Unusual bonding in a main-group multiple-bonded system: umbrella-shaped diphosphenes

Busch, Thilo; Schoeller, Wolfgang W.; Niecke, Edgar; Nieger, Martin; Westermann, H.

doi:10.1021/ic00323a011

Cited by 35 publications

(12 citation statements)

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“…Calculations suggest that HPSi may be fairly unique among SiP compounds, as no other SiP compound with a bridged structure has been experimentally characterized to date. Similar examples have been discussed solely on the basis of quantum-chemical calculations, namely the P 2 H + ion with a cyclic structure and HPPR with electron-withdrawing substituents R. [19] In light of the present findings, it is clearly desirable to characterize experimentally the structures of other species of greater complexity, such as HPSiH 2 . [10,12] As the recent experimental detection of a fairly stable, new bridged isomer of Si 2 H 4 demonstrates, [1c] isomers with bridging H atoms may exist for other simple SiP compounds as well.…”

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confidence: 55%

Bonding in the Heavy Analogue of Hydrogen Cyanide: The Curious Case of Bridged HPSi

et al. 2010

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The bonding of first-and second-row elements differ dramatically. The simplest unsaturated silicon hydrides Si 2 H 2 and Si 2 H 4 exhibit quite unusual geometries [1] compared to the analogous hydrocarbon molecules. For example, the most stable form of Si 2 H 2 is nonplanar with C 2v symmetry and two bridging H atoms, in sharp contrast to linear acetylene, HC CH. Phosphorus and nitrogen share many of the same bonding characteristics, but P prefers single over multiple bonds. For these reasons, it may be difficult to predict the most stable isomeric arrangement, even for a small molecule with a single P or Si atom and especially when it contains both.Silicon-phosphorus bonds are important in materials science [2] and organometallic chemistry. [3] Geometries for several-hundred larger molecules containing a phosphorussilicon single bond have been determined by X-ray crystallography, [4] but the uncertainties are typically 0.05 . With respect to phosphorus-silicon multiple bonds, it appears that sterically stabilized phosphasilenes [5] R 2 Si = PR' are the only compounds that have been isolated to date. The precise structures have been determined for only two of these species, using single-crystal X-ray crystallography.[6] Our knowledge of the SiÀP bond is therefore quite inadequate.Gas-phase investigations of phosphorus-silicon compounds have been hampered by their high reactivity; consequently the structures of only a few species with Si À P bond have been accurately characterized, [7] that is, with accuracies of at least 0.05 . Nevertheless, it should be noted that small molecules containing both elements are also of astronomical interest, because silicon-and phosphorus-bearing molecules [8j have been detected in the interstellar space by radio astronomy.HPSi is perhaps the simplest unsaturated compound to have a chemical bond between silicon and phosphorus. Quantum-chemical calculations and experimental investigations [9] have shown that linear structures are by far the most stable arrangements for HCN, HNC, and the heavier analogues HNSi and HCP. Until the present investigation, no experimental data were available for HPSi, but ab initio calculations [10][11][12] concluded that a bridged structure with a SiÀ P double bond (hereafter denoted HPSi) is more stable than linear HSiP. These calculations [12] also predict an energy difference, of the order of 10 kcal mol À1 , between these forms; a transition state lying 13 kcal mol À1 above HSiP connects the two isomers. Although hydrogen bonding occurs in silicon hydrides, no phosphorus-bearing molecules with this type of bonding are known.To determine the existence, geometry, and bonding of HPSi, a study has been undertaken to measure its rotational spectrum. Rotational spectroscopy is an ideal technique to study HPSi and other polar molecules because rotational frequencies are directly related to the moments of inertia along the three principal axes of the molecule. With sufficient isotopic substitutions, it is then possible to determine highly accurate molecular...

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confidence: 55%

Bonding in the Heavy Analogue of Hydrogen Cyanide: The Curious Case of Bridged HPSi

et al. 2010

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“…This might be a result of a higher degree of p-bonding interactions involving the more electron withdrawing imidazoliumyl-group, or the large steric demand of the imidazoliumyl-substituent. 14 Interestingly, the reaction of 6 with MeOTf does not yield MeCl and 7 [OTf]. Instead, addition of MeOTf to a solution of 6 in benzene gave a yellowish reaction mixture from which 8[OTf] was conveniently obtained in good yields via addition of n-hexane and isolation of the formed precipitate (77% yield).…”

