and Tris(3-aminopropyl)amine - American Chemical Society

Mar 12, 2015 - •S Supporting Information. ABSTRACT: The N,N′,N″-triphenyl-substituted derivative of tris(2-aminoethyl)phosphine (Ph3-phospha-tre...
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Phospha Derivatives of Tris(2-aminoethyl)amine (tren) and Tris(3aminopropyl)amine (trpn): Synthesis and Complexation Studies with Group 4 Metals Malte Sietzen, Sonja Batke, Lukas Merz, Hubert Wadepohl, and Joachim Ballmann* Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 276, 69120 Heidelberg, Germany S Supporting Information *

ABSTRACT: The N,N′,N″-triphenyl-substituted derivative of tris(2-aminoethyl)phos phine ( Ph 3 - p ho s ph a -t r e n, P(CH2CH2NHR)3, R = Ph) and four derivatives of the related tris(3-aminopropyl)phosphine (phospha-trpn, P(CH2CH2CH2NHR)3, R = iPr, tBu, SitBuMe2, Ph) have been synthesized in addition to the parent phospha-trpn. Out of these ligand systems, only the N,N′,N″-triphenyl-substituted phosphatrpn derivative P(CH2CH2CH2NHPh)3 was found to be suitable for coordination to group 4 metals. For titanium, zirconium, and hafnium, the C3-symmetric endo-P-configured dimethylamido complexes Ph[PN3]M(NMe2) of the former ligand have been prepared and converted into the corresponding triflates Ph[PN3]M(OTf). Starting from these triflates, the benzyl complexes Ph [PN3]M(Bn) (M = Ti, Zr, Hf) have been obtained via reaction with Bn2Mg(THF)2. In case of titanium, the benzyl species Ph [PN3]Ti(Bn) is prone to thermal elimination of toluene, which results in the formation of a cyclometalated species. These findings are discussed in context with the very few group 4 trisamidophosphine complexes that have been reported earlier.

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Chart 1. C3-Symmetric Trisamidophosphine Complexes Sorted by the Length of Their N−Cn−P Linkage (n = 1−3)a

INTRODUCTION Trisamidophosphines are trisanionic ligand systems containing three commonly identical amido functionalities and a single phosphine moiety, which serves as a central linker.1 This definition does not specify whether such a trisamidophosphine coordinates in a tri- or tetradentate fashion, i.e. if the phosphine acts as an additional donor or a spectator,2 considering that both cases are known in the literature.3−5 The very first trisamidophosphine complexes, which have been prepared by Johnson et al. in 2006,3 comprise short methylene linkages between phosphorus and the three amides and serve as examples for a tridentate coordination (see Chart 1, system A). In these so-called exo-configured complexes, the phosphine’s lone pair points away from the metal, apparently for geometric reasons.3f The phenylene-linked system B has been studied as well and a similar exo configuration was found in case of the titanium(IV) complex [phenylene-PN3]TiCl (cf. Chart 1; for details see the Supporting Information).2a At first glance this finding might be rather surprising, as similar phenylene-linked [NN3] or [PS3] ligands are actually tetradentate.4 For the ethylene-linked trisamidophosphine ligand (phospha-tren, system C), no coordination compounds are known, although the Me3Si-substituted derivative of this ligand has been prepared by Schrock and co-workers (vide infra).5 Very recently, we have obtained the o-tolylene- and the benzylenelinked ligands D and E (see Chart 1) and demonstrated that these ligands coordinate in a tetradentate fashion (endo-P configuration).6 Taking these observations together, one might hypothesize that the configuration of the central phosphine is © XXXX American Chemical Society

a

The dashed line in system C is meant to indicate that the phosphine’s configuration (exo vs endo) is unclear.

dependent on the length and flexibility of the N−Cn−P linkage (n = 1−3). To test this hypothesis, we set out to synthesize the so far unknown propylene-linked system F (see Chart 1) and study its coordination chemistry. The most important question to be clarified here is if ligand F supports the tetradentate coordination mode that is implied in Chart1 and observed for D and E and the closely related propylene-linked trisamidoamine complexes.7 In this context, it seemed appropriate to Received: January 22, 2015

A

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Organometallics Scheme 1. Synthesis of N,N′,N″-Triphenylphospha-tren P(CH2CH2NHPh)3 (3)

Scheme 2. Synthesis of Phospha-trpn Derivatives (8a−e)

P(CH2CH2NHSiMe3)3 were observed, as judged by 31P{1H} NMR spectroscopy. Assuming that Schrock made similar observations,5 we excluded the possibility that our failure is due to inappropriate experimental conditions and hypothesized that the inaccessibility of well-defined complexes is either due to an unusual coordination of the ligand (e.g., formation of oligomers and polymers by reaction of more than one metal per ligand or nucleation via an exposed exo-configured phosphine donor) or due to cleavage of the silylamides. In order to test the latter assumption, a N,N′,N″-trisalkyl- or N,N′,N″-trisaryl-substituted derivative of phospha-tren was required. As selective Nalkylations, N-acylations, and N-arylations of the parent P(CH2CH2NH2)3 were unsuccessful due to competitive transformations at the phosphorus atom, a strategy that involves introduction of the amino substituent prior to the phosphine was developed. Gratifyingly, the N,N′,N″-triphenylsubstituted system P(CH2CH2NHPh)3 could be obtained via the synthetic pathway shown in Scheme 1. Starting from the trimethylsilyl-protected N-phenyl(2-chloroethyl)amine 1,11 the primary phosphine 2 was prepared and isolated by distillation. Stepwise deprotonation of the primary phosphine and reaction with additional 1, followed by removal of the trimethylsilyl protective groups by treatment with methanol, results in the formation of crude P(CH2CH2NHPh)3 (3), which was isolated as a yellow oil. In lieu of a convenient workup procedure, crude 3 was BH3 protected at its phosphine moiety, purified by column chromatography, and subsequently deprotected, leading to 3 in a pure form. In numerous attempts, we once again failed to isolate well-defined metal complexes of 3.12 In comparison to P(CH2CH2NHSiMe3)3, bond cleavage reactions are rather unlikely in ligand 3, which supports the hypothesis that phospha-tren tends to form more complicated aggregates rather than simple monomeric complexes. However, drawing definite conclusions from failed experiments is inappropriate in general, which allows for only one conclusion at this end, namely that the coordination chemistry of phospha-tren and its derivatives still remains mysterious.

examine the effect of different amido substituents on ligand F and (re)evaluate if complexes of phospha-tren (system C) are indeed inaccessible. Our findings discussed below are meant to contribute to a more comprehensive understanding of trisamidophosphines as a rather unique class of new ligands.

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RESULTS AND DISCUSSION Phospha-tren and Derivatives. To the best of our knowledge, the idea that phospha-tren (cf. structure C in Chart 1) might display a useful variant of the long-known tren ligand was first mentioned by Schrock in 1997.8 In this context, however, it was stated as well that the synthesis of phospha-tren is expected to be rather challenging. In the following years, theoretical chemists analyzed Schrock’s proposal by means of DFT calculations and arrived at the conclusion that hypothetical phospha-tren-coordinated molybdenum or osmium complexes might indeed perform well in catalytic dinitrogen reduction processes.9 In both of these studies (Mo and Os), a tetradentate coordination of phospha-tren, similar to that of the parent tren complexes,8 was assumed. In 2009, however, a theoretical analysis on silicon complexes of phospha-tren revealed that sila-cages of this ligand are expected to be exo configured.10 Thus, it remained somewhat unclear if phosphatren would act as a tri- or tetradentate ligand or if both denticities were equally possible in reality. Therefore, we started our efforts to prepare phospha-tren and explore its coordination chemistry in early 2011. At that time, we were unaware of the fact that Schrock had achieved the ligand’s synthesis already several years before us. When we first took note of the Ph.D. thesis from Schrock’s group that describes the synthesis of phospha-tren,5 we already had prepared the parent ligand as well as N,N′,N″-tris(trimethylsilyl)-substituted derivative P(CH2CH2NHSiMe3)3 independently and started to explore the coordination chemistry of the latter trimethylsilyl-substituted derivative, employing group 4 metals (for details see the Supporting Information). Despite persistent efforts over the course of more than one year, no clean reactions of B

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Organometallics Unable to solve the “phospha-tren puzzle”, we decided to turn our attention to the propylene-linked derivative phosphatrpn, not knowing what we actually had to expect from this ligand. On one hand, one might assume that the more flexible propylene side arms disfavor the formation of monomeric complexes to an even higher extent. On the other hand, we have shown previously that related C3-linked trisamidophosphines (cf. systems D and E in Chart 1) are well-suited to coordinate to group 4 metals in a tetradentate manner.6 Phospha-trpn and Derivatives. P(CH2CH2CH2NH2)3 (phospha-trpn) was first observed in 1952, when it was identified as one of the products that form upon irradiating mixtures of allylamine and PH3.13 At that time, however, only traces of the molecule were isolated. In 1973, a second report on phospha-trpn appeared and it was claimed that the target molecule can be obtained by reduction of tris(2-cyanoethyl)phosphine.14 In our laboratory, this patented procedure resulted in the formation of complex mixtures with only minor amounts of phospha-trpn present (as determined by 31 1 P{ H} NMR spectroscopy). Thus, we decided to develop an independent synthetic route to phospha-trpn and its derivatives, which employs the primary phosphines 4 as key intermediates (see Scheme 2). In case of R = H, tBu, iPr, the required primary phosphines 4a−c are easily synthesized starting from diethyl 3bromopropylphosphonate 5.15 The synthetic route to parent 3aminopropylphosphine (4a, R = H) via reduction of diethyl 3azidopropylphosphonate (6) has been reported earlier,16 and both alkyl-substituted phosphines RHN(CH2)3PH2 (4a, R = t Bu; 4b, R = iPr) have been obtained following a similar strategy: i.e., via LiAlH4 reduction of the corresponding phosphonates. In case of the N-phenyl-substituted intermediate 4d (R = Ph), this procedure failed and the target molecule was obtained via reaction of excess aniline with 3-bromopropylphosphine (7), which is readily prepared via reduction of 5.17 With all the differently substituted primary phosphines in hand, the targeted phospha-trpn ligands 8a−d were prepared in good yields by radical hydrophosphination18 using an excess of the respective allylamines and catalytic amounts of AIBN as an initiator (see Scheme 2). The N-silylated derivative 8e (R = SitBuMe2) was then prepared by treatment of 8a with t BuMe2SiCl in the presence of triethylamine. Thus, four potentially suitable ligands (8b−e) with different amino substituents (R = tBu, iPr, tBuMe2Si, Ph) were made available and had to be studied with respect to their coordination chemistry with group 4 metals. Complex Synthesis. Three of these ligands, namely both alkyl-substituted variants (8b,c) and the tert-butyldimethylsilylsubstituted ligand (8e), failed to react cleanly with various group 4 precursors.19 However, the N-phenyl derivative 8d (Ph[PN3]H3) reacts in a productive manner with tetrakis(dimethylamido)zirconium to afford a well-defined complex, although elevated temperatures (130 °C) and relatively long reaction times (48 h) are needed to ensure complete conversion (see Scheme 3). As in all other cases, this transformation is conveniently monitored by 31P{1H} NMR spectroscopy, as the signal of the free ligand 8d at −32.3 ppm disappears while a new signal of the zirconium complex at −37.3 ppm builds up over time. From the 1H and 13C NMR spectra of the isolated complex (9-Zr), it is evident that a single dimethylamido substituent remained at zirconium and that the C3 symmetry of the ligand is retained, which implies free rotation of the dimethylamido substituent at room temperature.

