Synthesis, structure, and reactivity of doubly trans-spanning bis(dialkyl selenide) complexes; a new route to diselenamacrocycles via alkene metathesis in metal coordination spheres
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2018 Elsevier B.V. The reaction of selenium with NaBH4 and Br(CH2)6CH=CH2 (2.0 equiv each) gives the dialkyl selenide Se((CH2)6CH=CH2)2 (91% after workup) which is combined with PtCl2 (0.5 equiv, toluene) to give trans-PtCl2(Se((CH2)6CH=CH2)2)2 (10, 85%). The reaction of 10 and Grubbs' first generation catalyst yields macrocyclic[Figure presented] (11, 60%) as a mixture of syn/anti isomers with respect to the selenium lone pairs. The reaction of 11 and Ph2Zn gives the diphenyl complex[Figure presented] (12, 86%; mixture of isomers). When 11 is treated with H2 under conditions that hydrogenate related diphosphine complexes (5 bar, 50 C, (Ph3P)3RhCl or PtO2, CH2Cl2), no reaction occurs. Under more forcing conditions, (8 bar, 85 C, Pd/C, C2H5OH), 11 and 12 give the demetalated diselenamacrocycle Se(C14H28)2Se (13; 72-67%). The crystal structures of 11 and 12 show anti selenium lone pairs and trans C=C linkages; that of 13 exhibits columns of extended macrocycles.