Neutral and Cationic Palladium(II) Bis(pyrazolyl)methane Complexes

The synthesis, structures, and reactivity of neutral and cationic Pd(II) complexes incorporating bis(pyrazolyl)methane ligands are described. The reaction of (CH 3 CN) 2 PdCl 2 with the appropriate bis(pyrazoyl)methane in CH 2 Cl 2 yields {Ph 2 C(3- t Bu-pz) 2 }PdCl 2 ( 1 ) and {Ph 2 C(pz) 2 }PdCl 2 ( 2 ). Steric crowding associated with the t Bu groups of 1 increases the puckering of the chelate ring (boat conformation) and retards the chelate ring inversion relative to 2 . The reaction of {Me 2 C(pz) 2 }PdMe 2 ( 3 ) with [HNMe 2 Ph][B(C 6 F 5 ) 4 ] yields {Me 2 C(pz) 2 }PdMe(NMe 2 Ph) + ( 4a, B(C 6 F 5 ) 4 - salt), while treatment of 3 with [H(OEt 2 ) 2 ][B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ] yields {Me 2 C(pz) 2 }PdMe(OEt 2 ) + ( 4b, B{3,5-(CF 3 ) 2 C 6 H 3 } 4 - salt). Complex 4a reacts with ethylene at −60 °C (CD 2 Cl 2 ) to yield {Me 2 C(pz) 2 }PdMe(CH 2 CH 2 ) + ( 5, B(C 6 F 5 ) 4 - salt) and free NMe 2 Ph. Cation 5 undergoes ethylene insertion at −10 °C and oligomerizes ethylene (1 atm) to predominantly linear internal C 8 to C 24 olefins (ca. 0.1 branches per 2 carbons) at 23 °C.