Lanthanum-Catalyzed Double Hydrophosphinylation of Nitriles

Jan 20, 2017 - A new lanthanum-based catalyst was shown to be effective for the double hydrophosphinylation of unactivated nitriles under very mild ...
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Lanthanum-Catalyzed Double Hydrophosphinylation of Nitriles Miriam M. I. Basiouny and Joseph A. R. Schmidt* Department of Chemistry & Biochemistry, School of Green Chemistry and Engineering, College of Natural Sciences and Mathematics, The University of Toledo, 2801 West Bancroft Street MS 602, Toledo, Ohio 43606-3390, United States S Supporting Information *

ABSTRACT: A new lanthanum-based catalyst was shown to be effective for the double hydrophosphinylation of unactivated nitriles under very mild conditions. Surprisingly, the lanthanum catalyst gave two regioisomeric products depending on the nature of the starting nitrile. Primary alkyl nitriles undergo 1,1-addition to give products with a new P−C−P linkage and concomitant formation of a primary amine. Under the same conditions, secondary alkyl and aryl nitriles instead produced 1,2addition products, where 1 equiv of the phosphine oxide was added to the carbon, while a second equivalent added to the nitrogen of the nitrile, resulting in a P−C−N−P framework. Further investigation of the catalytic cycle yielded evidence that all nitriles first undergo 1,1-addition (deemed the kinetic product) that then undergoes isomerization to the final unsymmetric addition product (the thermodynamic product). All catalytic reactions were run neat or with very little solvent, required little workup, and had high to moderate yields.

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INTRODUCTION Phosphines (R3P) and phosphine oxides (R3PO; R = H, aryl, alkyl) are broadly applicable, versatile compounds that are used in many fields ranging from the pharmaceutical industry1 to organometallic catalysis.2,3 Chelating diphosphine ligands, as well as their partially or fully oxidized derivatives, have become a nearly indispensable part of the synthetic chemist’s toolbox.4 Diphosphine ligands bearing a free amine are much less common but have been utilized in important roles. For example, aminodiphenylphosphonic acids have been used as chelating agents, corrosion inhibitors, surfactants,5 are able to mimic amino acid residues, and can act as potent protein inhibitors.6 This class of compounds was first synthesized in 1971 via the reaction of acetonitrile with phosphorus(III) bromide mediated by a strong acid.5 Currently, these compounds are produced by hydrophosphorylation (addition of H−P(O)(OR)2) of nitriles7 and isonitriles8 in the presence of acid7b or base.9 The viability of this reaction protocol is linked to the high acidity of phosphonates (pKa ≈ 18.4−9.0).10 In contrast, the hydrophosphinylation (addition of H− P(O)R2) of nitriles and isonitriles is a much more daunting task due to the decreased acidity of phosphine oxides (pKa ≈ 26.9−20.3).10 As a result, reports of the hydrophosphinylation of nitriles and isonitriles are scarce, having been achieved with limited success using metal-catalyzed conditions and/or activated nitriles. In 2006, Han et al. demonstrated that single © XXXX American Chemical Society

and double addition of phosphine oxide to isonitriles can be achieved regioselectively by employing palladium and rhodium catalysts, respectively.11 Onys’ko et al. described a basecatalyzed double hydrophosphorylation applicable to alkyl nitriles with electron-withdrawing substituents (Scheme 1, top).7a,9,12 This double hydrophosphorylation required polyfluorinated or polychlorinated acetonitrile and utilized either diphenyl or diethyl phosphite in the presence of a base (triethylamine) to yield the monohydrophosphorylated imine, which subsquently reacted with a second equivalent of phosphite to yield the 1,1-addition product.7a Scheme 1. Onys’ko’s Reported Double Hydrophosphorylation of Activated Alkyl Nitriles and Subsequent Isomerization/Elimination Reactions9,12

Received: December 12, 2016

A

DOI: 10.1021/acs.organomet.6b00919 Organometallics XXXX, XXX, XXX−XXX

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indicates that the lanthanide species is required for the reaction to occur, playing a direct role in the hydrophosphinylation. Undertaking the hydrophosphinylation reaction with 1 mol % rather than 10 mol % afforded the double hydrophosphinylation product; however, the reaction was very slow and did not reach 100% completion even after an elongated time period (4 days). In an effort to delineate the reaction scope for this rare double hydrophosphinylation reaction, we utilized several alkyl nitriles under the catalytic conditions. All primary alkyl nitriles yielded symmetric 1,1-regioisomers (Table 1). In some cases,

In 2008, Hor et al. described the double hydrophosphinylation of acetonitrile to produce the 1,1-addition product in the presence of chromium(III) and water, resulting in a doubly phosphinylated carbon and a free amine fragment (NH2).13 Another possible product from the double hydrophosphinylation of nitriles is the unsymmetric double addition of phosphine oxide, with the first phosphorus delivered to the carbon and the second phosphorus binding to the nitrogen to form a new P− C−N−P fragment (1,2-addition). Examples of compounds with this connectivity are very rare. In 1992, Chengye showed that these compounds can be accessed when reacting oximes with chlorodiphenylphosphine under radical conditions, followed by a subsequent oxidation of the phosphine to give the phosphine oxide.14 Similarly, reaction of compounds bearing a preestablished P−C−N backbone with chlorophosphine also yields the unsymmetric 1,2-addition products.15 In 2002, Storace et al. showed that the reaction of oximes with chlorodiphenylphosphine can yield the 1,2-addition product, but only in very low yields as a side product.16 Herein, we report the first example of lanthanum(III)-catalyzed double hydrophosphinylation of unactivated nitriles under mild conditions. These catalysts are applicable to a wide range of nitriles with high yields to produce the symmetric (1,1-addition) and surprisingly, the unsymmetric (1,2-addition) products (Scheme 2). Generation of the 1,2-

Table 1. Double Hydrophosphinylation of Nitriles To Yield 1,1-Addition Productsa

Scheme 2. Lanthanum(III)-Catalyzed Double Hydrophosphinylation of Nitriles

a Catalytic reactions were run with La(Dmba)3 (27 mg, 0.050 mmol, 10 mol %), nitrile, and diphenylphosphine oxide at room temperature unless specified otherwise. Method I: neat (2 mL of the nitrile, excess), HP(O)Ph2 (202 mg, 1.0 mmol). Method II: pyridine (3 mL), nitrile (0.5 mmol), HP(O)Ph2 (303 mg, 1.5 mmol). *80 °C. +Catalyst loading at 54 mg, 0.100 mmol, 20 mol %.

addition products represents a useful new route to desymmetrized dppe [bis(diphenylphosphino)ethane] derivatives bearing a nitrogen atom within the ligand backbone.

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RESULTS AND DISCUSSION We previously reported the development of a new class of homoleptic lanthanum(III) complexes supported by α-metalated N,N-dimethylbenzylamine ligands (La(Dmba)3).17 These new lanthanide complexes proved to be effective for the hydrophosphination (addition of H−PR2) of a wide variety of heterocumulenes.18 Many other research groups have also shown the ability of lanthanide complexes to catalyze hydrophosphination of unsaturated substrates, including alkenes and alkynes.19 In hydrophosphination, the optimal solvent was tetrahydrofuran; moving from hydrophosphination to hydrophosphinylation, we found that tetrahydrofuran was not polar enough to solvate the active catalyst. Thus, attempting to utilize our La(Dmba)3 precatalyst in the more polar solvent acetonitrile for hydrophosphinylation, we were delightfully surprised to discover that our only reaction product was doubly hydrophosphinylated acetonitrile with phosphine oxides adding twice to the carbon atom, concomitantly producing a free amine. Therefore, pyridine was chosen as a suitable polar solvent for the double hydrophosphinylation of nitriles, as it solvated the active lanthanum catalyst without taking part in the catalysis. The control reaction without La(Dmba)3 as precatalyst did not yield any hydrophosphinylation products. Similarly, attempted reactions with general base (potassium tert-butoxide) or strong acid (triflic acid) catalysts instead of La(Dmba)3 did not yield any tractable products. This

reactions required higher temperatures (80 °C) in order to reach 100% conversion via 31P{1H} NMR spectroscopy in 48 h. Additionally, for products 1c and 1d, pyridine was necessary as solvent. In general, each of these alkyl nitriles (products 1a−d) gave nearly quantitative conversion, and high to moderate yields were isolated. During the course of these hydrophosphinylation reactions, the reaction mixture was sampled regularly, but there was no evidence of singly hydrophosphinylated nitriles at any point during the catalysis. To our surprise, in the case of benzonitrile (PhCN), using the same catalyst loading and conditions, high conversion to a single product was observed, but it displayed two doublets in its 31 1 P{ H} NMR spectrum that were coupled to each other. This suggested that double hydrophosphinylation had occurred to produce a new regioisomer, with one phosphine oxide bound to the carbon atom and the second phosphine oxide bound to the nitrogen atom, giving a product with a P−C−N−P linkage. The related reaction employing o-fluorobenzonitrile proceeded similarly to give a highly crystalline product with two 31P{1H} signals that were coupled to each other (Figure 1). X-ray diffraction confirmed the connectivity of the unprecedented double hydrophosphinylation product (Figure 2). Formation of 1,2-addition products proved to be quite general for the various substituted aryl nitriles tested. Two B

DOI: 10.1021/acs.organomet.6b00919 Organometallics XXXX, XXX, XXX−XXX

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Table 2. Double Hydrophosphinylation of Nitriles To Yield 1,2-Addition Productsa

Figure 1. 31P{1H} NMR spectrum of the double hydrophosphinylation of o-fluorobenzonitrile (product 2f) in CDCl3.

