A Base-Free Terminal Actinide Phosphinidene Metallocene: Synthesis

Article Cite This: J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

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A Base-Free Terminal Actinide Phosphinidene Metallocene: Synthesis, Structure, Reactivity, and Computational Studies Congcong Zhang,† Guohua Hou,† Guofu Zi,*,† Wanjian Ding,*,† and Marc D. Walter*,‡ †

Department of Chemistry, Beijing Normal University, Beijing 100875, China Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany

‡

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S Supporting Information *

ABSTRACT: The synthesis, structure, and reactivity of a base-free terminal actinide phosphinidene metallocene have been comprehensively studied. The salt metathesis reaction of the thorium methyl iodide complex Cp‴2Th(I)Me (2; Cp‴ = η5-1,2,4-(Me3C)3C5H2) with Mes*PHK (Mes* = 2,4,6(Me3C)3C6H2) in THF furnishes the first stable base-free terminal phosphinidene actinide metallocene, Cp‴2Th PMes* (3). Density functional theory (DFT) shows that the bonds between the Cp‴2Th2+ and [PMes*]2− fragments are more covalent than those in the related thorium imido complex. While the phosphinidene complex 3 shows no reactivity toward alkynes, it reacts with a variety of heterounsaturated molecules such as CS2, isothiocyanate, nitriles, isonitriles, and organic azides, forming carbodithioates, imido complexes, metallaaziridines, and azido compounds. These experimental observations are complemented by DFT computations.

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on the structure, bonding, and reactivity.8 These aspects also inspired us to study actinide complexes with terminal metal− ligand multiple bonds and their reactivity.9 The sterically encumbered cyclopentadienyl ligand, 1,2,4-(Me3C)3C5H2 (Cp‴), has been our ligand of choice to stabilize the basefree terminal thorium imido metallocene Cp″′2Th = N(ptolyl),9a,b which readily reacts with various small molecules such as elemental sulfur (S8) and selenium (Se), silanes, borane, carbodiimides, isothiocyanates, organic azides, and diazoalkanes.9b−e In addition, the thorium imido complex Cp‴2Th = N(p-tolyl) is also an important intermediate in the catalytic hydroamination of internal acetylenes,8b an efficient catalyst for the trimerization of PhCN,9b and a useful precursor for the preparation of oxido and sulfido thorium metallocenes Cp‴2ThE (E = O, S) by cycloaddition−elimination reactions with Ph2CE (E = O, S) or CS2.9a The thorium atom has a [Rn] 6d27s2 electronic ground state which resembles that of early d-transition metals, but our studies revealed that the 5f orbital contribution modulates the bonding and reactivity of organothorium compounds.9 Encouraged by the very attractive features of the bulky 1,2,4-(Me3C)3C5H2 (Cp‴) ligand, the fascinating chemistry of the thorium imido metallocene Cp″′2Th = N(p-tolyl), and by the fact that so far no examples of base-free terminal phosphinidene actinide metallocenes have been reported, we have extended our investigations to actinide phosphinidene metallocenes supported by two 1,2,4-(Me3C)3C5H2 (Cp‴) ligands. In this

INTRODUCTION As the phosphorus analogues of alkylidene and imido complexes, metal phosphinidene complexes have received considerable attention over the past two decades.1 This development has been motivated by their rich chemistry and their potential utility as intermediates or catalysts in the preparation of phosphorus compounds, organometallic derivatives, and new materials.1 In this context, variations of the metals bound to the phosphinidene ligands results in specific changes in their structure and catalytic activity as well as chemical and physical properties.1−4 Terminal phosphinidene metal complexes with a MPR double bond are highly reactive, resulting not only in new phosphorus-containing molecules but also more efficient phosphorus−element bond synthesis and useful catalytic transformations.1−3 Nevertheless, while the reactivity and properties of the terminal phosphinidenes of d-transition metals are now well explored and understood,1−3 the related terminal phosphinidene actinide complexes have been difficult to access, and therefore, their intrinsic reactivity remained virtually unexplored.5 Hence, only a few examples of terminal phosphinidene actinide complexes have been structurally authenticated so far,5b,c,e−g and steric effects imposed by the ligand exert a considerable influence on the formation of the terminal multiple-bonded actinide complexes, in general.5,6 Thus, the development of novel actinide compounds with terminal phosphinidene units represents an interesting, yet challenging, synthetic target for which bulky ligands are a prerequisite. Nevertheless, research activities in organoactinide chemistry have centered on small molecule activation7 and the influence of the 6d and 5f orbitals © XXXX American Chemical Society

Received: September 8, 2018

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DOI: 10.1021/jacs.8b09746 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

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Journal of the American Chemical Society

spectroscopic techniques, elemental analysis, and single-crystal X-ray diffraction. The 31P{1H} NMR spectrum features a singlet resonance at δ = 145.7 ppm, corresponding to a phosphinidiide ligand,5e,g and therefore supports the formation of 3. The molecular structure of 3 is shown in Figure 2, and selected bond distances and angles are listed in Table 1. To the best of our knowledge, 3 constitutes the first structurally authenticated base-free terminal phosphinidene actinide metallocene, and it also represents an important addition to the family of structurally characterized actinide phosphinidene metallocenes, (η5-C5Me5)2U(P-2,4,6-tBu3C6H2)(OPMe3),5b {[(η5-C5Me5)2Th(P-2,4,6-iPr3C6H2)(PH-2,4,6-iPr3C6H2)]K} 2 , 5g and [(η 5 -C 5 Me 5 ) 2 Th(P-2,4,6- i Pr 3 C 6 H 2 )(PH2,4,6-iPr3C6H2)][K(2,2,2-cryptand)].5g The short Th−P distance of 2.536(2) Å and the approximately linear Th−P− C(35) angle (177.2(2)°) are consistent with a ThP double bond.10 Furthermore, the Th−P distance of 2.536(2) Å is shorter than those found in [(iPr3SiNCH2CH2)3NTh PH][Na(12-c-4)2] (2.7584(18) Å),5e {[(η5-C5Me5)2Th(P2,4,6-iPr3C6H2)(PH-2,4,6-iPr3C6H2)]K}2 (2.6957(10) Å),5g and [(η5-C5Me5)2Th(P-2,4,6-iPr3C6H2)(PH2,4,6-iPr3C6H2)][K(2,2,2-cryptand)] (2.6024(9) Å).5g Overall, these structural parameters of 3 are fully consistent with the formation of a thorium phosphinidene metallocene. Bonding Studies. To further probe the interaction between the thorium atom and the [Mes*P] moiety, density functional theory (DFT) computations at the B3PW91 level of theory were undertaken. The bonding in 3 was also compared to its hypothetical thorium imido analogue Cp‴2ThNMes* (3′). While the computed structure of 3 is in excellent agreement with the experimental data, computations also reveal that the [Mes*E]2− fragment is coordinated to the Cp‴2Th2+ moiety by one Th−E σ-bond and two Th−E πbonds, as illustrated in Figure 3. A natural localized molecular orbital (NLMO) analysis (Table 2) suggests that the Th−P σbond, σ(ThP), is composed of a phosphorus hybrid orbital (78.7%; 76.7% 3s and 23.3% 3p) and a thorium hybrid orbital (20.6%; 15.0% 5f and 65.5% 6d). One of the Th−P π bonds (π1) consists of a pure 3p phosphorus-based orbital (70.7%) and a thorium hybrid orbital (25.2%; 64.3% 6d and 33.9% 5f), whereas the other Th−P π bond (π2) is formed by a pure 3p phosphorus-based orbital (66.0%) and a thorium hybrid orbital (30.9%; 74.0% 6d and 24.0% 5f). These findings indicate that electron density is effectively transferred from the π-orbitals of [Mes*P]2− fragment to the electron-deficient and Lewis acidic thorium atom. Moreover, the Th−P distance of 2.536(2) Å (2.542 Å (computed)) in complex 3 is shorter than that found in [(iPr3SiNCH2CH2)3NThPH][Na(12-c-4)2] (2.7584(18) Å; 2.709 Å (computed)),5e which results in a larger degree of covalency between the Th and P atoms in complex 3 than those found in [(iPr3SiNCH2CH2)3NThPH][Na(12-c-4)2] (12% Th for ThP σ bond, and 14% Th for ThP π bond, respectively).5e Nevertheless, in the hypothetical thorium imido complex Cp‴2ThNMes* (3′), the metal contribution to the bonding of the ThNMes* moiety decreases notably (8.9% Th for the ThN σ bond and 13.0% and 15.4% Th for the ThN π1 and π2 bonds, respectively) (Table 2). This is also reflected in an increased charge separation and therefore increased electrostatic interaction between the individual Cp‴2Th2+ and [Mes*E]2− fragments, that is, 0.80 (for E = P (3)) and 2.18 for (E = N (3′) (Table 2). Moreover, the Wiberg bond order of the ThE decreases from 2.099 (for 3) to 1.202 (for 3′)) (Table 2). Both observations are consistent

paper, we report on some observations concerning the synthesis, bonding, and structure−reactivity relationship of the first stable terminal actinide phosphinidene metallocene Cp″′2ThPMes* (3) and describe the differences and similarities between the phosphinidene (ThPR) and imido (ThNR) complexes.

