Substituent Effects on the Thermochemistry of Thiophenes. A Theoretical (G3(MP2)//B3LYP and G3) Study

Very good linear correlations between experimental and calculated enthalpies of formation in the gas phase (G3­(MP2)//B3LYP and G3) for 48 thiophene derivatives have been obtained. These correlations permit a correction of the calculated enthalpies of formation in order to estimate more reliable “experimental” values for the enthalpies of formation of substituted thiophenes, check the reliability of experimental measurements, and also predict the enthalpies of formation of new thiophenes that are not available in the literature. Moreover, the difference between the enthalpies of formation of isomeric thiophenes with the same substituent in positions 2 and 3 of the ring has been analyzed. Likewise, a comparison of the substituent effect in the thiophene and benzene rings has been established

Synthesis and DFT, Multinuclear Magnetic Resonance, and X‑ray Structural Studies of Iminoacyl Imido Hydridotris(3,5-dimethylpyrazolyl)borate Niobium and Tantalum(V) Complexes

Reaction of alkyl imido [MTp*XR­(N<i>t</i>Bu)] (M = Nb/Ta; Tp* = HB­(3,5-Me₂C₃HN₂)₃; X = Cl, R = Me (<b>1a</b>/<b>1b</b>), CH₂CH₃ (<b>2a</b>/<b>2b</b>), CH₂Ph (<b>3a</b>/<b>3b</b>), CH₂<i>t</i>Bu (<b>4a</b>/<b>4b</b>), CH₂SiMe₃ (<b>5a</b>/<b>5b</b>), CH₂CMe₂Ph (<b>6a</b>/<b>6b</b>); X = R = Me (<b>7a</b>/<b>7b</b>)) complexes with 1 equiv of the isocyanide 2,6-Me₂C₆H₃NC takes place with migration of an alkyl group and leads to the formation of the series of chlorido or methyl imido iminoacyl derivatives [MTp*X­(N<i>t</i>Bu)­{C­(R)­NAr-κ²<i>C</i>,<i>N</i>}] (M = Nb/Ta; Ar = 2,6-Me₂C₆H₃; X = Cl, R= Me (<b>8a</b>/<b>8b</b>), CH₂CH₃ (<b>9a</b>/<b>9b</b>), CH₂Ph (<b>10a</b>/<b>10b</b>), CH₂<i>t</i>Bu (<b>11a</b>/<b>11b</b>), CH₂SiMe₃ (<b>12a</b>/<b>12b</b>), CH₂CMe₂Ph (<b>13a</b>/<b>13b</b>); X = R = Me (<b>14a</b>/<b>14b</b>)). The molecular structure of <b>10b</b> was determined by X-ray diffraction methods. An irreversible <i>endo</i> → <i>exo</i> isomerization was detected by ¹H NMR in compounds <b>10a</b>–<b>13a.</b> The insertion–isomerization reaction coordinate was computed by DFT calculations

Functionalization Reactions Characteristic of a Robust Bicyclic Diphosphane Framework

The 3,4,8,9-tetramethyl-1,6-diphospha-bicyclo-[4.4.0]­deca-3,8-diene (P₂(C₆H₁₀)₂) framework containing a P–P bond has allowed for an unprecedented selectivity toward functionalization of a single phosphorus lone pair with reference to acyclic diphosphane molecules. Functionalization at the second phosphorus atom was found to proceed at a significantly slower rate, thus opening the pathway for obtaining mixed functional groups for a pair of P–P bonded λ⁵-phosphorus atoms. Reactivity with the chalcogen-atom donors MesCNO (Mes = 2,4,6-C₆H₂Me₃) and SSbPh₃ has allowed for the selective synthesis of the diphosphane chalcogenides OP₂(C₆H₁₀)₂ (87%), O₂P₂(C₆H₁₀)₂ (94%), SP₂(C₆H₁₀)₂ (56%), and S₂P₂(C₆H₁₀)₂ (87%). Computational studies indicate that the oxygen-atom transfer reactions involve penta-coordinated phosphorus intermediates that have four-membered {PONC} cycles. The P–E bond dissociation enthalpies in EP₂(C₆H₁₀)₂ were measured via calorimetric studies to be 134.7 ± 2.1 kcal/mol for P–O, and 93 ± 3 kcal/mol for P–S, respectively, in good agreement with the computed values. Additional reactivity with breaking of the P–P bond and formation of diphosphinate O₃P₂(C₆H₁₀)₂ was only observed to occur upon heating of dimethylsulfoxide solutions of the precursor. Reactivity of diphosphane P₂(C₆H₁₀)₂ with azides allowed the isolation of monoiminophosphoranes (RN)­P₂(C₆H₁₀)₂(R = Mes, CPh₃, SiMe₃), and treatment with additional MesN₃ yielded symmetric and unsymmetric diiminodiphosphoranes (RN)­(MesN)­P₂(C₆H₁₀)₂ (91% for R = Mes). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)₂P₂(C₆H₁₀)₂ (nppn) allowed for the isolation and characterization of (nppn)­Mo­(η³-C₃H₅)­Cl­(CO)₂ (91%), (nppn)­NiCl₂ (76%), and [(nppn)­Ni­(η³-2-C₃H₄Me)]­[OTf] showing that these ligands provide an attractive preorganized binding pocket for both late and early transition metals

