Noninnocent behavior of bidentate amidophosphido [NP]2- ligands upon coordination to copper

Gradual Coordination and Reversible P-P Bond Activation of a P3 -Unit with Transition Metal Carbonyls

Coordination of a stereochemically defined P3 -chain to a series of transition metal carbonyls [M(CO)x ]z- (M = Mn (x = 5, z = 1), Fe (x = 4, z = 2) or Co (x = 4, z = 1)) is explored using a [3]ferrocenophane scaffold. A gradual transition from η1 -, η2 - to η3 -coordination is observed where in the η2 -mode the terminal positions of the phosphorus chain are bridged. With an excess of cobalt carbonyl successive P-P bond activation and gradual separation of the central phosphorus atoms from the phosphorus chain has been observed. This process is reversible and with suitable reagents such as methyl lithium, the P3 -unit is regenerated in stereospecific manner. The bonding situation and steps of the gradual P-P bond activation are investigated by DFT calculations as well as experimental methods (e.g., NMR spectroscopy, X-ray crystallography).

Reversible P-P bond cleavage at an iridium(III) metal centre

Treatment of a κ¹-P-monodentate bicyclic diphosphane iridium(III) complex with a labile gold(I) precursor afforded an unusual Ir^III/Au^I complex in which the P-P single bond has been cleaved. This reaction was cleanly reversed upon addition of tertiary phosphine. Carbon-carbon bond activation, across neighbouring P₂C₂N rings of the coordinated bicyclic diphosphane, occurred upon thermolysis of the Ir^III/Au^I complex.

Metal–ligand cooperativity of a Co–P moiety

Metal–ligand cooperative redox reactions and intramolecular group transfer of a P–P containing dicobalt(i) species are shown.

Radical-Type Reactivity and Catalysis by Single-Electron Transfer to or from Redox-Active Ligands

Controlled ligand-based redox-activity and chemical non-innocence are rapidly gaining importance for selective (catalytic) processes. This Concept aims to provide an overview of the progress regarding ligand-to-substrate single-electron transfer as a relatively new mode of operation to exploit ligand-centered reactivity and catalysis based thereon.

Phosphido complexes derived from 1,1'-ferrocenediyl-bridged secondary diphosphines

This paper focuses on ferrocene-based secondary diphosphines of the type [Fe{η⁵-C₅H₄(PHR)}₂] with P-substituents of distinctly different steric and electronic properties, namely methyl, neopentyl (Np), tert-butyl, phenyl and 3,5-bis(trifluoromethyl)phenyl (XyF). The reaction of [Fe{η⁵-C₅H₄(PHPh)}₂] (H₂1a) and [Fe{η⁵-C₅H₄(PHt-Bu)}₂] (H₂1b) with n-BuLi in the presence of TMEDA afforded lithium diphosphides of the type [Li₂(μ-1)(TMEDA)₂], which contain a cyclic non-planar Li₂P₂ core. The analogous reactions of [Fe{η⁵-C₅H₄(PHMe)}₂] (H₂1c) and [Fe{η⁵-C₅H₄(PHNp)}₂] (H₂1d) furnished dimeric aggregates exhibiting a ladder-type Li₄P₄ motif, viz. [Li₄(μ-1c)₂(TMEDA)₃] and [Li₂(μ-1d)(TMEDA)]₂. H₂1e (R = XyF) did not afford a stable lithium diphosphide. A Brønsted metathesis with Zr(NMe₂)₄ was possible with the aryl-substituted compounds H₂1a and H₂1e, leading to products of the type [{Zr(NMe₂)₃}₂(μ-1)]. In contrast, the alkyl-substituted congeners H₂1b-H₂1d were inert towards Zr(NMe₂)₄. The reaction of [Fe{η⁵-C₅H₄(PHR)}₂] with nickelocene afforded intractable mixtures of numerous products in the case of H₂1c and H₂1e. In the other three cases, compounds of the type [(NiCp)₂(μ-1)] were isolated. For H₂1b and H₂1d a two-stepped reaction via a phosphino-phosphido intermediate of the type [NiCp(H1)] was observed, which could be isolated and fully characterised in the case of [NiCp(H1b)].

Redox-ligand sustains controlled generation of CF3 radicals by well-defined copper complex

A well-defined copper complex bearing iminosemiquinone ligands performs single electron reduction of an electrophilic CF3+ source into CF˙3 radicals. This redox behavior is enabled by the ligand which shuttles through two different redox states (iminosemiquinone and iminobenzoquinone) while the copper center is preserved as a Cu(ii). This system was used in the trifluoromethylation of silyl enol ethers, heteroaromatics and in the hydrotrifluoromethylation of alkynes. This is the first example of cooperative redox catalysis for the controlled generation of CF˙3 radicals.

Synthesis and solid-state structures of gold(i) complexes of diphosphines

A series of diphosphine bis(gold) complexes were synthesised and the importance of aurophilic interactions for their structure formation was studied.