Probing Donor–Acceptor Interactions in peri-Substituted

Nov 26, 2014 - Diphenylphosphinoacenaphthyl−Element Dichlorides of Group 13 .... by members of the heavier group 1313 and 15 elements14 and prepared...
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Probing Donor−Acceptor Interactions in peri-Substituted Diphenylphosphinoacenaphthyl−Element Dichlorides of Group 13 and 15 Elements Emanuel Hupf,† Enno Lork,† Stefan Mebs,‡ Lilianna Chęcińska,*,§ and Jens Beckmann*,† †

Institut für Anorganische Chemie, Universität Bremen, Leobener Straße, 28359 Bremen, Germany Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany § Department of Theoretical and Structural Chemistry, University of Lodz, Pomorska 163/165, 90-236 Lodz, Poland ‡

S Supporting Information *

ABSTRACT: Transmetalation reactions of ArLi with ECl3 (E = Al, P, In, Bi) and ArSnBu3 with ECl3 (E = B, Ga, Tl, As, Sb) gave rise to the formation of peri-substituted diphenylphosphinoacenaphthyl−element dichlorides ArECl2 (Ar = 6-Ph2PAce-5-), which were characterized by multinuclear NMR spectroscopy and X-ray crystallography. DFT calculations were performed on the compounds at relaxed gas-phase molecular geometries. For the series ArECl2 containing group 13 elements one structure type featuring regular Lewis pairs with short E−P peri distances (E = B, Al, Ga, In, Tl) was observed. For the series ArECl2 containing group 15 elements two structural types with very different peri distances (E = P, As, Sb, Bi) were found. The computed electron and pair densities were topologically analyzed according to the atoms-in-molecules (AIM) and electron localizability indicator (ELI-D) spacepartitioning schemes, which facilitates the characterization of the peri interactions and also allows for monitoring minute electronic effects induced by different substituents and/or spatial arrangements.

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INTRODUCTION

Our group described 1-diphenylphosphino-8-naphthyl-dimesitylborane (1-(Ph2P)-8-(Mes2B)-Nap, IIIa) and the closely related 5-diphenylphosphino-6-acenaphthyl-dimesitylborane (5-(Ph2P)-6-(Mes2B)-Ace, IIIb), possessing the same substituents at the B and P atoms with albeit quite different B−P peri distances of 2.162(2) and 3.050(3) Å, which is due to the fact that the naphthyl framework accommodates a higher degree of conformational flexibility in comparison to the rigid acenaphthyl framework.6 Wang et al. also conducted an experimental study of IIIa and put forward DFT calculations of both the regular and frustrated forms of IIIa, which appear to have similar energies.7 Unlike 1,8-bis(diphenylphosphino)naphthalene (1,8-(Ph2P)2-Nap, IV), which possesses a rather long P−P peri distance of 3.052(2) Å,8 the related 5dichlorophosphino-6-diisopropylphosphinoacenaphthene (5(Cl2P)-6-(i-Pr2P)-Ace, V) recently reported by Kilian et al. gives rise to a short peri distance of 2.257(1) Å that is indicative of a strongly attractive donor−acceptor interaction between the P atoms.9 Interestingly, the spatial arrangement of the PCl2 group adopts a T-shaped arrangement in the crystal structure with two uneven P−Cl bond lengths of 2.275(1) and 2.488(2) Å, pointing to an ionic bond situation and the influence of crystal-packing effects. Reduction of V with BH3·SMe2 and

Donor−acceptor interactions between phosphines and maingroup elements have received tremendous interest,1 which has been recently fueled by the discovery that bulky phosphines and boranes may form frustrated Lewis pairs (FLPs) that are able to activate small molecules, such as dihydrogen and carbon dioxide, without the aid of a transition metal.2 Peri-substituted (ace)naphthylphosphinoboranes comprise regular Lewis pairs or FLPs depending on the nature of the substituents attached to the B and P atoms in 1,8- and 5,6-positions (Chart 1). Sasamori and Tokitoh et al.3 communicated two 1-dichlorophosphino-8-naphthyl-diarylboranes 1-(Cl2P)-8-(R2B)-Nap (Ia, R = 3,5-t-Bu2C6H3; Ib, R = Mes) and later disclosed structural data.4 Reduction of Ia,b with Mg proceeded with aryl group migration and gave rise to the formation of unique phosphaboranes.3 Miqueu and Bourissou et al.5 reported on the three 1-diisopropylphosphino-8-naphthyl-diorganoboranes 1-(iPr2P)-8-(R2B)-Nap (IIa, R = Mes; IIb, R = Cy; IIc, R2 = Flu; Flu = 2,2′-biphenylene), which were structurally elucidated. The different P−B peri distances (Å) of 2.108(2) (Ia), 2.892(2) (Ib), 2.173(3) (IIa), 2.076(2) (IIb), and 2.011(2) (IIc) demonstrate that the bulk and electronic effect of the substituents attached to the B and P atoms determines the nature of the peri interaction: namely, if it is dominated by attractive or repulsive forces. © XXXX American Chemical Society

Received: October 11, 2014

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Chart 1. 1,8- and 5,6-Disubstituted Phosphinonaphthalenes and Phosphinoacenaphthenes of Groups 13 and 15 and Related peri Distances

Scheme 1. Synthesis of 1−9

subsequent treatment with Me 2 NH provided the first phosphanylidene phosphorane having a two-coordinated P atom,10 which shows an interesting coordination chemistry.11 During the course of this work a heavier congener of V, namely 5-dichloroarseno-6-diisopropylphosphinoacenaphthene (5(Cl2As)-6-(i-Pr2P)-Ace, VI), was reported by the same group, which also comprises a short As−P peri distance of 2.257(1) Å.12 Compound VI is the starting material for the preparation of a unique arsanylidine phosphorane and rare cyclooligoarsines. We have now extended these compound classes by members of the heavier group 1313 and 15 elements14 and prepared an entire series of peri-substituted diphenylphosphinoacenaphthyl−element dichlorides 5-(Cl2E)-6-(Ph2P)-Ace (1, E = B; 2, E = Al; 3, E = Ga; 4, E = In, 5, E = Tl; 6, E = P; 7, E = As; 8, E = Sb; 9 = Bi) with the aim of comparing their molecular and electronic structures in the solid state and gas phase. As in our previous study,6 we utilized real-space bonding indicators (RSBIs) obtained from density functional theory (DFT) calculations and topological analysis of the computed electron and pair densities according to the atoms-in-molecules (AIM)15 and electron localizability indicator (ELI-D)16 spacepartitioning schemes, respectively, which provide a set of topological and integrated bonding and atomic properties. By definition of surfaces of zero electronic flux, AIM generates atomic basins as well as a topological pattern which can be interpreted as the molecular structure. For “ambiguous through-space” peri interactions this approach may unravel

whether or not a direct bond path is present. ELI-D nicely complements the AIM approach in that basins of paired electrons are generated. Hence, bonding electron pairs become distinguishable from lone pairs, which is particularly useful for the assignment of the bond situation: e.g., a polar covalent P−E bond vs a coordinative P−E contact. Finally, both topological methods can be combined, providing the information on how the electron density (ED) of a bonding ELI-D basin is shared between the adjacent AIM atoms which constitute the bond. The combination of these methods give rise to the so-called Raub−Jansen index (RJI),17 which adopts for homopolar bonds values of 50%. The RJI becomes larger than 50% for polarcovalent interactions and larger than 95% for coordinative bonds.6

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RESULTS AND DISCUSSION Synthetic Aspects. For the preparation of the perisubstituted diphenylphosphinoacenaphthyl−element dichlorides two transmetalation reagents with different reactivities were used. The reaction of the bench-stable, rather mild ArSnBu3 (Ar = 6-Ph2P-Ace-5-)18 with BCl3, GaCl3, TlCl3 (freshly prepared from TlCl and gaseous Cl2),19 AsCl3, and SbCl3 at room temperature afforded the monosubstituted products ArECl2 (1, E = B; 3, E = Ga; 5, E = Tl; 7, E = As; 8, E = Sb) and Bu3SnCl, which were separated easily (Scheme 1). Multiple substitutions were not observed. No reaction of ArSnBu3 with AlCl3 and PCl3 occurred. The reaction of B

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Figure 1. Molecular structures of 1−5 showing 30% probability ellipsoids and the crystallographic numbering scheme.

ArSnBu3 with InCl3 and BiCl3 gave several products that were difficult to separate. One of the products in the reaction with BiCl3 could be assigned to ArBu2SnCl on the basis of the 31P NMR signal at δ −31.1 ppm that showed indicative tin satellites (J(31P-119/117Sn) = 595/569 Hz). The rational synthesis of

ArBu2SnCl is presented in the Supporting Information. Apparently, in these cases the Sn−C bond cleavage was not selective. Whenever ArSnBu3 was not suitable, the substantially more reactive aryllithium ArLi (prepared in situ from ArBr20 with n-butyllithium and N,N,N′,N′-tetramethylethylenediamine C

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Figure 2. Molecular structures of 2a,b showing 30% probability ellipsoids and the crystallographic numbering scheme.

