A New Route to Phosphaalkene Chelate Complexes: SET

Aug 22, 2013 - Andreas W. Kyri , Gregor Schnakenburg , and Rainer Streubel ... Alexandra B. Grimm , Sloane Evariste , Arnold L. Rheingold , Curtis E. ...
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A New Route to Phosphaalkene Chelate Complexes: SET Deoxygenation of Oxaphosphirane Complexes Followed by Intramolecular CO Substitution Melina Klein, Carolin Albrecht, Gregor Schnakenburg, and Rainer Streubel* Institut für Anorganische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany S Supporting Information *

ABSTRACT: Synthesis and SET deoxygenation of oxaphosphirane complexes 1a−e of the general formula [(CO)5M{R1R2C−O-PCH(SiMe3)2}] (1a: M = W, R1 = Me, R2 = o-py; 1b: M = W, R1 = H, R2 = o-py; 1c: M = Mo, R1 = H, R2 = o-py; 1d: M = Cr, R1 = H, R2 = o-py; 1e: M = W, R1,R2 = Me) using the system TiCpCl3/Zn led to the formation of phosphaalkene complexes 2a−e. In the case of 2e, [{CpTi(Cl)O}4] (4), a product of the SET deoxygenation process, was isolated. Subsequent CO extrusion/substitution of 2a−d yielded the phosphaalkene chelate complexes 3a−d under mild conditions. NMR, IR and MS data as well as X-ray structures of complexes 1a,b, 2e, and 3a,b will be reported.

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plexes are known since the early 90s, this might seem surprising at first,9 but only the recent advent of a new facile protocol10 has enabled systematic, broad research of these relatives of oxiranes (epoxides). Here, the first systematic application of the SET deoxygenation protocol on oxaphosphirane complexes is reported, allowing a new access to a series of chelate phosphaalkene complexes that are formed via selective transformation of transient phosphaalkene complexes in a one-pot-like reaction. First, oxaphosphirane complexes 1a−d were synthesized using the standard methodology.10 As observed before, mixtures of three diastereomers were obtained in the case of 1a−d, which could not be separated, but unequivocally characterized.11 These mixtures of complexes 1a−d were then treated with the TiCpCl3/Zn system in THF under conditions described before8 (Scheme 2). In all reactions the formation of isomeric phosphaalkene complexes 2a−d was observed by 31P NMR spectroscopy; the ratios were determined by 31P{1H} NMR spectroscopy to 0.3:1.0:0.9 (2a), 1.0:0.1:0.01 (2b), 1.0:0.2 (2c), 1.0:0.02:0.01 (2d). As proposed before,8 the formation of oligomers of the type [{CpTi(O)Cl}n] was assumed but could not be unequivocally determined (but see the case of 2e). Surprisingly, CO substitution occurred rapidly in most cases to yield the chelate complexes 3a−d (Scheme 2). The overall reactions depended from the steric demand of the substituents, the metal and/or metal-to-phosphorus bond distance: in the case of 2a the elimination of CO was fast at room temperature, and after two days the conversion to give 3a was completed. In comparison, the elimination of CO from 2b was very slow, and after two days only 17% of 3b were formed, and the reaction

n comparison to ubiquitous phosphine ligands, the chemistry of phosphaalkenes,1,2 in general, and their coordination chemistry, in particular, is far less developed. Although examples of η2-binding modes of phosphaalkenes to transition metals are known (II), complexes having an η1 coordination mode (I) (through the lone pair) are more common.3 Despite first reports4 on catalytic applications of these compounds, complexes with chelating bonding motifs (III)5 are still very scarce (Scheme 1). Scheme 1. Binding Modes of Phosphaalkenes to Transition Metal Complexesa

a

Lines denote organic substituents.

On the other hand, chelating phosphaalkene complexes III are comparable to 2-pyridyl-phosphines, for which complex formation has been described.6 Here, the first step was ligation of phosphorus, followed by additional coordination of the nitrogen center, as revealed from a downfield shifted resonance in the 31P NMR spectrum. In general, phosphaalkene derivatives are synthesized first, using a wide range of PC bond-forming methodologies, and then ligated to the metal center. But some examples of rearrangement reactions occurring in the coordination sphere of the metal that lead to PC bond formation7 have been described, too. Recently, a first example of a SET oxaphosphirane deoxygenation using in situ formed Ti(III) complexes was described in a preliminary study that offers a new path to η1 phosphaalkene complexes.8 Given that oxaphosphirane com© 2013 American Chemical Society

Received: July 3, 2013 Published: August 22, 2013 4938

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Scheme 2. Formation and Subsequent Reaction of Diastereomeric Mixtures of 1a−d with TiCpCl3/Zn in THF

was finished after one month at room temperature. In the case of 2c already 92% of 3c was formed after three hours, and in the case of 2d the conversion to 3d was not finished after two months at room temperature (29%). Unfortunately, gentle heating (35 °C, 3 h) of a THF reaction solution of complex 2d did not yield the chelate complex 3d but led to unidentified decomposition products. As a consequence, only 31P NMR data of 2a,c could be obtained from the reaction solutions (Table 1),

center, and one for the two remaining carbon atoms of the CO groups (Table 3). A preliminary study was performed to examine the tendency for CO elimination in the absence of an intramolecular nitrogen donor center, and hence, complex 1e was treated with the TiCpCl3/Zn system in THF under the same conditions (Scheme 3) and obtained 2e, which is structurally confirmed Scheme 3. Reaction of Oxaphosphirane Complex 1e with TiCpCl3/Zn in THF

Table 1. 31P NMR Data (THF-d8) of Phosphaalkene Complexes 2a−2d δ 31P (1JW,P [Hz]) 2a 2b 2c 2d a

215.9 (263.9) 244.6 (269.7) 271.3 303.8

213.8 (266.8) 238.6 (262.2) 266.7 296.4

ratio 200.9 (260.0) 233.3

0.3:1.0:0.9 1.0:0.1:0.01 1.0:0.2 1.0:0.02:0.01

a

291.1

Third isomer not detected.

while it was possible to obtain all NMR spectroscopic data of 2b and 2d. All NMR data for complexes 2a−d are in good agreement with those described before for E,Z phosphaalkene complexes.cf.8 Compared to the precursors 2a−d, the chelate complexes 3a−d revealed a downfield shift of about 70 ppm in the 31P NMR spectra (Table 2). Table 2. 31P NMR Data (THF-d8) of the Complexes 3a−3d 3a δ 31P [ppm] (1JW,P) [Hz] 2,3 JP,H [Hz]

3b

3c

3d

289.9 (268.7)

