Chiral-at-Metal Compounds [CpFe(Prophos)L] - ACS Publications

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Organometallics 2011, 30, 414–421 DOI: 10.1021/om100276t

Chiral-at-Metal Compounds [CpFe(Prophos)L] (L = Cl, I, CN), [CpFe(Prophos)CO]X (X = I, PF6), and [IndFe(Prophos)CO]I Henri Brunner,*,† Hayato Ike,‡ Manfred Muschiol,† Takashi Tsuno,*,‡ Naohisa Umegaki,‡ and Manfred Zabel†,§ †

Institut f€ ur Anorganische Chemie, Universit€ at Regensburg, 93040 Regensburg, Germany, and Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Chiba 275-8575, Japan. § X-ray structure analyses.

‡

Received April 6, 2010

The compounds [CpFe(Prophos)Cl] and [CpFe(Prophos)I] were prepared in photochemical reactions of [CpFe(CO)2Cl] and [CpFe(CO)2I] with (R)-Prophos. They consist of pairs of RFe,RC and SFe,RC diastereomers which only differ in the configuration at the metal atom. The diastereomerically pure compounds (SFe,RC)-[CpFe(Prophos)Cl] and (RFe,RC)-[CpFe(Prophos)I], which have the same relative configurations, were isolated. They epimerize via change of the Fe configuration and approach the equilibria (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)Cl] = 5/95 and (RFe,RC)-/ (SFe,RC)-[CpFe(Prophos)I] = 95/5 in first-order reactions with half-lives of 43 min at 20 C and 50 min at 50 C in C6D6, respectively. The reaction of (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)I] = 95/5 with KCN afforded the cyano complex [CpFe(Prophos)CN] in the diastereomer ratio RFe,RC/SFe, RC = 50/50. Both diastereomers (RFe,RC)- and (SFe,RC)-[CpFe(Prophos)CN] could be isolated diastereomerically pure. The compounds (RFe,RC)- and (SFe,RC)-[CpFe(Prophos)CN] are configurationally stable at the metal center. There is no diastereomer interconversion, not even at higher temperatures. The carbonyl complexes [CpFe(Prophos)CO]I, [CpFe(Prophos)CO]PF6, and [IndFe(Prophos)CO]I were prepared in thermal reactions of [CpFe(CO)2I] and [IndFe(CO2)I] with (R)Prophos or in an autoclave reaction of [CpFe(Prophos)I]/NH4PF6 with CO under pressure. All the carbonyl complexes are configurationally stable at the metal center. Seven diastereomers were characterized by X-ray crystallography. Including the two diastereomers (RFe,RC)-[CpRu(Prophos)Br] and (RFe,RC)-[CpRu(Prophos)I], a conformational analysis of the M-Prophos chelate ring was carried out, resulting in characteristic differences between major and minor diastereomers.

Introduction In the mid-1980s the RRu,RC and SRu,RC diastereomers of [CpRu(Prophos)Cl], containing the well-known ligand (R)Prophos (=(R)-1,2-bis(diphenylphosphanyl)propane),1 were separated and characterized.2-4 Both diastereomers, which only differ in the metal configuration, were extensively used as starting materials for the preparation of the derivatives (RRu,RC)- and (SRu,RC)-[CpRu(Prophos)X], claimed to occur with retention of configuration at the Ru atom.4 However, recent studies showed that (RRu,RC)- and (SRu,RC)[CpRu(Prophos)Cl] are not configurationally stable at the metal atom.5 Halide exchange and epimerization reactions *To whom correspondence should be addressed. H.B.: fax, þ49-9419434439; e-mail, [email protected]. T.T.: fax, þ81-47-474-2579; e-mail, [email protected]. (1) Fryzuk, M. D.; Bosnich, B. J. Am. Chem. Soc. 1977, 99, 6262– 6267. (2) Consiglio, G.; Morandini, F.; Bangerter, F. Inorg. Chem. 1982, 21, 455–457. (3) Morandini, F.; Consiglio, G.; Straub, B.; Ciani, G.; Sironi, A. J. Chem. Soc., Dalton Trans. 1983, 2293–2298. (4) Consiglio, G.; Morandini, F. Chem. Rev. 1987, 87, 761–778. (5) Brunner, H.; Muschiol, M.; Tsuno, T.; Takahashi, T.; Zabel, M. Organometallics 2008, 27, 3514–3525. pubs.acs.org/Organometallics

Published on Web 01/20/2011

proved that in the rate-determining step the Ru-Cl bond is broken to give the pyramidal 16-electron intermediates (RRu,RC)- and (SRu,RC)-[CpRu(Prophos)]þ, which keep their metal configuration. In competition reactions nucleophiles X may fill the vacant site in (RRu,RC)- and (SRu,RC)-[CpRu(Prophos)]þ to afford the substitution products (RRu,RC)and (SRu,RC)-[CpRu(Prophos)X] with retention of the metal configuration or pyramidal inversion of (RRu,RC)- and (SRu, RC)-[CpRu(Prophos)]þ may serve the side with the opposite metal configuration. A basilica-type energy profile implies that Cl/X substitution is faster than pyramidal inversion.5 (RRu,RC)- and (SRu,RC)-[CpFe(Prophos)Cl], the higher homologues of (RRu,RC)- and (SRu,RC)-[CpRu(Prophos)Cl], and related compounds were unknown. We were interested in synthesizing these compounds, studying their stereochemistry, and comparing the results of the Fe system with those of the corresponding Ru system.

Synthesis and Characterization of (RFe,RC)-/(SFe,RC)[CpFe(Prophos)Cl] and (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)I] (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)Cl] and (RFe,RC)-/ (SFe,RC)-[CpFe(Prophos)I] (Scheme 1) were synthesized by r 2011 American Chemical Society

