Article pubs.acs.org/IC
Potassium-Mediated Hydrophosphorylation of Heterocumulenes with Diarylphosphane Oxide and Sulfide Stephan M. Har̈ ling, Helmar Görls, Sven Krieck, and Matthias Westerhausen* Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Humboldtstrasse 8, D-07743 Jena, Germany S Supporting Information *
ABSTRACT: The preparation of the hydrophosphorylation catalysts succeeds via the metalation of dimesitylphosphane oxide and diphenylphosphane sulfide with potassium hydride in ethereal solvents such as tetrahydropyran (THP) and tetrahydrofuran (THF) yielding the tetramers [(thp)K(OPMes2)]4 (1a) and [(thf)3{K(OPMes2)}4] (1b) as well as [(thp)KSPPh2]∞ (2) with a strand-like structure in the crystalline state. In ethereal solution these complexes very slowly degrade into KPAr2 and KE2PAr2 (E = O, S). The catalytic conversion of iPr-NCE′ (E′ = O, S) and of RNCN-R (R = iPr, cHex) to the addition products Ar2P(E)-C(=E′)-NHR (Ar = Ph, Mes; E = O, S; E′ = O, S, NR) was studied in the presence of catalytic amounts of Ar2PEK (Ar = Ph, Mes; E = O, S). Steric hindrance prevents the addition of dimesitylphosphane oxide to N,N′diisopropylcarbodiimide, whereas diphenylphosphane oxide and sulfide smoothly add to iPr−NCN-iPr yielding Ph2P(E)C(N-iPr)-NHiPr (E = O, S).
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INTRODUCTION Hydroelementation (hydrofunctionalization, addition of H−E bonds to multiple bonds) represents an atom-economic reaction for the functionalization of unsaturated compounds.1 However, this reaction requires a catalyst to overcome the electrostatic repulsion between electron-rich π-systems and Lewis bases such as amines (hydroamination), phosphanes (hydrophosphination, hydrophosphanylation), or phosphane oxides (hydrophosphorylation). Furthermore, this reaction is entropically disfavored, and especially the hydroamination often succeeds only with activated alkenes via a catalytic intramolecular addition reaction. For the addition of H−N and H−P bonds across multiple bonds, diverse catalysts are suitable.1,2 The s-block metals are not commonly used for catalytic purposes; nevertheless, their importance is increasingly being recognized. Therefore, the catalytic activity of s-block metal complexes has been explored by several research groups quite recently.3−6 Especially calciumbased catalysts seem to be advantageous due to the global abundance and beneficial position in the Periodic Table between typical s-block metals and early transition metals, advantageously combining the beneficial properties of typical sblock metals (highly ionic bonds, strong nucleophilicity) and of the early transition metals (availability of d-orbitals,4 catalytic activity).5 These catalysts commonly are prepared via a metathetical approach from calcium halide and potassium complexes, yielding the calcium derivatives and insoluble potassium halide according to Scheme 1. This procedure requires an exact 2:1 stoichiometry of KR/CaI2 in order to © XXXX American Chemical Society
Scheme 1. Synthesis and Degradation of [(thf)4Ca(OPPh2)2]
avoid the presence of excess KR (leading to formation of potassium calciates with a different reactivity than the monometallic organometallics) or of halide yielding heteroleptic calcium complexes.7 Often recrystallization is necessary to isolate analytically pure calcium derivatives. The hydrophosphanylation and hydrophosphorylation can be mediated by the calcium catalyst [(thf)4Ca(PPh2)2].8,9 In the latter reaction, the catalytically active species [(thf)4Ca(OPPh2)2] is formed in an equilibrium with the starting phosphanide [(thf)4Ca(PPh2)2].10 Even though [(thf)4Ca(OPPh2)2] can be prepared in a straightforward metalation reaction,11 oxygen-transfer reactions occur in solution yielding calcium-bound Ph2P− and Ph2PO2− anions (Scheme 1). The calcium bis(diphenylphosphanides) were observed in the 31P NMR spectrum, whereas the phosphonates are insoluble in common organic solvents and precipitate.11 This disproportionation reaction has also been detected during the deprotonation of Mes2P(O)H with nBuLi yielding [(thf)2Li(O2PMes2)]2 and LiPMes2, whereas the addition of [Cd{N(SiMe3)2}2] stabilizes the dimesitylphosphinite anion in the complex Received: August 15, 2016
A
DOI: 10.1021/acs.inorgchem.6b01973 Inorg. Chem. XXXX, XXX, XXX−XXX
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a stronger base than THP, one ether ligand is replaced by πinteractions between one potassium ion and a side-on bound aryl group yielding [(thf)3{K(OPMes2)}4] (1b). These tetranuclear potassium phosphinites are soluble in diethyl ether, tetrahydrofuran, toluene, and hexane. The molecular structure and numbering scheme of the tetramer [(thp)K(OPMes2)]4 (1a) are shown in Figure 1,
[(Me3Si)2NCd(μ-OPMes2)2Li(thf)2] with the cadmium binding to the phosphorus atoms.12 In order to catalytically prepare R2P(E)-C(=E′)-NHR′ (E = O, S; E′ = O, S, NR′), two strategies are suitable. On the one hand, isocyanates, thioisocyanates, or carbodiimides can be hydrophosphorylated with phosphane oxides10 or sulfides. On the other hand, phosphanes can be added to these heterocumulenes13−17 followed by an oxidation of the phosphorus atoms via wellestablished protocols with, e.g., hydrogen peroxide.18 However, these addition reactions are accompanied by side-reactions because Lewis acidic metal ions are able to also trimerize isocyanates, and recently, even the characterization of an intermediate has been trapped and characterized by X-ray crystal structure determination (Scheme 2).19 Scheme 2. Simplified Representation of an Intermediate of the Trimerization of Isocyanatesa
Figure 1. Molecular structure and atom numbering scheme of [(thp)K(OPMes2)]4 (1a). The ellipsoids represent a probability of 30%, and H atoms are neglected for the sake of clarity. The four units of the tetranuclear cage compound are distinguished by the letters A, B, C, and D.
a
The isocyanate precursors are shown with different colors (R = 2,6diisopropylphenyl, Cy = cyclohexyl).
On the basis of the above-mentioned findings, we got curious if the potassium compounds themselves could also act as catalysts in hydroelementation reactions because this rather soft alkali metal ion effectively binds hard Lewis bases as well as soft π-systems. Earlier investigations also demonstrated that potassium derivatives are more reactive than the lighter alkali metals in catalytic addition reactions of diphenylphosphane toward N,N′-diisopropylcarbodiimide.17 Furthermore, potassium and calcium ions are isoelectronic; however, their hardness (charge-to-radius ratio) and, hence, their Lewis acidity differ significantly. This fact could stabilize the phosphinites and suppress the disproportionation into the Ar2P− and Ar2PE2− anions (Ar = aryl). For our studies we chose the hydrophosphorylation of heterocumulenes such as isopropylisocyanates, isopropylthioisocyanates, and N,N′-dialkylcarbodiimides with dimesitylphosphane oxide and diphenylphosphane sulfide to elucidate the influence of the chalcogen atom and of the steric demand of diarylphosphane chalcogenides.
