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CATALYZED STANNOLE SYNTHESIS; X-RAY STRUCTURE; OXIDATIVE-ADDITION; STEREOCHEMICAL NONRIGIDITY; HYDROSILYLATION CATALYST; NICKEL(0) COMPLEXES; ALLYLIC ALCOHOLS; ARYL HALIDES; PHOSPHINE; ALKYNES
Abstract:
The complexes (cod)MCl2 (M = Pd, Pt; cod = cis,cis-1,5-cyclooctadiene) react with Li2(cot) (cot = cyclooctatetraene) in a 1,6-diene/diethyl ether mixture (1,6-diene = hepta-1,6-diene, diallyl ether, dvds (1,3-divinyl-1,1,3,3-tetramethyldisiloxane)) to afford the isolated homoleptic dinuclear Pd0 and Pt0 compounds Pd2(C7H12)3 (1), Pd2(C6H10O)3·C6H10O (2‘; 2: Pd2(C6H10O)3), Pd2(dvds)3 (3), and Pt2(C7H12)3 (4). When 1−4 are treated with additional 1,6-diene the equally homoleptic but mononuclear derivatives of type M(1,6-diene)2 (5−8) and with ethene the mixed alkene complexes (C2H4)M(1,6-diene) (9−12) are obtained in solution. Complexes 1−12 react with donor ligands such as phosphanes, phosphites, or tBuNC to give isolated complexes of types L−M(1,6-diene) (13−41), which have also been prepared by other routes. In all complexes the metal centers are TP-3 coordinated: complexes 1−4 contain chelating and bridging 1,6-diene ligands, whereas the other complexes contain a chelating 1,6-diene ligand and an η2-alkene (5−12) or η1-donor ligand (13−41). Of the studied 1,6-diene complexes the hepta-1,6-diene derivatives are most reactive, while the diallyl ether complexes are often more convenient to handle. The readily isolable dinuclear hepta-1,6-diene and diallyl ether complexes 1, 2‘, and 4, and their mononuclear pure olefin derivatives are among the most reactive sources for naked Pd0 and Pt0. The corresponding L−M(1,6-diene) complexes are equally reactive precursor compounds for the generation of [L−M0] fragments in solution, which for M = Pd are available otherwise only with difficulty. The results are significant for the operation of naked Pd0 and L−Pd0 catalysts in homogeneous catalysis.
