. A THF solution (150 ml) of Na’. [$-C5HsFe(CO)J, prepared from 3.54 g (10.0 mmolj of [q5-C5HsFe(C0),],_, was cooled to -78°C. Sulfur dioxide (0.94 ml of liquid, 21 mmol) was then passed into this solution in a stream of nitrogen over a period of 80 min. The resulting red reaction mixture was stirred at -7S”C for 100 min, allowed to warm for 25 min, treated with CHd (G.&g, 48 mmol) and stirred at room temperature under a Dry Ice-cooled condenser for 21 h. Filtration, solvent removal from the filtrate, and chromatography of the residue on alumina (6% H20) eluting with CHClJacetone led to the isolation of a mixture of [$-CSHsFe(CO),]-_ and q5-C5H5Fe(CO),I (0.80 g, 15 and 4%, respectively, by IR spectroscopy) and of $-CjH5Fe(CO)zS(0)&H3 (2.36 g, 46%). The insoluble solid from the reaction mixture was shown to be NaI (l-25 g)_ Several other alkylation reactions were carried out under analogous and somewhat modified experimental conditions, These conditions and the results are summarized in Table 3. The S-sulfinates ??5-C5H,Fe(CO),S(0)tR, all known compounds [29], were characterized by IR spectroscopy.
67
Reaction
of [q5-C$?~e(CO)J2SOz
with CHJ
A solution of 0.300 g (0.718 mmol) of [q5-CgH5Fe(CO)I!]tSO+ in 20 ml of CH,I in a sealed glass tube was maintained at SO-85°C for 3 h. The tube was cooled to room temperature and opened, the solvent was removed, and the residue was chromatographed on alumina to afford 0.245 g (56% yield) of qs&,H,Fe(CO),I and 0.096 g (26% yield) of $-CSHSFe(CO),S(0),CH,. When the same reaction between 0.230 g (0.550 mmol) of [qS-C,H,Fe(CO),],SO, and 3.0 ml (48 mmol) of CH,I was carried out in THF (20 ml) at reflux, 0.179 g (54% yield) of $-C,H,Fe(CO),I and 0.059 g (21% yield) of q5-C,H,Fewere isolated upon chromatography. There was no evidence of (CC),S(G)&H,
CrlS-WWdCOM,.
Acknowledgements We gratefully acknowledge support of this work by the National Science Foundation (Grant No. CHE76-02413 AOl) and the North Atlantic Treaty Organization (Grant No. 604 with Professor M. Graziani). P.R.-R. thanks The Ohio State University Graduate School for a Postdoctoral Fellowship. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
L. Vaska and S.S. Bath. J. Amer. Chem. Sot.. 88 (1966) 1.333. S.J. La Piaca and J-A. Ibea. Ino%_ Chem. 5 (1966) 405. K-W. Muir and J.A. Ibers. Inorg. Chem.. 8 (1969) 1921. D.C. Moody and R.R. Ryan. Inorg_ Chem.. 15 (1976) 1823. P-G. ElIer. R.R. Ryan and D.C. Moody. Inorg. Chem.. 15 (1976j.2442. See. for example. R-B. King. Advan. OrganometaI. Chem.. 2 (1964) 157. R.E. Dessy. R.L. PohI and R.B. King. J_ Amer. Chem. Sot.. 88 <1966) 5121. J.E. EUs. R.W. Fennelland E.A. Flom, Inorg. Chem.. 15 (1976) 2031. M-R. ChurchiII. B.G_ DeBoer. K_L. Kah-a. P. Reich-Rohrwig and A_ Wojcicki, J. Chem. Sot.. Chem. Commue. (197’2) 981. N-H. Tennent. S.R. Su. CA. Poffenberger and A. Woicicki. J. OrganometaL Chem.. 102 (1975) C46. J.K. Ruff and W.J. Schlientz. Inorg. Syn.. 15 (1974) 84. M.R. Churchi.B. B-G_ DeBoer and KL. Kalra. Inorg. Chem.. 12 (1973) 1646. M.R. ChurchiII and K.L. Kaha. Inorg. Chem.. 12 (1973) 1650. CA. Poffenberger, N.H. Tennent and A. Wojcicki. to be submitted for publication. E. Schumacher and R. Taubenest. Helv. Chim. Acta, 49 (1966) 1447. OS. MiBs. Acta CrystaBogr.. 