CP Bond Research Articles

Conciliatory Inductive Model Explaining the Origin of Changes in the η(2)-SiH Bond Length Caused by Presence of Strongly Electronegative Atoms X (X = F, Cl) in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] (n = 0-3) Complexes.

Using three theoretical methods, QTAIM, IQA, and NCI, we analyze an influence of halogen atoms X (X = F, Cl) substituted at various positions in the -SiH3-nXn group on the charge density distribution within the η(2)-SiH bond and on the SiH bond energies in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes and isolated HSiH3-nXn molecules. It is shown that shortening of the η(2)-SiH bond in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes should be considered as a normal inductive result of halogenation. This η(2)-SiH bond's compression may, however, be overcome by a predominant elongation resulting from a contingent presence of a halogen atom at position trans to the η(2)-SiH bond. This trans effect is particularly large for bulky and highly polarizable chlorine. Moreover, peculiar properties of the trans chlorine atom are manifested in several ways. To explain the origin of all the observed changes in both the length and the electron charge distribution of the η(2)-SiH bond in investigated Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes a new model, called the Conciliatory Inductive Model, is being proposed.

Microwave-induced dppm ligand substitution in triosmium clusters: Structural and DFT evaluation of Os3 clusters containing multiply activated dppm ligands through cyclometalation, ortho metalation, and P[sbnd]C bond cleavage

Four new triosmium carbonyl complexes containing multiple dppm ligands were produced by microwave heating of solutions containing Os3(CO)12 and excess dppm. Three of these complexes, Os3(μ-H)2(CO)6(μ-dppm)[μ3-Ph2PCHP(C6H4)Ph] (2), Os3(CO)6[μ3-Ph2PCH2P(C6H4)Ph]2 (3), and Os3(μ-H)(CO)6[μ3-PhPCH2P(C6H4)Ph][μ3-PhPCH(C6H4)PPh] (4), contain two dppm ligands per Os3 unit, while the fourth, Os3(μ-H)(CO)5(dppm)[μ3-PhPCH2P(C6H4)Ph][μ3-PhPCH(C6H4)PPh] (5), is the first example of an Os3 cluster containing three dppm ligands. Microwave heating was also used to prepare the known complex Os3(μ-dppm)2(CO)8 (1) more efficiently than previously reported. The new complexes 2–5 have been characterized by IR, NMR, mass spectrometry, and X-ray crystallography. In addition, the bonding in these complexes has been examined by electronic structure calculations. All of the new complexes contain at least one dppm ligand that has undergone CH and/or CP bond activation. Complex 2 is a 48e cluster that contains one intact dppm ligand and one face-capping dppm ligand that coordinates all three osmium sites through the phosphine moieties and cyclometalated and ortho-metalated carbon atoms. Complex 3 is a 48e cluster with two ortho-metalated dppm ligands while complexes 4 and 5 are 50e clusters that possess a common metallic framework with one cyclometalated dppm ligand and one ortho-metalated dppm ligand.

Systematic studies of the influence of electronegative X (X = F and Cl) substituents on the structure of the Mn–H–Si unit and the strength of the Mn⋯([formula omitted]-SiH) [formula omitted] interaction in Cp(OC)2Mn[[formula omitted]-H(SiH3−nXn)] ([formula omitted]) complexes

Results of systematic studies of the influence of electronegative X (X=F and Cl) substituents at the SiR3 moiety on the structure of the Mn–H–Si unit and the strength of the Mn⋯(η2-SiH) σ interaction in Cp(OC)2Mn[η2-H(SiH3−nXn)] (n=0–3) complexes are presented. It is shown that the length of the η2-SiH bond depends on the position of the halogen atom at Si, the number of halogens, and the type of the halogen. Considering position of the halogen atom, it is shown that the Si⋯H distance results from two opposite effects: a slight η2-SiH bond shortening due to the presence of a halogen atom at any position at –SiH3−nXn and the more pronounced bond elongation resulting from the trans halogen atom. In order to explain the influence of an electronegative atom X on the length of the η2-SiH bond in Cp(OC)2Mn[η2-H(SiH3−nXn)] complexes a new model is proposed. It is based on a marriage of the idea of an inductive effect caused by a presence of a halogen atom being at any position relative to the η2-SiH bond and the probable ‘trans effect’ if the halogen X is present at the position trans. This model is shown to be in accord with all presented changes of the η2-SiH bond length. The influence of halogens substituted at Si on the Mn–H distance is negligible. On the contrary, one observes considerable influence on the Mn⋯Si distance.

