Design and synthesis of tris[bis(benzylammonium)aryl]phosphines with bulky meta-substituents

Abstract

Abstract-A novel 3,5,3 0 ,5 0 ,3 00 ,5 00 -hexakis(dimethylamino)methyl substituted triphenylphosphine analogue has been prepared. The six amine functionalities of the corresponding phosphine oxide and sulfide were alkylated quantitatively with methyl iodide and benzyl bromide, as well as with G1 and G2 Fréchet dendrons to afford the respective hexa-ammonium triarylphosphine oxides and sulfides. The phosphine sulfide derivatives were deprotected with P(n-Bu) 3 to afford a series of hexa-ammonium triarylphosphines that range from small molecules to first and second generation dendrimers (MW up to 5451.44). Upon formation of the hexa-ammonium salt a clear shift in 31 P NMR is observed, indicative for opening of the C -P-C angle of the triaryl phosphine. Calculations on the hexacationic phosphines show an increased barrier of rotation around the P-C(aryl) bond with increasing size of the N-substituents. The calculated structure of the G2-dendron alkylated hexa-ammonium triarylphosphine shows that this dendritic phosphine has a disc-like rather than a cone-like structure, with an estimated cone angle of approximately 1808 q

Synthesis, coordination chemistry, and metal complex reactivity of (dimethylamino)methyl-substituted triarylphosphanes; X-ray study on [AuCl(PPh3−nArn)] (Ar=1-C6H3(CH2NMe2)2-3,5, n=1, 3; Ar=1-C6H4(CH2NMe2)-4, n=3)

“…The solid state structure of complex 8, which is almost identical to that of the corresponding PPh 3 complex, supports this observation. Interestingly, this exclusive formation of a cis-platinum dichloride complex in the case of 6 is in contrast with the findings for its previously reported hexa-ammonium salts (Dendriphos) [8], for which increased bulk and, presumably, larger cone angles lead to the exclusive formation of the trans-platinum dichloride complexes [14]. The similarity of 8 and [AuCl(PPh 3 )] in the solid state is in line with the observations of Dunitz, who discussed the structure of triphenylmethane and triphenylphosphane stereoisomers in the solid state [15].…”

“…Using a previously described protocol [8], mono{3,5-bis[(dimethylamino)methyl]phenyl}-diphenylphosphane (2, PPh 2 -(NC(H)N)) and tris{3,5-bis[(dimethylamino)-methyl]phenyl}phosphane (4, P(NC(H)N) 3 ) were prepared. The procedure started from 1-bromo-3,5-bis[(dimethylamino)methyl]benzene (1, Br-(NC(H)N)) [9], which was converted into the respective phosphanes 2 and 4 via lithium-bromide exchange followed by reaction with chlorodiphenylphosphane or phosphorus tribromide (Scheme 1).…”

Fast Suzuki–Miyaura Cross‐Coupling Reaction with Hexacationic Triarylphosphine Bn‐Dendriphos as Ligand

“…The results for 1 and 2 are in line with the molecular modelling and coordination experiments on these ligands, reported elsewhere. [1,16] Based on these studies we predicted enlarged cone angles and a bulky behaviour for 2. We (1) at 0.01 mol % Pd loading using Bn-Dendriphos.…”

“…[1] These novel ligands combine a triarylphosphine core with a shell of six ammonium groups. The latter feature makes this series of dendritic ligands very versatile, as it enables them to act as phase-transfer agents and opens the way for catalyst recovery by means of a biphasic work-up or via nanofiltration.…”

“…Both NMR and molecular modelling experiments suggested the use of these hexacationic phosphines as bulky ligands. [1] At the same time, based on the solubility range of these ligands, applications in both H 2 O and MeOH, as well as in organic solvents, can be envisioned.…”