The Chemistry of ortho-(Diarylphosphino)aryl Isocyanides

Dec 14, 2015 - The title phosphine-isocyanides were obtained by reaction of 2-lithioaryl isocyanides with diarylchlorophosphines. They cyclize to 1 ...
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The Chemistry of ortho-(Diarylphosphino)aryl Isocyanides Lujun Zhang,† Wenfei Yu,† Changchun Liu,† Youzhi Xu,† Zheng Duan,*,† and Francois Mathey*,†,‡ †

College of Chemistry and Molecular Engineering, International Phosphorus Laboratory, International Joint Research Laboratory for Functional Organophosphorus Materials of Henan Province, Zhengzhou University, Zhengzhou 450001, P. R. China ‡ Division of Chemistry & Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 S Supporting Information *

ABSTRACT: The title phosphine-isocyanides were obtained by reaction of 2-lithioaryl isocyanides with diarylchlorophosphines. They cyclize to 1,3-benzazaphospholes with cleavage of their two aryl−P bonds upon treatment with an excess of lithium in THF. Their PCH2 ylids spontaneously evolve to give λ5-1,4benzazaphosphinines. Their complexation by gold(I), palladium(II), and nickel(II) chlorides has been investigated. An original pincer diphosphine−carbene complex has been obtained with palladium. The new products have been characterized by X-ray crystal structure analysis.

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INTRODUCTION Even without taking into account their rich synthetic chemistry,1 the coordination chemistry of isocyanides is a wide domain whose versatility can be easily explained by the fact that these ligands are isoelectronic with carbon monoxide and can be considered as tunable CO’s.2 It is thus quite surprising that even a simple chelating ligand associating phosphine and isocyanide donors like 1a remains presently unknown even though some phosphine-isocyanide ligands have been synthesized in the coordination sphere of transition metals.3 This report is intended to fill this gap.

unexceptional and does not deserve special comments. The HOMO and the LUMO (Kohn−Sham) are shown in Figure 1.

Figure 1. HOMO (left) and LUMO (right) (Kohn−Sham) of phosphine-isocyanide 1a.

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The HOMO includes the lone pair at P and shows no localization on the isocyanide group. The LUMO includes a π* orbital of the NC triple bond and shows no localization at P. We can expect that nucleophiles will react primarily at the isocyanide group and electrophiles at phosphorus. Very recently, we developed a new method to synthesize phospholides by reaction of open-chain acetylenic phosphines with lithium (eq 2).6

RESULTS AND DISCUSSION The title compound and some analogues were easily synthesized using the recently described4 2-lithioaryl isocyanides as shown in eq 1.

The isocyanide functionality induces a shielding of the 31P resonance which is found at −11.8 (1a), −13.2 (1b), and −13.5 ppm (1c) in CDCl3 vs −6 ppm for triphenylphosphine. The 13C resonances of the isocyanide are found between 167.35 and 168.12 ppm. Phosphines 1 display two reactive centers. In order to have some insight on their relative reactivity, we decided to compute the electronic structure of 1a by DFT at the B3LYP/6311+G(d, p) level.5 The computed molecular structure of 1a is © XXXX American Chemical Society

This led us to investigate the reaction of lithium with our new phosphine-isocyanides 1. We were not very optimistic on the issue of these attempts because the LUMO of 1 is not localized at Received: September 1, 2015

A

DOI: 10.1021/acs.organomet.5b00746 Organometallics XXXX, XXX, XXX−XXX

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Organometallics P. Hence, injecting an electron into the LUMO was not supposed to induce a breaking of the P−Ph bonds. Nevertheless, unexpectedly, the azaphospholides 3 were formed (eq 3). Quenching the reaction mixture with water led, inter alia, to 1H2-phenyl-1,3-benzazaphosphole 4a, whose structure was confirmed by comparison with the numerous data reported in the literature.7

The resulting phosphide anion 8 displays the frontier orbitals shown in Figure 3.

Figure 3. HOMO (left) and LUMO (right) (Kohn−Sham) of the phosphide 8.

The HOMO includes the p lone pair of the phosphide, whereas the LUMO contains one of the π* orbitals of the isocyanide. Cyclization by nucleophilic attack of the anionic P at the NC triple bond is thus expected, but we do not know the precise mechanism of the azaphosphole formation. Anyhow, numerous similar cyclizations involving related 2-hydroxy- and 2amino-aryl-isocyanides have been described in the literature.8 Phosphines 1 can also serve to prepare the six-membered benzazaphosphinines, as shown in eq 5.

Similar results were obtained with 1b and 1c. Treating 3 with benzyl bromide or methyl iodide and sulfur gave 3H-2-phenyl1,3-benzazaphosphole sulfides 5 and 6, respectively. The structure of 5b was confirmed by X-ray crystal structure analysis (Figure 2).

