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

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journal contribution
posted on 1999-10-03, 00:00 authored by Shoei Tsuji, Dale C. Swenson, Richard F. Jordan
The synthesis, structures, and reactivity of neutral and cationic Pd(II) complexes incorporating bis(pyrazolyl)methane ligands are described. The reaction of (CH3CN)2PdCl2 with the appropriate bis(pyrazoyl)methane in CH2Cl2 yields {Ph2C(3-tBu-pz)2}PdCl2 (1) and {Ph2C(pz)2}PdCl2 (2). Steric crowding associated with the tBu groups of 1 increases the puckering of the chelate ring (boat conformation) and retards the chelate ring inversion relative to 2. The reaction of {Me2C(pz)2}PdMe2 (3) with [HNMe2Ph][B(C6F5)4] yields {Me2C(pz)2}PdMe(NMe2Ph)+ (4a, B(C6F5)4- salt), while treatment of 3 with [H(OEt2)2][B{3,5-(CF3)2C6H3}4] yields {Me2C(pz)2}PdMe(OEt2)+ (4b, B{3,5-(CF3)2C6H3}4- salt). Complex 4a reacts with ethylene at −60 °C (CD2Cl2) to yield {Me2C(pz)2}PdMe(CH2CH2)+ (5, B(C6F5)4- salt) and free NMe2Ph. Cation 5 undergoes ethylene insertion at −10 °C and oligomerizes ethylene (1 atm) to predominantly linear internal C8 to C24 olefins (ca. 0.1 branches per 2 carbons) at 23 °C.