Figure 3. Molecular structures of 6−9 showing 30% probability ellipsoids and the crystallographic numbering scheme.

(TMEDA)) was used as transmetalation reagent. Thus, the reaction of ArLi with an excess of AlCl3, PCl3, InCl3, and BiCl3 produced the monosubstituted products ArECl2 (2, E = Al; 4, E = In; 6, E = P; 9, E = Bi) at −78 °C (Scheme 1); however, multiple substitution had to be avoided by a careful choice of

the reaction conditions. In order to obtain the monosubstituted product ArAlCl2 (2), the aryllithium ArLi had to be added slowly to an excess of 5 equiv of AlCl3. The reaction of ArLi with 1 equiv of AlCl3 at −78 °C provided predominately the disubstituted product Ar2AlCl (2a), whereas the reversed order D

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Table 1. Selected Bond Parameters (Å and deg) of 1−9 1 (E = B)

E−Cl1 E−Cl2 E−C10 C10−E1−Cl1 C10−E1−Cl2 Cl1−E1−Cl2 P(1)···E(1) E(1)−C(10)−C(19) C(10)−C(19)−C(18) P(1)−C(18)−C(19) ∑ of bay angles splay anglea C(20)−P(1)−C(30) P(1) E(1) C(13)−C(14)−C(19)−C(18) C(15)−C(14)−C(19)−C(10)

E−Cl1 E−Cl2 E−C10 C10−E1−Cl1 C10−E1−Cl2 Cl1−E1−Cl2 P(1)···E(1) E(1)−C(10)−C(19) C(10)−C(19)−C(18) P(1)−C(18)−C(19) ∑ of bay angles splay anglea C(20)−P(1)−C(30) P(1) E(1) C(13)−C(14)−C(19)−C(18) C(15)−C(14)−C(19)−C(10)

2 (E = Al) Bond Lengths and Angles 1.842(2) 2.1367(5) 1.870(2) 2.1261(5) 1.801(2) 1.960(1) 116.9(2) 119.14(4) 110.1 (1) 116.04(4) 110.5(1) 111.59(2) peri Region Distances 2.040(2) 2.4305(5) peri Region Bond Angles 113.5(3) 114.25(8) 122.7(2) 125.6(2) 107.5(2) 116.20(8) 343.7(7) 356.1(5) −16.3(7) −3.9(5) 107.8(1) 106.4(1) Out-of-Plane Displacementb 0.0671(5) 0.0475(3) 0.219(3) 0.2688(4) Central Acenaphthene Ring Torsion −178.6(3) −179.2(3) −179.5(2) 176.0(2) 6 (E = P) Bond Lengths and Angles 2.252(1) 2.501(1) 1.848(2) 92.24(8) 85.02(7) 176.16(4) peri Region Distances 2.268(2) peri Region Bond Angles 116.5(2) 124.6(2) 110.7(2) 351.8(6) −8.2(6) 108.3(2) Out-of-Plane Displacementb 0.1669(6) 0.0468(6) Central Acenaphthene Ring Torsion −177.0(3) 178.7(3)

3 (E = Ga)

4 (E = In)

5 (E = Tl)

2.189(1) 2.174(2) 1.969(5) 120.0(1) 116.7(1) 109.08(6)

2.3782(5) 2.4430(5) 2.146(2) 123.00(5) 132.42(5) 104.37(2)

2.4193(7) 2.4921(6) 2.148(2) 129.02(7) 124.89(6) 105.22(2)

2.411(2)

2.7043(5)

2.7725(6)

112.8(3) 126.2(4) 116.7(3) 356(2) −4(2) 106.9(2)

116.4(2) 127.8(2) 118.1(2) 362.3(6) 2.3(6) 104.28(9)

116.7(2) 128.7(2) 118.7(2) 364.1(6) 4.1(6) 105.6(2)

0.043(2) 0.2460(6) Angles −179.7(5) 176.8(5)

0.0643(5) 0.3796(1)

0.1802(6) 0.2976(1)

−179.1(2) 177.2(2)

−179.7(3) −177.0(3)

7 (E = As)

8 (E = Sb)

9 (E = Bi)

2.381(2) 2.543(2) 1.981(7) 89.9(2) 86.5(2) 173.75(8)

2.525(1) 2.396(1) 2.170(2) 93.16(7) 95.62(7) 87.58(3)

2.5714(8) 2.8503(7) 2.251(3) 90.09(8) 84.60(8) 174.32(2)

2.394(2)

2.808(1)

2.7696(8)

116.6(5) 125.5(7) 112.6(6) 355(3) −5(3) 106.2(4)

121.5(3) 128.7(2) 116.1(2) 366.3(7) 6.3(7) 104.0(2)

119.2(2) 127.9(3) 116.6(2) 363.7(7) −3.7(7) 107.6(2)

0.013(3) 0.0291(9) Angles −173.9(8) 178.6(8)

0.1075(6) 0.1799(3)

−0.2478(8) 0.2132(1)

180.0(3) 176.1(3)

178.8(4) 175.4(3)

Splay angle: (sum of the three bay region angles) − 360. bCompounds 2, 3, and 8 have a cisoid out-of-plane displacement, and compounds 1, 4−7, and 9 show a transoid out-of-plane displacement. a

X-ray Crystallography. The molecular structures of 1−5, 2a,b, and 6−9 established by X-ray crystallography are shown in Figures 1−3, respectively. Selected bond parameters are collected in Table 1. The monosubstistuted ArECl2 compounds 1−9 adopt three distinctively different structural types (Chart 2). All group 13 compounds comprise regular Lewis pairs with rather short E−P peri distances and distorted-tetrahedral triele atoms in which attractive interactions between E and P are decisive (1−5, type A). No evidence was found for FLPs with long E−P peri distances, such as Ib3,4 and IIIb (Chart 1),6 in which the interactions between E and P are predominantly

of addition at room temperature even gave the trisubstituted product Ar3Al (2b). With the exception of ArBCl2 (1), ArAsCl2 (2), ArSbCl2 (3), and ArBiCl2 (9) all compounds are sensitive toward hydrolysis. The lighter compounds ArAlCl2 (2), Ar2AlCl (2b), Ar3Al (2c), ArGaCl2 (3), and ArPCl2 (6) show immediate decomposition on exposure to moist air. Once isolated from the mother liquor, ArInCl2 (4) and ArTlCl2 (5) are reasonably stable toward moist air but decompose within a few hours in wet solvents. Notably, ArTlCl2 (5) undergoes decomposition also in dry chlorinated solvents in less than 1 h. E

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108.3(2)°. Both results suggest that the spatial arrangement of the P atoms is very little affected by distortion. NMR Spectroscopy. Compounds 1−3, 6, and 7 are readily soluble in moderately polar solvents such as CH2Cl2 and THF. The solubility virtually drops for compounds containing the heavier elements of periods 5 and 6 (4, 5, 8, and 9), which is presumably due to secondary E···Cl interactions that might also exist in solution. The 31P NMR chemical shifts of 1−9 are strongly influenced by the substituents in the peri positions and vary between δ −36.0 and 54.8. The largest difference within group 13 compounds is observed between 1 (δ 3.7) and 2 (δ −35.0). The former value is reasonably close to that of IIIa (δ 12.2),6,7 whereas the latter compares well with those of the heavier congeners 3 (δ −34.0), 4 (δ −36.0), and 5 (δ −18.7) and the recently reported series of (6-diphenylphosphino)acenapth-5-yl)stannanes.18 Within the series of group 15 compounds, the 31P NMR chemical shifts of 6 (δ 54.8) and 7 (δ 48.2) are very different from those of 8 (δ −17.7) and 9 (δ −0.4), which might be due to the different structure types B and C. In light of the small energy difference (see below), we speculate that 9 might adopt structure type C in solution. The 31 P and 11B NMR give rise to broad signals which prevent the assignment of a J(31P−11B) coupling constant. The 11B NMR chemical shift of δ 7.0 ppm is close to that of IIIa (δ 16.2 ppm)6 and is indicative of a four-coordinated B atom. Due to the two highly abundant NMR-active thallium isotopes 205Tl (70%, I = 1/2) and 203Tl (30%, I = 1/2), the 31P NMR signal of 5 is split into two doublets, giving rise to J(31P−205/203Tl) couplings of 4513 and 4474 Hz. It is noteworthy that indirect spin−spin coupling constants (SSCC) involving the nuclei 31P, 77 Se, 119Sn, and 125Te have been instrumental in analyzing the nature of peri interactions in substituted (ace)naphthyl compounds.21 The 3J(1H−205/203Tl) and 4J(1H−205/203Tl) couplings of 837 and 189 Hz are slightly smaller than those of 1-naphthylthallium dichloride (3J = 984 Hz; 4J = 287 Hz).22 The 31P NMR spectrum of 6 shows a characteristic J(31P−31P) coupling of 389 Hz, which compares well with that of V (364 Hz).9 It is noteworthy that the 1J(31P−13C) coupling constants significantly decreases from ArBCl2 (1) to ArInCl2 (4) and from ArPCl2 (6) to ArSbCl2 (9), especially on comparison of elements from period 4 to 5 (1 (61/65 Hz) > 2 (49/48 Hz) > 3 (50/51 Hz) > 4 (27/25 Hz); 6 (75/68 Hz) > 7 (68/62 Hz) > 8 (18/19 Hz)). AIM and ELI-D Analysis. Gas-phase structures of 1−9 were obtained by geometry optimization at the B3PW91/TZVP level of theory. Starting from the experimental coordinates, closely related minima were found for the regular Lewis pairs of group 13 (type A), referred to as 1A−5A. Repeating the optimization with substantially longer peri distances (ca. 3.8 Å) gave the same minima. No evidence was found for minima representing frustrated Lewis pairs, which so far have only been observed in the phosphino-(ace)naphthyl-boranes Ib3,4 and IIIb6 containing bulky substituents. From appropriate coordinates taken from the experimental coordinates for all group 15 compounds as the starting point, two minima were found, which are denoted 6B−9B (type B) and 6C−9C (type C). Superimposed structures of 1A−5A, 6B−9B, and 6C−9C are shown in Figure 4. The energy differences for 6B/6C, 7B/7C, 8B/8C, and 9B/ 9C are −10.60, −6.27, −17.46, and −16.02 kJ mol−1, respectively. The higher stability of type C in the gas phase suggests that the structures of type B experimentally observed for 6, 7, and 9 require an electric field such as that present in the crystal lattice of polar compounds or in solvents with high