Article Scheme 1. (SFe,RC)-/(RFe,RC)-[CpFe(Prophos)Cl] and (RFe, RC)-/(SFe,RC)-[CpFe(Prophos)I]

starting from [CpFe(CO)2Cl] and [CpFe(CO)2I], following a procedure reported for the conversion of [CpFe(CO)2Cl] to [CpFe(Diphos)Cl] (Diphos = 1,2-bis(diphenylphosphanyl)ethane).6 [CpFe(CO)2Cl] and (R)-Prophos were dissolved in toluene and irradiated with a mercury lamp at room temperature. [CpFe(Prophos)Cl] was isolated in 53% yield as black crystals which gave a black-violet solution in organic solvents. During irradiation an insoluble black precipitate had formed which had to be separated, reducing the yield. Such a precipitate did not form in the reaction of [CpFe(CO)2I] with (R)-Prophos. [CpFe(Prophos)I] was isolated in 83% yield. Under N2 protection the blue-violet band of [CpFe(Prophos)I] in THF migrated rapidly in chromatography on a silica column without decomposition. In our hands the best entry into the chemistry of the compounds [CpFe(Prophos)X] is via the synthesis of [CpFe(Prophos)I]. [CpFe(Prophos)I] did not change its violet color in toluene or THF solution on standing in air for minutes. After hours the violet solutions turned yellow. Short contact with air markedly affected the 1H and 31P NMR spectra of [CpFe(Prophos)I] (Figure 1S, Supporting Information), which broadened extremely. On addition of Cp2Co the signals became sharp. The reason is that oxygen in the air oxidizes some [CpFe(Prophos)I] to the radical cation [CpFe(Prophos)I]þ. Obviously, the paramagnetic 17-electron species [CpFe(Prophos)I]þ undergoes fast self-exchange with the neutral 18-electron species [CpFe(Prophos)I], which broadens the NMR spectra. Similar phenomena have been observed for [(C7H7)Mo(Prophos)Cl]7 and [CpRu(Prophos)Cl].5 Actually, compounds [CpFe(Diphos)Hal]þX- are stable and can be isolated.8 To get good NMR spectra, the addition of the strongly reducing agent Cp2Co has proven beneficial.5,7,9 Therefore, all the NMR spectra of [CpFe(Prophos)I] were measured in the presence of a small amount of Cp2Co. The air sensitivity of [CpFe(Prophos)Cl] (Figure 2S, Supporting Information) is much higher than that of [CpFe(Prophos)I]. (6) King, R. B.; Houk, L. W.; Pannell, K. H. Inorg. Chem. 1969, 8, 1042–1048. (7) Disley, S. P. M.; Grime, R. W.; McInnes, E. J. L.; Spencer, D. M.; Swainston, N.; Whiteley, M. W. J. Organomet. Chem. 1998, 566, 151– 158. (8) Treichel, P. M.; Molzahn, D. C.; Wagner, K. P. J. Organomet. Chem. 1979, 174, 191–197. (9) Brunner, H.; Klankermayer, J.; Zabel, M. Eur. J. Inorg. Chem. 2002, 2494–2501.

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Within minutes its violet solutions in toluene or THF change color in the air. After addition of Cp2Co [CpFe(Prophos)Cl] gave good 1H and 31P NMR spectra in CDCl3. However, in the 1H and 31P NMR spectra of [CpFe(Prophos)I] in CDCl3 and CD2Cl2 the signals of [CpFe(Prophos)Cl] appeared. Therefore, we avoided chloroform and methylene chloride as solvents for compounds other than [CpFe(Prophos)Cl] and we used C6D6 and toluene-d8 for 1H and for 31P NMR measurements as solvents. 31P NMR is the best method to analyze the diastereomer mixtures of the chloro and iodo complexes. The 1H and 31P NMR spectra of [CpFe(Prophos)Cl] and [CpFe(Prophos)I] in C6D6 showed diastereomer ratios of about 95/5. Obviously, these 95/5 ratios are equilibrium ratios (see below). From a solution of (RFe,RC)-/(SFe, RC)-[CpFe(Prophos)I] = 95/5 diastereomerically pure (RFe, RC)-[CpFe(Prophos)I] could be obtained by crystallization from 1/8 toluene/hexane at -20 C. Similarly, from a (RFe, RC)-/(SFe,RC)-[CpFe(Prophos)Cl]=5/95 mixture diastereomerically pure (SFe,RC)-[CpFe(Prophos)Cl] was isolated. An X-ray analysis of a single crystal from a diastereomerically pure sample established the RFe,RC configuration for [CpFe(Prophos)I] (Figure 1, left side; Table 1), using the ligand priority sequence I > Cp > PCHMe > PCH2.10,11 The molecular parameters of [CpFe(Prophos)I] in the methylene chloride solvate (RFe,RC)-[CpFe(Prophos)I] 3 CH2Cl2 (Table 1) were very similar. The dominating diastereomer of the chloro complex [CpFe(Prophos)Cl] had the same relative configuration (Figure 1, right side; Table 1), although its configurational symbol is SFe,RC as a consequence of the ligand priority sequence Cp > Cl > PCHMe > PCH2.

Configurational Stability of (RFe,RC)-[CpFe(Prophos)I] and (SFe,RC)-[CpFe(Prophos)Cl] Using diastereomerically pure (RFe,RC)-[CpFe(Prophos)I], the conditions for equilibration with respect to the Fe configuration in different solvents could be studied. In C6D6 and toluene-d8 diastereomerically pure (RFe,RC)-[CpFe(Prophos)I] did not epimerize in the presence of Cp2Co at room temperature within short time intervals (see below). In CH2Cl2 in the presence of Cp2Co, the results were different. A diastereomerically pure sample of (RFe,RC)[CpFe(Prophos)I] was dissolved in CD2Cl2 at -60 C and slowly warmed. No change was observed up to -15 C. At 0 C the signals of (SFe,RC)-[CpFe(Prophos)I] and (SFe,RC)-[CpFe(Prophos)Cl] began to grow in, the chloro ligand coming from the solvent CD2Cl2. Simultaneously, signals of free Prophos appeared due to decomposition. A diastereomerically pure sample of (SFe,RC)-[CpFe(Prophos)Cl] in CD2Cl2 did not show the signals of (RFe,RC)[CpFe(Prophos)Cl] up to 5 C, whereas at 27 C epimerization was complete after a short time, accompanied by some decomposition to free Prophos. As expected after dissolution of diastereomerically pure (RFe,RC)-[CpFe(Prophos)I] in solvents such as THF, acetone, methanol, and DMSO-d6 the signals of the diastereomer (SFe,RC)-[CpFe(Prophos)I] were present in the NMR spectrum. Thus, diastereomerically enriched samples of [CpFe(Prophos)I], can be handled without epimerization at (10) Cahn, R. S.; Ingold, C.; Prelog, V. Angew. Chem. 1966, 78, 413-447; Angew. Chem., Int. Ed. Engl. 1966, 5, 385-415. (11) Brunner, H. Enantiomer 1997, 2, 133–134.

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Figure 1. Molecular structures of (RFe,RC)-[CpFe(Prophos)I] (left) and (SFe,RC)-[CpFe(Prophos)Cl] (right) in the crystal form. Table 1. Crystallographic Data for [CpFe(P-P0 )X] Complexes (Cu Kr Radiation) (SFe,RC)[CpFe (Prophos)Cl] empirical formula formula wt cryst syst space group a (A˚) b (A˚) c (A˚) R (deg) β (deg) γ (deg) V (A˚3) Z Fcalcd (Mg/m3) abs coeff (mm-1) abs correct max/min transmissn F(000) cryst size (mm) θ range (deg) no. of rflns measd/unique Rint no. of data/params goodness of fit F2 R1/wR2 (I > 2σ(I)) R1/wR2 (all data) abs struct param largest diff peak/hole (e A˚-3) CCDC No.