Table 1. K−O Bond Lengths (pm) of the K4O4 Heterocubane Cage of [(thp)K(OPMes2)]4 (1a) and [(thf)3{K(OPMes2)}4] (1b) Complex 1a O1A O1B O1C O1D O2A O2B O2C O2D Complex 1b O1A O1B O1C O1D O2A O2B O2C
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RESULTS AND DISCUSSION Synthesis of the Catalysts. The potassium-based catalyst can easily be prepared via the deprotonation of dimesitylphosphane oxide and diphenylphosphane sulfide with potassium hydride in ethereal solvents such as tetrahydropyran (THP) and tetrahydrofuran (THF) according to Scheme 3. The tetrahydropyran adduct of potassium dimesitylphosphinite forms the tetramer [(thp)K(OPMes2)]4 (1a) in the solid state with a slightly distorted K4O4 heterocubane cage. Synthesis of this catalyst in tetrahydrofuran leads to a very similar heterocubane cage. Despite the fact that THF represents
K1A
K1B
261.2(2) 278.6(2)
270.2(2) 261.5(2) 270.6(2)
269.9(2) 273.1(2)
K1C
K1D 278.0(2)
266.6(2) 260.5(2) 276.3(2)
273.8(2) 259.2(2)
265.6(2) 268.6(2) 271.2(2) 274.5(2) 267.5(2) 263.4(2)
260.5(2) 274.0(2) 268.7(2)
277.0(2) 273.2(2) 290.2(2)
264.2(2) 282.9(2) 258.8(2)
271.6(3) 267.0(2) 267.1(2)
selected bond lengths are summarized in Table 1. The K−O distances within the heterocubane cage and to the ether ligands are similar. All phosphinite ions show very similar structural parameters (Table 2) with the phosphorus atoms in trigonal pyramidal environments with angle sums of approximately 315°. The molecular structure and numbering scheme of [(thf)3{K(OPMes2)}4] (1b) are shown in Figure 2, and selected bond lengths and angles are included in Tables 1
Scheme 3. Synthesis of KEPAr2 (E = O, S; Ar = Ph, Mes; L = thf, thp)
B
DOI: 10.1021/acs.inorgchem.6b01973 Inorg. Chem. XXXX, XXX, XXX−XXX
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Inorganic Chemistry Table 2. Environments of the Phosphorus Atoms in [(thp)K(OPMes2)]4 (1a) and [(thf)3{K(OPMes2)}4] (1b) (Bond Lengths [pm] and Angles [deg]) Complex 1a O1 C1 C10 O1−P1−C1 O1−P1−C10 C1−P1−C10 angle sum Complex 1b O1 C1 C10 O1−P1−C1 O1−P1−C10 C1−P1−C10 angle sum
P1A
P1B
P1C
P1D
156.4(2) 187.3(3) 187.3(3) 110.9(1) 103.7(1) 100.4(1) 315.0
156.7(2) 187.1(3) 187.9(3) 110.6(1) 102.9(1) 101.0(1) 314.5
156.3(2) 187.8(3) 187.2(3) 105.5(1) 110.6(1) 100.5(1) 316.6
156.4(2) 187.0(3) 187.8(3) 110.8(1) 103.5(1) 100.3(1) 314.6
157.0(2) 187.3(3) 187.6(3) 111.4(1) 103.7(1) 98.8(1) 313.9
157.0(2) 186.5(3) 188.0(3) 109.6(1) 104.3(1) 99.6(1) 313.5
156.9(2) 187.4(3) 187.4(3) 100.9(1) 111.8(1) 100.8(1) 313.5
156.4(2) 186.8(3) 188.5(3) 111.2(1) 104.5(1) 101.4(1) 317.1
Figure 3. Molecular structure and atom numbering scheme of the asymmetric unit of [(thp)KSPPh2]∞ (2) (top). The ellipsoids represent a probability of 30%, H atoms are shown with arbitrary radii. At the bottom the ribbon-like aggregation is presented, neglecting all H atoms.
reasons also the structure of diphenylphosphane sulfide has been determined. The asymmetric unit contains two crystallographically independent molecules A and B; only molecule A is shown in Figure 4, molecule B is very similar, and the bond
Figure 2. Molecular structure and numbering scheme of [(thf)3{K(OPMes2)}4] (1b). The ellipsoids represent a probability of 30%, H atoms are omitted for clarity reasons. The four units of the tetranuclear cage compound are distinguished by the letters A, B, C, and D. The potassium atom K1D shows a π-interaction to an aryl group, and no ether molecule is bound to this alkali metal atom.
and 2. The side-on coordination of the aryl group leads to insignificant distortions of the heterocubane moiety, and the angle sum of the respective phosphorus atom P1C shows the same magnitude than the other P atoms. In both tetranuclear complexes the P−O bonds are approximately 8 pm longer compared to diphenylphosphane oxide (P−O 148.8(1), av. P− C 180.0 pm).10 In agreement with the expectation that a higher electron density at the phosphorus atom enhances the radius of the atom, also the P−C bonds of the potassium phosphinites 1a and 1b are elongated by approximately 7 pm compared to diphenylphosphane oxide. A surprisingly different molecular structure is realized for [(thp)KSPPh2]∞ (2) even though the composition is alike. This compound crystallizes with a ribbon-like structure; a part of the structure and the numbering scheme are represented in Figure 3. The sulfur atoms exhibit a coordination number of four, but the coordination mode of the thiophosphinites is quite unique. The potassium atom K1 binds side-on to the P−S bond with K1−S1A and K1−P1A distances of 315.52(7) and 337.70(6) pm, respectively. Furthermore, the potassium atom shows π-interactions to a phenyl group. For comparison
Figure 4. Molecular structure and atom numbering scheme of Ph2P(S)H. The ellipsoids represent a probability of 30%, H atoms are drawn with arbitrary radii. The asymmetric unit contains two molecules A and B; only molecule A is depicted. Selected bond lengths (pm) of molecule A [molecule B]: P1−S1 195.60(7) [195.52(7)], P1−C1 181.1(2) [180.4(2)], P1−C7 180.7(2) [180.8(2)], P1−H1 133(2) [137(2)]; angles (deg.): C1−P1−C7 105.97(9) [106.94(9)], S1−P1−C1 113.92(7) [114.49(7)], S1−P1− C7 114.67(7) [113.78(7)], S1−P1−H1 114.5(9) [113.8(8)], C1− P1−H1 104.9(9) [102.9(8)], C7−P1−H1 101.5(9) [103.8(8)]. C
DOI: 10.1021/acs.inorgchem.6b01973 Inorg. Chem. XXXX, XXX, XXX−XXX
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Inorganic Chemistry lengths are added in square brackets. In agreement with the structural data of the oxygen-containing congeners, the average P−S bond length of 195.6 pm and the average P−C bond length of 180.0 pm in Ph2P(S)H are significantly shorter than those in the potassium derivative 2. All these potassium (thio)phosphinites slowly show the disproportionation products Ph2P− as well as Ph2PO2− and Ph2PS2−, respectively, in ethereal solvents. Therefore, freshly prepared solutions of the catalyst in tetrahydrofuran were employed for all catalysis studies. Catalytic Reactivity. In order to elucidate the influence of the P-bound chalcogen atom and the reactivity toward heterocumulenes, the addition of dimesitylphosphane oxide and of diphenylphosphane sulfide across isopropylisocyanate, isopropylthioisocyanate, and N,N′-dialkylcarbodiimide was investigated in tetrahydrofuran solution at room temperature. An aliquot of a freshly prepared THF solution of KOPPh2 or KSPPh2 (0.05 equiv) was added to the reaction mixture containing 1 equiv of diarylphosphane oxide or sulfide and 1.1 equiv of the heterocumulene. Dimesitylphosphane oxide (E = O) and diphenylphosphane sulfide (E = S) show no reaction toward these heterocumulenes in the absence of a catalyst. Therefore, in all cases 5 mol % (with respect to a mononuclear species regardless of the above-mentioned solid state structures) of the appropriate catalyst Ar2PEK (Ar = Ph, Mes; E = O, S) were added. The catalytic conversion of iPr− NCE′ (E′ = O, S) and of R-NCN-R (R = iPr, cHex) to the addition products Ar2P(E)-C(=E′)-NHR (Ar = Ph, Mes; E = O, S; E′ = O, S, NR) was studied and is summarized in Scheme 4.
