Cobalt Complexes of Silicon and Germanium Heterocyclotriynes with One or Two Cyclyne Rings Li Guo, Joseph M. Hrabusa III, Mark D. Senskey, David B. McConville, Claire A. Tessier,* and Wiley J. Youngs* Department of Chemistry, The University of Akron, Akron, Ohio 44325-3601 Received March 9, 1999 The synthesis and structural characterization of Ge(OBET) 2 , SiPh 2 (OBET)(Co 2 (CO) 6 ) 2 , and Ge(OBET) 2 (Co 2 (CO) 6 ) 2 are reported. Reaction of Li 2 (OBET), generated in situ from the reaction of nBuLi and o-(bisethynyl)tolane (OBET)H 2 , with GeCl 4 in a 2:1 molar ratio gave Ge(OBET) 2 in 64% yield. Ge(OBET) 2 was characterized by 1 H NMR, 13 C NMR, elemental analysis, FDMS, and X-ray crystallography. Co 2 (CO) 8 selectively complexes to the bent alkynes adjacent to Ge or Si of Ge(OBET) 2 and SiPh 2 (OBET) and severely distorts the ligands. Comparisons are made to related complexes. Introduction Tribenzocyclotriyne (TBC) and its analogues have demonstrated intriguing and diverse reactivities toward transition metals. 1 The important feature of this ligand system is that three soft, polarizable alkynes are fixed in a trigonal plane. It has been shown that the size of the transition metal is extremely important in deter- mining its coordination pattern toward TBC and the structure of mono metal complexes. The smaller transi- tion metals, cobalt, 2 nickel, 3 and copper, 4 reside in the pocket of TBC; whereas larger transition metals such as silver 5 form sandwich complexes. 6 The size of the central pocket of TBC can be altered by using thieno groups instead of benzene rings in the system (TTC). 7 This change results in dramatically different coordina- tion chemistry, demonstrated by the differences between the two cobalt complexes of TBC 2 and TTC 8 (see below for structures). In the TBC tetracobalt complex, one cobalt atom resides in the cavity of TBC. The other three cobalt atoms, one above each of the three alkynes, form a total of three Co-Co bonds with the cobalt atom at the center. In the TTC cobalt complex two dicobalt- hexacarbonyl moieties are bound to two alkynes, in the typical way that dicobalthexacarbonyl forms complexes with alkynes, 9 whereas the third alkyne remains un- complexed even if excess dicobalt octacarbonyl is used. Another way to alter the size of the central pocket is to substitute a heteroatom such as silicon or germanium for one of the benzene rings in TBC. We have previously described one such compound, SiPh 2 (OBET). 10 Here we report the synthesis and crystallographic characteriza- tion of the dipocket heterocyclyne Ge(OBET) 2 and the selective complexation of Co 2 (CO) 8 with SiPh 2 (OBET) and Ge(OBET) 2 . Experimental Procedures Materials. All chemicals were purchased from Aldrich and used as received unless otherwise stated. Solvents for reactions were dried and distilled before use. Tetrahydrofuran (THF) (Fisher), diethyl ether, and hexane were predried over sodium hydroxide and distilled from sodium benzophenone ketyl to which a small amount of tetraethylene glycol dimethyl ether was added. Germanium tetrachloride was purchased from Gelest and was distilled from anhydrous potassium carbonate (1) (a) Ferrara, J. D.; Tanaka, A. A.; Fierro, C.; Tessier-Youngs, C. A.; Youngs W. J. Organometallics 1989, 8, 2089. (b) Ferrara, J. D.; Tessier-Youngs, C.; Youngs, W. J. J. Inorg. Chem. 1988, 27, 2201. (c) Kinder, J. D.; Tessier, C. A.; Youngs, W. J. Synlett 1993, 149. (d) Youngs, W. J.; Kinder, J. D.; Bradshaw, J. D. Organometallics 1993, 12, 2406. (2) Djebli, A.; Ferrara, J. D.; Tessier-Youngs, C.; Youngs, W. J. J. Chem. Soc., Chem. Commun. 1988, 548. (3) Ferrara, J. D.; Tessier-Youngs, C.; Youngs, W. J. J. Am. Chem. Soc. 1985, 107, 6719. (4) Ferrara, J. D.; Tessier-Youngs, C.; Youngs, W. J. Organometallics 1987, 6, 676. (5) Ferrara, J. D.; Djebli, A.; Tessier-Youngs, C.; Youngs, W. J. J. Am. Chem. Soc. 1988, 110, 647. (6) (a) Dunbar, R. C.; Solooki, D.; Tessier, C. A.; Youngs, W. J.; Asamoto, B. Organometallics 1991, 10, 52. (b) Dunbar, R. C.; Uechi, G. T.; Solooki, D.; Tessier, C. A.; Youngs, W. J. J. Am. Chem. Soc. 1993, 115, 12477. (7) Solooki, D.; Kennedy, V. O.; Tessier, C. A.; Youngs, W. J. Synlett 1990, 7, 427. (8) Solooki, D.; Bradshaw, J. D.; Tessier, C. A.; Youngs, W. J. Organometallics 1994, 13, 451. (9) Sly, W. G. J. Am. Chem. Soc. 1959, 81, 18 (10) Guo, L.; Bradshaw, J. D.; Tessier, C. A.; Youngs, W. J. Organometallics 1995, 14, 586. 1767 Organometallics 1999, 18, 1767-1773 10.1021/om9901675 CCC: $18.00 © 1999 American Chemical Society Publication on Web 04/08/1999