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

• Published in: Organometallics 1999-11, Vol.18 (23), p.4758-4764
• Main Authors: Tsuji, Shoei, Swenson, Dale C, Jordan, Richard F
• Format: Article
• Language: English
• Subjects: 40 CHEMISTRY; CHEMICAL PREPARATION; CONFIGURATION INTERACTION; LIGANDS; PALLADIUM COMPLEXES; PYRAZOLES
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om990508e

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.