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RESULTS AND DISCUSSION Synthesis of Cp‴2ThPMes* (3). Treatment of CuI with 1 equiv of the dimethyl metallocene Cp‴2ThMe2 (1) in toluene gives the thorium methyl iodide metallocene, Cp‴2Th(I)Me (2), in 90% yield (Scheme 1). The molecular Scheme 1

Figure 1. Molecular structure of 2 (thermal ellipsoids drawn at the 35% probability level).

structure of 2 is shown in Figure 1, and selected bond distances and angles are listed in Table 1. The Th−C(35) distance is 2.470(7) Å, whereas the Th−I distance is 3.048(1) Å, and the angle of C(35)−Th−I is 92.7(2)°. Subsequent salt metathesis between 2 and 1 equiv of Mes*PHK in THF affords the desired base-free terminal phosphinidene thorium metallocene, Cp‴2ThPMes* (3), in 80% yield (Scheme 1). While 3 is air and moisture sensitive, it can be stored without any degradation in a dry nitrogen atmosphere at room temperature. Complex 3 is soluble in and readily recrystallized from a benzene solution, and it was fully characterized by various B


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Journal of the American Chemical Society Table 1. Selected Bond Distances (Å) and Angles (deg) for Compounds 2−16a compd

C(Cp)−Thb

C(Cp)−Thc

Cp(cent)−Thb

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

2.851(7) 2.859(6) 2.842(6) 2.838(9) 2.908(8) 2.855(9) 2.873(6) 2.881(5) 2.906(12) 2.890(4) 2.859(7) 2.885(5) 2.876(6) 2.883(3) 2.861(11)

2.793(7)−2.929(7) 2.777(6)−2.980(6) 2.752(6)−2.970(6) 2.775(9)−2.906(8) 2.753(8)−3.113(7) 2.770(9)−2.970(9) 2.755(6)−3.026(6) 2.779(4)−3.008(5) 2.798(12)−3.000(12) 2.782(4)−3.002(3) 2.777(7)−2.977(7) 2.774(5)−3.045(5) 2.779(6)−3.011(6) 2.733(3)−3.046(3) 2.772(11)−2.941(11)

2.581(7) 2.590(6) 2.573(6) 2.567(9) 2.649(8) 2.585(9) 2.606(6) 2.614(5) 2.643(12) 2.625(4) 2.591(7) 2.620(5) 2.610(6) 2.620(3) 2.591(11)

Th−X C(35) P(1) S(1) S(1) S(1) N(1) N(1) N(1) N(1) N(1) N(1) N(1) N(1) N(1) N(1)

2.470(7), 2.536(2) 2.704(1), 2.733(2), 2.713(2), 2.080(7) 2.062(6) 2.072(4) 2.143(9), 2.094(3), 2.266(6), 2.359(4), 2.316(6), 2.330(2), 2.273(9),

Cp(cent)−Th−Cp(cent)

X−Th−X/Y

139.4(5) 135.8(3) 135.8(4) 143.6(5) 119.2(5) 143.9(5) 138.8(4) 138.8(3) 139.8(7) 144.3(3) 139.5(4) 130.8(3) 132.3(4) 131.5(2) 137.8(6)

92.7(2)

I(1) 3.048(1) S(2) 2.771(1) S(2) 2.731(2) S(2) 2.726(2)

N(2A) 2.575(10) N(2A) 2.566(3) N(2) 2.365(6) C(38) 2.410(5) C(35) 2.398(7) C(43) 2.440(3) N(2) 2.306(9)

67.5(1) 68.1(1) 76.5(1)

95.8(3)d 87.0(1)d 62.0(2) 33.3(2) 33.3(2) 33.2(1) 95.3(3)

a

Cp = cyclopentadienyl ring. bAverage value. cRange. dThe angle of N(1)−Th(1)−N(2A).

Table 2. Natural Localized Molecular Orbital (NLMO) Analysis of ThEMes* Bonds,a Bond Order, and the Natural Charges for the [Cp‴2Th] and [Mes*E] Units σ Th−E

π1 ThE


π2 ThE

Wiberg bond order (ThE) NBO charge (Th) NBO charge (E) NBO charge (Cp2Th) NBO charge (ArE)

Figure 3. Plots of HOMOs for 3 (the hydrogen atoms have been omitted for clarity).

with a more polarized and more ionic bond between the metallocene Cp‴2Th2+ and the nitrene fragment [Mes*N]2−, and the π-donation from the π-MO of the nitrene fragment to the metal atom decreases. This difference reflects itself in the reactivity of the thorium phosphinidene (3) when compared to thorium imido compounds.9,11 Reactivity Studies. The electronic structure within the moiety ThPMes* should reflect itself in a high reactivity toward unsaturated organic substrates. However, in contrast to the thorium imido Cp‴2ThN(p-tolyl),9b,11 no reaction occurs between complex 3 and internal alkyne RCCR (R = Ph, Me, p-tolyl) even when the mixture is heated at 100 °C for 1 week, presumably due to the steric hindrance between the incoming alkyne and the ThPMes* fragment. Nevertheless, like the thorium imido complexes,9,11 complex 3 reacts readily

% % % % % % % % % % % % % % % % % % % %

Th s p d f E s p Th p d f E p Th p d f E p

3 (E = P)

3′ (E = N)

20.6 9.4 10.1 65.5 15.0 78.7 76.7 23.3 25.2 1.8 64.3 33.9 70.7 100 30.9 2.0 74.0 24.0 66.0 100 2.099 0.62 −0.12 0.40 −0.40

8.9 1.5 3.5 71.0 24.0 90.3 54.7 45.3 13.0 1.0 69.0 30.0 84.8 100 15.4 0.5 72.6 26.9 81.6 100 1.202 1.73 −1.20 1.09 −1.09

a

The contributions by atom and orbital are averaged over all the ligands of the same character.

with hetero-unsaturated organic substrates. For example, the reaction of complex 3 and 1 equiv of CS2 forms the carbodithioate compound Cp‴2Th[SC(PMes*)S] (4) at room temperature in quantitative conversion (Scheme 2). We propose that CS2 initially reacts with 3 via a [2 + 2] cycloaddition to yield a four-membered thorium metallaheterocycle. Nevertheless, unlike the complex Cp‴2Th[N(p-tolyl)C(S)S] formed by the reaction of the thorium imido complex Cp‴2ThN(p-tolyl) with CS2,9a,11 this intermediate converts to 4 by a [1,3]-Th migration (Scheme C


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Journal of the American Chemical Society Scheme 2

Scheme 3

2). The molecular structure of 4 is shown in Figure 4, and selected bond distances and angles are listed in Table 1. The


Th−S(1) distance is 2.704(1) Å, whereas the Th−S(2) distance is 2.771(1) Å, and the angle of S(1)−Th−S(2) is 67.5(1)°. However, the carbodithioate Cp‴2Th[SC(NPh)S] (5) is isolated from the reaction of complex 3 with PhNCS at room temperature in quantitative conversion. Furthermore, the amount of PhNCS added to the reaction mixture has no influence on the product formation (Scheme 3). We suggest that one molecule of PhNCS initially reacts with 3 via a [2 + 2] cycloaddition to give a four-membered metallaheterocycle, but unlike the complex Cp‴2Th[N(p-tolyl)C(NPh)S] formed in the reaction of Cp‴2ThN(p-tolyl) and PhNCS,9a,11 this intermediate eliminates PhNCPMes* to yield the monomeric terminal sulfido intermediate Cp‴2ThS, which spontaneously reacts with a second molecule of PhNCS to furnish complex 5 (Scheme 3). DFT investigations imply that complex 3 initially reacts with PhNCS via [2 + 2] cycloaddition to give the heterocyclic intermediate INT5a, which then degrades to the sulfido INT5b and PhNCPMes*. The formation of INT5b from 3 + PhNCS is very exergonic with ΔG(298 K) = −32.9 kcal/mol and proceeds via two transition states (TS5a and TS5b) with an overall reaction barrier of ΔG⧧(298 K) = 24.5 kcal/mol (Figure 5). However, reaction of INT5b with a

Figure 5. Energy profile (kcal/mol) for the reaction of 3 + PhNCS + PhNCS (computed at T = 298 K). [Th] = [η 5 -1,2,4(Me3C)3C5H2]2Th. Ar = 2,4,6-tBu3C6H2.

second molecule of PhNCS to form 5 is thermodynamically even more preferred (ΔG(298 K) = −42.2 kcal/mol), and it occurs via the transition state TS5c with a low activation barrier (ΔG⧧(298 K)) of 11.6 kcal/mol. Overall, this reaction profile is consistent with the experimentally observed formation of 5 at ambient temperature. Nevertheless, the elimination of PhNCS from 5 to INT5b is only slightly uphill with ΔG(298 K) = 9.3 kcal/mol and proceeds with a reaction barrier of ΔG⧧(298 K)) = 20.9 kcal/mol (Figure 5). This explains why complex 5 is thermal unstable and eliminates PhNCS at 75 °C to form the sulfido intermediate Cp‴2ThS, which then dimerizes to give (Cp‴2Th)2(μ-S)2 (6) (Scheme 3).9a The molecular structures of 5 and 6 are depicted in Figures 6 and 7, and selected bond distances and angles are shown in Table 1. The Th−S distances are 2.733(2) and D


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Figure 8. Energy profile (kcal/mol) for the reaction of 3 + PhCN (computed at T = 298 K). [Th] = [η5-1,2,4-(Me3C)3C5H2]2Th. Ar = 2,4,6-tBu3C6H2.