Synthesis, Structures and Properties of Half‐Sandwich Nickel(II) Complexes with Backbone‐Modified NHC Ligands

AbstractA series of seven nickel complexes [Ni(η5‐C5H5)(X)(NHC)] (X = Cl or Br; NHC = N‐heterocyclic carbene) containing backbone‐modified NHC ligands was prepared by treatment of nickelocene with the corresponding NHC·HX salts or, in the case of complex 1h [Ni(η5‐C5H5)(Cl)(IMesO)] (IMesO = 4‐oxo‐1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene), by deprotection of the corresponding NHC ligand in complex 1g [Ni(η5‐C5H5)(Cl)(IMesOPiv)] [IMesOPiv = 4‐(pivaloyloxy)‐1,3‐bis(2,4,6‐trimethylphenyl)imidazol‐2‐ylidene]. Single‐crystal X‐ray structures were determined for complexes 1d [Ni(η5‐C5H5)(Cl)(Bn2‐bimy)] (Bn2‐bimy = 1,3‐dibenzylbenzimidazolin‐2‐ylidene), 1g and 1h. The coordination spheres around the nickel atoms resemble those of d8 NiL4 square‐planar complexes, with Ni–C(Cp) bond length differentiation and C–C bond alternation in Cp ligands being taken into account. Desymmetrization of the five‐membered heterocyclic ring and a tautomeric equilibrium were observed for complex 1h. All new complexes are efficient precatalysts in three C–C bond‐forming reactions (polymerization of styrene, polymerization of methyl methacrylate, Suzuki–Miyaura cross‐coupling).

Crystal structure of 1,1'-bis-(2-meth-oxy-carbonyl-2-methyl-prop-yl)ferrocene.

The Fe atom in the title ferrocene derivative, [Fe(C11H15O2)2], is situated on an inversion centre. As a result of the point-group symmetry -1 of the mol­ecule, the ferrocene moiety adopts a staggered conformation. The average Fe—C(Cp) bond length (Cp is cyclo­penta­dien­yl) is 2.045 (4) Å, in agreement with that of other disubstituted ferrocenes. The Fe—C bond length involving the substituted C atom is slightly longer [2.0521 (17) Å] than the remaining Fe—C bond lengths caused by the inductive effect of the methyl­ene group on the Cp ring. Apart from van der Waals forces, no significant inter­molecular inter­actions are observed in the crystal packing.

Intra-ring haptotropic rearrangements of Mn(CO)3 in fluorenyl ligands

Geometric parameters, and intra-ring haptotropic rearrangements π–π (intra-ring-HRs) ŋ5⇌ŋ3 of the manganesetricarbonyl complexes (ŋ5-9-R-C13H8)Mn(CO)3, R=But and Ph in 18e zero-valence are carried out using density functional theory DFT at PBE/TZP level. The calculated activation barriers to ŋ5⇌ŋ3 intra-ring HR in (ŋ5-9-R-C13H8)Mn(CO)3, R=But and Ph are (28.5 and 69.5kcal.mol−1 respectively). The compute of HOMA and FLU indexes indicates the reduction of aromaticity when going from free to coordinated complex. The energy decomposition analysis reveals the dominant ionic character in manganese–Cp bond in the presence of covalent contribution.

Tuning the Polymerization Behavior of Silicon-Bridged [1]Ferrocenophanes Using Bulky Substituents

