Kinetic and Thermodynamic Control of Nitrile Dissociation in the

Publication Date (Web): June 1, 2018. Copyright © 2018 American Chemical Society ... ACS ActiveView PDF. Hi-Res Print, Annotate, Reference QuickView...
0 downloads 0 Views 1MB Size
Download PDF
Article Cite This: Organometallics XXXX, XXX, XXX−XXX

Kinetic and Thermodynamic Control of Nitrile Dissociation in the Complexes (RFe,RC)/(SFe,RC)‑[CpFe(Prophos)NCR]X (X = I, PF6) by the Inductive Effect Henri Brunner,*,† Takashi Tsuno,*,‡ Takaki Kurosawa,‡ Hikaru Kitamura,‡ and Hayato Ike‡ †

Institut für Anorganische Chemie, Universität Regensburg, 93040 Regensburg, Germany Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Chiba 275-8575, Japan

‡

S Supporting Information *

ABSTRACT: The chiral-at-metal complexes (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCR]X (X = I, PF6; R = Et, Ph, p-substituted Ph) were prepared, and the diastereomers were separated by fractional crystallization. Eight diastereomerically pure complexes (SFe,RC)-[CpFe(Prophos)NCR]X could be characterized by X-ray crystallography. The kinetics of epimerization with respect to the labile Feconfiguration in CDCl3 at ambient temperatures was measured for the EtCN, PhCN, and (p-C6H4NMe2) complexes. The half-lives of 162 and 760 min of the first-order reactions of (SFe,RC)-[CpFe(Prophos)NCPh]PF6 and (SFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]PF6 at 293 K demonstrate the importance of the inductive effect in the rate-determining cleavage of the Fe−NCR bond. The diastereomer ratios of 5:95 to 10:90 at equilibrium under thermodynamic control were strongly in favor of the (SFe,RC)-[CpFe(Prophos)NCR]X diastereomers. In ligand exchange reaction reactions, (RFe,RC)/(SFe,RC) diastereomer ratios of up to 35:65 were observed under kinetic control.

■

INTRODUCTION In coordination chemistry, acetonitrile is a ubiquitous ligand which is easily introduced into and removed from a complex. Acetonitrile is available as a convenient solvent, and the synthesis of acetonitrile complexes is straightforward. Usually, the bonds between metal atom and acetonitrile are weak, allowing a fast dissociation of the acetonitrile ligand and replacement by other ligands. The high volatility of acetonitrile can be used to shift equilibria by removing the acetonitrile ligand with the help of N2 bubbling.1 Replacement of the methyl group in MeCN by other alkyl or aryl groups provides the opportunity to obtain nitrile ligands with variable electronic and steric properties. (SFe,RC)-[CpFe(Prophos)NCMe]PF6 is a well-behaved prime example of a chiral-at-metal compound, the synthesis and properties of which we reported previously. In acetonitrile solution, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)I]2 was converted into (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCMe]I.3 (RFe,RC)/ (SFe,RC)-[CpFe(Prophos)NCMe]PF6 was obtained in the presence of NH4PF6.3 The (RFe,RC)/(SFe,RC) diastereomers, which only differ in the configuration at the metal atom, were separated by fractional crystallization. The diastereomerically pure compounds (SFe,RC)-[CpFe(Prophos)NCMe]X (X = I, PF6) could be characterized by X-ray crystallography. In solution, (SFe,RC)-[CpFe(Prophos)NCMe]X (X = I, PF6) epimerized with respect to the Fe-configuration by ratedetermining cleavage of the Fe−NCMe bond. Several times, (SFe,RC)-[CpFe(Prophos)NCMe]X (X = I, PF6) served as © XXXX American Chemical Society

starting material for the synthesis of other chiral-at-iron compounds.1−4 In the present paper we describe synthesis, characterization, and epimerization of the ethyl and para-substituted arylnitrile complexes (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCEt]X and (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCC6H4Rp]X (X = I, PF6; Rp = H, Me, OMe, NMe2, NO2). The stable compounds are suitable for kinetic studies. We show that the cleavage of the Fe−NCR bond in the rate-determining step is controlled by the inductive effect of the nitrile substituent, allowing a change of the Fe configuration from slow to fast. Kinetic control affects the ligand substitution reactions and thermodynamic control establishes the equilibrium concentrations of the products.

■

RESULTS AND DISCUSSION Synthesis and Characterization of (RFe,RC)/(SFe,RC)[CpFe(Prophos)NCR]X (X = I, PF6). The nitrile complexes (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCR]X (X = I, PF6) were prepared by stirring a THF solution of (RFe,RC)/(SFe,RC)[CpFe(Prophos)I] 95:5 with the corresponding nitrile and optionally NH4PF6 for 10 h at room temperature (Scheme 1). The well-separated doublets in the 31P NMR spectra allow the determination of the ratios of the (RFe,RC)/(SFe,RC) diastereomers. In all cases, the diastereomerically pure (SFe,RC)compounds could be obtained by crystallization as indicated for Received: March 17, 2018

A

DOI: 10.1021/acs.organomet.8b00146 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics Scheme 1. Nitrile Complexes (RFe,RC)/(SFe,RC)[CpFe(Prophos)NCR]X (X = I, PF6)a

a

Priority sequence5,6 Cp > PCHMe > PCH2 > NCR.

Figure 1. Epimerization of (SFe,RC)-[CpFe(Prophos)NCEt]PF6, (SFe,RC)-[CpFe(Prophos)NCPh]PF6, and (RFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]PF6 in CDCl3 at 293 K. (SFe,RC)-[CpFe(Prophos)NCEt]PF6 (black circles); (RFe,RC)-[CpFe(Prophos)NCEt]PF6 (black squares); (SFe,RC)-[CpFe(Prophos)NCPh]PF6 (red circles); (RFe,RC)-[CpFe(Prophos)NCPh]PF6 (red squares); (S Fe ,R C )-[CpFe(Prophos)(p-C 6 H 4 NMe 2 )]PF 6 (cyan circles); (RFe,RC)-[CpFe(Prophos)(p-C6H4NMe2)]PF6 (cyan squares).