Chart 2. Different Spatial Arrangements of 1−9

repulsive. The pnictogen atoms of the group 15 compounds adopt two different T-shaped spatial arrangements, one with a nearly linear Cl−E−Cl linkage (6, 7, and 9, type B) similar to those already observed for V9 and VI (Chart 1)11 and the other with a nearly rectangular Cl−E−Cl linkage (8, type C). Inspection of the E−P peri distances of 1−9 reveals some unexpected trends. The B−P distance of 1 (2.040(2) Å) compares well with those of the related phosphinoboranes Ia (2.108(2) Å),3,4 IIa (2.173(3) Å), IIb (2.011(2) Å),5 and IIIa (2.162(2) Å).6,7 However, the Al−P distance of 2 (2.4305(5) Å) is exceptionally longer than expected; it is slightly longer than the Ga−P distance of 3 (2.411(2) Å) and even substantially longer than the P−P distance of 6 (2.252(1) Å). The Al−P distances of the related di- and triarylalanes 2a (2.6934(7) and 2.7405(7) Å) and 2b (2.831(2), 2.909(2), and 2.943(2) Å) are even longer than that of 2 (see the Supporting Information for details). The In−P and Tl−P distances of 4 (2.7043(5) Å) and 5 (2.7725(6) Å) are very similar and expectedly the longest within the series of group 13 compounds. The P−P and As−P distances of 6 (2.268(2) Å) and 7 (2.394(2) Å) compare well with those of V (2.257(1) Å)9 and VI (2.403(1) Å).11 The Sb−P distance of 8 (2.808(1) Å) is substantially longer, even longer than the Bi−P distance of 9 (2.7696(8) Å), which can be attributed to the different structural types within the series of group 15 compounds. In contrast, the two E−Cl bonds within the series of the group 13 compounds are very similar in lengths and increase in the order 1 (1.842(2) and 1.870(2) Å) < 2 (2.1261(5) and 2.1367(5) Å) < 3 (2.174(2) and 2.189(1) Å) < 4 (2.3782(5) and 2.4430(5) Å) < 5 (2.4193(7) and 2.4921(6) Å). The two E−Cl bonds within the series of group 15 compounds are significantly different, which is particularly noteworthy for 6, 7, and 9 (type B), pointing to an ionic bond situation and the influence of crystal-packing effects. The E−Cl bond lengths of 6 (2.252(1) and 2.501(1) Å) and 7 (2.381(2) and 2.543(2) Å) are reminiscent of those of V (2.275(1) and 2.488(2) Å)9 and VI (2.406(1) and 2.541(1) Å).11 It is noteworthy that four compounds are associated into dimers via secondary E···Cl interactions (see the Supporting Information for details). The related intermolecular E···Cl distances of 4 (2.786(1) Å), 5 (3.051(1) Å), 7 (3.166(2) Å), and 9 (3.005(1) Å) are also indicative of ionic bonding. The interaction between the peri substituents is reflected in a number of structural parameters (Table 1). As anticipated, the splay angle increases steadily from 1 (−16.3(7)°) to 5 (4.1(6)°) within the group 13 compounds (type A) and from 6 (−8.2(6)°) to 9 (−3.7(7)°) within group 15 compounds (type B), on going from the light to the heavy elements. Due to the predominately attractive interactions, the out-of-plane displacements of P and E are rather moderate. In all cases the P atoms are less displaced than the group 13 and group 15 elements E and the C(20)−P(1)− C(30) angles vary only in a very small range from 104.28(9) to F

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interactions, a set of topological and integrated real-space bonding indicators (RSBI) derived from the electron and electron pair densities was calculated and collected in Table 2 (see also the Supporting Information for details). The topological AIM bond path motifs and isosurface representations of the ELI-D localization domains of 1A, 2A, 6B, and 6C are shown in Figures 5 and 6. The highest electron densities ρbcp at the E−P bond critical points and the lowest (most negative) values of the corresponding Laplacian ∇2ρbcp of all compounds are found in 1A (0.70 e Å−3/−4.4 e Å−5), 6B (0.72 e Å−3/−2.9 e Å−5), and 7B (0.61 e Å−3/−1.4 e Å−5), respectively. These are typical values of (polar) covalent bonds. In contrast, rather low electron densities ρbcp at the E−P bond critical points and positive values of the corresponding Laplacian ∇2ρbcp are encountered in 2A (0.32 e Å−3/1.9 e Å−5), 6c (0.22 e Å−3/0.8 e Å−5), 7C (0.27 e Å−3/0.7 e Å−5), and 8C (0.27 e Å−3/0.7 e Å−5), respectively, which are indicative of strongly polar bonds with dominant ionic contribution. The following parameters also allow us to distinguish predominantly (polar) covalent bonding from those with strong polarization and ionic effects. The kinetic energy density over ρbcp ratios G/ ρbcp, showing the degree of iconicity, are low for 1A (0.22 he−1), 6B (0.19 he−1), and 7B (0.27 he−1) and high for 2A (0.74 he−1). The total energy density over ρbcp ratios H/ρbcp, the degree of covalency, are low (the most negative) for 1A (−0.65 he−1), 6B (−0.48 he−1), and 7B (−0.42 he−1) and high for 6C (−0.14 he−1). The volumes of the ELI-D basin V001ELI (cut at 0.001 au) and the distance of the attractor position perpendicular to the atom−atom axis ΔELI adopt the smallest values for 1A (7.26 Å3/0.15 Å), 6B (6.47 Å3/0.10 Å), and 7B (7.40 Å3/0.13 Å) of all compounds. Consistently, the Raub− Jansen indexes (RJIs) of 1A (78%), 6B (64%), and 7B (66%) are indicative of polar covalent bonding. RJI values close to or above 95% as observed for 2A (93%) and 7C (96%) reveal bonding classes with strong polarization toward one-atom, closed-shell interactions or even nonbonding situations. As mentioned above, the extraordinarily long and mainly ionic Al− P peri interaction of 2A is an exception for the series 1A−5A, a trend that is reflected in all topological and integrated bond properties (Table 2). For the other compounds in this series the peri distances become steadily longer and increasingly more ionic across the row from 1A to 5A. The differences between the predominantly polar covalent B−P bond of 1A and the mainly ionic Al−P bond of 2A are also visible in the location and shape of the bonding B−P and Al−P ELI-D basins (see Figure 6 for isosurface representations of the ELI-D). The B−P basin is located along the B−P axis and centered in the middle between both atoms, which is typical for (polar) covalent interactions (see for example the bonding C−C basins in the acenaphthyl moieties).20 The Al−P bonding basin, however, is located close to the P atom and its attractor is situated ca. 0.3 Å apart from the Al−P axis, which is commonly found in ionic interactions. Concomitantly, the RJI increases from 78% in 1A to 93% in 2A, a typical value for coordinative contacts.6 These results are further supported by the ELI-D distributions on the bonding B−P and Al−P basin (see Figure 7), which show increased electron localizability in direction of the P and B atoms for 1A but only minor localizability in direction of the Al atom for 2A. Interestingly, a significant change is observed in the character of the peri interactions between the different structure types of 6B−9B and 6C−9C. For 6B−9B the AIM bond topology as well as the RJI indicate polar covalent contacts with decreasing