Figure 2. ORTEP diagram of 2f (thermal ellipsoids at 50% probability). Selected bond lengths (Å) and angles (deg): P1−C1 = 1.85(1), P1−O1 = 1.44(1), C1−N1 = 1.46(2), P2−N1 = 1.66(1), P2−O2 = 1.49(1); O1−P1−C1 = 110.00(6), O2−P2−N1 = 112.23(5).

doublets in the 31P{1H} NMR spectra indicative of the P−C− N−P products were detected in each case (Table 2, products 2a−n). The system proved to be tolerant to numerous functional groups, invariably giving high yields of the 1,2addition products. Several nitriles required pyridine as solvent, as they were solids at room temperature. Of the aryl nitriles tested, only 1-naphthonitrile failed to react, which we attribute to its significant steric hindrance. Given the high yields observed, no obvious pattern could be deduced correlating reaction yields with the various electron-withdrawing or -donating substituents on the aromatic rings. Investigation of Catalytic Cycle. Given the contrasting results between primary alkyl nitriles and aryl nitriles, we further investigated secondary and tertiary alkyl nitriles (Table 2, products 2o−q). The secondary nitriles (cyclohexyl and isopropyl) both led to 1,2-addition products, while the tertbutyl nitrile failed to react at all. These results seem to indicate that the greater steric bulk of the secondary center results in double hydrophosphinylation to yield the unsymmetric 1,2addition products, while more extreme steric bulk shuts down the reaction entirely. In fact, the aryl nitriles, having greater steric bulk than primary alkyl nitriles, seem to adhere to this trend nicely.

a Catalytic reactions were run with La(Dmba)3 (27 mg, 0.050 mmol, 10 mol %), nitrile, and diphenylphosphine oxide at room temperature unless specified otherwise. Method I: neat (2 mL of the nitrile, excess), HP(O)Ph2 (202 mg, 1.0 mmol). Method II: pyridine (3 mL), nitrile (0.5 mmol), HP(O)Ph2 (303 mg, 1.5 mmol). *80 °C. +Catalyst loading at 54 mg, 0.100 mmol, 20 mol %. #Crude NMR spectra indicated complete conversion of nitrile to a 1c/2s or 1d/2t mixture, with isomerization from 1 to 2 being a very slow process.

The reaction products obtained by the double hydrophosphinylation of primary alkyl nitriles seemed to imply a simple insertion and protonolysis mechanism mediated by the C

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Organometallics Lewis acidic lanthanum center. On the other hand, the reaction products obtained with the secondary alkyl and aryl products were much harder to explain. Specifically, it was difficult to envision how the nitrogen−phosphorus linkage was produced. In an effort to obtain further insight, the catalytic hydrophosphinylation of benzonitrile with diphenylphosphine oxide was monitored by time-resolved 31P{1H} NMR spectroscopy. Within the first 2 h, the appearance of a reaction intermediate was detected by the growth of a new singlet at 37.6 ppm in deuterated pyridine. A small quantity of this intermediate was then successfully isolated, proving to be a 1,1-double addition product analogous to those obtained with primary alkyl nitriles (Scheme 3). Scheme 3. Careful Isolation of the Intermediate in Hydrophosphinylation of Benzonitrile Yielded the 1,1Addition Product 1e

On the basis of these observations, we hypothesized that the diphenylphosphine oxide initially produces the 1,1-addition product (kinetic product), which then undergoes a subsequent isomerization to the final 1,2-addition product (thermodynamic product) in most cases. The isolated benzonitrile kinetic product (1e) was then resubjected to active lanthanum catalyst and readily underwent the isomerization to produce 2a overnight. In contrast, product 1e was treated with strong base (potassium tert-butoxide; 10 mol %), strong acid (triflic acid; 10 mol %), or a Lewis acid (triethoxysilane; 10 mol %) and subjected to heating (50 °C) over an extended period (1 week) but no isomerization product was detected. Furthermore, no isomerization was observed by merely heating a solution of 1e in either THF or pyridine. Given that the secondary alkyl nitriles (2o and 2p) and all of the aryl nitriles readily underwent isomerization to produce the 1,2-addition products, the original primary alkyl nitriles were investigated further in an effort to induce this isomerization under forcing conditions. Both heteroatom-substituted propionitriles ultimately underwent isomerization in the presence of the lanthanum catalyst to give the 1,2-addition products after extended heating at 80 °C (120 h), while the products from hydrophosphinylation of acetonitrile and propionitrile did not isomerize under any conditions tested. Our catalytic results support a mechanism (Figure 3) in which La(Dmba)3 reacts with 3 equiv of diphenylphosphine oxide via protonolysis to produce the active catalyst in situ; this is supported by a control reaction with an internal standard that shows complete protonolysis, producing 3 equiv of N,Ndimethylbenzylamine (HDmba) and forming the tris-phosphinyl lanthanum active catalyst. Coordination and insertion of a nitrile, via a four-membered transition state, results in attachment of the phosphine oxide to the carbon atom and production of a lanthanum−amide bond; mechanistic studies showed that decreasing the catalyst loading decreases the rate of the reaction in a first-order fashion (for other possible binding modes please see ref 20). Because we have never observed evidence of monoaddition products, even when using the substrate nitrile as reaction solvent, we postulate that both phosphine oxide additions happen at a single metal center.

Figure 3. Proposed catalytic cycle for double hydrophosphinylation of nitriles.

After the first phosphine oxide insertion, protonolysis results in dative coordination of the imine and the oxide, forming a stable five-membered chelate ring. This is immediately followed by the second insertion, with protonolysis generating a free amine and the 1,1-addition product that subsequently undergoes isomerization to the 1,2-addition product in most cases. As noted above, only acetonitrile and propionitrile underwent double hydrophosphinylation without isomerization, no matter what conditions were employed. As these two substrates are the least sterically hindered, it seems that steric bulk at the phosphinylated carbon atom provides the driving force for isomerization to the final 1,2-addition products. Although the mechanism behind the isomerization remains unclear, Onys’ko previously showed a similar carbon to nitrogen migration involving a phosphoryl group.9 In that report, it was shown that isomerization occurs intramolecularly after the double hydrophosphorylation of an electron-withdrawing nitrile, proceeding via a three-membered ring, and ultimately driven by the loss of hydrogen halide (Cl, F) (Scheme 1, bottom). Much like our chemistry, their isomerization also required heating over extended periods.9 It is possible that our isomerization similarly occurs via attack of the amine group on the phosphorus atom to produce a three-membered ring that then collapses via proton transfer to give the final products, although additional experiments would be necessary to confirm this assertion.

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CONCLUSIONS We have demonstrated the first example of lanthanumcatalyzed double hydrophosphinylation of nitriles. Primary alkyl nitriles gave high yields of products with hydrophosphinylation twice at the carbon atom, while secondary and aryl nitriles rapidly isomerized to give products with hydrophosphinylation once at the carbon atom and once at the nitrogen atom, yielding a new P−C−N−P connectivity. A brief D