Scheme 3. Synthesis of Complexes 9-M (M = Ti, Zr, Hf) Starting from Ph[PN3]H3 (8d)

The homologous hafnium complex Ph[PN3]Hf(NMe2) (9Hf) is readily obtained in just the same way (see Scheme 3), i.e. starting from Ph[PN3]H3 (8d) and tetrakis(dimethylamido)hafnium, and both dimethylamido complexes are easily converted to the respective chlorides Ph[PN3]M(Cl) (M = Zr, Hf) by reaction with trimethylsilyl chloride (see the Supporting Information). The resulting chlorides, however, are sparingly soluble only in dichloromethane and virtually insoluble in other common organic solvents, which hampers further transformations. This is not the case for the corresponding triflates Ph [PN3]M(OTf) (M = Zr, Hf; 10-M), which can be obtained for both metals starting from 9-M (M = Zr, Hf) and triethylsilyl trifluoromethanesulfonate (see Scheme 4). Proton and 13C Scheme 4. Synthesis of Complexes 10-M and 11-M (M = Ti, Zr, Hf) nd 12

NMR data again suggest that both complexes 10-M (M = Zr, Hf) are C3 symmetric in solution, while their 31P{1H} NMR spectra exhibit rather uninformative singlet resonances at −17.0 ppm (10-Zr) and −7.6 ppm (2-Hf), respectively.20 In the case of titanium, several products are formed upon reaction of 8d with tetrakis(dimethylamido)titanium, while other precursors such as TiBn421 decompose prior to reaction with the protio ligand. The chloro precursors (Me2N)3TiCl22 and Bn3TiCl23 react with 8d but form insoluble materials. To overcome this problem, we synthesized the previously unknown titanium precursor (Me2N)3Ti(OTf) by treatment of Ti(NMe2)4 with 1 equiv of triethylsilyl trifluoromethanesulfonate. Subsequent reaction of 8d with (Me2N)3Ti(OTf) in Et2O at room temperature results in the formation of a green precipitate, which contains the desired Ph[PN3]Ti(OTf) according to 31P{1H} NMR spectroscopy (δ(31P{1H}) 6.2 C

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Organometallics ppm). However, proton, carbon, and fluorine NMR revealed that (Me2N)2Ti(OTf)2 was present as well, although it remains unknown how this material had formed. The use of other solvents and ratios of the employed starting materials results in lower conversions and does not prevent the formation of (Me2N)2Ti(OTf)2. As both products are not easily separated by fractional crystallization, the crude mixture of Ph[PN3]Ti(OTf) and (Me2N)2Ti(OTf)2 was treated with an excess of lithium dimethylamide, which results in the formation of Ph [PN3]Ti(NMe2) (9-Ti) and Ti(NMe2)4 (see Scheme 3). Unreacted LiNMe2 is insoluble in toluene and is easily removed by filtration, while liquid Ti(NMe2)4 is readily removed by pentane extraction, leaving the desired Ph[PN3]Ti(NMe2) (9Ti) behind, which was isolated that way, albeit in low yields of 38%. Once isolated in a pure form, red Ph[PN3]Ti(NMe2) (9Ti, δ(31P{1H}) −30.7 ppm) is easily converted into dark green Ph [PN3]Ti(OTf) (10-Ti, δ(31P{1H}) 6.2 ppm) by reaction with 1 equiv of Et3SiOTf (see Scheme 4). Both complexes 9-Ti and 10-Ti are C3 symmetric in solution, as only one set of signals is observed for the three N-phenyl and the three n-propylene units. With all the dimethylamido and trifluoromethanesulfonato complexes Ph[PN3]M(X) (9-M, 10-M; M = Ti, Zr, Hf; X = NMe2, OTf) available, the actual question regarding the denticity of ligand 8d was tackled. Whether the apical phosphines in 9-M and 10-M are coordinated (endo configuration) or pointing away from the central metals (exo configuration), however, cannot be extracted from NMR spectroscopy. Thus, single crystals suitable for X-ray diffraction were required and grown in case of 9-Ti and 10-Zr by slow diffusion of pentane into saturated solutions of the complexes in toluene (9-Ti) and THF (10-Zr), respectively. In accordance with the NMR data, X-ray diffraction analysis of 9-Ti and 10-Zr confirmed the expected approximate C3-symmetric half-cage structures (see Figure 1). In both cases, the coordination polyhedra around the metals are best described as trigonal bipyramidal, with the three amido donors occupying the equatorial positions. The configurations at the phosphorus atoms are revealed to be endo with a Ti−P distance of 2.624 Å and a Zr1−P1 distance of 2.66 Å. The Neq−M bond lengths and Neq−M−Neq angles (Neq = equatorial nitrogen atoms) are unexceptional, as are the former metal−phosphorus distances, which are in the range of those for comparable amidophosphine complexes.6 The dimethylamido substituent in 9-Ti and the trifluoromethanesulfonato substituent in 10-Zr are found in apical positions, completing the trigonal-bipyramidal coordination spheres. These monodentate ligands are located in trans positions with respect to the coordinated phosphine donors and, in the case of 9-Ti, are slightly bent with respect to the principal axes (N4−Ti−P = 166°, O1−Zr1−P1 ≈ 178°). It is proposed that the phosphines in 9-M and 10-M are coordinated to the central metals not only in the solid state but also in solution. This assumption is supported by the 31P{1H} NMR chemical shifts, which are found in the range of −30.7 to −37.3 ppm for the dimethylamido complexes 9-M and in the range of +6.2 to −17.0 ppm for the trifluoromethanesulfonato complexes 10-M. Thus, the 31P{1H} NMR resonances of the triflates 10-M are shifted downfield in comparison to the resonances for the dimethylamides 9-M, which has to be expected for phosphorus nuclei bound to the more electropositive metals present in 10-M.23 With Ph[PN3]M(OTf) (10-M, M = Ti, Zr, Hf) as the starting materials, the benzyl complexes Ph[PN3]M(Bn) (11-M, M = Ti,

Figure 1. ORTEP plots of the molecular structures of 9-Ti (top), and 10-Zr (bottom). For 10-Zr only one of the two independent molecules is shown. Disordered parts and hydrogen atoms are omitted for clarity; thermal ellipsoids are set at 50% probability. Selected bond lengths (Å) and angles (deg) for 9-Ti: Ti−P 2.6242(4), Ti−N1 1.9592(11), Ti−N2 2.0601(11), Ti−N3 1.9862(12), Ti−N4 1.9239(11), N4−Ti−P 165.95(4), N1−Ti−N2 122.69(5), N1−Ti− N3 103.86(5), N3−Ti−N2 127.38(5). Selected bond lengths (Å) and angles (deg) for one of the two independent molecules of 10-Zr (values for the second molecule with the disordered ligand backbone are similar but are less meaningful due to the applied restraints): Zr1− P1 2.6572(16), Zr1−N1 2.088(6), Zr1−N2 2.080(5), Zr1−N3 2.064(5), Zr1−O1 2.184(5), O1−Zr1−P1 178.39(15), N2−Zr1−N1 119.0(2), N3−Zr1−N2 118.5(2).

Zr, Hf) were prepared by reaction with Bn2Mg(THF)224 and isolated in moderate yields of 22−48% (see Scheme 4). As this conversion replaces the triflates with electron-donating benzyl ligands, the 31P{1H} NMR resonances of the individual products are shifted upfield (−33.7 to −40.2 ppm) and found in a range close to that for the dimethylamido complexes. At room temperature, free rotation of the benzyl ligand is assumed, as 1H and 13C NMR spectra indicate that complexes 11-M are C3 symmetric in solution. In the proton NMR spectra, the benzylic CH2 groups are found at 3.44 ppm (11Ti), 3.04 ppm (11-Zr), and 2.81 ppm (11-Hf) and a coupling to the 31P nucleus is noticed in the corresponding 13C{1H} NMR and 1H−31P HMBC NMR spectra. Therefore, complexes 11-M have the endo configuration in solution. Attempts to hydrogenate complexes 11-M under H2 pressure (10 bar) failed at room temperature, as no reaction to the desired terminal hydrido complexes was detectable in the individual 31P NMR spectra. At elevated temperatures (70 °C), decomposition was observed in the case of the zirconium and hafnium complex, while a new species at δ(31P{1H}) +50.7 ppm formed in the case of titanium. This species, however, originates from thermal elimination of toluene (identified by proton NMR spectroscopy) and proceeds equally well in the absence of dihydrogen gas. D

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CONCLUSION In summary, we have synthesized several new members of the trisamidophopshine ligand family, namely N,N′,N″-triphenylphospha-tren 3, parent phospha-trpn 8a, and four N,N′,N″trisubstituted derivatives of the latter framework. Despite extensive efforts to access coordination compounds of all these systems, only N,N′,N″-triphenylphospha-trpn, P(CH2CH2CH2NHPh)3 (8d), allowed for the preparation of closed half-cage complexes of the group 4 metals. It was shown that the dimethylamido, triflato, and benzyl complexes (9-M− 11-M) of the general formula Ph[PN3]M(X) (M = Ti, Zr, Hf; X = NMe2, OTf, Bn) can be prepared in the case of ligand 8d and that this particular ligand supports a tetradentate coordination mode with the phosphine bound to the central metal. In case of titanium, the benzyl species Ph[PN3]Ti(Bn) (11-Ti) is prone to thermally induced elimination of toluene, resulting in the formation of the metallaziridine species 12. In conjunction with previous studies on trisamidophosphine complexes, the presented results point to the presence of some common design principles and common reactivity patterns among the family of trisamidophosphine complexes.