317.8 (270.1)

335.9

370.9

18.9; 19.4 (dq)

14.95; 17.04 (dd)

16.2; 16.8 (dd)

br

Besides the change of the 31P chemical shifts and tungsten− phosphorus coupling constants, the formation of chelate complexes was clearly reflected by the 1H and 13C NMR data as highlighted by a comparison of complexes 2b and 3b (cf. Table 3). One typical spectroscopic NMR feature of these compounds is the 13C NMR resonance pattern of the CO ligands. In contrast to the typical 2 resonance signals (cis/trans) for M(CO)5L complexes, it displayed 3 resonances: one for the CO positioned trans to phosphorus, one trans to the nitrogen

Figure 1. Molecular structure of 2e (50% probability level) in the crystal; hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): W−P 2.4919(11), P−C1 1.669(5), P−C4 1.825(4), C2−C1−P 119.7(3), C1−P−W 126.45(16), C4−W−P 119.27(14).

by single-crystal X-ray analysis (Figure 1). Complex 2e showed no tendency for CO elimination under these conditions, as was

Table 3. Selected NMR Data (THF-d8) of Complexes 2b and 3b δ 1H [ppm] (2JP,H [Hz]) 2b 3b

δ 13C{1H} [ppm] (1JP,C [Hz])

δ P [ppm] ( JW,P) [Hz] ( JP,H) [Hz]

CH(SiMe3)2

CHP

CH(SiMe3)2

CHP

CO

244.6 (269.7) (16.1) 317.8 (270.1) (15.0, 17.0)

1.63 (7.3) 2.49 (17.0)

8.61 (19.9) 8.13 (14.9)

36.0 (12.2) 30.0 (30.0)

161.5 (47.3) 151.7 (31.0)

196.7 (10.1) cis, 200.6 (29.9) trans 197.8 (10.4) cis, 210.5 (4.7) N-trans, 213.7 (39.1) P-trans

31

1

x

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also the case of other phosphaalkene complexes observed before. In addition to phosphaalkene complex 2e, the CpTi(O) Cl tetramer [{CpTi(Cl)O}4]12 (4) was isolated from the reaction mixture and structurally confirmed by crystal X-ray analysis. This constitutes the first experimental evidence for the titanium species formed in deoxygenation reactions of oxaphosphirane complexes using the TiCpCl3/Zn system. It should be noted that tetramer 4 was previously obtained via hydrolysis of TEMPO-substituted titanium species;13 the crystal structure12 was also reported. The resonances of the tungsten complexes 2a and 2b are slightly downfield shifted compared to the 31P NMR chemical shift of 2e, which appeared as mixture of two P−C atropisomers due to the CH(SiMe3)2 group (2e: 181.1 ppm (95%), (1JW,P = 253.7); 2e′: 172.3 (5%), (1JW,P = 254.5)). As expected, the lighter homologues of tungsten assert a downfield shift of about 30 ppm (2c,d). Single-crystal X-ray structures were obtained for complexes 1a,b (see Supporting Information, Figure S1 and S2), 2e (Figure 1), and 3a,b (Figure 2 and 3); selected data will be discussed hereafter.

Figure 3. Molecular structure of 3b (50% probability level) in the crystal; hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): W−P 2.4312(13), P−C1 1.665(4), P−C7 1.801(5), C1−C2 1.441(6), C2−N 1.366(6), N−W 2.289(3), C1−P− W 108.09(18), N−W−P 74.29(10), C2−C1−P 116.7(4).

Table 4. Selected Bond Lengths of 2e and 3a,b (R = CH(SiMe3)2)

Figure 2. Molecular structure of 3a (50% probability level) in the crystal; hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): W−P 2.4427(6), P−C1 1.678(3), P−C8 1.802(5), C1−C2 1.459(3), C2−N 1.369(3), N−W 2.282(2), C1−P−W 109.51(9), N−W−P 73.53(6), C2−N−W 123.75(16).

interesting. In the case of the P,N-chelate complexes Cl2M{κP,κN-MesPC(Ph)Py} (M = Pd, Pt),5 the P−C1 bond distance was found to be in the same range (M = Pd: 1.672(4) Å, M = Pt: 1.675(3) Å).5 In addition, the same effect on the pyridine substituent was observed, i.e., shortening of the C1− C2 bond (M = Pt: C10−C17: 1.4685 Å, C2−N: 1.373(5) Å).5 The bond angles C1−P−W and C2−C1−P are smaller in the chelating complexes 3a (C1−P−W 109.51(9)°, C2−C1−P 114.4(9)°, N−C2−C1 118.7(2)°) and 3b (C1−P−W 108.09(18)°, C2−C1−P 116.7(4)°, N−C2−C1 118.3(4)°) compared to 2e. This is also in accordance with the data obtained for Cl2M{κP,κN-MesPC(Ph)Py} (M = Pd, Pt) (M = Pd: C1−P−Pd 108.3(1)°, C2−C1−P 112.7(2)°, N−C2−C1 117.6(2)°).5

The crystal structures revealed that, because of the chelate effect, the W−P bonds in 3a and 3b are significantly shortened compared to the terminal phosphaalkene complex 2e (Table 4). Despite of different substituents at the phosphaalkene carbon atom the bond lengths of the P−C double bonds and the P−R bonds are identical in 2e and 3a,b; the N−W bond in 3a and in 3b was found to be comparatively long (Table 4). Also the C1−C2 bond to the pyridine substituent is shortened in complexes 3a,b (cf. Table 4) compared to the oxaphosphirane complexes 1a and 1b (C1−C2: 1a, 1.502(7) Å; 1b, 1.476(7) Å) (see also Supporting Information, Figures S1 and S2). This effect, the π-back-bonding, has been already observed for 2,2′-bipyridine complexes.6a In total, the chelating bonding mode leads to a more distinct nature of the 1-aza-4-phosphabutadiene subunit of the ligands. Although there have been no reports on such group 6 metal complexes, a comparison to other metal complexes seems

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CONCLUSIONS Facile synthesis and deoxygenation of oxaphosphirane complexes, followed by CO ligand displacement, allowed selective access to a set of chelate phosphaalkene complexes of group 6 metal carbonyls. 31P {1H} NMR reaction monitoring clearly revealed the formation of transient phosphaalkene complexes. Structural studies showed that the chelating bonding mode is 4940