The 1H NMR spectra of azaphosphinines 9 are characterized by an ABX system corresponding to the P-CHCH-N units: 9a: δA 4.84 (dd, JHP = 9.9, JHH = 13.2 Hz, PCH), δB 7.46 (ddd, JHP = 7.8, JHH = 13.2 Hz, NCH); 9b: δA 4.80 (dd, JHP = 9.6, JHH = 13.2 Hz, PCH), δB 7.34 (dd, JHP = 8.1, JHH = 13.2 Hz, NCH). The PCH carbons display characteristic shielding due to the high polarization of the CC double bond and strong 1JCP couplings: 9a: 66.51 (95.8 Hz); 9b: 66.54 (96.6 Hz). Only very few reports on 1,4-benzazaphosphinines are available in the literature.9 Unfortunately, 9a and 9b were obtained as yellow oils and we were unable to get crystals for X-ray analysis. The mechanism possibly involves the stepwise formation of a four-membered ring via a formal [2 + 2] cycloaddition between the ylidic PC double bond and the isocyanide, followed by a cycloreversion, giving the phosphinine ring (eq 6).

Figure 2. ORTEP drawing of azaphosphole sulfide 5b (30% thermal ellipsoids). Main distances (Å) and angles (deg): P1−S1 1.9403(9), P1−C7 1.857(2), P1−C9 1.792(3), P1−C15 1.830(3), C8−C9 1.388(3), C8−N1 1.432(3), N1−C7 1.281(3); C7−P1−C9 88.99(12), P1−C7−N1 112.91(19), C9−C8−N1 117.1(2).

In order to understand this unexpected success, we computed the structure of the radical anion 7 derived from 1a. Quite logically, the spin density was found mainly on the carbon of the isocyanide group (30%), but the lone electron appears to be delocalized all over the NC-CC-P unit and 10% of the spin density is found at P, thus explaining the evolution of the radical that reaches stability by expulsion of a phenyl radical (eq 4). The coordination chemistry of 1 is, of course, the main focus of this work. The reaction of 1 with a gold chloride complex expectedly affords bis-complexes 10 in which both functionalities are coordinated (eq 7). B

DOI: 10.1021/acs.organomet.5b00746 Organometallics XXXX, XXX, XXX−XXX

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Organometallics

The formula of 11 was established by X-ray crystal structure analysis (Figure 5). The mechanism of this reaction very probably involves the hydrolysis of the isocyanide units (NC → NHCHO). Then, a gold-catalyzed decarbonylation of the formamide11 or a further metal-assisted hydrolysis of the formamide with formation of formic acid can complete the process. The [Au2]2+ unit displays a rather short Au−Au interaction at 3.0007(6) Å. The course of the reaction with palladium chloride is quite different (eq 9). Both complexes have been characterized by X-ray crystal structure analysis. The data for 10a are presented in Figure 4.

The product is a cationic carbene complex 12 that has been characterized by X-ray crystal structure analysis (Figure 6).

Figure 4. ORTEP drawing of AuCl complex 10a (50% thermal ellipsoids). Main distances (Å): Au1−P1 2.233(2), Au1−Cl1 2.284(3), Au2−C19 1.939(13), Au2−Cl2 2.243(3), Au1−Au2 3.4592(10), N1− C19 1.126(14).

Figure 6. ORTEP drawing of the carbenic palladium complex 12 (30% thermal ellipsoids). Main distances (Å) and angles (deg): C19−Pd1 2.003(5), P1−Pd1 2.2821(11), P2−Pd1 2.3188(11), Cl1−Pd1 2.3187(13), C19−N1 1.330(6), C19−N2 1.329(6); C19−Pd1−Cl1 176.80(14), P1−Pd1−P2 166.81(5), C19−Pd1−P1 84.13(13), C19− Pd1−P2 82.73(13), N1−C19−N2 114.6(4).

The complex shows a dimeric structure held by two gold−gold interactions with a gold−gold distance of 3.4592(10) Å. Typical aurophilic interactions are found between 2.7 and 3.3 Å,10 and thus, the interactions found in 10a are especially weak. In 10b, this interaction is shorter at 3.2106(6) Å. Upon abstraction of the chloride ions by silver triflate, these complexes evolve by losing their two isocyanide carbons and two gold units (eq 8).

The palladium center displays a slightly distorted square planar geometry with a Pd−carbene bond length of 2.003(5) Å, somewhat shorter than in a well-known palladium−carbene catalyst.12 The mechanism of the formation of 12 has not been established, but we propose the following scheme based on a well-documented chemistry (eq 10).13

Figure 5. ORTEP drawing of dicationic Au2 complex 11 (30% thermal ellipsoids). Main distances (Å) and angles (deg): Au1−Au1A 3.0007(6), Au1− N1A 2.130(6), Au1−P1 2.2427(17), C18−N1 1.433(9), C18−C13 1.387(11), C13−P1 1.833(7); C13−P1−Au1 114.0(2). C