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confidence: 99%

[(^ClIm^Dipp)PP(Dipp)][GaCl₄]: a polarized, cationic diphosphene

et al. 2016

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The reaction of the neutral diphosphanide [((Cl)Im(Dipp))P-P(Cl)(Dipp)] (6) ((Cl)Im(Dipp) = 4,5-dichloro-1,3-bis(Dipp)-imidazol-2-yl; Dipp = 2,6-di-iso-propylphenyl) with methyl triflate (MeOTf) leads to the formation of cationic diphosphane [((Cl)Im(Dipp))(Me)P-P(Cl)(Dipp)](+) (8+) in a stereoselective methylation. In contrast, reacting with the Lewis acid GaCl3 yields cationic diphosphene [((Cl)Im(Dipp))P=P(Dipp)](+) (7+), which is explained by a low P-Cl bond dissociation energy. The significantly polarized P=P double bond in 7+ allows for its utilization as an acceptor for nucleophiles - the reaction with Cl(-) regenerates diphosphanide and the reaction with PMe3 gives cation [((Cl)Im(Dipp))P-P(PMe3)(Dipp)] (9+). In depth DFT investigation provides detailed insights into the bonding situation of the reported compounds.

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“…Busch et al 40 previously studied the potential energy surface of 2 as a function of the H-P-P angle at the RHF level. The CEPA-1 method was employed together with the RHF structures to estimate electron correlation effects.…”

Section: Methodsmentioning

confidence: 99%

“…On the other hand, the shorter P-P bond length results in higher destabilizations of the bridged compared to the linear structure. The structures with <f(P-P) = 1.5 A, for example, differ by about 40 keal/mol with a preference for the linear structure.54 In both cases, the bridged structure becomes destabilized relative to the linear structure with the same bond length as the X-X bond length is shortened. This finding can be rationalized with qualitative MO theory.…”

Section: Methodsmentioning

confidence: 99%

Phosphorus analogs of diazonium ions. 2. Protonation of nitrogen, phosphorus nitride, and phosphorus dimer

Glaser¹,

Horan²,

Haney³

1993

J. Phys. Chem.

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The potential energy surfaces of protonated N2, P2, and PN are explored at RHF, MP2, and CISD levels. Stationary structures were not only optimized but also characterized by computation of their vibrational frequencies at each of these levels. Model dependencies of potential energy surface characteristics, geometries, vibrational frequencies, relative isomer stabilities, and proton affinities are studied in a systematic fashion. The potential energy surface of HP2+ exhibits dramatic model dependencies and it is clarified by a scan of the potential energy surface as a function of the H-P-P angle at the CZSD level. Geometries and vibrational frequencies of the most stable isomers also are reported at the CISD(full)/6-3llG(df,p) level. Accurate scale factors for bond lengths and vibrational frequencies determined for the neutral diatomics X s X can be applied successfully to the protonated species as well. End-on protonation of Nz, edge-on protonation of P2, and N-protonation of PN are favored, and our best estimates for the proton affinities are 116.3, 161.2, and 194.2 kcal/mol, respectively.Proton affinities parallel the increase of the polarizabilities (N2 < N P < P2) but the polarizabilities perpendicular to the bond axis, ape,.,,, are significantly small than apra and their ratio apra/aperp is not related to the isomer preference energies. For protonated N2 and P2, the isomer preference is closely related to the X2 bond length per se and the structural preferences of the protonated systems thus reflect the same factors that also determine the X=X bond lengths in the neutral diatomics. The proton is atypically electrophilic compared to carbenium ions and the carbenium ion affinities of N2, P2, and PN are generally much smaller than proton affinities. While the potential energy surfaces of protonated and methylated Nz and PN are qualitatively similar, the respective derivatives of P2 differ significantly.

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Unusual bonding in a main-group multiple-bonded system: umbrella-shaped diphosphenes

Cited by 35 publications

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Bonding in the Heavy Analogue of Hydrogen Cyanide: The Curious Case of Bridged HPSi

Bonding in the Heavy Analogue of Hydrogen Cyanide: The Curious Case of Bridged HPSi

[(^ClIm^Dipp)PP(Dipp)][GaCl₄]: a polarized, cationic diphosphene

Phosphorus analogs of diazonium ions. 2. Protonation of nitrogen, phosphorus nitride, and phosphorus dimer

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Unusual bonding in a main-group multiple-bonded system: umbrella-shaped diphosphenes

Cited by 35 publications

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Bonding in the Heavy Analogue of Hydrogen Cyanide: The Curious Case of Bridged HPSi

Bonding in the Heavy Analogue of Hydrogen Cyanide: The Curious Case of Bridged HPSi

[(ClImDipp)PP(Dipp)][GaCl4]: a polarized, cationic diphosphene

Phosphorus analogs of diazonium ions. 2. Protonation of nitrogen, phosphorus nitride, and phosphorus dimer

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[(^ClIm^Dipp)PP(Dipp)][GaCl₄]: a polarized, cationic diphosphene