Figure 5. Decrease of the concentration of Mes2P(O)H during the catalytic reaction with isopropylisocyanate (red) and increase of the product Mes2P(O)-C(O)-NHiPr (black). The half-life is approximately 4 h.
Table 3. Potassium-Mediated Synthesis of Ar2P(E)-C(=E′)NHR in Tetrahydrofuran at Room Temperaturea E
Ar
E′
R
time [h]
conversion [%]
O
Mes Mes Mes Ph Mes Mes Ph Ph Ph Ph Ph
O O S NR NR NR O O S NR NR
iPr cHex iPr iPr iPr cHex iPr cHex iPr iPr cHex
42 48 0.5 0.5 72 72 0.5 0.5 1 24 72
100 100 100 100 0 0 100 100 100 100 100
S
Scheme 4. Synthesis of Ar2P(E)-C(=E′)-NHR (Ar = Ph, Mes; E = O, S; E′ = O, S, NR) via the Potassium-Mediated Addition of Ar2P(E)H to iPr−NCE′ (E′ = O, S) and RNCN-R
yield [%] 79 75 88 71 0 0 82 65 78 62 80
(3a) (3b) (3c) (3d)
(4a) (4b) (4c) (4d) (4e)
a
The conversion was determined by 31P NMR spectroscopy with respect to the phosphorus component, the yields refer to isolated crystalline compounds.
decreases and the activity of the newly formed degradation species (KPPh2 and KE2PPh2) is unknown. Nevertheless, a nearly zero order catalysis can be estimated under these reaction conditions. In Table 3 the results of the potassium-mediated addition of Ar2P(E)H across heterocumulenes are summarized. It is immediately clear that the diphenylphosphane sulfides react much more smoothly than the dimesitylphosphane oxides, and significantly shorter reaction times lead to a complete conversion. The dialkylcarbodiimides do not react with dimesitylphosphane oxide under these reaction conditions. However, the addition of diphenylphosphane sulfide proceeds slowly, and extended reaction times are required. In the last column of Table 3 the isolated crystalline yields are given. In Figure 6, the 31P{1H} NMR spectra of the reaction solution of Ph2P(S)H, cHex-NCN-cHex, and 5 mol % of KSPPh2 are shown after protolysis with ethanol. The resonances are marked by colored frames. Two resonances with an intensity ratio of 2:1 can be addressed to the E and Z isomers of the product Ph 2 P(S)-C(N-cHex)-N(H)cHex. The resonances of Ph2P(S)H originate from the starting material but also from the protolysis of the potassium-based catalyst. The two other resonances in the blue and yellow boxes represent the compounds Ph 2 P(S)SH and Ph 2 PH that form during disproportionation of the catalyst and subsequent protolysis with ethanol. The disproportionation of the diarylthiophosphinites is observed during the extended reaction times and has
In diarylphosphane oxides and sulfides the phosphorus atoms are in distorted tetrahedral environments. Deprotonation (potassiation) leads to the (thio)phosphinites with a threecoordinate P atom. The thus-formed vacant coordination site might enable the addition to a heterocumulene system and formation of a new P−C bond, yielding the products shown in Scheme 4. The 31P NMR spectroscopic monitoring of the catalytic addition of Mes2P(O)H to isopropylisocyanate shows the changes of the concentrations of all P-containing compounds (Figure 5). For the determination of the conversion (Table 3) every hour an aliquot of the reaction solution was quenched with ethanol in order to deactivate the catalyst. Triphenylphosphane was added as an internal reference to quantify the conversion and the yields of the product. Because this protolysis reaction yielded dimesitylphosphane oxide from the catalytically active potassium dimesitylphosphinite, a small amount of Mes2P(O)H is also present after complete conversion. In Figure 5 the time-dependent increase of the product Mes2P(O)-C(O)-NHiPr and the decrease of the substrate Mes2P(O)H during catalytic conversion is shown. The half-life is approximately 4 h. Quantification must be defective due to the fact that the concentration of the catalyst D
DOI: 10.1021/acs.inorgchem.6b01973 Inorg. Chem. XXXX, XXX, XXX−XXX
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homologous sulfides. Selected spectroscopic parameters of the (thio)formamides and -amidines Ar2P(E)-C(=E′)-NHR (Ar = Ph, Mes; E = O, S; E′ = O, S, NR) are listed in Table 4. In order to elucidate the influence of the heavier chalcogen atom on the structural parameters of Ar2P(E)-C(=E′)-NHR the crystal structures of the isopropyl derivatives (R = iPr) were determined at single crystals. Selected structural data are listed in Table 5 and compared with Ph2P(O)-C(O)-N(H)iPr (I) and Ph2P(O)-C(S)-N(H)iPr (II). The molecular structures and numbering schemes of Mes2P(O)-C(O)-N(H)iPr and Ph2P(S)-C(S)-N(H)iPr are depicted in Figures 7 and 8. The steric influence of the P-bound mesityl groups and of the chalcogen atoms can be recognized. In all these molecules, the average P−CAr bond lengths are significantly smaller than the P1−C1 (P−CCE′) values. This finding is caused by electrostatic repulsion between the positively polarized carbon and phosphorus atoms as depicted in Scheme 5. The bonding situation of phosphane oxides in general are discussed in detail elsewhere.20 The formamide backbone P−C(E′)−N−CiPr is quite similar in all derivatives within the 3-fold standard deviation. The bulkiness of the mesityl groups leads to distortion of the environment of the phosphorus atoms and different CCE′−P−CAr1/2 bond angles are observed; also the E− P−CAr1/2 angles to the mesityl groups differ significantly, whereas rather similar values are observed for phenylsubstituted derivatives. In summary, the bulky mesityl groups lead to a slight elongation of the P−C bonds by approximately 1.5 pm and to significant distortion of the tetrahedral environment of the phosphorus atoms.
Figure 6. 31P{1H} NMR spectra of the protolyzed reaction solution of diphenylphosphane sulfide with dicyclohexylcarbodiimide in tetrahydrofuran in the presence of 5 mol % of KSPPh2 after 24 h (top) and 48 h (bottom) at room temperature (162 MHz, [D8]THF, r.t.), see text.