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separations. 2a and 2b were prepared according to literature methods.4 Commercially available reagents were used without further purification. Synthesis of Phosphines 1. To a solution of 2 (12.6 mmol) in anhydrous THF (60 mL), kept in an oven-dried 100 mL Schlenk flask under an atmosphere of dry nitrogen, was added dropwise a 1.6 M solution of n-BuLi in hexane (8.0 mL, 12.8 mmol) at−78 °C over a period of 5 min. After the mixture was stirred at −78 °C for 1 h, Ar2PCl (12.6 mmol) in anhydrous THF (10 mL) was added dropwise. The mixture was kept at −78 °C for 1 h and then warmed to room temperature. After 3 h, the reaction was completed. The mixture was diluted with diethyl ether, and the organic phase was washed with water and brine and dried over anhydrous Na2SO4. The solvents were removed under reduced pressure to give a crude product, which was purified by recrystallization (dichloromethane and hexane) at about 10 °C to give a yellow solid. 1a: mp 125−126 °C, 2361 mg, 65% yield. 31P NMR (121 MHz, CDCl3): δ −11.8 ppm; 1H NMR (300 MHz, CDCl3): δ 6.88−6.92 (m, 1 H), 7. 30−7. 42 (m, 13 H) ; 13C NMR (101 MHz, CDCl3): δ 127.30 (d, JCP = 2.0 Hz, CH), 128.85 (d, JCP = 8.0 Hz, 4CH), 129.28 (s, CH), 129.45 (s, 2CH), 129.49 (s, CH), 133.41 (s, CH), 134.18 (d, JCP = 21.1 Hz, 4CH), 134.30 (d, JCP = 10.1 Hz, 2C), 135.66 (d, JCP = 19.1 Hz, C), 168.12 (s, C, NC) ppm. One carbon is missing due to an overlap. HRMS calcd for C19H15NP [M + H]+: 288.0937; found:288.0934. 1b: mp 125−126 °C, 2361 mg, 60% yield. 31P NMR (121 MHz, CDCl3): δ −13.2 ppm; 1H NMR (300 MHz, CDCl3): δ 2.37 (s, 3H), 6.79 (dd, J = 3.3, 7.8 Hz, 1H), 7.12 (d, J = 8.1 Hz, 1H), 7.25(br s, 1H), 7.30−7.41(m, 10H); 13C NMR (75 MHz, CDCl3): δ 20.94 (s, CH3), 127.85 (d, JCP = 2.0 Hz, CH), 128.76 (d, JCP = 7.5 Hz, 4CH), 129.31 (s, 2CH), 130.27 (s, CH), 131.87 (d, JCP = 18.1 Hz, C), 133.42 (s, CH), 134.05 (d, JCP = 20.4 Hz, 4CH), 134.65 (d, JCP = 9.8 Hz, 2C), 140.14 (s, C), 167.35 (s, C, NC) ppm. One carbon is missing due to an overlap. HRMS calcd for C20H17NP [M + H]+: 302.1093; found: 302.1099. 1c: mp 98−100 °C, 3148 mg, 79% yield. 31P NMR (121 MHz, CDCl3): δ −13.5 ppm; 1H NMR (300 MHz, CDCl3): δ 2.39 (s, 6H), 6.89−6.93 (m, 1H), 7.19−7.41 (m, 11H); 13C NMR (75 MHz, CDCl3): δ 21.42 (s, 2CH3), 127.20 (d, JCP = 1.5 Hz, CH), 129.16 (s, CH), 129.21 (s, CH), 129.65 (d, JCP = 8.3 Hz, 4CH), 130.86 (d, JCP = 9.0 Hz, 2C), 133.23 (s, CH), 134.26 (d, JCP = 20.2 Hz, 4CH), 136.34 (d, JCP = 20.2 Hz, C), 139.45 (s, 2C), 168.01 (s, C, NC). One carbon is missing due to an overlap. HRMS calcd for C21H19NP [M + H]+: 316.1250; found: 316.1257. Synthesis of Benzazaphospholes 4 and Derivatives 5 and 6. To a solution of 1 (1 mmol) in THF (10 mL) was added 5 equiv of lithium wire under a N2 atmosphere. The reaction mixture was stirred for 1 h at room temperature, and the 31P NMR signal indicated that the reaction was complete. Then, the excess of lithium wire was removed. Water, benzyl bromide, or iodomethane (2 mmol) was added at room temperature. (1) For the reaction with water, the solvent was removed under reduced pressure after 10 min. Dichloromethane (20 mL) was added and dried over anhydrous Na2SO4. After stirring for 30 min, the reaction mixture was filtrated under a N2 atmosphere and evaporated again under reduced pressure. The products (4a, 4b, 4c) were got as yellow solids. (2) For the reaction with benzyl bromide or iodomethane, the reaction mixture was stirred for 3 h and 31P NMR indicated that the reaction was complete. Then, S8 was added, and the reaction mixture was stirred for another 3 h at 50 °C. After removal of the solvent under reduced pressure, the residue was treated with water (10 mL) and extracted with dichloromethane. The organic layer was dried over anhydrous Na2SO4. After filtration and removal of the solvent, the residue was chromatographed on silica gel (petroleum ether/ethyl acetate = 15/1). 4a2: 201 mg, 95% yield, purity > 95%. 31P NMR (121 MHz, CDCl3): δ 75.6 ppm; 1H NMR (300 MHz, CDCl3): δ 7.16−7.22 (m, 1H), 7.34− 7.48 (m, 4H), 7.60−7.63 (d, J = 8.4 Hz, 1H), 7.79−7.83 (m, 2H), 8.09 (dq, J = 3.6, 7.8 Hz, 1H), 9.56 (br s, 1H, NH); 13C NMR (75 MHz, CDCl3): δ 113.58 (s, CH), 120.54 (d, JCP = 12.1 Hz, CH), 125.28 (d, JCP = 2.3 Hz, 2CH), 125.43 (s, CH), 128.86 (d, JCP = 21.1 Hz, CH), 128.93 (d, JCP = 3.0 Hz, CH), 129.19 (s, 2CH), 134.96 (d, JCP = 15.8 Hz, C), 141.56 (d, JCP = 41.3 Hz, C), 142.88 (d, JCP = 9.1 Hz, C), 174.45 (d, JCP =

