Dimerisation of Dipiperidinoacetylene: Convenient Access to Tetraamino-1,3-Cyclobutadiene and Tetraamino-1,2-Cyclobutadiene Metal Complexes.

ABSTRACT: The reaction of 1,2-dipiperidinoacetylene (1) with 0.5?equivalents of SnCl2 or GeCl2 ?dioxane afforded the 1,2,3,4-tetrapiperidino-1,3-cyclobutadiene tin and germanium dichloride complexes?2?a and 2?b, respectively. A competing redox reaction was observed with excess amounts of SnCl2 , which produced a tetrapiperidinocyclobutadiene dication with two trichlorostannate(II) counterions. Heating neat 1 to 110?°C for 16?h cleanly produced the dimer 1,3,4,4-tetrapiperidino-3-buten-1-yne (3); its reaction with stoichiometric amounts of SnCl2 or GeCl2 ?dioxane furnished the 1,3,4,4-tetrapiperidino-1,2-cyclobutadiene tin and germanium dichloride complexes?4?a and 4?b, respectively. Transition-metal complexes containing this novel four-membered cyclic bent allene (CBA) ligand were prepared by reaction of 3 with [(tht)AuCl], [RhCl(CO)2 ]2 , and [(Me3 N)W(CO)5 ] to form [(CBA)AuCl] (5), [(CBA)RhCl(CO)2 ] (6), and [(CBA)W(CO)5 ] (7). The molecular structures of all compounds?2-7 were determined by X-ray diffraction analyses, and density functional theory (DFT) calculations were carried out to rationalise the formation of 3 and 4?a.

SUBMITTER: Hackl L 

PROVIDER: S-EPMC6973143 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature