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Sterically Congested 5‑Diphenylphosphinoacenaphth-6-yl-silanes and -silanols Emanuel Hupf,† Enno Lork,† Stefan Mebs,*,‡ and Jens Beckmann*,† †

Institut für Anorganische Chemie und Kristallographie, Universität Bremen, Leobener Straße, 28359 Bremen, Germany Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany

‡

S Supporting Information *

ABSTRACT: The synthesis and characterization of the 5diphenylphosphinoacenaphth-6-yl-silanes 5-Ph2P-Ace-6-SiMe2H (1), 5-Ph2P(S)-Ace-6-SiMe2H (1S), 5-Ph2P(Se)-Ace-6-SiMe2H (1Se), and 5-Ph2P-Ace-6-SiMe2Cl (2) as well as of the 5diphenylphosphinoacenaphth-6-yl-silanols 5-Ph2P-Ace-6-SiMe2OH (3), 5-Ph2P(O)-Ace-6-SiMe2OH (3O), 5-Ph2P(S)-Ace-6-SiMe2OH (3S), and 5-Ph2P(Se)-Ace-6-SiMe2OH (3Se) are reported. Due to steric congestion in the bay area, the substituents in peri-positions are affected by repulsion, out-of-plane deflection, and distortion of the spatial arrangement to various extents. The peri-interaction energy associated with the steric congestion of these and a number of previously known reference compounds was computationally estimated with a set of isodesmic reactions. The organo-H-silanes 1, 1S, and 1Se possess very weak intramolecular hydrogen bridges of the types Si−H···P and Si−H···EP (E = S, Se), whereas the organosilanols 3O, 3S, and 3Se contain medium-strength hydrogen bonds of the type Si−OH···EP (E = O, S, Se). These hydrogen bonds and those of related model complexes H3SiOH···(E)PH3 were analyzed applying real-space bonding indicators derived from the electron and pair densities using the atoms-in-molecules and electron localizability indicator space-partitioning schemes as well as natural population analysis and natural bond orbital analyses.

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that of IV (Chart 1).6,7 The 5,6-bis(triorganostannyl)substituted acenaphthenes 5,6-(Me3Sn)2-Ace (IX) and 5,6(Ph3Sn)2-Ace (X) possess even larger Sn−Sn peri-distances of 3.969(1) and 4.066(1) Å, which might be related to the restricted buckling of the more rigid acenaphthyl scaffold compared to the more flexible naphthyl backbone.8,9 Among the organometallic group 14 compounds VI−X, the Si derivative VI is thermally the least stable and arguably also the most difficult to prepare. The straightforward salt metathesis of 1,8-dilithionaphthalene, 1,8-Li2-Nap, or 5,6dilithioacenaphthene, 5,6-Li2-Ace, with Me3GeCl, Me3SnCl, and Ph3SnCl afforded VII−X, but the analogous reaction with Me3SiCl failed to provide VI.10,11 The synthesis of VI was achieved by the reaction of 1,8-Li2-Nap with Me2SiHCl, initially giving the less congested 1,8-(HMe2Si)2-Nap, which was subsequently chlorinated and methylated.12 At temperatures above 150 °C, 1,8-(Me3Si)2-Nap (VI) undergoes thermal rearrangement into the less congested isomer 1,7-(Me3Si)2Nap.12 Repulsion is also the prevalent force in peri-substituted group 15 element compounds XI−XVI (Chart 1). In 1,8bis(diphenylphosphino)naphthalene, 1,8-(Ph2P)2-Nap (XI), the lone-pairs point in the direction of each other and are the course for moderate repulsion.13 The double oxidation of

INTRODUCTION The interaction between peri-substituents in 1,8- and 5,6positions of naphthalenes (Nap) and acenaphthenes (Ace) can be dominated by repulsive forces due to steric congestion or attractive forces due to weak or strong bonding.1 The peridistance is a readily assessable geometric parameter that gives a first indication which of the forces is prevalent. In the parent naphthalene (I) and acenaphthene (II) the peri-distances between the noninteracting H atoms are 2.45(4) and 2.67(3) Å (Chart 1).2,3 Smaller peri-distances are indicative of predominantly attractive forces, whereas significantly larger values are usually a sign of repulsion. In the dialkyl-substituted naphthalenes 1,8-Me2-Nap (III), 1,8-t-Bu2-Nap (IV), and 1,8Ada2-Nap (V), the calculated C−C peri-distances steadily increase with the bulk of the alkyl groups from 2.981 Å to 3.877 and 3.915 Å, respectively.4,5 Substitution of the ipso-C atoms in IV by the heavier group 14 elements M = Si, Ge, and Sn has a counterintuitive effect. While the larger atomic radii would lead to the expectation of a greater steric congestion, the larger C− M bond lengths adversely increase the conformational flexibility, offering relief from the congestion through increased out-of-plane deflection and/or more severe distortion of the spatial arrangement of the atom M. Thus, the M−M peridistances of 1,8-bis(trimethylelement)-substituted naphthalenes 1,8-(Me3M)2-Nap (VI, M = Si; VII, M = Ge; VIII, M = Sn) are with 3.803(4), 3.809(4), and 3.864(4) Å indeed smaller than © XXXX American Chemical Society

Received: June 8, 2015

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DOI: 10.1021/acs.organomet.5b00489 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics Chart 1. Peri-Distances of (Ace)naphthyl Compounds I−XVI

Chart 2. Intramolecularly Coordinated (Ace)naphthyl Compounds of Group 14 Elements

studies have accounted for certain aspects related to the congestion in IV, VI, VII, and VIII, including the ring flipping of the peri-substituents; however, no efforts were undertaken to quantify the energy associated with the repulsion.4,16 8Dimethylaminonaphthyl-1-element compounds containing the intramolecularly coordinating “DAN” ligand are the most common compound class comprising two different perisubstituents.17 Among those, peri-substituted 8-dimethylaminonaphthylsilanes A containing intramolecular Si−N interactions are abundantly known,18−21 but to the best of our knowledge there is only one short communication on the preparation of related peri-substituted 1-diorganophosphinonaphthyl-8-silanes B possessing intramolecular Si−P interactions (Chart 2).22 This is presumably due to the tedious

1,8-(Ph2P)2-Nap (XI) using H2O2 and S8 gave rise to the formation of 1,8-bis(diphenylphosphinchalcogenido)naphthalenes, 1,8-[Ph2P(E)]2-Nap (XII, E = O14; XIII, E = S15) and increased the steric crowding and the P−P peridistances from 3.052(2) Å to 3.379(1) and 3.746(1) Å, re sp ective ly ( C h a r t 1 ) . I n t h e r e l a t e d 5 , 6 -b i s (diorganophosphinsulfido)acenaphthenes 5-[Ph2P(S)]-Ace-6[P(S)i-Pr2 ] (XV) and 5-[i-PrPhP(S)]-Ace-6-[P(S)i-Pr2 ] (XVI) the P−P peri-distances of 4.041(1) and 4.051(2) Å are again even larger.8 Interestingly, the reaction of 1,8-bis(diphenylphosphino)naphthalene, 1,8-(Ph2P)2-Nap (XI), with excess Se8 occurred only at one P atom due to steric restriction and provided 1-[Ph2P(Se)]-Nap-8-(PPh2) (XIV) with a moderate P−P peri-distance of 3.248(1) Å.15 Theoretical B


Article

Organometallics Scheme 1. Synthesis and NMR Parameters of 1−3

Scheme 2. Synthesis and NMR Parameters of 1S, 1Se, 3O, 3S, and 3Se

formation of 5-Ph2P(S)-Ace-6-SiMe2H (1S), 5-Ph2P(Se)-Ace6-SiMe2H (1Se), 5-Ph2P(O)-Ace-6-SiMe2OH (3O), 5-Ph2P(S)-Ace-6-SiMe2OH (3S), and 5-Ph2P(Se)-Ace-6-SiMe2OH (3Se). Within the congested environment of these compounds (enforced) intramolecular hydrogen bonds of the type Si−H··· P (1), Si−H···EP (E = S, 1S; E = Se, 1Se), and Si−OH···E P (E = O, 3O; E = S, 3S; E = Se, 3Se) are observed.27 Unusual intramolecular hydrogen bonds situated in the confined space between two peri-substituents of a naphthalene scaffold are not unprecedented. Dorsey and Gabbaı̈ reported on 1-(dimethylfluorosilane)-8-(9H-xanthene)naphthalenediyl that possesses an agostic C−H···SiR3F interaction, which was thoroughly analyzed by a number of computational methods.28 In order to quantify the energy associated with the increasing steric

preparation of the basic starting materials, namely, 1,8dihalonaphthalenes. Replacing the latter by the easily accessible 5,6-dihaloacenaphthenes has paved the way for the preparation of 6-diorganophosphinoacenaphthyl-5-element compounds,23 including the stannanes C, in which the Sn−P interaction is either repulsive or attractive depending on the Lewis acidity of the Sn atoms.24−26 As part of our systematic studies on the bond situation in peri-substituted diphenylphosphino(ace)naphthyl element compounds, we have now investigated a series of sterically congested 5-diphenylphosphinoacenaphth-6yl-silanes and -silanols. Starting from readily available 5-Ph2PAce-6-SiMe2H (1), the functionalization of the P and Si atoms by chalcogens significantly increased the repulsive forces between the substituents in peri-position and gave rise to the C


