Electronic manipulation of the agostic and syndetic components in 1-tetralone oxime and imine complexes of palladium (II)

Abstract

Structural, spectroscopic, QTAIM and NBO analysis results obtained from disperson-corrected density functional theory (DFT-D) calculations on the agostic intermediate [PdCl2(1-tetralone oxime)] (1) show that both agostic CHσ and syndetic CCπ donations are effected by electronic substituents on the aromatic ring. Changing the C5-substituent in 1 to σ-electron withdrawing SO2Cl unexpectidly increases both the agostic and π-donations; π-electron withdrawing N2PO(OEt)2 increases the agostic donation but the π-donation is replaced by C8 to Pd covalency; σ-electron donating B(OH)3− gives similar agostic donation to H but the syndetic π-donation increases markedly; π-electron donating S− reduces the agostic donation almost to zero and the syndetic π-donation turns to Pd to C8 covalency. For (N)OMe ligand [PdCl2(1-tetralone imine)] agostic complex (7), σ-electron withdrawing SO2Cl at C5 shows similar agostic and π-donations to the (N)OH analogue; π-electron withdrawing N2PO(OEt)2 changes 7 to an anagostic complex; σ-electron donating B(OH)3− produces less syndetic π-donation than in the (N)OH analogue and π-electron donating S− reduces the agostic donation much less than the (N)OH analogue but retains the PdC8 covalency arising from carbon based orbitals. For the σ and π-electron withdrawing NN+ BF4− substituent, PdC8 covalency arises from metal based orbitals.