also been detected for the diarylphosphinites during phosphane oxide addition reactions. In order to clarify whether the bulkiness of the P-bound mesityl groups or the chalcogen atoms E = O are responsible for the lack of reactivity, the potassium-mediated addition was repeated with a reaction mixture of diphenylphosphane oxide and diisopropylcarbodiimide under similar reaction conditions as mentioned above. Now a potassium-mediated reaction occurs, and a quantitative conversion is already achieved after 30 min. This finding verifies that the intermolecular hindrance of the P-bound mesityl groups and the N-bound isopropyl groups of the carbodiimide prevent the addition reaction and that the diphenylphosphane oxides are more reactive than the
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CONCLUSION The potassium diarylphosphinites and thiophosphinites are catalytically active and mediate the addition of diarylphosphane oxide and sulfide, respectively, to heterocumulenes of the type R-NCE′ with E′ = O, S. The diphenylphosphane sulfide is much more reactive in the presence of potassium thiophosphinites than the oxygen-containing congeners. Thus, only
Table 4. Selected NMR (Chemical Shifts [ppm] and Coupling Constants [Hz]) and IR Parameters (Wave Numbers [cm−1]) of Ar2P(E)-C(=E′)-N(H)R E
Ar
O
Mes Ph Mes Ph Ph Ph Ph Ph Ph Ph Ph Ph Ph Ph Ph Ph Ph
S
Se
E′ O O S S NR NR O O S NR NR NR NR NR NR NR NR
(E) (Z)
(E) (Z) (E) (Z) (E) (Z) (E) (Z)
R
δ(31P)
δ(13CCE′)
iPr iPr iPr iPr iPr iPr iPr cHex iPr iPr iPr cHex cHex iPr iPr cHex cHex
19.7 14.8 28.4 20.6 19.6 15.8 31.4 31.4 45.0 35.9 31.0 37.1 33.6 23.2 35.2 23.9 35.5
171.8 168.7 200.7 195.4 147.0 148.5 166.0 166.0 190.9 146.30, 143.52b
113.5 120.7 77.1 87.4 80.2 154.7 98.2 98.2 65.1 143.5, 54.1b
3243 3273 3243 3138 3379, 3277a
1648 1641 1648 1510 1602a
3316 3305 3169 3425
1656 1661 1503 1609
c
146.2, 143.3
133.6, 53.2
3304a
1608a
c
145.9, 141.6b
122, 42b
3321a
1614a
145.6, 141.3b
123, 43b
3428, 3304, 3262a
1614a
16d 16d 16d 16d
1
J(P−CCE′)
ν(N−H)
ν(C = E′)
ref 10 10
a
No differentiation of the frequencies of E- and Z-isomer possible. bNo assignment of the signals to the E-/Z-isomer. cNMR data are in agreement with published values;16b the compounds were prepared via oxidation of the phosphanyl derivatives with sulfur. dCompounds were synthesized via oxidation of the phosphanyl derivatives with selenium. E
DOI: 10.1021/acs.inorgchem.6b01973 Inorg. Chem. XXXX, XXX, XXX−XXX
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Table 5. Selected Structural Parameters (Bond Lengths [pm] and Angles [deg] of Mes2P(O)-C(O)-N(H)iPr and Ph2P(S)C(S)-N(H)iPr as Characteristic Representatives of the Substance Class of Ar2P(E)-C(=E′)-NHR
a
Ar/E/E′
Ph/O/O (I)
Mes/O/O (A)
Mes/O/O (B)
Ph/O/S (II)
Ph/S/S
av. P−CAr PE P−CCE′ CCE′E′ CCE′−N N−CiPr P−CCE′−N P−CCE′−E′ N−CCE′−E′ E−P−CCE′ E−P−CAr1 E−P−CAr2 CCE′−P−CAr1 CCE′−P−CAr2 CAr1−P−CAr2 CCE′−N−CiPr
179.8 149.29(9) 186.4(1) 123.2(2) 132.8(2) 147.1(2) 113.25(9) 120.88(9) 125.9(1) 111.61(6) 112.64(5) 113.63(5) 104.20(6) 106.18(6) 107.95(6) 123.1(1)
181.5 149.4(2) 187.5(2) 123.4(3) 132.9(4) 146.6(3) 111.5(2) 122.3(2) 125.8(2) 109.9(1) 109.1(1) 115.2(1) 112.9(1) 99.8(1) 109.8(1) 123.2(2)
181.6 149.3(2) 188.0(3) 122.9(3) 132.8(4) 146.9(3) 112.5(2) 121.4(2) 125.7(2) 110.2(1) 109.7(1) 115.1(1) 112.3(1) 101.1(1) 108.2(1) 122.6(2)
179.8 149.4(1) 184.2(2) 166.4(2) 131.8(2) 147.5(2) 112.8(1) 119.43(9) 127.7(1) 110.62(7) 110.97(7) 113.19(7) 109.75(7) 103.00(7) 109.01(7) 124.9(1)
180.6 196.08(5) 186.6(2) 166.0(2) 131.8(2) 147.0(2) 112.3(1) 120.13(9) 127.5(1) 110.54(5) 113.83(5) 114.06(5) 104.25(7) 106.48(7) 106.98(7) 125.6(1)
For comparison reasons also the data of Ph2P(O)-C(O)-N(H)iPr (I) and Ph2P(O)-C(S)-N(H)iPr (II) are included.
Figure 8. Molecular structure and atom numbering scheme of Ph2P(S)-C(S)-N(H)iPr. The ellipsoids represent a probability of 30%; H atoms are shown with arbitrary radii.
Figure 7. Molecular structure and atom numbering scheme of Mes2P(O)-C(O)-N(H)iPr. The ellipsoids represent a probability of 30%, H atoms are omitted for the sake of clarity. The asymmetric unit contains two molecules A and B; only molecule A is depicted.
Scheme 5. Valence Bond Representation of the Starting Materials (Top) and Products (Bottom) Clarifying the Phosphonium-type Nature of the P Atoms and the Electrostatic Repulsion between P and CCE′ (Ar = aryl; E, E′ = O, S)
diphenylphosphane sulfide adds to dialkylcarbodiimides, whereas the dimesitylphosphane oxide shows no reactivity toward this 1,3-diazacumulene. The dialkylcarbodiimides are much less reactive than the isocyanates and isothiocyanates and require significantly extended reaction times. The potassium-based phosphinites are less reactive and promote the addition of Ar 2 P(E) to (thio)isocyanates less efficiently than the corresponding calcium-based catalyst [(thf)4Ca(OPAr2)2]. Diverse reasons may account for this finding. The enhanced Lewis acidity of Ca2+ compared with K+ ions results from a larger charge to radius ratio. Furthermore, the calcium complexes are mononuclear in ethereal solvents, whereas the potassium derivatives form aggregates that could hinder the substrate availability of the catalytic centers. Another important factor concerns the long-term stability of the catalyst. The potassium phosphinites and the calcium congeners exhibit slow disproportionation reactions in ethereal solvents yielding Ar2P− (phosphanide) and Ar2PE′2− (phosphinate) ions. Because of this reason long reaction times should
be avoided. Furthermore, the s-block metal catalysts have to be added shortly prior to the reaction; ethereal stock solutions slowly degrade under loss of catalytic reactivity. Diarylphosphane oxide and sulfide show no tendency to react with heterocumulenes such as (thio)isocyanates and F
DOI: 10.1021/acs.inorgchem.6b01973 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
