PINCER COMPLEXES A SPECIAL TOPIC

Pincer Complexes Complexes of mixed donor polydentate ligands pioneered by Shaw in mid-70s

Generic Structure of Pincer Complex

Dehydrogenation of Alkanes

Palladium Pincer Complexes as Catalysts for the Heck Reaction

Palladium Phosphinito PCP Pincer Complex in Heck Reactions Involving Aryl Chlorides CsOAC, 180 o C, Dioxane

The Classical Mechanism

The Pd(II)/Pd(IV) Mechanism

Platinum NCN and PCP pincer complexes as catalysts for alkane CH bond activation and functionalization

Mechanism for the Shilov system

Preparation of Pincer Complex synthesis of pincer ligand synthesis of metal precursor Metalation of pincer ligand

A solution of resorcinol (0.36 g, 3.28 mmol) and DMAP (0.81 g, 6.60 mmol) in THF (30 ml) was added a solution of ClPPr i 2 (1.0 g, 6.55 mmol) in THF (20 ml), while stirring at 0°C. The resulting mixture was allowed to reach room temperature (r.t.) and stirred for an additional 24 h. Following removal of the solvent in vacuo, the solid residue was extracted with toluene (220 ml). The combined extracts were filtered through a short plug of Celite and the toluene removed in vacuo to yield the product (1.1 g, 95%) as a colorless oil. NMR spectroscopy showed the product to be greater than 98% pure and it was used in further steps without further purification. 1 H NMR ( MHz, CDCl 3 ): d 7.10–6.80 (m, 4H, arom.); 2.00–1.80 (m, 4H, CH(CH 3 ) 2 ); 1.15–1.00 (m, 24H, CH(CH 3 ) 2 ). 13 C NMR ( MHz, CDCl 3 ): d (s, ArC), (s, ArC), (s, ArC), (s, ArC), (d, 1JPC 17.9 Hz, PCH(CH 3 ) 2 ), (s, PCH(CH 3 ) 2 ), (s, PCH(CH 3 ) 2 ). 31 P{ 1 H} NMR ( MHz, CDCl 3 ): d Anal. Calc. for C 18 H 32 O 2 P 2 ( ): C, 63.14; H, Found: C, 63.42; H, 9.74%. Preparation of C 6 H 4 -2,6 -(OPPr i 2 ) 2

DMAP = 4 dimethylaminopyridine

A toluene (50 ml) solution of C 6 H 4 -2,6-(OPPr i 2 ) 2 (500 mg, 1.46 mmol), and PdCl 2 (COD) (417 mg, 1.46 mmol) was refluxed for 5 h. The solvent was evaporated under vacuum and the crude product was extracted with pentane. Following recrystalization from diethyl ether, a purified product was obtained (Yield 630 mg, 90 %). 1 H NMR ( MHz, CDCl 3 ): d 1.20–1.40 (m, 24H, CH(CH 3 ) 2 ), 2.40–2.52 (sep m, 3 JHH7.2 Hz, 4H, CH(CH 3 ) 2 ), 6.54 (d, 3 JHH8.0 Hz, 2H, arom), 6.96 (t, 3 JHH8.0 Hz, 1H, arom); 13 C NMR ( MHz, CDCl 3 ) d (bs, ArC), (s, ArC), (s, ArC), (vt, JPC14.48 Hz, ArC), (vt, JPC23.14 Hz, PCH(CH 3 ) 2 ), (s, PCH(CH 3 ) 2 ), (s, PCH(CH 3 ) 2 ); 31 P NMR ( MHz, CDCl 3 ): d (s, 1P). Anal. Calc. for C 18 H 31 Cl 1 O 2 P 2 Pd (483.24): C, 44.74; H, Found: C, 44.49; H, 6.15%. Preparation PdCl{C6H3 -2,6 -(OPPri2)}

Single-crystal X-ray diffraction study