Functionalization Reactions Characteristic of a Robust Bicyclic Diphosphane Framework

The 3,4,8,9-tetramethyl-1,6-diphospha-bicyclo-[4.4.0]­deca-3,8-diene (P₂(C₆H₁₀)₂) framework containing a P–P bond has allowed for an unprecedented selectivity toward functionalization of a single phosphorus lone pair with reference to acyclic diphosphane molecules. Functionalization at the second phosphorus atom was found to proceed at a significantly slower rate, thus opening the pathway for obtaining mixed functional groups for a pair of P–P bonded λ⁵-phosphorus atoms. Reactivity with the chalcogen-atom donors MesCNO (Mes = 2,4,6-C₆H₂Me₃) and SSbPh₃ has allowed for the selective synthesis of the diphosphane chalcogenides OP₂(C₆H₁₀)₂ (87%), O₂P₂(C₆H₁₀)₂ (94%), SP₂(C₆H₁₀)₂ (56%), and S₂P₂(C₆H₁₀)₂ (87%). Computational studies indicate that the oxygen-atom transfer reactions involve penta-coordinated phosphorus intermediates that have four-membered {PONC} cycles. The P–E bond dissociation enthalpies in EP₂(C₆H₁₀)₂ were measured via calorimetric studies to be 134.7 ± 2.1 kcal/mol for P–O, and 93 ± 3 kcal/mol for P–S, respectively, in good agreement with the computed values. Additional reactivity with breaking of the P–P bond and formation of diphosphinate O₃P₂(C₆H₁₀)₂ was only observed to occur upon heating of dimethylsulfoxide solutions of the precursor. Reactivity of diphosphane P₂(C₆H₁₀)₂ with azides allowed the isolation of monoiminophosphoranes (RN)­P₂(C₆H₁₀)₂(R = Mes, CPh₃, SiMe₃), and treatment with additional MesN₃ yielded symmetric and unsymmetric diiminodiphosphoranes (RN)­(MesN)­P₂(C₆H₁₀)₂ (91% for R = Mes). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)₂P₂(C₆H₁₀)₂ (nppn) allowed for the isolation and characterization of (nppn)­Mo­(η³-C₃H₅)­Cl­(CO)₂ (91%), (nppn)­NiCl₂ (76%), and [(nppn)­Ni­(η³-2-C₃H₄Me)]­[OTf] showing that these ligands provide an attractive preorganized binding pocket for both late and early transition metals

Functionalization Reactions Characteristic of a Robust Bicyclic Diphosphane Framework

