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Ammonia, alkyl amines, and aryl amines are found to undergo rapid intermolecular N-H oxidative addition to a planar mononuclear σ(3)-phosphorus compound (1). The pentacoordinate phosphorane products (1·[H][NHR]) are structurally robust, permitting full characterization by multinuclear NMR spectroscopy and single-crystal X-ray diffraction. Isothermal titration calorimetry was employed to quantify the enthalpy of the N-H oxidative addition of n-propylamine to 1 ((n)PrNH2 + 1 → 1·[H][NH(n)Pr], ΔHrxn(298) = -10.6 kcal/mol). The kinetics of n-propylamine N-H oxidative addition were monitored by in situ UV absorption spectroscopy and determination of the rate law showed an unusually large molecularity (ν = k[1][(n)PrNH2](3)). Kinetic experiments conducted over the temperature range of 10-70 °C revealed that the reaction rate decreased with increasing temperature. Activation parameters extracted from an Eyring analysis (ΔH(⧧) = -0.8 ± 0.4 kcal/mol, ΔS(⧧) = -72 ± 2 cal/(mol·K)) indicate that the cleavage of strong N-H bonds by 1 is entropy controlled due to a highly ordered, high molecularity transition state. Density functional calculations indicate that a concerted oxidative addition via a classical three-center transition structure is energetically inaccessible. Rather, a stepwise heterolytic pathway is preferred, proceeding by initial amine-assisted N-H heterolysis upon complexation to the electrophilic phosphorus center followed by rate-controlling N → P proton transfer.

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Studies on the stoichiometric and catalytic reactivity of a geometrically constrained phosphorous triamide 1 with pinacolborane (HBpin) are reported. The addition of HBpin to phosphorous triamide 1 results in cleavage of the B-H bond of pinacolborane through addition across electrophilic phosphorus and nucleophilic N-methylanilide sites in a cooperative fashion. The kinetics of this process of were investigated by NMR spectroscopy, with the determined overall second order empirical rate law given by ν = − k[1][HBpin] where k = 4.76 × 10−5 M−1s−1 at 25 °C. The B–H bond activation process produces a P-hydrido-1,3,2-diazaphospholene intermediate 2, which exhibits hydridic reactivity capable of reacting with imines to give phosphorous triamide intermediates, as confirmed by independent synthesis. These phosphorous triamide intermediates are typically short-lived, evolving with elimination of the N-borylamine product of imine hydroboration with regeneration of the deformed phosphorous triamide 1. The kinetics of this latter process are shown to be first-order, indicative of a unimolecular mechanism. Consequently, catalytic hydroboration of a variety of imine substrates can be realized with 1 as catalyst and HBpin as terminal reagent. A mechanistic proposal implicating a P–N cooperative mechanism for catalysis that incorporates the various independently verified stoichiometric steps is presented and a comparison to related phosphorus-based systems is offered.

Purpose – The purpose of this paper is to investigate the relationship between protean career attitude and perceived internal and external employability, along with the mediating effect of learning-goal orientation. Design/methodology/approach – Data were collected by distributing paper-based questionnaires to 527 workers in private banking sectors in Taiwan. Hierarchical regression analysis was used to examine the results of the relationships. Findings – The results supported the idea that protean career attitude is a significant antecedent of perceived internal and external employability. Protean talents with a higher degree of protean attitude toward value-driven career orientation and self-directed career management have an external employability that is greater than their internal employability. Learning-goal orientation fully mediated the effect of protean career attitude on perceived internal employability, but only partially mediated external employability. Practical implications – The findings can help human resource managers gain a better understanding of the use of an appropriate strategy to influence an employee’s perceived internal and external employability, which can increase the motivation and improve employer-employee relationships that contribute to organizational success and performance. Employees should recognize the increased importance of continuous learning with goal-setting in order to deal with changes at work. Originality/value – This paper empirically establishes the association between protean career attitude and perceived internal and external employability. The protean career concept may provide organizations with a valuable perspective in the evolution of careers. Valuable and protean talents place an emphasis on individuals’ core values, and while learning goals are meant to suit employer organizations, they may also establish opportunities that could cross-organizational boundaries.