Orgatlometallics 1996,14, 387-400
387
Radical Processes in the Reduction of Nitrobenzene Promoted by Iron Carbonyl Clusters. X-ray Crystal Structures of [Fe3(CO)&3-NPh)12-,[HFe3(CO)g@3-NPh)l-, and the Radical Anion [Fe3(CO)111-* Fabio Ragaini,?Jeong-Sup Song, David L. Ramage, and Gregory L. Geoffrey" Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
Glenn A. P. Yap and Arnold L. Rheingold Department of Chemistry, University of Delaware, Newark, Delaware 19716 Received July 20, 1994@
The halides C1-, Br-, and I- and the pseudo-halide NCO- react with Fe3(C0)12(1)in aprotic solvents to induce a disproportionation reaction yielding the radical anion [Fe3(C0)11]-' (3). This species has been h l l y characterized by single-crystal X-ray diffraction studies of its PPL+and PPN+ salts, although the latter was disordered. Crystal data for PPh4.3: C35H20Fe3011P, monoclinic, P21/n, a = 11.313(2),b = 12.966(3),and c = 23.6826) B = 91.380(9)", V = 3472.8(9) A3, 2 = 4, RQ = 6.73%. In contrast to other related Fe3 carbonyl clusters, the structures show that the anion has one semibridging CO and ten terminal CO ligands. Cluster 3 also forms upon reaction of [Fe3(C0)11I2- with ArN02, and it disproportionates under a CO atmosphere to yield Fe(C0)5 and [Fe3(C0)11I2-. The mixed-metal cluster FezRu(C0)lp also reacts with [PPNICl to yield [PPN][Fe2Ru(Cl)(c0)10],a reaction which is similar to that previously observed for RUB(CO)~P. Reaction of [Fe3(CO)111-*with PhNO and PhN02 yields a mixture of clusters which, after workup, gives azo- and azoxybenzene. When c15c6NO2 was used in place of PhN02, the cluster [Fe3(C0)9013-NC6C15)]2-(5) was obtained together with other products. Cluster 5 can be protonated by HBF4 to yield [HFe3(CO)gOc3-NC6Cl5)](6). The non-chlorinated analogue of 5, [PPL12[Fe3(C0)&3-NPh)3'2CH2C12 (PPh4*8*2CH2Clz), has been characterized by an X-ray diffraction study. Crystal data for PPh&2CHzClz: P21, a = 13.065(3), b = 18.114(4), and c = 13.618(3) /3 = 98.93(2)", 2 = 2, R(F) = 6.94%, R(wF') = 7.30%. The cluster [HFe3(CO)111- (2) has been found to react with PhNO and ArN02 by a n initial electron-transfer process to form [HFe3(CO)g@3-NPh)l-(71, with PhNO giving higher yields. This species has been crystallographically characterized as its PPN+ salt: Crystal data for PPN-7: P21/c, a = 15.03(3), b = 21.22(3), and c = 16.12(3) p = 106.71(2)",2 = 4, R(F) = 10.05%, R(wF) = 11.34%. Cluster 7 reacts with PhNO in the presence of radical activators to yield azo- and azoxybenzene. The use of 2-Me-C6H4NO in this reaction gave only symmetrical azo- and azoxyarenes, implying that these products do not derive from a coupling of the imido fragment in 7 with free ArNO. Cluster 7 reacts with water to yield aniline in the presence of [Cp2Fe][PF,j] but not in its absence. Competition experiments show that 7 is not a kinetically significant intermediate in the phase-transfercatalyzed reduction of ArN02 by Fe3(C0)12 and imply that radical intermediates are also involved in this reaction.
