Highly Reduced Organometallics. 32. Cyclopentadienyl- and Pentamethylcyclopentadienyl-Substituted Heptacarbonyls of Zerovalent Titanium, Zirconium, and Hafnium, [(C5R5)M(CO)4], and Derivatives Thereof

John E Ellis, Scott R. Frerichs, Beatrice Kelsey Stein

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Abstract

Reduction of (C5R5)MCl3 (R = H, Me; M = Ti, Zr, Hf) by alkali-metal naphthalenides at low temperature followed by carbonylation at atmospheric pressure provided 40–75% isolated yields of [(C5R5)Ti(CO)4] as Et4N+ salts and 15–40% isolated yields of the corresponding zirconium and hafnium salts. Also, [(C5Me5)Hf(CO)4]was isolated in 40–50% yields as pure [K(cryptand 2.2.2)]+ or [K(15-crown-5)2]+ salts. Except for unsolvated Na[(C5H5)Ti(CO)4], which proved to be explosive at room temperature, the other compounds were quite thermally stable materials and were easily handled in the absence of oxygen and moisture. Interactions of the carbonyltitanates and -zirconates with Ph3SnCl and Ph3PAuCl provided what are believed to be the first series of heterobimetallic complexes to contain tin and gold atoms bound to Ti(II) and Zr(II). Although the zirconium complexes (C5R5)Zr(CO)4E (E = SnPh3, AuPPh3) proved to be too thermally unstable for isolation, their spectral properties were very similar to those of the significantly more robust titanium analogs. Reaction of [(C5Me5)Ti(CO)4] with I2 provided the very thermally unstable (C5Me5)Ti(CO)4I, which in turn gave a more stable dmpe derivative, (C5Me5)Ti(CO)2(dmpe)I (dmpe = 1,2-bis(dimethylphosphino)ethane). The IR and NMR spectral properties of the latter substance are compared to those of (C5Me5)Zr(CO)2(dmpe)Cl and (C5-Me5)Hf(CO)2(dmpe)Cl, which are believed to have quite similar half-sandwich molecular structures. The divalent Zr and Hf carbonyl chlorides were obtained by the reductive carbonylation of the corresponding (C5Me5)MCl3 in the presence of dmpe. Of the three halocarbonyl–dmpe complexes described herein, only the hafnium complex was sufficiently robust to be isolated as a pure substance.

Original languageEnglish (US)
Pages (from-to)1048-1057
Number of pages10
JournalOrganometallics
Volume12
Issue number4
DOIs
StatePublished - Jan 1 1993

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