tBuP(NH₂)₂—A Reactive Synthon for the Synthesis of Molecular Imidophosphinates of Group 13 Metals

Abstract

Reactions of tBuP(NH(2))(2) with Group 13 trialkyls MR(3) (M=Al, Ga, In; R=Me, tBu) were investigated in detail. According to variable-temperature (VT) NMR investigations, the reaction proceeds stepwise with the initial formation of aminophosphane adducts, which subsequently react to give iminophosphorane adducts and finally the heterocyclic metallonitridophosphinates. BP86/TZVPP (DFT) calculations were performed to verify this reaction pathway, to elucidate the influence of the central Group 13 element on the stability of the reaction intermediates and the heterocycles, as well as to assess the thermodynamics of their formation. The relative stability of free and complexed aminophosphane RP(NH(2))(2) and iminophosphorane R(H(2)N)(H)P=NH (adducts) with P(III) and P(V) centers was studied in more detail with DFT and MP2 methods. In addition, the influence of the substituent R was investigated by variation of R from H to Me, tBu, F, and NH(2). In general, the aminophosphane form was found to be favored for the free ligand, however, upon complexation with MR(3) (M=Al, Ga; R=alkyl) both forms are almost equal in energy.

Reactivity of Bis(organoamino)phosphanes with Aluminum(III) Compounds: Straightforward Access to Diiminophosphinates by Means of Hydrogen‐Atom Migration – An Experimental and Theoretical Study

“…The 31 P NMR spectrum of the reaction mixture after 2 h revealed a new signal at δ = 41.0 ppm ( 1 J P,H = 502.8 Hz) (this signal is observed as a singlet in the corresponding 31 P{ 1 H} NMR spectrum), which indicated the presence of an intermediate 2c that already contained the P H functionality together with the signal of the final product 3c . The observation of this intermediate is reminiscent of the study reported by Schulz et al (Scheme ),7 in which the presence of an analogous intermediate (Scheme , A ) was suggested. This intermediate then smoothly transformed into the final product 3c within the ensuing 24 hours.…”

“…5 kcal mol –1 ), although the stability order and trends are the same. In addition, the calculations on neutral phosphanes were also performed with the BP86‐D functional,26 previously used by Schulz et al7…”

“…Thus, as early as 1981 Cowley et al observed an interesting reaction between the compound (Me 3 Si) 2 NP(=NSiMe 3 ) that contained two coordinated phosphorus atoms and Me 3 Al to yield diiminophosphinate {(Me)(Me 3 Si)P[N(SiMe 3 )] 2 }AlMe 2 by means of double‐group migration and concomitant cyclization, which gave a central PN 2 Al core 6. Later on, Schulz and Krossing et al reported the reaction between t BuP(NH 2 ) 2 and AlMe 3 that gave compound {[( t Bu)(H)P(NH) 2 ]AlMe 2 } 2 as a result of the hydrogen‐atom migration according to Scheme 7. This compound formally represents a dimer of N , P , N ‐chelated compound [( t Bu)(H)P(NH) 2 ]AlMe 2 (Scheme ).…”

“…This compound formally represents a dimer of N , P , N ‐chelated compound [( t Bu)(H)P(NH) 2 ]AlMe 2 (Scheme ). Such hydrogen‐atom migration between NH from t BuP(NH 2 ) 2 and PH from t Bu(H)P(=NH)(NH 2 ) was also studied from the theoretical point of view to prove that the N(H) form is more stable 7. Nevertheless, it is evident from Scheme that this situation can change dramatically upon coordination of the metallic fragment and/or when the N,P,N backbone becomes negatively charged.…”

6 Nitrogen, phosphorus, arsenic, antimony and bismuth

“…The reaction of PBu t (NH 2 ) 2 towards reagents containing group 13 alkyls has also been reported and shows initial adduct formation followed by alkane elimination: heterocyclic products are ultimately obtained. 112 Remarkably, exposure of solutions containing Li 3 [P(NBu t ) 3 (N(SiMe 3 )] and LiOBu t to atmospheric oxygen gives the stable radical dianion {(Me 3 SiN)P(m 3 -NBu t ) 3 [m 3 -Li(THF) 3 ](OBu t )}. In a remarkable reaction, Wright and co-workers have shown that reaction of PhPHLi with MeAlCl 2 in a 3:1 ratio results in the formation of [{PhP(H)-PPh}Li?THF] 4 : the solid-state structure of this compound shows that it has D 2 symmetry.…”