each complex. Eight complexes were characterized by X-ray analysis. Table S1 lists the crystallographic data. Conformational flexibility in the compounds (RFe,RC)/ (SFe,RC)-[CpFe(Prophos)NCR]X, which changes the shape of the molecules, is only possible for the Prophos and the nitrile ligands. In all the compounds characterized by X-ray crystallography, the five-membered Prophos rings adopt devCHMe conformations with the CHMe group on the steep side and the favored equatorial orientation of the methyl group in the envelope structure.7 The torsion angles P−Fe−P−CHMe and P−Fe−P−CH2 measure the deviation of the carbon atoms of the CHMe and CH2 groups from the P−Fe−P plane.7 There is no preferred orientation of the aryl rings of the nitrile ligands. Including the published structures of (S Fe ,RC )-[CpFe(Prophos)NCPh]X (X = I, PF 6) and (SFe,RC)-[CpFe(Prophos)NC(p-C6H4NO2)]PF6, the positive torsion angles Cpcent−Fe−Ci−Co range between 2 and 137°.8,9 The iodide salts are less stable than the PF6 salts, because the iodide anion is a potential ligand for the unsaturated intermediate (RFe,RC)/(SFe,RC)-[CpFe(Prophos)]+, formed on dissociation of the Fe−NCR bond. On standing in solution for a longer time or at higher temperatures, the NMR signals of (RFe,RC)/(SFe,RC)-[CpFe(Prophos)I] show up. Epimerization Kinetics. Propionitrile Complexes (SFe,RC)[CpFe(Prophos)NCEt]X (X = I, PF6). The epimerization kinetics of the acetonitrile complexes (SFe,RC)-[CpFe(Prophos)NCMe]X (X = I, PF6) is known.3 The epimerization kinetics of the corresponding propionitrile complexes will provide the effect of the increased electron donation. In Figure 1, the decrease of the concentration of (SFe,RC)[CpFe(Prophos)NCEt]PF6 and the increase of the concentration of (RFe,RC)-[CpFe(Prophos)NCEt]PF6 in CDCl3 at 293 K as a function of time is shown (black curves). The reaction is first-order with a half-life of 138 min for approach to the equilibrium (SFe,RC)/(RFe,RC)-[CpFe(Prophos)NCEt]PF6 93:7. The epimerization of the propionitrile derivatives (SFe,RC)[CpFe(Prophos)NCEt]X (X = I, PF6) (half-lives 372 and 138 min, Table 1) was appreciably slower than that of the corresponding acetonitrile compounds (S Fe ,R C )-[CpFe(Prophos)NCMe]X (X = I, PF6) (half-lives 216 and 96 min).3 The reason for the retardation is the inductive effect. The higher electron density makes propionitrile the better ligand for the 16-electron intermediate [CpFe(Prophos)]+ compared to acetonitrile. Due to the linear N−C−C system,

there should be no difference in the steric effect of acetonitrile and propionitrile. The epimerization of (SFe,RC)-[CpFe(Prophos)NCEt]X (X = I, PF6) follows a dissociative or interchange mechanism similar to that of (SFe,RC)-[CpFe(Prophos)NCMe]X (X = I, PF6).3 The rate-determining step is the cleavage of the FeNCEt bond (Figure 2). In principle, the 16-electron intermediate [CpFe(Prophos)]+ may undergo pyramidal inversion (inversion of the Fe configuration) or react with EtCN in a bimolecular reaction (retention of the Fe configuration). As propionitrile is a constituent of the bimolecular back reaction of the rate-determining step, we investigated the influence of free EtCN on the epimerization rate of (SFe,RC)[CpFe(Prophos)NCEt]X (X = I, PF6) (Table 1). Increasing amounts of EtCN increased the rate of epimerization appreciably. For the iodide salt, the effect was much larger than for the PF6 salt. The same effect had been observed in the epimerization of (SFe,RC)-[CpFe(Prophos)NCMe]I.3 The temperature dependence of the epimerization rate of (SFe,RC)-[CpFe(Prophos)NCEt]X (X = I, PF6) was as expected. At 313 K, the half-life of epimerization of the I and PF6 salts dropped to 17 and 11 min, respectively. The equilibrium compositions changed from 6:94 at 293 K to 10:90 at 313 K. The positive entropy of activation is in accord with a dissociative process (Table 1). Benzonitrile Complex (SFe,RC)-[CpFe(Prophos)NCPh]PF6. The epimerization of (SFe,RC)-[CpFe(Prophos)NCPh]PF6 in CDCl3 at 293 K is shown in Figure 1 (red curves). The results and the temperature dependence of the epimerization are given in Table 2. We also investigated the influence of free PhCN on the epimerization rate of (SFe,RC)-[CpFe(Prophos)NCPh]PF6 (Table 2). Surprisingly, increasing amounts of benzonitrile decreased the rate of epimerization of the corresponding complexes appreciably, while the opposed effect of added ligand was observed for alkyl nitriles (see above). This startling discrepancy will be discussed in the following section. B

DOI: 10.1021/acs.organomet.8b00146 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics Table 1. Kinetics of the Epimerization of (SFe,RC)-[CpFe(Prophos)NCEt]X (X = I or PF6) in CDCl3

X

I

PF6

a

temp. (K)

Keq × 102

kep × 103 (min−1)

6.2 1.9 ± 293a 293b 7.4 6.5 ± 293c 7.3 7.2 ± 300a 8.2 6.0 ± 307a 8.6 17.0 ± 313a 9.9 40.0 ± ΔH⧧→ = 126 ± 4 kJ mol−1 ΔS⧧→ = 79 ± 12 J mol−1 K−1 ΔG⧧→ (300 K) = 103 ± 7 kJ mol−1 293a 7.8 5.0 ± 293b 8.3 5.7 ± 300a 8.6 15.0 ± 307a 10.0 38.0 ± 313a 12.0 65.0 ± ΔH⧧→ = 111 ± 3 kJ mol−1 ΔS⧧→ = 33 ± 11 J mol−1 K−1 ΔG⧧→ (300 K) = 101 ± 9 kJ mol−1

0.15 0.24 0.10 0.14 0.86 3.0

0.04 0.13 0.64 1.0 5.5

τ1/2 (min)

k→ × 103 (min−1)

372 0.12 107 0.45 96 0.49 115 0.46 40 1.4 17 3.6 ΔH⧧← = 113 ± 3 kJ mol−1 ΔS⧧← = 54 ± 13 J mol−1 K−1 ΔG⧧← (300 K) = 97 ± 8 kJ mol−1 138 0.36 121 0.44 45 1.2 19 3.6 11 6.8 ΔH⧧← = 95 ± 3 kJ mol−1 ΔS⧧← = 0 ± 12 J mol−1 K−1 ΔG⧧← (300 K) = 94 ± 7 kJ mol−1

k← × 103 (min−1)

equilibrium ratio (RFe,RC)/(SFe,RC)

1.8 6.1 6.7 5.6 16.0 37.0

6/94 7/93 7/93 8/92 8/92 9/91

4.6 5.3 1.4 34.0 58.0

7/93 8/92 8/92 9/91 10/90

In CDCl3 bIn CDCl3/EtCN (99:1, v/v). cIn CDCl3/EtCN (10:1, v/v).

Figure 2. Kinetic and thermodynamic control in the ligand exchange MeCN/PhCN in (SFe,RC)-[CpFe(Prophos)NCMe]PF6.

