The 3,5-Dichlorotrifluorophenyl Ligand, a Useful Tool for the Study of Coordination Modes and Dynamic Behavior of Complexes of Palladium and Platinum

Abstract

The square‐planar complexes [MR2L2] (M = Pd, Pt; R = 3,5‐C6Cl2F3) [L2 = OPPyPh2 (Py = 2‐pyridyl); SPPyPh2; OPPy2Ph; DMBI (3,3′‐dimethyl‐2,2′‐biindazole); OPPyPh(NHTol‐p); p‐TolNPPy2Ph] have been prepared by treating cis‐[MR2(THF)2] (THF = tetrahydrofuran) with the appropriate chelate ligands. The 19F‐NMR spectra of these complexes show the presence of intramolecular through‐space F‐F couplings between ortho‐fluorine atoms of nonequivalent R groups, which provide information for the assignment of the different ortho‐fluorine signals and can be used to study the dynamic behavior of the mentioned complexes such as: a) Rotation of the R group in either Pd or Pt complexes, at the same or at different rates for each R groups depending on the neutral ligand; and b) exchange of the coordination sites of the chelating ligand, either by Berry or by turnstile mechanisms. The activation parameters for some of the processes are given.

Formation of an Unsymmetrical Pt−Ir Tetraalkynyl Complex and Investigation into Subsequent Construction of Multimetallic Systems

“…In the ortho fluorine region the two signals located at high field have the appearance of triplets and are therefore attributed to ortho fluorine atoms of different rings . Coupling between ortho -F atoms of different rings is rare but not unknown . In our system, the attempts to confirm it by irradiation experiments on the meta -F signals at this low temperature were unsuccessful due to the separation of both meta -F resonances; but this scalar coupling through the space between two ortho -F of different rings was undoubtedly confirmed with a 19 F− 19 F COSY spectrum (193 K, Figure ).…”

“…The appearance of the ortho region corresponding to an AKXM part of a complex eight-spin system (which also includes the meta fluorine atoms; AK ortho -F of one ring and XM ortho -F of the other ring) with 4 J ortho -F - ortho - F in each ring ∼0, but with one strong inter-ring 19 F− 19 F coupling ( J AX or J KM ≠ 0), in addition to usual ortho -F− meta -F coupling.…”

Indirect Nonbonded Nuclear Spin–Spin Coupling: A Guide for the Recognition and Understanding of “Through-Space” NMR J Constants in Small Organic, Organometallic, and Coordination Compounds

“…This mode of structural identification used for fluorinated arene ligands was extended to palladium and platinum complexes of 3,5-dichlorotrifluorophenyl ligands (complexes of type 36a and 36b , Scheme ) . The existence of through-space coupling makes it possible to study the dynamic processes in which the internal motion does not change the chemical shift but rather changes the spin system.…”

Snapshots of a Stille reaction

“…For an easier monitoring of the cycle the studies were repeated on [Pd(C 6 Cl 2 F 3 )(OTf)(dppe)] 1b (C 6 Cl 2 F 3 = 3,5-dichlorotrifluorophenyl), which behaves identically to 1a and shows the same intermediates, but has more simple 19 F NMR spectra, facilitating a more accurate integration of the signals. 5 Scheme 1 shows, step by step, the mechanism of the catalytic cycle and the 1 H NMR spectra of the intermediates identified in the stoichiometric cycle for 1b while Fig. 1 shows the evolution of the reaction, as monitored by 19 F NMR.…”