Potassium cyclopentadienyl derivatives

The broader subject of the interaction of stable carbenes with main-group compounds has recently been reviewed. Accordingly, the following discussion focuses on metallic elements of the s and p blocks. Dimeric NHC-alkali adducts have been characterized for lithium, sodium, and potassium. For imidazolin-2-ylidenes, alkoxy-bridged lithium dimer 20 and a lithium-cyclopentadienyl derivative 21 have been reported. For tetrahydropyrimid-2-ylidenes, amido-bridged dimers 22 have been characterized for lithium, sodium, and potassium. Since one of the synthetic approaches to stable NHCs involves the deprotonation of imidazolium cations with alkali metal bases, the interactions of alkali metal cations with NHCs are considered to be important for understanding the solution behavior of NHCs. 

The low-valency cyclopentadienyl vanadium complexes are usually stabilized by carbon monoxide, and VCp(CO)4 is the most useful precursor to various low-valency organovanadium complexes. There are a number of synthetic routes to VCp(CO)4. One convenient method is to carry out the reaction between NaCp and VCl3 in THF in situ and then to carbonylate under 60 atm CO pressure at 120 °C [19]. Reduction of preformed vanadocene by potassium, and subsequent carbonylation also gives rise to VCp(CO)4 [20]. These methods, however, cannot be applied to alkyl-substituted cyclopentadienyl derivatives. It is necessary to treat alkyl-substituted cyclopentadiene... 

Roesky introduced bis(iminophosphorano)methanides to rare earth chemistry with a comprehensive study of trivalent rare earth bis(imino-phosphorano)methanide dichlorides by the synthesis of samarium (51), dysprosium (52), erbium (53), ytterbium (54), lutetium (55), and yttrium (56) derivatives.37 Complexes 51-56 were prepared from the corresponding anhydrous rare earth trichlorides and 7 in THF and 51 and 56 were further derivatised with two equivalents of potassium diphenylamide to produce 57 and 58, respectively.37 Additionally, treatment of 51, 53, and 56 with two equivalents of sodium cyclopentadienyl resulted in the formation of the bis(cyclopentadienly) derivatives 59-61.38 In 51-61 a metal-methanide bond was observed in the solid state, and for 56 this was shown to persist in solution by 13C NMR spectroscopy (8Ch 17.6 ppm, JYc = 3.6 2/py = 89.1 Hz). However, for 61 the NMR data suggested the yttrium-carbon bond was lost in solution. DFT calculations supported the presence of an yttrium-methanide contact in 56 with a calculated shared electron number (SEN) of 0.40 for the yttrium-carbon bond in a monomeric gas phase model of 56 for comparison, the yttrium-nitrogen bond SEN was calculated to be 0.41. 

The relatively strong Bronsted acidity of cyclopentadienes, indenes, and fluorenes, permits the formation of alkali metal compounds of the conjugate bases of these organic molecules by direct reaction with the metal. The effect of substitnents on the rate of formation of 9-R-fluorenylhthium componnds in THE solution and on the degree of ion pairing in solutions of these species has been determined. Potassinm derivatives are commonly prepared by the reaction of the cyclopentadiene with potassium bis(trimethylsilyl)amide. Eluorenyl and indenyl compounds with the heavier alkah metals, Rb and Cs, are also prepared by reaction with the metal bis(trimethylsilyl)amide. The cyclopentadienyl ring in alkali metal compounds can also be coordinated to other metals. ... 

Fe(CO)4H2 Iron tetracarbonyl dihydride, 2 243 potassium salt, 2 244 sodium salts, 7 194, 197 [Fe(C204)3]K3-3H20 Potassium trioxalatoferrate(III), 1 36 FeC6Hs(CO)2l Cyclopentadienyl-iron dicarbonyl iodide, 7 110 FeC6H5(CO)2Na Cyclopentadi-enyliron dicarbonyl, sodium derivative, 7 112 [FeC6H5(CO)2]2 Cyclopentadi-enyliron dicarbonyl, dimer, 7 110... 

---