Figure 4. Superposition of the gas-phase structures: type A (top, left), 1A (brown) 2A (yellow), 3A (orange), 4A (red), and 5A (violet); type B (top, right), 6B (yellow), 7B (orange) 8B (red), and 9B (violet); type C (bottom, left), 6C (yellow), 7C (orange) 8C (red), and 9C (violet).

dielectric constants. In an effort to verify this hypothesis, the optimization of 6B and 7B was repeated including a polarizable continuum model (PCM) for solvation by MeCN. The minimum structures are denoted 6Bpcm and 7Bpcm (see the Supporting Information for details). Indeed, inclusion of solvation significantly decreases the energy below that of type C. The energy differences for 6C/6Bpcm and 7C/7Bpcm are −55.26 and −62.08 kJ mol−1, respectively. The geometries of type B with and without inclusion of solvation differ only very little, with one exception: The two E−Cl bond lengths are quite similar in 6B (2.3227 and 2.3701 Å) and 7B (2.4372 and 2.4460 Å) but are unequal in 6Bpcm (2.2998 and 2.4857 Å) and 7Bpcm (2.4533 and 2.5105 Å). Both the energy decrease and the unequal E−Cl bonds support the hypothesis that an electric field is required for the structure type B. In a very recent experimental and theoretical study on phosphine complexes of antimony(III) chloride, a similar solvation effect was reported for [mer-Cl3-cis-(Me3P)2Sb].23 Overall, the agreement between the experimentally observed and theoretically calculated structures is very good and all trends are fully retained, particularly for the peri distances (see the Supporting Information for details). For instance, the Al−P distance of 2A (2.4788 Å) is substantially longer than the B−P distance of 1A (2.0804 Å) and slightly longer than the Ga−P distance of 3A (2.4703 Å). These values closely resemble those of the experimental structures of 2 (2.4305(5) Å), 1 (2.040(2) Å), and 3 (2.411(2) Å), respectively. Interestingly, the P−P distances of 6B (2.2831 Å) and 6C (2.8913 Å) are very different. The former distance is very close to the experimentally obtained value of 6 (2.268(2) Å), whereas the latter is somewhat reminiscent of the value for IV (3.052(2) Å). In an effort to get further insight into the nature of the E−P peri G

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Table 2. Calculated Bond Topologicala and Integratedb Bond Descriptors for the E−P peri Interactions of 1−9 (E = B, Al, Ga, In, Tl, P, As, Sb, Bi) 1A 2A 3A 4A 5A 6Bc 6C 7Bc 7C 8B 8Cc 9Bc 9C

bond P1−B1 P1−Al1 P1−Ga1 P1−In1 P1−Tl1 P1−P2 P1−P2 P1−As1 P1−As1 P1−Sb1 P1−Sb1 P1−Bi1 P1−Bi1

d 2.0804 2.4788 2.4703 2.6550 2.7407 2.2831 2.8913 2.4103 2.8377 2.6262 2.9237 2.7315 3.0049

ρbcp 0.70 0.32 0.44 0.38 0.36 0.72 0.22 0.61 0.27 0.47 0.27 0.42 0.24

∇2ρbcp −4.4 1.9 0.8 1.7 1.6 −2.9 0.8 −1.4 0.7 −0.1 0.7 0.6 1.0

d1 1.327 1.601 1.394 1.417 1.399 1.227 1.484 1.280 1.491 1.390 1.528 1.399 1.542

d2 0.754 0.879 1.077 1.240 1.344 1.058 1.415 1.132 1.352 1.239 1.401 1.335 1.467

ε 0.10 0.13 0.04 0.02 0.01 0.09 0.05 0.09 0.06 0.10 0.08 0.07 0.09

1A 2A 3A 4A 5A 6Bc 6C 7Bc 7C 8B 8Cc 9Bc 9C

basin P1−B1 P1−Al1 P1−Ga1 P1−In1 P1−Tl1 P1−P2 P1d P1−As1 P1−As1 P1−Sb1 P1−Sb1 P1−Bi1 P1−Bi1

V001ELI 7.26 11.09 11.03 11.61 10.99 6.47 12.70 7.40 10.74 8.84 10.92 9.49 11.48

ELIpop 2.02 2.09 2.16 2.04 1.94 2.06 1.99 2.10 1.93 2.06 2.02 1.92 1.97

ELImax 2.14 2.38 2.17 2.14 2.10 1.92 2.35 1.92 2.17 1.99 2.17 2.00 2.22

ΔELI 2.14 2.38 2.17 2.14 2.10 1.92 2.35 1.92 2.17 1.99 2.17 2.00 2.22

RJI (e) 1.59 1.94 1.74 1.77 1.75 1.32 1.94 1.39 1.86 1.55 1.86 1.59 1.88

RJI (%) 78 93 81 87 90 64 98 66 96 75 92 83 95

G/ρbcp 0.22 0.74 0.53 0.57 0.54 0.19 0.39 0.27 0.36 0.35 0.38 0.39 0.44

H/ρbcp −0.65 −0.33 −0.40 −0.26 −0.23 −0.48 −0.14 −0.42 −0.18 −0.36 −0.20 −0.29 −0.16

a Definitions and units: electron density ρbcp, in e Å−3, and its corresponding Laplacian ∇2ρbcp, in e Å−5; d1 and d2, distances from bond critical point to nucleus in Å; ε, bond ellipticity; G/ρbcp and H/ρbcp, kinetic and total energy density over ρbcp ratios in he−1; ELImax, ELI-D value at the attractor position; ΔELI, distance in Å of the attractor position perpendicular to the atom−atom axis. bDefinitions and units: V001ELI, volume of the ELI-D basin in Å3 cut at 0.001 au; ELIpop, electron population within the ELI-D basin in e; RJI, Raub−Jansen index in e and %. cStructure type most resembling the experimentally observed structure. dLone pair (nonbonding) ELI-D basin of P1 atom.

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CONCLUSIONS Synthetic protocols for the preparation of an entire series of peri-substituted diphenylphosphinoacenaphthyl−element dichlorides ArECl2 of group 13/15 elements (1, E = B; 2, E = Al; 3, E = Ga; 4, E = In; 5, E = Tl; 6, E = P; 7, E = As; 8, E = Sb; 9 = Bi; Ar = 6-Ph2P-Ace-5-) have been developed. The structural elucidation by single-crystal X-ray diffraction and DFT calculations unravels a common structural motif for the group 13 compounds 1−5 featuring regular Lewis pairs with attractive P−E peri interactions. In contrast, the group 15 compounds 6−9 each show two structural isomers, the preference of which is dependent on the environment. In the gas phase the electronic ground state features one axial and one equatorial Cl atom as well as a long peri distance, pointing to weakly bonding to almost nonbonding throughspace interactions. In the environment of an electric field, such as present in the crystal lattice of polar compounds or in polar solvents, a T-shaped alignment of the Cl atoms and shorter peri distances are observed, which are associated with attractive interactions. Electron density based real-space bonding indicators derived from AIM and ELI-D space-partitioning schemes have been utilized to determine differences in the bond polarity of the peri interactions. The B−P peri interaction of 1 shows the highest degree of covalency, while the Al−P peri interaction of 2 exhibits the highest degree of ionicity.

degree of covalency on going from P to Bi. Interestingly, this order is reversed for 6C−9C. For 8 and 9, inspection of the RJI suggests that the Sb/Bi−P peri interactions become more polarized when going from 8B (75%) and 9B (83%) to 8C (92%) and 9C (95%), respectively, but the bonding character is only gradually changed from strongly polarized covalent to basically ionic. However, for the lighter congeners, particularly for 6, the bonding situation changes dramatically from mainly covalent in 6B (64%) and 7B (66%) to almost nonbonding in 6C (98%) and 7C (96%). For 6C, this also leads to a change in the ELI-D topology as the bonding P−P basin in 6B retracts to form a P atomic lone pair basin in 6C. Figure 7 displays these two basins on which the ELI-D distribution is mapped. Both the shape of the basins and the ELI-D distributions clearly unravel the totally different contact scenarios, as the lone pair basin in 6C is flattened in the direction of the second P atom and no increase of electron localizability is visible along the P− P axis. As a consequence, it can be concluded that the bond characteristics are dependent not only on the elements which form a bond but also to a high degree to the element−element distance and the spatial arrangement thereof. To a certain extent this is a self-explanatory, which, however, can be very well quantified by the combined use of topological and integrated bonding properties derived from AIM and ELI-D. H

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Figure 5. AIM bond paths of 1A, 2A, 6B, and 6C. Bond critical points are given as red dots. (unless otherwise stated, c = 1 × 10−6 mol L−1) were injected directly into the spectrometer at a flow rate of 3 μL min−1. Nitrogen was used both as a drying gas and for nebulization with flow rates of approximately 5 L min−1 and a pressure of 5 psi, respectively. Pressure in the mass analyzer region was usually about 1 × 10−5 mbar. Spectra were collected for 1 min and averaged. The nozzle-skimmer voltage was adjusted individually for each measurement. Synthesis of (5-(Diphenylphosphino)acenaphth-6-yl)boron Dichloride (5-(Ph2P)-6-(Cl2B)-Ace, 1). (6-(Diphenylphosphino)acenaphth-5-yl)tributylstannane (1.23 g, 1.96 mmol) was added to a solution of boron trichloride (1.96 mmol, 1.0 M in n-hexane) and nhexane (10 mL), causing immediate precipitation of the crude product. The reaction mixture was stirred at room temperature overnight. The precipitate was filtered, washed with n-hexane, and dried in vacuo to afford 1 as a white solid (0.51 g, 1.22 mmol, 62%; mp 92 °C dec). Crystals suitable for X-ray were obtained by recrystallization from dichloromethane/n-hexane. 1 H NMR (CDCl3): δ 7.98 (d, 3J(1H−1H) = 6.9 Hz, 1H, H-7), 7.83−7.72 (m, 5H), 7.61−7.48 (m, 8H), 3.53 ppm (m, 4H, H-1,2). 13 C{1H} NMR (CDCl3): δ 152.2 (d, 4J(31P−13C) = 2.4 Hz, Cc or Cd), 144.7 (s, Cd or Cc), 141.0 (d, 2J(31P−13C) = 29.5 Hz, Ca), 138.1 (d, 3 31 J( P−13C) = 11.3 Hz, Cb), 133.5 (d, 2J(31P−13C) = 8.8 Hz, Co), 132.0 (s, C7), 132.0 (d, 4J(31P−13C) = 2.9 Hz, Cp), 131.2 (d, 2 31 J( P−13C) = 11.8 Hz, C4), 128.9 (d, 3J(31P−13C) = 11.1 Hz, Cm), 123.8 (d, 1J(31P−13C) = 60.0 Hz, Ci or C5), 122.6 (d, 5J(31P−13C) = 2.0 Hz, C8), 120.4 (d, 3J(31P−13C) = 9.1 Hz, C3 or C6), 118.5 (d, 1 31 J( P−13C) = 65.4 Hz, C5 or Ci), 31.5 (s, C1 or C2), 30.8 ppm (s, C2

Considering compound pairs of the same period, 2 and 3 are not stronger Lewis pairs than 6 and 7, respectively, despite the electron deficiency of the Al and Ga atoms. In fact, the P−P and As−P peri interactions of 6 and 7 closely resemble the polar covalent bond character of the B−P peri interaction of 1. This observation suggests that the combination of a basic phosphine and a Lewis acidic phosphine or arsine might give rise to FLPs entirely based on group 15 elements. Reactivity studies of 1−9 are actively being perused in our laboratory.

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EXPERIMENTAL SECTION

General Considerations. Reagents were obtained commercially (Sigma-Aldrich, Germany) and were used as received. Dry solvents were collected from a SPS800 mBraun solvent system. 5-Bromo-6diphenylphosphinoacenaphthene, 20 (6-(diphenylphosphino)acenaphth-5-yl)tributylstannane,18 and thallium(III) chloride19 were prepared according to literature procedures. 1H, 11B, 13C, and 31P NMR spectra were recorded at room temperature (unless otherwise stated) using a Bruker Avance-360 spectrometer and are referenced to tetramethylsilane (1H, 13C), boron trifluoride diethyl etherate (11B), and phosphoric acid (85% in water) (31P). Chemical shifts are reported in parts per million (ppm), and coupling constants (J) are given in hertz (Hz). High-resolution electron impact mass spectroscopy (HREIMS) was carried out using a Finnigan MAT 95 instrument. The ESI-MS spectra were obtained with a Bruker Esquire-LC MS instrument. Dichloromethane/acetonitrile solutions I

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bromo-6-diphenylphosphinoacenaphthene (0.50 g, 1.20 mmol) in diethyl ether (5 mL), and the mixture was stirred for 2 h at this temperature. The suspension was warmed to room temperature, stirred for 1 h, and added at −78 °C to a suspension of aluminum trichloride (0.16 g, 1.20 mmol) and diethyl ether (5 mL). The reaction mixture was warmed to room temperature overnight. The white precipitate was filtered, washed with diethyl ether, and dried in vacuo. Dichloromethane was added to the residue, and after filtration the solvent was slowly removed under reduced pressure until the product started to crystallize. The colorless crystals of 2a were filtered and dried in vacuo (0.18 g, 0.24 mmol, 41%; mp 158 °C). 1 H NMR (CDCl3): δ 8.27 (dd, 3J(1H−1H) = 6.8 Hz, 4J(1H−1H) = 2.0 Hz, 2H), 7.62−7.55 (m, 9H), 7.39−7.32 (m, 16H), 7.10 (d, 3 1 J( H−1H) = 6.8 Hz, 2H), 3.40 ppm (m, 8H, H-1,2). 13C{1H} NMR (CDCl3): δ 150.4 (s, Cc or Cd), 146.2 (m), 141.2 (m), 134.4 (s), 133.6 (m, Co), 129.3 (s, Cp), 128.4 (m, Cm), 120.2 (s), 119.2 (m), 30.5 (s, C1 or C2), 30.2 ppm (s, C2 or C1). 31P{1H} NMR (CDCl3): δ −28.6 ppm (s). HREIMS: calcd for C48H36P2Al, 736.17962; found, 736.17913. Synthesis of Tris(5-diphenylphosphinoacenaphth-6-yl)aluminum ([5-(Ph2P)-6-Ace]3Al, 2b). n-Butyllithium (1.20 mmol, 2.5 M in n-hexane) and N,N,N′,N′-tetramethylethylenediamine (0.14 g, 1.20 mmol) were added at −78 °C to a suspension of 5-bromo-6diphenylphosphinoacenaphthene (0.50 g, 1.20 mmol) in diethyl ether (5 mL), and the mixture was stirred for 2 h at this temperature. The suspension was warmed to room temperature and stirred for 1 h, and aluminum trichloride (0.16 g, 1.20 mmol) was added. The reaction mixture was stirred at room temperature overnight. The white precipitate was filtered, washed with diethyl ether, and dried in vacuo. Dichloromethane was added to the residue, and after filtration the solvent was reduced to approximately 2−3 mL and n-hexane was slowly added. The colorless crystals of 2b were filtered and dried in vacuo (0.28 g, 0.14 mmol, 68%; mp 119 °C dec). 1 H NMR (CDCl3): δ 7.53−7.46 (m, 3H), 7.32−7.19 (m, 15H), 7.12−7.00 (m, 9H), 6.77−6.73 (m, 8H), 6.56 (d, 3J(1H−1H) = 6.6 Hz, 2H), 6.39 (t, 3J(31P−1H) = 7.5 Hz, 5H), 3.31−3.14 ppm (m, 12H, H1,2). 13C{1H} NMR (CDCl3): δ 150.4 (s), 149.5 (s), 146.2 (s), 143.4 (s), 142.6 (m), 141.2 (m), 141.2 (m), 139.1 (m), 138.3 (m), 137.7 (m), 134.8 (s), 134.3 (s), 134.0 (m), 133.5 (m), 133.7 (m), 129.3 (s), 128.9 (m), 128.4 (m), 128.2 (s), 127.9 (m), 126.3 (s), 120.2 (s), 119.7 (s), 119.3 (s), 118.2 (s), 30.2 (C1 or C2), 30.1 ppm (C2 or C1). 31 1 P{ H} NMR (CDCl3): δ −26.7 ppm (s). ESI MS (CH2Cl2/MeCN 1/10, positive mode): m/z 1077.4 (C72H54PAlK) for [M + K+]. Synthesis of (6-(Diphenylphosphino)acenaphth-5-yl)gallium Dichloride (6-(Ph 2 P)-5-(Cl 2 Ga)-Ace, 3). (6(Diphenylphosphino)acenaphth-5-yl)tributylstannane (0.50 g, 0.80 mmol) was added to a solution of gallium trichloride (0.21 g, 1.20 mmol) and toluene (5 mL). The reaction mixture was stirred at room temperature overnight. The solvent was removed slowly under reduced pressure until small crystals begin to form. Crystallization was continued at 5 °C for 7 days. The colorless crystals of 3 were filtered and dried in vacuo (0.32 g, 0.67 mmol, 84%; mp 156 °C). 1 H NMR (CDCl3): δ 8.02 (d, 3J(1H−1H) = 6.7 Hz, 1H, H-4), 7.75−7.65 (m, 5H), 7.59−7.46 (m, 8H), 3.50 ppm (m, 4H, H-1,2). 13 C{1H} NMR (CDCl3): δ 152.9 (d, 4J(31P−13C) = 2.3 Hz, Cc or Cd), 144.7 (d, 4J(31P−13C) = 1.9 Hz, Cd or Cc), 141.2 (d, 2J(31P−13C) = 19.0 Hz, Ca), 138.5 (d, 3J(31P−13C) = 8.0 Hz, Cb), 136.5 (d, 2 31 J( P−13C) = 10.5 Hz, C7), 134.8 (s, C4), 133.6 (d, 2J(31P−13C) = 11.7 Hz, Co), 131.8 (d, 4J(31P−13C) = 2.7 Hz, Cp), 129.3 (d, 3 31 J( P−13C) = 11.3 Hz, Cm), 123.8 (d, 1J(31P−13C) = 49.6 Hz, Ci or C6), 121.7 (d, 5J(31P−13C) = 5.1 Hz, C3), 119.9 (d, 3J(31P−13C) = 8.2 Hz, C5 or C8), 119.8 (d, 1J(31P−13C) = 51.3 Hz, C6 or Ci), 30.7 (s, C1 or C2), 30.4 ppm (s, C2 or C1). 31P{1H} NMR (CDCl3): δ −34.0 ppm. HREIMS: calcd for C24H18PCl2Ga, 475.97735; found, 475.97687. Synthesis of (6-(Diphenylphosphino)acenaphth-5-yl)indium Dichloride (6-(Ph2P)-5-(Cl2In)-Ace, 4). n-Butyllithium (1.20 mmol, 2.5 M in n-hexane) and N,N,N′,N′-tetramethylethylenediamine (0.14 g, 1.20 mmol) were added at −78 °C to a suspension of 5-bromo-6diphenylphosphinoacenaphthene (0.50 g, 1.20 mmol) in diethyl ether (5 mL), and the mixture was stirred for 2 h at this temperature. The