Sila[1]ferrocenophanes bearing bulky nitrogen- and silicon-based substituents at the ansa bridge have been prepared by nucleophilic substitution of chloride at silicon in Fe(η5-C5H4)2SiClH (3) by Li[N(SiMe3)2] and K[Si(SiMe3)3]. The resulting compounds, Fe(η5-C5H4)2Si[N(SiMe3)2]H (4) and Fe(η5-C5H4)2Si[Si(SiMe3)3]H (5), have been fully characterized, and their ring-opening polymerization (ROP) chemistry has been explored. Upon heating for 3 h, 4 yields the polymer [(η5-C5H4)Fe(η5-C5H4)Si{N(SiMe3)2}H]n (Mn = 38 000 Da, PDI = 7.5), but 5 does not react due to the larger steric bulk of the substituent on silicon. ROP initiated by Na[C5H5] under photolytic conditions involving Fe−Cp bond cleavage occurred for both 4 and 5, to afford (η5-C5H5)Fe(η5-C5H4)[SiRH(η5-C5H4)Fe(η5-C5H4)]n−1SiRH(η1-C5H5) (R = N(SiMe3)2: n = 20 and 60; R = Si(SiMe3)3: n = 20 and 50), but anionic ROP initiated with nBuLi was unsuccessful, presumably due to the close proximity of the bulky group to the site of nucleophilic attack. The pol...

Palladium‐Catalyzed Arylation of Olefins by Triarylphosphines via CP Bond Cleavage

AbstractCH Arylation of olefins by triarylphosphines via CP bond cleavage has been achieved with either Pd0 or PdII catalysts. A variety of olefins and triarylphosphines are tolerated, and we inferred that both Pd0 and PdII could function directly without pre‐oxidation or pre‐reduction.

Phosphate group vibrational signatures of the osteoporosis drug alendronate

The infrared (IR) and Raman spectra of the osteoporosis drug alendronate in the monosodium trihydrate alendronate crystal were measured. In order to interpret them, density functional theory (DFT) calculations for the solvated alendronate molecule were performed following the structural features revealed by X‐ray data. A comparison between the DFT‐calculated IR and Raman of the converged species and the measured spectra unveils relevant phosphate group signatures in the 400–1400 cm−1 wavenumber range, especially IR absorption bands at 1015, 1049, 1067, 1131, 1177, and 1235 cm−1, which were related to CP and OP bond length stretching, and Raman lines at 449, 661, and 969 cm−1, involving phosphate scissors and bond length vibrations. A comparison with experimental data of alendronate incorporated into hydroxyapatite (HAP) indicates that, for wavenumbers below 1500 cm−1, the interaction of alendronate with HAP does not affect significantly the alendronate vibrational spectra, while for the 1600–3000 cm−1 interval the interaction with HAP changes the normal mode wavenumbers by about −100 cm−1. Copyright © 2014 John Wiley & Sons, Ltd.

Functionalization of Complexed N2O in Bis(pentamethylcyclopentadienyl) Systems of Zirconium and Titanium.

Methyl triflate reacts with the metastable azoxymetallacyclopentene complex Cp*2Zr(N(O)NCPhCPh), generated in situ from nitrous oxide insertion into the Zr–C bond of Cp*2Zr(η2-PhCCPh) at −78 °C, to afford the salt [Cp*2Zr(N(O)N(Me)CPhCPh)][O3SCF3] (1) in 48% isolated yield. A single-crystal X-ray structure of 1 features a planar azoxymetallacycle with methyl alkylation taking place only at the β-nitrogen position of the former Zr(N(O)NCPhCPh) scaffold. In addition to 1, the methoxy-triflato complex Cp*2Zr(OMe)(O3SCF3) (2) was also isolated from the reaction mixture in 26% yield and fully characterized, including its independent synthesis from the alkylation of Cp*2Zr=O(NC5H5) with MeO3SCF3. Complex 2 could also be observed, spectroscopically, from the thermolysis of 1 (80 °C, 2 days). In contrast to Cp*2Zr(N(O)NPhCCPh), the more stable titanium N2O-inserted analogue, Cp*2Ti(N(O)NCPhCPh), reacts with MeO3SCF3 to afford a 1:1 mixture of regioisomeric salts, [Cp*2Ti(N(O)N(Me)CPhCPh)][O3SCF3] (3) and [Cp*2Ti(N(OMe)NCPhCPh)][O3SCF3] (4), in a combined 65% isolated yield. Single-crystal X-ray diffraction studies of a cocrystal of 3 and 4 show a 1:1 mixture of azoxymetallacyle salts resulting from methyl alkylation at both the β-nitrogen and the β-oxygen of the former Ti(N(O)NCPhCPh ring. As opposed to alkylation reactions, the one-electron reduction of Cp*2Ti(N(O)NCPhCPh) with KC8, followed by encapsulation with the cryptand 2,2,2-Kryptofix, resulted in the isolation of the discrete radical anion [K(2,2,2-Kryptofix)][Cp*2Ti(N(O)NCPhCPh)] (5) in 68% yield. Complex 5 was studied by single-crystal X-ray diffraction, and its solution X-band EPR spectrum suggested a nonbonding σ-type wedge hybrid orbital on titanium, d(z2)/d(x2–y2), houses the unpaired electron, without perturbing the azoxymetallacycle core in Cp*2Ti(N(O)NCPhCPh). Theoretical studies of Ti and the Zr analogue are also presented and discussed.