A variant of this mechanism could involve a coordination of the isocyanide to palladium prior to cyclization. The course of the reaction with nickel chloride is again entirely different. The sole isolated product was a head-to-tail organic dimer 13, unfortunately obtained in low yield (14%) (eq 11).

The formula of 13 was established by X-ray crystal structure analysis (Figure 7).

Figure 7. ORTEP drawing of the head-to-tail dimer 13 (30% thermal ellipsoids). Main distances (Å) and angles (deg): P1−C13 1.775(4), P1−C20 1.794(4), C13−C18 1.396(5), C18−N1 1.376(5), N1−C19 1.377(5), C19−C20 1.372(5); C13−P1−C20 103.35(17), P1−C20− C19 118.3(3), C19−C20−N2 126.1(3), P1−C20−N2 115.6(2), C19− N1−C18 125.5(3).

The two central carbons appear as a doublet of doublet at 95.55 ppm in MeOD (1JCP = 100.5, 2JCP = 6.8 Hz). This product has never been described in the literature. The mechanism of its formation is not clear. From all of the preceding experiments, it appears that the chemistry of 1 is diverse and unpredictable. It certainly deserves further investigation.

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EXPERIMENTAL SECTION

All reactions were performed under nitrogen using solvents dried by standard methods. 1H, 13C, and 31P NMR spectra were recorded on Bruker 300 and 400 MHz spectrometers. Chemical shifts are expressed in ppm from internal TMS (1H and 13C). All coupling constants (J values) are reported in hertz (Hz). HRMS spectra were obtained on a Water Q-Tof Premier MS. Element analytic data were obtained on a Thermo Electron Corporation flash EA 1112 element spectrometer. Melting point: heating rate, 4 °C/min; the thermometer was not corrected. Silica gel (230−400 mesh) was used for the chromatographic D

