Structural elucidation of tungsten compounds containing arylamine, piperazine and morpholine fragments of pyrrole and keto-amine ligands. (24th November 2015) - Chen, Guan-Xuan
Graphical abstract: Various imido tungsten derivatives incorporating bi-dentate pyrrole–piperazine, pyrrole–morpholine, pyrrole–imine and keto-amine precursors were synthesized and characterized by 1 H and 13 C NMR spectroscopy and single crystal X-ray diffraction analysis. Abstract: Various imido tungsten derivatives incorporating bidentate pyrrole–piperazine, pyrrole–morpholine, pyrrole–imine and keto-amine precursors were synthesized. Reacting W(N t Bu)2 (NH t Bu)2 with one equivalent of the pyrrole–phenylpiperazine ligand {C4 H3 NH-[2-CH2 N(CH2 CH2 )2 NPh]} in toluene generated [W(N t Bu)2 (NH t Bu){C4 H3 N-[2-CH2 N(CH2 CH2 )2 NPh]}] (1 ). Similarly, addition of W(N t Bu)2 (NH t Bu)2 to one equivalent of the pyrrole–morpholine ligand {C4 H3 NH-[2-CH2 N(CH2 CH2 )2 O]} in toluene afforded [W(N t Bu)2 (NH t Bu){C4 H3 N-[2-CH2 N(CH2 CH2 )2 O]}] (2 ), which was converted to [W(N t Bu)2 {C4 H3 N-[2-CH2 N(CH2 CH2 )2 O]}]2 (μ2 -O) (3 ) in moisture. Reacting the pyrrole–imine ligand {C4 H3 NH-[2-CHN(C6 H3 -2, 6- i Pr2 )]} with one equivalent of W(N t Bu)2 (NH t Bu)2 in toluene gave [W(N t Bu)2 (NH t Bu){C4 H3 N-[2-CHN(C6 H3 -2, 6- i Pr2 )]}] (4 ), which was transformed to [W(N t Bu)(NH t Bu){C4 H3 N-[2-CHN(C6 H3 -2, 6- i Pr2 )]}(μ-O)]2 (5 ) upon absorbing moisture. Furthermore, when one equivalent of {C4 H3 NH-[2-CHNC2 H4 N(C2 H4 )2 O]} reacted with W(N t Bu)2 (NH t Bu)2 in toluene, {W(N t Bu)2 {C4 H3 N-[2-CHNC2 H4 N(C2 H4 )2 O]}2 } (6 ) was isolated. The tungsten keto-amine compounds {W(N t Bu)2 [OCMeCHCMeN(C6 H3 -2, 6- i Pr2 )]2 } (7 ) and {W(N t Bu)2 [OCMeCHCMeNCH2 CH2 N(CH2 CH2 )2 O]2 } (8 ) were obtained by the reaction between W(N t Bu)2 (NH t Bu)2 and two equivalents of the corresponding keto-amine ligands in toluene. All the tungsten derivatives were characterized by 1 H and 13 C NMR spectroscopy. Single crystal X-ray diffraction analysis revealed that in compounds, 1, 3, 5, 6 and7, the central W atom belonged to either a distorted trigonal bipyramidal or an octahedral geometrical arrangement. Overall, the influence of the substituted pyrrole and keto-amine bidentate precursors on the imido tungsten derivatives were explored and structurally constructed.