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Organometallics

stoichiometric amounts of the hydrogen peroxide urea adduct (1:1 ratio) gave the same product, but extended the reaction time to 3 days (Scheme 1). The course of the reaction was monitored by 29Si and 31P NMR spectroscopy; however, no evidence was found for the silane 5-Ph2P(O)-Ace-6-SiMe2H (1O), containing a phosphorus(V) atom. As the formation of 3O involves both peri-substituents, we assume that the oxidation of the P atom is the rate-determining step, while the reaction at the Si atom occurs much more rapidly. Unlike the phosphorus(III) compound 5-Ph2P-Ace-6-SiMe2H (1), the phosphorus(V) species 5-Ph2P(S)-Ace-6-SiMe2H (1S) and 5Ph2P(Se)-Ace-6-SiMe2H (1Se) are moisture sensitive in solution and undergo conversion into the silanols 5-Ph2P(S)Ace-6-SiMe2OH (3S) and 5-Ph2P(Se)-Ace-6-SiMe2OH (3Se). It is noteworthy that the hydrolysis of organo-H-silanes into organosilanols usually requires the presence of a transition metal catalyst.37 The hydrolysis of 1S is complete within 2−3 weeks, while that of 1Se is significantly slower (80% conversion after 6 months, based on 31P NMR spectroscopy). The conversion of 1S and 1Se into 3S and 3Se, respectively, can be accelerated by the use of the hydrogen peroxide urea adduct (1 day) or elemental sulfur (3 days) in refluxing THF. The role of sulfur in these reactions is not entirely clear. One conceivable mechanism may involve the transient formation of silanthiols that rapidly hydrolyze to give the silanols and hydrogen sulfide. The reaction of 1Se with the hydrogen peroxide urea adduct or with elemental sulfur under moist conditions to give 3Se takes longer (up to 2 weeks) and is accompanied by the formation of 3O and 3S as side products in significant amounts. No side products are formed by the hydrolysis of 1Se in moist air in the absence of any other oxidizing reagents. The oxidation of 5Ph2P-Ace-6-SiMe2OH (3) with the hydrogen peroxide urea adduct or with elemental sulfur and selenium proved to be the rational way for the preparation of the silanols 3O, 3S, and 3Se, in 72%, 42%, and 48% yield, respectively (Scheme 2). With the exception of 1S, 1Se, and 5-Ph2P-Ace-6-SiMe2Cl (2) all compounds are stable towards moist air. The silanes 1, 1S, and 1Se, the chlorosilane 2, and the silanols 3, 3O, 3S, and 3Se are readily soluble in moderately polar solvents such as CH2Cl2 and THF. The 31P NMR chemical shifts of 1−3 containing phosporous(III) atoms are only slightly low field shifted in the order 2 (δ = −17.6) < 1 (δ = −15.6) < 3 (δ = −14.5) and compare well with the monosubstituted 5-Ph2P-Ace-6-H (δ = −14.6).31 It is worth mentioning that 31P NMR spectroscopy is a sensitive probe to study peri-substituted diphenylphosphino(ace)naphthyl compounds with 31P NMR chemical shifts ranging from δ = −45.6 to 54.8 ppm, as observed for (6Ph2P-Ace-5-)2SnCl2 and 6-Ph2P-Ace-5-PCl2, respectively.25,30 The 29Si NMR chemical shift of 5-Ph2P-Ace-6-SiMe2Cl (2, δ = 9.4) shows the expected low-field shift in comparison to the silanol 3 (δ = −1.2) and the silane 1 (δ = −19.7). Interestingly, the methyl groups of 1−3 give rise to J(31P−13C(CH3)) coupling constants, which increase in the order 3 (11 Hz) < 1 (19 Hz) < 2 (30 Hz). However, a J(31P−29Si) coupling was observed only for 1 (J = 12 Hz). The 31P NMR chemical shifts of the phosphorus(V) species 1S and 1Se are slightly low field shifted (δ = 50.5 and 41.1) compared to those of the respective silanols (3S, δ = 49.8; 3Se, δ = 40.0). The 29Si NMR chemical shifts of 1S (δ = −20.7) and 1Se (δ = −20.4) are very similar to the parent compound 1 (δ = −19.7) and significantly high field shifted with respect to the silanols 3O, 3S, and 3Se. Within the series of silanols a moderate high-field shift is observed in the order 3O (δ = 3.5) > 3S (δ = 0.5) > 3Se (δ = −0.2) > 3 (δ =

congestion, a set of isodesmic reactions was calculated, and two different peri-interaction energies (PIEs) were defined and validated against disubstituted naphthalene isomers. Extending upon our preceding studies,9,25,29−33 we carried out topological analyses of the computed electron and pair densities according to the atoms-in-molecules (AIM)34 and electron localizability indicator (ELI-D)35 space-partitioning schemes. By definition of surfaces of zero electronic flux, atomic basins and a topological bond path motif are generated within the AIM scheme, which affords the detection of weak to nonbonding interactions and the quantification of charge transfer between atoms or molecular fragments, whereas ELI-D generates basins of paired electrons, which yields the localization/visualization and quantification of core, bonding, and nonbonding electron pairs. This means that the size, shape, and spatial orientation of the electron pairs responsible for attraction and repulsion in the bay area of naphthalenes and acenaphthenes become visible. For a complementary view on the hydrogen bonds Si−OH··· EP (E = O, 3O; E = S, 3S; E = Se, 3Se) natural bond orbital (NBO)36 analyses were carried out on the model complexes H3SiOH···(E)PH3 (E = O, S, Se), and the results compared to those of our previous studies on supramolecular gas-phase complexes between silanols and various acceptor molecules.37

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RESULTS AND DISCUSSION Synthetic Aspects and Spectroscopic Characterization. The reaction of 5-Ph2P-Ace-6-Li (prepared in situ from 6Ph2P-Ace-5-Br with n-butyllithium and N,N,N′,N′-tetramethylethylenediamine (TMEDA)29) with chlorodimethylsilane proceeds via salt metathesis to give 5-Ph2P-Ace-6-SiMe2H (1) in 88% yield (Scheme 1). The salt metathesis of 5-Ph2P-Ace-6Li with dichlorodimethylsilane afforded the chlorosilane 5Ph2P-Ace-6-SiMe2Cl (2), which was immediately hydrolyzed into the silanol 5-Ph2P-Ace-6-SiMe2OH (3) in a two-layer mixture of diethyl ether/saturated aqueous NaCl solution in the presence of ammonium carbonate in 55% yield (Scheme 1). Alternatively, the chlorination of 5-Ph2P-Ace-6-SiMe2H (1) with catalytic amounts of palladium dichloride in refluxing carbon tetrachloride also led to the formation of 5-Ph2P-Ace-6SiMe2Cl (2) in 95% yield (Scheme 1). However, the reaction of the silane 5-Ph2P-Ace-6-SiMe2H (1) with water in the presence of Pearlman’s catalysts (Pd(OH)2/C) in THF adopting previously used conditions38 failed to provide silanol 5-Ph2PAce-6-SiMe2OH (3) presumably due to the steric congestion in the bay area. Unlike many other silanols, no self-condensation was observed for 3 under ambient conditions. Oxidation of 5Ph2P-Ace-6-SiMe2H (1) with elemental sulfur or selenium in refluxing THF gave rise to 5-Ph2P(S)-Ace-6-SiMe2H (1S) and 5-Ph2P(Se)-Ace-6-SiMe2H (1Se) after recrystallization in 43% and 57% yield, respectively (Scheme 2). Notably, the reaction of 5-Ph2P-Ace-6-SiMe2H (1) with sulfur is much slower than the reaction of 6-Ph2P-Ace-6-Br with sulfur, which can be attributed to greater steric congestion in 1. This is demonstrated by the competitive reaction of equal amounts of 5-Ph2P-Ace-6-SiMe2H (1) and 6-Ph2P-Ace-6-Br with one equivalent of sulfur at room temperature (see the SI for details). After full consumption of the sulfur, 46% of 6-Ph2PAce-6-Br (4% remaining) was converted into 6-Ph2P(S)-Ace-6Br and only 4% of 1 (46% remaining) was converted in 1S. The oxidation of 5-Ph2P-Ace-6-SiMe2H (1) with (an excess of) hydrogen peroxide in THF at room temperature immediately gave the silanol 5-Ph2P(O)-Ace-6-SiMe2OH (3O) in 62% yield (Scheme 2). The reaction of 5-Ph2P-Ace-6-SiMe2H (1) with D


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Organometallics

significantly smaller wavenumber, which can be explained by the presence of intramolecular hydrogen bonds of medium strength (see below). Molecular Structures. The molecular structures of 1, 1S, 1Se and 3O, 3S and 3Se established by X-ray crystallography are shown in Figures 1−3. Selected bond parameters are collected in Table 1. The spatial arrangement of all silicon atoms is tetrahedral, however, with a varying degree of distortion due to the steric congestion (see below). The (nonbonding) Si−P peri-distance of 5-Ph2P-Ace-6-SiMe2H (1, 3.1835(7) Å) is indicative for predominantly repulsive interactions, which increase upon oxidation of the phosphorus atom in 5-Ph2P(S)-Ace-6-SiMe2H (1S, 3.6905(6) Å) and 5Ph2P(Se)-Ace-6-SiMe2H (1Se, 3.718(2) Å). Judging from the Si−P peri-distances of 5-Ph2P(O)-Ace-6-SiMe2OH (3O, 3.8083(6) Å), 5-Ph2P(S)-Ace-6-SiMe2OH (3S, 3.863(2) Å), and 5-Ph2P(Se)-Ace-6-SiMe2OH (3Se, 3.909(2) Å), the repulsive forces increase even more when going to the silanols. The latter values are in between the peri-distances reported for the sterically congested naphthyl compounds VI (Si−Si; 3.803(4) Å),6 VII (Ge−Ge; 3.809(4) Å),7 VIII (Sn−Sn; 3.864(4) Å),11 and XIII (P−P; 3.746(1) Å)8 and for the acenaphthyl compounds IX (Sn−Sn; 3.969(1) Å),8 X (Sn−Sn; 4.066(1) Å),8 XV (P−P; 4.041(1) Å),8 and XVI (P−P; 4.051(2) Å)8 (Chart 1). The steric congestion in 1S, 1Se, 3O, 3S, and 3Se is reflected in a number of other geometrical parameters. Thus, 5-Ph2P(S)-Ace-6-SiMe2H (1S) and 5Ph2P(Se)-Ace-6-SiMe2H (1Se) show a significant P/Si atom out-of-plane displacement from the central acenaphthyl moiety of 0.3547(4)/0.4256(4) Å (1S) and 0.3748(8)/0.4868(9) Å (1Se), respectively, which is in contrast to the almost nondisplaced P/Si atoms in 5-Ph2P-Ace-6-SiMe2H (1). The P/Si out-of-plane displacement of the silanol 5-Ph2P(O)-Ace-6SiMe2OH (3O) is even higher (0.9083(3)/0.9995(4) Å), which might be due to the intramolecular hydrogen bond, as indicated by the O1−O2 donor−acceptor distance of 2.609(2) Å. It is also noteworthy that the P/Si out-of-plane displacement of 3O is larger than that of the Sn atoms in IX (0.735(1)/ 1.023(1) Å)8 and X (0.725(1)/1.045(1) Å),8 possessing even larger peri-distances. The P−P-substituted acenaphthyl compounds XV and XVI show significantly larger P/P displacements (XV: 0.989(1)/1.206(1) Å; XVI: 1.179(1)/1.218(1) Å) than 3O.8 The naphthyl compounds VI, VII, VIII, and XIII

Figure 1. Molecular structure of 1 showing 30% probability ellipsoids and the crystallographic numbering scheme.

