Vinylidene, allenylidene, cyclic oxycarbene, and η2-alkyne complexes from reactions of (η5-C5Me5)OsCl(PPh3)2 with alkynes and alkynols

• Published in: Canadian journal of chemistry Vol. 99; no. 2; pp. 268 - 276
• Main Authors: Tse, Sunny Kai San, Sung, Herman Ho-Yung, Williams, Ian Duncan, Jia, Guochen
• Format: Journal Article
• Language: English
• Published: 1840 Woodward Drive, Suite 1, Ottawa, ON K2C 0P7 NRC Research Press 2021; Canadian Science Publishing NRC Research Press
• Subjects: alcyne; alkyne; Alkynes; alkynol; allenylidene; allénylidène; Chemical reactions; Chemicals; Osmium; Vinylidene; vinylidène
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/cjc-2020-0320

Reactions of Cp*OsCl(PPh 3 ) 2 (Cp* = pentamethylcyclopentadienyl) with alkynes and alkynols are described. Treatment of Cp*OsCl(PPh 3 ) 2 with phenylacetylene and trimethylsilylacetylene gave the vinylidene complexes Cp*OsCl(=C=CHPh)(PPh 3 ) and Cp*OsCl(=C=CH 2 )(PPh 3 ), respectively. Treatment of Cp*OsCl(PPh 3 ) 2 with the internal alkyne dimethyl acetylenedicarboxylate produced the η 2 -alkyne complex Cp*OsCl(η 2 -MeO 2 C≡CCO 2 Me)(PPh 3 ). Treatment of Cp*OsCl(PPh 3 ) 2 with the propargylic alcohol HC≡CC(OH)Ph 2 gave the osmium allenylidene complex Cp*OsCl(=C = C=CPh 2 )(PPh 3 ). The outcomes of the reactions of Cp*OsCl(PPh 3 ) 2 with ω-alkynols HC≡C(CH 2 ) n OH are dependent on the length of the -(CH 2 ) n - linker. The reaction with 3-butyn-1-ol produced the cyclic oxycarbene complex Cp*OsCl{=C(CH 2 ) 3 O}(PPh 3 ) exclusively. The reactions with 4-pentyn-1-ol produced a mixture of the hydroxyalkyl vinylidene complex Cp*OsCl{=C=CH(CH 2 ) 3 OH}(PPh 3 ) and the cyclic oxycarbene complex Cp*OsCl{=C(CH 2 ) 4 O}(PPh 3 ) in about 10:1 molar ratio. The reaction with 5-hexyn-1-ol gave exclusively the hydroxyalkyl vinylidene complex Cp*OsCl{=C=CH(CH 2 ) 4 OH}(PPh 3 ).