A,
A,
A,
Introduction Reduction and carbonylation of organic nitro compounds are reactions of significant potential synthetic and industrial interest, since many products can be obtained from nitro compounds and CO in a single step, including amines, amides, oximes, ureas, carbamates, isocyanates, and indo1es.l Many different complexes
have been reported to promote or to catalyze reduction and carbonylation of nitro compounds, with the most efficient metals being palladium, rhodium, and ruthenium. Only limited attention has been given to the study of iron complexes as promoters for these reaction^.^-^ Several iron compounds are known t o promote the but - ~few stoichiometric reduction of nitro c o m p o ~ n d s , ~
~~
+ On leave from the Dipartimento di Chimica Inorganica, Metallorganica e Analitica and CNFt Center, Milano, Italy. e Abstract published in Advance ACS Abstracts, December 1,1994. (1) Cenini, S.;Pizzotti, M.; Crotti, C. Metal Catalyzed Deoxygenation Reactions by Carbon Monoxide of Nitroso and Nitro Compounds. In Aspects ofHomgeneous Catalysis; Ugo, R., Ed.;D. Reidel: Dordrecht, The Netherlands, 1988 Vol. 6; pp 97-198.
(2) (a) des Abbayes, H.; Alper, H. J.Am. Chem. SOC.1977, 99,98. Gopal, M. J.Chem. SOC.,Chem. Commun. 1980,821. (c) (b)Alper, H.; Alper, H.; Paik, H.-N. NOULJ. J.Chim. 1978,2,245. (d)Alper, H.;Des Roches, D.; des Abbayes, H. Angew. Chem., Znt. Ed. Engl. 1977, 16, 41. (3)NGuini Effa, J.-B.; Djebailli, B.; Lieto, J.; Aune, J.-P. J. Chem. SOC.,Chem. Commun. 1983,408.
0276-733319512314-0387$09.OOIO 0 1995 American Chemical Society
Ragaini et al.
388 Organometallics, Vol. 14, No. 1, 1995
catalytic processes have been r e p ~ r t e d .Despite ~ the apparent lower efficiency of iron-based catalysts, their use is of interest due to the comparative cost advantage of iron compared to the other metals commonly employed as catalysts for these reactions. Since little is known about the mechanism by which nitro and nitroso compounds react with iron carbonyls, we have initiated an investigation in this area, using Fe3(C0)12 (1) and [HFe3(CO)111- (2) as starting compounds. As alkylammonium halides have been shown to be efficient cocatalysts in the related Ru3(CO)12-catalyzedcarbonylation of nitrobenzene,6 we have also investigated the reactivity of Fe3(C0)12 with [PPNIX salts (X = C1-, Br-, I-, NCO-; PPN+ = (PPh&N+). As described herein, this has led to the isolation of the radical anion cluster [Fe3(CO)111-*(3) as PPN+ or PPh4+ salts, both of which have been crystallographically characterized. The full characterization of [Fe3(CO)111-' is of significance in itself, since numerous studies in recent years have demonstrated the importance of free-radical processes in organometallic chemistry, including a number of catalytic reactions known or proposed to involve radical intermediate^.^ However, few of these intermediates have been definitively characterized, and because of their elusive nature it has seldom proven possible to conduct detailed investigations of their chemical behavior. One of the radical anions that has been invoked in a number of reactions is [Fe3(CO)111-'. This cluster radical anion has been observed during the reaction of Fe3(C0)12with nitro- and nitrosoparaffins under conditions similar to those used for Fe3(CO)l~-catalyzed carbonylation of these reagenk8 The anion [Fe3(CO)111-' has also been invoked as a key intermediate in the electron-transfer-catalyzed substitution reactions of Fe3(CO)12.9J0 This anion has been claimed to form in a number of ways, including reduction of Fe(C015 and Fe3( C O ) I ~ , oxidation ~ ~ J ~ of the anion [Fe3(C0)11I2- (4),11 electron transfer between Fe3(C0)12and [Fe3(C0)111~-,~~ disproportionation of Fe3(C0)12induced by strong bases ~~~~~
~~
~~
(4) (a) Landesberg, J. M.; Katz, L.; Olsen, C. J . Org. Chem. 1972, 37, 930. (b) Boldrini, G. P.; Umani-Ronchi, A,; Panunzio, M. J. Organomet. Chem. 1979, 171, 85. (5)(a) Knifton, J. F. J . Org. Chem. 1976, 41, 1200. (b) C a m , K.; Cole, T.; Slegeir, W.; Pettit, R. J . Am. Chem. SOC.1978,100, 3969. (c) Alper, H.; Hashem, K. E. J . Am. Chem. SOC.1981, 103, 6514. (d) Kmiecik, J. E. J . Org. Chem. 1966, 30, 2014.