Figure 9, whereas the structures of 8 and 9 are provided in the Supporting Information. The Th−N distances are 2.080(7) Å


2.731(2) Å for 5 and 2.713(2) and 2.726(2) Å for 6, which are comparable to those found in 4 (Table 1). However, in contrast to the reactivity of the thorium imido Cp‴2ThN(p-tolyl) toward nitriles,9b,11 no metallaheterocycles are isolated from the reaction of 3 and nitrile RCN (R = Ph, C6H11, Me3C); instead, the imido complexes Cp‴2Th NC(PMes*)R (R = Ph (7), C6H11 (8), Me3C (9)) are formed in quantitative conversion (Scheme 4). We propose that nitrile RCN initially reacts with 3 in a [2 + 2] cycloaddition to give a four-membered metallaheterocycle. However, unlike the complex Cp‴2Th[N(p-tolyl)C(Ph)N] formed by the reaction of the thorium imido complex Cp‴2ThN(p-tolyl) with PhCN,9b,11 this intermediate rearranges to the imido complexes 7−9 (Scheme 4). According to our DFT studies, the formation of 7 is exergonic (ΔG(298 K) = −20.7 kcal/mol) and proceeds via the concerted [2 + 2] transition state TS7 with a low reaction barrier of ΔG⧧(298 K) = 12.7 kcal/mol (Figure 8), which agrees with the experimentally observed rapid formation of 7 at ambient temperature. The molecular structure of 7 is shown in


for 7, 2.062(6) Å for 8 and 2.072(4) Å for 9, which are comparable to that in Cp‴2ThN(p-tolyl) (2.038(3) Å).9b Moreover, reaction of 3 with 1 equiv of m-C6H4(CN)2 or pC6H4(CN)2 gives the dimeric imido compounds [Cp‴2Th NC(PMes*)R]2 (R = 3-NCPh (10), 4-NCPh (11)) in good yields (Scheme 5). In these reactions, the steric bulk of the monomeric thorium imido complexes Cp‴2ThNC( PMes*)R is insufficient to prevent dimerization. The molecular structures of 10 and 11 are shown in Figures 10 E


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Scheme 6


and 11, and selected bond distances and angles are compared in Table 1. The Th−N distances are 2.143(9) and 2.575(10) Å for 10, which are comparable to those in 11 (2.094(3) and 2.566(3) Å). Nevertheless, when o-C6H4(CN)2 is used as substrate, a four-membered heterocycle Cp‴2Th[NC(N)(C6H4CPMes*)] (12) is formed in quantitative conversion (Scheme 6). We suggest that one nitrile group of oC6H 4(CN) 2 initially reacts with 3 to give an imido intermediate, subsequently, the imido intermolecularly reacts with the other nitrile group via a [2 + 2] cycloaddition to give 12 (Scheme 6). The molecular structure of 12 is shown in Figure 12, and selected bond distances and angles are provided in Table 1. The Th−N(1) distance is 2.266(6) Å, whereas the


Th−N(2) distance is 2.365(6) Å, and the angle of N(1)−Th− N(2) is 62.0(2)°. In contrast to the reactivity of the thorium imido Cp‴2Th N(p-tolyl) toward isonitrile,11 no C−H bond activation of a methyl group of the 1,2,4-(Me3C)3C5H2 ligand occurs;11 F


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Journal of the American Chemical Society instead, the reaction of complex 3 and isonitrile RNC (R = Me3Si, C6H11, 2,6-Me2Ph) forms metallaaziridines Cp‴2Th[C(PMes*)N(R)] (R = Me3Si (13), C6H11 (14), 2,6Me2Ph (15)) in quantitative conversions (Scheme 7). The Scheme 7


complex Cp‴2Th(NPMes*)(N3) (16) and Gomberg’s dimer Ph3CCH(C2H2)2CCPh2 are formed (Scheme 8). It isolation of the metallaaziridines 13−15 may be rationalized by an initial [2 + 1] cycloaddition of 3 with isonitrile, followed by a [1,3]-Th migration (Scheme 7). DFT studies predict that the formation of 15 is energetically favorable (ΔG(298 K) = −6.3 kcal/mol) and proceeds via intermediate INT15 and two transition states (TS15a and TS15b) with an overall low reaction barrier of ΔG⧧(298 K) = 12.1 kcal/mol (Figure 13).

Scheme 8

Figure 13. Energy profile (kcal/mol) for the reaction of 3 + 2,6Me 2 PhNC (computed at T = 298 K). [Th] = [η 5 -1,2,4(Me3C)3C5H2]2Th. Ar = 2,4,6-tBu3C6H2. Ph′ = 2,6-Me2Ph.

This energy profile is fully consistent with the rapid formation of 15 at ambient temperature. The molecular structure of 15 is shown in Figure 14, whereas the structures of 13 and 14 are provided in the Supporting Information. The Th−N distances are 2.359(4) Å for 13, 2.316(6) Å for 14 and 2.330(2) Å for 15, and the Th−C distances are 2.410(4) Å for 13, 2.398(7) Å for 14 and 2.440(3) Å for 15. These structural parameters are in the same range as those reported for (η5-C5Me5)2Th[C( P-2,4,6-iPr3C6H2)NtBu](CNtBu) with the Th−N distance of 2.346(5) Å and Th−C distance of 2.430(6) Å.12 Moreover, in contrast to the reactivity of the thorium imido Cp‴2ThN(p-tolyl) toward organic azides,9d,11 treatment of 3 with Ph3CN3 at room temperature does not form a fivemembered thorium metallacycle, instead, the thorium azido

appears reasonable that one molecule of Ph3CN3 initially reacts with 3 via a [2 + 1] cycloaddition to give a three-membered heterocyclic complex. In the next step, this intermediate converts by electron transfer to form an iminato intermediate, which further converts with a second molecule of Ph3CN3 by a nucleophilic attack to yield compound 16 and the diazene derivative (Ph3C)2N2. Finally, Gomberg’s dimer Ph3CCH(C2H2)2CCPh213 and N2 are formed from the degradation G


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Journal of the American Chemical Society of (Ph3C)2N2 (Scheme 8). Alternatively, analogous to the reaction of the thorium imido Cp‴2ThN(p-tolyl) with ptolylN3,9d,11 a mechanism may be proposed that involves initial reaction of 3 with Ph3CN3 to give a five-membered thorium metallacycle (A or B). In the next step, this intermediate releases N2 to yield a three-membered thorium metallacycle, which subsequently forms an iminato intermediate, which further converts with a second molecule of Ph3CN3 by a nucleophilic attack to yield compound 16 and Gomberg’s dimer Ph3CCH(C2H2)2CCPh2 (Scheme 8). The molecular structure of 16 is shown in Figure 15, and selected bond

Scheme 9

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CONCLUSIONS In conclusion, the first stable base-free terminal phosphinidene actinide metallocene, Cp‴2ThPMes* (3), was comprehensively studied. Density functional theory suggests that the Cp‴2Th2+ and [PMes*]2− fragments form more covalent bonds than those in the related thorium imido metallocene. Whereas the ThNR moiety in the thorium imido metallocene reacts with internal alkynes and hetero-unsaturated molecules to form the stable [2 + 2] or [2 + 3] cycloaddition products,9,11 the ThPR functionality in the thorium phosphinidene 3 remains inert to alkynes, but it reacts with a variety of heterounsaturated molecules such as CS2, isothiocyanate, nitriles, and isonitriles, yielding carbodithioates, imido complexes, and metallaaziridines, while the rearrangement occurs during the course of the reactions. Furthermore, complex 3 undergoes a rather complex reaction sequence with Ph3CN3 to yield Cp‴2Th(NPMes*)(N3) (16) besides Gomberg’s dimer Ph3CCH(C2H2)2CCPh2 and N2. In contrast, upon treatment with Me3SiN3, complex 3 converts to the thorium imido complex Cp‴2ThNSiMe3 (17). Further investigations on the intrinsic reactivity of terminal phosphinidene actinide metallocenes are ongoing and will be reported in due course.


distances and angles are shown in Table 1. The Th−N(1) distance is 2.273(9) Å, whereas the Th−N(2) distance is 2.306(9) Å, and the angle of N(1)−Th−N(2) is 95.3(3)°, which are comparable to those found in (η5-C5Me5)2Th[N(SiMe3)2](N3) with the Th−N distances of 2.334(7) and 2.301(7) Å and an angle of N−Th−N of 88.3(3)°.14 The N P distance is 1.555(9) Å, and the angle of Th−N−P is 144.9(6)°, whereas the angle of N−P−C is 106.1(5)°. However, under similar reaction conditions, treatment of 3 with Me3SiN3 furnishes the thorium imido Cp‴2ThNSiMe3 (17) and the phosphaindane derivative 3,3-Me2-5,7-tBu2C8H5P (18) accompanied by N2 release. Analogous to the reaction of the thorium imido Cp‴2ThN(p-tolyl) with p-tolylN3,9d,11 it is suggested that 3 initially reacts with Me3SiN3 to give a fivemembered thorium metallacycle. However, to reduce the steric hindrance around the metal atom, this intermediate then converts to the thorium imido 17 by Mes*PN2 elimination. The latter further degrades by N2 loss to form the highly reactive phosphinidene species 2,4,6-tBu3C6H2P, which converts to the phosphaindane 3,3-Me2-5,7-tBu2C8H5P (18) via C−H bond activation (Scheme 9). Alternatively, in analogy to the reaction of Cp‴2Th(bipy) with Me3SiN3,13 Me3SiN3 may displace the phosphinidene 2,4,6-tBu3C6H2P in 3 to form a four-membered metallacycle, which subsequently releases N2 to yield the imido complex 17, whereas C−H bond activation converts the phosphinidene 2,4,6-tBu3C6H2P to the phosphaindane 3,3-Me2-5,7-tBu2C8H5P (18) (Scheme 9).