relative to SiMe4 or 85% phosphoric acid as external standards. The residual signals of the deuterated solvents [D8]THF and CDCl3 were used as internal standards for 1H and 13C{1H} NMR experiments. Isopropylisocyanate and isopropylisothiocyanate were purchased from Sigma-Aldrich. All organylisocyanates or isothiocyanates were distilled under reduced pressure and saturated with nitrogen gas before use. N,N′-Diisopropylcarbodiimide and N,N′-dicyclohexylcarbodiimide were purchased from Alfa Aesar. N,N′-Diisopropylcarbodiimide was destilled under reduced pressure and saturated with nitrogen gas. N,N′-Dicyclohexylcarbodiimide was recrystallized from n-hexane in a nitrogen atmosphere. Specific amounts of the potassium-based catalysts were dissolved in anhydrous THF, and aliquots of these freshly prepared solutions were added to the reaction mixtures. The concentration of the catalyst stock solutions was verified by acidimetric titration after hydrolysis and the ratio of the integral of the 31P signal of the catalyst against PPh3 as standard. This procedure allowed us to easily add definite amounts of precatalyst to the substrates under strictly anaerobic and anhydrous conditions. Diphenylphosphane oxide,21 dimesitylphosphane oxide,22 and diphenylphospane sulfide23 were prepared according to literature procedures. Potassium-Based Catalysts. [(thp)K(OPMes2)]4 (1a). A total of 0.5 g (1.7 mmol) of HP(O)Mes2 were dissolved in 20 mL of THP at r.t., and the resulting colorless solution was added slowly to a suspension of 0.11 g (2.6 mmol) of potassium hydride in 10 mL of THP. The color immediately turned yellow, and the formation of H2 could be observed. After the suspension was stirred for 12 h at r.t., full conversion of HP(O)Mes2 was observed by 31P NMR spectroscopy. The suspension was filtered to remove excess of potassium hydride. The volume of the reaction mixture was reduced to approximately 5 mL leading to the formation of a white solid. The mixture was heated to 60 °C to give a clear solution and slowly cooled to r.t. Storage at 4 °C overnight led to a white microcrystalline solid, which was collected and washed twice with 2 mL of cold n-hexane yielding 0.48 g (1.2 mmol, 67%) of [(thp)K(OPMes2)]4. Mp 93 °C (deg.). 1H NMR (400 MHz, [D8]THF) δ = 6.55 (s, 4H, CHMes), 3.57−3.52 (m, 4H, thp), 2.39 (s, 12H, o-CH3‑Mes), 2.14 (s, 6H, p-CH3‑Mes), 1.61 (m, 2H, thp), 1.51 (m, 4H, thp). 13C{1H} NMR (101 Hz, [D8]THF): δ = 147.6 (d, 1 JP−C = 57.9 Hz, ipso-CMes), 140.5 (d, 2JP−C = 13.7 Hz, o-CMes), 135.1 (p-CMes), 129.8 (CHMes), 69.1 (thp), 27.7 (thp), 24.6 (thp), 21.5 (d, 3 JP−C = 15.9 Hz, o-CH3‑Mes), 21.1 (p-CH3‑Mes). 31P NMR (162 MHz, [D8]THF) δ = 95.9. IR (neat): ṽ (cm−1) = 2934 m (CH3), 2917 m (CH3), 2845 w (CH2), 1603 m (CC), 1451 m, 1191 m, 1171 m, 1085 s (P−O), 1044 s, 1028 s, 937 s, 847 s, 641 s, 592 m, 422 s. Single crystals suitable for X-ray diffraction analysis were obtained within 3 days at r.t. by layering the mother liquor with 2 mL of n-hexane. [(thp)K(SPPh2)]∞ (2). HP(S)Ph2 (0.75 g, 3.4 mmol) was dissolved in 40 mL of THP at r.t., and the resulting colorless solution was added slowly to a suspension of 0.21 g (5.2 mmol) of potassium hydride in 10 mL of THP. The color immediately turned yellow, and the formation of H2 was observed. After the suspension was stirred for 6 h at r.t., full conversion of HP(S)Ph2 was observed by 31P NMR spectroscopy. The suspension was filtered to remove excess of potassium hydride. The volume of the reaction mixture was reduced to approximately 15 mL and added dropwise to 40 mL of diethyl ether, which led to the immediate formation of a yellowish solid. The slightly yellow precipitate was collected and washed twice with 4 mL of cold nhexane yielding 1.05 g (3 mmol, 89%) of [(thp)K(SPh2)]∞. Mp 99 °C (degrad.). 1H NMR (400 MHz, [D8]THF) δ = 7.75 (m, 4H, m− CHPh), 7.11 (t, 3JH−H = 7.5 Hz, 2H, p−CHPh), 7.01 (t, 3JH−H = 7.2 Hz, 4H, o−CHPh), 3.59−3.51 (m, 4H, thp), 1.69−1.56 (m, 4H, thp), 1.51 (m, 2H, thp). 13C NMR (101 Hz, [D8]THF): δ = 151.9 (d, 1JP−C = 37.6 Hz, ipso-CPh), 132.5 (d, 3JP−C = 20.8 Hz, m-CHPh), 127.7 (d, 2JP−C = 5.3 Hz, o-CHPh), 126.6 (p-CHPh), 69.1 (thp), 27.7 (thp), 24.6 (thp). 31 P NMR (162 MHz, [D8]THF) δ = 26.8 (p, 3JP−H = 6.1 Hz). IR (neat): ṽ (cm−1) = 3048 w (CHaryl), 1480 m, 1435 m, 1333 w, 1309 w, 1105 s, 928 s, 913 s, 900 s, 879 s, 737 vs, 708 vs, 685 vs, 632 vs (P = S), 497 s, 463 s 428 m. Single crystals suitable for X-ray diffraction analysis were obtained by recrystallization from hot THP. General Procedure for the Catalysis. A solution of the heterocumulene (1.1 equiv with respect to Ph2P(E)H), diluted in
carbodiimides due to their tetrahedrally coordinated phosphorus atoms that sterically (kinetically) protect these substrates. Deprotonation and coordination of the metal to the chalcogen atom E open a coordination site at P and enable the addition to heterocumulenes. The potassium-mediated addition of diarylphosphane sulfides to the (thio)isocyanates is much faster than the addition of the diarylphosphane oxides. The aggregation degree of the catalyst may also account for this difference as may the varying charge on the P atoms due to a rather similar electronegativity of P and S, whereas O is significantly more electronegative, reducing the electron density on P. Another situation is observed for the hydrophosphorylation of carbodiimides because steric hindrance is induced by two Nbound alkyl groups. Thus, dimesitylphosphane oxide does not react with R-NCN-R, whereas diphenylphosphane oxide readily forms the formamidine addition product. The catalytic addition of diphenylphosphane sulfide requires a longer reaction time than the homologous oxide. A proposed catalytic cycle for the synthesis of diaryl(thio)phosphoryl-(thio)formamides and diarylthiophosphoryl-formamidines is depicted in Scheme 6. Scheme 6. Catalytic Cycle of the Potassium-Mediated Addition of Diarylphosphane Oxide and Sulfide (red) across Organic (Thio)isocyanates and Carbodiimides (Blue)
In this catalytic process the (thio)phosphinite anion binds to the carbon atom of the heterocumulene system via the phosphorus atom. This intermediate is stabilized by a heteroallylic moiety. Reaction with diarylphosphane oxide or sulfide reforms the catalyst and yields the corresponding formamides and amidines with N−H functionalities. Steric hindrance makes the addition of the thiophosphinite (E = S) to the carbodimides (yielding amidines) difficult and even prevents the addition to R-NCN-R if bulky dimesitylphosphinites (E = O) are employed.