−1.2). The νSiH stretching vibrations of the silanes 1S (2221 cm−1) and 1Se (2214 cm−1) containing P(V) atoms are observed at higher wavenumbers when compared to the parent silane 1 (2161 cm−1) containing phosphorus(III) atoms. This blue-shift suggests that the Si−H σ-bond is weaker in 1 than in 1S and 1Se and provides the first experimental evidence for a hitherto unprecedented hydrogen bond of the type Si−H··· P.39,40 It should be noted that agostic Si−H···M interactions of transition metal compounds usually lead to a much stronger interaction compared to 1, expressed in significantly smaller wavenumbers for the νSiH stretching vibrations (see, for example, 1483 cm−1, M = Ti; 1973 cm−1, M = Cu).41 Further evidence for this type of the Si−H···P hydrogen bond stems from the 1H NMR spectrum of 1, showing a doublet of septets with a J(31P−1H) coupling of J = 18 Hz for the Si−H group. It is noted that the same coupling was not observed in the Hcoupled 31P NMR spectrum of 1. Judging from the 1J(29Si−1H) coupling constants, the Si−H bond in 1 (197.5 Hz) is slightly weaker than those of 1S (210.1 Hz) and 1Se (210.6 Hz). The νSiOH stretching vibrations of the silanols 3 (3401 cm−1), 3S (3402 cm−1), and 3Se (3408 cm−1) vary only in a small range and point to weak or no hydrogen bonding. The νSiOH stretching vibration of 3O (3056 cm−1) is observed at a

Figure 2. Molecular structures of 1S (left) and 1Se (right) showing 50% probability ellipsoids and the crystallographic numbering scheme. E


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Organometallics

Figure 3. Molecular structures of 3O (top), 3S (middle), and 3Se (bottom) showing 50% probability ellipsoids and the crystallographic numbering scheme. Note the large displacement of Si1 and P1 from the acenaphthyl scaffold of 3O as opposed to 3S and 3Se as well as the large C10−Si1−O1 angles of 3S and 3Se compared to 3O.

Ace (VIII/IX).8,9,11 In contrast to 5-Ph2P(O)-Ace-6-SiMe2OH (3O), the silanols 5-Ph2P(S)-Ace-6-SiMe2OH (3S) and 5Ph2P(Se)-Ace-6-SiMe2OH (3Se) comprise a moderate P/Si out-of-plane displacement comparable to those of the silanes 5-

also show larger out-of-plane displacements of the perisubstituents, but a comparison might be misleading since the more rigid acenaphthyl backbone often leads to smaller out-ofplane displacements, as it can be nicely seen in (SnMe3)2-Nap/ F


Article

Organometallics Table 1. Selected Bond Parameters [Å, deg] of 1, 1S, 1Se, 3O, 3S, and 3Se 1; X = H(1), E = null Bond Lengths and Angles Si(1)−X 1.45(3) Si(1)−C(3) 1.864(2) Si(1)−C(4) 1.869(2) Si(1)−C(10) 1.887(3) X−Si(1)−C(3) 112.8(9) X−Si(1)−C(4) 101(2) X−Si(1)−C(10) 115.3(9) C(3)−Si(1)−C(4) 106.1(2) C(3)−Si(1)−C(10) 111.4(2) C(4)−Si(1)−C(10) 109.0(2) P(1)−E P(1)−C(18) 1.830(2) P(1)−C(20) 1.833(2) P(1)−C(30) 1.828(2) E−P(1)−C(18) E−P(1)−C(20) E−P(1)−C(30) C(18)−P(1)−C(20) 102.22(7) C(18)−P(1)−C(30) 104.06(7) C(20)−P(1)−C(30) 102.18(7) Peri Region Distances P(1)···Si(1) 3.1835(7) E···Si(1) E···X Peri Region Bond Angles Si(1)−C(10)−C(19) 129.3(2) C(10)−C(19)−C(18) 128.3(2) P(1)−C(18)−C(19) 120.6(2) Σ of bay angles 378.2(6) splay anglea 18.2(6) E−H(1)−O(1) Out-of-Plane Displacementb P(1) 0.0677(4) Si(1) 0.0679(5) E X 0.95(3) Central Acenaphthene Ring Torsion Angles C: (13)−(14)−(19)− −179.9(2) (18) C: (15)−(14)−(19)− −179.3(2) (10)

1S; X = H(1), E = S(1)

1Se; X = H(1), E = Se(1)

3O; X = O(1), E = O(2)

3S; X = O(1), E = S(1)

3Se; X = O(1), E = Se(1)

1.42(2) 1.869(2) 1.873(3) 1.891(2) 105.4(6) 105.2(7) 121.6(7) 108.17(8) 109.43(8) 106.40(7) 1.9570(5) 1.821(2) 1.826(2) 1.818(2) 114.96(5) 109.57(5) 114.90(5) 105.49(7) 107.22(7) 103.73(7)

1.29(4) 1.871(4) 1.878(4) 1.891(3) 114(2) 107(2) 112(2) 107.8(2) 109.2(2) 106.0(2) 2.1115(9) 1.828(3) 1.831(3) 1.820(3) 115.4(2) 109.1(2) 115.0(2) 105.2(2) 107.4(2) 103.7(2)

1.631(2) 1.863(2) 1.850(2) 1.898(2) 104.26(8) 112.52(8) 112.76(7) 108.66(8) 106.72(7) 111.42(7) 1.498(2) 1.805(2) 1.809(2) 1.805(2) 117.91(7) 108.73(7) 112.10(7) 108.60(7) 104.57(7) 104.00(7)

1.634(2) 1.869(3) 1.867(3) 1.908(3) 109.0(2) 102.5(2) 120.6(2) 111.2(2) 106.9(2) 106.6(2) 1.978(2) 1.825(2) 1.833(3) 1.821(3) 115.03(9) 108.17(9) 115.03(9) 106.6(2) 107.4(2) 103.8(2)

1.604(3) 1.876(3) 1.863(3) 1.900(3) 108.3(2) 102.4(2) 121.9(2) 109.9(2) 107.1(2) 106.9(2) 2.1244(7) 1.818(3) 1.829(3) 1.823(3) 115.51(9) 108.13(9) 115.04(9) 106.2(2) 107.3(2) 103.7(2)

3.6905(6) 3.3867(6) 2.96(2)

3.718(2) 3.466(2) 3.03(4)

3.8083(6) 3.445(2) 2.609(2)

3.909(2) 3.591(2) 3.092(3)

3.863(2) 3.5969(9) 3.142(3)

134.8(2) 130.3(2) 125.6(2) 390.7(6) 30.7(6)

134.2(2) 130.5(3) 125.9(2) 390.6(7) 30.6(7)

130.1(2) 129.5(2) 122.8(2) 382.4(6) 22.4(6) 170(3)

139.2(2) 131.0(2) 127.1(3) 397.3(6) 37.3(6) 146(5)

138.2(2) 131.2(2) 126.5(2) 395.9(6) 35.9(6) 153(2)

0.3547(4) 0.4256(4) 1.7154(4) 0.77(2)

0.3748(8) 0.4868(9) 1.8261(3) 0.83(4)

0.9083(3) 0.9995(4) 0.052(2) 1.768(2)

0.3257(7) 0.3698(7) 1.7130(7) 0.750(3)

0.3427(7) 0.4430(8) 1.8213(3) 0.810(3)

−177.1(2)

−176.4(3)

168.7(2)

−176.8(3)

−176.4(3)

−176.2(2)

−175.6(4)

170.3(2)

−175.8(3)

−175.6(3)

a Splay angle: ∑ of the three bay region angles 360°. bCompound 1 has a cisoid out-of-plane displacement; 1(S, Se) and 3(O, S, Se) show a transoid out-of-plane displacement.

order 18.2(6)° (1) < 22.4(6)° (3O) < 30.6(7)° (1Se) < 30.7(6)° (1S) < 35.9(6)° (3Se) < 37.3(6)° (3S), reflecting the high degree of in-plane distortion. The splay angles are significantly larger than the 27° observed for compounds X and XVI.8 In all compounds the P atoms are less displaced than the Si atoms. Consistently, the C(20)−P(1)−C(30) angles vary only in a very small range from 102.18(7)° to 104.00(7)°. Computational Analysis. Peri-Interaction Energy. In order to quantify the energy associated with the repulsion or attraction of the peri-substituents in 1,8- and 5,6-positions of naphthalenes and acenaphthenes, two computational approaches were evoked and exemplified for 1,8-(Me3Si)2-Nap (VI). The first approach involves calculation of structural isomers of VI, namely, 1,5-(Me3Si)2-Nap (XVII), 1,7-(Me3Si)2Nap (XVIII), and 2,7-(Me3Si)2-Nap (XIX), which lack Si−Si