C32H31ClFeP2 3 CH2Cl2 653.73 monoclinic P21 15.05386(13) 10.78240(11) 18.98963(16) 90 94.3659(8) 90 3073.39(5) 4 1.413 7.479 semiempirical 1.000 00/0.145 59 1352 0.26  0.17  0.06 2.33-62.31 26 885/9230

(RFe,RC)[CpFe (Prophos)I] C32H31FeIP2

(RFe,RC)[CpFe(Prophos)I 3 CH2Cl2

(RFe,RC)[CpFe (Prophos) CN]

(SFe,RC)[CpFe (Prophos) CO]PF6

(SFe,RC)[IndFe (Prophos) CO]I

C33H31F6FeOP2 3 2C7H8 890.61 orthorhombic P212121 10.58374(15) 16.23445(17) 24.3432(2) 90 90 90 4182.68(8) 4 1.414 4.513 semiempirical 1.000/0.473 1848 0.44  0.14  0.12 3.27-62.27 9341/5407

2C37H33FeIOP2 3 C2H6O 3 H2O 1540.73 monoclinic P21 11.45210(19) 22.1285(3) 13.66470(18) 90 90.8993(14) 90 3462.45(9) 2 1.479 11.620 semiempirical 1.000/0.234 1550 0.225  0.124  0.017 3.23-66.64 33 305/12 041

660.26 monoclinic P21 8.5056(2) 15.0338(4) 10.9136(2) 90 93.126(2) 90 1393.46(6) 2 1.574 14.260 semiempirical 1.000 00/0.434 73 664 0.21  0.14  0.08 4.06-62.43 10 886/3900

C32H31FeIP2 3 CH2Cl2 745.18 monoclinic P21 11.42524(17) 11.1501(2) 12.5399(2) 90 96.0172(16) 90 1588.69(12) 2 1.557 14.084 semiempirical 1.000 00/0.326 47 748 0.38  0.16  0.04 3.54-62.26 6077/3962

559.38 monoclinic P21 13.09737(13) 11.62720(12) 17.82324(16) 90 99.2596(9) 90 2678.86(5) 4 1.386 5.809 semiempirical 1.000 00/0.578 22 1168 0.25  0.08  0.02 2.51-62.16 14 263/7698

C33H31FeNP2 3 CH2Cl2 644.30 monoclinic P21 14.9125(2) 11.0492(2) 18.8918(3) 90 93.825(1) 90 3105.89(9) 4 1.378 6.631 semiempirical 1.000/0.283 1336 0.34  0.15  0.09 2.34-62.23 12 717/7311

0.0464 9230/705 1.072 0.0435/0.1033 0.0501/0.10986 0.008(4) 0.893/-0.617

0.0598 3900/316 1.061 0.0374/0.0951 0.0446/0.1025 -0.010(7) 1.241/-0.579

0.0718 3962/352 1.017 0.0824/0.1947 0.0964/0.2016 0.011(14) 3.149/-1.158

0.0470 7698/647 1.057 0.0544/0.1340 0.0672/0.1449 -0.026(6) 0.871/-0.618

0.0518 7311/707 0.972 0.0472/0.0642 0.0882/0.0689 0.011(5) 0.629/-0.362

0.0285 5407/514 0.962 0.0324/0.0760 0.0408/0.0760 -0.016(4) 0.302/-0.256

0.0367 12 041/788 1.051 0.0416/0.0979 0.0451/0.0994 -0.006(4) 0.799/-0.401

767239

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room temperature only in benzene and toluene solution and samples of [CpFe(Prophos)Cl] only for short time intervals (see below).

Epimerization of (RFe,RC)-[CpFe(Prophos)I] and (SFe,RC)-[CpFe(Prophos)Cl] In C6D6 a diastereomerically pure sample of (RFe,RC)[CpFe(Prophos)I] epimerized at 323 K to the equilibrium composition (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)I] = 92/8 with kep = 1.4  10-2 min-1 corresponding to the half-life τ1/2 = 50 min for the first-order approach to equilibrium (Table 2). Using the equilibrium constant Kep = 12, the rate constants kf and kr for the forward reaction RFe,RC f SFe, RC and the backward reaction SFe,RC f RFe,RC could be calculated. Table 2 shows the temperature dependence of the rate constants of the epimerization reaction between 318 and

C33H31FeNP2

(SFe,RC)[CpFe (Prophos) CN]

337 K. At 337 K the half-life for approach to equilibrium decreased to 11 min. As the half-life at 318 K was 140 min, enriched samples of (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)I] can be handled in benzene or toluene solution at room temperature for some time without appreciable epimerization. The measurements were not very accurate, because the limits of error were large for the small change from diastereomerically pure (RFe,RC)-[CpFe(Prophos)I] to the equilibrium ratio. For the measurement at 323 K this meant going from RFe,RC/SFe,RC =100/0 to 92/8. Therefore, the equilibrium constants Keq in Table 2 vary somewhat. Obviously, there is a temperature dependence of the equilibrium composition (Table 2). The epimerization of a diastereomerically pure sample of (S Fe ,R C )-[CpFe(Prophos)Cl] in C6 D 6 was about 1020 times faster than that of (R Fe ,R C )-[CpFe(Prophos)I], the equilibrium compositions and activation parameters

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Table 2. Kinetics of the Epimerization of Diastereomerically Pure (RFe,RC)-[CpFe(Prophos)I] in C6D6 and Activation Parametersa temp (K)

equilibrium ratio RFe,RC/SFe,RC

Keq

kep (min-1)

τ1/2 (min)

318 323 330 337

94/6 92/8 92/8 90/10

16 12 11 10

4.9  10-3 1.4  10-2 2.6  10-2 6.1  10-2

140 50 27 11

kfb (min-1)

krc (min-1)

2.9  10-4 1.1  10-3 2.1  10-3 6.1  10-3

4.6  10-3 1.3  10-2 2.4  10-2 5.5  10-2

activation enthalpy (kJ mol-1) ΔHqf(330 K) = 131 ΔHqr(330 K) = 108 ΔSqf(330 K) = 67 ΔSqr(330 K) = 18 activation entropy (J mol-1 K-1) ΔGqf(330 K) = 111 ΔGqr(330 K) = 103 Gibbs free energy (kJ mol-1) a In the presence of some Cp2Co. b The forward reaction: (RFe,RC)-[CpFe(Prophos)I] f (SFe,RC)-[CpFe(Prophos)I]. c The backward reaction: (SFe, RC)-[CpFe(Prophos)I] f (RFe,RC)-[CpFe(Prophos)I].

