Attempts To Prepare Palladium(II) Complexes with the O,C,O Pincer Aryl Ligand C₆(NO₂)₂-2,6-(OMe)₃-3,4,5

The complex [HgR 2 ] (R = C 6 (NO 2 ) 2 -2,6-(OMe) 3 -3,4,5-C 1 ( 2 )), obtained by thermal decomposition of [Hg(O 2 CR) 2 ] ( 1 ), reacts with Q 2 [Pd 2 Cl 4 (μ-Cl) 2 ] to give [Hg(R)Cl] ( 3 ) and Q 2 [Pd(R)Cl(μ-Cl)] 2 (Q = (PhCH 2 )Ph 3 P ( 4a ), Me 4 N ( 4b )), which react (i) with Tl(acac) (1:2, acac = acetylacetonate) to give Q[Pd(R)Cl(O,O-acac)] (Q = (PhCH 2 )Ph 3 P ( 5a ), Me 4 N ( 5b )) or (ii) with AgClO 4 (1:2) to give [Pd(κ 3 -R)Cl] (κ 3 -R = κ 3 -C 6 (NO 2 ) 2 -2,6-(OMe) 3 -3,4,5-C 1,O,O‘ ( 6 )), which can also be obtained by reacting 5a with HBF 4 . Complex 6 reacts with p -toluidine (1:1, L) to give [Pd(R)(μ-Cl)L] 2 ( 7 ). Complex 5b decomposes in a mixture of acetone/water to give [Pd(κ 2 -R)(O,O-acac)] (κ 2 -R = κ 2 -C 6 (NO 2 ) 2 -2,6-(OMe) 3 -3,4,5-C 1,O ( 8 )), which reacts (i) with neutral monodentate ligands to give [Pd(R)(O,O-acac)L] (L = PPh 3 ( 9 ), pyridine (py) ( 10 ), tetrahydrothiophene ( 11 )), (ii) with bis(diphenylphosphino)methane (dppm) to give a complex that readily oxidizes to give [Pd(R)(O,O-acac)(dppmO)] (dppmO = monoxide of bis(diphenylphosphino)methane ( 12 )), (iii) with 1,10-phenanthroline (phen) to give [Pd(R)(C-acac)(phen)] ( 13 ), and (iv) with protonated ligands (HL)ClO 4 to give 10 (L = py) or cis -[Pd(R)(H 2 O) 2 (PPh 3 )]·H 2 O (L = PPh 3 ( 14 )). Trifluoromethanesulfonic acid (HOSO 2 CF 3 ) reacts with 9 and PPh 3 or with 13 to give trans -[Pd(R)(OSO 2 CF 3 )(PPh 3 ) 2 ] ( 15 ) or [Pd(R)(OSO 2 CF 3 )(phen)] ( 16 ), respectively. The X-ray crystal structures of 7·2CH 2 Cl 2, 8, 10, and 14·H 2 O have been determined.