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136.7 (d, 3,4,5JP,C = 1.9 Hz, o-py-CH); 149.9 (d, 3,4,5JP,C = 2.1 Hz, o-pyCH); 155.7 (s, o-py-C); 194.9 (d, 2JP,C = 8.3 Hz, cis-CO); 196.9 (d, 2 JP,C = 35.9 Hz, trans-CO); 29Si{1H} NMR: δ = 0.04 (d, 2JP,Si = 5.5 Hz, SiMe3); 1.10 (d, 2JP,Si = 8.0 Hz, SiMe3). 31P NMR: δ = 41.1 (90%) (1JW,P = 309.5 Hz). Selected data of the minor isomer, 31P NMR: δ = 46.3 (1%) (1JW,P = 298.4 Hz, 2,3JP,H = m); 32.7 (9%) (1JW,P = 296.9 Hz, 2 JP,H = 17.2 Hz (d)). IR (neat): νmax/cm−1 2960.1, 2922.6, 2849.9 (w, CH); 2075.4, 1992.3, 1909.8 (s, CO); 1588.8, 1570.6 (m, CC); 1469.6, 1434.1 (m, CN); 1253.3 (s, SiMe3). MS: m/z (EI) 621.0 (50) [M]+•, 593.0 (5) [M − CO]+, 537.1 (15) [M − 3CO]+, 486.0 (100) [M − 2CO − o-py − H]+, 481.1 (50) [M − 5CO]+, 430.0 (30) [M − 4CO − o-py − H]+, 402.0 (25) [M − 5CO − o-py]+, 358.0 (50) [M − 4CO − o-py − H − SiMe3]+, 73.1 (90) [SiMe3]+. Anal. Calcd for C18H24NO6PSi2W (621.4 g/mol): C 34.79, H 3.89. Found: C 34.72, H 3.91. 1c. Yield of the diastereomeric mixture (1.0:0.02): 84.0 mg (0.16 mmol; 20%). mp = 94 °C. 1H NMR: δ = 0.18 (s, 9H, SiMe3); 0.29 (s, 9H, SiMe3); 1.07 (d, 2JP,H = 2.7 Hz, 1H, CH(SiMe3)2); 4.53 (d, 1H, 2 JP,H = 3.2 Hz, CH(P)(O)); 6.59 (dd, 1H, 3,4JH,H = 6.2 Hz, o-py-CH); 7.06 (td, 1H, 3,4JH,H = 7.7, 1.7 Hz, o-py-CH); 7.22 (d, 1H, 3JH,H = 7.9 Hz, o-py-CH); 8.39 (d, 1H, 3JH,H = 4.7 Hz, o-py-CH). 13C{1H} NMR: δ = 1.4 (s, SiMe3), 1.9 (d, 3JP,C = 2.3 Hz, SiMe3), 32.9 (d, 1JP,C = 24.6 Hz, CH(SiMe3)2)), 59.9 (d, 1JP,C = 23.6 Hz, CH(P)(O)), 119.9 (d, 3 JP,C = 3.9 Hz, o-py-CH), 122.8 (d, 5JP,C = 2.1 Hz, o-py-CH), 136.3 d, 4 JP,C = 1.98 Hz, o-py-CH), 149.8 (d, 4JP,C = 1.9 Hz, o-py-CH), 156.5 (s, o-py-C), 204.3 (d, 2JP,C = 10.9 Hz, cis-CO); 29Si{1H} NMR: δ = −0.9 (d, 2JP,Si = 5.3 Hz, SiMe3); −0.07 (d, 2JP,Si = 7.7 Hz, SiMe3). 31P NMR: δ = 64.7 (98%). Selected data of the minor isomer, 31P NMR: δ = 57.7 (2%). IR (neat): νmax/cm−1 2959.6, 2923.3, 2853.5 (w, CH); 2076.7, 2000.1, 1922.2 (s, CO); 1588.3, 1570.5 (m, CC); 1468.9, 1434.0 (m, CN); 1254.1 (SiMe3). MS: m/z (EI) 535.0 (1.5) [M]+•, 507.0 (2.5) [M − CO]+, 479.1 (8) [M − 2CO]+, 395.1 (20) [M − 5CO]+, 73.1 (100) [SiMe3]+. 1d. Yield of the diastereomeric mixture (1.0:0.01): 101.2 mg (0.21 mmol; 38%). mp = 120 °C. 1H NMR: δ = 0.17 (s, 9H, SiMe3); 0.29 (s, 9H, SiMe3); 1.10 (d, 1H, 2JP,H = 1.2 Hz, CH(SiMe3)2); 4.53 (d, 1H, 2 JP,H = 3.18 Hz, CH(P)(O)); 6.58 (t, 1H, 3JH,H = 6.2 Hz, o-py-CH); 7.06 (td,1H, 3,4JH,H = 7.73, 1.5 Hz, o-py-CH); 7.27 (d, 1H, 3JH,H = 7.8 Hz, o-py-CH); 8.39 (d, 1H, 3JH,H = 4.2 Hz, o-py-CH). 13C{1H} NMR: δ = 1.3 (d, 3JP,C = 4.0 Hz, SiMe3); 1.8 (d, 3JP,C = 2.2 Hz, SiMe3); 33.4 (d, 1JP,C = 23.5 Hz, CH(SiMe3)2)); 60.1 (d, 1JP,C = 24.6 Hz, CH(P)(O)); 120.1 (d, 3JP,C = 3.9 Hz, o-py-CH); 122.8 (d, 5JP,C = 2.15 Hz, o-py-CH); 136.3 (d, 4JP,C = 1.98 Hz, o-py-CH); 149.9 (d, 4JP,C = 2.0 Hz, o-py-CH); 156.0 (s, o-py-CH); 213.8 (d, 2JP,C = 16.1 Hz, cisCO); 29Si{1H} NMR: δ = −0.05 (d, 2JP,Si = 5.2 Hz, SiMe3); 0.56 (d, 2 JP,Si = 8.1 Hz, SiMe3). 31P NMR: δ = 91.2 (98%). Selected data of the minor isomer, 31P NMR: δ = 87.2 (2%) (2JP,H = 17.8, 5.0 Hz (dd)). IR (neat): νmax/cm−1 2957.7, 2923.8, 2852.9 (m, CH); 2068.8, 2062.2, 1919.5 (s, CO); 1588.3, 1570.6 (m, CC); 1468.1, 1434.3 (m, C N); 1254.1 (s, SiMe3). MS: m/z (EI) 489.0 (15) [M]+•, 377.1 (30) [M − 4CO]+, 349.1 (100) [M − 5CO]+, 297.1 (15) [Cr(CO)5]+, 270.0 (20) [M − 4CO − C6H5NO]+, 242.0 (30) [M − 5CO − C6H5NO]+, 168.0 (15) [M − 3CO − CH(SiMe3)2 − o-py]+, 159.0 (30) [CH(SiMe3)2]+, 73.1 (30) [SiMe3]+. Complex 1e. Dichloro(organo)phosphane complex [(CO)5WCH(SiMe3)2PCl2]14 (1.01 g, 1.73 mmol) was dissolved in diethyl ether (20 mL). Then, 12-crown-4 (0.8 equiv) was added, and the mixture cooled to −80 °C. A solution of tBuLi (1.6 M in n-pentane) (1.2 equiv) was then added dropwise, and 0.65 mL of acetone (8.84 mmol) in 5 mL of diethyl ether, precooled to −80 °C, was added via a doubleended needle. The suspension was then allowed to warm until 0 °C, and the solvent was removed in vacuo (∼10−2 mbar). The product was extracted with n-pentane (3 × 15 mL). The product was obtained as white oil, which was washed with n-pentane, thus giving a white powder. 1e. Yield: 793.6 mg (1.40 mmol; 81%). mp = 71 °C. 1H NMR: δ = 0.19 (s, 9H, SiMe3); 0.22 (s, 9H, SiMe3); 1.25 (d, 1H, 2JP,H = 3.04 Hz, CH(SiMe3)2); 1.46 (d, 3H, 3JP,H = 15.01 Hz, CH3); 1.63 (d, 3H, 3JP,H = 9.1 Hz, CH3). 13C{1H} NMR: δ = −0.4 (d, 3JP,C = 3.8 Hz, SiMe3);