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EXPERIMENTAL SECTION

General Procedures. All reactions and product manipulations were carried out under an atmosphere of dry dinitrogen with rigid exclusion of air and moisture using standard Schlenk or cannula techniques or in a glovebox. All organic solvents were freshly distilled from sodium benzophenone ketyl immediately prior to use. Cp‴2ThMe2 (1),9a,b Mes*PH2,15 and Mes*PHK16 were prepared according to literature methods. All other chemicals were purchased from Aldrich Chemical Co. and Beijing Chemical Co. and used as received unless otherwise noted. Infrared spectra were recorded in KBr pellets on an Avatar 360 Fourier transform spectrometer. 1H, 13 C{1H}, and 31P{1H} NMR spectra were recorded on a Bruker AV 400 spectrometer at 400, 100, and 162 MHz, respectively. All H


Article

Journal of the American Chemical Society chemical shifts are reported in δ units with reference to the residual protons of the deuterated solvents, which served as internal standards for proton and carbon chemical shifts, and to external 85% H3PO4 (0.00 ppm) for phosphorus chemical shifts. Melting points were measured on an X-6 melting point apparatus and were uncorrected. Elemental analyses were performed on a Vario EL elemental analyzer. Preparation of Cp‴2Th(I)Me (2). Solid CuI (0.38 g, 2.0 mmol) was slowly added to a stirred toluene (20 mL) solution of Cp‴2ThMe2 (1; 1.46 g, 2.0 mmol) at room temperature. During the reaction, the initially formed CuMe further degraded to ethane (CH3CH3) and copper metal (Cu),9f which deposits as an orange-red precipitate. After this solution was stirred at room temperature 1 week, the solvent was removed. The residue was extracted with benzene (10 mL × 3) and filtered. The volume of the combined filtrate was reduced to 10 mL, and colorless crystals of 2 were isolated after this solution was kept at room temperature for 2 days. Yield: 1.51 g (90%). Mp: 163−165 °C dec. 1H NMR (C6D6): δ 6.52 (d, J = 3.2 Hz, 2H, ring CH), 6.46 (d, J = 3.6 Hz, 2H, ring CH), 1.62 (s, 18H, C(CH3)3), 1.56 (s, 18H, C(CH3)3), 1.26 (s, 18H, C(CH3)3), 0.91 (s, 3H, ThCH3) ppm. 13C{1H} NMR (C6D6): 146.0 (ring C), 145.6 (ring C), 145.4 (ring C), 116.5 (ring C), 116.3 (ring C), 67.2 (ThCH3), 35.5 (C(CH3)3), 35.4 (C(CH3)3), 34.5 (C(CH3)3), 34.5 (C(CH3)3), 33.8 (C(CH3)3), 32.7 (C(CH3)3) ppm. IR (KBr, cm−1): ν 2960 (s), 2904 (m), 2868 (w), 1460 (m), 1386 (m), 1261 (s), 1091 (s), 1020 (s), 798 (s). Anal. Calcd for C35H61ITh: C, 50.00; H, 7.31. Found: C, 49.83; H, 7.39. Preparation of Cp‴2ThPMes*·C6H6 (3·C6H6). A THF (10 mL) solution of Mes*PHK (316 mg, 1.0 mmol) was added to a THF (10 mL) solution of Cp‴2Th(I)Me (2; 841 mg, 1.0 mmol) with stirring at room temperature. After the solution was stirred at room temperature overnight, the solvent was removed. The residue was extracted with benzene (10 mL × 3) and filtered. The volume of the filtrate was reduced to 10 mL, and orange crystals of 3·C6H6 were isolated when this solution was kept at room temperature for 2 days. Yield: 842 mg (80%). Mp: 165−167 °C dec. 1H NMR (C6D6): δ 7.64 (s, 2H, phenyl), 7.33 (s, 2H, ring CH), 7.15 (s, 6H, C6H6), 6.03 (d, J = 2.8 Hz, 2H, ring CH), 2.20 (s, 18H, C(CH3)3), 1.64 (s, 18H, C(CH3)3), 1.58 (s, 18H, C(CH3)3), 1.46 (s, 18H, C(CH3)3), 1.32 (s, 9H, C(CH3)3) ppm. 13C{1H} NMR (C6D6): δ 161.5 (d, JP−C = 66.7 Hz, phenyl C), 154.3 (phenyl C), 144.9 (phenyl C), 142.1 (phenyl C), 141.6 (ring C), 136.8 (ring C), 128.0 (C6H6), 121.7 (ring C), 120.9 (d, JP−C = 4.4 Hz, ring C), 116.8 (ring C), 38.4 (C(CH3)3), 35.3 (C(CH3)3), 34.8 (C(CH3)3), 34.7 (C(CH3)3), 34.3 (C(CH3)3), 33.7 (d, JP−C = 2.9 Hz, C(CH3)3), 33.5 (C(CH3)3), 33.4 (C(CH3)3), 31.8 (C(CH3)3), 27.0 (C(CH3)3) ppm. 31P{1H} NMR (C6D6): δ 145.7 ppm. IR (KBr, cm−1): ν 2960 (s), 2904 (m), 2866 (m), 1595 (w), 1456 (w), 1384 (m), 1359 (m), 1259 (s), 1091 (s), 1018 (s), 798 (s). Anal. Calcd for C58H93PTh: C, 66.13; H, 8.90. Found: C, 65.98; H, 8.96. Preparation of Cp‴2Th[SC(PMes*)S]·C6H6 (4·C6H6). Method A. A toluene (5 mL) solution of CS2 (19 mg, 0.25 mmol) was added to a toluene (10 mL) solution of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) with stirring at room temperature. After the solution was stirred at room temperature overnight, the solvent was removed. The residue was extracted with benzene (10 mL × 3) and filtered. The volume of the filtrate was reduced to 5 mL, and yellow crystals of 4· C6H6 were isolated when this solution was kept at room temperature for 1 week. Yield: 245 mg (87%). Mp: 235−237 °C. 1H NMR (C6D6): δ 7.65 (s, 2H, phenyl), 7.15 (s, 6H, C6H6), 6.40 (s, 4H, ring CH), 1.89 (s, 18H, C(CH3)3), 1.43 (s, 27H, C(CH3)3), 1.40 (s, 18H, C(CH3)3), 1.27 (s, 18H, C(CH3)3) ppm. 13C{1H} NMR (C6D6): δ 155.4 (phenyl C), 149.2 (phenyl C), 145.7 (phenyl C), 139.9 (d, JP−C = 65.4 Hz, phenyl C), 128.0 (C6H6), 127.3 (ring C), 121.6 (ring C), 121.5 (ring C), 38.7 (C(CH3)3), 35.3 (C(CH3)3), 35.0 (C(CH3)3), 34.7 (C(CH3)3), 34.4 (C(CH3)3), 34.1 (C(CH3)3), 32.2 (C(CH3)3), 31.7 (C(CH3)3) ppm; carbon of (SCP) was not observed. 31P{1H} NMR (C6D6): δ 225.2 ppm. IR (KBr, cm−1): ν 2960 (s), 2906 (m), 2868 (m), 1593 (w), 1386 (s), 1361 (s), 1093 (w), 1016 (m), 800 (m). Anal. Calcd for C59H92PS2Th: C, 62.79; H, 8.22. Found: C, 62.75; H, 8.23.