Table 3. Kinetics of the Epimerization of Diastereomerically Pure (SFe,RC)-[CpFe(Prophos)Cl] in C6D6 and Activation Parametersa temp (K)

equilibrium ratio RFe,RC/SFe,RC

Keq

kep (min-1)

τ1/2 (min)

293 301 313

5/95 8/92 10/90

20 16 9.3

1.6  10-2 2.7  10-2 5.8  10-2

43 26 12

kfb (min-1)

krc (min-1)

7.8  10-4 1.7  10-3 5.6  10-3

1.5  10-2 2.5  10-2 5.2  10-2

activation enthalpy (kJ mol-1) ΔHqf(330 K) = 74 ΔHqr (330 K) = 44 ΔSqf(330 K) = -87 ΔSqr (330 K) = -163 activation entropy (J mol-1 K-1) ΔGqf(330 K) = 102 ΔGqr (330 K) = 98 Gibbs free energy (kJ mol-1) a b c In the presence of some Cp2Co. The forward reaction: (SFe,RC)-[CpFe(Prophos)Cl] f (RFe,RC)-[CpFe(Prophos)Cl]. The backward reaction: (RFe,RC)-[CpFe(Prophos)Cl] f (SFe,RC)-[CpFe(Prophos)Cl].

remaining about the same (Table 3). As for the epimerization of (RFe,RC)-[CpFe(Prophos)I], the limits of error were large. At 293 K the half-life of the epimerization of (SFe,RC)[CpFe(Prophos)Cl] was 43 min. We could not measure the epimerization of (SFe,RC)-[CpFe(Prophos)Cl] in the presence of excess chloride, because we could not find a chloride salt soluble in benzene. It is interesting to compare the epimerization of [CpFe(Prophos)Cl] with that of its homologue [CpRu(Prophos)Cl]. The equilibrium ratio of [CpRu(Prophos)Cl] at 323 K in C6D6 had been 92.5:7.5 resulting in Keq =12.3, similar to the Keq values in Table 3. At 323 K the half-life of the approach to equilibrium had been τ1/2 = 1080 h for [CpRu(Prophos)Cl].12 Thus, the epimerization of [CpFe(Prophos)Cl] is faster than that of [CpRu(Prophos)Cl] by 2 powers of 10. As for [CpRu(Prophos)Cl], we assume that the dissociation of the M-Hal bond is the rate-determining step in the epimerization of [CpFe(Prophos)Cl]. In some of the measurements of the epimerization of [CpFe(Prophos)I] and [CpFe(Prophos)Cl] the appearance of small amounts of Prophos and Prophos oxide was observed, probably formed in decomposition and oxidation reactions. The activation parameters for the epimerization of (RFe, RC)-[CpFe(Prophos)I] and (SFe,RC)-[CpFe(Prophos)Cl] are given in Tables 2 and 3. The entropy of activation in the epimerization of (SFe,RC)-[CpFe(Prophos)Cl] in C6D6 is strongly negative, as found in the Hal exchange and epimerization reactions of [CpRu(Prophos)Hal] in chloroform/ methanol.5 Implying an increase in the number of particles, it had been explained in the [CpRu(Prophos)Hal] system with the strong solvation of the ions by the polar solvents methanol and chloroform, which increased the order. Surprisingly, in the nonpolar solvent C6D6 the epimerization of [CpFe(Prophos)Cl] also had a strongly negative entropy of activation (Table 3), whereas [CpFe(Prophos)I] had a positive entropy of activation (Table 2). We do not have an explanation for this discrepancy. (12) Brunner, H.; Tsuno, T. Acc. Chem. Res. 2009, 42, 1501–1510.

Scheme 2. (SFe,RC)-[CpFe(Prophos)CN] and (RFe,RC)-[CpFe(Prophos)CN]

(RFe,RC)/(SFe,RC)-[CpFe(Prophos)CN] Treatment of [CpFe(Prophos)I] with KCN in toluene/ methanol at room temperature gave [CpFe(Prophos)CN]. Interestingly, starting with a 95/5 ratio of (RFe,RC)-/(SFe, RC)-[CpFe(Prophos)I], a mixture of the diastereomers of [CpFe(Prophos)CN] with a RFe,RC/SFe,RC ratio close to 50/ 50 was isolated (Scheme 2). Similar 50/50 ratios of (RFe, RC)/(SFe,RC)-[CpFe(Prophos)CN] were obtained in the reaction of (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)Cl]=5/95 with KCN. Due to the methanol content in the solvent mixture, the reaction was much faster than expected on the basis of the epimerization of [CpFe(Prophos)Cl] and [CpFe(Prophos)I] in benzene. A 50/50 mixture of (R Fe,R C )- and (S Fe,R C )-[CpFe(Prophos)CN] was chromatographed on silica (40 cm) with 5/1 methylene chloride/acetone, resulting in partial separation of the diastereomers. In the front part of the band the faster migrating red SFe,RC diastereomer was enriched to RFe,RC/ SFe,RC =30/70. The rear part contained the slower migrating yellow RFe,RC diastereomer enriched to RFe,RC/SFe,RC =70/ 30. Using a silica column of 80 cm length, the slower migrating diastereomer could be enriched to RFe,RC/SFe,RC =5/95. Use of 31P NMR spectra is the best way to characterize the diastereomers. As sometimes the 31P signals broaden, addition of Cp2Co in the NMR measurements is beneficial. By fractional crystallization single crystals of both diastereomers, (RFe,RC)-[CpFe(Prophos)CN] and (SFe,RC)-[CpFe(Prophos)CN], could be isolated as described in the

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Figure 2. Molecular structures of (SFe,RC)-[CpFe(Prophos)CN] (left side) and (RFe,RC)-[CpFe(Prophos)CN] (right side). Scheme 3. (SFe,RC)-[CpFe(Prophos)CO]X and (RFe,RC)-[CpFe(Prophos)CO]X (X = PF6, I)

Experimental Section. The red crystals of (SFe,RC)-[CpFe(Prophos)CN] contain 1 mol of CH2Cl2/mol of complex, whereas the yellow crystals of (RFe,RC)-[CpFe(Prophos)CN] are solvent-free (Figure 2, Table1). The ligand priority sequence is Cp > PCHMe > PCH2 > CN. In contrast to [CpFe(Prophos)Cl] and [CpFe(Prophos)I], which epimerize in solution, the cyano complexes (RFe,RC)and (SFe,RC)-[CpFe(Prophos)CN] are configurationally stable at the metal center. Their solutions in benzene, toluene, THF, and methanol can be boiled without any diastereomer interconversion.

