Single Bond Lengths Research Articles

Organosulfur oxoacids. Part 1. Synthesis, structure, and reactivity of dimethylaminoiminomethanesulfinic acid (DMAIMSA)

One of the major metabolites of dimethylthiourea, dimethylaminoiminomethanesulfinic acid (DMAIMSA), was synthesized by controlled oxidation of dimethylthiourea using hydrogen peroxide. The crystal structure was determined by X-ray crystallography. It is a zwitterionic species in its solid form, with a positive charge delocalized around an sp2-hybridized carbon center and two nitrogen atoms. It crystallizes in the triclinic P[Formula: see text] space group. The C—S bond, at 1.880(2) Å, is much longer than a typical C—S single bond length of 1.79 Å. It is also longer than the one observed in thiourea trioxide, a comparable sulfonic acid. This C—S bond is stable in acidic conditions and is easily cleaved in basic conditions or in the presence of suitable nucleophiles that can attack the positively disposed carbon center. DMAIMSA is highly reactive and easily decomposes in basic conditions to yield dithionite in the presence of oxygen, whereas in strictly anaerobic conditions it gives a mixture of sulfite and sulfide. The precursor to dithionite, SO2·–, is formed from the one-electron oxidation of the sulfoxylate anion, SO22–, which results from an initial heterolytic cleavage of the C—S bond in DMAIMSA. The sulfur center is oxidized, even by mild oxidants such as aqueous iodine, to sulfate. Key words: thiourea metabolites, synthesis, structure, reactivity.

Pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione ethylene acetal

The title mol­ecule, C13H14O3, is a chiral mol­ecule which exhibits C—C single-bond lengths that deviate from the expected value. Both enanti­omers are present in the crystal structure.

A Kinetically Stabilized Ferrocenyl Diphosphene: Synthesis, Structure, Properties, and Redox Behavior

A new, stable ferrocenyl diphosphene [Tbt-P==P-Fc] (1) (Tbt=2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Fc = ferrocenyl) was synthesized by the dehydrochlorination reaction of the corresponding diphosphane, [Tbt-P(H)-P(Cl)-Fc] (8), with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in good yield. Diphosphene 1 is very stable in the solid state and also in solution. In the 31P NMR spectrum (C6D6), diphosphene 1 showed a low-fielded AB quartet at delta 501.7 and 479.5 ppm with the coupling constant 1J(PP)=546 Hz, which is characteristic of an unsymmetrically substituted trans-diphosphene. The molecular structure of 1 was established by X-ray crystallographic analysis, which showed a trans-diphosphene with a C-P-P-C torsion angle of 177.86(17) degrees . The phosphorus-phosphorus bond length of 1 [2.0285(15) A] which is considerably shorter than the typical P-P single-bond lengths (ca. 2.22-2.24 A) and within the range of reported P=P double-bond lengths (1.985-2.051 A) for diaryl diphosphenes, evidenced the P=P double-bond character of 1 in the solid state. In addition, the cyclic voltammograms of 1 showed reversible reduction and oxidation couples at -1.95 and +0.34 V versus SCE, respectively. The electrochemical results for 1 were reasonably supported by the DFT calculations, which suggested that the LUMO and HOMO orbitals should be mainly pi* orbital of the diphosphene moiety and d orbitals of the iron(II) atom, respectively.

Formation, Structural Characterization, and Calculated NMR Chemical Shifts of Selenium‐Nitrogen Compounds from SeCl4 and ArNHLi (Ar = supermesityl, mesityl)

AbstractSupermesityl selenium diimide [Se{N(C6H2tBu3‐2, 4, 6)}2; Se{N(mes*)}2] can be prepared in a good yield from the reaction of SeCl4 and (mes*)NHLi. The molecule adopts an unprecedented anti, anti‐conformation, as deduced by DFT calculations at PBE0/TZVP level of theory and supported by 77Se NMR spectroscopy and a crystal structure determination. An analogous reaction involving (C6H2Me3‐2, 4, 6)NHLi [(mes)NHLi] unexpectedly lead to the reduction of selenium and afforded the selenium diamide Se{NH(mes)}2 that was characterized by X‐ray crystallography and 77Se NMR spectroscopy. The Se‐N bonds of 1.847(3) and 1.852(3) Å show normal single bond lengths. The <NSeN bond angle of 109.9(1)° also indicates a tetrahedral AX2E2 bonding arrangement around selenium. Two N‐H···N hydrogen bonds link the Se{NH(mes)}2 molecule with two discrete (mes)NH2 molecules. In the solid state selenium diamide adopts the anti‐conformation, whereas in solution the presence of both syn‐ and anti‐isomers could be observed. PBE0/TZVP calculations of the shielding tensors of 28 different types of selenium‐containing molecules, for which the 77Se chemical shifts are unambiguously known, were carried out to assist the spectral assignment of Se{N(mes*)}2 and Se{NH(mes)}2.

A metal-mediated dimerization of the ligand bis(N,N-diethylamino)carbeniumdithiocarboxylate.

The title compound, methylene bis[bis(N,N-diethylamino)carbeniumdithiocarboxylate] pentachlorooxorhenium, (C(21)H(42)N(4)S(4))[ReCl(5)O], is the result of an unusual dimerization of the ligand bis(N,N-diethylamino)carbeniumdithiocarboxylate [(Et(2)N)(2)C(2)S(2)] upon reaction with [ReOCl(3)(PPh(3))(2)] in chloroform under reflux conditions. The compound was obtained as a dicationic moiety, with the molecular [ReOCl(5)](2-) anion providing the charge compensation. The planes of the carbenium and thiocarboxylate moieties are nearly perpendicular to one another and the backbone C-C bond length in the N(2)CCS(2) group is the same as a normal C-C single-bond length.

Crystal structures of 1,1-di(p-substituted phenyl)-2,2-dinitroethylenes

The X-ray crystal structures of 1,1-di(p-methylphenyl)-2,2-dinitroethylene (2), 1,1-di(p-methoxylphenyl)-2,2-dinitroethylene (3), 1,1-di(p-fluorophenyl)-2,2- dinitroethylene (4), 1,1-di(p-chlorophenyl)-2,2-dinitroethylene (5), and 1-phenyl-1- (p-nitrophenyl)-2,2-dinitroethylene (6) are reported and compared with that of 1,1-diphenyl-2,2-dinitroethylene (1). Owing to steric repulsion between the aryl rings, the single bond lengths between C(1) and the two ring carbons atoms are longer than the normal sp2–sp2 bond distance of 1.46 A. For 4–6 in which the aryl rings contain electron-withdrawing substituents (F, Cl, NO2), the double bonds between C(1) and C(2) are shorter than those in 2 and 3, whose aryl rings containing electron-donating substituents. Furthermore, the steric repulsion between the aryl rings and C\(---\)NO2 fragments results in an appreciable twist about the central double bond. The two aryl rings of compounds 1–6 make dihedral angles of 77.7, 66.6, 62.8, 80.9, 82.0, and 71.2°, and the two C\(---\)NO2 fragments make dihedral angles of 68.5, 67.8, 65.9, 76.9, 73.0, and 71.9°, respectively.

Syntheses and Structures of Molybdenum(IV) Complexes with 3,5-Dimethyl- and 3,5-Di-tert-butylpyrazolato Ligands. Variable Coordination Modes and C−H Bond Activation

Treatment of tetrakis(dimethylamido)molybdenum(IV) (Mo(NMe 2 ) 4 ) with 4 equiv of 3,5-dimethylpyrazole (Me 2 pzH) in pentane yields Mo(Me 2 pzH)(Me 2 pz) 3 (η 2 -CH 2 NHCH 3 ) (1), whereby the reaction with 3,5-di-tert-butylpyrazole (t-Bu 2 pzH) leads to Mo(t-Bu 2 pz) 3 (NMe 2 ) (2), independent of the molar ratio. The homoleptic Mo(t-Bu 2 pz) 4 (3) was synthesized from tetrachlorobis(tetrahydrofurano)molybdenum(IV) (MoCl 4 (thf) 2 ) with 4 equiv of 3,5-di-tert-butylpyrazolatopotassium (t-Bu 2 pzK). Magnetic measurements show the three complexes to be paramagnetic with two unpaired electrons (1, 3.0; 2, 2.8; and 3, 2.8 μ B , respectively). The molecular structures of all compounds determined by X-ray diffraction analysis are reported. Complex 1 reveals a η 2 -coordinate CH 2 NHCH 3 ligand arranged in an azametal-lacyclic fashion, verified by a small Mo-C-N angle and a typical C-N single bond length. The bonding mode of the pyrazolato ligands in all three compounds 1, 2, and 3 is influenced by the steric bulk around the metal center leading to η 1 -, slipped η 2 -, and η 2 -coordinate ligands.