enforcing a more distinct nature of the 1-aza-4-phosphabutadiene subunit of these ligands.

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EXPERIMENTAL SECTION

All reactions were carried out in an inert gas atmosphere using purified and dried argon and standard Schlenk techniques or inside the glovebox. Solvents were dried over sodium wire/benzophenone and distilled (and stored) under argon. NMR data were recorded on a Bruker DMX 300 spectrometer at 25 °C using THF-d8 as solvent; chemical shifts are given in ppm relative to tetramethylsilane (1H: 300.13, 13C: 75.5, 29Si: 59.6 MHz), and 85% H3PO4 (31P: 121.5 MHz). Mass spectra were recorded on a MAT 95 XL Finnigan (EI, 70 eV, 184 W) spectrometer, and IR spectra were recorded on a Thermo Nicolet 380 FT-IR spectrometer with attenuated total reflection (ATR) attachment; selected data are given only. Melting points were determined using a Büchi apparatus; the values are not corrected. Elemental analyses were performed using an Elementar VarioEL instrument. Complex 1a−d. Dichloro(organo)phosphane complex [(CO)5MCH(SiMe3)2PCl2]14 (1a,b (M = W): 400 mg, 0.68 mmol; 1c (M = Mo): 400 mg, 0.80 mmol; 1d (M = Cr): 250 mg, 0.55 mmol) was dissolved in diethyl ether (1a−c: 12 mL; 1d: 6 mL). Then 12crown-4 (0.8 equiv) was added, and the mixture was cooled to −80 °C. A solution of tBuLi (1.6 M in n-pentane) (1.2 equiv) was added dropwise, and then the aldehyde or ketone (1 equiv) (1a: oacetylpyridine; 1b−d: o-pyridinaldehyde) was added. The suspension was then allowed to warm to ambient temperature. The solvent was removed in vacuo (∼10−2 mbar), and the product extracted with npentane (3 × 20 mL). The product was then purified by column chromatography (Al2O3, −20 °C, h = 2 cm, Ø = 1 cm, eluent: petroleum ether); evaporation of the first fractions yielded 1a−d as diastereomeric mixtures as yellow solids. Therefore, analytical data were obtained from the mixture, and only NMR data of the major isomer are given. 1a. Yield of the diastereomeric mixture (0.2:1.0:0.1): 196.8 mg (0.31 mmol; 46%). mp = 115 °C. 1H NMR: δ = −0.15 (s, 9H, SiMe3); 0.21 (s, 9H, SiMe3); 0.91 (d, 1H, 2JP,H = 16.1 Hz, CH(SiMe3)2); 1.97 (d, 3H, 2JP,H = 14.7 Hz, CH3); 6.51 (m, 1H, o-py-CH); 6.92 (m, 1H, opy-CH); 7.15 (d, 1H, 3JH,H = 7.9 Hz, o-py-CH); 8.26 (dt, 1H, 3,4JH,H = 4.8 Hz, 0.86 Hz, o-py-CH). 13C{1H} NMR: δ = 1.2 (d, 3JP,C = 4.7 Hz, SiMe3); 1.8 (d, 3JP,C = 3.1 Hz, SiMe3); 22.9 (d, 2JP,C = 7.2 Hz, CH3); 25.7 (d, 1JP,C = 39.0 Hz, CH(SiMe3)2); 68.2 (d, 1JP,C = 25.7 Hz, C(P)(O)); 121.4 (d, 3,4,5JP,C = 1.4 Hz, o-py-CH); 122.4 (d, 3,4,5JP,C = 1.0 Hz, o-py-CH); 135.7 (d, 3,4,5JP,C = 1.2 Hz, o-py-CH); 149.7 (d, 3,4,5 JP,C = 1.3 Hz, o-py-CH); 159.9 (s, o-py-C); 196.1 (d, 2JP,C = 8.1 Hz, cis-CO); 196.5 (d, 2JP,C = 33.4 Hz, trans-CO); 29Si{1H} NMR: δ = −1.77 (d, 2JP,Si = 5.7 Hz, SiMe3); 3.67 (s, SiMe3). 31P NMR: δ = 48.9 (80%) (1JW,P = 299.8 Hz, 2JP,H = 16.1 Hz, 3JP,H = 15.1 Hz (dq)). Selected data of the minor isomer, 31P NMR: δ = 60.6 (16%) (1JW,P = 307.0 Hz, 2JP,H = 9.1 Hz (q)); 45.7 (4%) (1JW,P = 306.4 Hz, 2,3JP,H = 8.5 Hz). IR (KBr): νmax/cm−1 2962.8 (m, CH3); 2076.8, 1998.3, 1929.5 (s, CO); 1583.1, 1566.7 (m, CC); 1461.6, 1431.7 (m, CN); 1256.7 (s, SiMe3). MS: m/z (EI) 635.2 (25) [M]+•, 607.1 (5) [M − CO]+, 551.2 (30) [M − 3CO]+, 514.1 (10) [WP(CH(SiMe3)2]+, 495.2 (30) [M − 5CO]+, 486.1 (100) [M − CO − o-py − C(O)CH3]+, 484.1 (70) [M − SiMe3 − o-py]+, 458.1 (15) [M − 2CO − o-py − C(O)CH3]+, 430.1 (30) [M − 3CO − o-py − C(O)CH3]+, 402.1 (25) [M − 4CO − o-py − C(O)CH3]+, 384.1 (30) [M − 2CO − o-py − C(O)CH3 − SiMe3]+, 358.1 (50) [M − 3CO − o-py − C(O)CH3 − SiMe3 + H]+, 73.1 (80) [SiMe3]+. Anal. Calcd for C19H26NO6PSi2W (635.4 g/mol): C 35.92, H 4.12. Found: C 36.01, H 4.51. 1b. Yield of the diastereomeric mixture (0.01:1.0:0.1): 157.9 mg (0.25 mmol; 37%). mp = 132 °C. 1H NMR: δ = 0.31 (s, 9H, SiMe3); 0.39 (s, 9H, SiMe3); 1.27 (s, 1H, CH(SiMe3)2); 4.42 (d, 1H, 2JP,H = 3.2 Hz, CH(P)(O)); 7.23 (m, 2 H, o-py-CH); 7.65 (m, 1H, o-py-CH); 8.58 (d, 1H, 3JH,H = 4.2 Hz, o-py-CH). 13C{1H} NMR: δ = 1.5 (d, 3JP,C = 4.2 Hz, SiMe3); 1.9 (d, 3JP,C = 2.4 Hz, SiMe3); 32.9 (d, 1JP,C = 18.3 Hz, CH(SiMe3)2); 60.1 (d, 1JP,C = 27.1 Hz, CH(P)(O)); 120.3 (d, 3,4,5 JP,C = 3.8 Hz, o-py-CH); 123.1 (d, 3,4,5JP,C = 2.3 Hz, o-py-CH); 4941