(RFe,RC)/(SFe,RC)-[CpFe(Prophos)CO]X (X=I, PF6) and (RFe,RC)/(SFe,RC)-[IndFe(Prophos)CO]I The cation [CpFe(Prophos)CO]þ of the compounds (RFe,RC)and (SFe,RC)-[CpFe(Prophos)CO]X (X=I, PF6) (Scheme 3) can be prepared in different ways. The thermal reaction of [CpFe(CO)2I] with Prophos in boiling ethanol gave diastereomerically pure (SFe,RC)-[CpFe(Prophos)CO]I. In the presence of excess NH4PF6 the autoclave reaction of [CpFe(Prophos)I] in toluene/methanol with 100 bar of CO pressure afforded [CpFe(Prophos)CO]PF6. Crystallization from acetone/hexane/toluene gave crystals suitable for X-ray analysis (Figure 3, left side, Table 1). The configuration turned out to be SFe,RC, given the ligand priority sequence Cp > PCHMe > PCH2 > CO. (S Fe ,R C )-[CpFe(Prophos)CO]I and (S Fe ,R C )-[CpFe(Prophos)CO]PF6 are configurationally stable in boiling methanol for hours. Even at 100 C under 100 bar of CO pressure in methanol in an autoclave there is no equilibration of (SFe,RC)-[CpFe(Prophos)CO]I. The two diastereomers (RFe,RC)- and (SFe,RC)-[CpFe(Prophos)CO]X can easily be differentiated on the basis of the 31P NMR spectra. Addition of Cp2Co is not necessary to obtain good NMR spectra. This also holds for the two diastereomers (RFe,RC)- and (SFe,RC)-[IndFe(Prophos)CO]I (Scheme 4) of the corresponding indenyl complex, which was prepared in the thermal reaction of [IndFe(CO)2I]13 with Prophos in refluxing (13) Jones, D. J.; Mawby, R. J. Inorg. Chim. Acta 1972, 6, 157–160.

methanol. The molecular structure of the cation of (SFe, RC)-[IndFe(Prophos)CO]I is shown on the right-hand side of Figure 3 (Table 1). All the carbonyl complexes (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)CO]X and (RFe,RC)-/(SFe,RC)-[IndFe(Prophos)CO]I can be chromatographed on SiO2 with THF. Similar to the case for the Cp compound, the indenyl complex (SFe, RC)-[IndFe(Prophos)CO]I is configurationally stable at the Fe atom, even at higher temperatures.

Conformation of the M-Prophos Chelate Ring Disregarding the fast rotation of the cyclopentadienyl ligand about the metal-ligand centroid, the only part of the molecules [CpFe(Prophos)L] which may adopt different conformations is the five-membered Fe-Prophos chelate ring. Is there a correlation between ring conformation and major/minor diastereomers in equilibrium mixtures? After all, equilibrium ratios of 90/10 or 95/5 correspond to energy differences of 2-3 kcal/mol between major and minor diastereomers. In the present paper we report seven new X-ray structure analyses. Including the results of [CpRu(Prophos)I] and [CpRu(Prophos)Br] from a previous study,5 we have a basis of nine data sets for analysis. We analyze our 9 data sets according to a conformational analysis of the 5-membered metal-Prophos ring, reported in 1998,14 which was based on the data of 12 chelate rings in 10 X-ray structure analyses, retrieved from the Cambridge Structural Database. We have analyzed for δ/λ chirality and conformation of the chelate ring. We have not analyzed the chirality parameters of the phenyl rings of the Prophos ligand. The results are summarized in Table 4. The δ/λ conformation of a five-membered chelate system, such as a M-Prophos ring, is defined by taking the P-P connecting line and the C-C bond of the ethane backbone as a pair of skew lines.15 Viewing away from the observer, these two skew lines define the axis and tangent of a helix, turning clockwise (δ) or anticlockwise (λ). Usually, the δ/λ chirality is controlled by the tendency of the methyl group of Prophos to orient equatorially, avoiding 1,3-axial contacts with phenyl substituents at phosphorus and pointing almost horizontally away from the complex, as indicated in Figure 4. Thus, the R configuration of Prophos enforces the λ conformation of the chelate ring in all our nine cases (Table 4, column 3). A quantitative measure is the torsion angle P-CHMe-CH2-P (column 2). Basically, the metal-Prophos ring conformations subdivide into two types, shown in Figure 5 as a half-chair conformation (14) Brunner, H.; Winter, A.; Breu, J. J. Organomet. Chem. 1998, 553, 285–306. (15) Inorg. Chem. 1970, 9, 1-5.

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Figure 3. The cation (SFe,RC)-[CpFe(Prophos)CO]þ of the compound (SFe,RC)-[CpFe(Prophos)CO]PF6 (left side) and the cation (SFe,RC)-[IndFe(Prophos)CO]þ of the compound (SFe,RC)-[IndFe(Prophos)CO]I (right side). Scheme 4. (SFe,RC)-[IndFe(Prophos)CO]I and (RFe,RC)-[IndFe(Prophos)CO]I

(a) and envelope conformations (b and c). Of the 12 chelate rings in the analysis mentioned, 9 adopted an envelope conformation, and 3 had a half-chair conformation. All our complexes contain the commercial ligand Prophos in its R configuration. In eight of our nine X-ray analyses the diastereomers analyzed have the same relative configurations. The change in the symbols RFe,RC and SFe,RC is only due to changes in ligand priority sequences. In the systems (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)Cl] and (RFe,RC)-/(SFe, RC)-[CpFe(Prophos)I] the diastereomers isolated in pure form and characterized by X-ray crystallography, namely (SFe,RC)-[CpFe(Prophos)Cl] and (RFe,RC)-[CpFe(Prophos)I], are the major, thermodynamically more stable diastereomers in 95/5 equilibria. We did not succeed in isolating crystals of the minor, thermodynamically less stable diastereomers in these systems. Similarly, the two Ru complexes (RRu,RC)-[CpRu(Prophos)I] and (RRu,RC)-[CpRu(Prophos)Br], included in this study, are the major diastereomers in 90/ 10 equilibria.5 The complexes (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)CN], (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)CO]X, and (RFe,RC)-/(SFe,RC)-[IndFe(Prophos)CO]I are configurationally stable at the metal atom. There is no diastereomer interconversion. Nevertheless, the crystals of (SFe,RC)[CpFe(Prophos)CN], (SFe,RC)-[CpFe(Prophos)CO]PF6, and (SFe,RC)-[IndFe(Prophos)CO]I isolated and characterized by X-ray crystallography all belong to the diastereomer series which is thermodynamically favored in the Fe and Ru systems with labile metal configuration. The only exception is the cyano complex (RFe,RC)-[CpFe(Prophos)CN]. It is a member of the series of the minor diastereomers. The conformation of the exceptional cyano complex (RFe,RC)-[CpFe(Prophos)CN] deviates strongly from that of the other eight complexes. (RFe,RC)-[CpFe(Prophos)CN] has a heavily distorted envelope conformation, the distortion going in the direction opposite to the half-chair conformation (a) in Figure 5. This is obvious from the angles P-M-P-CHMe and P-M-P-CH2 in columns 4 and 5

