A palladium complex of a macrocyclic selenium ligand: catalyst for the dehydroxymethylation of dihydroxy compounds.

This report describes the synthesis of a seventeen-membered macrocyclic ring containing ligand (L1) by the reaction of 1,8-bis(2-(chloromethyl)phenoxy)octane with selenium powder. The trans-palladium dichloride complex (C1) of the macrocyclic selenium ligand was synthesized from its reaction with the Pd(CH3CN)2Cl2 precursor. The formation of the ligand and complex was authenticated with the help of various analytical techniques like 1H and 13C{1H} NMR, HRMS, FTIR, UV-visible spectroscopy, and elemental analysis. The structure of the ligand and its coordination mode with the palladium precursor were authenticated with the help of single crystal X-ray diffraction. The complex possesses a distorted square planar geometry around the palladium center. The new ligand and complex are air and moisture insensitive and stable at room temperature for over three months. The variable temperature NMR data and computational studies suggest selenium inversion in the palladium complex (C1) with an inversion barrier of ∼22.6 kcal mol-1. The palladium complex C1 was used as a catalyst for the dehydroxymethylation of long alkyl chain containing dihydroxy compounds. Generally, two separate catalysts are used for dehydroxymethylation (one for the oxidation of the alcohol and the other for the decarbonylation of the aldehyde). Here a single catalyst shows the dual action of dehydroxymethylation with up to 91% yield under only 5.0 mol% catalyst loading. A broad substrate scope can be achieved with good functional group tolerance. The PPh3 and Hg poisoning tests suggest the homogeneous nature of the reaction. Interestingly, the same long alkyl chain containing dihydroxy compounds were reported to undergo macrolactonization when reacted with a ruthenium catalyst.

Theoretical study of photodetachment processes of anionic boron clusters. I. Structure.

Photo-induced electron detachment spectroscopy of anionic boron clusters, B(4)(-) and B(5)(-), is theoretically investigated by performing electronic structure calculations and nuclear dynamics simulations. While the electronic potential energy surfaces (X(1)A(g), ã(3)B(2u), b(3)B(1u), Ã(1)B(2u), c(3)B(2g), and B(1)B(2g) of neutral B(4) and X(2)B(2), Ã(2)A(1), B(2)B(2), C(2)A(1), D(2)B(1), and E(2)A(1) of neutral B(5)) and their coupling surfaces are constructed in this paper, the details of the nuclear dynamics on these electronic states are presented in Paper II. Electronic structure calculations are carried out at the complete active space self-consistent field-multi-reference configuration interaction level of theory employing the correlation consistent polarized valance triple zeta basis set. Using the calculated electronic structure data suitable vibronic Hamiltonians are constructed utilizing a diabatic electronic basis and displacement coordinates of the normal vibrational modes. The theoretical results are discussed in relation to those recorded in recent experiments.

Theoretical study of photodetachment processes of anionic boron clusters. II. Dynamics.

Photodetachment bands of anionic boron clusters, B(n) (n = 4,5) are theoretically examined here. The model Hamiltonians developed through extensive ab initio quantum chemistry calculations in Paper I are employed for the required nuclear dynamics study. While the precise location of vibronic lines and progression of vibrational modes within a given electronic band is derived from time-independent quantum mechanical studies, the broadband spectral envelopes and the nonradiative decay rate of electronic states are calculated by propagating wave packets in a time-dependent quantum mechanical framework. The theoretical results are in good accord with the experiment to a large extent. The discrepancies between the two can be partly attributed to the inadequate energy resolution of the experimental results and also to the neglect of dynamic spin-orbit interactions and computational difficulty related with detachment channels involving multi-electron transitions in the theoretical formalism.