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layers were combined. The solvents were removed under reduced pressure, yielding the clean reaction product. Product Characterization. 1a (method I, isolation A):21 white solid, 200 mg (90%). Mp: 95−100 °C. 1H NMR (CDCl3): δ 8.17 (t, 3 JH−H = 7.0 Hz, 2H), 7.89 (t, 3JH−H = 7.0 Hz, 2H), 7.71−7.66 (m, 2H), 7.53 (td, 3JH−H = 7.0 Hz, 4JH−H = 2.0 Hz, 1H), 7.43−7.37 (m, 5H), 7.32−7.28 (m, 8H), 2.13 (t, 3JH−P = 11.0 Hz, 2H), 1.37 (t, 3JH−P= 15.0 Hz, 3H). 13C{1H} NMR (CDCl3): δ 132.9 (vt,22 JC−P = 4.0 Hz), 132.4 (vt,22 JC−P = 4.0 Hz), 132.0, 131.6, 129.8 (dd,23 JC−P = 95.0 Hz, JC−P = 9.0 Hz), 128.4 (vt,22 JC−P = 5.7 Hz), 128.3 (vt,22 JC−P = 5.7 Hz), 58.1 (t, JC−P = 65.0 Hz), 21.8. 31P{1H} NMR (CDCl3): δ 31.6. IR (cm−1): 3054.69 (w), 1589.79 (w), 1428.17 (w), 1436.91 (s), 1311.84 (w), 1177.33 (s), 1109.27 (s), 1072.00 (w), 1045.78 (w), 1027.95 (w), 997.84 (m), 941.54 (m), 846.55 (m). HRMScalc for C26H26NO2P2 [M + H+]: 446.1439. HRMSmeas: 446.1459. Anal. Calcd for C26H25NO2P2· CH2Cl2: C, 61.15; H, 5.13; N, 2.64. Found: C, 61.34; H, 5.27; N, 2.83.24 1b (method I*, isolation A): white solid, 192.8 mg (84%). Mp: 95− 105 °C. 1H NMR (CDCl3): δ 8.17 (t, 3JH−H = 7.0 Hz, 4H), 7.89 (bs, 4H), 7.38 (t, 3JH−H = 7.0 Hz, 2H), 7.34−7.31 (m, 6H), 7.24−7.21 (m, 4H), 2.36 (t, 3JH−P = 12.0 Hz, 2H), 1.98−1.90 (m, 2H), 0.76 (t, 3JH−H = 6.0 Hz, 3H). 13C{1H} NMR (CDCl3): δ 132.4 (vt,22 JC−P = 4.0 Hz), 132.3 (vt,22 JC−P = 4.0 Hz), 131.7, 131.3, 130.4 (dd,23 JC−P = 93.0 Hz, JC−P = 8.0 Hz), 128.2, 61.9 (t, JC−P = 66.0 Hz), 28.2, 7.6 (t, JC−P = 7.0 Hz). 13C{1H, 31P} NMR (CDCl3): δ 132.7, 132.6, 131.8, 131.4, 128.3, 28.2, 7.7. 31P{1H} NMR (CDCl3): δ 32.0. IR (cm−1): 3283.11 (w), 3057.08 (w), 2972.40 (w), 1598.44 (m), 1482.73 (w), 1335.35 (w), 1174.18 (s), 1154.55 (m), 1131.42 (m), 1107.79 (s), 1093.07 (m), 1074.39 (m), 1045.92 (m), 1022.49 (w), 996.89 (w), 908.16 (w), 818.16 (w). HRMScalc for C27H28NO2P2 [M + H+]: 460.1595. HRMSmeas: 460.1594. Anal. Calcd for C27H27NO2P2·CH2Cl2: C, 61.78; H, 5.37; N, 2.57. Found: C, 61.45; H, 5.06; N, 2.35.24 1c25 (method II*+, isolation B): orange solid, 163.8 mg (67%). Mp: 110−120 °C. 1H NMR (C6D6): δ 7.53−7.49 (m, 5H), 7.06−6.99 (m, 15H), 2.07−2.03 (m, 2H), 1.92−1.86 (m, 2H), 1.37 (s, 3H), 1.33 (bs, 2H). 13C{1H} NMR (C6D6): δ 133.0, 132.4, 131.9 (d, JC−P = 3.0 Hz), 130.9 (d, JC−P = 9.0 Hz), 128.8 (d, JC−P = 12.0 Hz), 128.3, 118.7 (d, JC−P = 18.0 Hz), 77.6 (t, JC−P = 32.0 Hz), 26.1, 25.7, 9.9. 31P{1H} NMR (C6D6): δ 27.6. IR (cm−1): 3055.16 (w), 2934.30 (w), 2245.78 (w), 2175.47 (w), 1590.10 (w), 1484.89 (m), 1435.96 (m), 1310.73 (w), 1151.57 (s), 1127.77 (s), 1099.95 (s), 1070.08 (w), 1045.21 (s), 1021.98 (m), 997.03 (m), 923.76 (w), 853.19 (w), 748.10 (m), 722.52 (s), 693.33 (s), 555.73 (m). HRMScalc for C28H29KNO3P2 [M + K+]: 528.1260. HRMSmeas: 528.1262. 1d25 (method II*+, isolation B): white solid, 175.8 mg (70%). Mp: 115−125 °C. 1H NMR (C6D6): δ 7.49−7.46 (m, 5H), 7.03−6.97 (m, 15H), 1.99−1.97 (m, 2H), 1.80−1.76 (m, 2H), 1.37 (s, 6H), 1.32 (bs, 2H). 13C{1H} NMR (C6D6): δ 133.2, 132.5, 131.8 (d, JC−P = 3.0 Hz), 130.8 (d, JC−P = 9.0 Hz), 128.8 (d, JC−P = 11.0 Hz), 128.4, 128.2, 118.5 (d, JC−P = 19.0 Hz), 31.0 (t, JC−P = 31.0 Hz), 26.2, 25.7, 9.9. 31P{1H} NMR (C6D6): δ 27.5. IR (cm−1): 3125.07 (w), 3052.08 (w), 1590.12 (w), 1464.86 (w), 1435.74 (m), 1311.52 (w), 1259.83 (m), 1202.83 (m), 1093.12 (w), 946.74 (w), 796.54 (s), 720.17 (s), 692.30 (s), 569.40 (w), 537.52 (w). HRMScalc for C29H32KN2O2P2 [M+K+]: 541.1576. HRMSmeas: 541.1580. 1e (method I, reaction was stopped after 2 h by adding a few drops of water deactivating the catalysis, the product was isolated from the organic layer and extracted into diethyl ether (10 mL)): white solid, 39.0 mg (20%). Mp: 245−250 °C. 1H NMR (CDCl3): δ 7.93 (t, 3JH−H = 9.0 Hz, 1H), 7.75 (t, 3JH−H = 10.0 Hz, 4H), 7.71−7.67 (m, 3H), 7.66−7.64 (m, 2H), 7.60−7.55 (m, 2H), 7.51−7.43 (m, 5H), 7.40− 7.28 (m, 8H). 13C{1H} NMR (CDCl3): δ 136.7 (d, JC−P = 63.0 Hz), 135.6, 133.4 (t, JC−P = 4.0 Hz), 133.0 (t, JC−P = 4.0 Hz), 132.9, 132.7 (d, JC−P = 3.0 Hz), 132.2, 131.8 (d, JC−P = 23.0 Hz), 131.6, 131.3 (d, JC−P = 10.0 Hz), 131.1 (d, JC−P = 24.0 Hz), 130.8 (d, JC−P = 12.0 Hz), 129.1 (d, JC−P = 23.0 Hz), 128.1 (d, JC−P = 13.0 Hz), 128.1−128.0 (m), 127.7−127.6 (m), 119.0, 112.5, 66.0 (t, JC−P = 63.0 Hz). 31P{1H} NMR (CDCl3): δ 34.2. IR (cm−1): 3065.90 (w), 1589.43 (w), 1430.00 (m), 1175.95 (s), 1135.19 (m), 1017.60 (m), 870.15 (w), 719.34 (s),

investigation of the catalytic cycle implied that the 1,1-addition products were in fact kinetic products, while the 1,2-addition products were thermodynamic products. All catalyses were effected at either room temperature or 80 °C neat or with very little solvent and required little workup while giving moderate to high yields. The 1,2-addition products from these reactions, bearing P−C−N−P linkages, are related to the highly successful bis(phosphino)ethane ligands, such as dmpe and dppe. We envision these hydrophosphinylation products and their deoxygenated derivatives as useful new entries to unsymmetric and electronically tunable versions of this versatile ligand set. Their use in catalysis remains a topic of continued study in our laboratory.