Ph2P(S)-Ace-6-SiMe2H (1S) and 5-Ph2P(Se)-Ace-6-SiMe2H (1Se). Instead, 3S and 3Se show a widening of the O(1)− Si(1)−C(10) angle to 120.6(2)° and 121.9(2)°, respectively. Such large deviations from the ideal tetrahedral angle while retaining the coordination number 4 are very rare and usually only observed when very bulky substituents are attached to the central atom.42 The silanol 5-Ph2P(O)-Ace-6-SiMe2OH (3O) showing the large P/Si out-of-plane displacement lacks such a dramatic widening of the O(1)−Si(1)−C(10) angle (112.76(7)°). The distortion of the geometry is also reflected in the Si(1)−C(10) bond length, which is greater in 5-Ph2P(S)Ace-6-SiMe2OH (3S, 1.908(3) Å) and 5-Ph2P(Se)-Ace-6SiMe2OH (3Se, 1.900(3) Å) than in 5-Ph2P-Ace-6-SiMe2H (1, 1.887(3) Å). The splay angle, which is defined by the sum of the three bay region angles minus 360°, increases in the G


Article

Organometallics peri-contacts. As anticipated, 1,8-(Me3Si)2-Nap (VI) and 2,7(Me3Si)2-Nap (XIX) are the least and the most stable isomers. The energy of the former was arbitrarily set to zero, and relative energies are collected in Chart 3. The energy difference

The second approach applies isodesmic reactions to compare the added energies of the peri-substituted compounds AB and of the parent naphthalene or acenapthene HH, denoted as E1, with the added energies of the two mono-substituted compounds (AH and BH), denoted as E2 (Scheme 3). An attractive peri-interaction is given when the difference between E1 and E2 is negative, while a positive difference is indicative for a repulsive peri-interaction. The isodesmic approach is computationally much less demanding, as the reference compounds AH and BH are rather small and can be used in a modular manner when closely related systems are considered. To address the question of whether significant peri-interactions between one substituent and one hydrogen atom exist, two different isodesmic reactions are considered, one involving the α-positions of (ace)naphthyl compounds (AH, BH) and one involving the β-positions of (ace)naphthyl compounds (A′H, B′H) giving rise to α- and β-peri-interaction energies (α- and βPIEs). For 1,8-(Me3Si)2-Nap (VI) the calculated α- and β-PIEs (80.5 and 98.0 kJ mol−1) compare very well with the relative energies of the structural isomers (see above). For simplicity, in this study isodesmic reactions giving rise to α-PIEs were calculated for the reference compounds III−XIV (Chart 1) as well as for 1, 1O, 1S, 1Se, 3, 3O, 3S, and 3Se and are collected in Table 2. Comparison of the purely organic compounds 1,8Me2-Nap (III, 27.7 kJ mol−1), 1,8-t-Bu2-Nap (IV, 109.5 kJ mol −1 ), and 1,8-Ada2 -Nap (V, 73.2 kJ mol −1 ) nicely demonstrate that not only the ipso-carbon atom but the complete substituent determines the α-PIEs. The series 1,8-tBu2-Nap (IV, 109.5 kJ mol−1), 1,8-(Me3Si)2-Nap (VI, 80.5 kJ mol−1), 1,8-(Me3Ge)2-Nap (VII, 76.9 kJ mol−1), and 1,8(Me3Sn)2-Nap (VIII, 64.7 kJ mol−1) confirms the counterintuitive trend that ipso-elements with larger atomic radii give rise to smaller α-PIEs. The pair 1,8-(Me3Sn)2-Nap (VIII, 64.7 kJ mol−1) and 5,6-(Me3Sn) 2-Ace (IX, 51.9 kJ mol−1) exemplifies that the more rigid acenaphthyl framework reduces the steric congestion compared to the more flexibe naphthyl scaffold. Moreover, the comparison of the α-PIEs reveals no

Chart 3. Relative Energies of Bis(trimethylsilyl)naphthalene Isomers

between VI and XIX (−98.1 kJ mol−1) can be mostly related to the repulsion of the two trimethylsilyl groups in VI. In comparison, the energy difference between VI and XVII (−87.7 kJ mol−1) and XVIII (−78.6 kJ mol−1), respectively, is significantly smaller, which can be attributed to the presence of one and two peri-contacts between trimethylsilyl groups and hydrogen atoms. While the calculation of structural isomers provides precise energy differences accounting for the periinteractions, this approach suffers from two drawbacks. It is computationally quite demanding, and it neglects possible electronic effects arising from different substitution patterns.

Scheme 3. Isodesmic Reactions for the Determination of α- and β-Peri-Interaction Energies (α- and β-PIEs)

H


Article

Organometallics Table 2. Peri-Interaction Energy (α-PIE) of 1, 1O, 1S, 1Se, 3, 3O, 3S, 3Se, and Reference Compounds

a

reference compound

α-PIE, kJ mol−1

compound in this work

α-PIE, kJ mol−1

1,8-Me2-Nap (III) 1,8-t-Bu2-Nap (IV) 1,8-Ada2-Nap (V) 1,8-(Me3Si)2-Nap (VI) 1,8-(Me3Ge)2-Nap (VII) 1,8-(Me3Sn)2-Nap (VIII) 5,6-(Me3Sn)2-Ace (IX) 5,6-(Ph3Sn)2-Ace (X) 1,8-(Ph2P)2-Nap (XI) 1,8-[Ph2P(O)]2-Nap (XII) 1,8-[Ph2P(S)]2-Nap (XIII) 1-(Ph2PSe)2-8-(Ph2P)-Nap (XIV) 1,8-[Ph2P(Se)]2-Nap (XV)a

27.7 109.5 73.2 80.5 76.9 64.7 51.9 73.3 31.5 66.6 103.7 57.4 113.2

5-Ph2P-Ace-6-Me2SiH (1) 5-Ph2P(O)-Ace-6-Me2SiH (1O) 5-Ph2P(S)-Ace-6-Me2SiH (1S) 5-Ph2P(Se)-Ace-6-Me2SiH (1Se) 5-Ph2P-Ace-6-Me2SiOH (3) 5-Ph2P(O)-Ace-6-Me2SiOH (3O) 5-Ph2P(S)-Ace-6-Me2SiOH (3S) 5-Ph2P(Se)-Ace-6-Me2SiOH (3Se)

26.4 38.9 51.6 53.7 24.1 30.0 48.2 50.3

Elusive compound.15

Table 3. AIM, ELI-D, and NLMO Parameters of 1, 1O, 1S, 1Se, 3, 3O, 3S, and 3Sea bond Si−H

O−H

P···H O···H S···H Se···H P···HO O···H S···H Se···H

compound

ρ(r)bcp [e Å−3]

G/ρ(r)bcp [he−1]

H/ρ(r)bcp [he−1]

NELI

VELI

ϒmax

1 1O 1S 1Se 3 3O 3S 3Se 1 1O 1S 1Se 3 3O 3S 3Se

0.83 0.84 0.85 0.85 2.37 2.32 2.34 2.34 0.10 0.10 0.08 0.07 0.16 0.25 0.17 0.15

0.92 0.93 0.94 0.95 0.22 0.22 0.22 0.22 0.48 0.66 0.56 0.53 0.52 0.88 0.61 0.56

−0.71 −0.71 −0.71 −0.71 −1.92 −1.94 −1.93 −1.93 0.01 0.05 0.08 0.07 −0.03 −0.01 −0.02 0.00

1.99 1.99 2.01 2.01 1.66 1.67 1.68 1.67 2.05

14.28 13.83 13.58 13.37 5.01 4.41 4.74 4.80 13.73

10.25 10.21 9.86 9.72 3.49 3.39 3.47 3.49 2.51

2.05

13.21

2.43

NLP

2 2 2 2

× × × ×

2.30 2.28 2.28 2.28

∑LP

4.60 4.56 4.56 4.56

NLMO 0.805 0.799 0.805 0.806 0.455 0.432 0.439 0.439 0.006 0.000 −0.001 0.000 0.026 0.022 0.024 0.025

ρ(r)bcp is the electron density at the bond critical point, G/ρ(r)bcp and H/ρ(r)bcp are the respective kinetic and total energy density over ρ(r)bcp ratios, NELI and VELI are the population and volume of the protonated monosynaptic valence basins (the H atoms), ϒmax(H) is the localizability at the ELI-D attractor position, ∑LP(O) is the sum of the lone-pair electron population of the O atom in the H−O−Si part, and NLMO are the natural localized molecular orbital bond orders. a