The 3,4,8,9-tetramethyl-1,6-diphospha-bicyclo-[4.4.0]­deca-3,8-diene (P₂(C₆H₁₀)₂) framework containing a P–P bond has allowed for an unprecedented selectivity toward functionalization of a single phosphorus lone pair with reference to acyclic diphosphane molecules. Functionalization at the second phosphorus atom was found to proceed at a significantly slower rate, thus opening the pathway for obtaining mixed functional groups for a pair of P–P bonded λ⁵-phosphorus atoms. Reactivity with the chalcogen-atom donors MesCNO (Mes = 2,4,6-C₆H₂Me₃) and SSbPh₃ has allowed for the selective synthesis of the diphosphane chalcogenides OP₂(C₆H₁₀)₂ (87%), O₂P₂(C₆H₁₀)₂ (94%), SP₂(C₆H₁₀)₂ (56%), and S₂P₂(C₆H₁₀)₂ (87%). Computational studies indicate that the oxygen-atom transfer reactions involve penta-coordinated phosphorus intermediates that have four-membered {PONC} cycles. The P–E bond dissociation enthalpies in EP₂(C₆H₁₀)₂ were measured via calorimetric studies to be 134.7 ± 2.1 kcal/mol for P–O, and 93 ± 3 kcal/mol for P–S, respectively, in good agreement with the computed values. Additional reactivity with breaking of the P–P bond and formation of diphosphinate O₃P₂(C₆H₁₀)₂ was only observed to occur upon heating of dimethylsulfoxide solutions of the precursor. Reactivity of diphosphane P₂(C₆H₁₀)₂ with azides allowed the isolation of monoiminophosphoranes (RN)­P₂(C₆H₁₀)₂(R = Mes, CPh₃, SiMe₃), and treatment with additional MesN₃ yielded symmetric and unsymmetric diiminodiphosphoranes (RN)­(MesN)­P₂(C₆H₁₀)₂ (91% for R = Mes). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)₂P₂(C₆H₁₀)₂ (nppn) allowed for the isolation and characterization of (nppn)­Mo­(η³-C₃H₅)­Cl­(CO)₂ (91%), (nppn)­NiCl₂ (76%), and [(nppn)­Ni­(η³-2-C₃H₄Me)]­[OTf] showing that these ligands provide an attractive preorganized binding pocket for both late and early transition metals

Functionalization Reactions Characteristic of a Robust Bicyclic Diphosphane Framework

The 3,4,8,9-tetramethyl-1,6-diphospha-bicyclo-[4.4.0]­deca-3,8-diene (P₂(C₆H₁₀)₂) framework containing a P–P bond has allowed for an unprecedented selectivity toward functionalization of a single phosphorus lone pair with reference to acyclic diphosphane molecules. Functionalization at the second phosphorus atom was found to proceed at a significantly slower rate, thus opening the pathway for obtaining mixed functional groups for a pair of P–P bonded λ⁵-phosphorus atoms. Reactivity with the chalcogen-atom donors MesCNO (Mes = 2,4,6-C₆H₂Me₃) and SSbPh₃ has allowed for the selective synthesis of the diphosphane chalcogenides OP₂(C₆H₁₀)₂ (87%), O₂P₂(C₆H₁₀)₂ (94%), SP₂(C₆H₁₀)₂ (56%), and S₂P₂(C₆H₁₀)₂ (87%). Computational studies indicate that the oxygen-atom transfer reactions involve penta-coordinated phosphorus intermediates that have four-membered {PONC} cycles. The P–E bond dissociation enthalpies in EP₂(C₆H₁₀)₂ were measured via calorimetric studies to be 134.7 ± 2.1 kcal/mol for P–O, and 93 ± 3 kcal/mol for P–S, respectively, in good agreement with the computed values. Additional reactivity with breaking of the P–P bond and formation of diphosphinate O₃P₂(C₆H₁₀)₂ was only observed to occur upon heating of dimethylsulfoxide solutions of the precursor. Reactivity of diphosphane P₂(C₆H₁₀)₂ with azides allowed the isolation of monoiminophosphoranes (RN)­P₂(C₆H₁₀)₂(R = Mes, CPh₃, SiMe₃), and treatment with additional MesN₃ yielded symmetric and unsymmetric diiminodiphosphoranes (RN)­(MesN)­P₂(C₆H₁₀)₂ (91% for R = Mes). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)₂P₂(C₆H₁₀)₂ (nppn) allowed for the isolation and characterization of (nppn)­Mo­(η³-C₃H₅)­Cl­(CO)₂ (91%), (nppn)­NiCl₂ (76%), and [(nppn)­Ni­(η³-2-C₃H₄Me)]­[OTf] showing that these ligands provide an attractive preorganized binding pocket for both late and early transition metals

Functionalization Reactions Characteristic of a Robust Bicyclic Diphosphane Framework