On the basis of careful NMR analysis, the resulting new species was identified as the cyclometalated species 12 shown in Scheme 4.25 In the 1H NMR spectrum of 12, all resonances assigned to the titanium-bound benzyl ligand disappeared and the C3 symmetry of the starting material was lost during the reaction. In the aromatic region, signals for overall 15 protons are found, indicating that all the N-phenyl substituents remained unchanged. The N−CH2 groups of the three propylene linkers, however, integrate for only five protons, with one of the protons appearing as a 31P-coupled resonance at δ 2.97 ppm (overlapping with one proton of an adjacent CH2 group, assignment ascertained by 1H{31P}, 1H−31P HMBC, and two-dimensional NMR spectra). On the basis of HSQC NMR spectroscopy, this proton resonance is correlated to a 13C NMR signal at δ 89.8 ppm, which appears as a 31P-coupled doublet and corresponds to a CH resonance (according to DEPT NMR analysis). Thus, it is clear that one N−CH2 proton was lost and that the remaining CH group is within the coupling range of the 31P nucleus. The conclusion that the latter CH group is bound to titanium agrees well with the observed downfield shift of the corresponding 13C resonance. Comparison of Trisamidophosphine Complexes. Out of the six different trisamidophosphine scaffolds that are known so far (systems A−F, Chart 1), only the C3-linked systems D−F seem to support a tetradentate coordination mode, while ligands A−C seem to favor tridentate or more complicated coordination modes, which are still obscure in the case of system C. However, it is not only the linkage between the phosphine and the three amides that controls the coordination geometry but also the nature of the amido substituents. Thus, only the N,N′,N″-triphenyl derivative of the propylene-linked ligand F (i.e., ligand 8d) was found to coordinate to group 4 metals via all four donor sites. A closer inspection of systems D−F reveals that the presence of anilides might very well display a basic necessity for the construction of trisamidophosphine complexes, as all the trisaminophosphine scaffolds that so far have led to isolable complexes actually contain aryl amines (including the exo-configured systems A and B). With respect to the trisamidophosphine-coordinated group 4 alkyl species of ligands D−F another similarity is noticeable, namely that only the titanium derivatives tend to form cyclometalated species, while their heavier homologues decompose upon heating. However, the position of the CH bond that suffers from deprotonation cannot be predicted easily (see Chart 2). Nevertheless, this brief summary on the observed similarities between the different trisamidophosphine scaffolds might be of use in the design of new NP ligands and complexes, especially if cyclometalated species are desired or to be avoided.

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EXPERIMENTAL SECTION

General Considerations. All manipulations were performed under an atmosphere of dry and oxygen-free argon by means of standard Schlenk or glovebox techniques. Toluene, THF, pentanes, hexanes, and diethyl ether were purified by passing the solvents over activated alumina columns (MBraun Solvent Purification System). Tetragylme and DME were dried over sodium benzophenone ketyl, methanol over magnesium tunings, and methylene chloride over CaH2 and distilled prior to use. Toluene-d8, THF-d8, and benzene-d6 were refluxed over sodium and purified by distillation. DMSO-d6 and CD2Cl2 were dried over CaH2 and purified by distillation. NMR spectra were recorded on a Bruker Avance II 400 MHz or a Bruker Avance III 600 MHz spectrometer at room temperature. 1H and 13C NMR spectra were referenced to residual proton signals of the lock solvent. 31P and 19F NMR spectra were referenced to external H3PO4 and CCl3F, respectively. Mass spectra were acquired on Bruker ApexQe hybrid 9.4 T FT-ICR (HR-ESI) and JEOL JMS-700 magnetic sector (HR-EI) spectrometers at the mass spectrometry facility of the Institute of Organic Chemistry of the University of Heidelberg. Microanalyses (C, H, N) were performed at the Department of Chemistry at the University of Heidelberg. Sodium phosphide,26 N-(2chloroethyl)-N-(trimethylsilyl)aniline (1),11 3-aminopropylphosphine (4a),16 diethyl 3-bromopropylphosphonate (5),15 diethyl 3-azidopropylphosphonate (6),16 3-bromopropylphosphine (7),17 N-allylaniline,27 and Bn2Mg(THF)224 were synthesized according to the literature. Substituted allylamines (N-(tert-butyl)allylamine, N(isopropyl)allylamine) were prepared by modified literature procedures (see the Supporting Information).28 Allylamine, aniline, di- and triethylamine, tert-butylamine, and isopropylamine were dried over CaH2 and distilled prior to use. All other chemicals were purchased from commercial suppliers and used without further purification. N-(2-Phosphanylethyl)-N-(trimethylsilyl)aniline (2). A vigorously stirred suspension of sodium phosphide (3.15 g, 56.0 mmol, 1.0 equiv) in DME (125 mL) was cooled to −78 °C and a solution of N(2-chloroethyl)-N-(trimethylsilyl)aniline (1; 12.6 g, 56.0 mmol, 1.0 equiv) in DME (50 mL) added dropwise over a period of 30 min. After addition was complete, stirring was continued at −78 °C for 30 min, the cooling bath was then removed, and stirring was continued for 12 h at room temperature. The resulting pale yellow suspension was heated to 60 °C for 3 h and cooled to room temperature. All volatiles were removed under vacuum, and the light brown residue was taken up in pentane (200 mL). This suspension was filtered over Celite, and the Celite pad was washed with pentane (2 × 50 mL). The combined pentane extracts were condensed to dryness, and the oily yellow residue was fractionally distilled under vacuum (5 × 10−1 mbar,

Chart 2. Cyclometalated Titanium Trisamidophosphine Complexesa

a

Anilide substructures within the individual trisamidophosphines are highlighted in blue (Xyl = 3,5-xylyl). E

DOI: 10.1021/acs.organomet.5b00065 Organometallics XXXX, XXX, XXX−XXX

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Organometallics bp 70−75 °C) to afford the product as a colorless liquid (5.22 g, 23.0 mmol, 41%). 1H NMR (400 MHz, C6D6): δ [ppm] 7.13 (t, 3JH,H = 7.7 Hz, m-Ph, 2 H), 6.90−6.84 (overlapping signals, o-Ph and p-Ph, 3 H), 3.23−3.18 (m, NCH2, 2 H), 2.46 (dm, 1JP,H = 192 Hz, PH2, 2 H), 1.45−1.34 (m, PCH2, 2 H), 0.11 (s, SiMe3, 9 H). 13C{1H} NMR (101 MHz, C6D6): δ [ppm] 148.6 (s, ipso-Ph), 129.2 (s, m-Ph), 123.2 (s, oPh), 121.4 (s, p-Ph), 51.4 (d, 2JP,C = 1.7 Hz, NCH2), 14.9 (d, 1JP,C = 10.9 Hz, PCH2). 31P{1H} NMR (162 MHz, C6D6): δ [ppm] −152.1 (s). MS (EI+): m/z 178.1 ([M − (H2CCHPH2)]+, 100%), 153.1 ([M − (SiMe3)]+, 12%). HR-MS (EI+): observed m/z 178.1044 ([M − (MePH2)]+), 153.0714 ([M − (SiMe3)]+); calcd m/z for C10H16NSi ([M − (MePH2)]+) 178.1050, calcd m/z for C8H12NP ([M − (SiMe3)]+) 153.0707. Tris(2-anilinoethyl)phosphine (3). Neat N-(2-chloroethyl)-N(trimethylsilyl)aniline (1; 1.48 g, 6.50 mmol, 1.0 equiv) was added to a solution of N-(2-phosphanylethyl)-N-(trimethylsilyl)aniline (2; 1.46 g, 6.50 mmol, 1.0 equiv) in diethyl ether (100 mL), and the resulting mixture was cooled to −78 °C. A solution of nBuLi (2.5 M in hexanes, 2.86 mL, 7.14 mmol, 1.1 equiv) was added dropwise, and the reaction mixture was stirred for 10 min at −78 °C. The cooling bath was then removed, and the mixture was stirred for 3 h while it was warmed to room temperature. The turbid pale yellow solution was cooled to −78 °C, and a solution of N-(2-chloroethyl)-N-(trimethylsilyl)aniline (1; 1.62 g, 7.14 mmol, 1.1 equiv) in diethyl ether (25 mL) was added slowly. A solution of nBuLi (2.5 M in hexanes, 2.86 mL, 7.14 mmol, 1.1 equiv) was added dropwise, and the reaction mixture was warmed to room temperature overnight. All volatiles were removed under vacuum, and the residue containing the N,N′,N″-tris(trimethylsilyl)protected ligand (δ(31P{1H} −52.2 ppm) was dissolved in methanol (30 mL). This mixture was stirred at 60 °C for 2 h, cooled to room temperature, and condensed under vacuum. The residual thick yellow oil was extracted with toluene (50 mL) and filtered over Celite, and the solvent once again was removed under vacuum. Subsequently, residual amounts of primary and secondary phosphines were distilled off (2 × 10−2 mbar, 200 °C), and the crude product (1.5 g, ∼3.8 mmol) was obtained in approximately 85% purity as a viscous dark orange oil. Further purification was achieved by BH3 protection, column chromatography, and subsequent deprotection, as detailed in the following: to a solution of crude tris(2-anilinoethyl)phosphine (1.5 g, ∼3.8 mmol) in THF (50 mL) was slowly added a solution of (THF)·BH3 (1.0 M in THF, 4.50 mL, 4.50 mmol) at 0 °C, and the resulting mixture was stirred for 20 min at room temperature. In air, all volatiles were removed using a rotary evaporator and the residue subjected to column chromatography over silica gel (Rf = 0.15 using dichloromethane/hexanes =3/1 as eluent) to afford the BH3-protected product as a colorless oil (1.1 g, 2.7 mmol, 41% based on 2). 1H NMR (600 MHz, C6D6): δ [ppm] 7.18 (dd, 3JH,H = 7.8 Hz, 3JH,H =7.3 Hz, mPh, 6 H), 6.75 (t, 3JH,H = 7.3 Hz, p-Ph, 3 H), 6.54 (d, 3JH,H = 7.8 Hz, oPh, 6 H), 3.88 (broad s, NH, 3 H) 3.45 (m, NCH2, 6 H), 2.01 (m, PCH2, 6 H), 0.8−0.2 (broad m, BH3, 3 H). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] 11.8 (broad m, R3P·BH3). This material was transferred to a Teflon-valved ampule and degassed prior to addition of diethylamine (40 mL). The ampule was sealed, heated to 60 °C for 4 h, and cooled to room temperature. The reaction mixture was condensed to dryness and (Et2NH)·BH3 removed by gently heating the residue under vacuum. The product was obtained as a colorless oil (1.0 g, 2.6 mmol, 40% based on 2). 1H NMR (600 MHz, C6D6): δ [ppm] 7.19 (dd, 3JH,H = 8.0 Hz, 3JH,H =7.3 Hz, m-Ph, 6 H), 6.79 (t, 3 JH,H = 7.3 Hz, p-Ph, 3 H), 6.48 (d, 3JH,H = 8.0, o-Ph, 6 H), 3.32 (unresolved broad triplet, NH, 3 H), 2.97 (m, NCH2, 6 H), 1.35 (t, 3 JH,H = 7.4 Hz, PCH2, 6 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 148.3 (s, ipso-Ph), 129.7 (s, m-Ph), 118.0 (s, p-Ph), 113.3 (s, oPh), 41.3 (d, 2JC,P = 18.3 Hz, NCH2), 27.8 (d, 1JC,P = 14.0 Hz, PCH2). 31 P NMR (243 MHz, C6D6): δ [ppm] −43.8 (sept, 2JP,H = 8.7 Hz). 31 1 P{ H} NMR (243 MHz, C6D6): δ [ppm] −43.8 (s). MS (EI+): m/z 391.3 (M+, 31%), 272.2 ([M − (PhNHCHCH2)]+, 100%). HR-MS (EI+): observed m/z 391.2171; calcd m/z for C24H30N3P 391.2177. N-(tert-Butyl)(3-phosphanylpropyl)amine (4b). Neat diethyl 3bromopropylphosphonate (5; 15.0 g, 57.9 mmol, 1.0 equiv) was slowly

