Reactivity of Palladium(II) Complexes Containing the Orthometalated C,C-Chelating Ligand C₆H₄-2-PPh₂C(H)COCH₂PPh₃ toward Deprotonating Reagents

The dinuclear complex [Pd(μ-Cl)(C 6 H 4 -2-PPh 2 C(H)COCH 2 PPh 3 )] 2 (ClO 4 ) 2 reacts with Hg(OOCCH 3 ) 2 (1:1 molar ratio, CH 2 Cl 2, room temperature) giving the trinuclear derivative [Pd 2 Hg(μ-Cl) 2 ( C 6 H 4 -2-PPh 2 C (H)CO C (H)PPh 3 ) 2 ](ClO 4 ) 2 ( 1 ). The X-ray structure of 1 has been determined: C 78 H 62 Cl 4 HgO 10 P 4 Pd 2, monoclinic, I 2/ a, a = 20.205(3) Å, b = 11.7529(9) Å, c = 30.905(3) Å, β = 90.333(10)°, V = 7339.0(14) Å 3, Z = 4. The structure shows two Pd atoms bridged by two Cl atoms and also shows weak Pd−Hg contacts. Both orthometalated ylide groups [ C 6 H 4 -2-PPh 2 C (H)CO C (H)(PPh 3 )] - in 1 act as C,C,C-tridentate ligands, coordinated to the palladium center through the arylic carbon atom and the ylidic carbon atom adjacent to the PPh 2 group and to the mercury center through the ylidic carbon atom adjacent to the PPh 3 group. The reaction of [Pd(μ-Cl)(C 6 H 4 -2-PPh 2 C(H)COCH 2 PPh 3 )] 2 (ClO 4 ) 2 with (acac)AuPPh 3 (acac = acetylacetonate; 1:2 molar ratio) affords [Pd( C 6 H 4 -2-PPh 2 C (H)COCH 2 PPh 3 )(acac-O,O‘)](ClO 4 ) ( 2 ) by transmetalation of the acac group. Further treatment of 2 with (acac)AuPPh 3 gives the dinuclear derivative [Pd( C 6 H 4 -2-PPh 2 C (H)CO C H(AuPPh 3 )(PPh 3 ))(acac-O,O‘)](ClO 4 ) ( 3 ) in which the orthometalated ylide fragment acts as a C,C,C-tridentate ligand. The reaction of [Pd(C 6 H 4 -2-PPh 2 C(H)COCH 2 PPh 3 )Cl(PPh 3 )](ClO 4 ) with NBu 4 OH (1:1 molar ratio) affords [Pd( C 6 H 4 -2-PPh 2 C (H)COCH PPh 3 )Cl(PPh 3 )] as a mixture of the cis and trans isomers ( 4a / 4b ), while the reaction of the same cationic precursor [Pd(C 6 H 4 -2-PPh 2 C(H)COCH 2 PPh 3 )Cl(PPh 3 )](ClO 4 ) with (acac)AuPPh 3 results in the formation of [Pd( C 6 H 4 -2-PPh 2 C (H)CO C H(AuPPh 3 )(PPh 3 ))Cl(PPh 3 )](ClO 4 ) ( 5 ). The reaction of [Pd(C 6 H 4 -2-PPh 2 C(H)COCH 2 PPh 3 )(L−L)](ClO 4 ) 2 (L−L = dppe, phen) with Na[N(SiMe 3 ) 2 ] (dppe = 1,2-bis(diphenylphosphino)ethane and phen = 1,10-phenanthroline; 1:1 molar ratio, THF, room temperature) results in the formation of the cationic species [Pd( C 6 H 4 -2-PPh 2 C (H)COCH PPh 3 )(L−L)](ClO 4 ) (L−L = dppe ( 6 ), phen ( 7 )), which contain a free ylidic fragment. Complex 6 reacts with ClAu(tht) (tht = tetrahydrothiophene; 1:1 molar ratio) giving [Pd( C 6 H 4 -2-PPh 2 C (H)CO C H(AuCl)(PPh 3 ))(dppe)](ClO 4 ) ( 8 ), while [Pd(C 6 H 4 -2-PPh 2 C(H)COCH 2 PPh 3 )(phen)](ClO 4 ) 2 reacts with (acac)AuPPh 3 (1:1 molar ratio) affording [Pd( C 6 H 4 -2-PPh 2 C (H)CO C H(AuPPh 3 )(PPh 3 ))(phen)](ClO 4 ) 2 ( 9 ).