dx.doi.org/10.1021/om400654c | Organometallics 2013, 32, 4938−4943

Organometallics

Article

Hz, trans-CO); 29Si{1H} NMR: δ = 2.7 (d, 2JP,Si = 15.5 Hz; SiMe3). 31P NMR: δ =181.1 (95%) (1JW,P = 253.7 Hz); minor isomer (2e′), 31P NMR: δ = 172.3 (5%) (1JW,P = 254.5 Hz). IR (Nujol): νmax/cm−1 1254 (m), 1942 (s), 1982 (m), 2071 (m); UV/vis (CH2Cl2) λ (log ε)/nm: 276 (1.107), 366 (0.070). MS: m/z (EI) 556 (100) [M]+•, 500 (95) [M − 2CO]+, 444 (30) [M − 4CO]+, 414 (10) [M − 5CO − 2H]+, 232 (55) [M − W(CO)5]+, 73 (75) [SiMe3]+. Anal. Calcd for C15H25O5PSi2W (556.34 g/mol): C 32.38, H 4.53. Found: C 32.32, H 4.70. Complexes 3a−d. To a solution of 1a−d in THF, TiCpCl3 and Zn were added in a 1:1:1 ratio, and the green reaction solutions were stirred at room temperature. Depending on the derivative CO elimination started, and the reaction solutions turned red (3a: 5 h, 3b: 24 h, 3c: 5 days, 3d: 7 days). The CO elimination was completed after 8 days (3a), after 35 days (3b), after 6 months (3c), and in the case of 3d completion was not reached at room temperature, even after several months (3 months: 51%, 7 months: 93%). The red reaction mixtures were filtered, and the solvent removed in vacuo (∼10−2 mbar); all analytical data were subsequently obtained. 3a. 1H NMR: δ = 0.31 (s, 18H, SiMe3); 2.29 (d, 3H, 3JP,H = 19.4 Hz, CH3); 2.79 (d, 1H, 2JP,H = 18.9 Hz, CH(SiMe3)2); 6.96−7.03 (m, 1H, o-py-CH); 7.59 (dd, 1H, 3,4JH,H = 2.66, 8.21 Hz, o-py-CH); 7.73− 7.82 (m, 1H, o-py-CH); 9.09 (dd, 3,4JH,H = 0.9, 5.7 Hz, o-py-CH). 13 C{1H} NMR: δ = 1.6 ppm (d, 3JP,C = 3.7 Hz, SiMe3); 17.8 (d, 2JP,C = 9.26 Hz, CH3); 25.6 (d, 1JP,C = 39.8 Hz, CH(SiMe3)2); 121.5 (d, 3JP,C = 18.4 Hz, o-py-CH); 122.3 (d, 5JP,C = 7.6 Hz, o-py-CH); 138.4 (d, 4 JP,C = 2.8 Hz, o-py-CH); 157.4 (d, 4JP,C = 1.9 Hz, o-py-CH); 159.5 (d, 1 JP,C = 29.3 Hz, CP); 165.8 (d, 2JP,C = 16.0 Hz, o-py-C); 198.3 (d, 2 JP,C = 11.1 Hz, cis-CO); 210.6 (d, 2JP,C = 4.8 Hz, trans-CO); 212.6 (d, 2 JP,C = 38.7 Hz, trans-CO); 29Si{1H} NMR: δ = 3.81 (d, 2JSi,C = 5.7 Hz). 31P NMR: δ = 289.9 (1JW,P = 268.7 Hz, 2JP,H = 18.9 Hz, 3JP,H = 19.4 Hz (dq)). 3b. 1H NMR: δ = 0.30 (s, 18H, SiMe3); 2.49 (d, 1H, 2JP,H = 17.0 Hz, CH(SiMe3)2); 6.85−6.96 (m, 1H, o-py-CH); 7.45−7.55 (m, 1H, o-py-CH); 7.60−7.72 (m, 1H, o-py-CH); 8.13 (d, 2JP,H = 14.95 Hz, H(o-py)CP); 8.96 (d, 2JH,H = 5.3 Hz, o-py-CH). 13C{1H} NMR: δ = 1.5 ppm (d, 3JP,C = 3.6 Hz, SiMe3); 30.0 (d, 1JP,C = 30.0 Hz, CH(SiMe3)2); 121.8 (d, 5JP,C = 7.1 Hz, o-py-CH); 123.9 (d, 3JP,C = 20.3 Hz, o-py-CH); 138.5 (d, 4JP,C = 1.8 Hz, o-py-CH); 151.7 (d, 1JP,C = 31.0 Hz, CP); 156.5 (d, 4JP,C = 2.0 Hz, o-py-CH); 166.2 (d, 2JP,C = 10.8 Hz, o-py-CH); 197.8 (d, 2JP,C = 10.4 Hz, cis-CO); 210.5 (d, 2JP,C = 4.7 Hz, trans-CO); 213.7 (d, 2JP,C = 39.1 Hz, trans-CO); 29Si{1H} NMR: δ = 2.85 (d, 2JSi,C = 9.5 Hz). 31P NMR: δ = 317.8 ppm (1JW,P = 270.1 Hz, 2JP,H = 14.95 Hz, 2JP,H = 17.04 Hz (dd)). 3c. 1H NMR: δ = 0.34 (s, 18H, SiMe3); 2.48 (d, 1H, 2JP,H = 16.2 Hz, CH(SiMe3)2); 6.94−7.05 (m, 1H, o-py-CH); 7.42 (d, 1H, 3JH,H = 7.9 Hz, o-py-CH); 7.68 (dd, 1H, 3,4JH,H = 7.6 Hz, o-py-CH); 7.92 (d, 1H, 2JP,H = 16.8 Hz, H(o-py)CP); 8.86 (d, 3JH,H = 5.1 Hz, o-pyCH). 13C{1H} NMR: δ = 1.5 (d, 3JP,C = 3.5 Hz, SiMe3); 31.0 (d, 1JP,C = 36.1 Hz, CH(SiMe3)2); 121.3 (d, 5JP,C = 6.9 Hz, o-py-CH); 124.2 (d, 3 JP,C = 20.2 Hz, o-py-CH); 138.2 (d, 4JP,C = 1.9 Hz, o-py-CH); 152.9 (d, 1JP,C = 23.8 Hz, CP); 155.7 (s, o-py-CH); 164.2 (d, 2JP,C = 11.4 Hz, o-py-C); 204.5 (d, 2JP,C = 12.9 Hz, cis-CO); 219.6 (d, 2JP,C = 39.1 Hz, trans-CO), 220.7 (d, 2JP,C = 7.8 Hz, trans-CO); 29Si{1H} NMR: δ = 2.44 (d, 2JSi,C = 8.9 Hz). 31P NMR: δ = 335.9 ppm (dd, 2JP,H = 16.2 Hz, 2JP,H = 16.8 Hz). 3d. 31P NMR: δ = 370.9 ppm (2JP,H = br). Crystal Data for 2e. Suitable single crystals of 2e were obtained from a concentrated THF solution at room temperature. Data were collected with a Nonius KappaCCD diffractometer equipped with a low-temperature device at 100 K by using graphite monochromated Mo Kα radiation (λ = 0.71073 Å). The structure was solved by Patterson methods (SHELXS-97)15a and refined by full-matrix leastsquares on F2 (SHELXL-97).15b C15H25O5PSi2W, M = 556.4, crystal dimensions 0.79 × 0.17 × 0.10 mm3, orthorhombic, space group P212121, Z = 4, a = 10.3992(3) Å, b = 13.5300(4) Å, c = 15.6236(5) Å, α = 90°, β = 90°, γ = 90°, V = 2198.26(11) Å3, dc = 1.681 g cm−3, μ = 5.455 mm−1, T = 123(2) K, transmission factors (min/max) 0.0988/ 0.6115, analytical absorption correction based on the indexing of the