Theoretical Study of the Mechanism of CO and Acetylene Migratory Insertions into Pt–Cp* Bonds

Density functional theory computation for the reaction of Cp*Pt(CO)I with PMe3 indicates that insertion of CO into the Pt–Cp* bond of Cp*Pt(CO)(PMe3)I proceeds via interaction of a π orbital of Cp* with a π* orbital of CO. A similar pathway is predicted for an insertion reaction of the acetylene complex Cp*Pt(C2H2)(PMe3)I. The conventional mechanism for CO and acetylene insertions, involving direct insertion into the Pt–C bond, is shown to be inoperative in this system.

Density Functional Theory Study of Oxygen-Atom Insertion into Metal–Methyl Bonds of Iron(II), Ruthenium(II), and Osmium(II) Complexes: Study of Metal-Mediated C–O Bond Formation

Metal-mediated C-O bond formation is a key step in hydrocarbon oxygenation catalytic cycles; however, few examples of this reaction have been reported for low-oxidation-state complexes. Oxygen insertion into a metal-carbon bond of Cp*M(CO)(OPy)R (Cp* = η(5)-pentamethylcyclopentadienyl; R = Me, Ph; OPy = pyridine-N-oxide; M = Fe, Ru, Os) was analyzed via density functional theory calculations. Oxygen-atom insertions through a concerted single-step organometallic Baeyer-Villiger pathway and a two-step pathway via a metal-oxo intermediate were studied; calculations predict that the former pathway was lower in energy. The results indicated that functionalization of M-R to M-OR (R = Me, Ph) is plausible using iron(II) complexes. Starting from Cp*Fe(CO)(OPy)Ph, the intermediate Fe-oxo showed oxyl character and, thus, is best considered an Fe(III)O(•-) complex. Oxidation of the π-acid ancillary ligand CO was facile. Substitutions of CO with dimethylamide and NH3 were calculated to lower the activation barrier by ∼1-2 kcal/mol for formation of the Fe(III)O(•-) intermediate, whereas a chloride ligand raised the activation barrier to 26 kcal/mol from 22.9 kcal/mol.

Phosphonate biosynthesis and catabolism: a treasure trove of unusual enzymology

Natural product biosynthesis has proven a fertile ground for the discovery of novel chemistry. Herein we review the progress made in elucidating the biosynthetic pathways of phosphonate and phosphinate natural products such as the antibacterial compounds dehydrophos and fosfomycin, the herbicidal phosphinothricin-containing peptides, and the antimalarial compound FR-900098. In each case, investigation of the pathway has yielded unusual, and often unprecedented, biochemistry. Likewise, recent investigations have uncovered novel ways to cleave the CP bond to yield phosphate under phosphorus starvation conditions. These include the discovery of novel oxidative cleavage of the CP bond catalyzed by PhnY and PhnZ as well as phosphonohydrolases that liberate phosphate from phosphonoacetate. Perhaps the crown jewel of phosphonate catabolism has been the recent resolution of the longstanding problem of the C-P lyase responsible for reductively cleaving the CP bond of a number of different phosphonates to release phosphate. Taken together, the strides made on both metabolic and catabolic fronts illustrate an array of fascinating biochemistry.

The enzymatic conversion of phosphonates to phosphate by bacteria

Phosphonates are ubiquitous organophosphorus compounds that contain a characteristic CP bond which is chemically inert and hydrolytically stable. Bacteria have evolved pathways to metabolize these phosphonate compounds and utilize the products of these pathways as nutrient sources. This review aims to present all of the known bacterial enzymes capable of transforming phosphonates to phosphates. There are three major classes of enzymes known to date performing such transformations: phosphonatases, the C-P lyase complex and an oxidative pathway for CP bond cleavage. A brief description of each class is presented.