added to ice-cooled neat tert-butylamine (53.0 g, 75.0 mL, 0.73 mol 12.5 equiv), and stirring was maintained at 0 °C for 1 h. The reaction mixture was warmed to room temperature and stirred overnight. Due to the low boiling point of tert-butylamine (46 °C), the use of a reflux condenser is strongly recommended, although the reaction is only slightly exothermic. The obtained white suspension was reduced in volume, diluted with hexanes (150 mL), and filtered to remove tertbutylammonium bromide. The latter hydrobromide salt was extracted with hexanes (2 × 60 mL), and the combined filtrates were condensed under vacuum. The residual turbid oil was distilled under vacuum (5 × 10−2 mbar, bp 85−90 °C) to afford diethyl [3-(tert-butylamino)propyl]phosphonate as a colorless clear liquid (11.0 g, 43.8 mmol, 75%), which was used in the next step without further purification. 1H NMR (400 MHz, CDCl3): δ [ppm] 3.99 (dt, 3JH,H = 7.2 Hz, 3JP,H = 5.7 Hz, OCH2, 4 H), 2.51 (t, 3JH,H = 6.8 Hz, NCH2, 2 H), 1.60−1.75 (m, CH2 and PCH2, 4 H), 1.22 (t, 3JH,H = 7.1 Hz, OEt(CH3), 6 H), 0.98 (s, tBu, 9 H), 0.71 (broad s, NH, 1 H). 13C{1H} NMR (101 MHz, CDCl3): δ [ppm] 61.5 (d, 2JC,P = 6.5 Hz, OCH2), 57.2 (s, tBu(Cquat)), 43.1 (s, NCH2), 33.4 (s, tBu(CH3)), 25.8 (d, 1JC,P = 4.3 Hz, PCH2) 23.5 (s, CH2), 16.25 (d, 3JC,P = 6.0 Hz, OEt(CH3)). 31P{1H} NMR (162 MHz, CDCl3): δ [ppm] 32.3 (s). MS (ESI+, EtOH): m/z 252.1 ([M + H]+, 100%). To a stirred suspension of lithium aluminum hydride (2.40 g, 63.1 mmol, 1.75 equiv) in diethyl ether (150 mL) maintained at 0 °C was added a solution of diethyl [3-(tertbutylamino)propyl]phosphonate (9.00 g, 35.8 mmol, 1.0 equiv) in diethyl ether (40 mL) dropwise, and stirring was continued at room temperature for 5 h. The resulting reaction mixture was cooled to 0 °C and carefully quenched by addition of a saturated solution of sodium chloride in degassed water (20 mL). The white precipitate was allowed to settle and the supernatant filtered off via cannula and dried over sodium sulfate. After filtration, diethyl ether was removed under reduced pressure (700 mbar) and the residue distilled under vacuum (25 mbar, bp 75−80 °C) to afford the product as a colorless malodorous liquid (5.0 gr, 34 mmol, 95%). 1H NMR (400 MHz, C6D6): δ [ppm] 2.65 (dt,1JP,H = 188 Hz, 3JH,H = 8.0 Hz, PH2, 2 H), 2.34 (t, 3JH,H = 6.7 Hz, NCH2, 2 H), 1.56−1.35 (m, CH2, 2 H), 1.33− 1.27 (m, PCH2, 2 H), 0.97 (s, tBu, 9 H), 0.6 to −0.3 (broad s, NH, 1 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 45.0 (s, tBu(Cquat)), 43.0 (d, 3JC,P = 6.1 Hz, NCH2), 34.8 (d, 2JC,P = 3.6 Hz, CH2), 29.30 (s, t Bu(CH3)), 11.8 (d, 1JC,P = 8.1 Hz, PCH2). 31P NMR (162 MHz, C6D6): δ [ppm] −138.2 (t, 1JP,H = 188 Hz). 31P{1H} NMR (162 MHz, C6D6): δ [ppm] −138.2 (s). MS (ESI+, MeOH): m/z 148.0 ([M + H]+, 100%). HR-MS (EI+): observed m/z 147.1172; calcd m/z for C7H18NP 147.1177. N-(Isopropyl)(3-phosphanylpropyl)amine (4c). Neat diethyl 3bromopropylphosphonate (5; 13.5 g, 52 mmol, 1.0 equiv) was slowly added to ice-cooled neat isopropylamine (50 mL, 34.5 g, 0.59 mol, 11.5 equiv), and stirring was maintained at 0 °C for 1 h. The reaction mixture was warmed to room temperature and refluxed overnight. Subsequently, excess isopropylamine was removed under vacuum, and the residue was taken up in dichloromethane (100 mL) and cooled to 0 °C. A cold solution of sodium hydroxide (22 g, 55 mmol) in water (100 mL) was then added, and the mixture was stirred vigorously for 1 h. The organic phase was separated, washed with water (3 × 50 mL), and dried over sodium sulfate. After filtration, the solvent was removed under vacuum and diethyl [3-(isopropylamino)propyl]phosphonate isolated via trap-to-trap distillation (5 × 10−2 mbar, T(oil bath) = 120 °C). The obtained colorless liquid (8.60 g, 36.4 mmol, 72%) was used in the next step without further purification. 1H NMR (400 MHz, C6D6): δ [ppm] 4.11−3.79 (m, OCH2, 4 H), 2.55 (sept, 3JH,H = 6.2 Hz, iPr(CH), 1 H), 2.41 (t, 3JH,H = 6.2 Hz, NCH2, 2 H), 1.84−1.57 (m, CH2 and PCH2, 4 H), 1.05 (t, 3JH,H = 7.1 Hz, OEt(CH3), 6 H), 0.90 (d, 3JH,H = 6.2 Hz, iPr(CH3), 6 H) 0.5 (broad s, NH, 1 H). 13 C{1H} NMR (101 MHz, C6D6): δ [ppm] 61.0 (d, 2JC,P = 6.3 Hz, OCH2), 48.8 (s, iPr(CH)), 47.7 (s, NCH2), 24.1 (d, 1JC,P = 4.7 Hz, PCH2), 23.5 (s, CH2), 23.3 (s, iPr(CH3)), 16.6 (d, 3JC,P = 5.7 Hz, OEt(CH3)). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] 32.1 (s). MS (ESI+, EtOH): m/z 238.3 ([M − OEt]+, 100%). To a stirred suspension of lithium aluminum hydride (1.20 g, 31.6 mmol, 1.8 equiv) in diethyl ether (50 mL) maintained at 0 °C was added a F

