Synthesis and catalytic properties of cationic palladium(II) and rhodium(I) complexes bearing diphosphinidinecyclobutene ligands

Activation of the C[double bond, length as m-dash]P bond in phosphanylphosphaalkenes (C[double bond, length as m-dash]P-P bond system) in the reaction with nucleophilic reagents: MeLi, nBuLi and tBuLi

Three reactions of phosphanylphosphaalkene (1) with nucleophiles were performed to activate the diphosphorus monomer. We observed similar results in the reactions with MeLi and nBuLi, in which the P-P bond is cleavaged and triphosphorus systems [P(Me)₂-CH(biph)-CH(biph)-P-(PtBu₂)]^- (1a'') and [P(nBu)₂-CH(biph)-CH(biph)-P-(PtBu₂)]^- (1b''), respectively, are formed depending on the nucleophilic reagent (biph = biphenyl). In the case of tBuLi, the P-P bond remains intact; on the phosphorus atom, only one -tBu group is substituted, and as a result, [(biph)(H)C-P(tBu)-PtBu₂]^- (1c) is generated as a stable carbanion. We additionally investigated the effect of substitution in the phenyl ring in the course of these reactions by involving two other phosphanylphosphaalkenes (3 and 4). All initial reactions were conducted in tetrahydrofuran (THF) solution at ambient temperature.

Palladium(II) complexes of 1,10-phenanthroline: Synthesis and X-ray crystal structure determination

Two palladium(II) complexes, [Pd(phen)(N identical withCCH(3))(2)][O(3)SCF(3)](2) (1) and [Pd(phen)(mu-OH)](2)[O(3)SCF(3)](2).2H(2)O (2) (where phen= 1,10-phenanthroline), have been crystallized following the reaction of Pd(phen)Cl(2) with silver triflate, Ag(O(3)SCF(3)), in acetonitrile and water, respectively. The structures of both complexes are based on a Pd(phen)(2+) metal core, with two acetonitrile molecules binding in a monodentate fashion in complex 1 and two hydroxo bridges holding together two cores to form a dimer in complex 2. Additionally, both complexes present a hydrogen bonded 3-D network involving the triflate anions in 1, and water and triflate anions in 2. Both complexes have been characterized by infrared and (1)H NMR spectroscopy and their crystal structures determined by X-ray crystallography.

Catalytic applications of transition-metal complexes bearing diphosphinidenecyclobutenes (DPCB)

The preparation and characterization of sterically protected diphosphinidenecyclobutenes bearing two two-coordinate phosphorus atoms are described from the viewpoint of the development of a novel type of bidentate ligand for transition-metal complexes. They form complexes with group 6 metals such as chromium, molybdenum and tungsten, group 8 metals such as ruthenium, group 10 metals such as palladium and platinum, and group 11 metals such as copper and gold. Some of them can be used as catalysts for synthetic reactions such as cross-coupling of the Sonogashira type, Suzuki-Miyaura coupling, Ullmann coupling, Kosugi-Migita-Stille coupling, cyanation, polymerization of ethylene, dehydrogenative hydrosilylation of ketones, hydroamination of 1,3-butadienes, and direct alkylation or amination of allylic alcohols of Tsuji-Trost reactions.