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Organometallics 44.5 Hz, C). HRMS calcd for C13H11NP [M + H]+: 212.0624; found: 212.0622. 4b: 221 mg, 98% yield, purity > 95%. 31P NMR (121 MHz, CDCl3): δ 74.9 ppm; 1H NMR (300 MHz, CDCl3): δ 2.50 (s, 3H, CH3), 7.02 (d, J = 8.1 Hz, 1H), 7.36−7.48 (m, 4H), 7.79 (d, J = 7.5 Hz, 2H), 7.95 (dq, J = 3.6, 8.1 Hz, 1H), 9.33 (br s, 1H, NH); 13C NMR (75 MHz, CDCl3): δ 21.73 (s, CH3), 113.41 (s, CH), 122.61 (d, JCP = 12.1 Hz, CH), 125.17 (d, JCP = 12.8 Hz, 2CH), 128.48 (d, JCP = 21.1 Hz, CH), 128.75 (d, JCP = 3.0 Hz, CH), 129.17 (s, 2CH), 135.10 (d, JCP = 15.1 Hz, C), 135.54 (d, JCP = 3.0 Hz, C), 138.22 (d, JCP = 40.0 Hz, C), 143.43 (d, JCP = 6.8 Hz, C), 173.81 (d, JCP = 49.8 Hz, C). HRMS calcd for C14H13NP [M + H]+: 226.0780; found: 226.0778. 4c: 176 mg, 78% yield, purity > 95%. 31P NMR (121 MHz, CDCl3): δ 73.4 ppm; 1H NMR (300 MHz, CDCl3): δ 2.37 (s, 3H, CH3), 7.11−7.23 (m, 3H), 7.28−7.34 (m, 1H), 7.54−7.57 (m, 1H), 7.64−7.67 (dd, J = 1.8, 8.1 Hz, 2H), 8.03 (dq, J = 3.6, 7.8 Hz, 1H), 9.41 (br s, 1H, NH); 13C NMR (75 MHz, CDCl3): δ 21.32 (s, CH3), 113.48 (s, CH), 120.50 (d, JCP = 11.3 Hz, CH), 125.10 (d, JCP = 3.0 Hz, CH), 125.20 (d, JCP = 12.1 Hz, 2CH), 128.80 (d, JCP = 21.1 Hz, CH), 129.86 (s, 2CH), 132.22 (d, JCP = 15.8 Hz, C), 139.10 (d, JCP = 3.0 Hz, C), 141.54 (d, JCP = 41.5 Hz, C), 142.82 (d, JCP = 6.8 Hz, C), 174.81 (d, JCP = 50.6 Hz, C). HRMS calcd for C14H13NP [M + H]+: 226.0780; found: 226.0778. 5a: mp 131−133 °C, yellow solid, 200 mg, 60% yield. 31P NMR (121 MHz, CDCl3): δ 49.5 ppm; 1H NMR (300 MHz, CDCl3): δ 3.53−3.76 (m, 2H), 6.80 (dd, J = 1.8, 7.2 Hz, 2H), 7.09 (t, J = 7.8 Hz, 2H), 7.14− 7.19 (m, 1H), 7.38−7.43 (m, 1H), 7.48−7.61 (m, 6H), 8.43 (dq, J = 0.6, 7.2 Hz, 2H); 13C NMR (75 MHz, CDCl3): δ 42.58 (d, JCP = 39.2 Hz, CH2), 124.70 (d, JCP = 5.0 Hz, CH), 126.02 (s, C), 127.66 (d, JCP = 4.0 Hz, CH), 128.23 (d, JCP = 3.5 Hz, 2CH), 128.61 (s, CH), 128.74 (s, CH), 128.89 (d, JCP = 3.4 Hz, 2CH), 129.15 (s, 2CH), 129.44 (d, JCP = 9.0 Hz, C), 129.77 (d, JCP = 5.5 Hz, 2CH), 132.54 (s, CH), 133.08 (d, JCP = 26.2 Hz, C), 133.97 (d, JCP = 2.0 Hz, CH), 153.41 (d, JCP = 31.7 Hz, C), 170.08 (d, JCP = 42.3 Hz, C). HRMS calcd for C20H17NPS [M + H]+: 334.0814; found: 334.0817. Anal. Calcd for C20H16NPS: C 72.05, H 4.84, N 4.20, S 9.62; found: C. 71.85, H 4.82, N 4.08, S 9.45. 