Single (C–C) and triple (CC) bond-length dependence of the static electric polarizability and hyperpolarizability of H–CC–CC–H

We report an ab initio study of the static electric (hyper)polarizability of diacetylene and its dependence on the single (C–C) and triple (CC) bond length. At the CCSD(T) level of theory we find for the mean dipole polarizability and its derivatives α ̄ =49.10 e 2 a 0 2 E h −1,( ∂ α ̄ / ∂R C− C ) e=−4.41 and ( ∂ α ̄ / ∂R C C ) e=34.57 e 2 a 0 E h −1 . For the anisotropy Δα=54.45 e 2 a 0 2 E h −1 , (∂Δ α/∂ R C–C) e =−20.42 and ( ∂Δα/ ∂R C C ) e=64.56 e 2 a 0 E h −1 . The dependence of the mean hyperpolarizability on R C–C and R CC around the equilibrium is quite distinct. Varying the single bond by Δ R/ a 0 around the equilibrium entails changes of [ γ ̄ (R C– C )− γ ̄ (R e)]/ e 4 a 0 4 E h −3=−3643 ΔR−230 ΔR 2−184 ΔR 3+453 ΔR 4 The mean second hyperpolarizability increases strongly with R C≡C around the equilibrium [ γ ̄ (R C C )− γ ̄ (R e)]/ e 4 a 0 4 E h −3=22 259 ΔR+11 293 ΔR 2+2384 ΔR 3+6445 ΔR 4

Characterization of a stable ruthenium complex with an oxyl radical.

The ruthenium oxyl radical complex, [Ru(II)(trpy)(Bu(2)SQ)O(.-)] (trpy = 2,2':6',2"-terpyridine, Bu(2)SQ = 3,5-di-tert-butyl-1,2-benzosemiquinone) was prepared for the first time by the double deprotonation of the aqua ligand of [Ru(III)(trpy)(Bu(2)SQ)(OH(2))](ClO(4))(2). [Ru(III)(trpy)(Bu(2)SQ)(OH(2))](ClO(4))(2) is reversibly converted to [Ru(III)(trpy)(Bu(2)SQ)(OH-)](+) upon dissociation of the aqua proton (pK(a) 5.5). Deprotonation of the hydroxo proton gave rise to intramolecular electron transfer from the resultant O(2-) to Ru-dioxolene. The resultant [Ru(II)(trpy)(Bu(2)SQ)O(.-)] showed antiferromagnetic behavior with a Ru(II)-semiquinone moiety and oxyl radical, the latter of which was characterized by a spin trapping technique. The most characteristic structural feature of [Ru(II)(trpy)(Bu(2)SQ)O(.-)] is a long Ru-O bond length (2.042(6) A) as the first terminal metal-O bond with a single bond length. To elucidate the substituent effect of a quinone ligand, [Ru(III)(trpy)(4ClSQ)(OH(2))](ClO(4))(2) (4ClSQ = 4-chloro-1,2-benzosemiquinone) was prepared and we compared the deprotonation behavior of the aqua ligand with that of [Ru(III)(trpy)(Bu(2)SQ)(OH(2))](ClO(4))(2). Deprotonation of the aqua ligand of [Ru(III)(trpy)(4ClSQ)(OH(2))](ClO(4))(2) induced intramolecular electron transfer from OH- to the [Ru(III)(4ClSQ)] moiety affording [Ru(II)(trpy)(4ClSQ)(OH.)]+, which then probably changed to [Ru(II)(trpy)(4ClSQ)O(.-)]. The antiferromagnetic interactions (J values) between Ru(II)-semiquinone and the oxyl radical for [Ru(II)(trpy)(Bu(2)SQ)O(.-)] and for [Ru(II)(trpy)(4ClSQ)O(.-)] were 2J = -0.67 cm(-1) and -1.97 cm(-1), respectively.

Dipropyl 3,6-diphenyl-1,2-dihydro-1,2,4,5-tetrazine-1,2-dicarboxylate.

The title compound, C(22)H(24)N(4)O(4), was prepared from propyl chloroformate and 3,6-diphenyl-1,2-dihydro-s-tetrazine. This reaction yields the title compound rather than dipropyl 3,6-diphenyl-1,4-dihydro-s-tetrazine-1,4-dicarboxylate. The 2,3-diazabutadiene group in the central six-membered ring is not planar; the C=N double-bond length is 1.285 (2) A, and the average N-N single-bond length is 1.401 (3) A, indicating a lack of conjugation. The ring has a twist conformation, in which adjacent N atoms lie +/- 0.3268 (17) A from the plane of the ring. The molecule has twofold crystallographic symmetry.

Reactions of [W2(OCH2tBu)8] (MM) with diazobenzene and trimethylsilyldiazomethane. Preparation and structures of W2(OCH2tBu)8(NPh) and W2(OCH2tBu)8(N2C(H)SiMe3)

Hydrocarbon solutions of W2(OCH2tBu)8 (MM) react with azobenzene at room temperature to give the phenylimido-bridged compound W2(μ-NPh)(μ-OCH2tBu)2(OCH2tBu)6 which has a confacial biooctahedral geometry with a W–W single bond length of 2.5613(2) Å and W–N = 1.987(3) Å (ave). Similarly, W2(OCH2tBu)8 (MM) and trimethylsilyldiazomethane react to give the 1 ∶ 1 adduct W2(μ-N2C(H)SiMe3)(μ-OCH2tBu)2(OCH2tBu)6 which has a W–W distance of 2.5626(2) Å and W–N = 1.985(1) Å (ave). The μ-N2CHSiMe3 ligand can be described as a hydrazonido(2−) ligand. The N–N distance is 1.366(4) Å and the N–N–C angle is 120.1(3)°. The NNC plane of the bridging ligand is perpendicular to the W–W bond axis. The bonding in these molecules is discussed in the light of electronic structure calculations employing density functional theory. The present findings are contrasted with related reactions involving MM multiply bonded compounds and with low valent early transition metal complexes that are similarly known to activate N–N bonds.

The stable inner salt 2,2-dimorpholino-2-ethylium-1-dithioate.

The title compound, C(10)H(16)N(2)O(2)S(2), is considered to maintain an inner-salt structure in the crystal, where the planes of the carbenium and the thiocarboxylate moieties are nearly perpendicular to each other [77 (2) degrees ], and the backbone C-C bond length [N(2)C-CS(2) 1.510 (2) A] is significantly shorter than a normal C-C single-bond length.

Crystal orbital calculation of coupled-perturbed Hartree–Fock dynamic (hyper)polarizabilities for polydiacetylene and polybutatriene

Crystal orbital coupled-perturbed Hartree–Fock static and dynamic (hyper)polarizabilities for polydiacetylene (PDA) and polybutatriene (PBT) are computed. Geometry effects have been investigated. The static CPHF/6-31G second-order hyperpolarizability of PBT is 67 times larger than that of PDA using the optimized geometries at the HF/6-31G level. However, this factor is reduced to 17 with the optimized geometries at the MP2/6-311G* level. One of the bond length alternations (BLA), the difference between the single and double bond lengths (S/D), of PDA is the most sensitive factor for the (hyper)polarizabilities. It has been shown from the calculations that a smaller S/D produces a larger polarizability and second-order hyperpolarizability of PDA. Unlike PDA, two different BLAs of PBT are competing to change the values of polarizability and second-order hyperpolarizability. The dynamic second-order hyperpolarizabilities have been checked with the general dispersion expression by fitting the results to a polynomial. Our theoretical results can also be compared with experiment and possible reasons for the discrepancies are addressed.

Comparative study of the adsorption of C 2H 4 on the Si( [formula omitted]) and Ge( [formula omitted]) surfaces

Using a first-principles pseudopotential method we have compared the interaction processes involved in the adsorption of ethylene on the silicon and germanium surfaces. We have found that, at low temperatures, the di-σ bond configuration is the most stable structure from the energetic point of view. According to our calculations C 2H 4 adsorbs preferentially on the alternate dimer sites, corresponding to a coverage of 0.5 ML. The di-σ adsorbed system is characterized by symmetric and slightly elongated Si–Si (Ge–Ge) dimers, and by a symmetric C–C bond close to the single carbon bond length of the ethane molecule. The electronic band structure derived from our calculations suggest that the adsorption of the C 2H 4 molecule leaves a surface state in the fundamental band gap that is mainly localized around the adsorbate. Finally, our ab initio vibrational spectra further support the di-σ model for the ethylene adsorption on IV(0 0 1)-(2×2).

Cyclopalladated Complexes with Functionalized Diphosphines via Activation of Chelated 1,1-Bis(diphenylphosphino)ethene

The reaction of 1 with 1,1-bis(diphenylphosphino)ethene (vdpp) gave the mononuclear cyclometalated compound 2. The withdrawing effect of the cyclopalladated moiety suffices to polarize the CCH2 double bond to afford the addition products 3−8, by treatment of complex 2 with primary aliphatic and aromatic amines. The molecular structures of 2, 4, and 8 have been determined by X-ray crystallography, showing that the C−C distance in 4 and 8 has the expected single-bond length upon addition.

The N[sbnd]O bond in covalent nitrates and nitrites

The NO single bond length in gaseous nitrates MONO2 depends strongly on the substituent M. In ‘simple’ nitrates (M=SiMe3, CH3, H, halogens, or CF3) this bond lengthens with increasing electronegativity of M from 1.383(5) Å in Me3SiONO2 to 1.507(4) Å in FONO2. In peroxynitrates ROONO2 with R=H, CF3, FC(O), CH3C(O) and CF3C(O) the NO bond length varies between 1.492(7) Å in CH3C(O)OONO2 and 1.526(10) Å in CF3C(O)OONO2. The longest bond occurs in (CF3)2NONO2 with 1.588(14) Å. This large variation of NO bond lengths can be rationalized qualitatively by different ionic contributions M+ NO3− and by partial decomposition into MO and NO2 radicals. Quantum chemical calculations with standard methods (HF, MP2 and B3LYP with 6-31G* basis sets) predict greatly different bond lengths. The HF values are too short by up to 0.19Å, the MP2 values are too long by up to 0.08Å and the B3LYP method reproduces all bond lengths very well. Only a very limited number of gas phase structures of covalent nitrites MONO has been reported. In these compounds the NO bond length varies from 1.397(6) Å in HONO to 1.572(21) Å in (CF3)2NONO. Again the B3LYP method reproduces these bond lengths better than HF or MP2 approximations. A possible exception, however, may be ClONO, where the MP2 approximation reproduces the estimated experimental value better than the B3LYP method.

The Solid State Conformation of Diaryl Ditellurides and Diselenides: The Crystal and Molecular Structures of (C4H3E2)2E'2 (E = O, S; E' = Te, Se)

The crystal and molecular structures of dithienyl ditelluride (C4H3S)2Te2 (1), difuryl ditelluride (C4H3O)2Te2 (2), dithienyl diselenide (C4H3S)2Se2 (3), and difuryl diselenide (C4H3O)2Se2 (4) are reported in this paper and compared to those of other simple diaryl ditellurides and diselenides. The chalcogen-chajcogen bonds exhibit approximately single bond lengths [Te-Te = 2.7337(8) and 2.7240(4) Å in 1 and 2, respectively; Se-Se = 2.357(1) and 2.368(2) Å in 3 and 4, respectively], as do the chalcogen-carbon bond lengths [Te-C = 2.095(9) - 2.104(6) in 1 and 2.091(6) - 2.105(9) Å in 2; Se-C = 1.87(1) - 1.90(1) Å in 3 and 1.887(8) - 1.897(10) Å in 4]. The aromatic rings are disordered. The dihedral angles C-E-E-C range from 79(2) to 96(1)° are consistent with the concept of minimized p lone-pair repulsion of adjacent chalcogen atoms. The dependence of molecular parameters on the angle between the aromatic rings and the chalcogen-chalcogen bonds follow trends established previously for aromatic disulfides. Though the bond parameters and conformations of 1 - 4 are similar, the packing of the molecules is different. The two ditellurides 1 and 2 show short Te···Te contacts (3.900 - 4.002 Å in 1 and 4.060 - 4.172 Å in 2). The two diselenides 3 and 4 do not exhibit close chalcogen-chalcogen interactions. The NMR spectroscopic properties of 1 - 4 are discussed.