Rate Increase and Decrease on Ligand Addition. In the epimerization of (SFe,RC)-[CpFe(Prophos)NCMe]PF6 in CDCl3 solution, it had been observed that the addition of

increasing amounts of free ligand MeCN decreased the reaction rate.3 A bimolecular reaction of (SFe,RC)-[CpFe(Prophos)NCMe]PF 6 and MeCN with inversion of the metal C

DOI: 10.1021/acs.organomet.8b00146 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics Table 2. Kinetics of the Epimerization of (SFe,RC)-[CpFe(Prophos)NCPh]PF6 in CDCl3

temp. (K)

Keq × 102

kep × 103 (min−1)

a

293 5.4 4.3 293b 7.72 2.4 293c 8.1 2.3 300a 8.1 9.2 307a 11.0 18.0 313a 12.0 51.0 ΔH⧧→= 116 ± 6 kJ mol−1 ΔS⧧→ = 48 ± 19 J mol−1 K−1 ΔG⧧→ (300 K) = 102 ± 11 kJ mol−1 a

± ± ± ± ± ±

τ1/2 (min)

0.27 0.08 0.06 0.74 1.1 4.2

k→ × 103 (min−1)

k← × 103 (min−1)

equilibrium ratio (RFe,RC)/(SFe,RC)

4.1 2.2 2.1 8.4 16.0 46.0

5/95 7/93 7/93 7/93 10/90 10/90

162 0.22 291 0.17 305 0.17 73 0.68 38 1.7 14 5.3 ΔH⧧←= 86 ± 6 kJ mol−1 ΔS⧧← = −30 ± 19 J mol−1 K−1 ΔG⧧← (300 K) = 95 ± 11 kJ mol−1

In CDCl3. bIn CDCl3/PhCN (99:1, v/v). cIn CDCl3/PhCN (10:1, v/v).

Table 3. Kinetics of the Epimerization of (SFe,RC)-[CpFe(Prophos)NC(p-C6H4X)]PF6 in CDCl3

X

temp. (K)

NMe2

Me a

Keq × 102

kep × 103 (min−1)

293 7.5 0.91 ± 293b 8.5 0.84 ± 300a 8.6 0.22 ± 307a 9.6 9.1 ± 313a 1.1 25.0 ± ΔH⧧→ = 140 ± 3 kJ mol−1 ΔS⧧→ = 117 ± 12 J mol−1 K−1 ΔG⧧→ (300 K) = 105 ± 8 kJ mol−1 293a 8.7 1.5 a

0.03 0.03 0.09 0.25 1.7

τ1/2 (min)

k→ × 103 (min−1)

k← × 103 (min−1)

760 0.064 822 0.066 312 0.18 75 0.81 29 2.5 ΔH⧧← = 126 ± 4 kJ mol−1 ΔS⧧← = 93 ± 13 J mol−1 K−1 ΔG⧧← (300 K) = 94 ± 7 kJ mol−1 463 0.12

equilibrium ratio (RFe,RC)/(SFe,RC)

0.85 0.78 2.0 8.3 23.0

7/93 8/92 8/92 9/91 10/90

1.2

8/92

In CDCl3. bIn CDCl3/p-Me2NC6H4CN (10:1, v/v).

Excluding bimolecular reactions, how can the addition of free nitrile ligands affect the rate of dissociative reactions such as the epimerization of the complexes (SFe,RC)-[CpFe(Prophos)NCR]PF6 in both directions? The answer is by stabilization or destabilization of ground state and transition state of the rate determining step, which is the cleavage of the Fe−NCR bond. Ground state and transition state are ionic. The solvent CDCl3 has a small dipole moment of 1.1 D. Nitriles, however, have large dipole moments of about 4 D.11,12 Thus, there should be a strong dipole alignment to the ions, which however should be similar for alkyl and aryl nitriles. Other than alkyl nitriles, aryl nitriles can build up CH/π stabilizations or form π-stacks with the many aryl groups of ground and transition states. It is to differences in such weak interaction that we ascribe the observed changes of the rates of epimerization of the complexes (SFe,RC)-[CpFe(Prophos)NCR]PF6 by factors of two to three in both directions on addition of free nitrile. p-Dimethylaminobenzonitrile Complex (SFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]PF6. The epimerization of the pdimethylaminobenzonitrile complex (R Fe ,R C )-[CpFe-

configuration was proposed as an explanation. In the present paper, the same results were obtained for the system (SFe,RC)[CpFe(Prophos)NCEt]PF6/EtCN. However, the epimerization rates of (SFe,RC)-[CpFe(Prophos)NCPh]PF6 in CDCl3 decreased in the presence of PhCN. For a similar retardation in the epimerization of (SRu.RC)-[CpRu(Prophos)Cl], a bimolecular reaction of the unsaturated intermediate (SRu.RC)-[CpRu(Prophos)]+ with increasing amounts of Cl− had been suggested.10 Such a reaction could also be put forward for the retardation of the epimerization of (SFe,RC)-[CpFe(Prophos)NCPh]PF6 in the presence of added PhCN. However, it is the close similarity of alkyl and aryl nitriles which does not allow two completely different types of bimolecular reactions as an explanation of the opposite influence of free nitrile ligands on the rate of epimerization. In addition, as we will show below, the epimerization of (SFe,RC)-[CpFe(Prophos)NCMe]PF6 is even retarded on addition of PhCN, which is not a constituent of the system (SFe,RC)-[CpFe(Prophos)NCMe]PF6/MeCN. D

DOI: 10.1021/acs.organomet.8b00146 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

Figure 3. Left side: Ligand exchange of (SFe,RC)-[CpFe(Prophos)NCMe]PF6 with a 10-fold excess of PhCN in CDCl3 at 293 K: (SFe,RC)[CpFe(Prophos)NCMe]PF6 (black circles); (RFe,RC)-[CpFe(Prophos)NCMe]PF6 (cyan squares); (SFe,RC)-[CpFe(Prophos)NCPh]PF6 (red triangles); and (RFe,RC)-[CpFe(Prophos)NCPh]PF6 (open circles). Right side: Determination of kinetic control by extrapolation of the diastereomer ratio (RFe,RC):(SFe,RC)-[CpFe(Prophos)NCPh]PF6 to time 0.