Figure 6. Isosurface representations of the localization domains of the ELI-D (an isovalue of Y = 1.40) of 1A, 2A, 6B, and 6C. The labels V2(P,E) and V1(P) represent bonding (disynaptic valence) and lonepair basins, respectively. or C1). 31P{1H} NMR (CDCl3): δ 3.7 ppm (br, ω1/2 = 298 Hz). 11 1 B{ H} NMR (CDCl3): δ 7.0 ppm (br, ω1/2 = 246 Hz). HREIMS: calcd for C24H18PCl210B, 417.06471; found, 417.06376. Synthesis of (5-(Diphenylphosphino)acenaphth-6-yl)aluminum Dichloride (5-(Ph2P)-6-(Cl2Al)-Ace, 2). n-Butyllithium (1.20 mmol, 2.5 M in n-hexane) and N,N,N′,N′-tetramethylethylenediamine (0.14 g, 1.20 mmol) were added at −78 °C to a suspension of 5bromo-6-diphenylphosphinoacenaphthene (0.50 g, 1.20 mmol) in diethyl ether (5 mL), and the mixture was stirred for 2 h at this temperature. The suspension was warmed to room temperature, stirred for 1 h, and added at −78 °C to a suspension of aluminum trichloride (0.80 g, 6.00 mmol) and diethyl ether (10 mL). The reaction mixture was warmed to room temperature overnight. The white precipitate was filtered, washed with diethyl ether, and dried under vacuum. Dichloromethane was added to the residue, and after filtration the solvent was reduced to approximately 2−3 mL and nhexane was slowly added. The colorless crystals of 2 were filtered and dried in vacuo (0.28 g, 0.64 mmol, 53%; mp 124 °C). 1 H NMR (CDCl3): δ 8.04 (d, 3J(1H−1H) = 6.7 Hz, 1H, H-7), 7.68−7.63 (m, 5H), 7.58−7.43 (m, 8H), 3.49 ppm (m, 4H, H-1,2). 13 C{1H} NMR (CDCl3): δ 152.7 (d, 4J(31P−13C) = 1.9 Hz, Cc or Cd), 147.1 (s, Cd or Cc), 143.5 (d, 2J(31P−13C) = 21.0 Hz, Ca), 138.3 (d, 3 31 J( P−13C) = 9.2 Hz, Cb), 137.9 (d, 2J(31P−13C) = 7.8 Hz, C4), 134.3 (s, C7), 133.6 (d, 2J(31P−13C) = 11.8 Hz, Co), 131.6 (d, 4J(31P−13C) = 2.2 Hz, Cp), 129.3 (d, 3J(31P−13C) = 11.0 Hz, Cm), 125.3 (d, 1 31 J( P−13C) = 49.0 Hz, Ci or C5), 121.4 (d, 5J(31P−13C) = 3.2 Hz, C8), 121.0 (d, 1J(31P−13C) = 48.2 Hz, C5 or Ci), 119.6 (d, 3J(31P−13C) = 8.1 Hz, C3 or C6), 30.6 (s, C1 or C2), 30.5 ppm (s, C2 or C1). 31P{1H} NMR (CDCl3): δ −35.0 ppm. MS: no molecular ion was found in either EI or ESI. Synthesis of Bis(5-diphenylphosphinoacenaphth-6-yl)aluminum Chloride ([5-(Ph2P)-6-Ace]2AlCl, 2a). n-Butyllithium (1.20 mmol, 2.5 M in n-hexane) and N,N,N′,N′-tetramethylethylenediamine (0.14 g, 1.20 mmol) were added at −78 °C to a suspension of 5J

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Figure 7. ELI-D distributions mapped on bonding V2(P,E) basins of 1A, 2A, and 6B and the lone-pair V1(P1) basin of 6C. insoluble parts were removed by filtration. The solvent was slowly evaporated until small crystals begin to form. Crystallization was continued at 5 °C for 24 h. The colorless crystals of 5 were filtered and dried in vacuo (0.24 g, 0.39 mmol, 49%; mp 157 °C dec). Compound 5 shows decomposition in chlorinated solvents in less than 1 h, and no reliable assignment was possible for the 13C spectra. The solubility in d8-THF and C6D6 is too low to observe reasonable 13C spectra. 1 H NMR (CDCl3): δ 7.89 (d, br, 3J(205/203Tl−1H) = 837.0 Hz, 1H, H-4), 7.75−7.41 (m, 12H), 7.51 (dd, br, 3J(1H−1H) = 5.4 Hz, 4 205/203 J( Tl−1H) = 189.0 Hz, 1H, H-3), 3.68−3.32 ppm (m, 4H, H31 1 1,2). P{ H} NMR (CDCl3): δ −18.0 ppm (d, J(205/203Tl−31P) = 4516.3/4474.3 Hz). ESI MS (CH2Cl2/MeOH 1/10, positive mode): m/z 651.1 (C24H18PCl2TlK) for [M + K+], 577.1 (C24H18PClTl) for [M − Cl−]. Synthesis of (6-(Diphenylphosphino)acenaphth-5-yl)phosphorus Dichloride (6-(Ph2P)-5-(Cl2P)-Ace, 6). n-Butyllithium (2.40 mmol, 2.5 M in n-hexane) and N,N,N′,N′-tetramethylethylenediamine (0.28 g, 2.40 mmol) were added at −78 °C to a suspension of 5bromo-6-diphenylphosphinoacenaphthene (1.00 g, 2.40 mmol) in diethyl ether (10 mL) and stirred for 2 h at this temperature. The suspension was warmed to room temperature, stirred for 1 h, and again cooled to −78 °C, and phosphorus trichloride (0.32 g, 2.40 mmol) was added. The reaction mixture was warmed to room temperature overnight. The white precipitate was filtered, washed with diethyl ether, and dried in vacuo. Dichloromethane was added to the residue, and after filtration the solvent was slowly evaporated until small crystals begin to form. Crystallization was continued at 5 °C for 7 days. The colorless crystals of 6 were filtered and dried in vacuo (0.56 g, 1.27 mmol, 53%; mp 121 °C dec).