(3S, 48.2 kJ mol−1), and 5-Ph2P(Se)-Ace-6-Me2SiOH (3Se, 50.3 kJ mol−1), having even larger peri-distances. Apparently, the repulsion of the peri-substituents is somewhat reduced in 3O, 3S, and 3Se by the formation of intramolecular hydrogen bridges. Intramolecular Hydrogen Bonds in the Peri-Substituted Compounds. The Si−H···P hydrogen bond of 1, the Si−H··· EP hydrogen bonds (E = O, S, Se) of 1O, 1S, and 1Se, and the Si−OH···EP hydrogen bonds (E = O, S, Se) of 3O, 3S, and 3Se were further analyzed using computational methods. Topological and integrated AIM and ELI-D parameters and natural localized molecular orbital (NLMO) bond orders are collected in Table 3. Since the influence of these hydrogen bonds on the PE and Si−O bonds is marginal, those parameters are given in the SI. As anticipated, hydrogen bonds involving Si−H groups are rather weak and almost fall in the regime of hydrogen−hydrogen interactions.43 Nevertheless, in all cases bond paths and Si−H···P and Si−H···EP bond critical points (bcp’s) are observed (Figures 4a and S8). The (almost) nonbonding character of these interactions is expressed in NLMO bond orders of essentially zero, and in

correlation with any geometric parameter, particularly not with the peri-distance. Thus, 5,6-(Ph3Sn)2-Ace (XI) possesses the largest peri-distance but not the highest α-PIE (73.3 kJ mol−1). In (1,8-Ph2P)2-Nap (XI) the repulsion of the lone-pairs causes a moderate α-PIE (31.5 kJ mol−1) comparable with that of 1,8Me2-Nap (III, 27.7 kJ mol−1). Oxidation of XI by chalcogens dramatically raises the α-PIE value in 1,8-[Ph2P(O)]2-Nap (XII, 66.6 kJ/mol) and 1,8-[Ph2P(S)]2-Nap (XIII, 103.7 kJ mol−1). This dramatic increase is probably the reason that the reaction of 1-[(Ph2PSe)]2-8-(Ph2P)-Nap (XIV, 57.4 kJ mol−1) with selenium failed to provide 1,8-[Ph2P(Se)]2-Nap (XV, 113.2 kJ mol−1),15 for which the highest α-PIE value yet was calculated. Among the compounds of this work, 5-Ph2P-Ace-6Me2SiH (1) and 5-Ph2P-Ace-6-Me2SiOH (3) have the lowest α-PIEs (26.4 and 24.1 kJ mol−1). The α-PIE increases upon oxidation going from 1 to 5-Ph2P(O)-Ace-6-Me2SiH (1O, 38.9 kJ mol−1), 5-Ph2P(S)-Ace-6-Me2SiH (1S, 51.6 kJ mol−1), and 5-Ph2P(Se)-Ace-6-Me2SiH (1Se, 53.7 kJ mol−1). However, unexpectedly at first, no further increase of the α-PIE was observed when going to the silanols 5-Ph2P(O)-Ace-6Me2SiOH (3O, 30.0 kJ mol−1), 5-Ph2P(S)-Ace-6-Me2SiOH I


Article

Organometallics

Figure 4. AIM topological bond path motif (a, c) and ELI-D isosurface (Y = 1.40) representations (b, d) of compounds 1 (a, b) and 3O (c, d). Bond (ring) critical points are given as red (yellow) dots in the AIM topology. In the ELI-D the basins are color-coded according to their size and change from greenish (small) to bluish (large). For clarity, protonated valence basins (H atoms) are given in transparent mode, whereas bonding and lonepair basins are solid. This suggests that the predominantly repulsive peri-interactions are partly counterbalanced by the intramolecular hydrogen bonds.

mode, and a compilation of AIM, ELI-D, and NPA (natural population analysis)/NBO (natural bond order)/NLMO derived parameters are collected in Table 4. From the Eadd values of H3SiOH···(E)PH3 (E = O, −29.37 kJ mol−1; E = S, −19.20 kJ mol−1; E = Se, −19.08 kJ mol−1) it can be gathered that the PO bond is a substantially better acceptor for hydrogen bonds than the PS and PSe bonds. The trend found for the Eadd values (E = O > S ≈ Se) in the model complexes H3SiOH···(E)PH3 nicely mirrors the trend found for the α-PIE values of peri-substituted compounds 3O (30.0 kJ mol−1) < 3S (48.2 kJ mol−1) ≈ 3Se (50.3 kJ mol−1). Intermolecular Hydrogen Bonds in the Model Complexes H3SiOH···(E)PH3 (E = O, S, Se). Hydrogen bonds of the type Si−OH···EP are not common structural motifs (E = O, S, Se). For a complementary view on these hydrogen bonds, NBO36 analyses were carried out on the model complexes H3SiOH···(E)PH3 (E = O, S, Se), and the results compared to those of our previous studies on supramolecular gas-phase complexes between silanols and various acceptor molecules.37 The complexation energy, IR red-shift of the O−H stretching mode, geometric parameters, and AIM, ELI-D, NPA/NBO/ NLMO analysis of the hydrogen-bonded model complexes H3SiOH···(E)PH3 (E = O, S, Se) are collected in Table 4. As anticipated, the weak interactions are accompanied by typical IR red-shifts of the O−H stretching vibrations and polarization effects, which affect the geometrical parameters as well as the

fact, they are topologically unstable, as the Si−H···OP and Si−H···SeP bcp’s vanish in the virial field (VF), which is the potential energy density (Figure S8). The Si−H···SP bcp is retained in the VF, but is considerably curved. In contrast, hydrogen bonds comprising Si−OH groups are stronger. The Si−OH···EP bcp’s are topologically stable, as they are observed in both (electron density) ED and VF (Figures 4c and S9). Although weak, all hydrogen bonds have some influence on the adjacent Si−H, Si−OH, and PE bonds (E = O, S, Se), with the latter two being the least affected bonds (Table S2). Notably, the Si−H bond shows an increasing amount of electron density at the Si−H bcp in the order 5-Me2HSi-Ace-6H < 1 < 1O < 1S < 1Se, whereas the opposite trend (H3SiOH > 3 > 3O ≈ 3S = 3Se) is observed for the Si−OH bond. Isosurface representations of the ELI-D of 1 and 3O are displayed in Figure 4b and d. In 1, the P atoms lone-pair (solid mode) and the adjacent basin of the hydridic H atom (transparent mode) seem to avoid each other. In 3O, the protic H(OSi) atom and the lone-pairs of the O atom are situated toward each other, and an increased electron localizability of the lone-pair is visible along the O···H axis, which is expected for an attractive interaction. Extending upon our previous study37 we also investigated the model complexes H3SiOH···(E)PH3 possessing unconstrained hydrogen bonds of the type Si−OH···EP. BSSE-corrected complexation energies (Eadd), the IR red-shifts of the H−O stretching J


Article

Organometallics

Table 4. Complexation Energy, IR Red-Shift of the H−O Stretching Mode, Geometric Parameters, and AIM, ELI-D, NPA/ NBO/NLMO Analysis of the Hydrogen-Bonded Model Complexes H3SiOH···(E)PH3 (E = O, S, Se)a Eadd [kJ mol−1] H3SiOH H3SiOH···(O)PH3 H3SiOH···(S)PH3 H3SiOH···(Se)PH3 H3SiOH H3SiOH···(O)PH3 H3SiOH···(S)PH3 H3SiOH···(Se)PH3 H3SiOH H3SiOH···(O)PH3 H3SiOH···(S)PH3 H3SiOH···(Se)PH3

H3SiOH H3SiOH···(O)PH3 H3SiOH···(S)PH3 H3SiOH···(Se)PH3

−29.37 −19.20 −19.08 QNPA(P) 1.30 0.61 0.50 N(n(E)) [au]

ν(OH) [cm−1]

Δν(OH) [cm−1]

3926 3585 3644 3650 ΔQNPA(P) 0.00 0.00 0.01 s-char [%] ΔN(n(E))

341 282 276 QNPA(Y)

0.007 0.014 0.015 ΔQNPA(Y)

−1.08 −0.57 −0.49 [au] Δ(s-char)

1.976 67.6 −0.011 1.990 85.5 −0.001 1.992 89.7 0.000 ρ(r)bcp (E···H) [e G/ρ(r)bcp (E...H) Å−3] [he−1] 0.22 0.14 0.12

Δ(P−E) [Å]

d(E···H) [Å]

d(O−H) [Å]

d(O−Si) [Å]

E···H−O [deg]

1.800 2.377 2.520 QNPA(H)

0.958 0.975 0.971 0.971 QNPA(O)

1.653 1.640 1.649 1.650 QNPA(Si)

170.15 153.05 150.39 ∑(H+O+Si)

0.50 −0.03 0.52 −0.03 0.51 −0.03 0.51 [%] N(σ*(O−H)) [au]

0.0041 −0.4 0.0285 0.3 0.0330 0.2 0.0311 H/ρ(r)bcp (E...H) NELI(H) [he−1] [e]

0.85 0.57 0.52

0.03 0.03 0.05

1.65 1.68 1.67 1.67

−1.07 1.18 −1.11 1.19 −1.11 1.18 −1.11 1.18 s-char [%] ΔN(σ*(O−H)) [au]

0.61 0.60 0.58 0.58 Δ(s-char) [%]

22.3 25.8 25.2 25.0 VELI(H) [Å]

ϒmax(H)

∑LP(O)

3.5 2.9 2.7 NLMO (E...H)

6.80 4.72 5.39 5.44

3.63 3.34 3.46 3.49

4.62 4.60 4.64 4.64

0.021 0.022 0.022

0.0244 0.0289 0.0270

Eadd is the complexation energy, (Δ)ν(OH) is the (difference) frequency of the vibrational O−H stretching mode, Δ(P−E) is the difference in the P−E bond lengths, QNPA are NPA atomic charges, N(n(E)) is the occupation of the O/S/Se lone-pair, N(σ*(O−H)) is the occupation of the antibonding O−H natural orbital, ρ(r)bcp is the electron density at the bond critical point, G/ρ(r)bcp and H/ρ(r)bcp are the respective kinetic and total energy density over ρ(r)bcp ratios, NELI and VELI are the population and volume of the protonated monosynaptic valence basins (the H atoms), ϒmax(H) is the localizability at the ELI-D attractor position, ∑LP(O) is the sum of the lone-pair electron population of the O atom in the H−O−Si part, and NLMO are the natural localized molecular orbital bond orders. a

simple complexes H3SiOH···(E)PH3 are suitable models for the same interactions.