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EXPERIMENTAL SECTION
General Remarks. All manipulations were carried out in an inert nitrogen atmosphere using standard Schlenk techniques. The solvents were dried over KOH and subsequently distilled over sodium/ benzophenone in a nitrogen atmosphere prior to use. Deuterated solvents were dried over sodium, degassed, and saturated with nitrogen. The yields given are not optimized. 1H, 13C{1H}, 31P, and 31 1 P{ H} NMR spectra were recorded on Bruker AC 400 and AC 600 spectrometers. Chemical shifts are reported in parts per million G
DOI: 10.1021/acs.inorgchem.6b01973 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
132.7 (d, 4JP−C = 2.8 Hz, p-CHPh), 132.3 (d, 2JP−C = 8.9 Hz, o-CHPh), 131.9 (d, 2JP−C = 10.8 Hz, o-CHPh), 131.3 (d, 1JP−C = 96.4 Hz, ipsoCPh), 50.7 (d, 3JP−C = 15.5 Hz, CHiPr), 43.0 (d, 3JP−C = 5.6 Hz, CHiPr), 24.4 (CH3‑iPr), 22.3 (CH3‑iPr). Zsyn δ = 148.5 (d, 1JP−C = 154.7 Hz, N = C(P(O)Ph2)-N), 132.7 (d, 1JP−C = 103.2 Hz, ipso-CPh), 131.5 (d, 4JP−C = 2.8 Hz, p-CHPh), 48.4 (d, 3JP−C = 22.1 Hz, CHiPr), 46.3 (d, 3JP−C = 7.2 Hz, CHiPr), 24.6 (CH3‑iPr), 24.3 (d, 4JP−C = 1.4 Hz, CH3‑iPr). 31P NMR (162 MHz, CDCl3) Esyn δ = 22.1 Zsyn δ = 16.7. IR (neat): ṽ (cm−1) = 3379 w (NH), 3277 w (NH), 3049 w (Ph), 2965 m (CH3), 2922 m (CH3), 2865 w (CH), 1692 m, 1602 s (C = N), 1481 m, 1462 m, 1436 s, 1360 m, 1277 m, 1226 m, 1175 s, 1155 vs, 1118 vs, 1097 s, 748 s, 724 vs, 692 vs (P = S), 647 vs, 566 vs, 544 vs, 517 vs, 495 vs, 444 s. MS (DEI): m/z (%) = 328 (60) M + H+, 202 (30) HP(O)Ph2+, 201 (45) P(O)Ph2+, 127 (100) iPrN = CNiPr + H+, 85 (70) iPrN = C-NH2+• Elemental analysis: calcd. C 69.49 H 7.67 N 8.53 found C 69.12 H 7.77 N 8.55. i Pr-NH−C(O)-P(S)Ph2 (4a). Scale: 0.64 mL (0.044 mmol, 6.9 × 10−2 M in THP) of (thp)K(SPPh2), 0.19 g (0.87 mmol) of HP(S)Ph2, 0.11 mL (1.15 mmol) of isopropylisocyanate; reaction period 0.5 h; recrystallization from n-hexane/ethyl acetate (2:1); yield: 0.22 g (0.71 mmol, 82%) of colorless crystals of iPr-NH−C(O)-P(S)Ph2. Mp 96 °C. 1H NMR (600 MHz, CDCl3) δ = 8.10 (d, 3JP−H = 6.0 Hz, 1H, NH), 8.02−7.91 (m, 4H, m−CHPh), 7.54 (m, 2H, p−CHPh), 7.47 (m, 4H, o−CHPh), 4.19−4.06 (m, 1H, CHiPr), 1.24 (d, 3JH−H = 6.6 Hz, 6H, CH3‑iPr). 13C NMR (101 MHz, CDCl3) δ = 166.0 (d, 1JP−C = 98.2 Hz, CO), 132.3 (d, 4JP−C = 3.1 Hz, p-CHPh), 132.1 (d, 2JP−C = 10.4 Hz, oCHPh), 129.9 (d, 1JP−C = 81.4 Hz, ipso-CPh), 128.8 (d, 3JP−C = 12.6 Hz, m-CHPh), 43.2 (d, 3JP−C = 5.6 Hz, CHiPr), 22.4 (CH3‑iPr). 31P NMR (243 MHz, CDCl3) δ = 31.4. IR (neat): ṽ (cm−1) = 3316 m, 3056 w (Ph), 2971 m (CH3), 1656 vs (C = O), 1586 m, 1503 vs, 1434 vs, 1211 m, 1108 s, 1098 s, 745 s, 716 vs, 686 vs (P = S), 648 vs, 572 s, 520 vs, 492 vs, 476 s, 447 s, 434 vs MS (DEI): m/z (%) = 606 (5) 2M+, 403 (10) 2M-HP(S)Ph2+, 304 (25) M + H+, 218 (100) H2P(S)Ph2+, 185 (85) PPh2+, 140 (65) P(S)Ph+ MS (Micro-ESI, CHCl3 + MeOH, positive): m/z (%) = 629 (100) 2M + Na+, 326 (70) M + Na+ Elemental analysis: calcd. C 63.35 H 5.98 N 4.62 S 10.57 found C 63.39 H 5.68 N 4.57 S 10.31. i Pr-NH-C(S)-P(S)Ph2 (4c). Scale: 1.24 mL (0.09 mmol, 6.9 × 10−2 M in THP) of (thp)K(SPPh2), 0.37 g (1.70 mmol) of HP(S)Ph2, 0.22 mL (2.03 mmol) of isopropylisothiocyanate; reaction period 1 h; recrystallization from n-hexane/ethyl acetate (2:1); yield: 0.42 g (1.32 mmol, 78%) of yellow crystals of iPr-NH-C(S)-P(S)Ph2. Mp 107 °C. 1 H NMR (400 MHz, CDCl3) δ = 10.06 (1H, NH), 7.97 (m, 4H, m− CHPh), 7.55 (m, 2H, p−CHPh), 7.46 (m, 4H, o−CHPh), 4.83−4.26 (m, 1H, CHiPr), 1.36 (d, 3JH−H = 6.6 Hz, 6H, CH3‑iPr). 13C NMR (101 MHz, CDCl3) δ = 190.9 (d, 1JP−C = 65.12 Hz, CS), 133.0 (d, 2JP−C = 10.3 Hz, o-CHPh), 132.3 (d, 4JP−C = 3.1 Hz, p-CHPh), 130.4 (d, 1JP−C = 89.5 Hz, ipso-CPh), 128.4 (d, 3JP−C = 13.0 Hz, m-CHPh), 48.3 (d, 3JP−C = 5.7 Hz, CHiPr), 21.0 (CH3‑iPr). 31P NMR (243 MHz, CDCl3) δ = 45.0 (dq, 3JP−H = 12.4 Hz). IR (neat): ṽ (cm−1) = 3169 m (amid), 3048 m (Ph), 2966 m (CH3), 1503 s (CS), 1478 m, 1434 s, 1396 s, 1326 s, 1313 s, 1163 m, 1108 s, 1097 s, 995 m, 823 m, 744 s, 713 vs, 702 vs, 685 vs, 675 vs, 634 vs, 612 s, 573 vs, 517 vs, 486 vs, 477 vs, 431 s. MS (DEI): m/z (%) = 321 (5) M+2+, 319 (70) M+, 218 (100) HP(S)Ph2+, 185 (70) PPh2+, 140 (65) P(S)Ph+. MS (Micro-ESI, THF + MeOH, positive): m/z (%) = 342 (M+Na+) Elemental analysis: calcd. C 60.16 H 5.68 N 4.39 S 20.07 found C 60.54 H 5.65 N 4.43 S 20.77. i PrN(H)−C(P(S)Ph2) = NiPr (4d). Scale: 0.78 mL (0.09 mmol, 1.1 • −2 10 M in THP) of (thp)K(SPPh2), 0.39 g (1.79 mmol) of HP(S)Ph2, 0.3 mL (1.97 mmol) of N,N′-Diisopropylcarbodiimide; reaction period 24 h; Recrystallization from n-hexane; yield: 0.38 g (1.10 mmol, 62%) of colorless crystals of E/Z-mixture of iPrN(H)−C(P(S)Ph2) = NiPr. Mp 81 °C. 1H NMR (400 MHz, CDCl3) Zsyn δ = 7.85 (dd, 3JH−H = 13.5 Hz, 7.0 Hz, 4H, o−CHPh), 7.60−7.43 (m, 6H, m−CHPh + p− CHPh), 4.96 (1H, NH), 3.91 (m, 2H, CH−iPr), 1.13 (d, 3JH−H = 6.5 Hz, 6H, CH3‑iPr), 0.79 (d, 3JH−H = 5.9 Hz, 6H, CH3‑iPr). Esyn δ = 8.03 (dd, 3 JH−H = 12.9 Hz, 7.4 Hz, 4H, o−CHPh), 7.45−7.39 (m, 6H, m−CHPh + p−CHPh), 6.23 (1H, NH), 4.03 (m, 2H, CH−iPr), 1.18 (d, 3JH−H = 6.3 Hz, 6H, CH3‑iPr), 1.10 (d, 3JH−H = 6.3 Hz, 6H, CH3‑iPr). 13C NMR (151