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EXPERIMENTAL SECTION

Lanthanum tris(N,N-dimethylbenzylamine) (La(Dmba)3) was synthesized as previously reported.18 Diphenylphosphine oxide was purchased from AK Scientific and was transferred into the glovebox and used without any further purification. All nitriles were purchased from Alfa Aesar, Aldrich, Acros, and AK Scientific, dried over calcium hydride, filtered, freeze−pump−thawed three times, and stored in a nitrogen-filled glovebox. Pyridine was purchased from Alfa Aesar and dried over sodium metal, distilled under nitrogen, freeze−pump− thawed three times, and stored in a nitrogen-filled glovebox. All 1H and 13C NMR spectra were collected on a 600 MHz Bruker Avance III spectrometer at 599.9 and 150.8 MHz, respectively, and referenced to the residual solvent peaks of CDCl3 at 7.26 and 77.3 ppm and C6D6 at 7.16 and 128.0 ppm, respectively. All 31P and 19F NMR spectra were collected on a 400 MHz Varian VXRS NMR spectrometer at 161.9 and 376.0 MHz, respectively; 31P NMR spectra were externally referenced to 0.00 ppm with 5% H3PO4 in D2O, and 19F NMR spectra were referenced to CFCl3 at 0.00 ppm. Infrared spectra were collected on a PerkinElmer Frontier spectrometer with Pike miracle ATR. Highresolution mass spectra were determined by the University of Illinois Mass Spectrometry Laboratory, Urbana, IL, USA, or at the Department of Chemistry and Biochemistry, University of Toledo, OH, USA, using a Waters Synapt high-definition mass spectrometer (HDMS) equipped with a nano-ESI source. Catalytic Procedure. All catalytic reactions were performed in oven-dried glassware under a nitrogen atmosphere. Unless otherwise stated, all reactions were run at room temperature. Reactions were set up using the following two methods. Method I. La(Dmba)3 (27 mg, 0.050 mmol, 10 mol %) and diphenylphosphine oxide (202 mg, 1 mmol, limiting reagent) were dissolved in the appropriate nitrile (2 mL). Entries denoted with a “+” used La(Dmba)3 (54 mg, 0.10 mmol, 20 mol %). The reactions were stirred under inert conditions for the respective times and conditions outlined in Tables 1 and 2. Method II. La(Dmba)3 (27 mg, 0.050 mmol, 10 mol %), diphenylphosphine oxide (303 mg, 1.5 mmol), and nitrile (0.5 mmol, limiting reagent) were dissolved in pyridine (2 mL). Entries denoted with a “+” used La(Dmba)3 (54 mg, 0.10 mmol, 20 mol %). The reactions were stirred under inert conditions for the respective times and conditions outlined in Tables 1 and 2. Isolation Procedure. All isolations were carried out under an ambient atmosphere. The reaction solvent was removed under reduced pressure, and the indicated products were obtained using the following methods. Isolation A. The crude reaction product was washed three times with diethyl ether (5 mL each) to remove any unreacted starting material. The residual solid was then extracted with dichloromethane three times (5 mL each), leaving behind any lanthanum salts. The combined dichloromethane extracts were then dried to a solid under reduced pressure to obtain the clean reaction product. Isolation B. The crude reaction product was dissolved in diethyl ether (5 mL) and then triturated with hexanes three times (3 mL each). The precipitate was removed via filtration, and the organic E

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Organometallics

Hz), 132.1 (d, JC−P = 10.0 Hz), 132.0 (d, JC−P = 3.0 Hz), 131.8 (d, JC−P = 3.0 Hz), 131.7−131.6 (m), 131.5 (d, JC−P = 9.0 Hz), 131.3 (d, JC−P = 6.0 Hz), 130.5 (d, JC−P = 5.0 Hz), 129.6 (d, JC−P = 5.0 Hz), 128.9− 128.8 (m), 128.7 (d, JC−P = 5.0 Hz), 128.4 (d, JC−P = 12.0 Hz), 128.2 (d, JC−P = 10.0 Hz), 128.1−127.9 (m), 127.7 (d, JC−P = 2.0 Hz), 125.9 (d, JC−P = 5.0 Hz), 53.7 (d, JC−P = 74.0 Hz), 53.6 (d, JC−P = 74.0 Hz), 21.3, 21.2. 31P{1H} NMR (CDCl3): δ 34.6 (m), 26.9 (m). IR (cm−1): 3205.18 (w), 3057.47 (w), 1592.80 (w), 1436.04 (m), 1177.36 (s), 1173.66 (s), 1075.67 (s), 912.89 (w), 872.06 (m), 749.34 (m), 720.05 (s), 690.92 (s), 619.13 (m), 555.79 (w), 498.53 (w). HRMScalc: 522.1752 for C32H30NO2P2 [M + H+]; HRMSmeas: 522.1750. 2e (method I, isolation A): white solid, 225 mg (86%). Mp: 245− 254 °C. 1H NMR (CDCl3): δ 8.12 (t, 3JH−H = 9.0 Hz, 2H), 7.64−7.57 (m, 3H), 7.53 (dd, 3JH−P = 12.6 Hz, 3JH−H = 7.8 Hz, 2H), 7.42−7.39 (m, 1H), 7.36−7.29 (m, 4H), 7.25−7.14 (m, 8H), 7.00 (d, 3JH−H = 7.8 Hz, 1H), 6.89−6.82 (m, 3H), 5.23 (q, 2JH−P = 3JH−P = 3JH−H = 10.2 Hz, 1H), 4.81 (bs, 1H), 2.04 (s, 3H). 13C{1H} NMR (CDCl3): δ 139.3, 138.3, 137.4, 136.1, 133.7, 132.7, 132.6 (d, JC−P = 6.0 Hz), 132.4 (d, JC−P = 6.0 Hz), 132.2 (d, JC−P = 9.0 Hz), 131.9, 131.8, 131.7 (d, JC−P = 10.4 Hz), 131.5, 131.3 (d, JC−P = 9.0 Hz), 131.1 (d, JC−P = 7.5 Hz), 129.6 (d, JC−P = 5.2 Hz), 129.4, 129.1, 128.8 (d, JC−P = 11.3 Hz), 128.3 (d, JC−P = 12.9 Hz), 128.0 (d, JC−P = 19.6 Hz), 127.9 (d, JC−P = 20.6 Hz), 126.0 (d, JC−P = 4.5 Hz), 53.5 (d, JC−P = 75.4 Hz), 21.2. 31 1 P{ H} NMR (CDCl3): δ 34.4 (d, 3JP−P = 26.7 Hz), 27.5 (d, 3JP−P = 26.7 Hz). IR (cm−1): 3207.48 (w), 3056.85 (w), 1591.95 (w), 1436.07 (m), 1197.88 (m), 1187.78 (m), 1046.27 (m), 1025.75 (m), 870.50 (m), 748.75 (m), 720.89 (s), 691.29 (s), 623.39 (w), 576.95 (w), 476.62 (w). HRMScalc: 522.1752 for C32H30NO2P2 [M + H+]; HRMSmeas: 522.1749. 2f (method I, isolation A): white solid, 170 mg (64%). Mp: 258− 264 °C. 1H NMR (CDCl3): δ 8.10 (t, 3JH−H = 9.0 Hz, 2H), 7.76−7.64 (m, 6H), 7.41−7.38 (m, 2H), 7.30 (t, 3JH−H = 9.0 Hz, 1H), 7.31−7.27 (m, 1H), 7.22−7.21 (m, 7H), 7.14−7.12 (m, 2H), 7.05−7.02 (m, 1H), 6.93 (t, 3JH−H = 7.0 Hz, 1H), 6.52 (t, 3JH−H = 9.0 Hz, 1H), 5.64 (q, 2 JH−P = 3JH−P = 3JH−H = 10.3 Hz, 1H), 5.23 (bs, 1H). 13C{1H} NMR (CDCl3): δ 163.3 (d, JC−F = 258.0 Hz), 159.3 (d, JC−F = 245.0 Hz), 135.1 (d, JC−F = 8.0 Hz), 133.6, 132.7, 132.4 (d, JC−P = 2.0 Hz), 132.3 (d, JC−P = 10.0 Hz), 132.1 (d, JC−P = 9.0 Hz), 131.8 (d, JC−P = 11.0 Hz), 131.7 (d, JC−P = 2.0 Hz), 131.1 (d, JC−P = 9.0 Hz), 130.1 (d, JC−P = 50.0 Hz), 129.8 (d, JC−P = 50.0 Hz), 129.3 (d, JC−P = 7.0 Hz), 128.9 (d, JC−P = 12.0 Hz), 128.3 (d, JC−P = 13.0 Hz), 128.0 (d, JC−P = 10.0 Hz), 124.9 (d, JC−F = 4.0 Hz), 116.6 (d, JC−F = 19.0 Hz), 114.5 (d, JC−P = 22.1 Hz), 114.1, 101.7 (d, JC−F = 15.0 Hz), 45.9 (d, JC−P = 76.3 Hz). 31 1 P{ H} NMR (CDCl3): δ 34.4 (d, 3JP−P = 24.7 Hz), 26.5 (d, 3JP−P = 24.7 Hz). 19F{1H} NMR (CDCl3): δ −117.6 (s). IR (cm−1): 3145.88 (m), 1588.49 (w), 1489.64 (w), 1437.50 (m), 1312.34 (w), 1227.96 (w), 1188.38 (s), 1122.65 (s), 1098.10 (m), 996.78 (m), 884.85 (w), 807.62 (w), 779.06 (m), 750.40 (s), 724.88 (s), 692.85 (s), 617.93 (w), 567.56 (m), 544.57 (w), 489.36 (w). HRMS calc for C31H27FNO2P2 [M + H+]: 526.1501. HRMSmeas: 526.1486. 2g (method II, isolation A): white solid, 231.5 mg (88%). Mp: 250−254 °C. 1H NMR (CDCl3): δ 8.13 (t, 3JH−H = 9.0 Hz, 2H), 7.68−7.56 (m, 5H), 7.41 (td, 3JH−H = 7.0 Hz, 4JH−H = 1.0 Hz, 1H), 7.35−7.25 (m, 4H), 7.23−7.15 (m, 8H), 6.92−6.87 (m, 3H), 6.73 (t, 3 JH−H = 9.0 Hz, 1H), 5.31 (q, 2JH−P = 3JH−P = 3JH−H = 10.0 Hz, 1H), 5.11 (bs, 1H). 13C{1H} NMR (CDCl3): 162.4 (d, JC−F = 248.4 Hz), 149.9, 133.0, 132.3 (d, JC−P = 10.0 Hz), 132.1 (d, JC−P = 9.0 Hz), 132.0 (d, JC−P = 15.0 Hz), 131.6 (d, JC−P = 11.0 Hz), 131.1 (d, JC−F = 9.0 Hz), 130.4 (dd, JC−P = 96.7 Hz, JC−P = 20.0 Hz), 129.3 (d, JC−P = 9.0 Hz), 128.9 (d, JC−P = 12.0 Hz), 128.4 (d, JC−P = 13.0 Hz), 128.2 (d, JC−P = 12.0 Hz), 128.0 (d, JC−P = 13.0 Hz), 124.7, 115.9 (dd, JC−P = 22.0 Hz, JC−F = 4.5 Hz), 114.5 (d, JC−F = 21.0 Hz), 53.0 (d, JC−P = 74.8 Hz). 31P{1H} NMR (CDCl3): δ 34.4 (d, 3JP−P = 26.7 Hz), 27.5 (d, 3 JP−P = 26.7 Hz). 19F{1H} NMR (CDCl3): δ −113.7 (s). IR (cm−1): 3206.58 (s), 3055.66 (s), 1586.40 (s), 1436.70 (s), 1265.29 (s), 1178.47 (s), 1124.32 (s), 882.85 (b), 738.06 (s). HRMScalc for C31H27FNO2P2 [M + H+]: 526.1501. HRMSmeas: 526.1486. 2h (method I, isolation A): white solid, 231 mg (88%). Mp: 255− 260 °C. 1H NMR (CDCl3): δ 8.15 (t, 3JH−H = 9.0 Hz, 2H), 7.68−7.45