(6) (a) Cenini, S.; Crotti, C.; Pizzotti, M.; Porta, F. J. Org. Chem.
1988,53,1243. (b) Han, S.-H.; Song, J.-S.; Macklin, P. D.; Nguyen, S. T.; Geoffroy, G. L.; Rheingold, A. L. Organometallics 1989, 8, 2127. (7) (a) Chanon, M., Julliard, M., Poite, J . C., Eds. Paramagnetic
Organometallic Species in ActiuationlSelectiuity, Catalysis; NATO AS1 Series C257; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1989. (b) Trogler, W. C., Ed. Organometallic Radical Processes; Journal of Organometallic Chemistry Library 22; Elsevier: Amsterdam, 1990. (c) Chanon, M. ACC.Chem.Res. 1987,20,214. (d) Julliard, M.; Chanon, M. Chem. Reu. 1983,83,425. (e) Tyler, D. F. Prog. Inorg. Chem. 1988,36, 125. (8) Belousov, Yu. A.; Kolosova, T. A. Polyhedron 1987, 6, 1959. (9) Bruce, M. I.; Hambley, T. W.; Nicholson, B. K.J . Chem. SOC., Dalton Trans. 1983, 2385. Yang, S.-R.; Li, C.-S.; Duan, J.-P.; Cheng, C.-H. J. (10) Luo, F.-H.; Chem. SOC.,Dalton Trans. 1991, 2435. (11)(a)Krusic, P. J. Int. Conf. EPR Spectrosc. 1978. (b) Krusic, P. J.; San Filippo, J., Jr.; Hutchinson, B.; Hance, R. L.; Daniels, L. M. J. Am. Chem. SOC.1981, 103, 2129. (c) Morton, J. R.; Preston, K. F.; Charland, J.-P.; Krusic, P. J. J . Mol. Struct. 1990,223, 115. (12) Dawson, P. A.; Peake, B. M.; Robinson, B. H.; Simpson, J. Inorg. Chem. 1980,19, 465. (13) (a) Chini, P. J . Organomet. Chem. 1980,200, 37. (b) Furuya, F. R.; Gladfelter, W. L. J . Chem. SOC.,Chem. Commun. 1986, 129.
and basic solvents such as DMF,l4-I6and 6oCoradiolysis of Fe3(C0)12 and [HFes(CO)111-.11cJ7 Although it appears to have been isolated on two o c c a ~ i o n sit , ~has ~ only been characterized by its EPR datal1 and even that has been disputed.12 The isolation and characterization of [Fes(CO)111-' should now make possible detailed explorations of the mechanistic and reaction chemistry of this important species. In this paper, we also report the results of an investigation of the reactivity of [Fe3(CO)111-*with nitro and nitroso organic compounds. Part of the results reported herein have been previously communicated in a preliminary form.18 Results and Discussion
Synthesis of [Fes(CO)111-' (3). Alkylammonium halides are known to strongly enhance the activity of Ru3(C0)12 as catalyst for the carbonylation of nitro organic compounds to the corresponding carbamates.6a Although the reactions of halides with Ru3(C0)12 are now well u n d e r s t o ~ d , the ' ~ ~corresponding ~~ reactivity of Fe3(C0)12 (1)with halides has not been well developed.21 We have found that [Ph4PlC1 and the [PPNl+ salts of C1-, Br-, I-, and NCO- react with 1 to induce a disproportionation reaction to form the radical anion [Fe3(CO)111-* (31,Fe(C0)5, and FeX, salts as principal products, eg., eq 1. Trace amounts of other anionic
0 C.
..*/,Fe(CO)r
(C0)3Fe"Fe(C0)3
1PPN+ +
Fe(CO)5 + FeCI2 (1)
clusters have also been observed, among which the most (14) Babain, V. N.; Belousov, Yu. A.; Gumenyuk, V. V.; Salimov, R. M.; Materikova, R. B.; Kochetkova, N. S. J . Organomet. Chem. 1983, 241, C41.