atomic charges. In the complexes the PE and O−H bonds are elongated by about 0.01−0.2 Å in comparison with their free precursors H3SiOH and (E)PH3, whereas the Si−O bonds are shortened by ca. 0.1 Å. Concomitantly, the E and O(Si) atomic charges become ca. 0.03−0.04e more negative, which is compensated by the H and Si atoms. Negative hyperconjugation of the type n(E) → σ*(H−O) is the main contribution to Eadd,37 indicative of charge transfer between the interacting atoms, and has already been analyzed for a large set of hydrogen-bonded complexes between H3SiOH and various acceptor molecules in our former study.37 With a population increase of 0.024−0.029 au in the σ*(O−H) orbitals the H3SiOH···(E)PH3 complexes most closely resemble the values of 0.025 and 0.027 au for the H3SiOH···OR1R2 complexes (R1 = Me, R2 = H, Me).37 The same is found for the IR red-shifts, which are also very similar for these two model systems. Apparently, the electron-donating abilities are quite similar for terminal PO groups and ether, alcohol, and water-like R1− O−R2 linkages. The E···H AIM bond topological properties show the expected values for hydrogen bonds, with an electron density (ρ) value of about 0.1−0.2 e Å3 at the bond critical point and a kinetic energy density over ρ ratio (G/ρ(r)bcp) being positive and of much higher absolute value than the respective total energy density over ρ ratio (H/ρ(r)bcp). Upon hydrogen bond formation, the protonated monosynaptic valence basins (the H atoms in the ELI-D scheme) shrink from 6.8 Å3 in H3SiOH to 4.7 Å3 (E = O) and 5.4 Å3 (E = S, Se) in H3SiOH···(E)PH3, and the electrons within these basin become less localized (ϒmax decreases). Notably, all observed changes are also found for the geometrically restrained peri-substituted compounds 3O, 3S, and 3Se (see Tables S2 and S3), which let us surmise that the

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CONCLUSION A series of sterically congested 5-diphenylphosphinoacenaphth6-yl-silanes (1, 1S, 1Se) and -silanols (3O, 3S, 3Se) have been prepared and fully characterized. Peri-interaction energies for these compounds and a number of previously known reference compounds have been derived from calculation of isodesmic reactions. Neither the peri-distance nor other geometrical parameters were found to correlate with the PIE. In 1, 1S, and 1Se very weak hydrogen bridges of the type Si−H···P and Si− H···EP are evident (E = S, Se). In 3O, 3S, and 3Se mediumstrength hydrogen bonds (“weak attraction”) of the type Si− OH···EP are present (E = O, S, Se), which partly counterbalance the energy associated with the steric congestion (“strong repulsion”).

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EXPERIMENTAL SECTION

General Procedures. Reagents were obtained commercially (Sigma-Aldrich, Germany) and were used as received. Dry solvents were collected from an SPS800 mBraun solvent system. 5-Bromo-6diphenylphosphinoacenaphthene was prepared according to literature procedures.29 1H, 13C, 29Si, 31P, and 77Se NMR spectra were recorded at rt using a Bruker Avance-360 spectrometer and are referenced to tetramethylsilane (1H, 13C, 29Si) and phosphoric acid (85% in water) ( 31 P). As secondary reference for 77 Se NMR spectroscopy diphenyldiselenide in CDCl3 [δ(77Se) = 464.0 ppm] was used. Chemical shifts are reported in parts per million (ppm) and coupling constants (J) are given in hertz (Hz). Electron impact mass spectroscopy (EIMS) was carried out using a Finnigan MAT 95. The ESI-MS spectra were obtained with a Bruker Esquire-LC MS. Dichloromethane/acetonitrile solutions (or as otherwise stated, c = 1 K


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Organometallics × 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. IR spectra were recorded on a PerkinElmer Spectrum 1000 FT-IR spectrometer as KBr discs. Elemental analyses were carried out at the Institut für Wassergüte, Ressourcenmanagement and Abfallwirtschaft of the Technische Universität Wien (Austria). Synthesis of (5-(Diphenylphosphino)acenaphth-6-yl)dimethylsilane, 5-Ph2P-Ace-6-SiMe2H (1). 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 allowed to warm to rt and stirred for 1 h, and chlorodimethylsilane (0.11 g, 1.20 mmol) was added. The reaction mixture was stirred at rt overnight. Dichloromethane was added to the mixture, and after aqueous workup the solvent was removed by rotary evaporation. The residue was recrystallized by dichloromethane and nhexane to give 1 as colorless crystals (0.42 g, 1.06 mmol, 88%, mp 163 °C). 1 H NMR (CDCl3): δ = 7.96 (d, 3J(1H−1H) = 7.0 Hz, 1H, H-7 or H-8), 7.48−7.29 (m, 13H), 5.15 (dsept, J(31P−1H) = 18.0 Hz, 3 1 J( H−1H) = 3.3 Hz, 1J(29Si−1H) = 197.5 Hz, 1H, SiH), 3.44 (m, 4H, H-1,2), 0.64 ppm (dd, J(31P−1H) = 3.3 Hz, 3J(1H−1H) = 3.3 Hz, 2 29 J( Si−1H) = 120.2 Hz, 6H, CH3). 13C{1H} NMR (CDCl3): δ = 149.5 (s, Cc or Cd), 148.8 (d, 4J(31P−13C) = 2.1 Hz, Cd or Cc), 140.5 (d, 2J(31P−13C) = 33.7 Hz, Ca), 139.5 (d, 3J(31P−13C) = 9.3 Hz, Cb), 138.7 (s, C7), 138.6 (d, 2J(31P−13C) = 11.5 Hz, C4), 138.5 (d, 3 31 J( P−13C) = 1.9 Hz, C6), 133.2 (d, 2J(31P−13C) = 18.2 Hz, Co), 131.6 (d, 1J(31P−13C) = 7.5 Hz, Ci or C5), 130.6 (d, 1J(31P−13C) = 16.8 Hz, C5 or Ci), 128.3 (d, 3J(31P−13C) = 6.3 Hz, Cm), 128.0 (s, Cp), 119.8 (s, C8), 119.4 (s, C3), 30.0 (s, C1 or C2), 30.0 (s, C2 or C1), 0.6 ppm (d, J(31P−13C) = 19.0 Hz, CH3). 29Si{1H} NMR (CDCl3): δ = −19.7 ppm (d, J(31P−29Si) = 12.0 Hz). 31P{1H} NMR (CDCl3): δ = −15.4 ppm (s). HREIMS: calcd for C26H24PSi 395.13849, found 395.13945 [M − H]+. IR: νSiH = 2161 cm−1. Anal. Calcd for C26H25PSi (396.54): C, 78.75; H, 6.35. Found: C, 78.7; H, 6.5. Synthesis of (5-(Diphenylphosphinosulfide)acenaphth-6-yl)dimethylsilane, 5-Ph2P(S)-Ace-6-SiMe2H (1S). Sulfur (4.10 mg, 0.13 mmol) was added to a solution of 1 (50.0 mg, 0.13 mmol) and tetrahydrofuran (2 mL) and stirred under reflux for 3 d. Recrystallization by carefully overlaying n-hexane (2 mL) to the reaction mixture yielded 1S as colorless crystals (23.5 mg, 0.05 mmol, 43%, mp 172 °C). 1 H NMR (CDCl3): δ = 7.77 (d, 3J(1H−1H) = 7.1 Hz, 1H, H-7 or H-8), 7.67−7.62 (m, 4H), 7.44−7.39 (m, 2H), 7.36−7.30 (m, 6H), 7.02 (d, 3J(1H−1H) = 7.3 Hz, 1H, H-8 or H-7), 5.15 (sept, 3J(1H−1H) = 3.3 Hz, 1J(29Si−1H) = 210.1 Hz, 1H, SiH), 3.33−3.27 (m, 4H, H1,2), 0.04 (d, 3J(1H−1H) = 3.4 Hz, 2J(29Si−1H) = 120.7 Hz, 6H, CH3). 13 C{1H} NMR (CDCl3): δ = 153.0 (d, 4J(31P−13C) = 3.1 Hz, Cc or Cd), 148.6 (d, 4J(31P−13C) = 1.8 Hz, Cd or Cc), 140.1 (d, J(31P−13C) = 11.3, Ca or Cb), 139.0 (s, C7), 138.3 (d, 2J(31P−13C) = 12.7 Hz, C4), 135.7 (d, J(31P−13C) = 10.0 Hz, Cb or Ca), 135.8 (d, 1J(31P−13C) = 86.2 Hz, Ci or C5), 132.4 (d, 2J(31P−13C) = 10.1 Hz, Co), 131.0 (d, 4 31 J( P−13C) = 2.9 Hz, Cp), 128.4 (d, 3J(31P−13C) = 12.6 Hz, Cm), 124.9 (d, 1J(31P−13C) = 82.8 Hz, C5 or Ci), 120.2 (s, C8), 117.9 (d, 3 31 J( P−13C) = 14.6 Hz, C6 or C3), 29.9 (s, C1 or C2), 29.8 (s, C2 or C1), −0.1 ppm (s, 1J(29Si−13C) = 52.4 Hz, CH3). 29Si{1H} NMR (CDCl3): δ = −20.7 ppm (s). 31P{1H} NMR (CDCl3): δ = 50.5 ppm. HREIMS: calcd for C26H24PSSi 427.11056, found 427.10926 [M − H]+. IR: νSiH = 2221 cm−1. Anal. Calcd for C26H25PSSi (428.60): C, 72.86; H, 5.88. Found: C, 72.0; H, 5.6. Synthesis of (5-(diphenylphosphinoselenide)acenaphth-6-yl)dimethylsilane, 5-Ph2P(Se)-Ace-6-SiMe2H (1Se). Selenium (10.0 mg, 0.13 mmol) was added to a solution of 1 (50.0 mg, 0.13 mmol) and tetrahydrofuran (2 mL), and the mixture was stirred under reflux for 3 d. Recrystallization by carefully overlaying n-hexane (2 mL) to the