695.23 (s), 565.70 (m), 482.64 (w). HRMScalc for C31H28NO2P2 [M + H+]: 508.1595. HRMSmeas: 508.1595. 2a (method I, isolation A):14a white solid, 228 mg (90%). Mp: 245−250 °C. 1H NMR (CDCl3): δ 8.14 (t, 3JH−H = 9.0 Hz, 2H), 7.66−7.57 (m, 6H), 7.47 (t, 3JH−H = 8.0 Hz, 1H), 7.39−7.27 (m, 4H), 7.17−7.15 (m, 5H), 7.11−7.09 (m, 4H), 7.02 (d, 3JH−H = 7.4 Hz, 1H), 6.10 (d, 3JH−H = 8.0 Hz, 2H), 5.46 (bs, 1H), 5.35 (q, 2JH−P = 3JH−H = 3 JH−H = 10.6 Hz, 1H). 13C{1H} NMR (CDCl3): δ 136.1, 133.5, 132.9, 132.4 (d, JC−P = 86.7 Hz), 132.3 (d, JC−P = 10.0 Hz), 132.2 (d, JC−P = 9.0 Hz), 131.7, 131.6, 131.6 (d, JC−P = 2.1 Hz), 131.4 (d, JC−P = 1.2 Hz), 131.3, 131.1 (d, JC−P = 9.0 Hz), 130.6 (d, JC−P = 18.5 Hz), 130.2, 129.1 (d, JC−P = 4.6 Hz), 128.8 (d, JC−P = 11.7 Hz), 128.3 (d, JC−P = 12.7 Hz), 128.1 (d, JC−P = 11.7 Hz), 127.9, 127.8, 127.4, 119.0, 112.6, 53.4 (d, JC−P = 76.1 Hz). 31P{1H} NMR (CDCl3): δ 34.5 (d, 3JP−P = 26.5 Hz), 27.3 (d, 3JP−P = 26.5 Hz). IR (cm−1): 3174.83 (w), 3056.39 (w), 1592.53 (w), 1435.84 (m), 1178.08 (s), 1121.19 (m), 1027.48 (m), 876.15 (w), 721.34 (s), 690.23 (s), 556.92 (m), 486.46 (w). HRMScalc for C31H28NO2P2 [M + H+]: 508.1595. HRMSmeas: 508.1586. Anal. Calcd for C31H27NO2P2: C, 73.37; H, 5.36; N, 2.76. Found: C, 72.73; H, 5.34; N, 3.00. 2b (method II, isolation A): white solid, 243 mg (90%). Mp: 249− 255 °C. 1H NMR (CDCl3): δ 8.15 (t, 3JH−H = 9.0 Hz, 2H), 7.67−7.65 (m, 1H), 7.63−7.57 (m, 4H), 7.40 (td, 3JH−H = 7.5 Hz, 4JH−H = 1.3 Hz, 1H), 7.37−7.30 (m, 4H), 7.22−7.12 (m, 8H), 7.09 (dd, 3JH−H = 8.3 Hz, 4JH−H = 1.5 Hz, 2H), 6.91 (d, 3JH−H = 8.3 Hz, 2H), 5.46 (bs, 1H), 5.33 (q, 2JH−P = 3JH−P = 3JH−H = 10.3 Hz, 1H). 13C{1H} NMR (CDCl3): δ 134.8, 133.4, 133.3 (d, JC−P = 79.6 Hz), 132.6, 132.3 (d, JC−P = 10.0 Hz), 132.1 (d, JC−P = 9.0 Hz), 131.9 (d, JC−P = 7.5 Hz), 131.7 (d, JC−P = 10.0 Hz), 131.6, 131.1 (d, JC−P = 9.0 Hz), 130.8 (d, JC−P = 11.0 Hz), 130.3 (d, JC−P = 4.7 Hz), 130.2 (d, JC−P = 11.0 Hz), 128.9 (d, JC−P = 11.3 Hz), 128.3 (d, JC−P = 9.0 Hz), 128.2 (d, JC−P = 8.0 Hz), 128.0, 127.9 (d, JC−P = 4.3 Hz), 52.7 (d, JC−P = 73.1 Hz). 31 1 P{ H} NMR (CDCl3): δ 34.2 (d, 3JP−P = 26.7 Hz), 27.5 (d, 3JP−P = 26.7 Hz). IR (cm−1): 3175.07 (w), 3057.68 (w), 2936.13 (w), 1592.46 (w), 1487.16 (w), 1435.96 (m), 1177.79 (s), 1121.70 (m), 1073.80 (m), 878.82 (m), 749.24 (w), 721.50 (s), 691.16 (s), 539.31 (w), 454.06 (w). HRMScalc for C31H27ClNO2P2 [M + H+]: 542.1206. HRMSmeas: 542.1206. Anal. Calcd for C31H26ClNO2P2: C, 68.70; H, 4.84; N, 2.58. Found: C, 68.92; H, 5.24; N, 2.32. 2c (method II, isolation A): white solid, 245 mg (85%). Mp: 260− 264 °C. 1H NMR (CDCl3): δ 8.19 (t, 3JH−H = 8.0 Hz, 2H), 7.69−7.55 (m, 5H), 7.40 (t, 3JH−H = 7.0 Hz, 1H), 7.35−7.29 (m, 4H), 7.26−7.25 (m, 2H), 7.18−7.11 (m, 10H), 5.51 (bs, 1H), 5.05 (q, 2JH−P = 3JH−P = 3 JH−H = 9.2 Hz, 1H). 13C{1H} NMR (CDCl3): δ 140.2, 132.6 (d, JC−P = 92.2 Hz), 132.4, 132.1 (d, JC−P = 10.0 Hz), 132.0 (d, JC−P = 9.0 Hz), 131.9, 131.5 (d, JC−P = 10.0 Hz), 130.9 (d, JC−P = 9.0 Hz), 130.5 (d, JC−P = 5.8 Hz), 129.8 (d, JC−P = 5.8 Hz), 129.4, 129.2 (d, JC−P = 4.3 Hz), 128.9 (d, JC−P = 11.0 Hz), 128.2 (d, JC−P = 9.0 Hz), 128.1 (d, JC−P= 8.0 Hz), 127.8 (d, JC−P = 13.0 Hz), 124.5, 52.9 (d, JC−P = 75.4 Hz). 31P{1H} NMR (CDCl3): δ 34.2 (d, 3JP−P = 27.3 Hz), 27.8 (d, 3 JP−P = 27.3 Hz). 19F{1H} NMR (CDCl3): δ −63.1 (s). IR (cm−1): 3159.04 (w), 3058.16 (w), 2928.89 (w), 1591.93 (w), 1437.67 (m), 1326.83 (m), 1179.96 (s), 1116.31 (s), 1068.96 (m), 998.49 (w), 882.04 (m), 857.65 (w), 748.38 (w), 724.07 (s), 692.33 (s), 647.68 (w), 542.79 (w), 457.14 (w). HRMScalc for C32H27F3NO2P2 [M + H+]: 576.1469. HRMSmeas: 576.1473. 2d, because of hindered rotation, two diastereomeric atropisomers were observed in solution in a 2:1 ratio. The diastereomers were inseparable; herein is the spectroscopic analysis of the mixture of the diastereomers (method I, isolation A): white solid, 203 mg (78%). Mp: 250−255 °C. 1H NMR (CDCl3): δ 8.14−8.07 (m, 7H), 7.65− 7.56 (m, 10H), 7.51−7.47 (m, 7H), 7.43−7.40 (m, 3H), 7.36−7.28 (m, 14H), 7.25−7.23 (m, 8H), 7.21−7.17 (m, 10H), 7.13 (d, 3JH−H = 7.0 Hz, 2H), 7.09−7.06 (m, 1H), 7.03−7.00 (m, 4H), 6.97 (d, 3JH−H = 7.0 Hz, 1H), 6.93 (t, 3JH−H = 7.0 Hz, 1H), 6.87−6.83 (m, 4H), 5.24 (q, 2 JH−P = 3JH−P = 3JH−H = 9.0 Hz, 1H), 5.17 (q, 2JH−P = 3JH−P = 3JH−H = 9.0 Hz, 2H), 4.61 (bs, 1H), 4.50 (bs, 2H), 2.21 (s, 3H), 2.08 (s, 6H). 13 C{1H} NMR (CDCl3): δ 147.6, 137.3, 136.4, 136.1, 133.4, 132.9, 132.4 (d, JC−P = 9.0 Hz), 132.3 (d, JC−P = 3.0 Hz), 132.2 (d, JC−P = 9.0 F

