title: A neutral tetraphosphacyclobutadiene ligand in cobalt(I) complexes.
abstract: The unusual reactivity of the newly synthesized β-diketiminato cobalt(I) complexes, [(L(Dep)Co)2] (2 a, L(Dep)=CH[C(Me)N(2,6-Et2C6H3)]2) and [L(Dipp)Co⋅toluene] (2 b, L(Dipp)=CH[CHN(2,6-(i)Pr2C6H3)]2), toward white phosphorus was investigated, affording the first cobalt(I) complexes [(L(Dep)Co)2(μ2:η(4),η(4)-P4)] (3 a) and [(L(Dipp)Co)2(μ2:η(4),η(4)-P4)] (3 b) bearing the neutral cyclo-P4 ligand with a rectangular-planar structure. The redox chemistry of 3 a and 3 b was studied by cyclic voltammetry and their chemical reduction with one molar equivalent of potassium graphite led to the isolation of [(L(Dep)Co)2(μ2:η(4),η(4)-P4)][K(dme)4] (4 a) and [(L(Dipp)Co)2(μ2:η(4),η(4)-P4)][K(dme)4] (4 b). Unexpectedly, the monoanionic Co2P4 core in 4 a and 4 b, respectively, contains the two-electron-reduced cyclo-P4(2-) ligand with a square-planar structure and mixed-valent cobalt(I,II) sites. The electronic structures of 3 a, 3 b, 4 a, and 4 b were elucidated by NMR and EPR spectroscopy as well as magnetic measurements and are in agreement with results of broken-symmetry DFT calculations.
authors.affiliation: Technische Universität Berlin, Institute of Chemistry: Metalorganics and Inorganic Materials, Sekr. C2, Strasse des 17. Juni 135, 10623 Berlin (Germany) http://www.driess.tu-berlin.de.
authors.forename: Shenglai
authors.initials: S
authors.lastname: Yao
authors.forename: Nils
authors.initials: N
authors.lastname: Lindenmaier
authors.forename: Yun
authors.initials: Y
authors.lastname: Xiong
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Inoue
authors.forename: Tibor
authors.initials: T
authors.lastname: Szilvási
authors.forename: Mario
authors.initials: M
authors.lastname: Adelhardt
authors.forename: Jörg
authors.initials: J
authors.lastname: Sutter
authors.forename: Karsten
authors.initials: K
authors.lastname: Meyer
authors.forename: Matthias
authors.initials: M
authors.lastname: Driess
keywords: bond activation; cobalt; phosphorus; β-diketiminates