Selective Dehydrocoupling of Phosphines by Triamidoamine Zirconium Catalysts

Abstract

New zirconium triamidoamine complexes (N3N)ZrR (N3N = N(CH2CH2NSiMe3)3 3-; R = Me, 1; PHPh, 2; PHCy, 4) are effective catalysts for the dehydrocoupling of primary and secondary phosphines and select for the diphosphine product. Mechanistic analysis revealed that metal-catalyzed P−P bond formation occurs via σ-bond metathesis steps.

Zirconium-Catalyzed Alkene Hydrophosphination and Dehydrocoupling with an Air-Stable, Fluorescent Primary Phosphine

“…Diphosphines of the type (RPH)2, like 5, are known in some instances to thermally degrade to primary phosphines RPH2 and This diphosphine displays resonances in the 31 P NMR spectrum at δ = −70.8 and −71.3 corresponding to rac and meso isomers of the diphosphine product, similar to known compounds of this type [3]. The P-H protons of 5 resonate at δ = 3.89 (J PH = 199 Hz), which is similar to other aryl-substituted secondary diphosphines (e.g., (p-TolPH) 2 , δ = 3.99 (J PH = 198 Hz)) [8]. Diphosphines of the type (RPH) 2 , like 5, are known in some instances to thermally degrade to primary phosphines RPH 2 and phosphacycles [23,24], but such products were not observed under these conditions.…”

“…The P-H protons of 5 resonate at δ = 3.89 (JPH = 199 Hz), which is similar to other arylsubstituted secondary diphosphines (e.g., (p-TolPH)2, δ = 3.99 (JPH = 198 Hz) [8]. Diphosphines of the type (RPH)2, like 5, are known in some instances to thermally degrade to primary phosphines RPH2 and This diphosphine displays resonances in the 31 P NMR spectrum at δ = −70.8 and −71.3 corresponding to rac and meso isomers of the diphosphine product, similar to known compounds of this type [3].…”

“…The P-H protons of 5 resonate at δ = 3.89 (JPH = 199 Hz), which is similar to other arylsubstituted secondary diphosphines (e.g., (p-TolPH)2, δ = 3.99 (JPH = 198 Hz) [8]. Diphosphines of the type (RPH)2, like 5, are known in some instances to thermally degrade to primary phosphines RPH2 and Scheme 2.…”

“…The phosphido proton resonates at δ = 4.08 (J PH = 211 Hz) in the 1 H NMR spectrum, confirming a secondary phosphine. This complex is highly related to a class of zirconium phosphido complexes formed by insertion of a primary phosphine into 1 [5,6,8,25,26] (Figure S9). …”

“…The goal of P-E bond formation in a selective, atom-economical, and efficient manner has motivated efforts in two principal catalytic approaches: hydrophosphination to make P-C bonds [2] and dehydrocoupling to make P-P bonds [3]. Pursuant to both approaches, we have demonstrated hydrophosphination [4][5][6] and dehydrocoupling [7][8][9] of primary phosphine substrates with [κ 5 -N,N,N,N,C-(Me 3 SiNCH 2 CH 2 ) 2 NCH 2 CH 2 NSiMe 2 CH]Zr (1) [8] (Scheme 1) where phosphide compounds (i.e., (N 3 N)ZrPHR; N 3 N = N(CH 2 CH 2 NSiMe 3 ) 3 3− ) are key intermediates.…”