DOI: 10.1021/acs.organomet.6b00919 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics (m, 6H), 7.40 (t, 3JH−H = 7.2 Hz, 1H), 7.36−7.30 (m, 4H), 7.21−7.11 (m, 9H), 6.61 (d, 3JH−H = 8.0 Hz, 2H), 5.33 (bs, 1H), 5.25 (q, 2JH−P = 3 JH−P = 3JH−H = 10.9 Hz, 1H). 13C{1H} NMR (CDCl3): δ 162.1 (d, JC−F = 55.0 Hz), 132.7 (d, JC−P = 81.1 Hz), 132.2 (d, JC−P = 11.0 Hz), 132.0 (d, JC−F = 9.0 Hz), 131.7 (d, JC−P = 18.0 Hz), 131.5 (d, JC−P = 11.0 Hz), 131.0 (d, JC−P = 9.0 Hz), 130.8 (d, JC−P = 22.0 Hz), 130.5 (d, JC−P = 5.2 Hz), 130.1 (d, JC−P = 21.0 Hz), 128.8 (d, JC−P = 11.0 Hz), 128.4 (d, JC−P = 13.0 Hz), 128.1 (d, JC−P = 12.0 Hz), 127.8 (d, JC−P = 13.0 Hz), 114.6 (d, JC−F = 21.0 Hz), 52.5 (d, JC−P = 75.8 Hz). 31 1 P{ H} NMR (CDCl3): δ 34.4 (d, 3JP−P = 27.3 Hz), 27.6 (d, 3JP−P = 27.3 Hz). 19F{1H} NMR (CDCl3): δ −115.1 (s). IR (cm−1): 3173.57 (w), 3055.40 (w), 1603.51 (w), 1509.68 (w), 1436.77 (m), 1225.45 (w), 1177.13 (s), 1122.22 (s), 1070.13 (m), 1024.68 (w), 887.02 (m), 846.60 (w), 796.37 (w), 746.81 (m), 721.55 (s), 692.19 (s), 561.65 (m), 538.28 (m), 457.74 (m). HRMScalc for C31H27FNO2P2 [M + H+]: 526.1501. HRMSmeas: 526.1501. 2i (method II, isolation A): white solid, 214 mg (80%). Mp: 254− 260 °C. 1H NMR (CDCl3): δ 8.15 (t, 3JH−H = 8.0 Hz, 2H), 7.65−7.58 (m, 3H), 7.52 (t, 3JH−H = 10.0 Hz, 2H), 7.39 (t, 3JH−H = 7.5 Hz, 1H), 7.34 (t, 3JH−H = 10.0 Hz, 2H), 7.30−7.27 (m, 2H), 7.21−7.11 (m, 8H), 7.05 (d, 3JH−H = 8.0 Hz, 2H), 6.95 (d, 3JH−H = 7.5 Hz, 2H), 5.25 (q, 2JH−P = 3JH−P = 3JH−H = 9.4 Hz, 1H), 5.01 (bs, 1H), 1.20 (s, 9H). 13 C{1H} NMR (CDCl3): δ 150.3, 133.0, 132.9 (d, JC−P = 97.4 Hz), 132.4 (d, JC−P = 11.0 Hz), 132.2 (d, JC−P = 9.0 Hz), 132.0 (d, JC−P = 50.6 Hz), 131.7 (d, JC−P = 10.0 Hz), 131.5 (d, JC−P = 26.0 Hz), 131.3 (d, JC−P = 9.0 Hz), 130.6 (d, JC−P = 23.0 Hz), 128.8 (d, JC−P = 11.0 Hz), 128.6 (d, JC−P = 5.0 Hz), 128.3 (d, JC−P = 13.0 Hz), 128.0 (d, JC−P = 12.0 Hz), 127.8 (d, JC−P = 13.0 Hz), 124.8, 53.1 (d, JC−P = 76.1 Hz), 34.4, 31.4. 31P{1H} NMR (CDCl3): δ 34.5 (d, 3JP−P = 27.3 Hz), 27.3 (d, 3JP−P = 27.3 Hz). IR (cm−1): 3384.60 (br), 3054.43 (s), 2966.67 (s), 2305.64 (s), 1911.64 (s), 1437.52 (s), 1265.00 (s), 1187.90 (s), 1125.20 (s), 1046.74 (s), 895.07 (s), 738.68 (br). HRMScalc for C35H36NO2P2 [M + H+]: 564.2221. HRMSmeas: 564.2222. 2j (method II, isolation A): white solid, 239 mg (89%). Mp: 250− 255 °C. 1H NMR (CDCl3): δ 8.13 (t, 3JH−H = 9.0 Hz, 2H), 7.64−7.53 (m, 5H), 7.39 (td, 3JH−H = 7.5 Hz, 4JH−H = 1.3 Hz, 1H), 7.34−7.28 (m, 4H), 7.24−7.14 (m, 8H), 7.08 (dd, 3JH−H = 7.0 Hz, 4JH−H = 1.5 Hz, 2H), 6.50 (d, 3JH−H = 9.0 Hz, 2H), 5.25 (q, 2JH−P = 3JH−P = 3JH−H = 10.5 Hz, 1H), 4.99 (bs, 1H), 3.37 (s, 3H). 13C{1H} NMR (CDCl3): δ 159.0, 133.2, 133.0 (d, JC−P = 73.7 Hz), 132.4 (d, JC−P = 10.0 Hz), 132.2 (d, JC−P = 8.0 Hz), 132.0, 131.9 (d, JC−P = 2.0 Hz), 131.7 (d, JC−P = 10.0 Hz), 131.5 (d, JC−P = 2.0 Hz), 131.2 (d, JC−P = 9.0 Hz), 130.6 (d, JC−P = 10.0 Hz), 130.1 (d, JC−P = 5.0 Hz), 128.8 (d, JC−P = 11.7 Hz), 128.4, 128.3 (d, JC−P = 13.0 Hz), 128.2 (d, JC−P = 13.0 Hz), 127.9 (d, JC−P = 13.0 Hz), 113.4, 55.2, 52.8 (d, JC−P = 76.6 Hz). 31 1 P{ H} NMR (CDCl3): δ 34.3 (d, 3JP−P = 27.3 Hz), 27.3 (d, 3JP−P = 27.3 Hz). IR (cm−1): 3205.18 (w), 3057.47 (w), 1592.80 (w), 1436.04 (m), 1177.36 (s), 1173.66 (s), 1075.67 (s), 912.89 (w), 872.06 (m), 749.34 (m), 720.05 (s), 690.92 (s), 619.13 (m), 555.79 (w), 498.53 (w). HRMScalc for C32H30NO3P2 [M + H+]: 538.1701. HRMSmeas: 583.1708. 2k (method II, isolation A): white solid, 174.3 mg (63%). Mp: 250−260 °C. 1H NMR (CDCl3): δ 8.13 (t, 3JH−H = 13.0 Hz, 2H), 7.63−7.51 (m, 5H), 7.42 (t, 3JH−H = 15.0 Hz, 1H), 7.36−7.29 (m, 5H), 7.23−7.17 (m, 7H), 7.06 (d, 4JH−H = 2.0 Hz, 2H), 6.86 (d, 3JH−H = 8.0 Hz, 2H), 5.24 (q, 2JH−P = 3JH−P = 3JH−H = 9.0 Hz, 1H), 4.86 (bs, 1H), 2.38 (s, 3H). 13C{1H} NMR (CDCl3): δ 137.8, 133.1, 132.3 (d, JC−P = 10.0 Hz), 132.1 (d, JC−P = 9.0 Hz), 131.9 (d, JC−P = 20.5 Hz), 131.7 (d, JC−P = 10.0 Hz), 131.2 (d, JC−P = 8.0 Hz), 130.6 (d, JC−P = 95.0 Hz), 129.3 (d, JC−P= 5.0 Hz), 128.9 (d, JC−P = 12.0 Hz), 128.4 (d, JC−P = 13.0 Hz), 128.2 (d, JC−P = 12.0 Hz), 128.1 (d, JC−P = 13.0 Hz), 126.0, 53.2 (d, JC−P = 76.0 Hz), 15.8. 31P{1H} NMR (CDCl3): δ 34.3 (d, 3JP−P = 27.5 Hz), 27.5 (d, 3JP−P = 27.5 Hz). IR (cm−1): 3172.67 (w), 3054.72 (w), 2936.23 (w), 1593.39 (w), 1489.99 (m), 1435.46 (s), 1409.78 (w), 1336.11 (w), 1260.36 (s), 1178.36 (s), 1121.03 (s), 1090.97 (m), 1072.48 (s), 1039.04 (s), 1027.25 (s), 1016.24 (s), 969.78 (w), 948.45 (w), 923.43 (w), 879.06 (m). HRMScalc for C32H30NO2P2S [M + H+]: 554.1472. HRMSmeas: 554.1467.