Oxygen isotope signature of UV degradation of glyphosate and phosphonoacetate: Tracing sources and cycling of phosphonates

The degradation of phosphonates in the natural environment constitutes a major route by which orthophosphate (Pi) is regenerated from organic phosphorus and recently implicated in marine methane production, with ramifications to environmental pollution issues and global climate change concerns. This work explores the application of stable oxygen isotope analysis in elucidating the CP bond cleavage mechanism(s) of phosphonates by UV photo-oxidation and for tracing their sources in the environment. The two model phosphonates used, glyphosate and phosphonoacetic acid were effectively degraded after exposure to UV irradiation. The isotope results indicate the involvement of both ambient water and atmospheric oxygen in the CP bond cleavage and generally consistent with previously posited mechanisms of UV-photon excitation reactions. A model developed to calculate the oxygen isotopic composition of the original phosphonate P-moiety, shows both synthetic phosphonates having distinctly lower values compared to naturally derived organophosphorus compounds. Such mechanistic models, based on O-isotope probing, are useful for tracing the sources and reactions of phosphonates in the environment.

Bis(diphenylphosphino)methane ligated gold cluster cations: Synthesis and gas-phase unimolecular reactivity

Electrospray ionization mass spectrometry (ESI-MS) and UV–vis spectroscopy were used to monitor the condensed phase synthesis of gold cluster cations via NaBH4 reduction of Ph3PAuCl in the presence of Ph2P-(CH2)-PPh2 (dppm, L1) a capping ligand. ESI-MS highlights that upon mixing of Ph3PAuCl and dppm a range of ligated Au(I) cations are present, including [Au2L12]2+, [Au(PPh3)2]+, [Au2L13]2+, [AuL12]+ and [Au2ClL12]+. These cationic precursors to reduction can be controlled by the ratios of the two reactants. For a ratio of 1:2 of Ph3PAuCl and dppm, [AuL12]+ is a major ion, while [Au(PPh3)2]+, which has previously been postulated to be a key precursor to gold colloid formation (J.M. Pettibone, J.W. Hudgens, Small 8 (2012) 715) is essentially absent. Upon NaBH4 reduction of a solution of this stoichiometry (Ph3PAuCl:dppm, 1:2), the following types of gold nanocluster ions are observed via ESI-MS: [Au5L13(CH(PPh2)2)]2+, [Au9L14]3+, [Au9L15]3+, [Au10L14]2+, [Au11L15]3+, [Au11L16]3+, [Au13L16]3+ and [Au14L16(CH(PPh2)2)]3+. The gas phase unimolecular chemistry of these clusters and their fragment ions were examined in a LTQ FT Hybrid Linear Ion Trap (LIT) Mass Spectrometer. Low-energy collision induced dissociation (CID) produced a range of novel gas-phase clusters of the type, [AuxL1y]z+ (x=2, 3, 6–13; y=1–6 and z=1–3) and [AuxL1y(CH(PPh2)2)]z+ (x=5, 14; y=2, 5; z=2, 3), via ligand loss and core fission fragmentation pathways. In addition fragmentation channels due to CP bond activation were also observed. Electron capture dissociation (ECD) on the Au cluster cations resulted in either one or a combination of three fragmentation channels: (i) charge reduction, (ii) charge reduction accompanied by ligand loss and/or (iii) charge reduction accompanied by CP bond activation.

Monomeric Ferrocene Bis-Imidazoline Bis-Palladacycles: Variation of Pd–Pd Distances by an Interplay of Metallophilic, Dispersive, and Coulombic Interactions

Monomeric ferrocene bis-imidazoline bis-palladacycles (FBIP) have recently been reported to be efficient bimetallic catalysts in different sorts of asymmetric reactions by the cooperation of two Pd(II) centers. A crucial parameter regarding the efficiency of reactions catalyzed in a bimetallic mode is—in general—the intermetallic distance of both catalytically relevant metal centers. In this article we describe the structural elucidation of the monomeric FBIP catalyst type (usually generated in situ from a catalytically inactive dimeric chloride bridged precatalyst) by X-ray crystal structure analysis. Two dicationic monomeric complexes are compared to a neutral complex. The solid-state structures reveal varying Pd–Pd distances ranging from 3.15 to 5.27 A for the doubly charged complexes, whereas for the neutral complex a distance of 3.28 A has been found. This variability is supposed to be one of the key advantages of a ferrocene backbone in a bimetallic catalyst system, since the Fe–Cp bonds allow the b...