11 (1968) 620. R.F. Bryan. P.T. Greene. D.S. Field and M.J. Newlands. J. Chem. Sot.. Chem. Commun.. (1969) 1477. J.W. Dunker. J-S. Finer. J. CIardy and R.J. Angelici. J. Organometal. Chem.. 114 (1976) C49. R.D. Ad-, M.D. BrIce and F.A. Cotton. Inorg. Chem.. 13 (1974) 1080. F.A. Cotton and B.A.Frentz.Inorg_ Chem.. 13 (1974) 253. J.A.S. Howe& M.J. Mays, I.D. Hunt and O.S. Mills. J. Organometal. Chem.. 128 (1977) C29. AR. Manning, J. Chem_ Sot A. (1968) 1319. S.E. Jacobson and A. Wojcicki, Inorg. Chim. Acta. 10 (1974) 229. J.E. Thomasson. P.W. Robinson, D.A. Ross and A. Wojcicki. Inorg. Chem.. 10 (1971) 2130. R-L. Doand A. Wojcicki, Inorg. Cbim. Acta. in press. J-J_ Alexander and A Woicicki. Inorg. Chim. Acta. 5 (1971) 655. M.S. Wxighton and D.S. GInley. J. Amer. Chem. Sot;. 97 (1975) 2065. D.S. Field and M.J. Newlands. J. Organometal Chere. 27 (1971) 221. J.P. Bibler and A. Wojcicki. J. Amer. Chem Sot.. 88 (1966) 4862. J. Meunier-Piret. P. Piret and M. van Meerssche. BulL Sot. Chim. BeIg.. 76 (1967) 374. C. Berbeau and R.J. Dubey. Can. J. Chem. 51 (1973) 3684. R.R. Ryan. P.G. EBer and G.J. Kubas. Inorg. Chem.. 15 (1976) 797. A.A. Vi’cekand F. Basolo. Inorg. Chem. 5 (1966) 156.
68 34
_
-. : J-5
Rx&f, Inorg:C+wa.,
35 W:StrohuMer 36
W_ hohmeier,
37
Ii: Ciainkr.
6 (1967)
5080.
:-
‘.: -:
and J.F.~Gutt&nbergei, Chem. Be+ 97 (1964) I&, h POPS and J,F_ G; ttklbekm. cherir Ber.,?S (1966) J. Anier. &em. Sdc; 39 (iSi57, i5377.
:
:. 1. 165. ._.
--
Journal
if
@ Elkier
Organometallic &hem&&. 145 (1978) 57-68 Sequoia S.A., Lausanne- Printed in The Netherlands
REACTION OF SODIUM +CYCLOPENTADIENYLDICARBONYLFERRATE(O) WITH SULFUR COMPLEXES
DIOXIDE.
SYNTHESIS
OF IRON-SULFUR
DIOXIDE
PGTER REICH-ROHRWIG, ALAN C. CLARK, RAYMOND L. DOWNS- and ANDREW WOJCICKI * The McPherson (U.S.A.)
Chemical
Laboratory,
The Ohio
State
University,
Columbus.
Ohio
43210
(Received August 22nd, 1977)
Sulfur dioxide reacts at -78°C with Na’ [qS-C,H,Fe(C0)2]-, prepared by the reduction of [q5-CsHsFe(CO),], with sodium amalgam in tetrahydrofumn, to g4ve a red solu~on containing a species which can be alkylated with RX to q5-CSH5Fe(CO)2S(0)2R. The alkylation reaction with CH,I affords both $C,H,Fe(CO),S(O),CH, and $-C,H,Fe(CO),I. The nature of this solution and the possible existence of the anion [q5-CSHSFe(CO),SOJ therein are discussed. Upon warming to room temperature and chromatography, the solutions of Na’ [$-CsHsFe(CO),]and SO2 afford the isolable iron-sulfur dioxide complexes, [qS-C,H,Fe(CO),],S0,, [$-C5H,Fe(CO)]z(CO)S02, and I$‘-CSH,Fe(CO),SO,],. The characterization and properties of the first two compounds are described.
