Molybdenum dinitrogen complexes supported by a silicon-centred tripod ligand and dppm or dmpm: tuning the activation of N₂

Abstract

Two molybdenum dinitrogen complexes with a novel pentaphosphine environment have been synthesised and structurally characterised. A combination of the tripodal alkylphosphine ligand tris(dimethylphosphinomethyl)methylsilane (SiP3) and the coligands dppm/dmpm has been employed to tune the activation of the N2 ligand.

Group 6 Transition‐Metal/Boron Frustrated Lewis Pair Templates Activate N2and Allow its Facile Borylation and Silylation

“…Indeed, Lewis pairs between 2 and one dinitrogen ligand in complexes 1 were formed. Although some pb lock Lewis acid adducts of metal-ligated dinitrogen are known, very few have been structurally characterized, [13,21] and their reactivity was generally not explored. [ ]a nd long N À Nd istances [1.196(5) for 3 Mo and 1.212(6) for 3 W vs.1.096 for free N 2 and 1.10(2) for 1 Mo ]s upport aM =N=Nd epiction, [16] as ar esult of enhanced metal-to-N 2 back bonding.T he BÀNb onds are 1.567(7) (3 Mo )a nd 1.570(6) (3 W )a nd fall within the range of B À N bond lengths typical of classical adducts of 2 with nitrogen bases.…”

Beyond Triphos – New hinges for a classical chelating ligand

“…Recently however, several molybdenum complexes have been investigated for the activation of molecular nitrogen [44,45].…”

“…Ligands 82, 89 and 90 were coordinated to molybdenum(III) and subsequently studied for molecular nitrogen activation [44,45]. In general, the tripodal MeSiP 2 Me P R ligands were complexed with [MoCl 3 (THF) 3 ] forming [MoCl 3 (κ 3 -PhBP 2 Me P R )] (92-94), and then subsequently reduced using a Na x Hg amalgam in the presence of a secondary bidentate phosphine ligand (95-100, Scheme 17).…”

Molybdenum(0)‐N2 Complexes Supported by the Tripod Ligand 1,1,1‐Tris(Diphenyl‐Phosphinomethyl)Ethane: Steric Influence on the Coordination of Mono‐ and Diphosphine Coligands

“…[16] Eventually, we were able to tune the activation of the N 2 ligand by consecutively interchanging aryland alkylphosphines in the tripod ligand. [14][15][16][17] In order to de-spectroscopy. The influence of the ligand tdppme on the coordination of PMe 3 , PMe 2 Ph, PMePh 2 , PPh 3 and dcpm (bis(dicyclohexylphosphine) is investigated and compared to earlier results involving dppm and dmpm as co-ligands.…”

“…[10][11][12] Moreover, we have explored the use of multidentate phosphine ligands to address mechanistic problems of the Chatt cycle. [10,[13][14][15] Recently we reported the synthesis of the first molybdenum dinitrogen complexes facially coordinated by the tripodal ligand 1,1,1-tris(diphenylphosphinomethyl)ethane (tdppme), [Mo(N 2 )(tdppme)(dmpm)] and [Mo(N 2 )(tdppme)(dppm)] (dppm = bis(diphenylphosphanyl)methane, dmpm = bis(dimethylphosphanyl)methane), by sodium amalgam reduction of [MoBr 3 (tdppme)] under N 2 in the presence of dmpm and dppm, respectively. Importantly, protonation of [Mo(N 2 ) (tdppme)(dmpm)] with triflic acid led to the NNH 2 complex [Mo(NNH 2 )(tdppme)(dmpm)](OTf) 2 with retention of the pentaphosphine coordination, thus principally demonstrating the capability of such systems to serve as catalysts in a nitrogen-fixing cycle.…”