Supersilylsilane R*SiX3: Darstellung, Charakterisierung und Strukturen; sterische und van-der-Waals Effekte der Substituenten X [1] / Supersilylsilanes R*SiX3: Syntheses, Characterization and Structures; Steric and van-der-Waals Effects of Substituents X [1

Supersilylsilanes R*SiX3 (R* = supersilyl = SitBu3; X = H, Me, tBu, Ph, SiMe3, F, Cl, Br, I, OMe, OSO2CF3) are prepared (i) by reactions of supersilylhalosilanes with supersilyl sodium NaR* (Hal/R* exchange), (ii) by reactions of supersilylhalosilanes with hydride H- (Hal/H exchange), (iii) by reactions of supersilylsilanes with halogens Hal2 (H/Hal exchange, R*/Hal exchange), (iv) by reactions of supersilylhalosilanes with nucleophiles like F- , MeO- (Hal/F or Hal/OMe exchange) and (v) by reactions of supersilylsilanes with strong acids (H/OSO2CF3 exchange). NMR chemical shifts δ (29Si) of the SiX3 groups of R*SiX3 strongly depends on the nature of X. The supersilylsilanes R*SiX3 are in part moisture sensitive (especially compounds with SiX3≡SiHHal2 and SiH2Hal), in part sensitive against oxygen (compounds with SiX≡SiBr or SiI), and some of them react with supersilyl sodium by supersilanidation (for example R*SiF3, R*SiH2Cl, R*SiMeHCl) or by reduction (for example R*SiCl3, R*SiMeBr2, R*SiPhBrCl). X-ray structure analyses of disilanes tBu3Si-SiX3 with SiX3≡SitBu3, SiPh3, Sil3, SiPhCl2 show a staggered conformation. Due to steric repulsion of the tBu3Si and SiX3 groups as well as van-der-Waals attraction of the substituents tBu and X in tBu3Si-SiX3 the SiSi bonds are longer than 2.34 Å (the normal SiSi single bond length) and the torsion angles are smaller/larger than 60° (the ideal staggered conformation). From the extent of SiSi bond elongation and CSiSiX angle compression it is concluded that the bulkiness of X increases in direction Cl < I < Ph < SiMe3 < CMe3 (tBu3Si-SitBu3 has to date the longest SiSi bond of all disilanes) and the van-der-Waals forces between tBu/X increase in direction tBu/I < tBu/tBu < tBu/Ph.

Interatomic distances in the stable and metastable bcc and omega structures of the transition metals: analysis of experimental and theoretical trends and correlations with Pauling’s bond lengths

The name omega (Ω) phase refers to a high-pressure modification of the transition metals (TMs) Ti, Zr, and Hf. In alloys of Ti, Zr and Hf with other TMs, the Ω phase can be formed and retained metastably at room temperature by quenching the bcc structure, which is usually the stable high-temperature phase in these alloy systems. As a part of a long-term research program on the structural and bonding properties of TM phases, we present in this paper a detailed analysis of the shortest interatomic distances (SIDs) of the stable and metastable bcc and Ω structures of the 3d, 4d and 5d TMs, as well as the connections between these and the single-bond length D (1) entering into Pauling’s classical bond length vs. bond number relation (BLBNR). The analysis involves an extensive database including experimental data, very recent ab initio calculations, and new predictions based on the BLBNR for the bcc phase of the TMs. Our results lend support to early suggestions by Jamieson of the existence of a correlation between D (1) and the SID of the Ω phase of Ti and Zr. We also find that, for most TMs, D (1) and the SID of the Ω structure differ by less than about 2%, which implies that the Jamieson correlation might be considered as a reasonably accurate first approximation in estimating IDs and lattice parameters for unknown Ω phases of the TMs.

First-principles bond-length correlation for the omega structure of the 4d-transition elements

Abstract Using the full potential-linearised muffin tin orbitals (FP-LMTO) method, we have studied the shortest interatomic distance (SID) of the AlB 2 (C32) type-structure, so-called omega (Ω) phase, of Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd and Ag. It is shown that the SID in this phase correlates remarkably well with the single bond length D (1) given to these elements by Pauling’s bond length (BL) versus bond number relation. The physical relevance of this result, which holds for stable and metastable Ω phases, lies in the identification of the quantity D (1), which for metallic elements has long represented only a useful empirical parameter, to be used in the analysis and prediction of BLs, with a structural property that can be either directly measured, or accurately calculated by current ab initio methods.