Introduction
Sulfur dioxide behaves as a Lewis acid toward a number of low-valent transition metals in complexes. Examples of such interactions are found in Ir[PW$-WJ,~(COKQ 11,213 RhIP(C6H~5)312CI(CO)SO* C1,3], WW,H,),I,(SO,), . C&H8[4], and Pt[P(C6H5)J3S02 * 0.7 SO2 [5]. These complexes contain nonplanar MSOz moieties with a pyramidal configuration about the sulfur, indicative of the presence of a lone pair of valence electrons thereon. Transition metal carbonyl anions undergo reactions with a number of electrophilic reagents, including protic acids, alkyl halides, and various other organic as well as organometallic compounds, especially those containing halogens 163. The anion [$-CsHsFe(CO)J, in particular, has been found to behave as a powerful nucleophile [ 71. The observed high degree of nucleophilicity of
Cr15-C$-&Fe(CO)2r suggested that it would interest readily with SO, to form a l/l adduct, This adduct is expected to exhibit “nonplanar” Fe-SO* bonding, similar in nature to that found for the aforementioned noble metal complexes. The interaction of I$-CSHsFe(CO)Jwith CS2, a weaker electrophile than SO,, to yield [$-CSHSFe(CO)$SZ] was reported very recently [S]. In this paper are described our studies on reaction between Na’ [$-C,H,Fe(CO),] and SO*. As the investigation progressed it became apparent that the reaction in question is quite complex and affords several Fe-SO, products, the nature of which depends on the experimental conditions. Some aspects of this study were communicated earlier [9,10]. Presented herein is a full account. Results and discussion Reaction of Na’ [$4&H5Fe(CO)J with SO2 Gaseous SO, was passed slowly into a tetrahydrofuran solution of an approximately equimolar amount of Na’ [$-CSHjFe(CO)J, prepared by the reduction of [@-C,H;Fe(CO),], with sodium amalgam and cooled to ca. -78°C. The resulting solution v& treated with bis(triphenylphosphine)iminium chloride (PPN’ Cl-) [ll] at -78°C and above in attempts to obtain [PPN]‘[$-CSHjFe(CO)lSO,]. However, none of the additions of PPN’ Cl- resulted in the isolation of a solid with infrared spectroscopic properties expected for [PPN]‘[$-C,H,Fe(CO),SOJ. There was no evidence of such metathesis,and the isolated materials were those likely originating horn oxidation and/or decomposition of the iron carbony anions (vide infm) *_ In subsequent experiments, reaction mixtures of SO2 and Na’ [q’-C,H,Fe(CO),]- in tetrahydrofruan at ca -78°C were allowed to warm to approximately room temperature, whereupon they acquired a dark reddish-brown color. Depending on the ratio of SO2 to Na’ [$-C,H,Fe(CO)J employed, different products were isolated when solvent was removed and the residue was chromatographed as described in the Experimental section. When the ratio of SO, to Na’ [$-C5H5Fe(CO),]was 1.511, work-up of the reaction mixture afforded [$-C,HsFe(CO),] 2 and two red solids, characterized (vide infra) as [$-C,H,Fe(CO),]zSO,, a major product, and [$-C,H,Fe(CO)],(CO)SO,, a minor product. With a much higher, 30/l ratio of SO2 to Na’ [r$C&Fe(CO)J, the isolated products were [q5-C5H,Fe(CO)J2, [g5-C,H,Fe(CO)&30,, and the dithionite complex [$-C5H,Fe(CO),S0J2. The properties of the sulfur dioxide complexes [$-CSHSFe(CO)J,SO, and [$-CSH5Fe(CO)]2(CO)SO,, both characterized by X-ray crystallography [9,12,13], are described in this paper, whereas the characterization and properties of [$-C,H,Fe(CO)=SO& [lo] will be treafed together with those of other, recently synthesized dithionite complexes in a separ&tepublication [ 141. The dinuclear [$-CsHsFe(CO),],SO, (I) is reasonably stable in the solid; however, its solutions in benzene, CHC& or acetone decompose quite rapidly when exposed to air. An attempted sublimation at 110°C (0.15 To@ for 17 h afforded *
The anion C+-C,H~e
59
only [$-C,H,Fe(CO),], in 66% yield. Likewise, heating [~5-CSH,Fe(CO),],S02 in tetrahydrofuran at reflux for 2 h resulted in the formation of [$-CsHsFe(CO),], (60% yield). This mode of decomposition and the apparent lack of volatility of [$-C5H5Fe(C0)J2SOz both accordwith its observed mass spectrum, which is essentially that of [$-CjHjFe(CO),] 2 [15].