5b: mp 127−129 °C, yellow solid, 288 mg, 83% yield. 31P NMR (121 MHz, CDCl3): δ 49.0 ppm; 1H NMR (300 MHz, CDCl3): δ 2.43 (s, 3H, CH3), 3.50−3.75 (m, 2H, CH2), 6.81−6.83 (m, 2H), 7.07−7.24 (m, 4H), 7.34−7.59 (m, 5H), 8.44 (d, J = 6.9 Hz, 2H); 13C NMR (75 MHz, CDCl3): δ 21.93 (s, CH3), 42.70 (d, JCP = 40.0 Hz, CH2), 122.07 (d, JCP = 99.6 Hz, C), 125.47 (d, JCP = 5.3 Hz, CH), 127.60 (d, JCP = 3.8 Hz, CH), 128.21 (d, JCP = 3.8 Hz, 2CH), 128.59 (d, JCP = 12.1 Hz, CH), 128.83 (d, JCP = 3.0 Hz, 2CH), 129.09 (s, 2CH), 129.40 (d, JCP = 10.6 Hz, CH), 129.61 (d, JCP = 9.1 Hz, C), 129.78 (d, JCP = 5.3 Hz, 2CH), 132.40 (s, CH), 133.18 (d, JCP = 25.7 Hz, C), 144.89 (d, JCP = 2.1 Hz, C), 153.82 (d, JCP = 32.5 Hz, C), 170.41 (d, JCP = 42.3 Hz, C). HRMS calcd for C21H19NPS [M + H]+: 348.0970; found: 348.0978. Anal. Calcd for C21H18NPS: C 72.60, H 5.22, N 4.03, S 9.23; found: C 72.49, H 5.17, N 4.05, S 9.09. 5c: mp 120−122 °C, yellow solid, 261 mg, 75% yield. 31P NMR (121 MHz, CDCl3): δ 49.6 ppm; 1H NMR (300 MHz, CDCl3): δ 2.47 (s, 3H, CH3), 3.51−3.74 (m, 2H, CH2), 6.77−6.81 (m, 2H), 7.06−7.19 (m, 3H), 7.32−7.40 (m, 3H), 7.48 (t, J = 7.8 Hz, 1H), 7.53−7.60 (m, 2H), 8.32 (d, J = 8.1 Hz, 2H); 13C NMR (75 MHz, CDCl3): δ 21.85 (s, CH3), 42.74 (d, JCP = 39.2 Hz, CH2), 124.41 (d, JCP = 5.1 Hz, CH), 125.19 (d, JCP = 97.1 Hz, C), 127.57 (d, JCP = 4.1 Hz, CH), 128.15 (d, JCP = 3.5 Hz, 2CH), 128.31 (d, JCP = 10.3 Hz, CH), 128.66 (s, CH), 128.85 (d, JCP = 3.8 Hz, 2CH), 129.52 (d, JCP = 9.0 Hz, C), 129.70 (d, JCP = 5.5 Hz, 2CH), 129.86 (s, 2CH), 130.41 (d, JCP = 26.4 Hz, C), 133.83 (d, JCP = 2.3 Hz, CH), 143.32 (s, C), 153.61 (d, JCP = 32.5 Hz, C), 170.00 (d, JCP = 41.5 Hz, C). HRMS calcd for C21H19NPS [M + H]+: 348.0970; found: 348.0977. Anal. Calcd for C21H18NPS: C, 72.60; H, 5.22; N, 4.03; S, 9.23. found: C, 72.85; H, 5.32; N, 3.93; S, 8.85. 6a: mp 108−110 °C, yellow solid, 85 mg, 33% yield. 31P NMR (121 MHz, CDCl3): δ 42.7 ppm; 1H NMR (300 MHz, CDCl3): δ 2.06 (d, JHP = 13.2 Hz, 3H, CH3), 7.43−7.50 (m, 1H), 7.52−7.59 (m, 3H), 7.61− 7.67 (m, 1H), 7.75−7.83 (m, 2H), 8.45−8.48 (m, 2H); 13C NMR (75 MHz, CDCl3): δ 21.33 (d, JCP = 48.3 Hz, CH3), 124.90 (d, JCP = 5.1 Hz, CH), 127.46 (d, JCP = 98.1 Hz, C), 127.77 (d, JCP = 12.8 Hz, CH), 128.78 (d, JCP = 3.8 Hz, 2CH), 129.04 (d, JCP = 10.5 Hz, CH), 129.16 (s,