of Table 4, which both are in the middle range. In comparison to the corresponding angles of the other eight complexes, these values are unprecedented. On the basis of this result, we predict similar conformations for the minor diastereomers in diastereomer equilibria with configurationally labile metal centers. Obviously, it is the heavy distortion of the envelope conformation which increases the energy content of these diastereomers by 2-3 kcal/mol in comparison to their major counterparts. In the other eight complexes the M-Prophos rings have envelope conformations, characterized by a large P-MP-CHMe angle on the “steep” substituted side (Table 4, column 4) and small positive ((b) in Figure 5) or negative ((c) in Figure 5) P-M-P-CH2 angles on the “flat” unsubstituted side (Table 4, column 5). The envelope conformations (b) and (c) are typical for the thermodynamically more stable diastereomers in diastereomer equilibria with configurationally labile metal atoms. In our study we did not find complexes with half-chair conformations.

Experimental Section General Considerations. Melting points (not corrected): B€ uchi SMP 20. IR: Varian FTS800 and BIORAD FTS60A. 1H/31P NMR: Bruker Avance 400 (400/162 MHz, T=300 K), TMS as internal standard and H3PO4 as external standard. MS: Finnigan MAT 95 (EI, 70 eV). [CpFe(Prophos)Cl]. [CpFe(CO)2Cl] (212 mg, 1 mmol) and (R)-Prophos (412 mg, 1 mmol) were dissolved in 230 mL of toluene and irradiated with a Hg lamp at room temperature. After 5 h the originally red solution had become black-violet. The solution was passed through a thin layer of SiO2 (3 cm) to remove a black precipitate. The SiO2 layer was washed with methylene chloride, and the combined solvents were evaporated. The remaining crude [CpFe(Prophos)Cl] (300 mg, 53%) was dissolved in methylene chloride (7 mL) and layered with 60 mL of pentane. After 24 h at -20 C (SFe,RC)-[CpFe(Prophos)Cl] was obtained as black crystals suitable for X-ray analysis. Mp: 200 C dec. 1H NMR (400 MHz, benzene-d6, Cp2Co, minor diastereomer in brackets, if distinguishable): δ 8.22 (t, 2H, 3 J=8.6 Hz, ArH) [8.38 (br t, 2H, 3J=9.3 Hz, ArH)], 7.63 (t, 2H, 3 J=7.6 Hz, ArH) [7.86 (br t, 2H, 3J=9.0 Hz, ArH)], 7.35 (t, 2H, 3 J = 9.0 Hz, ArH), 7.21-6.88 (m, 14H, ArH), 4.01 (s, 5H, Cp) [4.05 (s, 5H, Cp)], 2.71-2.58 (m, 1H, CH), 2.35-2.15 (m, 1H, CH), 1.82-1.71 (m, 1H, CH), 0.83 (dd, 3H, 3JH-H = 7.4 Hz, 3 JH-P = 9.1 Hz, Me). 31P{1H} NMR (162 MHz, benzene-d6, Cp2Co, minor diastereomer in brackets): δ 105.68 (1P, 2JP-P = 43.4 Hz) [98.71 (1P, 2JP-P = 35.0 Hz)], 83.15 (1P, 2JP-P = 43.4 Hz) [88.77 (1P, 2JP-P = 35.0 Hz)]. MS (EI): m/z 568 (Mþ, 23), 412 (100), 186 (48). Anal. Calcd for C32H31ClFeP2 (568.8): C, 67.57; H, 5.49. Found: C, 67.69; H, 5.44.

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Table 4. Conformational Analysis of the M-Prophos Chelate Ring complex

— P-CHMe-CH2-P chelate chirality

(RFe,RC)-[CpFe(Prophos)I] 3 CH2Cl2 (RFe,RC)-[CpFe(Prophos)I] (SFe,RC)-[CpFe(Prophos)Cl] 3 CH2Cl2 (1) (SFe,RC)-[CpFe(Prophos)Cl] 3 CH2Cl2 (2) (SFe,RC)-[CpFe(Prophos)CN] 3 CH2Cl2 (1) (SFe,RC)-[CpFe(Prophos)CN] 3 CH2Cl2 (2) (RFe,RC)-[CpFe(Prophos)CN] (SFe,RC)-[CpFe(Prophos)CO]PF6 3 2C7H8 (SFe,RC)-[IndFe(Prophos)CO]I 3 C2H6O (1) (SFe,RC)-[IndFe(Prophos)CO]I 3 C2H6O (2) (RRu,RC)-[CpRu(Prophos)I] (RRu,RC)-[CpRu(Prophos)Br] a

-43.0 -45.6 -45.1 -45.8 -45.8 -45.5 -35.7 -49.8 -52.6 -51.5 -43.6 -47.7

λ λ λ λ λ λ λ λ λ λ λ λ

— P-M-P-CHMe -24.8 -23.3 -26.4 -27.9 -27.9 -26.9 15.2 -21.6 -22.3 -19.6 -29.7 -21.6

— P-M-P-CH2 conformation typea 3.6 0.5 3.5 5.2 5.1 2.7 -32.6 -2.7 -3.3 -5.5 8.0 -2.3

envelope (c) envelope (c) envelope (c) envelope (c) envelope (c) envelope (c) distorted envelope envelope (b) envelope (b) envelope (b) envelope (c) envelope (b)

See Figure 5 for definition of envelope types.

Figure 4. Conformation of the M-Prophos chelate ring in (SFe,RC)-[CpFe(Prophos)Cl] (left side), typical for all the compounds of Table 2 except (RFe,RC)-[CpFe(Prophos)CN], and the conformation in the exceptional compound (RFe,RC)-[CpFe(Prophos)CN] (right side).