PhCN, at this time the 31P NMR signal of (SFe,RC)[CpFe(Prophos)NCMe]PF6 had disappeared. In the beginning of the MeCN/PhCN ligand exchange, the situation was different. The concentration of the thermodynamically less stable diastereomer (RFe,RC)-[CpFe(Prophos)NCPh]PF6 increased much faster than that of the thermodynamically more stable diastereomer (SFe,RC)-[CpFe(Prophos)NCPh]PF6. This is due to the fact that the early stages of the ligand exchange reaction are under kinetic control (Figure 2). The kinetic control is indicated by the difference ΔG⧧ of the activation energies of the bimolecular reactions of the 16electron intermediates (R Fe ,R C )- and (S Fe ,R C )-[CpFe(Prophos)]+ with PhCN (top of Figure 2). The thermodynamic control of the (RFe,RC)/(SFe,RC) diastereomer ratio of the benzonitrile complex (8:92) at equilibrium shows up in the energy difference ΔG (bottom of Figure 2). At each point of the time scale in Figure 3, the diastereomer ratio is determined by the kinetic control in the formation and the amount of epimerization of the products (RFe,RC)- and (SFe,RC)-[CpFe(Prophos)NCPh]PF6. For each of the 25 measurement points, we calculated the (RFe,RC):(SFe,RC) diastereomer ratio and plotted it versus the reaction time (Figure 3, right side). Although the calculations for low conversions were not very accurate, extrapolation to time 0 gave the result 19:81 for the contribution of the kinetic control. This is the highest diastereomer ratio achievable in the MeCN/ PhCN ligand exchange under the given reaction conditions. During the reaction, the diastereomer ratio changed, approaching the equilibrium value due to the epimerization of (RFe,RC)and (SFe,RC)-[CpFe(Prophos)NCPh]PF6. In Figure 2 the barrier of pyramidal inversion of the 16electron intermediates (R Fe ,R C )- and (S Fe ,R C )-[CpFe(Prophos)]+ is lower than the barriers of the bimolecular reactions intermediate + PhCN, because in substitution reactions different (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCMe]PF6 ratios had afforded constant diastereomer ratios of configurationally stable products.3 Thus, with respect to the bimolecular reactions intermediate + PhCN, the pyramidal 3d intermediates (RFe,RC)- and (SFe,RC)-[CpFe(Prophos)]+ are in a mobile equilibrium. For the corresponding 4d intermediates (RRu,RC)- and (SRu,RC)-[CpRu(Prophos)]+ this is different.10 A

(Prophos)NC(p-C6H4NMe2)]PF6 in CDCl3 at 293 K in Figure 1 approaches the equilibrium from the side of the enriched (RFe,RC)-diastereomer (blue curves). The data closely join those of the corresponding benzonitrile complex, albeit with a strongly reduced rate due to the electron-donating effect of the dimethylamino substituent (Table 3). While the half-life of the benzonitrile complex in CDCl3 at 293 K was 162 min, for the pdimethylaminobenzonitrile complex under the same condition it was up to 760 min. The temperature dependence of the epimerization rate of (S Fe ,R C )-[CpFe(Prophos)NC(pC6H4NMe2)]PF6, was as expected and the results of the epimerization in the presence of free dimethylaminobenzonitrile were in line with those of the benzonitrile complex (Table 3). The slightly electron-donating methyl substituent placed the tolunitrile complex (S F e ,R C )-[CpFe(Prophos)NC(pC6H4Me)]PF6 between the benzonitrile and the p-dimethylaminobenzonitrile complex with respect to its kinetic data (Table 3, last line). The 31P NMR spectra of the epimerization of the complexes (S F e ,R C )-[CpFe(Prophos)NC(pC 6 H 4 OMe)]PF 6 and (S Fe ,R C )-[CpFe(Prophos)NC(pC6H4NO2)]PF6 were broadened and did not allow the extraction of kinetic data. Kinetic and Thermodynamic Control in the Ligand Exchange MeCN/ArCN. We investigated the MeCN/PhCN ligand exchange in (SFe,RC)-[CpFe(Prophos)NCMe]PF6 by 31P NMR spectroscopy in the presence of a 10-fold excess of PhCN in CDCl3 at 293 K (Figure 3, left side). The decrease of the concentration of (SFe,RC)-[CpFe(Prophos)NCMe]PF6 was accompanied by the increase of (RFe,RC)- and (SFe,RC)[CpFe(Prophos)NCPh]PF6. The concentration of (RFe,RC)[CpFe(Prophos)NCMe]PF6 remained below the level of detection. The MeCN/PhCN ligand exchange started under kinetic control. However, as the products (RFe,RC)- and (SFe,RC)[CpFe(Prophos)NCPh]PF6 are configurationally labile at the iron center, they themselves were subjected to epimerization. After 160 h, more than 10 half-lives of (SFe,RC)-[CpFe(Prophos)NCMe]PF6, the equilibrium was established. The diastereomer ratio (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCPh]PF6 at equilibrium was 8:92. Due to the 10-fold excess of E

DOI: 10.1021/acs.organomet.8b00146 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

Figure 4. Left side: Ligand exchange of (SFe,RC)-[CpFe(Prophos)NCMe]PF6 with a 10-fold excess of (p-C6H4NMe2)CN in CDCl3 at 293 K: (SFe,RC)-[CpFe(Prophos)NCMe]PF6 (black circles); (RFe,RC)-[CpFe(Prophos)NCMe]PF6 (cyan squares); (SFe,RC)-[CpFe(Prophos)NC(pC6H4NMe2)]PF6 (red triangles); and (RFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]PF6 (open circles). Right side: Determination of kinetic control by extrapolation of the diastereomer ratio (RFe,RC):(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]PF6 to time 0.

stereomer equilibria. For slowly epimerizing systems the (RFe,RC) diastereomers can be enriched under kinetic control.

high barrier for pyramidal inversion allowed substitution reactions with dominant retention of the Ru configuration. Due to the slow epimerization of the product (SFe,RC)[CpFe(Prophos)NC(p-C 6 H 4 NMe 2 )]PF 6 , the MeCN/(pC 6 H 4 NMe 2 )CN exchange in (S Fe ,R C )-[CpFe(Prophos)NCMe]PF6 (Figure 4, left side) resulted in a higher enrichment of the thermodynamically less stable diastereomer (RFe,RC)[CpFe(Prophos)NC(p-C6H4NMe2)]PF6 during the phase of kinetic control. Extrapolation to time 0 gave a diastereomer ratio (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]PF 6 = 35:65 (Figure 4, right side). The MeCN/(pC6H4Me)CN ligand exchange in (SFe,RC)-[CpFe(Prophos)NCMe]PF6 was consistent with that of PhCN and (pC6H4NMe2)CN. It afforded a diastereomer ratio (RFe,RC)/ (SFe,RC)-[CpFe(Prophos)NC(p-C6H4Me)]PF6 = 29:71 (Figure S29). Figures 3 and 4 show the disappearance of (SFe,RC)[CpFe(Prophos)NCMe]PF6 in the ligand exchange reactions with a 10-fold excess of PhCN and (p-C6H4NMe2)CN in CDCl3 at 293 K. In both cases, the half-lives of the disappearance of (SFe,RC)-[CpFe(Prophos)NCMe]PF6 are much longer than in the epimerization of (SFe,RC)-[CpFe(Prophos)NCMe]PF6, which had been 96 min. In the PhCN system of Figure 3, the half-life is 462 min, and in the (pC6H4NMe2)CN system of Figure 4, it is 385 min. The explanation for this retardation is dipole alignment, π-stack formation, and so on (see above). The interesting point here is that the free ligands, PhCN and (p-C6H4NMe2)CN, added in 10-fold excess, are not constituents of the system (SFe,RC)[CpFe(Prophos)NCMe]PF6/MeCN.