2CH), 132.27 (d, JCP = 27.2 Hz, C), 132.55 (s, CH), 133.85 (d, JCP = 2.0 Hz, CH), 152.90 (d, JCP = 34.0 Hz, C), 171.11 (d, JCP = 45.3 Hz, C). HRMS calcd for C14H13NPS [M + H]+: 258.0501; found: 258.0508. Anal. Calcd for C14H12NPS: C, 65.35; H, 4.70; N, 5.44; S, 12.46. found: C, 65.22; H, 4.79; N, 5.34; S, 12.57. 6b: mp 123−125 °C, yellow solid, 122 mg, 45% yield. 31P NMR (121 MHz, CDCl3): δ 42.2 ppm; 1H NMR (300 MHz, CDCl3): δ 2.03 (d, JHP = 13.2 Hz, 3H, CH3), 2.48 (s, 3H, CH3), 7.26−7.29 (m, 1H), 7.53−7.59 (m, 4H), 7.67 (t, J = 8.1 Hz, 1H), 8.44−8.47 (m, 2H); 13C NMR (75 MHz, CDCl3): δ 21.52 (d, JCP = 48.3 Hz, CH3), 21.87 (s, CH3), 124.15 (d, JCP = 100.4 Hz, C), 125.65 (d, JCP = 5.3 Hz, CH), 127.55 (d, JCP = 13.6 Hz, CH), 128.74 (d, JCP = 3.8 Hz, 2CH), 129.12 (s, 2CH), 129.66 (d, JCP = 10.6 Hz, CH), 132.36 (d, JCP = 27.2 Hz, C), 132.44 (s, CH), 144.91 (d, JCP = 3.0 Hz, C), 153.30 (d, JCP = 34.0 Hz, C), 171.38 (d, JCP = 47.5 Hz, C). HRMS calcd for C15H15NPS [M + H]+: 272.0657; found: 272.0665. Anal. Calcd for C15H14NPS: C, 66.40; H, 5.20; N, 5.16; S, 11.82. found: C, 66.21; H, 5.31; N, 5.04; S, 11.66. 6c: mp 101−102 °C, yellow solid, 100 mg, 37% yield. 31P NMR (121 MHz, CDCl3): δ 42.5 ppm; 1H NMR (300 MHz, CDCl3): δ 2.04 (d, JHP = 8.4 Hz, 3H), 2.45 (s, 3H), 7.35 (d, J = 8.4 Hz, 2H), 7.44 (ddd, J = 0.9, 3.9, 7.5 Hz, 1H), 7.59−7.65 (m, 1H), 7.72−7.81 (m, 2H), 8.35 (d, J = 8.4 Hz, 2H; 13C NMR (75 MHz, CDCl3): δ 21.42 (d, JCP = 47.9 Hz, CH3), 21.86 (s, CH3), 124.69 (d, JCP = 5.1 Hz, CH), 127.32 (d, JCP = 98.4 Hz, C), 127.73 (d, JCP = 12.8 Hz, CH), 128.73 (d, JCP = 9.8 Hz, CH), 128.80 (d, JCP = 3.8 Hz, 2CH), 129.62 (d, JCP = 26.9 Hz, C), 129.95 (s, 2CH), 133.89 (d, JCP = 2.1 Hz, CH), 143.47 (s, C), 153.06 (d, JCP = 33.2 Hz, C), 170.99 (d, JCP = 45.3 Hz, C). HRMS calcd for C15H15NPS [M + H]+: 272.0657; found: 272.0664. Anal. Calcd for C15H14NPS: C, 66.40; H, 5.20; N, 5.16; S, 11.82. found: C, 66.19; H, 5.18; N, 5.04; S, 11.86. Synthesis of Benzazaphosphinines 9. To a solution of 1 (1 mmol) in anhydrous dichloromethane (10 mL) was added MeOTf (1.1 mmol) under a N2 atmosphere. The reaction mixture was stirred for 1 h at room temperature, and the 31P NMR spectrum indicated that the reaction was complete. Then, t-BuOK (2 mmol) was added. The 31P NMR spectrum showed that the reaction was complete after another 1 h. Then, TFA (2.1 mmol) was added. After filtration, the solvent was removed under reduced pressure. The crude product was purified by column chromatography on silica gel (CH2Cl2/CH3OH 10:1). 9a: yellow oil, 239 mg, 53% yield. 31P NMR (121 MHz, CDCl3): δ −3.8 ppm; 19F NMR (CDCl3): δ −79.0 ppm; 1H NMR (300 MHz, CDCl3): δ 4.84 (dd, J = 9.9, 13.2 Hz, 1H), 7.21−7.27 (m, 1H), 7.46 (ddd, J = 1.5, 7.8, 13.2 Hz, 1H), 7.52−7.63 (m, 9H), 7.65−7.72 (m, 2H), 7.80−7.85 (m, 1H), 7.99 (ddd, J = 4.8, 9.6, 31.5 Hz, 1H), 12.94 (br s, 1H, NH); 13C NMR (75 MHz, CDCl3): δ 66.51 (d, JCP = 95.8 Hz, CH), 97.31 (d, JCP = 90.6 Hz, C), 120.49 (d, JCP = 6.0 Hz, CH), 124.78 (d, JCP = 11.8 Hz, CH), 125.39 (d, JCP = 94.5 Hz, 2C), 129.92 (d, JCP = 12.8 Hz, 4CH), 131.00 (d, JCP = 6.8 Hz, CH), 132.56 (d, JCP = 12.1 Hz, 4CH), 134.09 (d, JCP = 3.0 Hz, 2CH), 134.74 (d, JCP = 1.5 Hz, CH), 142.50 (d, JCP = 3.0 Hz, C), 145.99 (d, JCP = 2.3 Hz, CH). HRMS calcd for C20H17NP [M − OTf]+: 302.1093; found: 302.1094. 9b: yellow oil, 405 mg, 87% yield. 31P NMR (121 MHz, CDCl3): δ −4.1 ppm; 19F NMR (CDCl3): δ −78.2 ppm; 1H NMR (300 MHz, CDCl3): δ 2.33 (s, 3H, CH3), 4.80 (dd, J = 9.6, 13.2 Hz, 1H), 7.05 (d, J = 8.1 Hz, 1H), 7.34 (dd, J = 8.1, 13.2 Hz, 1H), 7.49−7.66 (m, 11 H), 7.94 (ddd, J = 6.6, 16.5, 31.5 Hz, 1H), 12.72 (br s, 1H, NH); 13C NMR (75 MHz, CDCl3): δ 21.69 (s, CH3), 66.54 (d, JCP = 96.6 Hz, CH), 94.34 (d, JCP = 92.8 Hz, C), 119.99 (d, JCP = 6.8 Hz, CH), 125.59 (d, JCP = 94.3 Hz, 2C), 126.46 (d, JCP = 12.1 Hz, CH), 129.84 (d, JCP = 13.6 Hz, 4CH), 130.88 (d, JCP = 6.8 Hz, CH), 132.45 (d, JCP = 11.3 Hz, 4CH), 133.96 (d, JCP = 3.0 Hz, 2CH), 142.49 (d, JCP = 3.8 Hz, C), 145.93 (d, JCP = 2.3 Hz, CH), 146.17 (d, JCP = 1.5 Hz, C). HRMS calcd for C21H19NP [M − OTf]+: 316.1250; found: 316.1253. Synthesis of Gold Complexes 10. Gold chloride complex (600 mg, 1.87 mmol), kept in an oven-dried 50 mL Schlenk flask under an atmosphere of dry nitrogen, was added to a solution of 1a (253 mg, 0.89 mmol) in anhydrous dichloromethane (20 mL). The reaction was complete after 24 h at room temperature. The solvent was removed under reduced pressure, and the residue was washed with hexane and a mixture of dichloromethane and hexane, to give 10a as a white solid (563 mg, 85% yield). E