DOI: 10.1021/acs.organomet.5b00065 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

mmol, 78%). 1H NMR (600 MHz, C6D6): δ [ppm] 2.54 (t, 3JH,H = 6.7 Hz, NCH2, 6 H), 1.66−1.56 (m, CH2, 6 H), 1.48−1.44 (m, PCH2, 6 H), 1.02 (s, tBu, 27 H), 0.33 (s, NH, 3 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 50.0 (s, tBu(Cquat)), 44.2 (d, 3JC,P = 11.4 Hz, NCH2), 29.4 (s, tBu(CH3)), 28.3 (d, 2JC,P = 13.3 Hz, CH2), 25.9 (d, 1JC,P = 13.9 Hz, PCH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −31.47 (s). MS (ESI+, MeOH): m/z 374.4 ([M + H]+, 100%). HR-MS (ESI+, MeOH): observed m/z 374.36719, calcd m/z for C21H49N3P ([M + H]+) 374.36586. Tris[3-(isopropylamino)propyl]phosphine (8c). A mixture of N-(isopropyl)(3-phosphanylpropyl)amine (4c; 1.2 g, 9.0 mmol, 1.0 equiv), N-(isopropyl)allylamine (7.0 mL, 5.3 g, 54 mmol, 6.0 equiv), and AIBN (50 mg) was heated to 75 °C and stirred at this temperature for 14 h. The reaction mixture was cooled to room temperature, and residual N-(iso-propyl)allylamine was removed under vacuum to afford the product as a colorless oil (2.5 g, 7.7 mmol, 86%). 1H NMR (400 MHz, C6D6): δ [ppm] 2.66 (sept, 3JH,H = 6.3 Hz, iPr(CH), 3 H), 2.57 (t, 3JH,H = 6.9 Hz, NCH2, 6 H), 1.68−1.54 (m, CH2, 6 H), 1.45− 1.38 (m, PCH2, 6 H), 0.98 (d, 3JH,H = 6.3 Hz, 18 H), 0.43 (broad s, NH, 3 H). 13C{1H} NMR (101 MHz, C6D6): δ [ppm] 49.2 (d, 3JC,P = 11.2 Hz, NCH2), 49.0 (s, iPr(CH)), 27.6 (d, 2JC,P = 13.3 Hz, CH2), 25.8 (d, 1JC,P = 13.9 Hz, PCH2), 23.5 (s, iPr(CH3)). 31P NMR (162 MHz, C6D6): δ [ppm] −31.4 (sept, 2JP,H = 7.8 Hz). 31P{1H} NMR (162 MHz, C6D6): δ [ppm] −31.4 (s). MS (ESI+, MeOH): m/z 232.3 ([M + H]+,100%). HR-MS (ESI+, MeOH): observed m/z 332.31904, calcd m/z for C18H43N3P ([M + H]+) 332.31891. Tris(3-anilinopropyl)phosphine (8d). A stirred mixture of N-(3phosphanylpropyl)aniline (4d; 2.20 g, 13.2 mmol, 1.0 equiv), N(allyl)aniline (14.0 mL, 13.7 g, 103 mmol, 7.8 equiv), and AIBN (150 mg) was slowly heated to 75 °C and kept at this temperature for 2 h. The temperature was then raised to 90 °C and stirring continued overnight. Excess N-(allyl)aniline was distilled off under vacuum, and the reaction mixture was kept at 90 °C. In order to remove minor traces of N-(allyl)aniline as well, a short-path vacuum-distillation apparatus was used and the flask briefly (15 min) heated to 160 °C toward the end of the distillation. The crude product, which can be used for complex preparation without further purification, remained as a light yellow viscous oil (5.42 g, 12.5 mmol, 95%). Minor impurities could be removed by conversion of free amine to the corresponding tris-hydrochloride, which was easily purified by recrystallization. Deprotonation with triethylamine afforded the protio ligand as a colorless oil, with no impurities detectable by NMR spectroscopy: A stirred solution of crude tris(3-anilinopropyl)phosphine (3.8 g, 9.0 mmol, 1.0 equiv) in toluene (100 mL) was cooled to 0 °C, and a solution of HCl (2.0 M in Et2O, 15 mL, 30 mmol, 3.3 equiv) was added dropwise. The resulting suspension was stirred at 0 °C for 2 h, and the white precipitate was isolated by filtration. The solid was washed with toluene (40 mL) and diethyl ether (40 mL) and consecutively dried under vacuum. The obtained white powder was dissolved in dichloromethane (50 mL) and cooled to −40 °C overnight. The precipitate was isolated, washed with cold dichloromethane (20 mL), and dried under vacuum, affording the trishydrochloride of tris(3-anilinopropyl)phosphine as a colorless solid (4.2 g, 7.7 mmol, 86%). 1H NMR (600 MHz, DMSO-d6): δ [ppm] 12.6−9.4 (broad s, NH, 6 H), 7.40−7.27 (broad s, m-Ph, 6 H), 7.25− 6.90 (broad overlapping m, p-Pn and o-Ph, 12 H), 3.24 (s, NCH2, 6 H), 2.08 and 1.89 (broad overlapping s, CH2 and PCH2, 12 H). 31 1 P{ H} NMR (243 MHz, DMSO-d6): δ [ppm] 12.3 (very broad s). The protio ligand was liberated from the tris-hydrochloride by deprotonation with triethylamine: to a suspension of [P(CH2CH2CH2NH2Ph)3]Cl3 (2.0 g, 3.7 mmol, 1.0 equiv) in dichloromethane (20 mL) was added triethylamine (20 mL, 145 mmol, 39 equiv), and the reaction mixture was stirred at room temperature for 24 h. All volatiles were removed under vacuum, and the residue was taken up in toluene (20 mL) and filtered over Celite. The Celite pad was washed with toluene (10 mL), and the combined filtrates were evaporated under vacuum. The product was obtained as a colorless viscous oil (1.4 g, 3.2 mmol, 87%). 1H NMR (600 MHz, CD2Cl2): δ [ppm] 7.05 (t, 3JH,H = 7.9 Hz, m-Ph, 6 H), 6.57 (t, 3JH,H = 7.3 Hz, pPh, 3 H), 6.50 (d, 3JH,H = 7.9 Hz, o-Ph, 6 H), 3.77 (s, NH, 1 H), 3.07

solution of diethyl [3-(isopropylamino)propyl]phosphonate (4.20 g, 17.7 mmol, 1.0 equiv) in diethyl ether (20 mL) dropwise over a period of 30 min. The reaction mixture was stirred at 0 °C for 1 h and warmed to room temperature, and stirring was continued for 18 h. The resulting reaction mixture was cooled to 0 °C and carefully quenched by addition of a saturated solution of sodium chloride in degassed water (10 mL). The white precipitate was allowed to settle, and the supernatant was filtered off via cannula and dried over sodium sulfate. After filtration, diethyl ether was removed under reduced pressure (700 mbar) and the residue was distilled under vacuum (25 mbar, bp 65−70 °C) to afford the product as a colorless malodorous liquid (1.2 g, 8.9 mmol, 50%). 1H NMR (400 MHz, C6D6): δ [ppm] 2.63 (td, 1JP,H = 190 Hz, 3JH,H = 7.3 Hz, PH2, 2 H), 2.55 (sept, 3JH,H = 6.2 Hz, iPr(CH), 1 H), 2.35 (t, 3JH,H = 6.9 Hz, NCH2, 2 H), 1.46−1.35 (m, CH2, 2 H), 1.33−1.21 (m, PCH2, 2 H), 0.92 (d, 3JH,H = 6.3 Hz, i Pr(CH3), 6 H), 0.7−0.1 (broad s, NH, 1 H). 13C{1H} NMR (101 MHz, C6D6): δ [ppm] 48.9 (s, iPr(CH), 48.0 (d, 3JC,P = 6.0 Hz, NCH2), 34.1 (d, 2JC,P = 3.5 Hz, CH2), 23.4 (s, iPr(CH3)), 11.8 (d, 1JC,P = 8.2 Hz, PCH2). 31P NMR (162 MHz, C6D6): δ [ppm] −138.2 (t, 1 JP,H = 190 Hz). 31P{1H} NMR (162 MHz, C6D6): δ [ppm] −138.2 (s). MS (ESI+, MeOH): m/z 134.1 ([M + H]+, 100%). HR-MS (EI+): observed m/z 133.1036; calcd m/z for C6H16NP 133.1020. N-(3-Phosphanylpropyl)aniline (4d). Neat (3-bromopropyl)phosphine (7; 4.70 g, 30.5 mmol, 1.0 equiv) was added to excess aniline (35.0 mL, 35.7 g, 385 mmol, 12.6 equiv), and the obtained solution was stirred at 95 °C for 2 h, resulting in the precipitation of anilinium hydrobromide. The reaction mixture was cooled to room temperature, diluted with diethyl ether (50 mL), and filtered via cannula. Residual anilinium hydrobromide was then extracted with diethyl ether (2 × 15 mL), and the combined filtrates were evaporated under vacuum. At 50 °C, unreacted aniline was removed under vacuum and the residue fractionally distilled (1 × 10−1 mbar, bp 100 °C) to afford the product (3.80 g, 22.7 mmol, 75%) as a colorless liquid. 1H NMR (600 MHz, Tol-d8): δ [ppm] 7.12 (t, 3JH,H = 7.8 Hz, m-Ph, 2 H), 6.70 (t, 3JH,H = 7.3 Hz, p-Ph, 1 H), 6.37 (d, 3JH,H = 8.0 Hz, o-Ph, 2 H), 2.93 (s, NH, 1 H), 2.70−2.65 (m, NCH2, 2 H), 2.55 (dm, 1 JP,H ≈ 200 Hz, PH2, 2 H), 1.34−1.28 (m, CH2, 2 H), 1.14−1.05 (m, PCH2, 2 H). 13C{1H} NMR (151 MHz, Tol-d8): δ [ppm] 148.6 (s, ipso-Ph), 137.4 (s, m-Ph), 117.4 (s, p-Ph), 112.9 (s, o-Ph), 44.3 (d, 3 JC,P = 6.1 Hz, NCH2), 32.9 (d, 2JC,P = 3.3 Hz, CH2), 11.4 (d, 1JC,P = 8.8 Hz, PCH2). 31P{1H} NMR (243 MHz, Tol-d8): δ [ppm] −137.8 (s). MS (EI+): m/z 167.2 (M+, 22%), 106.1 ([PhNCH2]+ (100%). HR-MS (EI+): observed m/z 167.0860, calcd m/z for C9H14NP 167.0863. Tris(3-aminopropyl)phosphine (8a). A mixture of 3-aminopropylphopsphine (4a; 2.60 mL, 2.43 g, 26.7 mmol, 1.0 equiv), allylamine (14.8 mL, 11.4 g, 200 mmol, 7.5 equiv), and AIBN (350 mg) was heated to 75 °C and refluxed at this temperature for 14 h. The reaction mixture was cooled to room temperature, and all volatiles (excess allylamine and residual 4a) were evaporated under vacuum. High-boiling byproducts (mainly bis(3-aminopropyl)phosphine) were distilled off at 90 °C (2 × 10−2 mbar), and the crude product was obtained as a colorless oil (3.10 g, 14.9 mmol, 56%). 1H NMR (600 MHz, Tol-d8): δ [ppm] 2.55 (t, 3JH,H = 6.8 Hz, NCH2, 6 H), 1.46− 1.37 (m, CH2, 6 H), 1.28−1.22 (m, PCH2, 6 H), 0.53 (broad s, NH, 6 H). 13C{1H} NMR (101 MHz, Tol-d8): δ [ppm] 44.0 (d, 3JC,P = 11.3 Hz, NCH2), 30.6 (d, 2JC,P = 12.8 Hz, CH2), 25.1 (d, 1JC,P = 14.2 Hz, PCH2). 31P{1H} NMR (243 MHz, Tol-d8): δ [ppm] −31.7 (s). MS (ESI+, MeOH): m/z 206.2 ([M + H]+, 100%). HR-MS (ESI+, MeOH): observed m/z 206.17819, calcd m/z for C9H25N3P ([M + H]+) 206.17806. Tris[3-(tert-butylamino)propyl]phosphine (8b). A mixture of N-(tert-butyl)(3-phosphanylpropyl)amine (4b. 4.2 g, 28 mmol, 1.0 equiv), N-(tert-butyl)allylamine (21 mL, 16 g, 0.14 mol, 5.0 equiv), and AIBN (150 mg) was heated to 75 °C and stirred at this temperature for 14 h. The reaction mixture was cooled to room temperature, and excess N-(tert-butyl)allylamine was removed under vacuum. High-boiling byproducts were distilled off at 100 °C (2 × 10−2 mbar), and the product was obtained as a colorless oil (8.2 g, 22 G