suspension was warmed to room temperature, stirred for 1 h, and added at −78 °C to a suspension of indium trichloride (0.80 g, 6.00 mmol) and diethyl ether (10 mL). The reaction mixture was warmed to room temperature overnight. The white precipitate was filtered, washed with diethyl ether, and dried in vacuo. Dichloromethane was added to the residue, and after filtration the solvent was reduced to approximately 5 mL and n-hexane was slowly added. The colorless crystals of 4 were filtered and dried in vacuo (0.28 g, 0.54 mmol, 45%; mp 171 °C dec). 1 H NMR (d8-THF): δ 7.93 (dd, 3J(1H−1H) = 6.8 Hz, 5J(31P−1H) = 2.3 Hz, 1H, H-4), 7.58−7.53 (m, 4H), 7.44−7.30 (m, 9H), 3.44 ppm (m, 4H, H-1,2). 13C{1H} NMR (d8-THF): δ 151.8 (d, 4J(31P−13C) = 1.5 Hz, Cc or Cd), 147.9 (d, 4J(31P−13C) = 2.0, Cd or Cc), 142.4 (d, 2 31 J( P−13C) = 18.9 Hz, Ca), 139.8 (d, 3J(31P−13C) = 6.4 Hz, Cb), 138.6 (d, 2J(31P−13C) = 9.3 Hz, C7), 136.7 (d, 4J(31P−13C) = 1.9 Hz, C4), 134.6 (d, 2J(31P−13C) = 13.9 Hz, Co), 130.5 (d, 4J(31P−13C) = 1.7 Hz, Cp), 129.2 (d, 3J(31P−13C) = 9.1 Hz, Cm), 125.0 (d, 1J(31P−13C) = 26.6 Hz, Ci or C6), 121.2 (d, 5J(31P−13C) = 6.3 Hz, C3), 120.0 (d, 3 31 J( P−13C) = 4.9 Hz, C5 or C8), 120.0 (d, 1J(31P−13C) = 24.5 Hz, C6 or Ci), 30.9 (s, C1 or C2), 30.6 ppm (s, C2 or C1). 31P{1H} NMR (d8THF): δ −36.0 ppm. HREIMS: calcd for C24H18PCl2In, 521.95619; found, 521.95572. Synthesis of (6-(Diphenylphosphino)acenaphth-5-yl)thallium Dichloride (6-(Ph2P)-5-(Cl2Tl)-Ace, 5). (6(Diphenylphosphino)acenaphth-5-yl)tributylstannane (0.50 g, 0.80 mmol) was added to a freshly prepared solution of thallium trichloride (reaction of thallium chloride (0.19 g, 0.80 mmol) with chlorine gas) and acetonitrile (10 mL). The reaction mixture was stirred at room temperature overnight. The precipitate was filtered, washed with acetonitrile, and dried in vacuo. Toluene (20−30 mL) was added, and K

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Organometallics

Article

1 H NMR (CDCl3): δ 8.25 (dd, 3J(31P−1H) = 9.6 Hz, 3J(1H−1H) = 7.3 Hz, 1H, H-7), 7.17 (dd, 3J(31P−1H) = 7.2 Hz, 3J(1H−1H) = 7.2 Hz, 1H, H-4), 7.80−7.74 (m, 5H), 7.65−7.61 (m, 2H), 7.56−7.51 (m, 5H), 3.60−3.53 ppm (m, 4H, H-1,2). 13C{1H} NMR (CDCl3): δ 154.6 (d, 4J(31P−13C) = 2.6 Hz, Cc or Cd), 148.2 (s, Cd or Cc), 139.7 (dd, 2J(31P−13C) = 27.2 Hz, 2J(31P−13C) = 7.2 Hz, Ca), 139.4 (d, 3 31 J( P−13C) = 14.5 Hz, Cb), 135.5 (d, 2J(31P−13C) = 3.3 Hz, C7), 133.8 (d, 2J(31P−13C) = 8.8 Hz, Co), 133.5 (d, 4J(31P−13C) = 3.3 Hz, Cp), 130.7 (dd, 2J(31P−13C) = 32.4 Hz, 4J(31P−13C) = 10.0 Hz, C4), 129.1 (d, 3J(31P−13C) = 12.9 Hz, Cm), 122.5 (dd, 1J(31P−13C) = 74.8, J(31P−13C) = 4.7 Hz, Ci or C6), 122.4 (d, 3J(31P−13C) = 10.0 Hz, C3), 122.9 (d, 3J(31P−13C) = 10.9 Hz, C5 or C8), 114.9 (dd, 1J(31P−13C) = 67.7 Hz, 3J(31P−13C) = 8.3 Hz, C6 or Ci), 31.5 (s, C1 or C2), 30.8 ppm (s, C2 or C1). 31P{1H} NMR (CDCl3): δ 54.8 (d, J(31P−31P) = 388.5 Hz, PR2), −3.5 ppm (d, J(31P−31P) = 389.4 Hz, PCl2). MS: no molecular ion was found in either EI or ESI. Synthesis of (6-(Diphenylphosphino)acenaphth-5-yl)arsenic Dichloride (6-(Ph2P)-5-(Cl2As)-Ace, 7). (6-(Diphenylphosphino)acenaphth-5-yl)tributylstannane (0.50 g, 0.80 mmol) was added to a solution of arsenic trichloride (0.22 g, 1.20 mmol) and n-hexane (5 mL). The reaction mixture was stirred at room temperature overnight. The precipitate was filtered, washed with n-hexane, and dried in vacuo to afford 7 as a white solid (0.24 g, 0.50 mmol, 62%; mp 192 °C dec). Crystals suitable for X-ray were obtained by recrystallization from dichloromethane. 1 H NMR (CDCl2): δ 8.16 (dd, 3J(31P−1H) = 9.9 Hz, 3J(1H−1H) = 7.3 Hz, 1H, H-7), 8.07 (d, 3J(1H−1H) = 7.1 Hz, 1H, H-4), 7.82−7.70 (m, 5H), 7.70−7.54 (m, 7H), 3.66−3.60 ppm (m, 4H, H-1,2). 13 C{1H} NMR (CD2Cl2): δ 155.6 (d, 4J(31P−13C) = 2.6 Hz, Cc or Cd), 148.1 (d, 4J(31P−13C) = 1.2 Hz, Cd or Cc), 140.8 (d, J(31P−13C) = 7.1 Hz, Ca or Cb), 140.6 (d, J(31P−13C) = 5.6 Hz, Cb or Ca), 137.2 (s, C7 or C4), 134.6 (d, 2J(31P−13C) = 8.7 Hz, Co), 133.5 (d, 4J(31P−13C) = 3.6 Hz, Cp), 130.0 (d, J(31P−13C) = 8.2 Hz, C4 or C7), 129.2 (d, 3 31 J( P−13C) = 12.8 Hz, Cm), 123.1 (d, 1J(31P−13C) = 67.8 Hz, Ci or C6), 122.5 (s, C3), 122.0 (d, 3J(31P−13C) = 10.2 Hz, C5 or C8), 116.9 (d, 1J(31P−13C) = 61.8 Hz, C6 or Ci), 31.7 (s, C1 or C2), 31.1 ppm (s, C2 or C1). 31P{1H} NMR (CD2Cl2): δ 48.2 ppm. HREIMS: calcd for C24H18PClAs, 447.00451; found, 447.00456 [M − Cl]+. Synthesis of (6-(Diphenylphosphino)acenaphth-5-yl)antimony Dichloride (6-(Ph 2 P)-5-(Cl 2 Sb)-Ace, 8). (6(Diphenylphosphino)acenaphth-5-yl)tributylstannane (0.50 g, 0.80 mmol) was added to a solution of antimony trichloride (0.18 g, 0.80 mmol) and toluene (5 mL). The reaction mixture was stirred at room temperature overnight. The precipitate was filtered, washed with nhexane, and dried in vacuo to afford 8 as a white solid (0.27 g, 0.52 mmol, 65%; mp 185 °C dec). Crystals suitable for X-ray were obtained by recrystallization from dichloromethane/n-hexane. 1 H NMR (d8-THF): δ 9.06 (d, 3J(1H−1H) = 7.2 Hz, 1H, H-4), 7.67 (dd, 3J(31P−1H) = 7.4 Hz, 3J(1H−1H) = 7.4 Hz, 1H, H-7), 7.59−7.54 (m, 5H), 7.49−7.40 (m, 7H), 3.49 ppm (m, 4H, H-1,2). 13C{1H} NMR (d8-THF): δ 152.8 (d, 4J(31P−13C) = 1.9 Hz, Cc or Cd), 149.7 (d, 4J(31P−13C) = 2.2 Hz, Cd or Cc), 142.1 (d, 2J(31P−13C) = 35.5 Hz, Ca), 141.2 (d, 3J(31P−13C) = 12.6 Hz, Cb), 138.7 (d, J(31P−13C) = 3.4 Hz, C4 or C7), 138.0 (d, J(31P−13C) = 3.1 Hz, C7 or C4), 134.1 (d, 2 31 J( P−13C) = 12.8 Hz, Co), 131.8 (d, 1J(31P−13C) = 17.6 Hz, Ci or C6), 130.9 (d, 4J(31P−13C) = 1.8 Hz, Cp), 129.5 (d, 3J(31P−13C) = 9.0 Hz, Cm), 127.0 (d, 1J(31P−13C) = 18.9 Hz, C6 or Ci), 121.7 (s, C3), 120.6 (d, 3J(31P−13C) = 4.6 Hz, C5 or C8), 31.2 (s, C1 or C2), 30.8 ppm (s, C2 or C1). 31P{1H} NMR (d8-THF): δ −17.7 ppm. HREIMS: calcd for C24H18PCl2Sb, 527.95559; found, 527.95585. Synthesis of (6-(Diphenylphosphino)acenaphth-5-yl)bismuth Dichloride (6-(Ph2P)-5-(Cl2Bi)-Ace, 9). n-Butyllithium (1.20 mmol, 2.5 M in n-hexane) and N,N,N′,N′-tetramethylethylenediamine (0.14 g, 1.20 mmol) were added at −78 °C to a suspension of 5bromo-6-diphenylphosphinoacenaphthene (0.50 g, 1.20 mmol) in diethyl ether (5 mL) and stirred for 2 h at this temperature. The suspension was warmed to room temperature, stirred for 1 h, and added at −78 °C to a suspension of bismuth trichloride (1.90 g, 6.00 mmol) and diethyl ether (10 mL). The reaction mixture was warmed to room temperature overnight. The white precipitate was filtered,