The complex was characterized by elemental analysis and an osmometric molecular weight determination (Table l), and its structure (I) was determined by X-ray crystallography [9,12]. A salient feature of the structure is the presence of sulfur dioxide as an unsupported bridging ligand attached to the iron atoms at short Fe-S bond distances of 2.28 A. Such short bond lengths suggest considerable Fe-to-S r-bonding in these linkages. The infrared v(SOJ absorptions, listed in Table 1, appear to support the above structural feature. The values of 1135 and 993 cm-’ are appreciably lower than those reported for the v(S0,) absorptions of metal carbonyl and related complexes containing either terminally bound SO* or bridging SOz in conjunction with a metal-metal bond. However, they are comparable to the v(SO*) values of other metal carbonyl complexes that incorporate SO* as an unsupported bridging group. These frequencies are given in Table 2. Other factors being equal, a sulfur dioxide ligand bonded to two metals would be expected to receive more n-electron density than an SO, linked to only one metal, thus accounting for its lower v(SOz). The second red complex, [$-C,H,Fe(CO)]2(CO)SO~ (II), a decomposition product of [$-C,H,Fe(C0)J1S02 in solution, was isolated in low and erratic yields from the reaction mixtures of SO, and Na’ [~5-CjH,Fe(CO)J_ The compound crystallizes as large octahedra which, however, undergo rather rapid decomposition on the surface upon exposure to air. This relatively low stability may account for the poor analytical data shown in Table 1. The mass spectrum of [$-C,H,Fe(CO)],(CO)SO,, like that of [$-CSHSFe(C0),],S02, is almost identical with the spectrum of [$-C,H,Fe(C0)J2 1151, indicating decomposition during the measurement. The structure II of this complex was elucidated unambiguously by X-ray crystallography 1133. The molecules contain bridging CO and SO, ligands and possess an overall cis geometry. The presence of a bridging CO is mdicated by infrared absorptions at 1817(sh) and 1807 cm-’ (Table 1). The v(SOz) absorptions at 1185,1175,1045 and 1037 cm-’ occur at higher frequencies than those for [$-CsH,Fe(C0)J2S0,, which, as stated earlier, empirically accords with the presence of a metal-metal bond in the tricarbonyl complex. The complex [7;1’-CSH,Fe(CO)],(CO)SO, joins a growing family of $-cyclopentadienyliron carbonyls that adopt one or both of the isomeric structures IIIa (cis) and IIIb (Pans). This group includes members with L = L’ = CO [16,17], L = L’ = CS [lS], L = CO and L’ = Ge(CH,), [19], L = L’ = CNR [20,21], and
D,OBS 5,OBS (BJSS)
w32) 1136,w3 1186,1175, 1046,1037
WO)
2027s,2016vs, lI)BBa, 1lltiavs o 204Ovs, lDOiSm~a, 1817(sh), lS07m-8 d
111NMR (f,mm) b
DIOXIDE COMPLEXES
40.46 (40.23) 38,0-36.5 (40.04)
C
2.01 (2.41) 2.18-2.27 (2.68)
11
AnalysL (Found (calcd.)) (9b)
7,76 (7.67) 6.71-7.00 (9.22)
S
(3W
,,
(418) 819,538
416
”
Mol. wt. (Pqk&(calcd,))
__ _.
-. -. -.
-. .^ __ __
__
._ - -
-
-- _ _,_
E(X)2--I;‘e(CO)2(~5.C~H5), dopendlne on tho conformation, * WC13 aOhthxL
-
__
.-
-. -
__
--
a Nujol mull except 88 noted, Abbrevlntlons: w, vary strona; 8, strong; m, modlum; (sh) shoulder. b CDC13 or (IWotontPd6) solution and taunothylsllane as an internal standard. Abbroviatlon: 8, etnglet. ’ Simple E&P thoorotical conoideratlons urodict 2, 3 or 4 IR-actlvo V&O) absorptionsalor comploxos of the typo T~~*C~H~(CO)~FO--
[05-C5R51Fe(CC)12(CC)SC2
[~5*CS~&(CC)212SC2
IR
Complex
(cm-l) a
DATA FOR IRON-SULFUR
PHYSICAL AND ANALYTICAL
TABLE 1
,
‘,
,‘,
61 TABLE
2
INFRARED
~_ V
OF SOME
METAL-SULFUR
DIOXIDE
COMPLEXES
Complex
Type o
V(SOz)
~‘~sH~
A Lg.‘,21
~6C
A
1135.993 1078.1072.984 1138.980
This work C333
1138.978
1341
1185.1175. 1045.1037 1210.1196.1049
This work
C
A
c(CRJ)4N32C
A B Cl31
B C301 C L311 C CC321 C' c31 C' [21
(cm-‘)
b
1282d 1253d 1258.1105-1093 1214.1188.1057= 1198.1185.104%c
Reference
r.341
=
c231 E351 C361 c371 ml Cl1
o A = unsupported SO2 bridge: B f SOzbridge and M-M bond: C = terminal SO2. planar MSO?: C' = terminal SO2. nonplaaax MS02. Structures determined by X-my techniques are referenced. b In Nujoi mull except as noted_ c KBr pellet. a Benzene solution.
L = CO and L’ = CNR 1211, inter alia. The infrared spectra of the L = L’ = CO complexes, in particular, have been thoroughly investigated in several solvents,
(II) and an assignment of the v(C0) bands was made to the two isomeric species 1221. By analogy with this assignment, the v(C0) absorptions at 2040, 1995, and 1807 cm-’ in CHC13 solution (Table 1) may be attributed to the cis isomer of [$-C,-H,Fe(CO)],(CO)SO,, which appears to be the sole species in the isolated solid. The origin of the shoulder at 1817 cm-’ is uncertain_ It may well be that some tmns-[as-CSHsFe(CO)] 2(CO)SOI? exists in solution, for its infrared terminal Y(CO) absorption would probably overlap with the band at 1995 cm-’ [22].