DOI: 10.1021/acs.organomet.5b00065 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

stirred at 130 °C for 48 h. All volatiles were removed under vacuum, and the residue was washed with n-pentane (30 mL). The resulting solid was dried under vacuum to afford the product as a yellow powder (2.79 g, 5.0 mmol, 91%). 1H NMR (600 MHz, Tol-d8): δ [ppm] 7.28 (t, 3JH,H = 7.8 Hz, m-Ph, 6 H), 6.84 (d, 3JH,H = 8.1 Hz, o-Ph, 6 H), 6.78 (t, 3JH,H = 7.2 Hz, p-Ph, 3 H), 3.51−3.38 (m, NCH2, 6 H), 3.20 (s, NMe2, 6 H), 1.35−1.20 (m, CH2, 6 H), 0.83−0.77 (m, PCH2, 6 H). 13 C{1H} NMR (151 MHz, Tol-d8): δ [ppm] 153.3 (s, ipso-Ph), 129.7 (s, m-Ph), 117.5 (s, p-Ph), 114.7 (s, o-Ph), 44.9 (d, 3JC,P = 10.2 Hz, NCH2), 43.8 (s, NMe2), 24.0 (d, 1JC,P = 8.4 Hz, PCH2), 23.2 (d, 2JC,P = 3.3 Hz, CH2). 31P{1H} NMR (243 MHz, Tol-d8): δ [ppm] −37.3 (s). Anal. Calcd for C29H39N4PZr: C, 61.56, H, 6.95, N, 9.90; in numerous attempts low values for carbon were obtained (e.g., C, 59.25; H, 6.76; N, 9.52) possibly due to carbide formation. Ph [PN3]Hf(NMe2) (9-Hf). A solution of tetrakis(dimethylamido)hafnium (0.82 g, 2.3 mmol, 1.0 equiv) in toluene (20 mL) was combined with a solution of tris(3-anilinopropyl)phosphine (8d; 0.99 g, 2.3 mmol, 1.0 equiv) in toluene (10 mL), and the resulting pale yellow reaction mixture was stirred at 130 °C for 96 h. After removal of the solvent, the residue was washed with n-pentane (2 × 50 mL) and dried under vacuum to afford the product as a pale yellow powder (0.85 g, 1.3 mmol, 57%). 1H NMR (400 MHz, C6D6): δ [ppm] 7.38− 7.29 (m, m-Ph, 6 H), 6.94 (d, 3JH,H = 7.9 Hz, o-Ph, 6 H), 6.83 (t, 3JH,H = 7.2 Hz, p-Ph, 3 H), 3.40−3.36 (m, NCH2, 6 H), 3.34 (s, NMe2, 6 H), 1.29−1.15 (m, CH2, 6 H), 0.76 (dd, 2JP,H = 13.2, 3JH,H = 7.1 Hz, PCH2, 6 H). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 153.7 (s, ipso-Ph), 129.7 (s, m-Ph), 117.1 (s, p-Ph), 115.1 (s, o-Ph), 44.7 (d, 3 JC,P = 9.8 Hz, NCH2), 43.7 (d, 3JC,P = 1.3 Hz, NMe2), 25.2 (d, 1JC,P = 10.1 Hz, PCH2), 23.6 (d, 2JC,P = 2.9 Hz, CH2). 31P{1H} NMR (243 MHz, C6D6)): δ [ppm] −30.7 (s). Anal. Calcd for C29H39N4PHf: C, 53.33; H, 6.02; N, 8.58. Found: C, 53.31; H, 6.03; N, 8.35. Ph [PN3]Ti(OTf) (10-Ti). A solution of triethylsilyl trifluoromethanesulfonate (0.16 g, 0.60 mmol, 1.0 equiv) in Et2O (30 mL) was added dropwise to a solution of Ph[PN3]Ti(NMe2) (9-Ti; 0.31 g, 0.60 mmol, 1.0 equiv) in Et2O (50 mL), and the mixture was stirred at room temperature for 2 h. Over the course of the reaction a color change from red to dark green was observed along with the precipitation of a dark green solid. The precipitate was filtered off and washed twice with n-pentane (25 mL). The obtained solid was dried under vacuum to afford the product as a green powder (0.37 g, 0.56 mmol, 93%). 1H NMR (600 MHz, CD2Cl2): δ [ppm] 7.30 (t, 3JH,H = 7.9 Hz, m-Ph, 6 H), 6.98 (d, 3JH,H = 8.0 Hz, o-Ph, 6 H), 6.93 (t, 3JH,H = 7.3 Hz, p-Ph, 3 H), 3.93 (broad s, NCH2, 6 H), 1.72 and 1.69 (broad overlapping s, CH2 and PCH2, 12 H). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 153.0 (s, ipso-Ph), 129.8 (s, m-Ph), 122.3 (s, p-Ph), 120.1 (q, 1JC,F = 317 Hz, CF3), 115.0 (s, o-Ph), 50.4 (d, 3JC,P = 10.4 Hz, NCH2), 24.4 (s, CH2), 23.5 (d, 1JC,P = 16.9 Hz, PCH2). 31P{1H} NMR (243 MHz, CD2Cl2): δ [ppm] 6.2 (s). 19F{1H} NMR (376 MHz, CD2Cl2): δ [ppm] −77.7 (s). Anal. Calcd for C28H33F3N3O3PSTi: C, 53.60; H, 5.30; N, 6.70. Found: C, 53.77; H, 5.45; N, 6.78. Ph [PN3]Zr(OTf) (10-Zr). To a stirred solution of Ph[PN3]Zr(NMe2) (9-Zr; 1.57 g, 2.8 mmol, 1.0 equiv) in toluene (20 mL) was added a solution of triethylsilyl trifluoromethanesulfonate (0.82 mg, 3.1 mmol, 1.1 equiv) in toluene (20 mL), and stirring was continued at room temperature for 35 min. After removal of toluene, the semisolid residue was coevaporated with diethyl ether (10 mL) and the residual powder washed with n-pentane (20 mL). The obtained solid was dried under vacuum, affording the product as a pale orange powder (1.70 g, 2.5 mmol, 89%). 1H NMR (600 MHz, CD2Cl2): δ [ppm] 7.25−7.15 (broad s, m-Ph, 6 H), 6.87−6.70 (broad overlapping s, p-Ph and o-Ph, 9 H), 3.48 (broad s, NCH2, 6 H), 1.80−1.60 (overlapping broad s, CH2 and PCH2, 12 H). 1H NMR (600 MHz, Tol-d8): δ [ppm] 7.28 (t, 3 JH,H = 7.8 Hz, m-Ph, 6 H), 6.92 (d, 3JH,H = 8.1 Hz, p-Ph, 3 H), 6.82 (t, 3 JH,H = 7.3 Hz, o-Ph, 6 H), 3.24−3.19 (m, NCH2, 6 H), 1.15−1.01 (m, CH2, 6 H), 0.72 (dd, 2JP,H = 13.2, 3JH,H = 7.5 Hz, PCH2, 6 H). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 150.9 (s, ipso-Ph), 130.3 (s, mPh), 120.7 (s, p-Ph), 120.0 (q, 1JC,F = 317 Hz, CF3), 114.1 (s, o-Ph), 47.0 (d, 3JC,P = 8.9 Hz, NCH2), 23.4 (s, CH2), 23.2 (d, 1JC,P = 16.1 Hz, PCH2). 19F{1H} NMR (376 MHz, CD2Cl2): δ [ppm] −77.7 (s).