washed with diethyl ether, and dried in vacuo. Tetrahydrofuran (30 mL) was added to the residue, and after filtration the solvent was slowly evaporated until small crystals begin to form. Crystallization was continued at 5 °C for 7 days. The yellow crystals of 9 were filtered and dried in vacuo (0.27 g, 0.44 mmol, 37%; mp 183 °C dec). 1 H NMR (d8-THF): δ 9.97 (d, 3J(1H−1H) = 7.1 Hz, 1H, H-4), 7.81 (d, 3J(1H−1H) = 7.2 Hz, 1H, H-7), 7.65−7.55 (m, 5H), 7.48−7.38 (m, 7H), 3.51−3.45 ppm (m, 4H, H-1,2). 13C{1H} NMR (d8-THF): δ 141.7 (d, J(31P−13C) = 2.5 Hz, Ca or Cb), 138.6 (s, C7 or C4), 133.9 (d, 2J(31P−13C) = 13.3 Hz, Co), 130.6 (d, 4J(31P−13C) = 1.6 Hz, Cp), 129.1 (d, 3J(31P−13C) = 9.1 Hz, Cm), 125.6 (s), 120.9 (d, 3J(31P−13C) = 4.7 Hz, C5 or C8), 31.1 (s, C1 or C2), 30.9 ppm (s, C2 or C1). 31 1 P{ H} NMR (d8-THF): δ −0.4 ppm. ESI MS (THF/MeOH 1/10, positive mode): m/z 581.1 (C24H18PClBi) for [M − Cl−]. X-ray Crystallography. Intensity data were collected on Siemens P4 (1·CH2Cl2, 3, 8), STOE IPDS 2T (2b·2CH2Cl2, 6·CH2Cl2), and Bruker Venture D8 (2, 2a, 4, 5·(toluene), 7, 9) diffractometers at 173 K with graphite-monochromated Mo Kα (0.7107 Å) radiation. All structures were solved by direct methods and refined on the basis of F2 by use of the SHELX program package as implemented in WinGX.24 All non-hydrogen atoms were refined using anisotropic displacement parameters. Hydrogen atoms attached to carbon atoms were included in geometrically calculated positions using a riding model. Crystal and refinement data are collected in Table S1 (Supporting Information). Figures were created using DIAMOND.25 Crystallographic data (excluding structure factors) for the structural analyses have been deposited with the Cambridge Crystallographic Data Centre (CCDC nos. 1027170−1027180). Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (fax, +44-1223-336033; e-mail, [email protected]. uk; web, http://www.ccdc.cam.ac.uk). Computational Methodology. With the X-ray single-crystal coordinates as the starting point, the gas-phase molecular geometries of 1−9 were fully optimized at the B3PW91 level of theory,26 using effective core potentials for In,27 Tl,28 Sb,27 and Bi27 along with the associated triple-ζ basis sets29 and the 6-311+G(2df,p) basis set for all other atoms. The final geometries were confirmed to be minima by an analysis of harmonic vibrational frequencies. All computations were performed using the Gaussian 09 program.30 Subsequently, topological and integrated AIM and ELI-D parameters were derived using AIM200031 and DGID-4.632 on the basis of wave function and checkpoint files, respectively. For the grid calculations, a step size of 0.05 bohr was applied. The AIM graphs were displayed with AIMall.33 ELI-D graphs were shown with MOLISO.34 The figures of the superimposed structures were drawn with SCHAKAL.35

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ASSOCIATED CONTENT

S Supporting Information *

Text, figures, tables, and CIF and xyz files giving NMR spectra of 1−9, synthesis details and characterization data for [6(Ph2P)-5-Ace]SnBu2Cl, crystal and refinement data for 1−9, selected bond parameters of 2a,b, intermolecular association of 4, 5, 7, 9, crystallographic data for 1−9, AIM bond paths of 3A−5A, 7B−9B, and 7C−9C, isosurface representation of the localization domains of the ELI-D of 3A−5A, 7B−9B, and 7C−9C, ELI-D distribution mapped on bonding V2(P,E) basins of 3A−5A, 7B−9B, and 7C−9C, calculated bond lengths and angles of 1A−5A, 6B−9B, and 6C−9C, calculated bond topological parameters for the E−Cl and E−C bonds of 1A−5A, 6B−9B, and 6C−9C, calculated topological and integrated bond descriptors for Cl−E and C10−E bonds of 1A−5A, 6B−9B, and 6C−9C, and Cartesian coordinates of 1A−5A, 6B−9B, and 6C−9C. This material is available free of charge via the Internet at http://pubs.acs.org. L

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M. Z.; Woollins, J. D. Phosphorus, Sulfur Silicon Relat. Elem. 2004, 179, 999−1002. (c) Nakanishi, W.; Hayashi, S. Chem. Eur. J. 2008, 14, 5645−5655. (d) Bühl, M.; Knight, F. R.; Křístková, A.; Ondík, I. M.; Malkina, O. L.; Randall, R. A. M.; Slawin, A. M. Z.; Woollins, J. D. Angew. Chem., Int. Ed. 2013, 52, 2495−2498. (e) Stanford, M. W.; Knight, F. R.; Arachchige, K. S. A.; Camacho, P. S.; Ashbrook, S. E.; Bühl, M.; Slawin, A. M. Z.; Woollins, J. D. Dalton Trans. 2014, 43, 6548−6560. (f) Arachchige, K. S. A.; Camacho, P. S.; Ray, M. J.; Chalmers, B. A.; Knight, F. R.; Ashbrook, S. E.; Bühl, M.; Kilian, P.; Slawin, A. M. Z.; Woollins, J. D. Organometallics 2014, 33, 2424−2433. (22) Maher, J. P.; Evans, D. F. J. Chem. Soc. 1965, 637−644. (23) Chitnis, S. S.; Burford, N.; McDonald, R.; Ferguson, M. J. Inorg. Chem. 2014, 53, 5359−5372. (24) (a) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr., Sect. A 2008, A64, 112−122. (b) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837−838. (25) Brandenburg, K. DIAMOND version 3.2i; Crystal Impact GbR, Bonn, Germany, 2012. (26) (a) Perdew, J. P.; Chevary, J. A.; Vosko, S. H.; Jackson, K. A.; Pederson, M. R.; Singh, D. J.; Fiolhais, C. Phys. Rev. B 1992, 46, 6671− 6687. (b) Becke, A. D. J. Chem. Phys. 1993, 98, 5648−5652. (27) Metz, B.; Stoll, H.; Dolg, M. J. Chem. Phys. 2000, 113, 2563− 2569. (28) Metz, B.; Schweizer, M.; Stoll, H.; Dolg, M.; Liu, W. Theor. Chem. Acc. 2000, 104, 22−28. (29) Peterson, K. A. J. Chem. Phys. 2003, 119, 11099−11112. (30) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian09, revision B.01; Gaussian, Inc., Wallingford, CT, 2010. (31) Biegler-König, F.; Schönbohm, J.; Bayles, D. J. Comput. Chem. 2001, 22, 545−559. (32) Kohout, M. DGRID-4.6 ; Radebeul, Germany, 2011 (33) Keith, T. A. AIMall (Version 13.11.04, Professional); T. K. Gristmill Software, Overland Park KS, USA, 2009 (http://aim. tkgristmill.com). (34) Hübschle, C. B.; Luger, P. J. Appl. Crystallogr. 2006, 39, 901− 904. (35) Keller, E. SCHAKAL; Albert Ludwigs Universität Freiburg, Germany, 1999.

AUTHOR INFORMATION

Corresponding Authors

*E-mail for L.C.: [email protected]. *E-mail for J.B.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Dedicated to Professor Rüdiger Beckhaus on the occasion of his 60th birthday. The Deutsche Forschungsgemeinschaft (DFG) is gratefully acknowledged for financial support. L.C. thanks the Deutscher Akademischer Austauschdienst (DAAD) for a two-month fellowship.

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dx.doi.org/10.1021/om501036c | Organometallics XXXX, XXX, XXX−XXX