2l (method II*, isolation A): white solid, 195 mg (71%). Mp: 240− 246 °C. 1H NMR (CDCl3): δ 8.08 (t, 3JH−H = 9.0 Hz, 2H), 7.62−7.59 (m, 3H), 7.51 (td, 3JH−H = 10.0 Hz, 4JH−H = 4.5 Hz, 2H), 7.39 (t, 3JH−H = 7.5 Hz, 1H), 7.37−7.28 (m, 7H), 7.24−7.19 (m, 5H), 7.00 (d, 3JH−H = 8.0 Hz, 2H), 6.40 (d, 3JH−H = 9.0 Hz, 2H), 5.11 (q, 2JH−P = 3JH−P = 3 JH−H = 10.5 Hz, 1H), 4.40 (bs, 1H), 2.85 (s, 6H). 13C{1H} NMR (CDCl3): δ 150.1, 133.1, 132.4 (d, JC−P = 10.0 Hz), 132.2 (d, JC−P = 9.0 Hz), 132.0 (d, JC−P = 33.0 Hz), 131.7 (d, JC−P = 10.0 Hz), 131.6 (d, JC−P = 13.0 Hz), 131.4 (d, JC−P = 9.0 Hz), 131.3 (d, JC−P = 9.0 Hz), 130.7, 130.4 (d, JC−P = 4.0 Hz), 129.6 (d, JC−P = 5.0 Hz), 128.7 (d, JC−P = 47.0 Hz), 128.3 (d, JC−P = 13.0 Hz), 128.1 (d, JC−P = 12.0 Hz), 128.0 (d, JC−P = 13.0 Hz), 124.0, 113.5, 112.3, 53.2 (d, JC−P = 78.0 Hz), 40.7. 31P{1H} NMR (CDCl3): δ 34.5 (d, 3JP−P = 27.3 Hz), 27.3 (d, 3JP−P = 27.3 Hz). IR (cm−1): 3053.00 (br), 1612.23 (w), 1520.68 (w), 1435.76 (m), 1129.38 (s), 1046.54 (s), 881.65 (m), 721.89 (s), 691.85 (s), 558.17 (m), 532.25 (w). HRMScalc for C33H33N2O2P2 [M + H+]: 551.2017. HRMSmeas: 551.2020. 2n (method II*, isolation A): white solid, 167 mg (60%). Mp: 270− 280 °C. 1H NMR (CDCl3): δ 8.17 (t, 3JH−H = 8.0 Hz, 2H), 7.70−7.61 (m, 4H), 7.53−7.47 (m, 5H), 7.43−7.28 (m, 8H), 7.24−7.16 (m, 4H), 7.10−7.08 (m, 2H), 7.06 (td, 3JH−H = 8.0 Hz, 4JH−H = 3.0 Hz, 2H), 5.46 (q, 2JH−P = 3JH−P = 3JH−H = 10.0 Hz, 1H), 4.86 (bs, 1H). 13C{1H} NMR (CDCl3): δ 133.7 (d, JC−P = 6.0 Hz), 132.7 (d, JC−P = 21.0 Hz), 132.3, 132.2 (d, JC−P = 14.0 Hz), 132.1, 131.9 (d, JC−P = 28.0 Hz), 131.6 (d, JC−P = 10.0 Hz), 131.2 (d, JC−P = 9.0 Hz), 129.2, 128.9 (d, JC−P = 12.0 Hz), 128.8 (d, JC−P = 12.0 Hz), 128.3, 128.2, 127.9, 127.8, 127.7 (d, JC−P = 6.0 Hz), 127.4, 127.2, 126.3 (d, JC−P = 4.0 Hz), 125.8 (d, JC−P = 18.0 Hz), 53.7 (d, JC−P = 73.9 Hz). 31P{1H} NMR (CDCl3): δ 34.6 (d, 3JP−P = 25.9 Hz), 27.3 (d, 3JP−P = 25.9 Hz). IR(cm−1): 3182.00 (w), 3054.05 (w), 2962.94 (w), 1591.61 (w), 1509.48 (w), 1435.16 (s), 1260.09 (s), 1195.90 (m), 1176.70 (m), 1096.65 (s), 1075.87 (s), 1016.96 (s), 952.89 (m), 915.78 (m), 896.74 (w), 875.33 (w). HRMScalc for C35H30NO2P2 [M + H+]: 558.5620. HRMSmeas: 558.5626. 2o (method I+, isolation A): white solid, 185.0 mg (72%). Mp: 120−130 °C. 1H NMR (CDCl3): δ 7.89 (t, 3JH−H = 7.8 Hz, 2H), 7.77−7.72 (m, 4H), 7.51−7.48 (m, 3H), 7.46−7.43 (m, 6H), 7.33 (t, 3 JH−H = 7.2 Hz, 1H), 7.14−7.08 (m, 4H), 4.16 (q, 2JH−P = 3JH−P = 3 JH−H = 10.6 Hz, 1H), 3.73 (bs, 1H), 2.03−1.99 (m, 1H), 1.61−1.54 (m, 3H), 1.46−1.39 (m, 3H), 1.25−1.15 (m, 1H), 1.00−0.87 (m, 3H). 13 C{1H} NMR (CDCl3): δ 134.2, 133.4, 133.0, 132.6 (dd, JC−P = 24.1 Hz, JC−P = 5.0 Hz), 132.1 (d, JC−P = 8.0 Hz), 132.0 (d, JC−P = 4.0 Hz), 131.9 (d, JC−P = 4.0 Hz), 131.6 (d, JC−P = 3.0 Hz), 130.9 (d, JC−P = 9.0 Hz), 129.1 (d, JC−P = 13.0 Hz), 128.9 (d, JC−P = 11.0 Hz), 128.6 (d, JC−P = 11.0 Hz), 128.5 (d, JC−P = 12.0 Hz), 128.2 (d, JC−P = 13.0 Hz), 54.2 (d, JC−P = 78.0 Hz), 39.6 (d, JC−P = 5.0 Hz), 31.7 (d, JC−P = 12.0 Hz), 27.8, 26.7, 26.2, 25.9. 31P{1H} NMR (CDCl3): δ 35.0 (d, 3JP−P = 24.4 Hz), 26.1 (d, 3JP−P = 24.4 Hz). IR(cm−1): 3053.68 (w), 2924.14 (w), 1484.54 (w), 1436.21 (m), 1179.76 (m), 1129.20 (s), 1044.88 (s), 1021.05 (s), 998.16 (m), 899.74 (w), 847.99 (w), 747.99 (m), 723.68 (m), 693.21 (s), 555.88 (s), 490.79 (w), 476.73 (w), 465.72 (w). HRMScalc for C31H34NO2P2 [M + H+]: 514.2065. HRMSmeas: 514.2071. 2p (method I, isolation A): white solid, 161.0 mg (85%). Mp: 115− 120 °C. 1H NMR (CDCl3): δ 7.92 (t, 3JH−H = 9.0 Hz, 2H), 7.79 (t, 3 JH−H = 8.0 Hz, 2H), 7.77−7.74 (m, 3H), 7.51−7.41 (m, 8H), 7.32 (td, 3JH−H = 7.0 Hz, 4JH−H = 1.4 Hz, 1H), 7.14−7.07 (m, 4H), 4.27 (q, 2 JH−P = 3JH−P = 3JH−H = 9.0 Hz, 1H), 3.69−3.64 (m, 1H), 1.94 (bs, 1H), 1.01 (d, 3JH−H = 7.0 Hz, 3H), 0.90 (d, 3JH−H = 7.0 Hz, 3H). 13 C{1H} NMR (CDCl3): δ 132.7, 132.0, 131.9 (d, JC−P = 12.0 Hz), 131.6 (d, JC−P = 9.0 Hz), 130.9 (d, JC−P = 9.0 Hz), 128.9 (d, JC−P = 11.0 Hz), 128.7 (d, JC−P = 11.0 Hz), 128.5 (d, JC−P = 13.0 Hz), 128.2 (d, JC−P = 13.0 Hz), 54.1 (dd, JC−P = 77.0 Hz, JC−P = 3.0 Hz), 29.3 (d, JC−P = 3.0 Hz), 21.9 (d, JC−P = 14.0 Hz), 17.2. 31P{1H} NMR (CDCl3): δ 34.6 (d, 3JP−P = 22.0 Hz), 26.3 (d, 3JP−P = 22.0 Hz). IR(cm−1): 3193.20 (w), 3055.39 (w), 1484.62 (w), 1436.01 (m), 1179.33 (s), 1156.30 (s), 1127.49 (s), 1045.69 (s), 1021.44 (m), 998.05 (w), 869.59 (w), 825.11 (w). HRMScalc for C28H30NO2P2 [M + H+]: 474.1752. HRMSmeas: 474.1791. G