(15)Yang, S. L.; Li, C. S.; Cheng, C. H. J . Chem. SOC.,Chem. Commun. 1987,1872. (16) Other studies in these laboratories have shown that phosphinimines, RsP-NR', efficiently induce disproportionation of Fe3(C0)12to form [Fe3(CO)111-' as the [R3P-NHRl+ salt: Nguyen, S. T.; Mirkin, C. A.; Ragaini, F.; Geofioy, G. L. Unpublished results. (17)Peake, B. M.; Symons, M. C. R.; Wyatt, J. L. J . Chem. SOC., Dalton Trans. 1983, 1171. (18) Ragaini, F.; Ramage, D. L.; Song, J.-S.; Geoffroy, G. L.; Rheingold, A. L. J . Am. Chem. SOC.1993, 115, 12183. (19) (a) Han, S.-H.; Geoffroy, G. L.; Dombeck, B. D.; Rheingold, A. L. Inorg. Chem. 1988,27,4355. (b) Lavigne, G.; Kaesz, H. D. J . Am. Chem. SOC.1984, 106,4647. (c) Lavigne, G.; Lugan, N.; Bonnet, J.-J. Inorg. Chem. 1987,26,2345. (d) Rivomanana, S.; Lavigne, G.; Lugan, N.; Bonnet, J.-J. Organometallics 1991, 10, 2285. (e) Lavigne, G.; Lugan, N.; Kalck, P.; Soulib, J. M.; Lerouge, 0.;Saillard, J. Y.; Halet, J. F. J . Am. Chem. SOC.1992, 114, 10669. (0 Cenini, S.; Pizzotti, M.; Crotti, C.; Ragaini, F.; Porta, F. J . Mol. Catal. 1988,49, 59. (9) ChinChoy, T.; Harrison, W. T. A,; Stucky, G. D.; Keder, N.; Ford, P. C. Inorg. Chem. 1989,28, 2028. (h) Lillis, J.;Rokicki, A.; Chin, T.; Ford, P. C. Inorg. Chem. 1993,32, 5040. (20) For recent reviews, see: (a) Ford, P. C.; Rokicki, A. Adu. Organomet. Chem. 1988, 28, 139. (b) Lavigne, G.; Kaesz, H. D. In Metal Clusters in Catalysis; Gates, B., Guczi, L., KnBzinger, H., Eds.; Elsevier: Amsterdam, 1986; Chapter 4, pp 43-88. (c) Lavigne, G. In The Chemistry ofMetal Cluster Complexes; Shriver, D., Adams, R. D., Kaesz, H. D., Eds.; VCH: New York, 1990; Chapter 5, pp 201-303. (21) In ref 19a, it was noted that Fes(C0)12 reacted with [PPNII in refluxing THF to form [PPNI[HFe3(CO)111and [PPNI[Fe(C0)4Il! but the presence of 5-10% MeOH in commercial Fe3(C0)12 is likely responsible for those results which differ from those reported herein.