DOI: 10.1021/acs.organomet.5b00746 Organometallics XXXX, XXX, XXX−XXX

Organometallics

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10a: decomp. 175 °C. 31P NMR (121 MHz, CDCl3): δ 27.8 ppm; 1H NMR (300 MHz, CDCl3): δ 7.10−7.17 (m, 1H), 7.59−7.73 (m, 13H). Anal. Calcd for C19H14Au2 Cl2NP: C 30.34, H 1.88, N 1.86; found: C. 29.75; H. 1.81; N. 1.87. 10b (colorless solid, 398 mg, 52% yield) was obtained from 1b (303 mg, 1 mmol) following the same protocol as that for 10a. 10b: decomp. 180 °C. 31P NMR (121 MHz, CDCl3): δ 27.8 ppm; 1H NMR (300 MHz, CDCl3): δ 2.50(s, 6H, CH3), 7.03 (dd, J = 8.1, 12 Hz, 2H), 7.41 (d, J = 8.1 Hz, 2H), 7.55−7.70 (m, 22H) . Anal. Calcd for C40H32Au4Cl4N2P2: C 31.35, H 2.10, N 1.83; found: C. 30.76; H. 2.03; N. 1.53. Synthesis of Gold Complex 11. AgOTf (93 mg, 0.36 mmol) was added to a solution of 10a (135 mg, 0.18 mmol) in anhydrous dichloromethane (6 mL), kept in an oven-dried 10 mL Schlenk flask under an atmosphere of dry nitrogen. After 12 h, 5 equiv of water was added. The reaction was complete after 12 h at room temperature. After filtration, the solvent was removed under reduced pressure and the residue was washed with hexane and a mixture of dichloromethane and hexane, to give a colorless solid 11 (70 mg, 63% yield). 11: decomp. 173 °C. 31P NMR (121 MHz, CDCl3): δ 19.3 ppm; 19F NMR (CDCl3) δ −78.6 ppm; 1H NMR (300 MHz, CDCl3): δ 6.69− 6.87 (m, 6H), 7.27−7.32 (m, 2H), 7.64−7.71 (m, 22H), 7.87−7.91 (m, 2H). Anal. Calcd for C38H32Au2F6N2O6P2S2: C 36.61, H 2.59, N 2.25, S 5.14; found: C. 36.89, H. 2.84, N. 2.25, S.4.94. Synthesis of Palladium Complex 12. PdCl2 (172 mg, 0.97 mmol) was added to a solution of 1a (278 mg, 0.97 mmol) in anhydrous dichloromethane (10 mL), kept in an oven-dried 50 mL Schlenk flask under an atmosphere of dry nitrogen. The 31P NMR spectrum of the solution indicated that the reaction was complete after 24 h at r.t. After filtration, the solvent was removed under reduced pressure and the residue was washed with hexane and a mixture of dichloromethane and hexane, to give a yellow solid (mp 203−205 °C, 275 mg, 76%). 12: 31P NMR (121 MHz, CDCl3): δ 14.1 ppm; 1H NMR (300 MHz, CDCl3): δ 7.05−7.10 (m, 2H), 7.21−7.27 (m, 3H), 7.39−7.45 (m, 15H), 7.51−7.56 (m, 8H), 12.64 (br s, 2H, NH); 13C NMR (101 MHz, CDCl3): δ 114.39 (dd, JCP = 24 Hz, 2C), 123.51 (dd, JCP = 2.2 Hz, 2CH), 125.40 (dd, JCP = 27, 8.0 Hz, 4C), 126.01 (dd, JCP = 3.0 Hz, 2CH), 128.92 (dd, JCP = 5.6 Hz, 8CH), 132.02 (s, 4CH), 133.02 (s, 2CH), 133.39 (s, 2CH), 134.42 (dd, JCP = 6.6 Hz, 8CH), 143.66 (dd, JCP = 7.5 Hz, 2C), 177.7 (dd, JCP = 7.5 Hz, C). Anal. Calcd for C37H30Cl2N2P2Pd: C 59.90, H 4.08, N 3.78; found: C. 59.63; H. 4.15; N. 3.53. Reaction of Phosphine 1a with Nickel Chloride. To a solution of 1a (288 mg, 1 mmol) in THF (10 mL) was added NiCl2 (130 mg, 1 mmol) under a N2 atmosphere. The reaction mixture was stirred for 24 h at r.t., and the 31P NMR signal disappeared. After filtration, the residual solid was washed with THF to give a yellow solid 13 (45 mg, 14%). 13: mp > 240 °C. 31P NMR (121 MHz, MeOD): δ −2.2 ppm; 1H NMR (300 MHz, MeOD): δ 7.35−7.39 (t, J = 6.9 Hz, 2H), 7.52−7.61 (m, 4H), 7.74−7.83 (m, 10H), 7.91−7.98 (m, 12H); 13C NMR (75 MHz, MeOD): δ 95.55 (AA’X, JCP = 6.8, 100.5 Hz, 2C), 117.68 (AA’X, JCP = 4.5, 96.8 Hz, 2C), 118.04 (s, 2CH), 124.69 (dd, JCP = 6.8 Hz, 2CH), 130.54 (dd, JCP = 6.8 Hz, 8CH), 131.28 (dd, JCP = 4.5 Hz, 2CH), 134.19 (dd, JCP = 6.0 Hz, 8CH), 135.55 (s, 2CH), 135.82 (s, 4CH), 143.01 (dd, JCP = 6.8 Hz, 4C). One carbon is missing. HRMS calcd for C38H30N2P2 [M − 2Cl]2+: 288.0937; found: 288.0940.

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AUTHOR INFORMATION

Corresponding Authors

*(F.M.) E-mail: [email protected]. *(Z.D.) E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors thank the referees for some valuable suggestions. This work was supported by the National Natural Science Foundation (21272218), the Specialized Research Fund for the Doctoral Program of Higher Education (20134101110004), the Henan Science and Technology Department (144300510011), and the Zhengzhou Science and Technology Department (131PYSGZ204) of China.

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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.5b00746. NMR spectra of compounds 1, 3, 4, 5, 6, 9, 10, 11, 12, and 13 (PDF) X-ray crystal structure analysis of compound 5b (CIF) X-ray crystal structure analysis of compound 10a (CIF) X-ray crystal structure analysis of compound 11 (CIF) X-ray crystal structure analysis of compound 12 (CIF) X-ray crystal structure analysis of compound 13 (CIF) F

DOI: 10.1021/acs.organomet.5b00746 Organometallics XXXX, XXX, XXX−XXX