Method B. NMR Scale. A C6D6 (0.3 mL) solution of CS2 (1.5 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 4 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of Cp‴2Th[SC(NPh)S] (5). Method A. This compound was obtained as yellow crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and PhNCS (68 mg, 0.50 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by a procedure similar to that used in the synthesis of 4. Yield: 169 mg (78%). Mp: 123−125 °C dec. 1H NMR (C6D6): δ 7.34−7.28 (m, 4H, phenyl), 6.95 (t, 1H, J = 6.8 Hz, phenyl), 6.65 (s, 2H, ring CH), 6.62 (s, 2H, ring CH), 1.47 (s, 18H, C(CH3)3), 1.44 (s, 18H, C(CH3)3), 1.23 (s, 18H, C(CH3)3) ppm. 13 C{1H} NMR (C6D6): δ 155.5 (C=NPh), 152.8 (phenyl C), 146.6 (phenyl C), 146.5 (phenyl C), 146.0 (phenyl C), 128.8 (ring C), 123.0 (ring C), 122.1 (ring C), 119.9 (ring C), 119.9 (ring C), 35.2 (C(CH3)3), 35.1 (C(CH3)3), 33.9 (C(CH3)3), 33.7 (C(CH3)3), 31.5 (C(CH3)3) ppm. IR (KBr, cm−1): ν 2958 (s), 2924 (s), 2868 (s), 1847 (m), 1593 (s), 1535 (s), 1388 (s), 1359 (s), 1238 (s), 1022 (s), 833 (s). Anal. Calcd for C41H63NS2Th: C, 56.86; H, 7.33; N, 1.62. Found: C, 56.82; H, 7.39; N, 1.61. Method B. NMR Scale. A C6D6 (0.3 mL) solution of PhNCS (5.4 mg, 0.04 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 5 along with those of PhNCPMes* (1H NMR: 7.60 (d, 2H, J = 2.0 Hz, phenyl), 6.94 (d, 2H, J = 7.7 Hz, phenyl), 6.83 (t, 2H, J = 7.5 Hz, phenyl), 6.70 (m, 1H, J = 7.4 Hz, phenyl), 1.79 (s, 18H, C(CH3)3), 1.23 (s, 9H, C(CH3)3) ppm. 31P{1H} NMR (C6D6): δ −107.4 ppm.)17 were observed by NMR spectroscopy (100% conversion) after the sample was kept at room temperature overnight. Reaction of Cp‴2ThPMes* (3) with PhNCS. NMR Scale. A C6D6 (0.2 mL) solution of PhNCS (2.7 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.3 mL). Resonances of 5 along with those of unreacted 3 and PhNCPMes* were observed by 1H NMR spectroscopy (50% conversion based on 3) after the sample was kept at room temperature overnight. Preparation of (Cp‴2Th)2(μ-S)2 (6). Method A. After a benzene (10 mL) solution of Cp‴2Th[SC(NPh)S] (5; 173 mg, 0.2 mmol) was stirred at 75 °C overnight, the solution was filtered. The volume of the filtrate was reduced to 2 mL, and colorless crystals 6 were isolated from the mixture after this solution stood at room temperature for 2 days. Yield: 105 mg (72%). 1H NMR (C6D6): δ 6.85 (d, J = 2.4 Hz, 2H, ring CH), 6.81 (d, J = 2.4 Hz, 2H, ring CH), 1.91 (s, 18H, (CH3)3C), 1.61 (s, 18H, (CH3)3C), 1.57 (s, 18H, (CH3)3C). These spectroscopic data agreed with those reported in the literature.9a Method B. NMR Scale. After an NMR sample of Cp‴2Th[SC( NPh)S] (5; 17 mg, 0.02 mmol) with C6D6 (0.5 mL) was heated at 75 °C overnight, resonances due to 6 along with those of PhNCS (1H NMR (C6D6): δ 6.70 (t, 3H, J = 2.9 Hz, phenyl), 6.59−6.57 (m, 2H, phenyl) ppm) were observed by 1H NMR spectroscopy (100% conversion). Preparation of Cp‴2ThNC(PMes*)(Ph) (7). Method A. This compound was obtained as orange crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and PhCN (26 mg, 0.25 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 240 mg (89%). Mp: 204−206 °C dec. 1H NMR (C6D6): δ 7.48 (s, 2H, phenyl), 7.35 (s, 2H, ring CH), 7.01−6.94 (m, 5H, phenyl), 6.09 (s, 2H, ring CH), 1.84 (br s, 18H, C(CH3)3), 1.58 (s, 18H, C(CH3)3), 1.47 (s, 36H, C(CH3)3), 1.43 (s, 9H, C(CH3)3) ppm. 13C{1H} NMR (C6D6): δ 200.9 (d, JP−C = 50.7 Hz, CP), 155.7 (phenyl C), 148.4 (phenyl C), 147.3 (phenyl C), 141.3 (phenyl C), 139.2 (d, JP−C = 68.0 Hz, phenyl C), 137.8 (phenyl C), 129.3 (phenyl C), 128.5 (phenyl C), 127.4 (d, JP−C = 2.3 Hz, ring C), 126.5 (ring C), 125.4 (ring C), 120.5 (ring C), 115.5 (ring C), 38.9 (C(CH3)3), 34.9 (C(CH3)3), 34.6 (C(CH3)3), 34.4 (C(CH3)3), 33.8 (C(CH3)3), 33.7 (C(CH3)3), 33.2 (C(CH3)3), 29.0 (C(CH3)3) ppm. I


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Journal of the American Chemical Society P{1H} NMR (C6D6): δ 141.8 ppm. IR (KBr, cm−1): ν 2954 (s), 2904 (m), 2866 (m), 1584 (m), 1475 (m), 1460 (m), 1386 (s), 1359 (s), 1236 (m), 1022 (m), 813 (s). Anal. Calcd for C59H92NPTh: C, 65.71; H, 8.60; N, 1.30. Found: C, 65.98; H, 8.62; N, 1.32. Method B. NMR Scale. A C6D6 (0.3 mL) solution of PhCN (2.1 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 7 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of Cp‴2ThNC(PMes*)(C6H11) (8). Method A. This compound was obtained as orange crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and C6H11CN (27 mg, 0.25 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 217 mg (80%). Mp: 189−191 °C dec. 1H NMR (C6D6): δ 7.56 (d, J = 6.0 Hz, 2H, phenyl), 7.25 (d, J = 2.2 Hz, 2H, ring CH), 6.10 (d, J = 2.2 Hz, 2H, ring CH), 1.95 (s, 9H, C(CH3)3), 1.89 (s, 9H, C(CH3)3), 1.78 (m, 4H, CH2), 1.64 (s, 18H, C(CH3)3), 1.60 (s, 18H, C(CH3)3), 1.49 (s, 18H, C(CH3)3), 1.47 (s, 9H, C(CH3)3), 1.32 (m, 3H, CH and CH2), 1.07 (m, 4H, CH2) ppm. 13C{1H} NMR (C6D6): δ 212.7 (d, JP−C = 53.1 Hz, C P), 156.1 (d, JP−C = 27.0 Hz, phenyl C), 147.7 (phenyl C), 141.7 (phenyl C), 140.7 (d, JP−C = 68.9 Hz, phenyl C), 140.7 (ring C), 136.9 (ring C), 120.4 (d, JP−C = 11.5 Hz, ring C), 119.8 (ring C), 115.5 (ring C), 48.5 (CHCH2), 38.9 (C(CH3)3), 34.9 (C(CH3)3), 34.6 (C(CH3)3), 34.5 (C(CH3)3), 34.3 (C(CH3)3), 33.3 (C(CH3)3), 32.0 (C(CH3)3), 31.4 (CH2), 31.3 (CH2), 31.2 (CH2), 28.7 (C(CH3)3), 27.4 (C(CH3)3), 27.2 (C(CH3)3) ppm. 31P{1H} NMR (C6D6): δ 140.9 ppm. IR (KBr, cm−1): ν 2960 (s), 2928 (s), 2868 (s), 1595 (s), 1386 (s), 1361 (s), 1259 (s), 1091 (s), 1020 (s), 798 (s). Anal. Calcd for C59H98NPTh: C, 65.35; H, 9.11; N, 1.29. Found: C, 65.38; H, 9.12; N, 1.31. Method B. NMR Scale. A C6D6 (0.3 mL) solution of C6H11CN (2.2 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 8 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of Cp‴2ThNC(PMes*)(CMe3)·0.5C6H6 (9· 0.5C6H6). Method A. This compound was obtained as orange crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and Me3CCN (21 mg, 0.25 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 228 mg (83%). Mp: 157−159 °C dec. 1H NMR (C6D6): δ 7.56 (s, 2H, phenyl), 7.29 (s, 2H, ring CH), 7.15 (s, 3H, C6H6), 6.14 (s, 2H, ring CH), 2.01 (s, 9H, C(CH3)3), 1.96 (s, 9H, C(CH3)3), 1.65 (s, 18H, C(CH3)3), 1.60 (s, 18H, C(CH3)3), 1.50 (s, 18H, C(CH3)3), 1.42 (s, 9H, C(CH3)3), 1.05 (s, 9H, C(CH3)3) ppm. 13C{1H} NMR (C6D6): δ 208.9 (d, JP−C = 64.0 Hz, CP), 155.4 (phenyl C), 148.5 (phenyl C), 141.2 (d, JP−C = 63.1 Hz, phenyl C), 136.9 (phenyl C), 129.3 (ring C), 128.0 (C6H6), 125.6 (ring C), 120.7 (ring C), 119.2 (ring C), 115.9 (ring C), 45.8 (d, JP−C = 6.2 Hz, C(CH3)3), 39.3 (C(CH3)3), 39.1 (C(CH3)3), 35.0 (C(CH3)3), 34.8 (C(CH3)3), 34.5 (C(CH3)3), 34.3 (d, JP−C = 4.5 Hz, C(CH3)3), 33.3 (C(CH3)3), 31.8 (C(CH3)3), 29.6 (C(CH3)3), 28.9 (C(CH3)3), 27.0 (C(CH3)3) ppm. 31 1 P{ H} NMR (C6D6): δ 141.1 ppm. IR (KBr, cm−1): ν 2958 (s), 2906 (m), 1593 (m), 1477 (m), 1462 (m), 1388 (s), 1361 (s), 1259 (s), 1096 (s), 1020 (s), 800 (s). Anal. Calcd for C60H99NPTh: C, 65.67; H, 9.09; N, 1.28. Found: C, 65.68; H, 9.11; N, 1.30. Method B. NMR Scale. A C6D6 (0.3 mL) solution of Me3CCN (1.6 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 9 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of [Cp‴2ThNC(PMes*)(3-NCPh)]2·2C6H6 (10·2C6H6). Method A. This compound was obtained as orange crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and m-Ph(CN)2 (32 mg, 0.25 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 254 mg