The 3,4,8,9-tetramethyl-1,6-diphospha-bicyclo-[4.4.0]­deca-3,8-diene (P₂(C₆H₁₀)₂) framework containing a P–P bond has allowed for an unprecedented selectivity toward functionalization of a single phosphorus lone pair with reference to acyclic diphosphane molecules. Functionalization at the second phosphorus atom was found to proceed at a significantly slower rate, thus opening the pathway for obtaining mixed functional groups for a pair of P–P bonded λ⁵-phosphorus atoms. Reactivity with the chalcogen-atom donors MesCNO (Mes = 2,4,6-C₆H₂Me₃) and SSbPh₃ has allowed for the selective synthesis of the diphosphane chalcogenides OP₂(C₆H₁₀)₂ (87%), O₂P₂(C₆H₁₀)₂ (94%), SP₂(C₆H₁₀)₂ (56%), and S₂P₂(C₆H₁₀)₂ (87%). Computational studies indicate that the oxygen-atom transfer reactions involve penta-coordinated phosphorus intermediates that have four-membered {PONC} cycles. The P–E bond dissociation enthalpies in EP₂(C₆H₁₀)₂ were measured via calorimetric studies to be 134.7 ± 2.1 kcal/mol for P–O, and 93 ± 3 kcal/mol for P–S, respectively, in good agreement with the computed values. Additional reactivity with breaking of the P–P bond and formation of diphosphinate O₃P₂(C₆H₁₀)₂ was only observed to occur upon heating of dimethylsulfoxide solutions of the precursor. Reactivity of diphosphane P₂(C₆H₁₀)₂ with azides allowed the isolation of monoiminophosphoranes (RN)­P₂(C₆H₁₀)₂(R = Mes, CPh₃, SiMe₃), and treatment with additional MesN₃ yielded symmetric and unsymmetric diiminodiphosphoranes (RN)­(MesN)­P₂(C₆H₁₀)₂ (91% for R = Mes). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)₂P₂(C₆H₁₀)₂ (nppn) allowed for the isolation and characterization of (nppn)­Mo­(η³-C₃H₅)­Cl­(CO)₂ (91%), (nppn)­NiCl₂ (76%), and [(nppn)­Ni­(η³-2-C₃H₄Me)]­[OTf] showing that these ligands provide an attractive preorganized binding pocket for both late and early transition metals

Functionalization Reactions Characteristic of a Robust Bicyclic Diphosphane Framework

The 3,4,8,9-tetramethyl-1,6-diphospha-bicyclo-[4.4.0]­deca-3,8-diene (P₂(C₆H₁₀)₂) framework containing a P–P bond has allowed for an unprecedented selectivity toward functionalization of a single phosphorus lone pair with reference to acyclic diphosphane molecules. Functionalization at the second phosphorus atom was found to proceed at a significantly slower rate, thus opening the pathway for obtaining mixed functional groups for a pair of P–P bonded λ⁵-phosphorus atoms. Reactivity with the chalcogen-atom donors MesCNO (Mes = 2,4,6-C₆H₂Me₃) and SSbPh₃ has allowed for the selective synthesis of the diphosphane chalcogenides OP₂(C₆H₁₀)₂ (87%), O₂P₂(C₆H₁₀)₂ (94%), SP₂(C₆H₁₀)₂ (56%), and S₂P₂(C₆H₁₀)₂ (87%). Computational studies indicate that the oxygen-atom transfer reactions involve penta-coordinated phosphorus intermediates that have four-membered {PONC} cycles. The P–E bond dissociation enthalpies in EP₂(C₆H₁₀)₂ were measured via calorimetric studies to be 134.7 ± 2.1 kcal/mol for P–O, and 93 ± 3 kcal/mol for P–S, respectively, in good agreement with the computed values. Additional reactivity with breaking of the P–P bond and formation of diphosphinate O₃P₂(C₆H₁₀)₂ was only observed to occur upon heating of dimethylsulfoxide solutions of the precursor. Reactivity of diphosphane P₂(C₆H₁₀)₂ with azides allowed the isolation of monoiminophosphoranes (RN)­P₂(C₆H₁₀)₂(R = Mes, CPh₃, SiMe₃), and treatment with additional MesN₃ yielded symmetric and unsymmetric diiminodiphosphoranes (RN)­(MesN)­P₂(C₆H₁₀)₂ (91% for R = Mes). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)₂P₂(C₆H₁₀)₂ (nppn) allowed for the isolation and characterization of (nppn)­Mo­(η³-C₃H₅)­Cl­(CO)₂ (91%), (nppn)­NiCl₂ (76%), and [(nppn)­Ni­(η³-2-C₃H₄Me)]­[OTf] showing that these ligands provide an attractive preorganized binding pocket for both late and early transition metals

Functionalization Reactions Characteristic of a Robust Bicyclic Diphosphane Framework