Reduction of Nitrobenzene Promoted by Clusters
Organometallics, Vol. 14, No. I, 1995 389
the formation of a complex from which the halide ligand abundant was [PPN]~[Fe4(C0)131.~~ These disproporcan be displaced by CO to re-form Fe3(C0)12. From the tionation reactions occur in thoroughly dried THF, CHzreactivity data and by analogy with the corresponding Clz, and Et20 solvents, with the latter found t o be best reactions of R U ~ ( C O ) this ~ Z complex , ~ ~ ~ ~is~likely to be for isolation of the product, since all other byproducts [Fe3(X)(C0)11]-(X= C1, Br, I, NCO). The presence of a are insoluble in this solvent except for Fe(C0)5, which larger amount of CO (1 atm) induced different reactivity, is easily removed by evaporation. The reaction with as described below. [PPNICl is much faster in THF (-10 min) than in Et20 (-1.5 h), which is likely due to the limited solubility of The [PPNl+ and [PPh4]+ salts of the radical anion [PPNICl in the latter solvent. The reactions with [Fe3(CO)111-' (3)are stable in the crystalline state under [PPNlBr and [PPNII were slower than the correspondNz for several days, but THF solutions decompose over ing reaction with [PPNICl when run in THF (-30 and the course of 1-2 days to yield [PPNI[HFe3(C0)113 75 min, respectively) but proceeded at comparable rates ( P P N O ~ Fe(C0)5, ),~~ and [PPNl~[Fe~(C0)~~1.22~27 The in EtzO. The lower nucleophilicity of Br- and I- in anion 2 likely forms via hydrogen atom abstraction from nonprotic solvents like THF or ether, with respect to THF, a conclusion supported by the observation that its C1-, it most likely compensated in this case by the formation was completely suppressed when [Fe3(CO)111-' higher solubility of the corresponding PPN salts. The was allowed t o decompose in benzene solution, whereas yie2ds for the reactions in Et20 were comparable for all the two other products were still formed. the anions and were near 50% in each case (see Addition of CO (1 atm) to solutions of [Fe3(CO)111-' Experimental Section). induced its immediate disproportionationto form mainly The residue from the reaction of Fe3(C0)1~ with [PPNIFe(C0)5 and [Fe3(C0)11lZ-(4Xz8 The same two products NCO, after extraction with THF, was shown to contain were also obtained when Fe3(C0)12was allowed to react the [PPNl+ salt of the knownz3 anion [Fe(NC0)4]- by with halides under a CO atm, although the intermediate comparison of its IR spectra (Nujol mull, VNCO = 2189 formation of [Fe3(CO)111-' was not directly observed in cm-l; MeNOz, y ~ c o = 2195 cm-l) to those reportedz3and this latter reaction. The disappearance of Fe3(C0)12was by the presence of a molecular ion for the anion a t M-3 times faster when the halide reactions were per= 224 in its negative ionization FAB mass spectrum. formed under a CO atm. This rate acceleration conThe identification of FeClz in the residue from the trasts with the inhibition of the reaction by low amounts reaction of Fe3(C0)12with [PPNICl was less certain, but of CO and suggests the involvement of an autocatalytic the presence of a shoulder at 494 cm-l on the 499 cm-l reaction in which the initially formed radical anion 3 [PPNl+ peak in the KBr IR spectrum of the tan residue reacts with CO to yield radical species of lower nuclecompares to the 493.2 cm-l band reported for F e c l ~ . ~ ~arity which readily transfer an electron either to Fe3This shoulder is not observed in the KBr IR spectrum (CO)lz, regenerating 3, or t o another molecule of 3, of pure [PPNICl. generating [Fe3(C0)11]2-.29The first possibility should By running the disproportionation reaction under be most favored until almost all of the starting FedC0)lz various solvent and concentration conditions, we obhas been consumed, and under a CO atm only a small served an