Figure 5. Five-membered M-Prophos chelate rings: (a) halfchair conformation, (b, c) envelope conformations (frontside, M; backside, ethane backbone). [CpFe(Prophos)I]. [CpFe(CO)2I] (608 mg, 2 mmol) and (R)Prophos (824 mg, 2 mmol) were dissolved in 230 mL of toluene and irradiated with a Hg lamp at room temperature. After 6 h the originally black-brown solution had become black-violet (no precipitate). The solution was evaporated to dryness. The residue was dissolved in methylene chloride (8 mL) and layered with 65 mL of pentane to give 1.1 g of [CpFe(Prophos)I] as black crystals (83%). Diastereomerically pure crystals of (RFe,RC)-[CpFe(Prophos)I], suitable for X-ray analysis, were obtained by crystallization from toluene/hexane 1:8 at -20 C. Mp: 192 C dec. 1H NMR (400 MHz, benzene-d6, Cp2Co, minor diastereomer in brackets, if distinguishable): δ 8.19 (t, 2H, 3 J=8.0 Hz, ArH) [8.39 (br t, 2H, 3J=7.6 Hz, ArH)], 7.63 (t, 2H, 3 J=7.6 Hz, ArH) [7.86 (br t, 2H, 3J=9.0 Hz, ArH)], 7.34-6.93 (m, 16H, ArH), 4.09 (s, 5H, Cp) [4.14 (s, 5H, Cp)], 3.27-3.16 (m, 1H, CH), 2.56-2.37 (m, 1H, CH), 1.83-1.74 (m, 1H, CH), 0.89 (dd, 3H, 3JH-H = 7.1 Hz, 3JH-P = 9.5 Hz, Me) [1.07 (dd, 3H, 3 JH-H = 7.8 Hz, 3JH-P = 10.7 Hz, Me)]. 31P{1H} NMR (162 MHz, benzene-d6, Cp2Co, minor diastereomer in brackets): δ 106.90 (1P, 2JP-P = 35.7 Hz) [105.01 (1P, 2JP-P = 29.7 Hz)], 85.04 (d, 1P, 2JP-P =35.7 Hz) [86.83 (1P, 2JP-P =29.7 Hz)]. MS (EI): m/z 660 (100, Mþ), 533 (23, Mþ - I). Anal. Calcd for C32H31FeIP2 (660.3): C, 58.21; H, 4.73. Found: C, 58.35; H, 4.78. [CpFe(Prophos)CN]. (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)I] 95/5 (1.04 g, 1.57 mmol) was dissolved in toluene (30 mL), combined with a solution of KCN (3.1 g, 47.6 mmol) in methanol (50 mL), and stirred at room temperature for 1 h. The originally violet solution became yellow-orange. After evaporation the

residue was dissolved in methylene chloride and extracted with water. The methylene chloride solution was evaporated to give 800 mg of [CpFe(Prophos)CN] (89%) as a mixture of the RFe,RC and SFe,RC diastereomers in a ratio close to 50/50. Diastereomer separation of (RFe,RC)- and (SFe,RC)-[CpFe(Prophos)CN] was carried out by fractional precipitation. An 800 mg amount of (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)CN] = 50/50 was dissolved in toluene (5 mL), and hexane (20 mL) was added. The precipitate was isolated and dissolved in 30 mL of toluene. Addition of 90 mL of hexane gave a new precipitate. This procedure was repeated another four times with reduced amounts of solvents. Then, the residue, containing the enriched less soluble SFe,RC diastereomer, showed the diastereomer ratio RFe,RC/SFe,RC e 5/95. A sample was recrystallized from 1/2 acetone/hexane to give red crystals proven to be (SFe, RC)-[CpFe(Prophos)CN] 3 CH2Cl2 by X-ray analysis and showing a RFe,RC/SFe,RC ratio of 0/100 in the NMR spectrum. From the filtrate of a fractional crystallization yellow needles were obtained, confirmed to be the RFe,RC diastereomer of [CpFe(Prophos)CN] by X-ray crystallography. Mp: 225 C dec. IR (KBr): ν 2075 cm-1 (CN). (SFe, RC)-[CpFe(Prophos)CN] (less soluble, red): 1H NMR (400 MHz, CDCl3, Cp2Co) δ 7.92-7.84 (m, 2H, ArH), 7.57-7.14 (m, 18H, ArH), 4.08 (s, 5H, CpH), 2.91-2.82 (m, 1H, CH), 2.62-2.40 (m, 1H, CH), 1.90-1.75 (m, 1H, CH), 1.05 (dd, 3JH-P= 11 Hz, 3JH-H = 6.8 Hz, 3H, Me); 31P{1H} NMR (162 MHz, CDCl3, Cp2Co) δ 111.18 (d, 2JP-P=41.2 Hz, 1P), 90.17 (d, 2JP-P= 41.2 Hz, 1P). (RFe,RC)-[CpFe(Prophos)CN] (more soluble, yellow): 1H NMR (400 MHz, CDCl3, Cp2Co) δ 8.01-7.93 (2H, m, ArH), 7.74-7.67 (2H, m, ArH), 7.37-7.01 (m, 16H, ArH), 4.13 (s, 5H, CpH), 2.93-2.83 (m, 1H, CH), 2.55-2.40 (m, 1H, CH), 1.88-1.77 (m, 1H, CH), 0.93 (dd, 3JH-P 11.7 Hz, 3 JH-H = 5.9 Hz, 3H, Me); 31P{1H} NMR (162 MHz, CDCl3, Cp2Co) δ 109.24 (d, 2JP-P =33.6 Hz, 1P), 95.23 (d, 2JP-P =33.6 Hz, 1P). MS (EI): m/z 559 (Mþ). Anal. Calcd for C33H31FeNP2 (559.4): C, 70.84; H, 5.58; N, 2.50. Found: C, 70.66; H, 5.32; N, 2.33. [CpFe(Prophos)CO]I. [CpFe(CO)2I] (360 mg, 1.17 mmol) and (R)-Prophos (500 mg, 1.17 mmol) were dissolved in 35 mL of ethanol under nitrogen protection and refluxed for 10 h. The red-brown solution became yellow-green. The solvent was removed. The residue was treated with 40 mL of hot THF. After the mixture was cooled to room temperature, the solid was collected by filtration and washed with THF. Yield: 300 mg (35%) of diastereomerically pure (SFe,RC)-[CpFe(Prophos)CO]I. Mp: 183 C dec. IR (KBr): ν 1971 cm-1 (CO). 1H NMR (400 MHz, CDCl3, major yellow diastereomer, minor green diastereomer in brackets, if distinguishable): 8.06-7.99 (m, 2H, ArH), 7.77-7.54 (m, 18H, ArH), 5.06 (t, 5H, 3JH-P = 1.4 Hz, CpH) [4.99 (t, 5H, 3JH-P = 1.5 Hz, CpH)], 3.56-3.36 (m, 2H, CH), 2.86-2.74 (m, 1H, CH), 2.46-2.38 (m, 1H, CH), 1.29 (ddd, 3H, 3 JH-P=12.5 Hz, 3JH-H=6.3 Hz, 4JH-P=0.7 Hz, Me) [0.87 (dd, 3H, 3JH-P=15.5 Hz, 3JH-H=7.0 Hz)]. 31P{1H} NMR (162 MHz, CDCl3, major diastereomer, minor diastereomer in brackets):