The 3,4,8,9-tetramethyl-1,6-diphospha-bicyclo-[4.4.0]­deca-3,8-diene (P₂(C₆H₁₀)₂) framework containing a P–P bond has allowed for an unprecedented selectivity toward functionalization of a single phosphorus lone pair with reference to acyclic diphosphane molecules. Functionalization at the second phosphorus atom was found to proceed at a significantly slower rate, thus opening the pathway for obtaining mixed functional groups for a pair of P–P bonded λ⁵-phosphorus atoms. Reactivity with the chalcogen-atom donors MesCNO (Mes = 2,4,6-C₆H₂Me₃) and SSbPh₃ has allowed for the selective synthesis of the diphosphane chalcogenides OP₂(C₆H₁₀)₂ (87%), O₂P₂(C₆H₁₀)₂ (94%), SP₂(C₆H₁₀)₂ (56%), and S₂P₂(C₆H₁₀)₂ (87%). Computational studies indicate that the oxygen-atom transfer reactions involve penta-coordinated phosphorus intermediates that have four-membered {PONC} cycles. The P–E bond dissociation enthalpies in EP₂(C₆H₁₀)₂ were measured via calorimetric studies to be 134.7 ± 2.1 kcal/mol for P–O, and 93 ± 3 kcal/mol for P–S, respectively, in good agreement with the computed values. Additional reactivity with breaking of the P–P bond and formation of diphosphinate O₃P₂(C₆H₁₀)₂ was only observed to occur upon heating of dimethylsulfoxide solutions of the precursor. Reactivity of diphosphane P₂(C₆H₁₀)₂ with azides allowed the isolation of monoiminophosphoranes (RN)­P₂(C₆H₁₀)₂(R = Mes, CPh₃, SiMe₃), and treatment with additional MesN₃ yielded symmetric and unsymmetric diiminodiphosphoranes (RN)­(MesN)­P₂(C₆H₁₀)₂ (91% for R = Mes). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)₂P₂(C₆H₁₀)₂ (nppn) allowed for the isolation and characterization of (nppn)­Mo­(η³-C₃H₅)­Cl­(CO)₂ (91%), (nppn)­NiCl₂ (76%), and [(nppn)­Ni­(η³-2-C₃H₄Me)]­[OTf] showing that these ligands provide an attractive preorganized binding pocket for both late and early transition metals

Functionalization Reactions Characteristic of a Robust Bicyclic Diphosphane Framework

The 3,4,8,9-tetramethyl-1,6-diphospha-bicyclo-[4.4.0]­deca-3,8-diene (P₂(C₆H₁₀)₂) framework containing a P–P bond has allowed for an unprecedented selectivity toward functionalization of a single phosphorus lone pair with reference to acyclic diphosphane molecules. Functionalization at the second phosphorus atom was found to proceed at a significantly slower rate, thus opening the pathway for obtaining mixed functional groups for a pair of P–P bonded λ⁵-phosphorus atoms. Reactivity with the chalcogen-atom donors MesCNO (Mes = 2,4,6-C₆H₂Me₃) and SSbPh₃ has allowed for the selective synthesis of the diphosphane chalcogenides OP₂(C₆H₁₀)₂ (87%), O₂P₂(C₆H₁₀)₂ (94%), SP₂(C₆H₁₀)₂ (56%), and S₂P₂(C₆H₁₀)₂ (87%). Computational studies indicate that the oxygen-atom transfer reactions involve penta-coordinated phosphorus intermediates that have four-membered {PONC} cycles. The P–E bond dissociation enthalpies in EP₂(C₆H₁₀)₂ were measured via calorimetric studies to be 134.7 ± 2.1 kcal/mol for P–O, and 93 ± 3 kcal/mol for P–S, respectively, in good agreement with the computed values. Additional reactivity with breaking of the P–P bond and formation of diphosphinate O₃P₂(C₆H₁₀)₂ was only observed to occur upon heating of dimethylsulfoxide solutions of the precursor. Reactivity of diphosphane P₂(C₆H₁₀)₂ with azides allowed the isolation of monoiminophosphoranes (RN)­P₂(C₆H₁₀)₂(R = Mes, CPh₃, SiMe₃), and treatment with additional MesN₃ yielded symmetric and unsymmetric diiminodiphosphoranes (RN)­(MesN)­P₂(C₆H₁₀)₂ (91% for R = Mes). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)₂P₂(C₆H₁₀)₂ (nppn) allowed for the isolation and characterization of (nppn)­Mo­(η³-C₃H₅)­Cl­(CO)₂ (91%), (nppn)­NiCl₂ (76%), and [(nppn)­Ni­(η³-2-C₃H₄Me)]­[OTf] showing that these ligands provide an attractive preorganized binding pocket for both late and early transition metals