Thermodynamic, Kinetic, and Computational Study of Heavier Chalcogen (S, Se, and Te) Terminal Multiple Bonds to Molybdenum, Carbon, and Phosphorus

Abstract

Enthalpies of chalcogen atom transfer to Mo(N[t-Bu]Ar)3, where Ar = 3,5-C6H3Me2, and to IPr (defined as bis-(2,6-isopropylphenyl)imidazol-2-ylidene) have been measured by solution calorimetry leading to bond energy estimates (kcal/mol) for EMo(N[t-Bu]Ar)3 (E = S, 115; Se, 87; Te, 64) and EIPr (E = S, 102; Se, 77; Te, 53). The enthalpy of S-atom transfer to PMo(N[ t-Bu]Ar) 3 generating SPMo(N[t-Bu]Ar)3 has been measured, yielding a value of only 78 kcal/mol. The kinetics of combination of Mo(N[t-Bu]Ar)3 with SMo(N[t-Bu]Ar)3 yielding (mu-S)[Mo(N[t-Bu]Ar)3]2 have been studied, and yield activation parameters Delta H (double dagger) = 4.7 +/- 1 kcal/mol and Delta S (double dagger) = -33 +/- 5 eu. Equilibrium studies for the same reaction yielded thermochemical parameters Delta H degrees = -18.6 +/- 3.2 kcal/mol and Delta S degrees = -56.2 +/- 10.5 eu. The large negative entropy of formation of (mu-S)[Mo(N[t-Bu]Ar)3]2 is interpreted in terms of the crowded molecular structure of this complex as revealed by X-ray crystallography. The crystal structure of Te-atom transfer agent TePCy3 is also reported. Quantum chemical calculations were used to make bond energy predictions as well as to probe terminal chalcogen bonding in terms of an energy partitioning analysis.

Molecular Control of the Nanoscale: Effect of Phosphine–Chalcogenide Reactivity on CdS–CdSe Nanocrystal Composition and Morphology

“…These values roughly agree with previous results, which gave PdS and PdSe bond strengths of 96 and 75 kcal/mol, respectively. 44 The ΔE°d ifference between two phosphineÀchalcogenides at the end of the series, TPPE and HPTE, is ∼13 kcal/mol for S and ∼14 kcal/mol for Se (solvation increases this difference to ∼23 kcal/mol for S and ∼16 kcal/mol for Se; see Supporting Information). Both ÀΔG°and ÀΔE°c alculations clearly show phosphineÀchalcogenide stability relative to the release of free phosphine and chalcogen increases in the order TPPE ∼ DPPE < TBPE < TOPE < HPTE.…”

“…44 PhosphineÀchalcogenide (R 3 PdSe, R 3 PdS) 31 P NMR chemical shifts (δ) are more "downfield" (higher δ) compared to parent phosphines (R 3 P), indicating that 77 Se NMR spectra of phosphine (R 3 P) and phosphineÀchalcogenide (R 3 PE) precursors (E = S, Se). J( 31 PÀ 77 Se) coupling (330À520 Hz) is observed for R 3 PSe by both 31 P and 77 Se NMR.…”

Pyridine, thiophosphine, and selenophosphine complexes of the phenylphosphine dication

“…ppm) [9] or the free ligand (SPCy 3 δ = 62.4 ppm). [10] The 19 F chemical NMR shift for the triflate anions is between -78.8 and 79.2 ppm and indicates free triflate in solution with weak to no interaction with the phosphorus dication. As shown in Figure 1, each of the solid state structures contains a PhP unit in which the phosphorus centre is attached to two nitrogen, sulfur or selenium atoms.…”

Phosphine chalcogenide complexes of antimony(III) halides

“…SPCy 3 was prepared via the method of Hoff and co-workers. 22 MeCN and CH 2 Cl 2 were dried initially via distillation from CaH 2 , and subsequently stored over 3 or 4 Å molecular sieves. All other solvents were collected from a Grubbs-type solvent purification system, 23 and stored over 4 Å molecular sieves.…”