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A competing redox reaction was observed with excess amounts of SnCl<jats:sub>2<\/jats:sub>, which produced a tetrapiperidinocyclobutadiene dication with two trichlorostannate(II) counterions. Heating neat <jats:bold>1<\/jats:bold> to 110\u2009\u00b0C for 16\u2005h cleanly produced the dimer 1,3,4,4\u2010tetrapiperidino\u20103\u2010buten\u20101\u2010yne (<jats:bold>3<\/jats:bold>); its reaction with stoichiometric amounts of SnCl<jats:sub>2<\/jats:sub> or GeCl<jats:sub>2<\/jats:sub>\u22c5dioxane furnished the 1,3,4,4\u2010tetrapiperidino\u20101,2\u2010cyclobutadiene tin and germanium dichloride complexes\u2005<jats:bold>4\u2009a<\/jats:bold> and <jats:bold>4\u2009b<\/jats:bold>, respectively. Transition\u2010metal complexes containing this novel four\u2010membered cyclic bent allene (CBA) ligand were prepared by reaction of <jats:bold>3<\/jats:bold> with [(tht)AuCl], [RhCl(CO)<jats:sub>2<\/jats:sub>]<jats:sub>2<\/jats:sub>, and [(Me<jats:sub>3<\/jats:sub>N)W(CO)<jats:sub>5<\/jats:sub>] to form [(CBA)AuCl] (<jats:bold>5<\/jats:bold>), [(CBA)RhCl(CO)<jats:sub>2<\/jats:sub>] (<jats:bold>6<\/jats:bold>), and [(CBA)W(CO)<jats:sub>5<\/jats:sub>] (<jats:bold>7<\/jats:bold>). The molecular structures of all compounds\u2005<jats:bold>2<\/jats:bold>\u2013<jats:bold>7<\/jats:bold> were determined by X\u2010ray diffraction analyses, and density functional theory (DFT) calculations were carried out to rationalise the formation of <jats:bold>3<\/jats:bold> and <jats:bold>4\u2009a<\/jats:bold>.<\/jats:p>","DOI":"10.1002\/chem.201904726","type":"journal-article","created":{"date-parts":[[2019,10,18]],"date-time":"2019-10-18T07:05:03Z","timestamp":1571382303000},"page":"16148-16155","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Dimerisation of Dipiperidinoacetylene: Convenient Access to Tetraamino\u20101,3\u2010Cyclobutadiene and Tetraamino\u20101,2\u2010Cyclobutadiene Metal Complexes"],"prefix":"10.1002","volume":"25","author":[{"given":"Ludwig","family":"Hackl","sequence":"first","affiliation":[{"name":"Institut f\u00fcr Anorganische und Analytische Chemie Technische Universit\u00e4t Braunschweig  Hagenring 30 38106 Braunschweig Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alex R.","family":"Petrov","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Anorganische und Analytische Chemie Technische Universit\u00e4t Braunschweig  Hagenring 30 38106 Braunschweig Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas","family":"Bannenberg","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Anorganische und Analytische Chemie Technische Universit\u00e4t Braunschweig  Hagenring 30 38106 Braunschweig Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matthias","family":"Freytag","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Anorganische und Analytische Chemie Technische Universit\u00e4t Braunschweig  Hagenring 30 38106 Braunschweig Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter G.","family":"Jones","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Anorganische und Analytische Chemie Technische Universit\u00e4t Braunschweig  Hagenring 30 38106 Braunschweig Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5364-0357","authenticated-orcid":false,"given":"Matthias","family":"Tamm","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Anorganische und Analytische Chemie Technische Universit\u00e4t Braunschweig  Hagenring 30 38106 Braunschweig Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2019,11,19]]},"reference":[{"key":"e_1_2_6_1_1","doi-asserted-by":"publisher","DOI":"10.1002\/anie.196405061"},{"key":"e_1_2_6_1_2","first-page":"537","volume":"76","year":"1964","journal-title":"Angew. 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