(86%). Mp: 230−232 °C dec. 1H NMR (C6D6): δ 8.15 (s, 1H, phenyl), 7.41 (s, 2H, phenyl), 7.30 (d, J = 7.1 Hz, 1H, phenyl), 7.15 (s, 2 x 6H, C6H6), 7.10 (s, 2H, ring CH), 6.73 (t, J = 7.7 Hz, 1H, phenyl), 6.51 (d, J = 7.5 Hz, 1H, phenyl), 6.33 (s, 2H, ring CH), 1.85 (s, 18H, C(CH3)3), 1.69 (s, 18H, C(CH3)3), 1.63 (s, 18H, C(CH3)3), 1.53 (s, 18H, C(CH3)3), 1.35 (s, 9H, C(CH3)3) ppm. 13C{1H} NMR (C6D6): δ 196.2 (d, JP−C = 61.7 Hz, CP), 155.8 (phenyl C), 149.8 (phenyl C), 148.4 (phenyl C), 143.1 (phenyl C), 141.9 (phenyl C), 141.7 (phenyl C), 139.9 (d, JP−C = 74.5 Hz, phenyl C), 135.7 (phenyl C), 133.1 (phenyl C), 131.9 (phenyl C), 129.3 (ring C), 128.0 (C6H6), 125.6 (ring C),121.3 (ring C), 116.8 (ring C), 114.6 (ring C), 105.5 (PhCN), 39.0 (C(CH3)3), 35.4 (C(CH3)3), 34.9 (C(CH3)3), 34.4 (C(CH3)3), 33.9 (C(CH3)3), 33.8 (C(CH3)3), 32.9 (C(CH3)3) ppm; other carbons overlapped. 31P{1H} NMR (C6D6): δ 151.3 ppm. IR (KBr, cm−1): ν 2960 (s), 2904 (s), 2868 (m), 2228 (m), 1591 (m), 1386 (s), 1359 (s), 806 (s). Anal. Calcd for C132H194N4P2Th2: C, 67.09; H, 8.28; N, 2.37. Found: C, 67.08; H, 8.27; N, 2.30. Method B. NMR Scale. A C6D6 (0.3 mL) solution of m-Ph(CN)2 (2.6 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 10 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of [Cp‴2ThNC(PMes*)(4-NCPh)]2·3C6H6 (11·3C6H6). A benzene (5 mL) solution of p-Ph(CN)2 (32 mg, 0.25 mmol) was added to a benzene (10 mL) solution of Cp‴2Th PMes* (3; 244 mg, 0.25 mmol) without stirring at room temperature. After this mixture was kept at room temperature overnight without stirring, green crystals were isolated from the solution, which were identified as 11·3C6H6 by X-ray diffraction analysis. Yield: 287 mg (94%). Mp: >300 °C. IR (KBr, cm−1): ν 2962 (s), 2244 (m), 1593 (m), 1400 (s), 1384 (s), 1261 (s), 1093 (s), 1020 (s), 800 (s). Anal. Calcd for C138H200N4P2Th2: C, 67.90; H, 8.26; N, 2.30. Found: C, 67.98; H, 8.27; N, 2.32. This compound was insoluble in common (deuterated) solvents such as pyridine, THF, toluene, and CD2Cl2, which prevented its characterization by NMR spectroscopy. Preparation of Cp‴2Th[NC(N)(C6H4CPMes*)]·C6H6 (12· C6H6). Method A. This compound was obtained as orange crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and oPh(CN)2 (32 mg, 0.25 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 248 mg (84%). Mp: 272−274 °C dec. 1H NMR (C6D6): δ 7.89 (d, J = 7.4 Hz, 1H, phenyl), 7.71 (s, 2H, phenyl), 7.15 (s, 6H, C6H6), 7.02 (t, J = 7.3 Hz, 1H, phenyl), 6.89 (t, J = 7.5 Hz, 1H, phenyl), 6.37 (d, J = 3.3 Hz, 2H, ring CH), 6.23 (d, J = 3.3 Hz, 2H, ring CH), 5.28 (d, J = 7.9 Hz, 1H, phenyl), 1.73 (s, 18H, C(CH3)3), 1.65 (s, 18H, C(CH3)3), 1.57 (s, 18H, C(CH3)3), 1.46 (s, 9H, C(CH3)3), 1.45 (s, 18H, C(CH3)3) ppm. 13C{1H} NMR (C6D6): δ 188.2 (d, JP−C = 33.1 Hz, CP), 157.6 (d, JP−C = 7.5 Hz, CN), 156.4 (phenyl C), 150.8 (phenyl C), 144.2 (phenyl C), 143.2 (phenyl C), 143.1 (phenyl C), 142.2 (phenyl C), 136.1 (d, JP−C = 54.3 Hz, phenyl C), 134.0 (d, JP−C = 7.3 Hz, phenyl C), 130.3 (d, JP−C = 2.2 Hz, phenyl C), 129.3 (phenyl C), 128.0 (C6H6), 125.3 (d, JP−C = 3.8 Hz, ring C), 122.4 (ring C), 121.9 (ring C), 116.6 (ring C), 116.1 (ring C), 38.8 (C(CH3)3), 35.3 (C(CH3)3), 35.0 (C(CH3)3), 34.8 (C(CH3)3), 34.6 (C(CH3)3), 34.0 (C(CH3)3), 33.7 (C(CH3)3), 33.1 (d, JP−C = 6.9 Hz, C(CH3)3), 32.2 (C(CH3)3), 31.8 (C(CH3)3) ppm. 31P{1H} NMR (C6D6): δ 139.0 ppm. IR (KBr, cm−1): ν 2960 (s), 2906 (s), 2868 (s), 1591 (m), 1527 (s), 1462 (s), 1390 (s), 1359 (s), 1095 (s), 1018 (s), 821 (s). Anal. Calcd for C66H97N2PTh: C, 67.09; H, 8.28; N, 2.37. Found: C, 67.18; H, 8.27; N, 2.32. Method B. NMR Scale. A C6D6 (0.3 mL) solution of o-Ph(CN)2 (2.6 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 12 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of Cp‴2Th[C(PMes*)N(SiMe3)]·1.5C6H6 (13· 1.5C6H6). Method A. This compound was obtained as yellow crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and Me3SiNC (25 mg, 0.25 mmol) in toluene (15 mL) at

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Journal of the American Chemical Society