■

EXPERIMENTAL SECTION

General. 1H/31P{1H} NMR: Bruker Avance 400 (400/162 MHz) or Bruker Avance III 500 (500/202 MHz, T = 293 K), tetramethylsilane as internal standard and H3PO4 as external standard. MS: Agilent Q-TOF 6540 UHD or ThermoQuest Finnigan TSQ 7000. IR-JASCO FT/IR4100ST. All manipulations were carried out in purified nitrogen. All solvents were dried and distilled before use according to standard procedures. (R)-Prophos was purchased from Wako Pure Chem. Ind. Ltd. Propionitrile and arylnitriles were purchased from Kanto Chem. Co. Inc. In the 1H NMR spectra, we differentiate major and minor diastereomers in the following way: major (SFe,RC)-diastereomer, minor (RFe,RC)-diastereomer in brackets, if distinguishable. In the 31P{1H} NMR spectra, the differentiation is as follows: major (SFe,RC)-diastereomer, minor (RFe,RC)-diastereomer in brackets. General Procedure for the Synthesis of [CpFe(Prophos)NCR]X (X = PF6, I). To a solution of (RFe,RC)/(SFe,RC)-[CpFe(Prophos)I]1 5:95 (100 mg, 0.15 mmol) in chloroform (20 mL) was added RCN (10 equiv) in the presence or absence of NH4PF6 (10 equiv) at room temperature. Instead of chloroform, solvents such as THF can also be used. After stirring for 2 h, the solvent was removed, and the residue was washed with diethyl ether and crystallized as indicated for each compound. (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](propanenitrile)iron]iodide, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCEt]I. Crystallization from dichloromethane/hexane afforded (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCEt]I 5:95 as orange crystals in 92% yield. Diastereomerically pure (SFe,RC)-[CpFe(Prophos)NCEt]I, suitable for X-ray analysis, was obtained by crystallization from methanol. IR (KBr): ν 2256 cm−1 (NC). 1H NMR (CDCl3, 293 K): δ 7.99− 7.27 (m, 20H, Ar−H), 4.30 (s, 5H, Cp−H), [4.33 (s, 5H, Cp−H)], 3.11−2.98 (m, 1H, CH), 2.31−2.23 (m, 3H, CH and CH2), 2.02−2.00 (m, 1H, CH), 1.23 (dd, 3H, 3JP−H = 12.7 Hz, 3JH−H = 4.5 Hz, CH3), 0.56 (t, 3H, 3JH−H = 7.5 Hz, CH3), [0.46 (t, 3JH−H = 7.9 Hz, CH3)]. 31 1 P{ H} NMR (CDCl3, 293 K): δ 106.57 (d, 1P, 2JP−P = 43.7 Hz), [109.10 (d, 1P, 2JP−P = 31.1 Hz)], 83.94 (d, 1P, 2JP−P = 43.7 Hz), [97.78 (d, 1P, 2JP−P = 31.1 Hz)]. ES-MS (CH2Cl2/MeCN): m/z 588 ([CpFe(Prophos)NCEt]+, 100), 533 ([CpFe(Prophos)]+, 56). ESIHRMS: Calcd for the cation C35H36FeNP2+ 588.1667; found m/z 588.1672. Anal. Calcd for C35H36FeNIP2 (715.3): C, 58.76; H, 5.07; N, 1.96. Found: C, 58.76; H, 5.04; N, 1.99 (diasteromer mixture). (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](propanenitrile)iron]hexafluorophosphate, (RFe,RC)/

■

CONCLUSION In chiral-at-metal complexes (R Fe ,R C )/(S Fe ,R C )-[CpFe(Prophos)NCR]X (X = I, PF6); R = Et, Ph, p-substituted Ph), the nitrile ligands tend to dissociate, allowing substitution reactions. The rate of dissociation is controlled by the inductive effect of the nitrile substituent. Whereas addition of free alkyl nitrile increases the rate of epimerization with respect to the labile Fe-configuration in alkyl nitrile complexes, addition of free aryl nitriles decreases the rate. Thermodynamic control strongly favors (SFe,RC)-[CpFe(Prophos)NCR]X in the diaF

DOI: 10.1021/acs.organomet.8b00146 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

