10.1021/om010800y.s002 Michael C. Janzen Michael C. Janzen Hilary A. Jenkins Hilary A. Jenkins Michael C. Jennings Michael C. Jennings Louis M. Rendina Louis M. Rendina Richard J. Puddephatt Richard J. Puddephatt Ring Expansion and Contraction in Reactions of an Alkyne with Stannylplatinum(IV) Metallacycles:  Formation of an Alkyl(alkenyl)(alkynyl)platinum(IV) Complex American Chemical Society 2002 PtMe 2 electrophilic alkyne RCCR bu 2 bpy metallacycle CO ESnMe Se SnMe 2002-02-16 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Ring_Expansion_and_Contraction_in_Reactions_of_an_Alkyne_with_Stannylplatinum_IV_Metallacycles_Formation_of_an_Alkyl_alkenyl_alkynyl_platinum_IV_Complex/3767583 The five-membered stannylplatinum(IV) metallacycles [PtMe<sub>2</sub>{SnMe<sub>2</sub>ESnMe<sub>2</sub>E}(bu<sub>2</sub>bpy)], E = S, Se, Te, bu<sub>2</sub>bpy = 4,4‘-di-<i>tert</i>-butyl-2,2‘-bipyridine, undergo facile ring expansion by insertion of the electrophilic alkyne RCCR, R = CO<sub>2</sub>Me, into the PtE−Sn bond to yield the corresponding seven-membered metallacycles [PtMe<sub>2</sub>{SnMe<sub>2</sub>ESnMe<sub>2</sub>CRCRE}(bu<sub>2</sub>bpy)]. The seven-membered metallacycles slowly eliminate “Me<sub>2</sub>SnE” to give new five-membered metallacycles [PtMe<sub>2</sub>{SnMe<sub>2</sub>CRCRE}(bu<sub>2</sub>bpy)]. When E = Se, reaction with excess RCCR gives the complex [PtMe<sub>2</sub>(CRCRH)(CCR)(bu<sub>2</sub>bpy)], which contains alkyl, alkenyl, and alkynyl functionalities in the same molecule. In the presence of excess RCCR and [(Me<sub>2</sub>SnSe)<sub>3</sub>], the products Se(<i>Z</i>-CRCHR)<sub>2</sub> and the selenole Se(CRCRCRCR) are formed catalytically.