Iiowevt$ if tbi$ isomer does exist, it must be present in low concentrations as infe&d from the relative-intensities of the-Y(CO) bands at 2040 and 1995 cm‘-‘_ It is worthy of note-that only one $-C&H5 signaloccurs in the ‘H NMR spectraof the complex in CDC13 or_acetone-d,+ Detailed studies on ci.+tr&~ isomerism in [$-C,H,Fe(CO)],(CO)SO, were not undertaken because of a rather low stability of the complex in solution. Attempts
at tmpping
[qs-CJ&Fe(CO)~S027_
Unsuccessful &$empts at isolation of [r15-CSH,Fe(CO)zS0,] from tetrahydrofuransolution by the addition of PPN+ Cl- (vide supra) led to experiments aimed at trapping the above anion with various alkylating reagents, particularly with CHJ_ These reactions were conducted by adding the alkyl halide (or another alkylating reagentj to a tetrahydrofuran solution of Na+ [$-C,HsFe(CO)J tid SO, prepared at low temperatures (generally -78OC). The reaction conclitions and the results of these experiments are summarked in Table 3. Focussing on the data from the ma&ions that utilized CH31, it is of interest that both $-C&H,Fe(CO),I and ~5-C,H5Fe(CO),S(0),CH3 were isolated as products. In those experiments where the quantities of the two iron dicarbonyl products were determined, the yield of the S-sulfinato complex (46%) substantially exceeded that of the iodo complex (<15%). The formation of q*-CsH,Fe(CO)J may appeal surprising and suggestive that the iron csrbonyl-ysulfur dioxide precursor of the isolated products is not [$-C,H,Fe(CO),SO,]-. This is because metal carbonyl anions generally react with alkyl halides to afford the alkylmetal carbonyls, but not the corresponding metal carbonyl halides [S]. Since the presumed [q5-C,H,Fe(CO),SOJ appears to undergo conversion to the isolable [$-CSHsFe(CO)JtSO+ under the experimental conditions that parallel those of the alkylation, reactions of this dinuclear complex with CH,I were examined to shed more light on the origin of the products. The reaction (eq. I), conducted neat and in tetrahydrofuransolution, pro[~S-C,H,Fe(CO),],SO,
+ CHJ + $-C,HsFe(CO)2S(0)1CH3
+ ~s-C,H,Fe(CO),I
ceeded at a reasonable rate upon heating to afford good yields of $-C,H,Fe(CO),I (54-56s) and much lower yields of $-CSH,Fe(C0)2S(0),CH, (21-26%). Thus it appears that [$-CSHSFe(C0)J2S02 is not the primary source of the S-sulfinato product formed by the al&+&ion of the solutions of Na’ [q5-CSHsFe(CO)J and SO, at low temperatures. Whether the anion [$-C,H,Fe(CO)$OJ is the principal precursor of the S-sulfinate cannot be stated with certainty. However, this may well be so for the following reasons. Reactions of CH,I with tetrahydrofuran solutions of Na’ [$-CSHsFe(CO),]and equimolar SO* yield very little, if any, [$-C5H,Fe(CO),],S0, when the solutions are allowed to warm to approximately room temperature. This indicates that CH,I quite effectively traps either [~5-C5H5Fe(CO),],S0, or a precursor thereof- The low temperatures employed in these reactions, along with considerations of reactivity of CHjI toward various iron carbonylsuifur dioxide complexes, both suggest that the trapped species is either [q5-C,H,Fe(CO),SOJ or one with similar expected chemical properties. The reaction of Na’
21.4 mmol over 80 mln at -78’C, stir 100 min nt -7S’C, wnrm f for 26 min
41.6 mmol over G,Gh at -7E°C, wnrm f for 2.G h 20 mm01 at -70 to -GO’C
20 mm01 st -7O’C
VI
VII
VIII
IX
21.1 mm01 of (CII3O)$$O2, stirr 22 h 100 mmol of CII3Br nt -70 to --GoOc, stir 22 I1 et -70 to -GO’C, stir B h nt -20 to -13Oc 20 mm01 of CeH.jCII2Cl nt -7occ, stir GO11at -70 to -43Oc
40,l mmol of CH31 nt -78’C, stir 105 h, warm for 3,S 11 20 mmol of CH$ at -7O’C, stirr 11 h nt -70 to -3O’C 48 mlnO1 Of p-CH$&&S0@~3, stir 21 I1
30 mm01 of CH$, 6th 12 h 32,l mmol of CH31, 6th 1G h
48 mm01 of CH31, stir 21 h
Addition of RX ’
lG9b ~~C~II~PC(CO)~S(O)~CH~C~II~; no IR evidcncc of r$C5115Fc(CO)2Cl
46% t75-C~I~~Pc(Co)~s(o)~CM~, iB% q5-c5Hs~e(c0)21 2% ~5-CSHsPe(CO)2S(O)2CH3, c11~-c5~15Pc(c0)212s02, [qs~C~H~Fe(CO)12(CO)S02 No SR evidence of ~~“-C~HSPC(CO)~S(O)~CH~; [~~~C~I~~FC(CO)~J~SO~,[~5-C~~I~Pe(CO)1~(CO)SO~ GO9iJ~5-C~I~~I~c(Co)~s(o)~CH3; no IR cvidcncc of $CSH#c(CO)2Br
469b t15-CSHSPe(CO)2S(0)2CI~~, 4% BQl~H~Pe(CO)21 18.4% $.CSH~F~(CO)~S(O)~CH~~ 26.1% ~~.CSH~FC(CO)~S(O)~CH~ ‘I, [~s~C~~I~Pe(CO)2]2S02 22.4% q5CgH5Fe(C0)2S(0)2CH3 g
Products ‘I ‘1 ’