DOI: 10.1021/acs.organomet.6b00919 Organometallics XXXX, XXX, XXX−XXX

Organometallics 2r (method I, isolation A): white solid, 229.0 mg (88%). Mp: 250− 260 °C. 1H NMR (CDCl3): δ 8.07−8.04 (m, 2H), 7.58−7.56 (m, 3H), 7.55−7.52 (m, 2H), 7.44 (td, 3JH−H = 7.4 Hz, 4JH−H = 1.2 Hz, 1H), 7.38−7.33 (m, 3H), 7.31−7.29 (m, 4H), 7.19 (td, 3JH−H = 7.4 Hz, 4 JH−H = 1.2 Hz, 1H), 7.15 (td, 3JH−H = 9.6 Hz, 4JH−H = 2.8 Hz, 2H), 7.08−7.05 (m, 4H), 6.88−6.81 (m, 3H), 4.27 (dt, 1JH−P = 9.5 Hz, 3 JH−P = 3JH−H = 6.9 Hz, 1H), 3.17−3.11 (m, 1H), 2.88−2.81 (m, 1H), 1.60 (bs, 1H). 13C{1H} NMR (CDCl3): δ 134.5, 134.3, 134.2, 133.9, 132.2 (d, JC−P = 2.0 Hz), 132.0 (d, JC−P = 8.0 Hz), 131.9 (d, JC−P = 2.0 Hz), 131.7 (d, JC−P = 9.0 Hz), 131.4 (d, JC−P = 2.0 Hz), 131.3 (d, JC−P = 8.0 Hz), 131.1 (d, JC−P = 2.0 Hz), 131.0 (d, JC−P = 9.0 Hz), 130.9 (d, JC−P = 10.0 Hz), 130.4 (d, JC−P = 10.0 Hz), 130.2 (d, JC−P = 7.0 Hz), 129.2 (d, JC−P = 11.0 Hz), 128.7 (d, JC−P = 11.0 Hz), 128.1 (d, JC−P = 5.0 Hz), 127.9 (d, JC−P = 5.0 Hz), 127.1 (d, JC−P = 2.0 Hz), 39.5 (d, JC−P = 69.0 Hz), 39.1 (d, JC−P = 69.0 Hz). 31P{1H} NMR (CDCl3): δ 36.6 (d, 3JP−P = 47.4 Hz), 31.0 (d, 3JP−P = 47.4 Hz). IR (cm−1): 3055.70 (w), 1591.87 (w), 1495.92 (w), 1436.95 (m), 1181.65 (m), 1155.10 (m), 1120.32 (m), 1103.84 (m), 1070.95 (w), 1046.77 (m), 1022.21 (w), 998.13 (w), 919.45 (w), 881.48 (w), 798.57 (w), 762.93 (w), 739.98 (s), 721.02 (s), 692.93 (s), 592.24 (w), 557.09 (w), 523.24 (w), 484.05 (w), 456.20 (w). HRMScalc for C32H30NO2P2 [M + H+]: 522.1752. HRMSmeas: 522.1758. 2s (method II*+, isolation B): red-orange solid, 93 mg (38%). Mp: 120−130 °C. 1H NMR (C6D6): 7.49−7.45 (m, 5H), 7.05−6.97 (m, 15H), 2.76 (d, 2JH−P = 15.0 Hz, 1H), 2.01−1.97 (m, 2H), 1.80−1.75 (m, 2H), 1.32 (bs, 1H), 0.91 (s, 3H). 13C{1H} NMR (C6D6): δ 149.0, 136.7 (d, JC−P = 9.0 Hz), 135.5, 134.9, 133.5, 132.8, 132.3 (d, JC−P = 3.0 Hz), 131.3 (d, JC−P = 9.0 Hz), 129.2 (d, JC−P = 11.0 Hz), 118.9 (d, JC−P = 15.0 Hz), 30.4 (d, JC−P = 51.0 Hz), 26.3 (d, JC−P = 70.0 Hz), 14.8, 13.0. 31P{1H} NMR (CDCl3): δ 34.6 (d, 3JP−P = 27.0 Hz), 27.4 (d, 3JP−P = 27.0 Hz). IR (cm−1): 2988.16 (w), 2880.30 (w), 2185.47 (w), 2175.78 (w), 1590.10 (w), 1486.90 (m), 1437.96 (m), 1310.73 (w), 1163.57 (s), 1127.77 (s), 1100.00 (s), 1070.08 (w), 1042.21 (s), 1021.98 (m), 1000.03 (m), 953.76 (w), 873.19 (w), 752.12 (m), 720.52 (s), 693.33 (s), 555.73 (m). HRMScalc for C28H29KNO3P2 [M +K+]: 528.1260. HRMSmeas: 528.1264. 2t (method II*+, isolation B): off-white solid, 100 mg (40%). Mp: 125−130 °C. 1H NMR (CDCl3): 7.90−7.69 (m, 7H), 7.62−7.59 (m, 2H), 7.53−7.39 (m, 8H), 7.23−7.20 (m, 3H), 2.80−2.62 (m, 2H), 3.68 (bs, 1H), 2.49−2.47 (m, 2H), 2.28 (s, 6H), 2.22 (d, 2JH−P = 15.0 Hz, 1H). 13C{1H} NMR (CDCl3): δ 132.3 (d, JC−P = 13.0 Hz), 132.0−131.5 (m), 130.8 (d, JC−P = 9.0 Hz), 129.1 (d, JC−P = 11.0 Hz), 128.9−128.7 (m), 128.5 (d, JC−P = 13.0 Hz), 50.3 (d, JC−P = 15.0 Hz), 29.9, 24.1, 10.3. 31P{1H} NMR (CDCl3): δ 34.8 (d, 3JP−P = 24.0 Hz), 26.3 (d, 3JP−P = 24.0 Hz). IR (cm−1): 2963.20 (w), 2880.40 (w), 1916.35 (w), 1590.12 (w), 1481.99 (w), 1435.74 (m), 1259.83 (m), 1172.91 (m), 1017.83 (s), 862.06 (w), 747.21 (s), 692.30 (s), 569.40 (w), 537.52 (w). HRMScalc for C29H32KN2O2P2 [M + K+]: 541.1576 HRMSmeas: 541.1580.

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ACKNOWLEDGMENTS

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REFERENCES

Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for support of this research, as well as the staff of the Ohio Crystallography Consortium housed at The University of Toledo for assistance with X-ray crystallography.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.6b00919. Spectroscopic data and crystal data including bond lengths and angles for compound 2f (PDF) Crystallographic data for compound 2f (CIF)

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*E-mail for J.A.R.S.: [email protected]. ORCID

Joseph A. R. Schmidt: 0000-0003-3019-0055 Notes

The authors declare no competing financial interest. H

DOI: 10.1021/acs.organomet.6b00919 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics (24) Alkyl nitriles were recrystallized from hot dichloromethane; solvent was trapped in the crystal lattice. (25) C6D6 was used instead of CDCl3 to avoid overlap with the diagnostic triplet in 13C{1H} NMR spectrum.

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DOI: 10.1021/acs.organomet.6b00919 Organometallics XXXX, XXX, XXX−XXX