IR (KBr): ν 2228 cm−1 (NC). 1H NMR (CDCl3, 293 K): δ 8.07− 6.54 (m, 24H, Ar−H), 4.36 (s, 5H, Cp−H), [4.34 (s, 5H, Cp−H)], 3.82 (s, 3H, OMe), [3.78 (s, 3H, OMe)], 3.26−3.06 (m, 1H, CH), 2.17−2.06 (m, 2H, CH), 1.24 (dd, 3H, 3JP−H = 9.3 Hz, 3JH−H = 5.4 Hz, CH3), [0.66 (dd, 3H, 3JP−H = 13.4 Hz, 3JH−H = 7.1 Hz, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 106.01 (d, 1P, 2JP−P = 45.6 Hz), [108.98 (d, 1P, 2JP−P = 29.7 Hz)], 83.81 (d, 1P, 2JP−P = 45.6 Hz), [97.62 (d, 1P, 2 JP−P = 29.7 Hz)]. ES-MS (CH2Cl2/MeCN) m/z 666 ([CpFe(Prophos)NC(p-C6H4OMe)]+, 100), 533 ([CpFe(Prophos)]+, 67). Anal. Calcd for C40H38FeINOP2·CH3OH (825.5): C, 59.66; H, 5.13; N, 1.70. Found: C, 59.89; H, 4.80; N, 1.65 (pure diastereomer). (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](4-methoxybenzonitrile)iron]hexafluorophosphate, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4OMe)]PF6. Crystallization from dichloromethane/ether/hexane afforded (RFe,RC)/(SFe,RC)[CpFe(Prophos)NC(p-C6H4OMe)]PF6 8:92 as red crystals in 88% yield. Diastereomerically pure (SFe,RC )-[CpFe(Prophos)NC(pC6H4OMe)]PF6·3CHCl3, suitable for X-ray analysis, was obtained by crystallization from chloroform/ether. IR (KBr): ν 2221 (CN), 842 cm−1 (PF). 1H NMR (CDCl3, 293 K): δ 7.92−6.52 (m, 24H, Ar−H), 4.34 (s, 5H, Cp−H), 3.81 (s, 3H, OMe), [3.87 (s, 3H, OMe)], 3.15−3.03 (m, 1H, CH), 2.17−2.07 (m, 2H, CH), 1.22 (br s, 3H, CH3), [0.66 (br s, 3H, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 104.74 (d, 1P, 2JP−P = 43.9 Hz), [107.67 (d, 1P, 2 JP−P = 30.6 Hz)], 82.37 (d, 1P, 2JP−P = 43.9 Hz), [97.23 (d, 1P, 2JP−P = 30.6 Hz)], −144.25 (septet, 1P, 1JP−F = 712.5 Hz). ESI-HRMS: Calcd for the cation C40H38FeNOP2+ 666.1778; found m/z 666.1799. Anal. Calcd for C40H38F6FeNOP3·3CHCl3 (1169.6): C, 44.16; H, 3.53; N, 1.20. Found: C, 44.57; H, 3.65; N, 1.28 (pure diastereomer). (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](4-(N,N-dimethylamino)benzonitrile)iron]iodide, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]I. The residue was (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]I 17:83 (red crystals in quantitative yield). Diastereomerically pure (SFe,RC)[CpFe(Prophos)NC(p-C6H4NMe2)]I·MeOH, suitable for X-ray analysis, was obtained by crystallization from methanol/ether. 1 H NMR (CDCl3, 293 K): δ 8.03−7.04 (m, 20H, Ar−H), 6.42 (d, 2H, 3JH−H = 9.3 Hz, Ar−H), [6.64 (d, 2H, 3JH−H = 9.1 Hz, Ar−H)], 6.35 (d, 2H, 3JH−H = 9.3 Hz, Ar−H), [6.50 (d, 2H, 3JH−H = 9.1 Hz, Ar−H)], 4.31 (s, 5H, Cp−H), [4.28 (s, 5H, Cp−H)], 3.22−3.00 (m, 1H, CH), [2.89−2.76 (m, 1H, CH)], 3.02 (s, 6H, NMe2), [2.97 (6H, s, NMe2)], 2.20−1.95 (m, 2H, CH), 1.23 (dd, 3H, 3JP−H = 10.3 Hz, 3 JH−H = 6.1 Hz, CH3), [0.65 (dd, 3H, 3JP−H = 13.4 Hz, 3JH−H = 7.3 Hz, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 106.04 (d, 1P, 2JP−P = 45.2 Hz), [108.78 (d, 1P, 2JP−P = 30.9 Hz)], 84.03 (d, 1P, 2JP−P = 45.2 Hz), [97.72 (d, 1P, 2JP−P = 30.9 Hz)]. ES-MS (CH2Cl2/MeCN): m/z 679 ([CpFe(Prophos)NC(p-C 6 H 4 NMe 2 )] + , 100), 533 ([CpFe(Prophos)]+, 10). Anal. Calcd for C41H41FeIN2P2·CH3OH (838.5): C, 60.16; H, 5.41; N, 3.34. Found: C, 60.33; H, 5.10; N, 3.13 (pure diastereomer). (RFe,RC)/(SFe,RC)-(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](4-(N,N-dimethylamino)benzonitrile)iron hexafluorophosphate, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]PF6. The residue was (R Fe ,R C )/(S Fe ,R C )-[CpFe(Prophos)NC(pC6H4NMe2)]PF6 18:82 (red crystals in a quantitative yield). Diastereomerically pure (S F e ,R C )-[CpFe(Prophos)NC(pC6H4NMe2)]PF6·MeOH, suitable for X-ray analysis, was obtained by crystallization from MeOH/diethyl ether. IR (KBr): ν 2207 (NC), 844 cm−1 (P−F). 1H NMR (CDCl3, 293 K): δ 7.94−7.31 (m, 20H, Ar−H), 6.40 (d, 2H, 3JH−H = 9.3 Hz, Ar− H), [6.64 (d, 2H, 3JH−H = 9.1 Hz, Ar−H)], 6.35 (d, 2H, 3JH−H = 9.3 Hz, Ar−H), [6.52 (d, 2H, 3JH−H = 9.1 Hz, Ar−H)], 4.31 (s, 5H, Cp− H), [4.28 (s, 5H, Cp−H)], 3.22−3.00 (m, 1H, CH), [2.89−2.76 (m, 1H, CH)], 3.02 (s, 6H, NMe2), [2.97 (6H, s, NMe2)], 2.20−1.95 (m, 2H, CH), 1.23 (dd, 3H, 3JP−H = 10.3 Hz, 3JH−H = 6.1 Hz, CH3), [0.65 (dd, 3H, 3JP−H = 13.4 Hz, 3JH−H = 7.3 Hz, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 104.72 (d, 1P, 2JP−P = 45.2 Hz), [107.50 (d, 1P, 2 JP−P = 31.1 Hz)], 82.55 (d, 1P, 2JP−P = 45.2 Hz), [96.37 (d, 1P, 2JP−P = 31.1 Hz)], −144.26 (septet, 1P, 1JP−F = 713.1 Hz). ES-MS: m/z 679 ([CpFe(Prophos)NC(p-C6H4NMe2)]+, 100). ESI-HRMS: Calcd for

