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

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

Thermodynamic, Kinetic, Structural, and Computational Studies of the Ph₃Sn–H, Ph₃Sn–SnPh₃, and Ph₃Sn–Cr(CO)₃C₅Me₅ Bond Dissociation Enthalpies

The kinetics of the reaction of Ph₃SnH with excess •Cr­(CO)₃C₅Me₅ = •<b>Cr</b>, producing H<b>Cr</b> and Ph₃Sn–<b>Cr</b>, was studied in toluene solution under 2–3 atm CO pressure in the temperature range of 17–43.5 °C. It was found to obey the rate equation <i>d</i>[Ph₃Sn–<b>Cr</b>]/<i>d</i>t = <i>k</i>[Ph₃SnH]­[•<b>Cr</b>] and exhibit a normal kinetic isotope effect (<i>k</i>_H/<i>k</i>_D = 1.12 ± 0.04). Variable-temperature studies yielded Δ<i>H</i>^‡ = 15.7 ± 1.5 kcal/mol and Δ<i>S</i>^‡ = −11 ± 5 cal/(mol·K) for the reaction. These data are interpreted in terms of a two-step mechanism involving a thermodynamically uphill hydrogen atom transfer (HAT) producing Ph₃Sn• and H<b>Cr</b>, followed by rapid trapping of Ph₃Sn• by excess •<b>Cr</b> to produce Ph₃Sn–<b>Cr</b>. Assuming an overbarrier of 2 ± 1 kcal/mol in the HAT step leads to a derived value of 76.0 ± 3.0 kcal/mol for the Ph₃Sn–H bond dissociation enthalpy (BDE) in toluene solution. The reaction enthalpy of Ph₃SnH with excess •<b>Cr</b> was measured by reaction calorimetry in toluene solution, and a value of the Sn–Cr BDE in Ph₃Sn-<b>Cr</b> of 50.4 ± 3.5 kcal/mol was derived. Qualitative studies of the reactions of other R₃SnH compounds with •<b>Cr</b> are described for R = ⁿBu, ^tBu, and Cy. The dehydrogenation reaction of 2Ph₃SnH → H₂ + Ph₃SnSnPh₃ was found to be rapid and quantitative in the presence of catalytic amounts of the complex Pd­(IPr)­(P­(<i>p</i>-tolyl)₃). The thermochemistry of this process was also studied in toluene solution using varying amounts of the Pd(0) catalyst. The value of Δ<i>H</i> = −15.8 ± 2.2 kcal/mol yields a value of the Sn–Sn BDE in Ph₃SnSnPh₃ of 63.8 ± 3.7 kcal/mol. Computational studies of the Sn–H, Sn–Sn, and Sn–Cr BDEs are in good agreement with experimental data and provide additional insight into factors controlling reactivity in these systems. The structures of Ph₃Sn–<b>Cr</b> and Cy₃Sn–<b>Cr</b> were determined by X-ray crystallography and are reported. Mechanistic aspects of oxidative addition reactions in this system are discussed