Investigation of the Dynamic Solution Behavior of Chloro(diene)rhodium(I) Phosphine Complexes with a Pendant Unsaturated Heterocycle at Phosphorus (2-pyridyl, 2-imidazyl; diene = COD, NBD)

3H-1,3-Azaphospholo[4,5-b]pyridines--novel heterocyclic P,N-bridging or hybrid ligands: synthesis and first d(8)-transition metal complexes

The first 3H-1,3-azaphospholo-pyridines 2a-c were synthesized as racemic mixtures in modest to medium yield by the reaction of N-(2-chloropyrid-3-yl)-trimethylacetimidoyl chloride 1 with RPLi2 (R = Ph, n-Bu, i-Bu), generated from RPH2 and BuLi in THF at -70 °C, and studied with respect to their suitability as ligands (L) in transition metal complexes. Reactions of 2a with group 6 metal(0) pentacarbonyls led to P-coordinated LM(CO)5 complexes 3a-5a (Cr, Mo, W) and the reaction of 2c with (norbornadiene)Mo(CO)4 surprisingly to 4c. [Rh(1,5-COD)Cl]2 and 2a,b, in metal/ligand ratio 1 : 1, furnished LRh(1,5-COD)Cl complexes 6a,b with P-coordination, 6b accompanied by a minor contamination by the bis-coordinated L[Rh(COD)Cl]2 complex 7b. Reactions of 2a,b with [(allyl)PdCl]2 proceeded in THF with dismutation of N-coordinated (allyl)PdCl and formed with 2a a labile crude product [(2a){(allyl)PdCl}1.2(PdCl2)0.8]·C4H8O, with the composition close to L[Pd(allyl)Cl]PdCl2 THF (8a·THF), which converted during crystallization to 9a, whereas 2b directly formed the N,N'-PdCl2-bridged bis[LPd(allyl)chloride] complex 9b. Conversion of 2b with equimolar amounts of Pd(CH3CN)2Cl2 in THF, or Na2PdCl4 in methanol, gave rise to the dimeric P,N-bridging complex 10b. Crystal structure analyses of 6a (rac), 9b·2CDCl3 (meso), 10b·4.5THF and 10b·2D6-acetone (rac) provided detailed structural information. 10b, but more efficiently complexes formed in situ from 2a,b and Pd2(DBA)3 or Pd(OAc)2, catalysed the arylamination of 2-bromopyridine with 2,4,6-trimethylaniline.

Synthesis, structure, and characterization of dinuclear copper(I) halide complexes with P^N ligands featuring exciting photoluminescence properties

A series of highly luminescent dinuclear copper(I) complexes has been synthesized in good yields using a modular ligand system of easily accessible diphenylphosphinopyridine-type P^N ligands. Characterization of these complexes via X-ray crystallographic studies and elemental analysis revealed a dinuclear complex structure with a butterfly-shaped metal-halide core. The complexes feature emission covering the visible spectrum from blue to red together with high quantum yields up to 96%. Density functional theory calculations show that the HOMO consists mainly of orbitals of both the metal core and the bridging halides, while the LUMO resides dominantly on the heterocyclic part of the P^N ligands. Therefore, modification of the heterocyclic moiety of the bridging ligand allows for systematic tuning of the luminescence wavelength. By increasing the aromatic system of the N-heterocycle or through functionalization of the pyridyl moiety, complexes with emission maxima from 481 to 713 nm are obtained. For a representative compound, it is shown that the ambient-temperature emission can be assigned as a thermally activated delayed fluorescence, featuring an attractively short emission decay time of only 6.5 μs at ϕPL = 0.8. It is proposed to apply these compounds for singlet harvesting in OLEDs.