approximately 2.5 mL of THF per mmol heterocumulene, was added dropwise to a slightly yellow mixture of potassium phosphinite (0.05 equiv in THP) and phosphane chalcogenide (1 equiv) in THF (approximately 10 mL of THF per mmol chalcogenide). The conversion of the substrates was monitored with 31P NMR experiments at the resonance of phosphane oxide/sulfide. After full conversion was achieved, the reaction solution was quenched with ethanol and the solvent was removed. The residue was dissolved in dichloromethane and filtered. The clear solutions were concentrated which led to the formation of solids (E′ = O, S) or oily liquids (E′ = NR). Solids were recrystallized yielding analytical pure crystals of the formamides/thioformamides. In the case of E = NR the oily liquid was layered with n-hexane, which leads to the formation of a white solid. The solid was recrystallized to yield an E,Z-mixture of the (thio)phosphorylguanidines. Reaction Parameters and Physical Data of the (Thio)formamides and (Thio)phosphorylguanidines. iPr-NH−C(O)P(O)Mes2 (3a). Scale: 0.31 mL (0.05 mmol, 0.17 M in THP) of (thp)K(OPMes2), 0.3 g (1.05 mmol) of HP(O)Mes2, 0.11 mL (1.15 mmol) of isopropylisocyanate; reaction period 42 h; recrystallization from n-hexane; yield: 0.31 g (0.83 mmol, 61%) of colorless crystals of i Pr-NH−C(O)-P(O)Mes2. Mp 174 °C. 1H NMR (400 MHz, CDCl3) δ = 7.98 (d, 3JP−H = 7.0 Hz, 1H, NH), 6.83 (s, 4H, CHMes), 4.15 (dh, 3 JH−H = 13.2 Hz, 6.5 Hz, 1H, CHiPr), 2.37 (s, 12H, o-CH3‑Mes), 2.26 (s, 6H, p-CH3‑Mes), 1.22 (d, 3JH−H = 6.5 Hz, 6H, CH3‑iPr). 13C NMR (101 MHz, CDCl3): δ = 171.8 (d, 1JP−C = 113.5 Hz, CO), 142.1 (d, 2JP−C = 10.0 Hz, o-CMes), 141.8 (p-CMes), 131.0 (d, 3JP−C = 11.2 Hz, CHMes), 127.4 (d, 1JP−C = 95.7 Hz, ipso-CMes), 42.2 (d, 3JP−C = 4.1 Hz, CHiPr), 22.7 (d, 3JP−C = 3.7 Hz, o-CH3‑Mes), 22.3 (CH3‑iPr), 21.2 (p-CH3‑Mes). 31 P NMR (162 MHz, CDCl3) δ = 19.7. IR (neat): ṽ (cm−1) = 3243 w (amid), 2965 m (CH3), 2925 m (CH3), 1648 vs (C = O), 1602 m, 1523 m, 1447 m, 1404 m, 1384 m, 1235 m, 1184 s (P = O), 1129 s, 1076 m, 1030 m, 852 s, 731 m, 708 m, 618 vs, 575 s, 566 s, 476 s, 445 s, 413 m. MS (DEI): m/z (%) = 371 (5) M+, 286 (60) HP(O)Mes2+, 272 (100) H2PMes2+ elemental analysis: calcd. C 71.14 H 8.14 N 3.77 found C 71.14 H 8.24 N 3.85. i Pr-NH-C(S)-P(O)Mes2 (3c). Scale: 0.31 mL (0.05 mmol, 0.17 M in THP) of (thp)K(OPMes2), 0.3 g (1.05 mmol) of HP(O)Mes2, 0.12 mL (1.12 mmol) of isopropylisothiocyanate; reaction period 0.5 h; Recrystallization from n-hexane; yield: 0.36 g (0.93 mmol, 88%) of yellow crystals of iPr-NH-C(S)-P(O)Mes2. Mp 195 °C. 1H NMR (400 MHz, CDCl3) δ = 9.89 (1H, NH), 6.83 (d, 4JP−H = 4.0 Hz, 4H, CHMes), 4.87−4.72 (m, 1H, CHiPr), 2.36 (s, 12H, o-CH3‑Mes), 2.26 (s, 6H, p-CH3‑Mes), 1.35 (d, 3JH−H = 6.6 Hz, 6H, CH3‑iPr). 13C NMR (101 MHz, CDCl3): δ = 200.7 (d, 1JP−C = 77.1 Hz, CO), 142.0 (d, 2JP−C = 10.0 Hz, o-CMes), 141.5 (d, 4JP−C = 2.8 Hz, p-CMes), 131.0 (d, 3JP−C = 11.9 Hz, CHMes), 128.6 (d, 1JP−C = 102.4 Hz, ipso-CMes), 47.1 (d, 3JP−C = 5.0 Hz, CHiPr), 23.4 (d, 3JP−C = 4.1 Hz, o-CH3‑Mes), 21.2 (d, 4JP−C = 1.2 Hz, CH3‑iPr), 20.7 (p-CH3‑Mes).31P NMR (162 MHz, CDCl3) δ = 28.4. IR (neat): ṽ (cm−1) = 3163 m (amid), 2966 m (CH3), 2926 m (CH3), 1602 m, 1555 m, 1513 s (C = S), 1444 s, 1404 m, 1381 s, 1163 m, 1145 vs (P = O), 1128 s, 997 vs, 847 s, 823 m, 696 s, 657 vs, 611 s, 568 vs, 511 s, 474 vs, 432 s. MS (DEI): m/z (%) = 387 (10) M+, 286 (55) HP(O)Mes2+, 271 (100) H2PMes2+ Elemental analysis: calcd. C 68.19 H 7.80 N 3.61 S 8.27 found C 68.20 H 7.44 N 3.62 S 8.0. i PrN(H)−C(P(O)Ph2) = NiPr (3d). Scale: 1.0 mL (0.1 mmol, 9.5 • 10−2 M in THP) of (thp)K(OPPh2), 0.4 g (1.94 mmol) of HP(O)Ph2, 0.30 mL (2.01 mmol) of N,N′-Diisopropylcarbodiimide; reaction period 0,5 h; Recrystallization from n-hexane; yield: 0.45 g (1.37 mmol, 71%) of colorless crystals of E/Z-mixture of iPrN(H)− C(P(O)Ph2) = NiPr. Mp 68 °C. 1H NMR (400 MHz, CDCl3) Esyn δ = 7.81−7.70 (m, 4H, o−CHPh), 7.64−7.56 (m, 2H, p−CHPh), 7.51 (m, 4H, m−CHPh), 5.18 (m, 1H, NH), 4.13−4.00 (m, 1H, CH−iPr), 3.74 (h, 3JH−H = 5.9 Hz, 1H, CH−iPr), 1.15 (d, 3JH−H = 6.4 Hz, 6H, CH3‑iPr), 0.73 (d, 3JH−H = 6.0 Hz, 6H, CH3‑iPr). Zsyn 8.02−7.90 (m, 4H, o− CHPh), 7.46 (m, 2H, p−CHPh), 7.40 (m, 4H, m−CHPh), 5.45 (t, 3 JH−H/H‑P = 9.3 Hz, 1H, NH), 4.01 (m, 1H, CH−iPr), 3.90−3.80 (dhept, 3 JH−H = 6.2 Hz, 3JP−H = 1.6 Hz, 1H, CH−iPr), 1.15 (d, 3JH−H = 6.4 Hz, 6H, CH3‑iPr), 1.10 (d, 3JH−H = 4.9, 6H, CH3‑iPr).13C NMR (151 MHz, CDCl3) Esyn δ = 147.0 (d, 1JP−C = 80.2 Hz, N = C(P(O)Ph2)-N), H
DOI: 10.1021/acs.inorgchem.6b01973 Inorg. Chem. XXXX, XXX, XXX−XXX
Inorganic Chemistry