(SFe,RC)-[CpFe(Prophos)NCEt]PF6. Crystallization from dichloromethane/hexane afforded (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCEt]PF6 2:98 in 78% yield as orange crystals. IR (KBr): ν 2259 (NC), 734 cm−1 (PF). 1H NMR (CDCl3, 293 K): δ 7.85−7.27 (m, 20H, Ar−H), 4.25 (s, 5H, Cp−H), [4.20 (s, 5H, Cp− H)], 3.09−2.92 (m, 1H, CH), 2.04−2.02 (m, 2H, CH), 1.95 (q, 2H, 3 JH−H = 7.6 Hz, CH2), 1.20 (dd, 3H, 3JP−H = 10.8 Hz, 3JH−H = 6.0 Hz, CH3), [0.64 (dd, 3H, 3JP−H = 12.4 Hz, 3JH−H = 6.8 Hz, CH3)], 0.51 (t, 3H, 3JH−H = 7.6 Hz, CH3), [0.41 (t, 3JH−H = 7.6 Hz, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 105.15 (d, 1P, 2JP−P = 43.9 Hz), [107.74 (d, 1P, 2JP−P = 31.3 Hz)], 82.42 (d, 1P, 2JP−P = 43.9 Hz), [96.17 (d, 1P, 2 JP−P = 31.3 Hz)], −144.34 (septet, 1JP−F = 713.5 Hz, PF6). ESIHRMS: Calcd for the cation C35H36FeNP2+ 588.1672; found m/z 588.1674. Anal. Calcd for C35H36F6FeNP3 (733.4): C, 57.32; H, 4.95; N, 1.91. Found: C, 57.27; H, 4.86; N, 1.90 (diasteromer mixture). (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](benzonitrile)iron]iodide/Hexafluorophosphate, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NCPh]X (X = I, PF6). Yields, crystallization conditions, spectra, and elemental analysis were published in the Supporting Information of ref 9. (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](4-methylbenzonitrile)iron]iodide, (RFe,RC)/(SFe,RC)[CpFe(Prophos)NC(p-C6H4Me)]I. Crystallization from dichloromethane/ether afforded (R Fe,R C )/(S Fe,R C )-[CpFe(Prophos)NC(pC6H4Me)]I 37:63 as red crystals in 58% yield. Diastereomerically pure (SFe,RC)-[CpFe(Prophos)NC(p-C6H4Me)]I·MeOH, suitable for X-ray analysis, was obtained by crystallization from methanol/ether. IR (KBr): ν 2228 cm−1 (NC). 1H NMR (CDCl3, 293 K): δ 8.08− 7.00 (m, 22H, Ar−H), 6.48 (d, 2H, 3JH−H = 6.1 Hz, Ar−H), [6.67 (d, 2H, 3JH−H = 6.9 Hz, Ar−H)], 4.38 (s, 5H, Cp−H), [4.35 (s, 5H, Cp− H)], 3.31−3.29 (m, 1H, CH), [3.60−3.45 (m, 1H. CH)], 2.34 (s, 3H, Me), [2.30 (s, 3H, Me)], 2.20−2.02 (m, 2H, CH × 2), [2.91−2.79 (m, 1H, CH)], 1.29−1.21 (br d, 3H, CH3), [0.66 (dd, 3H, 3JP−H = 13.0 Hz, 3JH−H = 5.4 Hz, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 106.37 (d, 1P, 2JP−P = 45.6 Hz), [109.50 (d, 1P, 2JP−P = 29.7 Hz)], 83.72 (d, 1P, 2JP−P = 45.6 Hz), [97.58 (d, 1P, 2JP−P = 29.7 Hz)]. ES-MS (CH2Cl2/MeOH) m/z 650 ([CpFe(Prophos)NC(p-C6H4Me)]+, 100). Anal. Calcd for C40H38FeINP2·1/2(CH2Cl2) (819.9): C, 59.32; H, 4.80; N, 1.71. Found: C, 59.89; H, 4.80; N, 1.66 (diasteromer mixture). (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](4-methylbenzonitrile)iron]hexafluorophosphate, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4Me)]PF6. Crystallization from dichloromethane/methanol/ether afforded (RFe,RC)/(SFe,RC)[CpFe(Prophos)NC(p-C6H4Me)]PF6 5:95 as red crystals in quantitative yield. Diastereomerically pure (SFe,RC)-[CpFe(Prophos)NC(pC6 H4 Me)]PF6 , suitable for X-ray analysis, was obtained by crystallization from CH2Cl2/ethanol/ether. IR (KBr): ν 2214 (NC), 839 cm−1 (PF). 1H NMR (CDCl3, 293 K): δ 7.93−7.24 (m, 20H, Ar−H), 7.05 (br d, 2H, 3JH−H = 6.8 Hz, Ar−H), 6.46 (d, 2H, 3JH−H = 6.8 Hz, Ar−H), [6.67 (d, 2H, 3JH−H = 6.9 Hz, Ar−H)], 4.35 (s, 5H, Cp−H), [4.30 (s, 5H, Cp−H)], 3.19−3.02 (m, 1H, CH), 2.33 (s, 3H, CH3), [2.42 (s, 3H, CH3)], 2.12−2.08 (m, 2H, CH) 1.23−1.20 (br s, 3H, CH3), [0.67 (br s, 3H, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 104.68 (d, 1P, 2JP−P = 44.2 Hz), [107.55 (d, 1P, 2JP−P = 30.3 Hz)], 82.24 (d, 1P, 2JP−P = 44.2 Hz), [96.19 (d, 1P, 2 JP−P = 30.3 Hz)], −144.18 (septet, 1P, 1JP−F = 713.3 Hz). ES-MS (CH2Cl2/MeOH): m/z 650 ([CpFe(Prophos)NC(p-C6H4Me)]+, 100). ESI-HRMS: Calcd for the cation C40H38FeNP2+ 650.1829; found m/z 650.1826. Anal. Calcd for C40H38F6FeNP3·1/2(CH2Cl2) (838.0): C, 58.05; H, 4.69; N, 1.67. Found: C, 58.32; H, 4.63; N, 1.65 (diasteromer mixture). (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](4-methoxybenzonitrile)iron]iodide, (RFe,RC)/(SFe,RC)[CpFe(Prophos)NC(p-C6H4OMe)]I. Crystallization from dichloromethane/ether afforded (R Fe,R C )/(S Fe,R C )-[CpFe(Prophos)NC(pC6H4OMe)]I 4:96 as red crystals in quantitative yield. Diastereomerically pure (SFe,RC)-[CpFe(Prophos)NC(p-C6H4OMe)]I·MeOH, suitable for X-ray analysis, was obtained by crystallization from methanol/ ether. G