inhibiting effect by small amounts of CO, such amount of halide is needed to initiate an autocatalytic as those which are formed during the reaction itself. reaction which eventually consumes all of the starting This effect was only observed when the reaction was cluster. run in Et20 with a high concentration of the reagents The EPR signal obtained from [PPNI[Fe3(CO)111, (1 g of Fe3(C0)12 in 100 mL of EtzO) and was particu(PPN-3)(g(THF, -78 "C) = 2.0489) compares well with larly evident when [PPhdCl was used. Under these data previously reported for radical anion [Fe3(C0)111-'.~~ conditions, the reaction stopped completely after conIn its IR spectrum, 3 shows only terminal carbonyl sumption of about half of the reagents, but it could be bands [vco(THF) = 2057 (vw),2017 (w), 1984 (vs), 1966 started again by bubbling nitrogen through the solution. (ms), 1933 (mw), 1922 (w, sh) cm-ll, and the spectrum Under the same conditions, but using [PPNICl instead is identical to the spectra produced upon reacting of [PPh41C1, the reaction only slowed, taking several together equimolar amounts of CPPNIdFe3(CO)111 and hours to reach completion, but it did not completely stop. Fe3(C0)12 and upon oxidation of [Fe3(C0)11lZ-,routes Even in this case, however, it was possible to apwhich have been used previously to prepare 3.11J3The preciably increase the rate of the reaction by bubbling absence of an IR band in the region characteristic of nitrogen through the solution at regular intervals of bridging CO's is in accord with the solid state structure time.25 This effect was not noted when the reaction was described below which shows 10 terminal carbonyls and conducted in THF or CH2C12, which is likely due to the 1 weakly semibridging CO (see Figure 1). higher solubility of the alkylammonium salts in these solvents. Although our data are not sufficient to (26) (a) Dahl, L. F.; Blount, J. F. Inorg. Chem. 1966, 4, 1373. (b) Hodali, H. A.; Arcus, C.; Shriver, D. F. Inorg. Synth. 1980,20, 218. indicate a specific mechanism for the formation of (27)Although no other product was observed by IR, some non[Fe3(CO)11]-*,it is clear from the CO inhibiting effect carbonyl compound is probably formed, since additional CO is necesthat one of the earliest stages of the reaction must be s a r y to complete the disproportionationof [Fe3(CO)111-' into Fe(C0)6 ~~
(22) Whitmire, K.; Ross, J.; Cooper, C. B.,III; Schriver, D. F. Inorg. Synth. 1982,21, 66. (23) Forster, D.; Goodgame, D. M. L. J . Chem. SOC.1965, 262. (24) Jacox, M. E.; Milligan, D. E. J . Chem. Phys. 1969,51,4143. (25) Continuous bubbling of Nz through the solution during the entire reaction led to irreproducible results, since much of the Et20 solvent evaporated under these conditions and had to be readded periodically. Also, evaporation of the solvent caused a marked decrease in the temperature of the solution. This inhibiting effect by CO was also clearly observed when the weak base R 3 P - m ' was used to induce the disproportionationof Fe3(COhz (see ref 16).
and [Fe4(CO)ls12-. (28) (a) Lo, F. Y.-K; Longoni, G.; Chini, P.; Lower, L. D.; Dahl, L. F. J . Am. Chem. SOC.1980,102, 7691. (b) Hodali, H. A,; Shriver, D. F. Inorg. Synth. 1980,20, 222. (29)(a) For related reactions see refs 9, 10, and 15. In ref 15, reaction of Fe3(C0)12 with CO to yield Fe(C0h was reported to be catalyzed by an electron-transfer path and [Fe3(CO)111-* was detected by EPR, along with [Fe3(CO)lzl-*and [Fez(CO)&*. (b) [Fe3(CO);iI-' can be uroduced uuon reductlon of Fes(C0)lz in the absence o f C 0 since under h e s e condi6ons insufficient CO is released in the transformation of [Fe3(C0)1&*into [Fe3(CO)d-' to induce further fragmentation of the latter species.
390 Organometallics, Vol. 14,No. 1, 1995
Ragaini et al.