(t, 3JH,H = 6.9 Hz, NCH2, 6 H), 1.68−1.59 (m, CH2, 6 H), 1.45−1.36 (m, PCH2, 6 H). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 148.7 (s, ipso-Ph), 129.6 (s, m-Ph), 117.6 (s, p-Ph), 113.1 (s, o-Ph), 45.1 (d, 3 JC,P = 11.1 Hz, NCH2), 25.9 (d, 2JC,P = 13.0 Hz, CH2), 24.9 (d, 1JC,P = 14.2 Hz, PCH2). 31P{1H} NMR (243 MHz, CD2Cl2): δ [ppm] −32.3 (s). MS (ESI+, MeOH): m/z 434.3 ([M + H]+,100%). HR-MS (ESI+, MeOH): observed m/z 434.27223, calcd m/z for C27H37N3P ([M + H]+) 434.27196. N,N′,N″-Tris(tert-butyldimethylsilyl)tris(3-aminopropyl)phosphine (8e). A stirred solution of tris(3-aminopropyl)phosphine (0.65 g, 3.2 mmol, 1.0 equiv) in THF (35 mL) was cooled to 0 °C, and triethylamine (0.99 g, 1.35 mL, 9.8 mmol, 3.0 equiv) was added in one portion. Subsequently, a solution of tert-butyldimethylsilyl chloride (1.5 g, 9.9 mmol, 3.1 equiv) in THF (5 mL) was added slowly and the resulting reaction mixture was stirred for 24 h at room temperature. All volatiles were removed under vacuum, and the residue was extracted with toluene (3 × 10 mL). The combined extracts were evaporated under vacuum, and the product was thus obtained as a colorless oil (0.80 g, 1.5 mmol, 46%). 1H NMR (600 MHz, C6D6): δ [ppm] 2.85−2.75 (m, NCH2, 6 H), 1.60−1.49 (m, CH2, 6 H), 1.40−1.35 (m, PCH2, 6 H), 0.95 (s, tBu, 27 H), 0.20 (unresolved t, NH, 3 H), 0.06 (s, SiMe2, 18 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 44.4 (d, 3JC,P = 11.5 Hz, NCH2), 31.7 (d, 2JC,P = 12.4 Hz, CH2), 26.7 (s, tBu(CH3)), 25.1 (d, 1JC,P = 14.4 Hz, PCH2), 18.7 (s, tBu(Cquat)), −4.6 (s, SiMe2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −32.0 (s). MS (ESI, THF): m/z 206.3 ([M − 3 t BuMe2Si]+, 100%), 320.3 ([M − 2 tBuMe2Si]+, 8%), 433.2 ([M − t BuMe2Si]+, 3%) 549.1 ([M + H]+, 1%). (Me2N)3Ti(OTf). A solution of triethylsilyl trifluoromethanesulfonate (1.81 g, 6.85 mmol, 1.0 equiv) in Et2O (30 mL) was added dropwise to a stirred solution of tetrakis(dimethylamido)titanium (1.54 g, 6.88 mmol, 1.0 equiv) in Et2O (40 mL). The solution was stirred at room temperature for 20 min, resulting in a color change from yellow to bright orange. The solvent was removed under vacuum, and the solid residue was washed twice with n-pentane (5 mL). The product was dried under vacuum and obtained as an orange powder (2.09 g, 6.35 mmol, 93%). 1H NMR (600 MHz, CD2Cl2): δ [ppm] 3.29 (s, NCH3). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 119.7 (q, 1JC,F = 318 Hz, CF3), 43.6 (s, NCH3). 19F{1H} NMR (376 MHz, CD2Cl2): δ [ppm] −78.2 (s, CF3). Anal. Calcd for C7H18F3N3O3STi: C, 25.54; H, 5.51; N, 12.77. Found: C, 25.57; H, 5.48; N, 12.88. Ph [PN3]Ti(NMe2) (9-Ti). To a vigorously stirred solution of tris(3anilinopropyl)phosphine (8d; 0.87 g, 2.0 mmol, 1.0 equiv) in Et2O (50 mL) was added (Me2N)3Ti(OTf) (0.66 g, 2.0 mmol, 1.0 equiv) in one portion at room temperature. The reaction mixture was stirred for 24 h at room temperature, and a dark green solid precipitated, which was isolated by filtration, washed twice with Et2O (10 mL), and dried under vacuum. The solid was identified as a mixture of the desired product Ph[PN3]Ti(NMe2) and (Me2N)2Ti(OTf)2. To a suspension of this mixture (0.60 g, 0.96 mmol, 1.0 equiv) in toluene (40 mL) was added lithium dimethylamide (0.13 g, 2.6 mmol, 2.7 equiv), and the resulting reaction mixture was stirred for 1 h at room temperature. The dark red suspension was filtered through Celite, and the filter pad was washed with toluene (10 mL). The solvent was removed under reduced pressure, and the residue was washed with n-pentane and dried under vacuum. The product was obtained as a red powder (0.19 g, 0.36 mmol, 38%). 1H NMR (400 MHz, C6D6): δ [ppm] 7.33 (dd, 3 JH,H = 8.3 Hz, 3JH,H = 7.5 Hz, m-Ph, 6 H), 6.98 (d, 3JH,H = 8.0 Hz, oPh, 6 H), 6.86 (t, 3JH,H = 7.2 Hz, p-Ph, 3 H), 3.74−3.63 (m, NCH2, 6 H), 1.42−1.33 (m, CH2, 6 H), 0.91 (dd, 2JP,H = 14.2, 3JH,H = 7.1 Hz, PCH2, 6 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 155.6 (s, ipso-Ph), 129.1 (s, m-Ph), 118.7 (s, p-Ph), 117.0 (s, o-Ph), 50.1 (d, 3JC,P = 11.9 Hz, NCH2), 48.0 (d, 3JC,P = 1.3 Hz, NMe2), 24.1 (d, 2JC,P = 4.1 Hz, CH2), 23.9 (d, 1JC,P = 7.5 Hz, PCH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −30.7. Anal. Calcd for C29H39N4PTi: C, 66.66; H, 7.52; N, 10.72. Found: C, 66.97; H, 7.61; N, 10.81. Ph [PN3]Zr(NMe2) (9-Zr). To a solution of tetrakis(dimethylamido) zirconium (1.46 g, 5.5 mmol, 1.0 equiv) in toluene (40 mL) was added a solution of tris(3-anilinopropyl)-phosphine (8d, 2.37 g, 5.5 mmol, 1.0 equiv) in toluene (20 mL), and the resulting yellow solution was H

DOI: 10.1021/acs.organomet.5b00065 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

to −40 °C, and a precooled (−40 °C) solution of Bn2Mg(THF)2 (46 mg, 0.13 mmol, 1.0 equiv) in toluene (15 mL) was added slowly. The resulting reaction mixture was stirred for 35 min while it was warmed to room temperature and filtered through Celite. The Celite pad was washed with toluene (10 mL), and the combined filtrates were condensed to dryness. The residual solid was washed with n-pentane (5 mL) and dried under vacuum, affording the product as a pale yellow powder (40 mg, 57 μmol, 22%). 1H NMR (600 MHz, C6D6): δ [ppm] 7.31−7.26 (m, m-NPh, 6 H), 7.11 (d, 3JH,H = 7.0 Hz, o-Bn, 2 H), 7.10−7.05 (m, m-Bn, 2 H), 6.93 (d, 3JH,H = 7.8 Hz, o-NPh, 6 H), 6.85 (t, 3JH,H = 7.3 Hz, p-NPh, 3 H), 6.75 (t, 3JH,H = 7.2 Hz, p-Bn, 1 H), 3.45−3.40 (m, NCH2, 6 H), 2.81 (d, 3JH,P = 3.1 Hz, benzylic CH2, 1 H), 1.14−1.02 (m, CH2, 6 H), 0.64 (dd, 2JP,H = 13.1, 3JH,H = 7.1 Hz, PCH2, 6 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 152.1 (s, ipso-NPh), 150.0 (d, 3JC,P = 1.1 Hz, Bn(Cquat)), 129.5 (s, m-NPh), 128.3 (s, m-Bn), 127.0 (s, o-Bn), 120.7 (s, p-Bn), 118.7 (s, p-NPh), 114.8 (s, o-NPh), 74.7 (d, 2JC,P = 31.1 Hz, benzylic CH2), 43.9 (d, 3JC,P = 10.1 Hz, NCH2), 23.6 (d, 1JC,P = 9.2 Hz, PCH2), 22.5 (d, 2JC,P = 2.5 Hz, CH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −34.6 (s). Anal. Calcd for C34H40HfN3P: C, 58.32; H, 5.76; N, 6.00. Found: C, 58.34; H, 6.13; N, 6.12. Ph [N2PCN]Ti (12). A solution of Ph[PN3]Ti(Bn) (11-Ti; 15 mg, 26 μmol) in toluene (20 mL) was stirred at 70 °C for 5 h and subsequently cooled to room temperature. All volatiles were removed under vacuum, and the resulting residue was taken up in Et2O (10 mL) and filtered through Celite. The obtained red-brown solution was cooled to −40 °C for 1 week, and the resulting precipitate was filtered off, washed with n-pentane (2 mL), and dried under vacuum. The product was obtained as a brown solid (10 mg, 21 μmol, 80%). 1H NMR (600 MHz, C6D6): δ [ppm] 7.36 (t, 3JH,H = 8.1 Hz, m-Ph(a), 2 H), 7.28 (t, 3JH,H = 8.0 Hz, m-Ph(b), 2 H), 7.13 (d, 3JH,H = 8.1 Hz, oPh(a), 2 H), 7.06 (t, 3JH,H = 7.3 Hz, m-Ph(c), 2 H), 7.01 (t, 3JH,H = 8.1 Hz, p-Ph(a), 1 H), 6.83 (t, 3JH,H = 7.3 Hz, p-Ph(b), 1 H), 6.71 (t, 3JH,H = 7.3 Hz, p-Ph(c), 1 H), 6.61 (d, 3JH,H = 7.9 Hz, o-Ph(c), 2 H), 6.32 (d, 3 JH,H = 7.2 Hz, o-Ph(b), 2 H), 3.58 (dd, 2JH,H = 14.8 Hz, 3JH,H = 4.9 Hz, NCH2(α), 1 H), 3.37(dd, 2JH,H = 14.8 Hz, 3JH,H = 8.9 Hz, NCH2(α), 1 H), 3.30−3.25 (m, NCH2(β), 1 H), 3.19−3.14 (m, NCH2(β), 1 H), 3.05−2.90 (m, NCH(γ) overlapping with CH2(γ), 2 H), 1.80−1.71 (m, CH2(β), 2 H), 1.58−1.48 (m, CH2(α), PCH2(β), PCH2(γ), 3 H), 1.30− 1.22 (m, PCH2(α), PCH2(γ), 2 H), 1.16−1.06 (m, CH2(α), PCH2(β), PCH2(α), 3 H), 0.96−0.87 (m, CH2(γ), 1 H) with (a), (b), and (c) = individual phenyl substituents and (α), (β), and (γ) = individual aliphatic groups (due to the absence of 1H−1H COSY cross-peaks between the aliphatic and aromatic region, a direct correlation between (a), (b), (c) and (α), (β), (γ) cannot be provided). 13C NMR (151 MHz, C6D6): δ [ppm] 154.4 (d, 3JC,P = 1.1 Hz, ipso-NPh), 152.2 (s, ipso-NPh), 144.5 (d, 3JC,P = 3.0 Hz, ipso-NPh), 133.8 (s, m-NPh), 129.5 (s, m-NPh), 128.7 (s, m-NPh), 120.9 (s, p-NPh), 119.5 (s, pNPh), 118.4 (s, p-NPh), 118.1 (s, o-NPh), 114.6 (s, o-NPh), 112.2 (s, o-NPh), 89.8 (d, 3JC,P = 9.8 Hz, NCH(γ), 51.8 (d, 3JC,P = 6.5 Hz, NCH2(β)), 48.9 (d, 3JC,P = 9.6 Hz, NCH2(α)), 38.3 (d, 2JC,P = 23.7 Hz, CH2(γ)), 33.4 (d, 1JC,P = 33.0 Hz, PCH2(γ)), 26.3 (d, 2JC,P = 5.6 Hz, CH2(α)), 26.1 (d, 2JC,P = 3.6 Hz, CH2(β)), 23.3 (d, 1JC,P = 9.9 Hz, PCH2(β), 22.9 (d, 1JC,P = 10.7 Hz, PCH2(α)). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] 50.7 (s). Elemental analysis consistently gave low values for carbon and nitrogen.25