DOI: 10.1021/acs.organomet.8b00146 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics the cation C41H41FeN2P2+ 679.2094; found m/z 679.2089. Anal. Calcd for C42H45F6FeN2OP3 (856.6): C, 59.89; H, 5.30; N, 3.40. Found: C, 58.58; H, 4.92; N, 3.27 (diastereomer mixture). (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](4-nitrobenzonitrile)iron]iodide, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NO2)]I. Crystallization from dichloromethane/ ether afforded (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NO2)]I 4:96 as purple crystals in 51% yield. Diastereomerically pure (SFe,RC)[CpFe(Prophos)NC(p-C6H4NO2)]I·EtOH, suitable for X-ray analysis, was obtained by crystallization from dichloromethane/ether/ethanol. IR (KBr): ν 2211 (NC), 1520 (NO2), 1339 cm−1 (NO2). 1H NMR (CDCl3, 293 K): δ 8.38−7.04 (m, 24H, Ar−H), 4.54 (s, 5H, Cp−H), [4.28 (s, 5H, Cp−H)], 3.35−3.126 (m, 1H, CH), 2.43−2.07 (m, 2H, CH), 1.27 (dd, 3H, 3JP−H = 10.8 Hz, 3JH−H = 6.6 Hz, CH3), [0.66 (dd, 3H, 3JP−H = 13.0 Hz, 3JH−H = 7.1 Hz, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 105.99 (d, 1P, 2JP−P = 41.6 Hz), [109.56 (d, 1P, 2JP−P = 29.6 Hz)], 83.50 (d, 1P, 2JP−P = 41.6 Hz), [97.67 (d, 1P, 2JP−P = 29.6 Hz)]. ES-MS (CH2Cl2/MeOH/NH4OAc) m/z 681 ([CpFe(Prophos)NC(p-C6H4NO2)]+, 100), 533 ([CpFe(Prophos)]+, 49). Anal. Calcd for C39H35FeIN2O2P2·CH2Cl2 (893.4): C, 53.78; H, 4.17; N, 3.14. Found: C, 53.62; H, 4.11; N, 3.03 (diastereomer mixture). (RFe,RC)/(SFe,RC)-[(η5-Cyclopentadienyl)[bis(diphenylphosphanyl)propane-κP](4-nitrobenzonitrile)iron]hexafluorophosphate, (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NO2)]PF6. Crystallization from dichloromethane/ether afforded (RFe,RC)/(SFe,RC)-[CpFe(Prophos)NC(p-C6H4NO2)]PF6 4:96 as purple crystals in 34% yield. The X-ray data of diastereomerically pure (SFe,RC)-[CpFe(Prophos)NC(p-C6H4NO2)]PF6 have been previously published.8 IR (KBr): ν 2211 (NC), 1520 (NO2), 1339 cm−1 (NO2). 1H NMR (CDCl3, 293 K): δ 8.04−7.20 (m, 24H, Ar−H), 4.54 (s, 5H, Cp−H), [4.28 (s, 5H, Cp−H)], 3.35−3.12 (m, 1H, CH), 2.43−2.07 (m, 2H, CH), 1.27 (dd, 3H, 3JP−H = 10.8 Hz, 3JH−H = 6.6 Hz, CH3), [0.66 (dd, 3H, 3JP−H = 13.0 Hz, 3JH−H = 7.1 Hz, CH3)]. 31P{1H} NMR (CDCl3, 293 K): δ 105.99 (d, 1P, 2JP−P = 41.6 Hz), [109.56 (d, 1P, 2JP−P = 29.6 Hz)], 83.50 (d, 1P, 2JP−P = 41.6 Hz), [97.67 (d, 1P, 2JP−P = 29.6 Hz)]. ES-MS (CH2Cl2/MeOH/NH4OAc): m/z 681 ([CpFe(Prophos)NC(p-C 6 H 4 NO 2 )] + , 100). ESI-HRMS: Calcd for the cation C39H35FeN2O2P2+ 681.1523; found m/z 681.1518. X-ray Analyses. Crystal and refinement data are given in Table S1. X-ray data were collected on a Rigaku RAXIS-RAPID imaging plate diffractometer using Mo Kα (graphite monochromated, λ = 0.71073 Å, fine focus tube, ω-scan) radiation at 173 K. The structures were solved by SIR200413 or SIR9714 and refined by full-matrix least-squares on F2 by SHELX 2016/6.15 All H atoms were included at calculated positions. CCDC 1527570 {for (SFe,RC)-[CpFe(Prophos)NCEt]I· MeOH}, 1527571 {for (SFe,RC)-[CpFe(Prophos)NC(p-C6H4Me)]I· MeOH},1527572{for (SFe,RC)-[CpFe(Prophos)NC(p-C6H4OMe)]I· MeOH}, 1527573 {for (SFe,RC)-[CpFe(Prophos)NC(p-C6H4NMe2)]I·MeOH}, 1527574 {for (S F e ,R C )-[CpFe(Prophos)NC(pC6H4NO2)]I·EtOH}, 1527575 {for (SFe,RC)-[CpFe(Prophos)NC(pC6H4Me)]PF 6}, 1527576 {for (SFe,RC)-[CpFe(Prophos)NC(pC 6 H 4 OMe)]PF 6 ·3CHCl 3 }, and 1527577{for (S Fe ,R C )-[CpFe(Prophos)NC(p-C6H4NMe2)]PF6·MeOH} contain the supplementary crystallographic data for this paper.

■

Accession Codes

CCDC 1527570−1527577 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Fax: +49941-9434439 (H.B.). *E-mail: [email protected]. Fax: +81-47-474-2579 (T.T.). ORCID

Takashi Tsuno: 0000-0003-0034-0710 Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Brunner, H.; Kurosawa, T.; Muschiol, M.; Tsuno, T.; Balazs, G.; Bodensteiner, M. Organometallics 2013, 32, 4904−4911. (2) Brunner, H.; Ike, H.; Muschiol, M.; Tsuno, T.; Umegaki, N.; Zabel, M. Organometallics 2011, 30, 414−421. (3) Brunner, H.; Ike, H.; Muschiol, M.; Tsuno, T.; Koyama, K.; Kurosawa, T.; Zabel, M. Organometallics 2011, 30, 3666−3676. (4) Brunner, H.; Kurosawa, T.; Muschiol, M.; Tsuno, T.; Ike, H. Organometallics 2012, 31, 3395−3401. (5) Lecomte, C.; Dusausoy, Y.; Protas, J.; Tirouflet, J.; Dormond, A. J. Organomet. Chem. 1974, 73, 67−76. (6) Brunner, H. Enantiomer 1997, 2, 133−134. (7) Brunner, H.; Tsuno, T.; Bodensteiner, M. Organometallics 2014, 33, 2257−2265. (8) Wenseleers, W.; Goovaerts, E.; Hepp, P.; Garcia, M. H.; Robalo, M. P.; Dias, A. R.; Piedade, M. F. M.; Duarte, M. T. Chem. Phys. Lett. 2003, 367, 390−397. (9) Brunner, H.; Muschiol, M.; Tsuno, T.; Ike, H.; Kurosawa, T.; Koyama, K. Angew. Chem., Int. Ed. 2012, 51, 1067−1070. (10) Brunner, H.; Muschiol, M.; Tsuno, T.; Takahashi, T.; Zabel, M. Organometallics 2008, 27, 3514−3525. (11) Sato, K.; Ohkubo, Y.; Moritsu, T.; Ikawa, S.; Kimura, M. Bull. Chem. Soc. Jpn. 1978, 51, 2493−2495. (12) Kawski, A.; Kukliński, B.; Bojarski, P. Chem. Phys. Lett. 2006, 419, 309−312. (13) Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 2005, 38, 381−388. (14) 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. (15) Sheldrick, G. M. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3−8.

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.8b00146. Crystallographic data of 8 complexes (SFe,RC)-[CpFe(Prophos)NCR]X, 1H NMR spectra and 31P{1H} NMR spectra of the complexes, ORTEP drawings, ligand exchange of (SFe,RC)-[CpFe(Prophos)NCMe]PF6 with a 10-fold excess of (p-C6H4Me)CN in CDCl3 at 293 K (PDF) H

DOI: 10.1021/acs.organomet.8b00146 Organometallics XXXX, XXX, XXX−XXX