z0‘5’
PPh4.3
Figure 1. ORTEP drawing of [PPhJFe3(C0)113 (PPh4.3) with thermal ellipsoids drawn at the 30% probability level. X-ray Crystal Structure of [PPh41[Fes(CO)111. Despite the high reactivity of [Fe3(CO)111-’, X-rayquality crystals of its [PPNI+ and [PPh41+ salts were obtained by slow diffusion of pentane into -70 “C Et20 solutions of the salts. Both salts were characterized by X-ray diffraction studies, although the [PPNl+ salt was disordered and produced a lower quality structure (see supplementary material). An ORTEP drawing of the [Fe3(CO)111-* anion in the [Ph4Pl+ salt is shown in Figure 1,and the relevant crystallographic data are set out in Tables 1and 2. Unlike the related Fe3 carbonyl clusters Fe3(C0)12,~O [Fe3(C0)1112-,28and [HFe3(C0)111- 26 which display 2-fold symmetry and have bridging CO’s, [Fe3(CO)111-*is without symmetry and possesses only a very weakly semibridging CO. The semibridged Fe(1)-Fe(3) bond distance of 2.503(2) A is significantly shorter than the Fe(l)-Fe(2) and Fe(2)-Fe(3) distances, which are more typical of Fe-Fe single bond values.30 The CO groups at Fe(2) are arranged in the expected axial ( 5 , 6) and equatorial (7, 8) arrangements. However, the presence of the unsymmetrical bridge has caused a tilting of CO(1) away from an axial position toward Fe(3), while the nearly equatorial plane for CO(2) and CO(3) is twisted so as t o bring CO(1) closer and CO(4) further from Fe(3). The geometry at Fe(3) is roughly trigonal bipyramidal. The absence of a full bridging CO ligand was unexpected. It is generally considered that an increase in the negative charge on a cluster leads to an increased tendency for carbonyl ligands to display a bridging coordination mode. However, in the structure of [Fe3(CO)111-’ the opposite trend is observed with respect to Fe3(C0)12, which, a t least in the solid state, has two bridging carbonyl ligands. It is to be noted that the “normal” tendency is again observed with the dianion [Fe3(C0)11I2-,which has two bridging and one semibridging CO ligands. Overall, the determined structure is in excellent agreement with that proposed on the basis of a singlecrystal EPR study of PPN.3 doped into crystals of [PPNI[ H F ~ ~ ( C O ) Iwhich, I I , ~ ~along ~ with EPR studies of 57Feenriched 3, led to the conclusion that the unpaired electron was localized on a single iron atom.ll This is a remarkable feature since unpaired spin density is usually considered to be quite delocalized over several ~
~
~~~~~
(30) (a) Cotton,F. A.; b u p , J. M. J.Am. Chem. SOC.1974,96,4155. (b) Braga, D.; Fanugia, L:; Grepioni, F.; Johnson, B. F. G. J. Organomet. Chem. 1994,464, C39.
PPN.7
PPh4.8.2CHzC12
(a) Crystal Parameters formula C~sH2oFe3011P C S I H ~ ~ F ~ ~ N ZC6dbC@e3N09Pz O~PZ fw 815.0 1050.3 1247.64 cryst sys monoclinic monoclinic monoclinic space group P2l/n P2,k p21 a, A 11.313(2) 15.03(3) 13.065(3) b, A 12.966(3) 21.22(3) 18.114(4) C, A 23.682(5) 16.12(3) 13.618(3) B. deg 9 1.380(9) 106.71(2) 98.93(2) v,A3 3472.8(9) 4922(15) 3184(1) Z 4 4 2 D(calcd) 1.559 1.417 1.301 p(Mo Ka),cm-l 13.42 9.94 5.10 temp, K 213 296 295 size, mm 0.12 x 0.32 x 0.58 0.10 x 0.20 x 0.40 0.30 x 0.34 x 0.36 color burgundy red deep red T(max)/T(min) 1.21 1.10 1.16 diffractometer monochromator wavelength, A radiation scan method scan limits, deg data collected (h,k,D rflnscollcd indpdt rflns obs rflns (F. 2 nu(FJ) std rtlns
var in stds, % R(F), % R(wF), % GOF hlu(max) A@), NJNv
(b) Data Collection Siemens R3mN Siemens R3mN graphite 0.710 73 Mo Ka
Nicolet P3
w
4-55 &14,+16,+30
4-45 f16,+22,+17
4-45 f15,+20,+15
8537 7974 3410 ( n = 5 )
6687 6419 2791 ( n = 4)
4865 4298 3133 (n = 4)
1-2
3 stdl97 rflns 1-2