146.3 (phenyl C), 144.2 (phenyl C), 137.9 (phenyl C), 130.2 (phenyl C), 122.7 (ring C), 119.4 (ring C), 116.1 (ring C), 39.1 (CH3), 34.7 (C(CH3)3), 34.6 (C(CH3)3), 34.4 (C(CH3)3), 33.0 (C(CH3)3), 32.2 (C(CH3)3), 29.5 (C(CH3)3), 23.0 (C(CH3)3), 22.8 (C(CH3)3) ppm. 31 1 P{ H} NMR (C6D6): δ 66.5 ppm. IR (KBr, cm−1): ν 2958 (s), 2924 (s), 1586 (s), 1478 (s), 1466 (s), 1389 (s), 1360 (s), 1281 (s), 1238 (s), 999 (s), 812 (s). Anal. Calcd for C61H96NPTh: C, 66.22; H, 8.75; N, 1.27. Found: C, 66.12; H, 8.82; N, 1.23. Method B. NMR Scale. A C6D6 (0.3 mL) solution of 2,6Me2PhNC (2.6 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 15 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of Cp‴2Th(NPMes*)(N3) (16). Method A. This compound was obtained as purple crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and Ph3CN3 (143 mg, 0.50 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 191 mg (74%). Mp: 195−197 °C dec. 1H NMR (C6D6): δ 7.39 (s, 2H, phenyl), 6.62 (s, 4H, ring CH), 1.66 (s, 18H, C(CH3)3), 1.53 (s, 18H, C(CH3)3), 1.45 (s, 18H, C(CH3)3), 1.35 (s, 9H, C(CH3)3), 1.34 (s, 18H, C(CH3)3) ppm. 13 C{1H} NMR (C6D6): δ 153.8 (phenyl C), 150.0 (phenyl C), 145.1 (d, JP−C = 37.1 Hz, phenyl C), 144.5 (phenyl C), 122.3 (ring C), 117.6 (ring C), 115.5 (ring C), 38.4 (C(CH3)3), 35.4 (C(CH3)3), 35.3 (C(CH3)3), 35.0 (C(CH3)3), 34.9 (C(CH3)3), 34.7 (C(CH3)3), 34.2 (C(CH3)3), 33.9 (C(CH3)3), 32.7 (C(CH3)3), 31.5 (C(CH3)3) ppm. 31P{1H} NMR (C6D6): δ 501.6 ppm. IR (KBr, cm−1): ν 2958 (s), 2904 (s), 2099 (s), 1591 (s), 1462 (s), 1390 (s), 1371 (s), 1236 (s), 1141 (s), 1120 (s), 823 (s). Anal. Calcd for C52H87N4PTh: C, 60.56; H, 8.50; N, 5.43. Found: C, 60.60; H, 8.52; N, 5.38. Method B. NMR Scale. A C6D6 (0.3 mL) solution of Ph3CN3 (11 mg, 0.04 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 16 along with those of Ph3CCH(C2H2)2CCPh2 (1H NMR (C6D6): δ 7.29 (m, 3H, phenyl), 7.00 (m, 22H, phenyl), 6.43 (d, J = 9.8 Hz, 2H, CH), 5.92 (d, J = 9.8 Hz, 2H, CH), 4.92 (s, 1H, CH))13 were observed by 1H NMR spectroscopy (100% conversion) after the sample was kept at room temperature overnight. Reaction of Cp‴2ThPMes* (3) with Ph3CN3. NMR Scale. A C6D6 (0.2 mL) solution of Ph3CN3 (5.7 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.3 mL). Resonances of 16 along with those of unreacted 3 and Ph3CCH(C2H2)2CCPh2 were observed by 1H NMR spectroscopy (50% conversion based on 3) after the sample was kept at room temperature overnight. Preparation of Cp‴2ThNSiMe3 (17). Method A. This compound was obtained as colorless crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and Me3SiN3 (29 mg, 0.25 mmol) in toluene (15 mL) at room temperature and recrystallization from an n-hexane solution by a procedure similar to that used in the synthesis of 4. Yield: 163 mg (83%). 1H NMR (C6D6): δ 7.15 (s, 4H, ring CH), 1.53 (s, 36H, (CH3)3C), 1.51 (s, 18H, (CH3)3C), 0.26 (s, 9H, (CH3)3Si). These spectroscopic data agreed with those reported in the literature.13 Method B. NMR Scale. A C6D6 (0.3 mL) solution of Me3SiN3 (2.3 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 17 along with those of 3,3-Me2-5,7-tBu2C8H5P (18) (1H NMR (C6D6): δ 7.46 (dd, J = 3.8, 1.5 Hz, 2H, phenyl), 4.39 (ddd, J = 181.6, 11.9, 7.9 Hz, 1H, PH), 1.59 (d, J = 3.6 Hz, 1H CH2), 1.56 (s, 9H, (CH3)3C), 1.34 (s, 3H, (CH3), 1.31 (s, 9H, (CH3)3C), 1.29 (d, J = 3.6 Hz, 1H CH2), 1.11 (s, 3H, (CH3) ppm. 31P{1H} NMR (C6D6): δ −79.5 ppm)18 were observed by NMR spectroscopy (100% conversion in 10 min). X-ray Crystallography. Single-crystal X-ray diffraction measurements were carried out on a Bruker Smart APEX II CCD or on a Rigaku Saturn CCD diffractometer at 100(2) K using graphitemonochromated Mο Kα radiation (λ = 0.71073 Å) or Cu Kα radiation (λ = 1.54184 Å). An empirical absorption correction was

room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 232 mg (78%). Mp: 155−157 °C dec. 1H NMR (C6D6): δ 7.55 (d, J = 7.0 Hz, 2H, phenyl), 7.15 (s, 9H, C6H6), 6.62 (d, J = 2.9 Hz, 1H, ring CH), 6.49 (d, J = 3.1 Hz, 1H, ring CH), 6.33 (d, J = 3.0 Hz, 1H, ring CH), 6.23 (d, J = 3.1 Hz, 1H, ring CH), 2.02 (9H, C(CH3)3), 1.98 (9H, C(CH3)3), 1.70 (9H, C(CH3)3), 1.66 (9H, C(CH3)3), 1.52 (9H, C(CH3)3), 1.51 (9H, C(CH3)3), 1.46 (s, 9H, C(CH3)3), 1.34 (s, 9H, C(CH3)3), 1.33 (s, 9H, C(CH3)3), 0.07 (s, 9H, Si(CH3)3) ppm. 13 C{1H} NMR (C6D6): δ 249.9 (d, JP−C = 176.4 Hz, ThCP), 154.7 (d, JP−C = 76.3 Hz, phenyl C), 154.1 (phenyl C), 152.8 (phenyl C), 146.7 (phenyl C), 143.9 (ring C), 143.6 (ring C), 142.4 (ring C), 140.3 (d, JP−C = 5.5 Hz, ring C), 136.8 (ring C), 129.3 (ring C), 128.0 (C6H6), 121.1 (ring C), 116.2 (ring C), 115.1 (d, JP−C = 7.0 Hz, ring C), 114.8 (ring C), 39.4 (d, JP−C = 2.2 Hz, C(CH3)3), 39.0 (C(CH3)3), 35.6 (C(CH3)3), 35.4 (C(CH3)3), 35.0 (C(CH3)3), 34.9 (C(CH3)3), 34.9 (d, JP−C = 10.7 Hz, C(CH3)3), 34.6 (C(CH3)3), 34.5 (C(CH3)3), 34.4 (C(CH3)3), 34.3 (C(CH3)3), 33.6 (C(CH3)3), 33.3 (C(CH3)3), 32.7 (C(CH3)3), 31.7 (C(CH3)3), 28.8 (C(CH3)3), 28.1 (d, JP−C = 6.7 Hz, Si(CH3)3) ppm. 31P{1H} NMR (C6D6): δ 76.2 ppm. IR (KBr, cm−1): ν 2955 (m), 2904 (m), 1398 (s), 1386 (s), 1360 (s), 1265 (s), 1238 (s), 1095 (m), 1020 (m), 810 (s). Anal. Calcd for C65H105NPSiTh: C, 65.51; H, 8.88; N, 1.18. Found: C, 65.58; H, 8.87; N, 1.12. Method B. NMR Scale. A C6D6 (0.3 mL) solution of Me3SiNC (2.0 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 13 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of Cp‴2Th[C(PMes*)N(C6H11)]·1.5C6H6 (14· 1.5C6H6). Method A. This compound was obtained as orange crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and C6H11NC (27 mg, 0.25 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 240 mg (80%). Mp: 194−196 °C dec. 1H NMR (C6D6): δ 7.56 (s, 1H, phenyl), 7.52 (s, 1H, phenyl), 7.15 (s, 9H, C6H6), 6.59 (s, 1H, ring CH), 6.46 (s, 1H, ring CH), 6.31 (s, 2H, ring CH), 3.41 (t, J = 9.7 Hz, 1H, NCH), 2.05 (s, 9H, C(CH3)3), 2.00 (s, 9H, C(CH3)3), 1.68 (br s, 18H, C(CH3)3), 1.54 (s, 22H, CH2 and C(CH3)3), 1.47 (s, 9H, C(CH3)3), 1.37 (s, 18H, C(CH3)3), 1.23 (m, 4H, CH2), 1.01 (m, 2H, CH2) ppm. 13C{1H} NMR (C6D6): δ 240.1 (d, JP−C = 164.6 Hz, C P), 155.7 (phenyl C), 148.5 (d, JP−C = 148.5 Hz, phenyl C), 146.6 (phenyl C), 129.3 (phenyl C), 128.0 (C6H6), 127.3 (ring C), 125.6 (ring C), 121.2 (ring C), 120.2 (ring C), 115.3 (ring C), 65.9 (d, JP−C = 9.5 Hz, NCH), 39.7 (d, JP−C = 2.2 Hz, C(CH3)3), 39.3 (C(CH3)3), 36.8 (C(CH3)3), 36.7 (C(CH3)3), 35.4 (C(CH3)3), 35.0 (C(CH3)3), 34.9 (C(CH3)3), 34.8 (C(CH3)3), 34.7 (C(CH3)3), 34.6 (C(CH3)3), 31.9 (C(CH3)3), 28.5 (C(CH3)3), 26.7 (CH2), 26.5 (CH2), 26.2 (CH2) ppm. 31P{1H} NMR (C6D6): δ 58.4 ppm. IR (KBr, cm−1): ν 2956 (s), 2931 (s), 1462 (m), 1388 (s), 1359 (w), 1097 (m), 1022 (m), 810 (s). Anal. Calcd for C68H107NPTh: C, 67.97; H, 8.98; N, 1.17. Found: C, 67.88; H, 8.89; N, 1.13. Method B. NMR Scale. A C6D6 (0.3 mL) solution of C6H11NC (2.2 mg, 0.02 mmol) was slowly added to a J. Young NMR tube charged with Cp‴2ThPMes* (3; 20 mg, 0.02 mmol) and C6D6 (0.2 mL). Resonances of 14 were observed by 1H NMR spectroscopy (100% conversion in 10 min). Preparation of Cp‴2Th[C(PMes*)N(2,6-Me2Ph)] (15). Method A. This compound was obtained as orange crystals from the reaction of Cp‴2ThPMes* (3; 244 mg, 0.25 mmol) and 2,6Me2PhNC (33 mg, 0.25 mmol) in toluene (15 mL) at room temperature and recrystallization from a benzene solution by procedure similar to that used in the synthesis of 4. Yield: 234 mg (86%). Mp: 138−140 °C dec. 1H NMR (C6D6): δ 7.15 (s, 2H, phenyl), 6.77−6.69 (m, 3H, phenyl), 6.43 (s, 4H, ring CH), 2.19 (s, 6H, CH3), 1.83 (br s, 18H, C(CH3)3), 1.51 (s, 18H, C(CH3)3), 1.50 (s, 36H, C(CH3)3), 1.46 (s, 9H, C(CH3)3) ppm. 13C{1H} NMR (C6D6): δ 243.1 (d, JP−C = 170.6 Hz, CP), 154.2 (phenyl C), 153.9 (phenyl C), 153.8 (phenyl C), 148.8 (d, JP−C = 111.5 Hz, phenyl C), K