P{1H} NMR (243 MHz, CD2Cl2): δ [ppm] −17.0 (s). Anal. Calcd for C28H33N3PZrF3O3S: C, 53.13; H, 4.96; N, 6.2. Found: C, 53.84; H, 5.18; N, 6.51. Ph [PN3]Hf(OTf) (10-Hf). To a stirred solution of Ph[PN3]Hf(NMe2) (9-Hf; 0.65 g, 1.0 mmol, 1.0 equiv) in toluene (10 mL) was added a solution of triethylsilyl trifluoromethanesulfonate (295 mg, 1.11 mmol, 1.1 equiv) in toluene (10 mL), and stirring was continued at room temperature for 60 min. The reaction mixture was condensed to dryness, and the residual solid was washed with diethyl ether (3 × 10 mL) and dried under vacuum. The crude product was recrystallized from diethyl ether/methylene chloride and obtained as a pale yellow solid (0.39 g, 0.52 mmol, 52%). 1H NMR (600 MHz, C6D6): δ [ppm] 7.33 (t, 3JH,H = 7.9 Hz, m-Ph, 6 H), 6.97 (d, 3JH,H = 8.2 Hz, o-Ph, 6 H), 6.83 (t, 3JH,H = 7.3 Hz, p-Ph, 3 H), 3.18 (broad s, NCH2, 6 H), 1.06− 0.92 (m, CH2, 6 H), 0.66−0,69 (m, PCH2, 6 H). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 151.2 (s, ipso-Ph), 130.1 (s, m-Ph), 120.2 (s, p-Ph), 114.5 (s, o-Ph), 45.8 (d, 3JC,P = 8.5 Hz, NCH2), 24.0 (d, 1JC,P = 17.5 Hz, PCH2), 23.8 (s, CH2), signal for CF3 group not detected. 19 1 F{ H} NMR (376 MHz, CD2Cl2): δ [ppm] −77.5 (s). 31P{1H} NMR (243 MHz, CD2Cl2): δ [ppm] −7.6 (s). Anal. Calcd for C28H33F3HfN3O3PS: C, 44.36; H, 4.39; N, 5.54. Found: C, 44.40; H, 4.63; N, 5.44. Ph [PN3]Ti(Bn) (11-Ti). To a suspension of Ph[PN3]Ti(OTf) (0.21 g, 0.33 mmol, 2.0 equiv) in toluene (10 mL) was added Bn2Mg(THF)2 (62 mg, 0.18 mmol, 1.1 equiv) at room temperature, and stirring was continued for 2 h. The suspension was filtered through Celite, and the filter pad was washed with toluene (10 mL). The combined filtrates were evaporated under reduced pressure, and the residue was washed with n-pentane (5 mL) and dried under vacuum. The product was obtained as a red solid (91 mg, 0.16 mmol, 48%). 1H NMR (600 MHz, C6D6): δ [ppm] 7.28 (t, 3JH,H = 7.7 Hz, m-NPh, 6 H), 7.03 (d, 3 JH,H = 8.1 Hz, o-NPh, 6 H), 7.00 (t, 3JH,H = 7.5 Hz, m-Bn, 2 H), 6.92− 6.86 (overlapping signals, p-NPh and o-Bn, 5 H), 6.77 (d, 3JH,H = 7.2 Hz, p-Bn, 1 H), 3.84−3.78 (m, NCH2, 6 H), 3.44 (s, benzylic CH2, 2 H), 1.14−1.08 (m, CH2, 6 H), 0.63 (t, 3JH,H = 6.3 Hz, PCH2, 6 H). 13 C{1H} NMR (151 MHz, C6D6): δ [ppm] 154.0 (s, ipso-NPh), 152.5 (d, 3JC,P = 1.2 Hz, Bn(Cquat)), 129.2 (s, m-NPh), 127.8 (s, m-Bn), 126.4 (d, 4JC,P = 1.0 Hz, o-Bn), 120.8 (s, p-Bn), 120.1 (s, p-NPh), 116.2 (s, o-NPh), 83.6 (d, 2JC,P = 33.2 Hz, benzylic CH2), 48.5 (d, 3JC,P = 12.5 Hz, NCH2), 23.3 (d, 1JC,P = 7.2 Hz, PCH2), 23.1 (d, 2JC,P = 3.0 Hz, CH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −33.7 (s). MS (LIFDI, toluene, FD+): m/z 911.5 ([M + Ph[PN3]H3]+, 31%), 478.0 ([M − Bn]+, 35%), 433.1 (Ph[PN3]H3]+, 100%). Ph [PN3]Zr(Bn) (11-Zr). A stirred suspension of Ph[PN3]Zr(OTf) (10-Zr; 0.40 g, 0.76 mmol, 2.0 equiv) in toluene (20 mL) was cooled to −40 °C, and a precooled (−40 °C) solution of Bn2Mg(THF)2 (134 mg, 0.38 mmol, 1.0 equiv) in toluene (10 mL) was added slowly. The reaction mixture was stirred for 1 h while it was warmed to room temperature and was then filtered through Celite. The Celite pad was washed with toluene (10 mL), and the combined filtrates were evaporated to dryness. The residual solid was washed with n-pentane (2 × 5 mL) and dried under vacuum to afford the product as a yellow powder (0.19 g, 0.31 mmol, 41%). 1H NMR (600 MHz, C6D6): δ [ppm] 7.27 (t, 3JH,H = 7.8 Hz, m-NPh, 6 H), 7.13 (d, 3JH,H = 7.5 Hz, oBn, 2 H), 7.06 (t, 3JH,H = 7.4 Hz, m-Bn, 2 H), 6.91 (d, 3JH,H = 8.1 Hz, o-NPh, 6 H), 6.85 (t, 3JH,H = 7.2 Hz, p-NPh, 3 H), 6.77 (t, 3JH,H = 7.1 Hz, p-Bn, 1 H), 3.53−3.42 (m, NCH2, 6 H), 3.04 (d, 3JH,P = 2.7 Hz, benzylic CH2, 2 H), 1.23−0.94 (m, CH2, 6 H), 0.65−0.59 (m, PCH2, 6 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 152.0 (s, ipso-NPh), 150.2 (s, Bn(Cquat)), 129.7 (s, m-NPh), 128.4 (s, o-Bn), 126.5 (s, mBn), 120.2 (s, p-Bn), 119.0 (s, p-NPh), 114.5 (s, o-NPh), 66.7 (d, 2JC,P = 32.3 Hz, benzylic CH2), 44.8 (d, 3JC,P = 10.4 Hz, NCH2), 23.0 (d, 1 JC,P = 8.2 Hz, PCH2), 22.5 (d, 2JC,P = 2.7 Hz, CH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −40.2 (s). Anal. Calcd for C34H40N3PZr: C, 66.63; H, 6.58; N, 6.86; in multiple attempts low values for carbon were obtained (e.g., C, 65.28; H, 6.47; N, 6.27) possibly due to carbide formation. Ph [PN3]Hf(Bn) (11-Hf). A stirred suspension of Ph[PN3]Hf(OTf) (10-Zr; 0.20 g, 0.26 mmol, 2.0 equiv) in toluene (20 mL) was cooled 31

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S Supporting Information *

Text, figures, a table, and CIF files giving additional experimental details, selected NMR spectra, and crystallographic data and details of the structure determinations for 9-Ti and 10-Zr. This material is available free of charge via the Internet at http://pubs.acs.org. I

DOI: 10.1021/acs.organomet.5b00065 Organometallics XXXX, XXX, XXX−XXX

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AUTHOR INFORMATION

Corresponding Author

*J.B.: e-mail, [email protected]; tel, (+ 49) 6221-54-8596. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors thank the Fonds der Chemischen Industrie (FCI) and the Deutsche Forschungsgemeinschaft (DFG, BA 4859/11) for funding of this work. A Liebig-fellowship for J.B. and a Ph.D. fellowship for M.S. from the FCI is gratefully acknowledged (Li-187/02). We thank Prof. Dr. L. H. Gade for generous support, fruitful discussions, and continued interest in our work. During research internships, Hendrik Herbst, Thorsten Lohr, Sebastian Hahn, Florian Kromm, Maximilian Bojanowski, and Severin Schneider prepared additional batches of some of the compounds described herein. We thank all the latter students for their help.

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DOI: 10.1021/acs.organomet.5b00065 Organometallics XXXX, XXX, XXX−XXX

Article

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DOI: 10.1021/acs.organomet.5b00065 Organometallics XXXX, XXX, XXX−XXX