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MHz, CDCl3) δ = 146.3 (d, 1JP−C = 133.9 Hz, N = C(P(S)Ph2)-N), 143.5 (1JP−C = 54.1 Hz, N = C(P(S)Ph2)-N), 132.7 (d, 1JP−C = 85.1 Hz, ipso-CPh), 132.6 (d, 2JP−C = 10.0 Hz, o-CHPh), 132.1 (d, 4JP−C = 2.3 Hz, p-CHPh), 132.0 (d, 2JP−C = 11.3 Hz, o-CHPh), 131.6 (ipso-CPh), 131.3 (d, 4JP−C = 2.7 Hz, p-CHPh), 129.0 (d, 3JP−C = 12.4 Hz, m-CHPh), 127.9 (d, 3JP−C = 12.6 Hz, m-CHPh), 50.6 (d, 3JP−C = 16.2 Hz, CHiPr), 49.2 (d, 3JP−C = 21.9 Hz, CHiPr), 46.8 (d, 3JP−C = 8.9 Hz, CHiPr), 43.6 (d, 3JP−C = 5.5 Hz, CHiPr), 24.3 (CH3‑iPr), 24.2 (CH3‑iPr), 24.0 (CH3‑iPr), 22.2 (CH3‑iPr). 31P NMR (162 MHz, CDCl3) Esyn δ = 35.8 Zsyn δ = 31.0. IR (neat): ṽ (cm−1) = 3425m (NH), 3049w (Ph), 2962m (CH3) 2883w (CH), 1690w, 1609vs (CN), 1491m, 1478m, 1465m, 1435s, 1362s, 1311m, 1227m, 1173s, 1124s, 1094vs, 751s, 722vs, 708vs, 691vs (P = S), 647vs, 558vs, 514vs, 483vs, 464s, 441s. MS (DEI): m/z (%) = 346 (5) M+2+, 344 (25) M+H+, 218 (5) HP(S)Ph2+, 183 (20) PPh2+, 127 (100) iPrNCNiPr+H+, 85 (90) i PrNC-NH2+•, 43 (50) C3H7+• Elemental analysis: calcd. C 66.25 H 7.32 N 8.13 S 9.31 found C 66.61 H 7.24 N 8.12 S 9.31. CyN(H)−C(P(S)Ph2)NCy (4e). Scale: 0.9 mL (0.06 mmol, 6.9 × 10−2 M in THP) of (thp)K(SPPh2), 0.27 g (1.25 mmol) of HP(S)Ph2, 0.3 mL (1.37 mmol) of N,N′-dicyclohexylisocyanate; reaction period 72 h; recrystallization from n-hexane; yield: 0.43 g (1.00 mmol, 82%) of colorless crystals of CyN(H)−C(P(S)Ph2)NCy. Mp 106 °C. 1H NMR (400 MHz, CDCl3): Esyn δ = 8.00 (dd, 3JH−H = 12.9 Hz, 7.3 Hz, 4H, o−CHPh), 7.51−7.38 (m, 4H, m−CHPh + p−CHPh), 6.45 (m, 1H, NH), 3.49−3.29 (m, 2H, CHCy) 1.92−0.72 (m, 22H, CH2‑Cy). Zsyn δ = 7.84 (dd, 3JH−H = 13.4 Hz, 7.0 Hz, 4H, o−CHPh), 7.51−7.38 (m, 4H, m−CHPh + p−CHPh), 5.24 (m, 1H, NH), 3.79 (m, 1H, CHCy), 3.57 (m, 1H, CHCy), 1.92−0.72 (m, 22H, CH2‑Cy). 13C NMR (101 MHz, CDCl3) δ = 146.2 (d, 1JP−C = 133.6 Hz, NC(P(S)Ph2)-N), 143.3 (1JP−C = 53.2 Hz, NC(P(S)Ph2)-N), 132.8 (d, 1JP−C = 85.0 Hz, ipsoCPh), 132.6 (d, 2JP−C = 10.0 Hz, o-CHPh), 132.0 (d, 4JP−C = 3.2 Hz, pCHPh), 131.9 (d, 2JP−C = 11.3 Hz, o-CHPh), 131.7 ((ipso-CPh), 131.4 (d, 4JP−C = 2.9 Hz, p-CHPh), 128.9 (d, 3JP−C = 12.5 Hz, m-CHPh), 127.9 (d, 3JP−C = 12.5 Hz, m-CHPh), 58.4 (d, 3JP−C = 15.5 Hz, CHCy), 57.3 (d, 3JP−C = 21.6 Hz, CHCy), 53.8 (d, 3JP−C = 8.5 Hz, CHCy), 49.8 (d, 3 JP−C = 4.7 Hz, CHCy), 34.4 (CH2‑Cy), 34.3 (CH2‑Cy), 34.2 (CH2‑Cy), 31.9 (CH2‑Cy), 26.1 (CH2‑Cy), 26.0 (CH2‑Cy), 25.8 (CH2‑Cy), 25.6 (CH2‑Cy), 24.6 (CH2‑Cy), 24.6 (CH2‑Cy), 24.4 (CH2‑Cy), 24.3 (CH2‑Cy). 31 P NMR (162 MHz, CDCl3) Esyn δ = 37.1 Zsyn δ = 33.6. IR (neat): ṽ (cm−1) = 3304 m (NH), 3051 w (Ph), 2921 s (CH3) 2847 s (CH), 1697 w, 1608 vs (CN), 1491 s, 1445 m, 1432 vs, 1363 m, 1346 m, 1308 m, 1103 vs, 1070 s, 1025 s, 886 m, 754 m, 742 s, 712 vs, 689 vs (PS), 644 vs, 611 vs, 585 s, 531 vs, 501 vs, 480 vs, 456 vs, 443 vs, 424 vs MS (DEI): m/z (%) = 217 (10) P(S)Ph2+, 207 (100) CyN CNCy+H+, 125 (55) CyNC-NH2+ ESI (MeOH, positive): m/z (%) = 427 (13) M + 2 + H+, 426 (45) M + 1 + H+, 425 (100) M + H+ Elemental analysis: calcd. C 70.72 H 7.83 N 6.60 S 7.55 found C 71.05 H 7.86 N 6.63 S 7.37. Crystal Structure Determinations. The intensity data for the compounds were collected on a Nonius KappaCCD diffractometer using graphite-monochromated Mo−K α radiation. Data were corrected for Lorentz and polarization effects; absorption was taken into account on a semiempirical basis using multiple-scans.24−26 The structures were solved by direct methods (SHELXS)27 and refined by full-matrix least-squares techniques against Fo2 (SHELXL-97).27 All hydrogen atoms of the compounds 2, Ph2P(S)H and 4c plus the hydrogen atoms of the amine groups of 3a were located by difference Fourier synthesis and refined isotropically. The other hydrogen atoms were included at calculated positions with fixed thermal parameters. All nondisordered, non-hydrogen atoms were refined anisotropically.27 The crystal of 1a contains large voids, filled with disordered solvent molecules. The size of the voids is 2411 Å3/unit cell. Their contribution to the structure factors was secured by back-Fourier transformation using the SQUEEZE routine of the program PLATON28 resulting in 699 electrons/unit cell. Crystallographic data as well as structure solution and refinement details are summarized in the Supporting Information. XP (Siemens Analytical X-ray Instruments, Inc.)29 and POV-Ray30 were used for structure representations.
Article
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b01973. Crystallographic data (excluding structure factors) has been deposited with the Cambridge Crystallographic Data Centre as supplementary publication CCDC1488684 for 1a, CCDC-1488685 for 1b, CCDC-1488686 for 2, CCDC-1488689 for Ph2P(S)H, CCDC-1488687 for 3a, and CCDC-1488688 for 4c. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [E-mail:
[email protected]]. CIF files giving crystallographic data of the crystal structure determinations (CIF) Preparative details and physical data of all reported compounds, tables, figures as well as the NMR spectra of all new compounds (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]; fax: +49 3641 948132. Funding
We appreciate the financial support of the Fonds der Chemischen Industrie (Verband der Chemischen Industrie e.V., FCI/VCI, Frankfurt/Main, Germany). Notes
The authors declare no competing financial interest.
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REFERENCES
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