Cyclopalladated o-carboranes. Palladium transfer from cyclopalladated N,N-dimethylbenzylamines, 1C-diphenylphosphino-o-carborane and η3-allyls in carboxylic acid solvents

Reactions of benzyldiphenylphosphine with Pd(II) sources on silica gel

“…Compound 1 was stable on the 100e230 and 230e400 mesh SiO 2 at 120 C for at least 5 h. Complex 3 did not change its structure at 85 C for at least 5 h. Compound 4 was stable at 50 C for at least 24 h. The same authors converted complex 2 to the m-Br analog of 1 in 86% using HgBr 2 [12]. Ryabov et al reported preparation of 1 in 21% yield using the transmetalation reaction between PBnPh 2 and the cyclopalladated complex [(m-Cl)PdL 2 ] 2 (HL 2 ¼ N,N-dimethylbenzylamine) in CHCl 3 eAcOH at rt [11]. Applying different conditions (PhMeeCF 3 CO 2 H, reflux) to the same reaction, Pfeffer's group increased the yield of the crude complex 1 to 90% [10].…”

“…Method 1 (preparation in solvent) [11]. In a glove box, PBnPh 2 (0.2300 g, 0.8324 mmol) was placed into an Ar-filled 50-mL Schlenk flask, then di-(m-chloro)bis-{[2-(N,N-dimethylamino)methyl]phenyl-C,N}dipalladium(II) (0.2138 g, 0.3872 mmol) was added followed by abs.…”

The Exchange of Cyclometalated Ligands

“…A prelude to the synthesis of a variety of cyclopalladated o-carboranes via the ligand exchange was the preparation of 4-1 (Figure 2) reacting N-donor palladacycle 3-1 with benzyldiphenylphosphine PhCH 2 PPh 2 [26]. Though the isolated yield was low (21%), it was still higher than that achieved by metalation of PhCH 2 PPh 2 by Pd II acetate [27].…”

“…Th B3/B4 ratio is sterically determined by the nature of R (100% for B4 in the case of 4-3c (R i Pr). Palladium(II) has been successfully transferred via the ligand exchange from dimeric chloro-bridged N-donor palladacycles 3-1 and both enantiomers of 3-4 (R = Me) at several Pand As-donor ligands 4-2-4-4 ( Figure 3) derived from the parent o-carborane C 2 B 10 H 12 [26]. Dimers 4-5 are effortlessly prepared in high yields.…”

“…26, x 17 of 31 the presence of AgNO3 in a CH2Cl2/MeOH mixture. Silver(I) abstracts chloro ligands and activates Pt II with respect to C−H bonds of incoming N-donor ligands.…”