0.0 (d, 3JP,C = 2.6 Hz, SiMe3); 20.0 (d, 3JP,C = 1.3 Hz, CH3); 23.0 (d, 3 JP,C = 9.1 Hz, CH3); 30.5 (d, 3JP,C = 17.4 Hz, CH(SiMe3)2); 61.1 (d, 1 JP,C = 31.0 Hz, C(CH3)2(P)(O)); 192.7 (d, 2JP,C = 9.7 Hz, cis-CO); 195.0 (d, 2JP,C = 32.9 Hz, trans-CO); 29Si{1H} NMR: δ = −1.0 (d, 2JP,Si = 6.5 Hz; SiMe3); 1.2 (d, 2JP,Si = 8.4 Hz; SiMe3). 31P NMR: δ =55.6 (ssat, 1JW,P = 296.2 Hz). IR (Nujol): νmax/cm−1 1880 (s), 1924 (w), 2067 (s), 2077 (s); UV/vis (CH2Cl2) λ (log ε)/nm: 234 (0.51), 305 (0.05). MS: m/z (EI) 571 (15) [M]+•, 557 (15) [M − Me]+, 516 (30) [M − 2CO]+, 486 (100) [M − 3CO]+, 73 (50) [SiMe3]+. Anal. Calcd for C15H25O6PSi2W (566.34 g/mol): C 31.48, H 4.40. Found: C 31.26, H 4.42. Complexes 2a−d. To a solution of 1a−d in THF, TiCpCl3 and zinc were added in a 1:1:1 ratio while stirring, and the green solution was then stirred until the reaction was completed. In the case of 2a and 2c the subsequent CO elimination was so fast that only the 31P NMR data could be obtained. The reaction mixture was filtered, and the solvent removed in vacuo (∼10−2 mbar). Analytical data were obtained for the mixture, and only an NMR data set of the major isomer is given. 2a. Analytical data obtained from the reaction mixture (0.8:1.0:0.3). Major isomer, 31P NMR: δ = 213.8 (47%) (1JW,P =266.8 Hz, 2,3JP,H = 7.7 Hz, 23.4 Hz (qd)); minor isomer, 31P NMR: δ = 200.9 (40%) (1JW,P = 260.0 Hz, 2,3JP,H = 19.4 Hz, 30.5 Hz (qd)); 215.9 (13%) (1JW,P = 263.9 Hz, 2,3JP,H = 11.8 Hz, 31.1 Hz (qd)). 2b. Analytical data obtained from reaction mixture (0.01:0.06:1.0). 1 H NMR: δ = 0.33 (s, 18H, SiMe3); 1.63 (d, 1H, 2JP,H = 7.3 Hz, CH(SiMe3)2); 7.09−7.20 (m, 2H, o-py-CH); 7.60−7.71 (m, 1H, o-pyCH); 8.52 (d, 1H, 2JH,H = 4.6 Hz, o-py-CH); 8.61 (d, 2JP,H = 19.95 Hz, H(o-py)CP). 13C{1H} NMR: δ = 1.4 (d, 3JP,C = 2.89 Hz, SiMe3); 36.0 (d, 1JP,C = 12.2 Hz, CH(SiMe3)2); 123.5 (s, o-py-CH); 123.7 (s, o-py-CH); 137.3 (d, 3JP,C = 1.6 Hz, o-py-CH); 148.8 (d, 4JP,C = 3.4 Hz, o-py-CH); 156.9 (d, 2JP,C = 2.3 Hz, o-py-C); 161.5 (d, 1JP,C = 47.3 Hz, CP); 196.7 (d, 2JP,C = 10.1 Hz, cis-CO); 200.6 (d, 2JP,C = 29.9 Hz, trans-CO); 29Si{1H} NMR: δ = 2.77 (d, 2JSi,C = 14.7 Hz). 31P NMR: δ = 244.6 (94%) (1JW,P = 269.7 Hz, 2JP,H = 16.1 Hz); minor isomer, 31P NMR: δ = 238.6 (5%) (1JW,P = 260.5, 2JP,H = 21.6, 14.6 (dd)); 233.3 (1%). 2c. Analytical data obtained from reaction mixture (0.1:1.0). 31P NMR: δ = 271.3 (88%) (2JP,H = 18.3 Hz (d)); minor isomer, 31P NMR: δ = 266.7 (12%) (2JP,H = m). 2d. Analytical data obtained from reaction mixture (0.01:0.5:1.0). 1 H NMR: δ = 0.34 (s, 18H, SiMe3); 1.52 (d, 1H, 2JP,H = 6.3 Hz, CH(SiMe3)2); 7.07−7.18 (m, 2H, o-py-CH); 7.61−7.69 (m, 1H, o-pyCH); 8.52 (d, 1H, 2JH,H = 3.7 Hz, o-py-CH); 8.60 (d, 2JP,H = 20.9 Hz, H(o-py)CP). 13C{1H} NMR: δ = 1.4 (d, 3JP,C = 2.7 Hz, SiMe3); 36.3 (d, 1JP,C = 17.0 Hz, CH(SiMe3)2); 122.6 (d, 4,5JP,C = 6.3 Hz, o-pyCH); 123.2 (d, 3JP,C = 18.2 Hz, o-py-CH); 137.2 (d, 4,5JP,C = 1.6 Hz, opy-CH); 148.7 (d, 4JP,C = 3.7 Hz, o-py-CH); 156.9 (s, o-py-C); 166.6 (d, 1JP,C = 39.4 Hz, CP); 215.9 (d, 2JP,C = 17.8 Hz, cis-CO); 223.1 (d, 2JP,C = 39.0 Hz, trans-CO); 29Si{1H} NMR: δ = 2.50 (d, 2JSi,P = 14.7 Hz). 31P NMR: δ = 304.4 (94%) (2JP,H = 20.9 Hz, 6.3 Hz (dd)); minor isomer, 31P NMR: δ = 291.4 (5%) (JP,H = m); 296.7 (1%) (2JP,H = 21.6 Hz, 16.4 Hz (dd)). Complex 2e. A solution of 1e (172.2 mg, 0.22 mmol) in THF (0.5 mL) was added to a solution of TiCpCl3 (48.5 mg, 0.22 mmol) and zinc (14.5 mg, 0.22 mmol) in THF (0.5 mL) at room temperature. After stirring of the green reaction mixture overnight, it was subjected to 31P NMR spectroscopic reaction control, and complex 2e was then characterized as a 95:5 mixture of the P,C-atropisomers (based on integration of the 31P NMR). The solvent was removed in vacuo (∼10−2 mbar), and the product isolated by extraction with n-pentane (3×) as a colorless powder. 2e,e′ (mixture (0.5:1.0). Yield: 110 mg (0.18 mmol; 90%). mp = 76 °C; major isomer (2e). 1H NMR: δ = 0.29 (s, 18H, SiMe3); 1.31 (d, 1H, 2JP,H = 10.0 Hz, CH(SiMe3)2); 2.23 (dq, 3H, JH,H = 0.9 Hz, 3JP,H = 30.8 Hz, CH3); 2.25 (d, 3H, JH,H = 0.9 Hz, 3JP,H = 23.1 Hz, CH3). 13 C{1H} NMR: δ = 2.2 (d, 3JP,C = 2.9 Hz, SiMe3); 28.0 (d, 2JP,C = 21.0 Hz, CH3); 28.8 (d, 2JP,C = 11.0 Hz, CH3); 33.4 (d, 3JP,C = 14.2 Hz, CH(SiMe3)2); 197.3 (d, 2JP,C = 9.7 Hz, cis-CO); 200.4 (d, 2JP,C = 27.8 4942