reaction mixture yielded 1Se as colorless crystals (34.3 mg, 0.07 mmol, 57%, mp 155 °C (dec)). 1 H NMR (CDCl3): δ = 7.87 (d, 3J(1H−1H) = 7.0 Hz, 1H, H-7 or H-8), 7.82−7.76 (m, 4H), 7.52−7.41 (m, 8H), 7.12 (d, 3J(1H−1H) = 7.3 Hz, 1H, H-8 or H-7), 5.05 (sept, br, 1J(29Si−1H) = 210.6 Hz, 1H, SiH), 3.43−3.36 (m, 4H, H-1,2), 0.12 (s, br, 2J(29Si−1H) = 117.9 Hz, 6H, CH3). 13C{1H} NMR (CDCl3): δ = 153.1 (d, 4J(31P−13C) = 3.2 Hz, Cc or Cd), 148.6 (d, 4J(31P−13C) = 1.7 Hz, Cd or Cc), 140.1 (d, J(31P−13C) = 11.5 Hz, Ca or Cb), 138.9 (s, C7), 137.9 (d, 2J(31P−13C) = 12.4 Hz, C4), 135.7 (d, J(31P−13C) = 10.6 Hz, Cb or Ca), 134.3 (d, 1 31 J( P−13C) = 77.1 Hz, Ci or C5), 134.1 (s, C3 or C6), 132.9 (d, 2 31 J( P−13C) = 10.3 Hz, Co), 131.0 (d, 4J(31P−13C) = 2.8 Hz, Cp), 128.4 (d, 3J(31P−13C) = 12.5 Hz, Cm), 124.0 (d, 1J(31P−13C) = 73.7 Hz, C5 or Ci), 120.3 (s, C8), 118.1 (d, 3J(31P−13C) = 14.3 Hz, C6 or C3), 29.9 (s, C1 or C2), 29.7 (s, C2 or C1), −0.1 ppm (s, 1J(29Si−13C) = 52.0 Hz, CH3). 29Si{1H} NMR (CDCl3): δ = −20.4 ppm (s). 31P{1H} NMR (CDCl3): δ = 41.1 ppm (s, 1J(77Se−31P) = 723.7 Hz). 77Se{1H} NMR (CDCl3): δ = −209.0 ppm (d, 1J(31P−77Se) = 692.0 Hz). HREIMS: calcd for C26H24PSeSi 475.05501, found 475.05509 [M − H]+. IR: νSiH = 2214 cm−1. Anal. Calcd for C26H25PSeSi (475.50): C, 65.67; H, 5.30. Found: C, 65.8; H, 5.6. Synthesis of (5-(diphenylphosphino)acenaphth-6-yl)dimethylchlorosilane, 5-Ph2P-Ace-6-SiMe2Cl (2). Method (i): To a suspension of 5-bromo-6-diphenylphosphinoacenaphthene (0.50 g, 1.20 mmol) and diethyl ether (5 mL) 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, and the mixture was stirred for 2 h at this temperature. The suspension was allowed to warm to rt and stirred for 1 h, and dichlorodimethylsilane (0.15 g, 1.20 mmol) was added. The reaction mixture was stirred at rt overnight. 31P{1H} NMR showed a sole chemical shift at −17.6 ppm, indicating complete conversion of 5-Ph2P-Ace-6-Li. The crude 5-Ph2P-Ace-6-SiMe2Cl (2) was used without further workup. Method (ii): A solution of 5-Ph2PAce-6-SiMe2H (1, 0.25 g, 0.63 mmol) and carbon tetrachloride (8 mL) in the presence of palladium dichloride (11.0 mg, 0.06 mmol) was stirred under reflux for 5 h. The reaction mixture was filtered, and the solvent was removed under reduced pressure to give 2 as a yellow oil (0.26 g, 0.60 mmol, 95%). 1 H NMR (CDCl3): δ = 8.72 (d, 3J(1H−1H) = 7.2 Hz, 1H, H-7 or H-8), 7.61 (dd, 3J(1H-1H) = 7.1 Hz, J(31P−1H) = 5.2 Hz, 1H, H-3 or H-4), 7.48 (d, 3J(1H−1H) = 7.2 Hz, 1H, H-8 or H-7), 7.43−7.32 (m, 11H), 3.48 (m, 4H, H-1,2), 1.21 ppm (d, J(31P−1H) = 9.6 Hz, 2 29 J( Si−1H) = 122.4 Hz, 6H, CH3). 13C{1H} NMR (CDCl3): δ = 150.5 (s, Cc or Cd), 149.7 (d, 4J(31P−13C) = 2.3 Hz, Cd or Cc), 141.1 (d, 3J(31P−13C) = 3.0 Hz, C6), 140.6 (d, 2J(31P−13C) = 37.4 Hz, Ca), 139.6 (d, 3J(31P−13C) = 10.0 Hz, Cb), 138.4 (d, 4J(31P−13C) = 1.6 Hz, C7), 136.6 (d, 2J(31P−13C) = 6.0 Hz, C4), 132.7 (d, 2J(31P−13C) = 16.2 Hz, Co), 128.5 (d, 3J(31P−13C) = 6.6 Hz, Cm), 128.5 (s, Cp), 127.4 (d, 1 31 J( P−13C) = 5.5 Hz, Ci or C5), 120.0 (d, 3J(31P−13C) = 1.8 Hz,C3), 119.6 (s, C8), 30.2 (s, C1 or C2), 29.9 (s, C2 or C1), 9.4 ppm (d, J(31P−13C) = 30.1 Hz, CH3). 29Si{1H} NMR (CDCl3): δ = 9.4 ppm (s). 31P{1H} NMR (CDCl3): δ = −17.6 ppm (s). Synthesis of (5-(Diphenylphosphino)acenaphth-6-yl)dimethylsilanole, 5-Ph2P-Ace-6-SiMe2OH (3). A solution of ammonia carbonate (0.07 g, 0.72 mmol) and sodium chloride (1.75 g, 29.9 mmol) in water (5 mL) was added to diethyl ether (5 mL). The crude solution of 2 (0.52 g, 1.20 mmol) and diethyl ether (see synthesis of 2, method (i)) was slowly poured into the vigorously stirred diethyl ether/water mixture at rt. The organic phase was separated after 1 h, washed three times with water, and dried over magnesium sulfate. The solvent was removed by rotary evaporation, affording 3 as a yellow oil (0.27 mg, 0.65 mmol, 55%). 1 H NMR (CDCl3): δ = 8.01 (d, 3J(1H−1H) = 7.1 Hz, 1H, H-7 or H-8), 7.50 (dd, 3J(1H−1H) = 7.1 Hz, J(31P−1H) = 5.6 Hz, 1H, H-3 or H-4), 7.30−7.24 (m, 12H), 4.49 (br, 1H, OH), 3.33 (m, 4H, H-1,2), 0.53 ppm (d, J(31P−1H) = 3.3 Hz, 2J(29Si−1H) = 118.9 Hz, 6H, CH3). 13 C{1H} NMR (CDCl3): δ = 150.4 (s, Cc or Cd), 149.1 (d, 4 31 J( P−13C) = 2.0 Hz, Cd or Cc), 140.1 (d, 2J(31P−13C) = 33.7 Hz, Ca), 139.8 (d, 3J(31P−13C) = 9.8 Hz, Cb), 139.3 (d, 3J(31P−13C) = 1.7 Hz, L