__ __ _. .
--
._ -
___
_
__
. .
.-
_ _ . . -_ -_
-
_ __
--
’ From 10 mmol nf [7$C~H5lk(CO)212. ’ Followh~g “ndditlon of SO$‘. ’ [~5C~HsIQ(CO)2)2 wns obtnlncd in nll cxperirnents. ’ The formotion of SC~H$c(C0)21 wns not cxnminccl in cxpcrimcnts II, III, nut1 IV. ’ Other, minor products were nlso detected upon chromntogrnphy but were not fully charncterbcd. ‘) After the cooling bath hnd bccn removed, the rcnction flnslc wns mnintnhicd at room tcmpcruturc. g Possible losses sustnincd through coprccipitation with NaI.
V
20 mmol over 4 h at -78eC, stir 1 11at -7&l”c 20 mm01 at’-70’C
21.4 mm01 over 80 min nt -78’C, stir 100 miu at -78’C, warm r for 26 miu 28.4 mmol over 4 h at -7E°C,wnrm f for 1 11 41.6 mmol over 3 h ut -78’C, worm ‘for 0 h
Addition of SO2
IV
II III
I
mcnt
Experi-
REACTIONS OF Nn+ [~5~C5115P~(C0)2]- ’ WITH SOg-RX IN TETRAHYDROFURAN
TABLE 3
64
[$-C,H,Fe(CO),] with C’H,I to give q5-C5H,Fe(C0)&H,, followed by SO, insertion (eq, Z), a reasonable alternative to the above proposal, may be readily Na’ [qS-C$I,Fe(CO),] q5-C,H,Fe(CO),CH,
+ Cl-&I + $-C,H,Fe(CO)&H,
+ NaI
+ SO, + q5-C,H,Fe(CO),S(O),CH,
(2)
dismissed from the reported kinetic data 1231 and from the following additional experiments_ First, there is nc observable reaction between $-C5HSFe(CO),CH,C,H, and SO2 under the conditions that mirror those of Experiment IX in Table 3. Second, as reported previously [24], reaction of Na* [$-C,H,Fe(CO)J with SO, followed by BrCH2GCCH, yields qS-CSH,Fe(CO),S(0)#H,~CCH,, whereas q*-C,H,Fe(CO),CH,eCCH, and SO, afford q5-C,H,Fe(CO)&=C(CH,)S(O)OCH,. Third, the interaction of ClCH,CH=C(CH,), with a mixture of Na’ [$-CSHsFe(CO)J and SO, affords $-C5H,Fe(CO),S(0),CH,CH=C(CH,), exclusively, but q5-CsHsFe(C0)&H2CH=C(CH,), and SO2 yield the two isomers $-C,H,Fe(CO),S(0)&H,CH=C(CH,)2 and q5-CsH,Fe(~)2S(0)2C(CH,),CH= CH, [25]_ The formation of both qS-C5HSFe(C0)2S(0)2CH3 and q5-C5HSFe(CO)tI in the reactions under discussion may indicate that these products are derived in part from [$-C,H,Fe(CO),],SO, and CHJ. Alternatively however, the interaction between [q’-CSH,Fe(CO),SOJ ( or a species with similar expected reactivity) and CHsI may be a free radical one, affording both the iodo and S-sulfinato complexes. An earlier study [26] of the reaction of a tetrahydrofuran solution of Na’ ]q*-C,H,Fe(CO)J and SO, with optically active BrCH(CH&,H, * revealed complete loss of stereochemistry upon the formation of q5-C,H,Fe(CO),S(0)&H(CH,)C6H5. This would seem to indicati a free radical pathway, a mechanism consistent with the nature of the products obtained in the alkylation reactions described herein. Notwithstanding uncertainties in the identity of the reactive iron carbonylsulfur dioxide species, the solutions of Na’ [$-C,H,Fe(CO)J and SO2 serve as ?Iuseful reagent for the preparation of iron S-sulfinates that are inaccessible via the SO2 insertion reaction 124,251. Very likely they possess a wider synthetic utility, which, however, still remains to be explored. Sumlmary of reactions In conclusion, we wish to present a summary of reasonable pathways leading to the formation of various ironsulfur dioxide produck investigated in this work. These pathways are depicted in Scheme 1. Because of the complexity of the reaction system Na’ [q5-CSH,Fe(CO),]
and SQ, parts of the scheme are admittedly speculative_ Moreover, no attempt was made to present all possible reactions; only those thought to be essential m-the formation of various observed products are included. The identity cf Ghe oxidizing Bgent [0] is unknown; it may be SO*, as air was excluded from these solutions. The species $-CSHSFe(CO)zS02 may undergo loss of SO* by analogy
*
The erperimenhl
conditions
Na+ [?$CsHsFe
for this
reaction
were
similar
+ SO2 with ClCH2CH=C(CH&
to those employed f251.
