Iridium Complexes with BIAN-Type Ligands: Synthesis, Structure and Redox Chemistry.

A series of iridium complexes with bis(diisopropylphenyl)iminoacenaphtene (dpp-bian) ligands, [Ir(cod)(dpp-bian)Cl] (1), [Ir(cod)(NO)(dpp-bian)](BF4)2 (2) and [Ir(cod)(dpp-bian)](BF4) (3), were prepared and characterized by spectroscopic techniques, elemental analysis, X-ray diffraction analysis and cyclic voltammetry (CV). The structures of 1-3 feature a square planar backbone consisting of two C = C π-bonds of 1,5-cyclooctadiene (cod) and two nitrogen atoms of dpp-bian supplemented with a chloride ion (for 1) or a NO group (for 2) to complete a square-pyramidal geometry. In the nitrosyl complex 2, the Ir-N-O group has a bent geometry (the angle is 125°). The CV data for 1 and 3 show two reversible waves between 0 and -1.6 V (vs. Ag/AgCl). Reversible oxidation was also found at E1/2 = 0.60 V for 1. Magnetochemical measurements for 2 in a range from 1.77 to 300 K revealed an increase in the magnetic moment with increasing temperature up to 1.2 µB (at 300 K). Nitrosyl complex 2 is unstable in solution and loses its NO group to yield [Ir(cod)(dpp-bian)](BF4) (3). A paramagnetic complex, [Ir(cod)(dpp-bian)](BF4)2 (4), was also detected in the solution of 2 as a result of its decomposition. The EPR spectrum of 4 in CH2Cl2 is described by the spin Hamiltonian H = gßHS with S = 1/2 and gxx = gyy = 2.393 and gzz = 1.88, which are characteristic of the low-spin 5d7-Ir(II) state. DFT calculations were carried out in order to rationalize the experimental results.

The Cluster Polyazide Complexes: Synthesis, Crystal Structures, and 14N NMR Studies of [{Re3(µ-X)3}(N3)9]3- (X = Br or I).

Azide cluster complexes [{Re3(µ-Br)3}(N3)9]3- and [{Re3(µ-I)3}(N3)9]3- were obtained by reaction of Re3X9 (X = Br or I, respectively) with sodium azide in methanol. The complexes were crystallized as cesium salts of the compositions Cs3[{Re3(µ-Br)3}(N3)9]·H2O (1) and Cs3[{Re3(µ-I)3}(N3)9]·H2O (2) and characterized by X-ray single-crystal diffraction and elemental analyses, mass spectrometry, 14N NMR spectroscopy, and DFT calculations. In the anions, each rhenium atom is coordinated by three azide ligands. To the best of our knowledge, these compounds represent the first case of metal cluster polyazide complexes (i.e., where each metal atom bears more than one azide ligand). Both complexes are stable in air but are very shock sensitive, and spontaneous explosive decomposition is also possible.

The Theoretical and Experimental Investigation of the Fluorinated Palladium ß-Diketonate Derivatives: Structure and Physicochemical Properties.

To search for new suitable Pd precursors for MOCVD/ALD processes, the extended series of fluorinated palladium complexes [Pd(CH3CXCHCO(R))2] with ß-diketone [tfa-1,1,1-trifluoro-2,4-pentanedionato (1); pfpa-5,5,6,6,6-pentafluoro-2,4-hexanedionato (3); hfba-5,5,6,6,7,7,7-heptafluoro-2,4-heptanedionato (5)] and ß-iminoketone [i-tfa-1,1,1-trifluoro-2-imino-4-pentanonato (2); i-pfpa-5,5,6,6,6-pentafluoro-2-imino-4-hexanonato (4); i-hfba-5,5,6,6,7,7,7-heptafluoro-2-imino-4-heptanonato (6)] ligands were synthesized with 70-80% yields and characterized by a set of experimental (SXRD, XRD, IR, NMR spectroscopy, TG) and theoretical (DFT, Hirshfeld surface analysis) methods. Solutions of Pd ß-diketonates contained both cis and trans isomers, while only trans isomers were detected in the solutions of Pd ß-iminoketonates. The molecules 2-6 and new polymorphs of complexes 3 and 5 were arranged preferentially in stacks, and the distance between molecules in the stack generally increased with elongation of the fluorine chain in ligands. The H…F contacts were the main ones involved in the formation of packages of molecules 1-2, and C…F, F…F, NH…F contacts appeared in the structures of complexes 4-6. The stability of complexes and their polymorphs in the crystal phases were estimated from DFT calculations. The TG data showed that the volatility differences between Pd ß-iminoketonates and Pd ß-diketonates were minimized with the elongation of the fluorine chain in the ligands.

Chirality and Relativistic Effects in Os3(CO)12.

The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os3(CO)12 with D3h and D3 symmetries using density functional theory (DFT) methods. The calculations took into account various levels of relativistic effects, including those associated with nonconservation of spatial parity. It was shown that the ground state of Os3(CO)12 corresponds to the D3 symmetry and thus may be characterized either as left-twisted (D3S) or right-twisted (D3R). The D3S↔D3R transitions occur through the D3h transition state with an activation barrier of ~10-14 kJ/mol. Parity violation energy difference (PVED) between D3S and D3R states equals to ~5 × 10-10 kJ/mol. An unusual three-center exchange interaction was found inside the {Os3} fragment. It was found that the cooperative effects of the mutual influence of osmium atoms suppress the chirality of the electron system in the cluster.

Parity violating energy difference for mirror conformers of DABCO linker between two M2+ cations (M = Zn, Cd, and Hg).

We have studied the potential energy surface of [ M 2 D A B C O ] 4 + cations (M = Zn, Cd, and Hg), which are considered as a model for the DABCO linker in metal-organic frameworks, a new prospective class of materials. Relativistic four-component and two-component calculations of parity violating energy difference (PVED) for twisted isomers of [ M 2 D A B C O ] 4 + cations have been performed. The right-twisted conformers of [ M 2 D A B C O ] 4 + are more stable than the left-twisted ones. The increase in PVED with the nuclear charge of the transition metal atom M (Z M ) is discussed.

A Localized Molecular Orbital Study of the Halogen Substitution Effect on (103)Rh NMR Shielding in [Cp*RhX2]2, Where X = Cl, Br, or I.

(103)Rh NMR parameters and the bonding structure of three complexes of [Cp*RhX2]2, where X = Cl, Br, or I, have been studied with the help of natural bond orbitals (NBOs) and natural localized molecular orbitals (NLMOs). The complexes of [Cp*RhX2]2, where X = Cl, Br, or I, have similar bonding structures, with the major difference being in the degree of covalency of the Rh-X bonds. The decomposition of (103)Rh NMR shielding into diamagnetic, paramagnetic, and spin-orbit terms shows that normal halogen dependence (NHD) of the (103)Rh NMR shift is defined mostly by the paramagnetic term, with the spin-orbit term being significantly smaller. The decomposition of (103)Rh shielding into spin-free NBO and NLMO contributions shows that (103)Rh shielding is dominated by Rh d-orbital deshielding contributions. We explain the NHD of the (103)Rh NMR shift with the increase in the energies of the virtual antibonding Rh-X orbitals along the X = Cl, Br, and I series.