Novel representatives of 16-membered aminomethylphosphines with alkyl substituents at nitrogen and their gold(I) complexes

Dynamic Covalent Chemistry Approach toward 18-Membered P4N2 Macrocycles and Their Nickel(II) Complexes

“…26 Compound 4 whose NMR spectroscopy data differed from that of macrocycles 1−3 indeed crystallized as the R P S P S P R P isomer of the corresponding 1,10-diaza-3,8,12,17-tetraphosphacyclooctadecane (Figure 3) and adopted a conformation different than macrocycles 1 and 3. Moreover, the conformation of 4 is essentially different from that of the meso-I isomer of 16-membered 1,9-diaza-3,7,11,15-tetraphosphacyclohexadecanes with a zigzag-type propylene chains between the phosphorus atoms 23,24 but is very similar to the conformation of the R P S P S P R P isomer of 14-membered 1,8diaza-3,6,10,13-tetraphosphacyclotetradecane. 28 Both fragments P−CH 2 −N-CH 2 −P and P−CH 2 −CH 2 −CH 2 −CH 2 −P in 4 have twisted conformations, in which all heteroatoms are located in the same plane and all exocyclic substituents are in equatorial positions.…”

“…It indicates the reversibility of P–C and C–N bond formation, interconversion of all components of the dynamic system, and self-correction of the reaction, which characterize the covalent self-assembly of macrocycles according to DCvC principles. In the final reaction mixtures, several intensive signals in the range of −30 to −40 ppm were observed, which are typical for macrocyclic aminomethylphosphines. − The intensity of the signals of byproducts (acyclic aminomethylphosphines or possible 9-membered cycles as products of [1 + 1] cyclocondensation reactions in the range of −24 to −28 ppm) was noticeably lower than that of the macrocyclic product, indicating that the formation of 18-membered macrocycles is more favorable in comparison with other possible products of the condensation reaction.…”

“… Formation of a tetra­phosphonium macrocycle was observed in the tetramerization of 3-(diphenylphosphino)­propanal under acidic conditions . Our previous works clearly demonstrate that the Mannich-like condensation reaction of primary phosphines or secondary bis-phosphines, formaldehyde, and primary or secondary amines and bis-amines can be employed for the selective synthesis of a wide range of macrocyclic aminomethylphosphines, namely [P 2 N 2 ] 2 -cyclophanes, [P 2 N 4 ]-cyclophanes, [P 4 N 2 ]-cryptand, and [P 4 N 2 ]-corands. − Their synthesis, which is accompanied by reversible P–C and C–N bond formation, proceeds with a remarkable stereoselectivity. Thus, in accordance with the main principles of DCvC (reversibility, thermodynamic control, interconversion of molecular components of the dynamic system) in the covalent self-assembly of [P 4 N 2 ]-corands, only one isomer with a preferred configuration of the four endocyclic phosphorus atoms is isolated from the dynamic system containing five possible stereoisomers of [P 4 N 2 ]-corands (Figure ) and [P 2 N]-corands as products of [1 + 1] condensations as well as cyclic and acyclic oligomers…”

“…Thus, the 16- and 20-membered macrocycles (where n = 3 and 5, correspondingly) were always isolated as the meso -I ( R P S P S P R P ) isomers, − but their 14-membered and one 18-membered homologues (where n = 2 and 4, correspondingly) were rac -I R P R P R P R P / S P S P S P S P isomers. ,− Based on these observations, an empirical rule for predicting the configuration of the preferred [P 4 N 2 ] macrocycle on the number of methylene fragments (even or odd) in the initial bis-phosphine was deduced . Unexpectedly, the meso -I isomer of 14-membered P 4 N 2 macrocycles was recently obtained from the reaction mixture of 1,2-bis­(phenylphosphino)­ethane, formaldehyde, and primary amine when a different workup procedure of the reaction mixture was employed, namely crystallization from diethyl ether or ethanol instead of crystallization from DMF .…”

“…The behavior of [P 4 N 2 ]-corands in solutions appears to be more complex than expected due to the lability of the P–CH 2 –N fragment. Thus, the interconversion of isomers for 16-membered P 4 N 2 macrocycles and splitting of 14-membered P 4 N 2 macrocycles into two 7-membered P 2 N macrocycles have been found. − It turned out that many external factors, in particular temperature, solvent, presence of protons or metal ions, influence these processes.…”