dx.doi.org/10.1021/om400654c | Organometallics 2013, 32, 4938−4943

Organometallics

Article

crystal faces, 2θmax = 55.98°, no. of unique data 5179, Rint = 0.0671, R1 (for I > 2σ(I)) = 0.0276, wR2 (for all data) = 0.0569, final R = 0.0304, goodness of fit 1.024, ΔF(max/min) = 0.984/−1.583 e Å−3. Crystal Data for 3a. Suitable single crystals of 3a were obtained from a concentrated THF solution at room temperature. Data were collected with a Nonius KappaCCD diffractometer equipped with a low-temperature device at 100 K by using graphite monochromated Mo Kα radiation (λ = 0.71073 Å). The structure was solved by Patterson methods (SHELXS-97)15a and refined by full-matrix leastsquares on F2 (SHELXL-97).15b C18H26NO4PSi2W, M = 591.4, red, crystal dimensions 0.36 × 0.16 × 0.07 mm3, monclinic, space group P21/c, Z = 4, a = 8.6208(2) Å, b = 15.8306(3) Å, c = 18.7955(3) Å, α = 90°, β = 115.1240(10)°, γ = 90°, V = 2322.39(8) Å3, dc = 1.691 g cm−3, μ = 5.168 mm−1, T = 123(2) K, transmission factors (min/max) 0.2577/0.7137, analytical absorption correction based on the indexing of the crystal faces, 2θmax = 56.0°, no. of unique data 5583, Rint = 0.0473, R1 (for I > 2σ(I)) = 0.0228, wR2 (for all data) = 0.0553, final R = 0.0261, goodness of fit 1.065, ΔF(max/min) = 1.015/−2.066 e Å−3. Crystal Data for 3b. Suitable single crystals of 3b were obtained from a concentrated THF solution at room temperature. Data were collected with a Nonius KappaCCD diffractometer equipped with a low-temperature device at 100 K by using graphite monochromated Mo Kα radiation (λ = 0.71073 Å). The structure was solved by Patterson methods (SHELXS-97)15a and refined by full-matrix leastsquares on F2 (SHELXL-97).15b C17H24NO4PSi2W, M = 577.37, red, crystal dimensions 0.20 × 0.12 × 0.04 mm3, monclinic, space group P21/c, Z = 4, a = 8.5399(3) Å, b = 15.7396(6) Å, c = 18.9053(6) Å, α = 90°, β = 116.7230(10)°, γ = 90°, V = 2269.73(14) Å3, dc = 1.690 g cm−3, μ = 5.285 mm−1, T = 123(2) K, transmission factors (min/max) 0.4179/0.8164, analytical absorption correction based on the indexing of the crystal faces, 2θmax = 56.0°, no. of unique data 5461, Rint = 0.0844, R1 (for I > 2σ(I)) = 0.0365, wR2 (for all data) = 0.0688, final R = 0.0723, goodness of fit 0.940, ΔF(max/min) = 2.582/−2.495 e Å−3. Crystallographic data of complexes 1a,b, 2e and 3a,b have been deposited at the Cambridge Crystallographic Data Centre under the numbers 948174 (1a), 948175 (1b), 948176 (2e), 948178 (3a), and 948177 (3b). This data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/ data_request/cif.