Article δ 101.14 (d, 1P, 2JP-P=39.7 Hz) [109.22 (d, 1P, 2JP-P=25.9 Hz)], 78.56 (d, 1P, 2JP-P=39.7 Hz) [90.44 (d, 1P, 2JP-P=25.9 Hz)]. MS (ES, MeCN): m/z 561 (cation). Anal. Calcd for C33H31FeIOP2 (688.3): C, 57.58; H, 4.54. Found: C, 57.63; H, 4.90. [CpFe(Prophos)CO]PF6. (RFe,RC)-/(SFe,RC)-[CpFe(Prophos)I] 95/5 (100 mg, 0.15 mmol) was dissolved in toluene (10 mL) and combined with a solution of NH4PF6 (50 mg, 0.3 mmol) in methanol (10 mL). The mixture was pressurized with CO (100 bar) in an autoclave (100 mL) at room temperature for 10 h. The originally violet solution had become yellow. The solvents were evaporated. Dissolution in methylene chloride and extraction with water afforded a quantitative yield of [CpFe(Prophos)CO]PF6 (diastereomer ratio RFe,RC/SFe,RC = 7/93) after evaporation of the methylene chloride phase. Crystals of (SFe,RC)-[CpFe(Prophos)CO]PF6 suitable for X-ray analysis were obtained by crystallization from 5/1/2 acetone/toluene/hexane at -20 C. Mp: 135 C dec. IR (KBr): ν 1970 (CO) cm-1. 1H NMR (400 MHz, acetone-d6, major diastereomer, minor diastereomer in brackets, if distinguishable): δ 7.89-7.41 (m, 20H, ArH), 4.91 (t, 3JP-H =1.3 Hz, 5H, CpH) [4.86 (t, 3JP-H =1.4 Hz, 5H, CpH)], 3.38-3.17 (m, 1H, CH), 2.75-2.65 (m, 1H, CH), 2.36-2.26 (m, 1H, CH), 1.29 (dd, 3JH-H =6.5 Hz, 3JP-H =12.4 Hz, 3H, Me) [0.74 (dd, 3JH-H =7.0 Hz, 3JP-H =15.1 Hz, 3H, Me)]. 31P{1H} NMR (162 MHz, acetone-d6, major diastereomer, minor diastereomer in brackets): δ 100.13 (d, 2JP-P =40.4 Hz, 1P) [109.57 (d, 2JP-P=25.9 Hz, 1P)], 78.71 (d, 2JP-P=40.4 Hz, 1P) [90.84 (d, 2 JP-P=25.9 Hz, 1P)], -142.56 (sept, 1JP-F =707.5 Hz, 1P). MS (ES, MeCN): m/z 561 (cation). Anal. Calcd for C33H31F6FeOP3 (706.4): C, 56.11; H, 4.42. Found: C, 56.06; H, 4.42. [IndFe(Prophos)CO]I. [IndFe(CO)2I]13 (240 mg, 0.67 mmol) and (R)-Prophos (276 mg, 0.67 mmol) were dissolved in 20 mL of methanol under nitrogen protection and refluxed for 3 h. The red-brown solution became orange-red. The solvent was removed. The residue was dissolved in THF and chromatographed on SiO2 with THF. There was a first fast migrating red band (50 mg) of a carbonyl-containing byproduct. The slowly migrating orange-red band afforded 250 mg of [IndFe(Prophos)CO]I (50% yield). The diastereomer ratio was SFe,RC/RFe,RC = 70:30. Recrystallization from ethanol gave a sample of diastereomer composition 97/3. Another recrystallization from ethanol afforded the diastereomerically pure product.

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Mp: 205 C dec. IR (KBr): ν 1968 cm-1. 1H NMR (400 MHz, acetone-d6, major diastereomer, minor diastereomer in brackets, if distinguishable): δ 7.86-7.45 (m, 20H, ArH), 7.27 (ddd, 1H, 3JH-H = 8.4 Hz, 3JH-H = 6.6 Hz, 4JH-H = 1.1 Hz, IndH), 6.99-6.93 (m, 2H, IndH), 6.56 (d, 1H, 3JH-H = 8.4 Hz, IndH) [6.45 (d, 1H, 3JH-H = 8.8 Hz, IndH)], 5.91 (s, 1H, IndH) [6.02 (s, 1H, IndH)], 5.36-5.33 (m, 2H, IndH) [5.06 (s, 1H, IndH)], 3.47-3.26 (m, 1H, CH), 2.53-2.41 (m, 1H, CH), 2.27-2.17 (m, 1H, CH), 1.18 (ddd, 3H, 3JH-P=12.5 Hz, 3JH-H=6.6 Hz, 4JH-P= 0.7 Hz, Me) [0.73 (dd, 3H, H, 3JH-P =14.9 Hz, 3JH-H =7.0 Hz)]. 31 P{1H} NMR (162 MHz, acetone-d6, major diastereomer, minor diastereomer in brackets): δ 103.23 (d, 2JP-P = 41.2 Hz, 1P) [111.70 (d, 2JP-P =26.0 Hz, 1P)], 73.91 (d, 2JP-P =41.2 Hz, 1P) [89.78 (d, 2JP-P = 26.0 Hz, 1P)]. MS (ES, MeCN): m/z 611 (cation). Anal. Calcd for C37H33FeIOP2 (738.4): C, 60.19; H, 4.51. Found: C, 59.61; H, 4.57. X-ray Analysis. The data for all crystals were collected on an Oxford Diffraction Gemini Ultra diffractometer with CCD detector and multilayer optics for Cu KR radiation (λ = 1.5418 A˚) at 123 K using an Oxford Instruments Cryojet cooler. For data reduction the Oxford Diffraction software16 was used. The structures were solved by direct methods (SIR-97)17 and refined by full-matrix least squares on F2 (SHELXL-97).18 All H atoms were included at calculated positions. Specific points concerning X-ray structure analysis are discussed in the Supporting Information. CCDC numbers given in Table 1 refer to supplementary crystallographic data, which can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, U.K. (fax, (internat.) 1 44-1223/336-033; e-mail, deposit@ ccdc.cam.ac.uk). Supporting Information Available: Figures giving NMR spectra, text giving additional details of the X-ray crystallographic analysis, and CIF files giving crystal data. This material is available free of charge via the Internet at http://pubs.acs.org. (16) CrysAlis RED; Oxford Diffraction Ltd., 2006. (17) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 1999, 32, 115–119. (18) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.