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Journal of the American Chemical Society applied using the SADABS program.19 All structures were solved by direct methods and refined by full-matrix least-squares on F2 using the SHELXL program package.20 All of the hydrogen atoms were geometrically fixed using the riding model. The crystals of 4 and 16 were twinned, and one domain was used for the refinement resulting in high residual electron density observed. Moreover, the crystal of 10 was highly twinned, and therefore, ISOR restraints were applied to all C and N atoms. The crystal data and experimental data for 2−16 and 19 are summarized in the Supporting Information. Selected bond distances and angles are listed in Table 1. Computational Methods. All calculations were carried out with the Gaussian 09 program (G09),21 employing the B3PW91 functional, plus a polarizable continuum model (PCM) (denoted as B3PW91-PCM), with standard 6-31G(d) basis set for C, H, N, S, and P elements and a quasi-relativistic 5f-in-valence effective-core potential (ECP60MWB) treatment with 60 electrons in the core region for Th and the corresponding optimized segmented ((14s13p10d8f6g)/[10s9p5d4f3g]) basis set for the valence shells of Th22 to fully optimize the structures of reactants, complexes, transition state, intermediates, and products and also to mimic the experimental toluene−solvent conditions (dielectric constant ε = 2.379). All stationary points were subsequently characterized by vibrational analyses, from which their respective zero-point (vibrational) energy were extracted and used in the relative energy determinations; in addition, frequency calculations were also performed to ensure that the reactant, complex, intermediate, product, and transition-state structures resided at minima and first order saddle points, respectively, on their potential energy hypersurfaces.

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Over. Acc. Chem. Res. 1997, 30, 445−451. (b) Stephan, D. W. Zirconium-Phosphorus Chemistry: Strategies in Syntheses, Reactivity, Catalysis, and Utility. Angew. Chem., Int. Ed. 2000, 39, 314−329. (c) Mathey, F. Phospha-Organic Chemistry: Panorama and Perspectives. Angew. Chem., Int. Ed. 2003, 42, 1578−1604. (d) Greenberg, S.; Stephan, D. W. Stoichiometric and catalytic activation of P-H and P-P bonds. Chem. Soc. Rev. 2008, 37, 1482−1489. (e) Waterman, R. Metal-phosphido and-phosphinidene complexes in P-E bondforming reactions. Dalton Trans 2009, 18−26. (f) Weber, L. Phosphaand Arsaalkenes RE = C(NMe 2 ) 2 (E= P, As) as Novel Phosphinidene-and Arsinidene-Transfer Reagents. Eur. J. Inorg. Chem. 2007, 2007, 4095−4117. (g) Aktas, H.; Slootweg, J. C.; Lammertsma, K. Nucleophilic Phosphinidene Complexes: Access and Applicability. Angew. Chem., Int. Ed. 2010, 49, 2102−2113. (h) García, M. E.; García-Vivó, D.; Ramos, A.; Ruiz, M. A. Phosphinidene-bridged binuclear complexes. Coord. Chem. Rev. 2017, 330, 1−36. (2) For selected papers on group 4 and 5 metal phosphinidene complexes, see: (a) Hou, Z.; Stephan, D. W. Generation and Reactivity of the First Mononuclear Early Metal Phosphinidene Complex, Cp*2Zr = P(C6H2Me3-2,4,6). J. Am. Chem. Soc. 1992, 114, 10088−10089. (b) Cummins, C. C.; Schrock, R. R.; Davis, W. M. Phosphinidenetantalum(V) Complexes of the Type [(N3N)Ta = PR] as Phospha-Wittig Reagents. Angew. Chem., Int. Ed. Engl. 1993, 32, 756−759. (c) Hou, Z.; Breen, T. L.; Stephan, D. W. Formation and Reactivity of the Early Metal Phosphides and Phosphinidenes Cp*2Zr = PR, Cp*2Zr(PR)2, and Cp*2Zr(PR)3. Organometallics 1993, 12, 3158−3167. (d) Ho, J.; Rousseau, R.; Stephan, D. W. Synthesis, Structure, and Bonding in Zirconocene Primary Phosphido (PHR−), Phosphinidene (PR2‑), and Phosphide (P3‑) Derivatives. Organometallics 1994, 13, 1918−1926. (e) Bonanno, J. B.; Wolczanski, P. T.; Lobkovsky, E. B. Arsinidene, Phosphinidene, and Imide Formation via 1,2-H2-Elimination from (silox)3HTaEHPh (E = N, P, As): Structures of (silox)3Ta = EPh (E = P, As). J. Am. Chem. Soc. 1994, 116, 11159− 11160. (f) Breen, T. L.; Stephan, D. W. Phosphinidene Transfer Reactions of the Terminal Phosphinidene Complex Cp2Zr(PC6H22,4,6-t-Bu3)(PMe3). J. Am. Chem. Soc. 1995, 117, 11914−11921. (g) Urnezius, E.; Lam, K.-C.; Rheingold, A. L.; Protasiewicz, J. D. Triphosphane formation from the terminal zirconium phosphinidene complex [Cp2Zr = PDmp(PMe3)](Dmp = 2,6-Mes2C6H3) and crystal structure of DmpP(PPh2)2. J. Organomet. Chem. 2001, 630, 193−197. (h) Basuli, F.; Tomaszewski, J.; Huffman, J. C.; Mindiola, D. J. FourCoordinate Phosphinidene Complexes of Titanium Prepared by α-HMigration: Phospha-Staudinger and Phosphaalkene-Insertion Reactions. J. Am. Chem. Soc. 2003, 125, 10170−10171. (i) Basuli, F.; Bailey, B. C.; Huffman, J. C.; Baik, M.-H.; Mindiola, D. J. Terminal and Four-Coordinate Vanadium(IV) Phosphinidene Complexes. A Pseudo Jahn-Teller Effect of Second Order Stabilizing the V-P Multiple Bond. J. Am. Chem. Soc. 2004, 126, 1924−1925. (j) Bailey, B. C.; Huffman, J. C.; Mindiola, D. J.; Weng, W.; Ozerov, O. V. Remarkably Stable Titanium Complexes Containing Terminal Alkylidene, Phosphinidene, and Imide Functionalities. Organometallics 2005, 24, 1390−1393. (k) Zhao, G.; Basuli, F.; Kilgore, U. J.; Fan, H.; Aneetha, H.; Huffman, J. C.; Wu, G.; Mindiola, D. J. Neutral and Zwitterionic Low-Coordinate Titanium Complexes Bearing the Terminal Phosphinidene Functionality. Structural, Spectroscopic, Theoretical, and Catalytic Studies Addressing the Ti-P Multiple Bond. J. Am. Chem. Soc. 2006, 128, 13575−13585. (l) Kilgore, U. J.; Fan, H.; Pink, M.; Urnezius, E.; Protasiewicz, J. D.; Mindiola, D. J. Phosphinidene group-transfer with a phospha-Wittig reagent: a new entry to transition metal phosphorus multiple bonds. Chem. Commun. 2009, 4521−4523. (m) Waterman, R.; Tilley, T. D. Terminal hafnium phosphinidene complexes and phosphinidene ligand exchange. Chem. Sci. 2011, 2, 1320−1325. (n) Graham, T. W.; Udachin, K. A.; Zgierski, M. Z.; Carty, A. J. Synthesis and Structural Characterization of the First Thermally Stable, Neutral, and Electrophilic Phosphinidene Complexes of Vanadium. Organometallics 2011, 30, 1382−1388. (o) Rankin, M. A.; Cummins, C. C. Terminal phosphinidene formation via tantalaziridine complexes. Dalton Trans 2012, 41,

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.8b09746. Reactivity of thorium imido metallocenes; crystal parameters for compounds 2−16 and 19; computational studies (PDF) X-ray crystallographic data for compounds 2−16 and 19 (CIF) Cartesian coordinates of all stationary points optimized at the B3PW91-PCM level (XYZ)

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AUTHOR INFORMATION

Corresponding Authors

*[email protected] *[email protected] *[email protected] ORCID

Guohua Hou: 0000-0002-3571-456X Guofu Zi: 0000-0002-7455-460X Marc D. Walter: 0000-0002-4682-8749 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (Grant Nos. 21871029, 21472013, 21573021, 21672024) and the Deutsche Forschungsgemeinschaft (DFG) through the Heisenberg program (WA 2513/6 and WA 2513/8).

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A Base-Free Terminal Actinide Phosphinidene Metallocene: Synthesis

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