Sol–gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces

Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (P(O)(OH)2). Strong covalent CP bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger “tantalum capture agent” effect of phosphonic-modified nanotubes during the sol–gel formation process of the deposits compared to nanotubes bearing oxidized functions (OH, CO, C(O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests.

The secondary phosphite selenide, CpFe(CO)2P(Se)(OiPr)2, as an organometalloligand in heterometallic M–Se–P–Fe(Cp)-type complexes [M = Cr(0), W(0), Pd(ii), Pt(ii), Au(i)

The neutral metalloligand [CpFe(CO)2P(Se)(O(i)Pr)2] (Cp = η(5)-C5H5), which contains the rare secondary phosphite selenide moiety, reacts with different metal complex precursors to form six new heterobimetallic complexes containing M-Se-P-Fe(Cp) bond connectivity. The complexes [M(CO)5{CpFe(CO)2P(Se)(O(i)Pr)2}] (M = Cr, 1; M = W, 2), [MCl2{CpFe(CO)2P(Se)(O(i)Pr)2}2] (M = Pd, 3; M = Pt, 4), [Au4Cl4{CpFe(CO)2P(Se)(O(i)Pr)2}2], 5, and [AuI{CpFe(CO)2P(Se)(O(i)Pr)2}], 6, are all heterometallic, neutral, dinuclear (1, 2, 6), trinuclear (3, 4), and hexanuclear (5) complexes. The complexes were all prepared from straightforward substitution reactions (1-5) or as an adduct, 6. All new complexes were characterized by (1)H, (31)P, (77)Se NMR, infrared spectroscopy, elemental analysis and single crystal X-ray diffraction.

Conformational stabilities from variable temperature Raman spectra, r0 structural parameters and vibrational assignments of 1,2-diphosphinoethane

Infrared spectra (3600–500cm−1) of gas, amorphous, crystalline solid and Raman spectra (3000–200cm−1) of liquid and solid were recorded. Variable temperature Raman spectra (30 to −38°C) of liquid were recorded which indicates the presence of significant amounts of six conformers at ambient temperature. Rotation about CC bond gives Trans (T) and Gauche (G) conformers and rotation around both CP bonds gives trans (t) and gauche (g) forms. Enthalpy differences for five of the lower energy conformers w.r.t. the lowest energy tTt form were determined to be 272±39cm−1, 434±40cm−1, 443±30cm−1, 663±60cm−1 and 671±34cm−1 for g′Tt, g′Tg′, g′Tg, tG′g′ and tG′t conformers, respectively, which are in the increasing order of energy. Ab initio calculations with various basis sets up to aug-cc-pVTZ were performed and to support the spectroscopic studies MP2(full)/6-31G(d) was used to predict Raman activities, infrared intensities, vibrational frequencies and band contours. By utilizing the previously reported microwave rotational constants along with MP2(full)/6-311+G(d,p) predictions, adjusted r0 parameters were obtained for two Trans and two Gauche (CC bond) conformers. The determined heavy atom structural parameters for g′Tt [g′Tg′] {tG′g′} |tG′t| conformers are: distances (Å) P1C2=1.870(3) [1.866(3)] {1.858(3)} |1.859(3)|, C2C3=1.535(3) [1.536(3)] {1.534(3)} |1.536(3)|, C3P4=1.863(3) [1.866(3)] {1.866(3)} |1.859(3)|, and angles (°) ∠P1C2C3=110.5(5) [110.4(5)] {117.0(5)} |118.5(5)|, ∠C2C3P4=115.5(5) [110.4(5)] {113.7(5)} |118.5(5)|. The results are discussed and compared to the corresponding properties of some similar molecules.