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88, 1327. (d) Scherer, O. J. Angew. Chem., Int. Ed. Engl. 1985, 24, 924. (f) Le Floch, P. Coord. Chem. Rev. 2006, 250, 627. (e) Weber, L. Angew. Chem., Int. Ed. 2002, 41, 563. (3) (a) Van der Knaap, T. A.; Bickelhaupt, F.; Kraaykamp, J. G.; van Koten, G.; Bernards, J. P. C.; Edzes, H. T.; Veeman, W. S.; de Boer, E.; Baerends, E. J. Organometallics 1984, 3, 1804. (b) Appel, R.; Casser, C.; Knoch, F. J. Organomet. Chem. 1985, 293, 213. (c) Marinetti, A.; Mathey, F. Angew. Chem., Int. Ed. Engl. 1988, 27, 1382. (d) Regitz, M.; Scherer, O. J. Multiple Bonds and Low Coordination in Phosphorus Chemistry; Thieme: Stuttgart, 1990. (e) Le Floch, P.; Marinetti, A.; Ricard, L.; Mathey, F. J. Am. Chem. Soc. 1990, 112, 2407. (f) Lorenz, I.P.; Pohl, W.; Nöth, H.; Schmidt, M. J. Organomet. Chem. 1994, 475, 211. (g) Dillon, K. B.; Mathey, F.; Nixon, J. F. Phosphorus: The Carbon Copy; Wiley: Chichester, 1998. (h) Mathey, F. Angew. Chem., Int. Ed. 2003, 42, 1578. (4) Bates, J. I.; Dugal-Tessier, J.; Gates, D. P. Dalton Trans. 2010, 39, 3151. (5) Dugal-Tessier, J.; Dake, G. R.; Gates, D. P. Organometallics 2007, 26, 6481. (6) (a) Brèque, A.; Santini, C. C.; Mathey, F.; Fischer, J.; Mitschler, A. Inorg. Chem. 1984, 23, 3463. (b) Le Floch, P.; Mathey, F. Coord. Chem. Rev. 1998, 179−180, 771−791. (7) (a) Deschamps, B.; Mathey, F. J. Chem. Soc., Chem. Commun. 1985, 1010. (b) Ionescu, E.; Wilkens, H.; Streubel, R. Organosilicon Chemistry VIFrom Molecules to Materials; Auner, N., Ed.; WileyVCH: Weinheim, 2005; p 202. (8) Albrecht, C.; Shi, L.; Marinas Pérez, J.; van Gastel, M.; Schwieger, S.; Neese, F.; Streubel, R. Chem.Eur. J. 2012, 18, 9780. (9) (a) Bauer, S.; Marinetti, A.; Richard, L.; Mathey, F. Angew. Chem., Int. Ed. Engl. 1990, 29, 1166. (b) Streubel, R.; Kusenberg, A.; Jeske, J.; Jones, P. G. Angew. Chem., Int. Ed. 1994, 33, 2427. (10) (a) Ö zbolat, A.; von Frantzius, G.; Marinas Pérez, J.; Nieger, M.; Streubel, R. Angew. Chem. 2007, 119 (48), 9488. (b) Streubel, R.; Bode, M.; Marinas Pérez, J.; Schnakenburg, G.; Daniels, J.; Nieger, M.; Jones, P. Z. Anorg. Allg. Chem. 2009, 635, 1163. (c) Bode, M.; Daniels, J.; Streubel, R. Organometallics 2009, 28, 4636. (d) Albrecht, C.; Bode, M.; Pérez, J. M.; Schnakenburg, G.; Streubel, R. Dalton Trans. 2011, 40, 1. (11) Streubel, R.; Klein, M.; Schnakenburg, G. Organometallics 2012, 31, 4711. (12) Skapski, A. C.; Troughton, P. G. H. Acta Crystallogr. 1970, B26, 716. (13) (a) Coutts, R. S. P.; Martin, R. L.; Wailes, P. C. Inorg. Nucl. Chem. Lett. 1973, 9, 49. (b) Wei Huang, K.; Waymouth, R. M. Dalton Trans. 2004, 3, 354. (14) Khan, A. A.; Wismach, C.; Jones, P. G.; Streubel, R. Dalton Trans. 2003, 12, 2483. (15) (a) SHELXS-97: Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 1990, 46, 467. (b) Sheldrick, G. M. SHELXL-97; University of Göttingen: Göttingen, Germany, 1997.

ASSOCIATED CONTENT

S Supporting Information *

Molecular structures of 1a (Figure S1), 1b (Figure S2). This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Fax: (+) 49-228-73-9616 E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The project was funded by the Deutsche Forschungsgemeinschaft (priority research program SFB 813 “Chemistry at Spin Centers” (TP B4) and STR 411/29−1); G.S. thanks Prof. A. C. Filippou for various support. Dedicated to Prof. E. Niecke on the occasion of his 75th birthday.

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REFERENCES

(1) (a) Appel, R.; Knoll, F.; Ruppert, I. Angew. Chem., Int. Ed. Engl. 1981, 20, 731. (b) Appel, R.; Knoll, F. Adv. Inorg. Chem. 1989, 33, 259. (c) Weber, L. Eur. J. Inorg. Chem. 2000, 2425. (d) Yoshifuji, M. J. Chem. Soc., Dalton Trans. 1998, 3343. (e) Gaumont, A. C.; Denis, J. M. Chem. Rev. 1994, 94, 1413. (2) (a) Mathey, F. Acc. Chem. Res. 1992, 25, 90. (b) Weber, L. Angew. Chem., Int. Ed. Engl. 1996, 35, 271. (c) Nixon, J. F. Chem. Rev. 1988, 4943

dx.doi.org/10.1021/om400654c | Organometallics 2013, 32, 4938−4943