Beyond Triphos – New hinges for a classical chelating ligand

Abstract

Branched triphosphine ligands have been less widely studied than mono-and bidentate analogues. The most studied ligand of this type is Triphos Ph (CH 3 C(CH 2 PPh 2 ) 3 ). Substitution of the apical C-CH 3 moiety with boron, silicon, tin, nitrogen or phosphorus fragments has generated a new family of ligands, in some cases displaying varying coordination chemistry and reactivity to the parent carbonbased system. This review includes the synthetic strategies implemented to afford these ligands, as well as derivatives by way of varying the phosphine substituents. Although not exhaustive, relevant types of reported complexes featuring these ligands are discussed, as well as their reactivity and catalytic applications. Through critical analysis, common themes and chemical trends across this family of apical heteroatomic, branched triphosphines can be identified, leading to improvements in current chemical applications, as well as new areas that remain underdeveloped.

Cobalt(-i) triphos dinitrogen complexes: activation and silyl-functionalisation of N2

“…Our group has been investigating the N-triphos ligand motif ({N(CH2PR2)3}), [9][10][11][12][13] and recently, we reported a Mo/N-triphos N2 complex. This complex showed moderate N2 activation that was comparable to the C-triphos analogue, but with a varied reactivity profile.…”

“…13 Of the many triphos derivatives, N-triphos is advantageous (particularly over the similar C-triphos system), due to the ease of synthetic tunability of the steric and electronic ligand parameters, and the accessible lone pair on the apical nitrogen provides an additional reactive site. 11,12 We sought to investigate the relatively unexplored potential of cobalt for N2 activation using the neutral N-triphos (N(CH2PPh2)3 or NP3 Ph ) and C-triphos ({MeC(CH2PPh2)3} or MeCP3 Ph ) scaffolds.…”

Carbon/Silicon Exchange at the Apex of Diphos‐ and Triphos‐Derived Ligands – More Than Just a Substitute?

“…[27] Recent investigations showed the high potential of this ligand platform to act as a superior support in metal-catalyzed reactions of various substrates. [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] However, the concept of C/Si switch to alter the catalytic properties or the reactivity of the metal complexes was never comparatively reported for such catalytic transformations. While the stability of the Si species is indeed crucial, it will be interesting to see whether an influence of C/Si exchange can be observed for other systems.…”

“…Such changes are typically observed for Triphos and its Si‐derived counterpart Triphos Si for metals that have high‐spin and low‐spin states with only low energy barriers between the two states . Recent investigations showed the high potential of this ligand platform to act as a superior support in metal‐catalyzed reactions of various substrates . However, the concept of C/Si switch to alter the catalytic properties or the reactivity of the metal complexes was never comparatively reported for such catalytic transformations.…”

Valorisation of plastic waste via metal-catalysed depolymerisation

“…Interestingly, PET flakes from postconsumer bottles could be used, showing the catalytic system to be resistant to the presence of contaminants and impurities (e.g., additives, pigments) [ 188 ]. More recently, effective PET depolymerisation was accomplished by a ruthenium molecular catalysts bearing the well-known tripodal phosphorous ligand 1,1,1-tri(diphenylphosphinomethyl)ethane (triphos) [ 189 – 190 ]. Thus, use of Ru(triphos)tmm (tmm = trimethylenemethane) and acidic bis(trifluoromethane)sulfonimide (HNTf 2 ) cocatalyst (1:1) in noxious 1,4-dioxane solvent resulted in 41% PET conversion and 64% BDM selectivity at 140 °C and 100 bar H 2 due to the formation of ether byproducts ( Table 1 , entry 3) [ 191 ].…”