Article

Organometallics C6), 138.3 (s, C7), 136.7 (d, 2J(31P−13C) = 3.6 Hz, C4), 133.9 (d, 1 31 J( P−13C) = 19.6 Hz, Ci or C5), 132.9 (d, 2J(31P−13C) = 17.7 Hz, Co), 128.5 (d, 3J(31P−13C) = 6.9 Hz, Cm), 128.5 (s, Cp), 119.8 (d, 3 31 J( P−13C) = 1.7 Hz, C3), 119.2 (s, C8), 29.9 (s, C1 or C2), 29.8 (s, C2 or C1), 3.3 ppm (d, J(31P−13C) = 10.5 Hz, CH3, 1J(29Si−13C) = 64.1 Hz). 29Si{1H} NMR (CDCl3): δ = −1.2 ppm (s). 31P{1H} NMR (CDCl3): δ = −14.5 ppm (s). HREIMS: calcd for C26H25OPSi 412.13886, found 412.13983 [M]+; calcd for C26H24OPSi 411.13340, found 411.13353 [M − H]+. IR: νSiOH = 3401 cm−1. Anal. Calcd for C26H25OPSi (412.54): C, 75.70; H, 6.11. Found: C, 75.1; H, 6.7. Synthesis of (5-(Diphenylphosphinoxide)acenaphth-6-yl)dimethylsilanole, 5-Ph2P(O)-Ace-6-SiMe2OH (3O). Method (i): Hydrogen peroxide (0.1 mL, 37% solution) was added to a solution of 1 (50.0 g, 0.13 mmol) and tetrahydrofuran (2 mL), and the mixture was stirred under reflux for 3 d. Recrystallization by carefully overlaying n-hexane (2 mL) to the reaction mixture yielded 3O as colorless crystals (33.5 mg, 0.08 mmol, 62%, mp 164 °C). Method (ii): Hydrogen peroxide urea (6.0 mg, 0.06 mmol) was added to a solution of 3 (25.0 g, 0.06 mmol) and tetrahydrofuran (2 mL), and the mixture was stirred at rt for 24 h. Recrystallization by carefully overlaying nhexane (2 mL) to the reaction mixture yielded 3O as colorless crystals (18.7 mg, 0.04 mmol, 72%). 1 H NMR (CDCl3): δ = 7.94 (d, 3J(1H−1H) = 7.0 Hz, 1H, H-7 or H-8), 7.53−7.39 (m, 12H), 7.20 (d, 3J(1H−1H) = 7.2 Hz, 1H, H-8 or H-7), 3.44 (m, 4H, H-1,2), 0.20 ppm (s, 2J(29Si−1H) = 118.8 Hz, CH3). 13C{1H} NMR (CDCl3): δ = 153.9 (d, 4J(31P−13C) = 3.0 Hz, Cc or Cd), 148.6 (d, 4J(31P−13C) = 1.5 Hz, Cd or Cc), 139.8 (d, J(31P−13C) = 11.3, Ca or Cb), 139.6 (s, C7), 139.4 (d, 2J(31P−13C) = 15.2 Hz, C4), 136.6 (d, J(31P−13C) = 9.2 Hz, Cb or Ca), 135.9 (s, C3 or C6), 133.5 (d, 1J(31P−13C) = 106.5 Hz, Ci or C5), 132.2 (d, 2 31 J( P−13C) = 9.7 Hz, Co), 131.8 (d, 4J(31P−13C) = 2.5 Hz, Cp), 128.4 (d, 3J(31P−13C) = 12.3 Hz, Cm), 123.2 (d, 1J(31P−13C) = 103.4 Hz, C5 or Ci), 120.0 (s, C8), 117.7 (d, 3J(31P−13C) = 15.7 Hz, C6 or C3), 30.0 (s, C1 or C2), 29.8 (s, C2 or C1), 3.1 ppm (s, 1J(29Si−13C) = 63.7 Hz, CH3). 29Si{1H} NMR (CDCl3): δ = 3.9 ppm (s). 31P{1H} NMR (CDCl3): δ = 39.5 ppm. HREIMS: calcd for C25H22O2PSi 413.11267, found 413.11070 [M − CH3]+. IR: νSiOH = 3056 cm−1. Anal. Calcd for C26H25O2PSi (428.53): C, 72.87; H, 5.88. Found: C, 72.7; H, 6.1. Synthesis of (5-(Diphenylphosphinosulfide)acenaphth-6-yl)dimethylsilanole, 5-Ph2P(S)-Ace-6-SiMe2OH (3S). Method (i): Sulfur (18.0 mg, 0.56 mmol) was added to a solution of 1S (50.0 mg, 0.11 mmol) and tetrahydrofuran (2 mL), and the mixture was stirred under reflux for 3 d. Recrystallization by carefully overlaying n-hexane (2 mL) to the reaction mixture yielded 3S as colorless crystals (27.1 mg, 0.06 mmol, 47%, mp 151 °C). Method (ii): Sulfur (2.0 mg, 0.06 mmol) was added to a solution of 3 (25.0 mg, 0.06 mmol) and tetrahydrofuran (2 mL), and the mixture was stirred under reflux for 7 d. Recrystallization by carefully overlaying n-hexane (2 mL) to the reaction mixture yielded 3S as colorless crystals (11.3 mg, 0.03 mmol, 42%). 1 H NMR (CDCl3): δ = 7.86 (d, 3J(1H−1H) = 7.1 Hz, 1H, H-7 or H-8), 7.72−7.66 (m, 4H), 7.51−7.38 (m, 8H), 7.16 (d, 3J(1H−1H) = 7.4 Hz, 1H, H-8 or H-7), 5.34 (s, 1H, OH), 3.45−3.40 (m, 4H, H1,2), 0.11 ppm (s, 2J(29Si−1H) = 126.5 Hz, CH3). 13C{1H} NMR (CDCl3): δ = 153.2 (d, 4J(31P−13C) = 3.2 Hz, Cc or Cd), 148.8 (d, 4 31 J( P−13C) = 1.9 Hz, Cd or Cc), 139.9 (d, J(31P−13C) = 11.8, Ca or Cb), 139.8 (d, 2J(31P−13C) = 13.4 Hz, C4), 138.8 (s, C7), 135.3 (d, 1 31 J( P−13C) = 85.7 Hz, Ci or C5), 132.8 (d, J(31P−13C) = 12.4 Hz, Cb or Ca), 132.2 (d, 2J(31P−13C) = 10.4 Hz, Co), 131.3 (d, 4J(31P−13C) = 2.9 Hz, Cp), 128.4 (d, 3J(31P−13C) = 12.6 Hz, Cm), 123.5 (d, 1 31 J( P−13C) = 84.0 Hz, C5 or Ci), 119.7 (s, C8), 118.0 (d, 3J(31P−13C) = 15.1 Hz, C6 or C3), 29.9 (s, C1 or C2), 29.8 (s, C2 or C1), 3.5 ppm (s, 1 29 J( Si−13C) = 67.8 Hz, CH3). 29Si{1H} NMR (CDCl3): δ = 0.5 ppm (s). 31P{1H} NMR (CDCl3): δ = 49.8 ppm. ESI MS (CH2Cl2/MeCN, 1:10, positive mode): m/z = 467.3 (C26H25OPSSiNa) for [M + Na]+. IR: νSiOH = 3402 cm−1. Anal. Calcd for C26H25OPSSi (444.60): C, 70.24. Found: C, 70.5. Synthesis of (5-(Diphenylphosphinoselenide)acenaphth-6-yl)dimethylsilanole, 5-Ph2P(Se)-Ace-6-SiMe2OH (3Se). Method (i): A solution of 1Se (50.0 mg, 0.11 mmol) and chloroform (1 mL) was left

to stand for 6 months. Recrystallization, by carefully overlaying nhexane to the reaction mixture, yielded 3Se as colorless crystals (16.5 mg, 0.03 mmol, 32%, mp 149 °C (dec)). Method (ii): Selenium (5.0 mg, 0.06 mmol) was added to a solution of 3 (25.0 mg, 0.06 mmol) and tetrahydrofuran (2 mL), and the mixture was stirred under reflux for 10 d. Recrystallization by carefully overlaying n-hexane (2 mL) to the reaction mixture yielded 3Se as colorless crystals (14.3 mg, 0.03 mmol, 48%). 1 H NMR (CDCl3): δ = 7.88 (d, 3J(1H−1H) = 7.1 Hz, 1H, H-7 or H-8), 7.75−7.69 (m, 4H), 7.50−7.37 (m, 8H), 7.15 (d, 3J(1H−1H) = 7.4 Hz, 1H, H-8 or H-7), 5.04 (s, 1H, OH), 3.44−3.38 (m, 4H, H1,2), 0.11 ppm (s, 2J(29Si−1H) = 119.0 Hz, CH3). 13C{1H} NMR (CDCl3): δ = 153.2 (d, 4J(31P−13C) = 3.3 Hz, Cc or Cd), 148.8 (d, 4 31 J( P−13C) = 2.0 Hz, Cd or Cc), 140.0 (d, J(31P−13C) = 12.2 Hz, Ca or Cb), 139.5 (d, 2J(31P−13C) = 12.7 Hz, C4), 138.5 (s, C7), 134.4 (d, 1 31 J( P−13C) = 77.5 Hz, Ci or C5), 132.6 (d, 2J(31P−13C) = 10.6 Hz, Co), 131.3 (d, 4J(31P−13C) = 3.0 Hz, Cp), 128.4 (d, 3J(31P−13C) = 12.6 Hz, Cm), 122.6 (d, 1J(31P−13C) = 75.3 Hz, C5 or Ci), 119.8 (s, C8), 118.1 (d, 3J(31P−13C) = 14.8 Hz, C6 or C3), 29.9 (s, C1 or C2), 29.8 (s, C2 or C1), 3.5 ppm (s, 1J(29Si−13C) = 64.6 Hz, CH3). 29Si{1H} NMR (CDCl3): δ = −0.2 ppm (s). 31P{1H} NMR (CDCl3): δ = 39.6 ppm (s, 1J(77Se−31P) = 687.2 Hz). 77Se{1H} NMR (CDCl3): δ = −209.0 ppm (d, 1 J( 31 P− 77 Se) = 686.6 Hz). HREIMS: calcd for C26H25OP80SeSi 492.05775, found 492.05958 [M]+; calcd for C26H25OP76SeSi 488.06044, found 488.06015 [M]+. IR: νSiOH = 3408 cm−1. Anal. Calcd for C26H25OPSeSi (491.50): C, 63.54. Found: C, 63.0. Crystallography. Intensity data were collected on Siemens P4 (1Se), STOE IPDS 2T (3S), and Bruker Venture D8 (1, 1S, 3O, 3Se) diffractometers with graphite-monochromated Mo Kα (0.7107 Å) radiation. To minimize thermal vibration, almost all data sets were collected at 173, 150, or 100 K, which, however, was not possible for 1 due to a phase transition at low temperatures. For 1 the data collection was carried out at 288 K. All structures were solved by direct methods and refined based on F2 by use of the SHELX program package as implemented in WinGX.45 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. Figures were created using DIAMOND.46 Crystallographic data (excluding structure factors) for the structural analyses have been deposited with the Cambridge Crystallographic Data Centre, CCDC nos. 1405148−1405153. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44-1223-336033; e-mail: [email protected] or http://www.ccdc.cam.ac.uk). Computational Chemistry. On the basis of X-ray structures of III−XIV and the silanes/silanols, optimizations of the gas-phase molecular geometries were performed at the B3PW91/6-311+ +G(2df,p) level of theory47 with the program package Gaussian09.48 Since no X-ray data are available for 1O and 3, the X-ray structures of 1S and 3O served as starting geometries. The reliability of all final optimized structures was verified by frequency analyses, which proved all structures to be local minima. Subsequently, topological analysis of the electron density was performed using AIM2000,49 while the ELI-D was calculated with DGrid-4.650 (grid step size 0.05 au). For the model complexes, additional NBO calculations were performed applying the NBO-5 suite.51 AIM bond path motifs are displayed with AIM2000, whereas ELI-D isosurfaces are displayed with MolIso.52

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ASSOCIATED CONTENT

S Supporting Information *

NMR spectra, crystal and refinement data, figure of relaxed gasphase molecular geometries, ED and VF topology and ELI-D isosurfaces, topological and integrated AIM, ELI-D bond properties, and NLMO bond indices. AIM and NPA atomic and fragmental charges, CIF files, and Cartesian coordinates of the optimized structures are provided separately. The M


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Organometallics

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Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.5b00489.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The Deutsche Forschungsgemeinschaft (DFG) is gratefully acknowledged for financial support. We are indebted to Dr. Ole Mallow (Technische Universität, Wien, Austria) for carrying out the elemental analyses. We are grateful to Dr. Alexander Gerisch (Bruker AXS, Karlsruhe, Germany) for invaluable advice on the X-ray structure of 1. This paper is dedicated to Professor Manfred Scheer on the occasion of his 60th birthday.

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REFERENCES

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