for
the
reactionof
65 SCHEME
1
[+CSHSFe(CO),]-=
[$-CSHSFe(CO),SO,]-
q5-C,H,Fe(CO),
1 q5-C5H5Fe(C0)$302
co1
1
dimerize
dime&e 1
[$-C5H,Fe(CO),S0J2
I~5-GH5Fe(C%12 11
C~S-WWdC0M2~02 1
-CO
[$-C5H5Fe(CO)]z(CO)SO~ with the reported [27] lability of metal carbonyl radicals_ Coupling between the radicals $-CSH5Fe(C0)2 and $-C5H5Fe(C0)&102 would then account for the formation of [$-C,H,Fe(CO),],, [s’-C5H5Fe(CO),],SOl, and [$-C5H5Fe(C0)1‘SOJ2. The complex [$-C5H5Fe(CO)J2S02 does not arise directly from [q5C,H,Fe(CO),], and SO*, since we have shown that such an insertion reaction does not proceed at temperatures up to 25°C. However, it is worthy of note that reaction between [$-C5HsFe(CO)z]z and SO, at 40°C led to the isolation of a polynuclear (~5-C5H5)4Fe4(CO),(SO~)~ upon work-up [28] *_ Experimental Reactions were conducted in an atmosphere of nitrogen, which was also used routinely in the handling of organometallic compounds_ Florisil(60-100 mesh) and Ventron or Woelm alumina, deactivated with Hz0 (generally 6%), were employed in chromatographic separations and purifications_ Anhydrous grade SO2 was purified as described previously [243. Tetrahydrofuran (THF) was freshly distilled from CaH, or LiAlH, under nitrogen. All other chemicals
and solvents procured commercially were reagent grade or equivalent quality and were used without further purification. Melting points were obtained on a Thomas-Hoover capillary melting point apparatus and are uncorrected. Proton NMR spectra were taken on a Varian Associates A-60 or _4-60A spectrometer. Infrared (IR) spectra were recorded on a Pa&in-Elmer 337 or Beckman IR-9 spectrophotometer using polystyrene film for calibration. Mass spectra were recorded by Mr. CR. Weisenberger on
an A.E.I. Model MS-9 spectrometer at 70 eV. Molecular weights were measured on a Mechrolab Model 301-A vapor pressure osmometer in CHCls solution. Elemental analyses and some molecular weights were obtained by Galbraith Laboratories, Inc., Knoxville, Tenn., and Pascher Mikroanalytisches Laboratorium, Bonn, Germany. * the po&bfity that [q5-C5H.9e(CO)~3-$30~ ‘+ecovcred” [$-C5HSFe(CO).& cannot employed
in the work-up.
