2 research outputs found
Mechanism of Chemical and Electrochemical N<sub>2</sub> Splitting by a Rhenium Pincer Complex
A comprehensive
mechanistic study of N<sub>2</sub> activation and
splitting into terminal nitride ligands upon reduction of the rhenium
dichloride complex [ReCl<sub>2</sub>(PNP)] is presented (PNP<sup>–</sup> = N(CH<sub>2</sub>CH<sub>2</sub>P<i>t</i>Bu<sub>2</sub>)<sub>2</sub><sup>–</sup>). Low-temperature studies using
chemical reductants enabled full characterization of the N<sub>2</sub>-bridged intermediate [{(PNP)ClRe}<sub>2</sub>(N<sub>2</sub>)] and
kinetic analysis of the N–N bond scission process. Controlled
potential electrolysis at room temperature also resulted in formation
of the nitride product [Re(N)Cl(PNP)]. This first example of molecular
electrochemical N<sub>2</sub> splitting into nitride complexes enabled
the use of cyclic voltammetry (CV) methods to establish the mechanism
of reductive N<sub>2</sub> activation to form the N<sub>2</sub>-bridged
intermediate. CV data was acquired under Ar and N<sub>2</sub>, and
with varying chloride concentration, rhenium concentration, and N<sub>2</sub> pressure. A series of kinetic models was vetted against the
CV data using digital simulations, leading to the assignment of an
ECCEC mechanism (where “E” is an electrochemical step
and “C” is a chemical step) for N<sub>2</sub> activation
that proceeds via initial reduction to Re<sup>II</sup>, N<sub>2</sub> binding, chloride dissociation, and further reduction to Re<sup>I</sup> before formation of the N<sub>2</sub>-bridged, dinuclear
intermediate by comproportionation with the Re<sup>III</sup> precursor.
Experimental kinetic data for all individual steps could be obtained.
The mechanism is supported by density functional theory computations,
which provide further insight into the electronic structure requirements
for N<sub>2</sub> splitting in the tetragonal frameworks enforced
by rigid pincer ligands
Mechanism of Chemical and Electrochemical N<sub>2</sub> Splitting by a Rhenium Pincer Complex
A comprehensive
mechanistic study of N<sub>2</sub> activation and
splitting into terminal nitride ligands upon reduction of the rhenium
dichloride complex [ReCl<sub>2</sub>(PNP)] is presented (PNP<sup>–</sup> = N(CH<sub>2</sub>CH<sub>2</sub>P<i>t</i>Bu<sub>2</sub>)<sub>2</sub><sup>–</sup>). Low-temperature studies using
chemical reductants enabled full characterization of the N<sub>2</sub>-bridged intermediate [{(PNP)ClRe}<sub>2</sub>(N<sub>2</sub>)] and
kinetic analysis of the N–N bond scission process. Controlled
potential electrolysis at room temperature also resulted in formation
of the nitride product [Re(N)Cl(PNP)]. This first example of molecular
electrochemical N<sub>2</sub> splitting into nitride complexes enabled
the use of cyclic voltammetry (CV) methods to establish the mechanism
of reductive N<sub>2</sub> activation to form the N<sub>2</sub>-bridged
intermediate. CV data was acquired under Ar and N<sub>2</sub>, and
with varying chloride concentration, rhenium concentration, and N<sub>2</sub> pressure. A series of kinetic models was vetted against the
CV data using digital simulations, leading to the assignment of an
ECCEC mechanism (where “E” is an electrochemical step
and “C” is a chemical step) for N<sub>2</sub> activation
that proceeds via initial reduction to Re<sup>II</sup>, N<sub>2</sub> binding, chloride dissociation, and further reduction to Re<sup>I</sup> before formation of the N<sub>2</sub>-bridged, dinuclear
intermediate by comproportionation with the Re<sup>III</sup> precursor.
Experimental kinetic data for all individual steps could be obtained.
The mechanism is supported by density functional theory computations,
which provide further insight into the electronic structure requirements
for N<sub>2</sub> splitting in the tetragonal frameworks enforced
by rigid pincer ligands