was formed in this reaction but decomposed to the be ruled out because of the rather high temper&-ares
66
Reactioza of Na’ [q5-C&T$&CO)J with SO2 A, THF-solution (120 ml) of Na’ [~5-CSH5Fe(CO),r, prepared from 1.77 g (5.0 mmol) of [q5-CSH,-Fe(CO),], and freed from excess sodium amalgam and mercury, was cooled to ca. -78k and treated with 0.96 g (15 mmol) of SOS dissolved in 20 ml of THF over a period of 10 min. The cooling bath was removed and the reaction mixture was allowed to warm to room temperature in 45-60 min. The solvent was evaporated in vacua at room temperature, the residue was dissolved in CHCIB, and the resulting solution was filtered through Florisil. The Florisil &as washed with acetone and the combined wash and filtrate were evaporated to dryness. The residue was dissolved in minimum CHC13 and chromatographed on a 2;7 X 25 cm column of Florisil. Chloroform eluted off a purple band containing [~5-C,H,Fe(CO),],, 10/l CHClJacetone removed a narrow red band of [~5-C5H,Fe(CO),(CO)S0,, and then acetone removed another red band of [q5-C,H,Fe(CO)],(CO)SO,, and then acetone removed another red dryness, the residue was dissolved in minimum CHC&, filtered, and the product was precipitated by the addition of per&me at 0°C. The yields of [q5-C,H,Fe(CO)],(CQ)SO* and [~5-C5H,-Fe(C0)2]zS02, dec. 142”C, were 0.04 (2%) and 0.4-0.6 g (29-30%), respectively. Physical and analytical data for these complexes are furnished in Table 1. Reaction between Na’ [n5-C,H,Fe(CO)J and SO, in THF was also carried out exactly as described above, but with a much larger, 7.0 g (110 mmol) amount of SO+. Chromatography on Florisil afforded a purple band containing [q5C,H,Fe(CO)I]z (0.36 g), which was eluted off with CHCIJ, an orange band ( E~5-C,H5Fe(CO),SO_], 2) removed with 5/l CHClJacetone, and a red band (Cr15-C5H~Fe(CO)211SO~)removed with acetone. The yields of [q5-C5H5Fe(CO),SO& and [$-C5H5Fe(CO),]zSOz were 0.40 (17%) and 0.14 g (7%), respectively. Reaction of Na’ [q5-CJT$e(CO)J with SO2 followed by CHJ A representative alkylation reaction of a mixture of Na’ [q5-CSH5Fe(CO)J and SOi is described below. A THF solution (150 ml) of Na’. [$-C5HsFe(CO)J, prepared from 3.54 g (10.0 mmolj of [q5-C5HsFe(C0),],_, was cooled to -78°C. Sulfur dioxide (0.94 ml of liquid, 21 mmol) was then passed into this solution in a stream of nitrogen over a period of 80 min. The resulting red reaction mixture was stirred at -7S”C for 100 min, allowed to warm for 25 min, treated with CHd (G.&g, 48 mmol) and stirred at room temperature under a Dry Ice-cooled condenser for 21 h. Filtration, solvent removal from the filtrate, and chromatography of the residue on alumina (6% H20) eluting with CHClJacetone led to the isolation of a mixture of [$-CSHsFe(CO),]-_ and q5-C5H5Fe(CO),I (0.80 g, 15 and 4%, respectively, by IR spectroscopy) and of $-CjH5Fe(CO)zS(0)&H3 (2.36 g, 46%). The insoluble solid from the reaction mixture was shown to be NaI (l-25 g)_ Several other alkylation reactions were carried out under analogous and somewhat modified experimental conditions, These conditions and the results are summarized in Table 3. The S-sulfinates ??5-C5H,Fe(CO),S(0)tR, all known compounds [29], were characterized by IR spectroscopy.
67
Reaction
of [q5-C$?~e(CO)J2SOz
with CHJ
A solution of 0.300 g (0.718 mmol) of [q5-CgH5Fe(CO)I!]tSO+ in 20 ml of CH,I in a sealed glass tube was maintained at SO-85°C for 3 h. The tube was cooled to room temperature and opened, the solvent was removed, and the residue was chromatographed on alumina to afford 0.245 g (56% yield) of qs&,H,Fe(CO),I and 0.096 g (26% yield) of $-CSHSFe(CO),S(0),CH,. When the same reaction between 0.230 g (0.550 mmol) of [qS-C,H,Fe(CO),],SO, and 3.0 ml (48 mmol) of CH,I was carried out in THF (20 ml) at reflux, 0.179 g (54% yield) of $-C,H,Fe(CO),I and 0.059 g (21% yield) of q5-C,H,Fewere isolated upon chromatography. There was no evidence of (CC),S(G)&H,
CrlS-WWdCOM,.
Acknowledgements We gratefully acknowledge support of this work by the National Science Foundation (Grant No. CHE76-02413 AOl) and the North Atlantic Treaty Organization (Grant No. 604 with Professor M. Graziani). P.R.-R. thanks The Ohio State University Graduate School for a Postdoctoral Fellowship. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
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68 34
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35 W:StrohuMer 36
W_ hohmeier,
37
Ii: Ciainkr.
6 (1967)
5080.
:-
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and J.F.~Gutt&nbergei, Chem. Be+ 97 (1964) I&, h POPS and J,F_ G; ttklbekm. cherir Ber.,?S (1966) J. Anier. &em. Sdc; 39 (iSi57, i5377.
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