Cyclopentadienyl carbonyl

Mono( 17-cyclopentadienyl) carbonyl complexes of Ti, Zr, and Hf have been noted only in the patent literature. A U.S patent issued to Ethyl Corporation in 1962 described the use of such complexes as anti-knock agents and lubricant additives. Two examples of complexes purported to have been made are shown below (115). 

Group VIA (Cr, Mo, W). y-Radiolysis studies have been carried out for the simple hexacarbonyls (31,32) and for certain carbonyl iodides (33) and cyclopentadienyl carbonyl iodides (34). In the case of the hexacarbonyls (31,32), two free-radical products have been detected and characterized for Cr(C0)6, weak unidentified EPR signals have been observed for Mo(C0)6, but irradiated W(C0)6 apparently contains no detectable paramagnetic centres. 

There are several examples of mixed clusters which are homologous with the dode-cacarbonyls. Some of these compounds, such as the anion [FeCo3(CO)i2] and the neutral cyclopentadienyl carbonyl Co3Ni(CO)9Cp, are believed to be iso-structural with Co4(CO)j2 and it is therefore convenient to discuss these compounds now. 

The 18-electron rale is not obeyed as consistently by these types of oiganome-tank compounds a by the carbonyl and nitrosyl complexes and their derivatives. For example, in addition to ferrocene. M(i 5-CsHs)2 compounds are known for most of the other elements of the first transition series (M — V, Cr, Mn.Co, Ni) and these cannot obey ihe 18-electron rule. However, only ferrocene shows exceptional thermal stability (stable to 500 C) and is not oxidized by air. Furthermore, cobaltocene, a 19-electron species, is readily oxidized to the 18-electron cobaltocenium ion. (Co(ip-CsH )3)4 , which reflects much of the thermal stability of ferrocene. Mixed cyclopentadienyl carbonyl complexes are common K -CjHjMCO) ]. [(if-CjH )-Cr(CO), . [( -CjHOMnCCOjJ, [(>r-C,H,>Fe(CO ,, . [fo -CjiyCoCoy. and (ip-CsH,)Ni(CO) 2. Of interest is the fact that among these compounds, the odd-atomic-number elements (V. Mn, and Co) form monomers and the even-atomic-number elements (Cr. Fe. and Ni) Ibrm dimers, which is in direct contrast to the behavior shown by the simple carbonyl complexes. Cyclopentadienyl derivatives are now known for every main group and transition metal of the periodic table and for most of the -block metals.89... 

Ruthenium (t 5-Cyclopentadienyl)-carbonyl-(3,4-f 2-5.5,5-trifluoro-1.2.3-tris-[trifluoromelhyl]-l,3-pentadienyl)- XIII/9a. 563... 

Cyclopentadienyl carbonyl complexes, with niobium, 5, 64 Cyclopentadienyl chromium bis(Ti-allyl) complexes, with chromium, 5, 305-306 Cyclopentadienyl chromium carbonyls... 

C-H bond dissociation energies, 1, 298 C-N triple bond additions, 10, 427 C02, ketene, ketenimine complexes, 5, 84 CO and CNR reductive coupling, 5, 66 cyclopentadienyl alkyl and aryls, 5, 66 cyclopentadienyl carbonyl complexes, 5, 64 cyclopentadienyl hydrides, 5, 69 cyclopentadienyl isocyanide complexes, 5, 65 rf-acyl and rj2-iminoacyl complexes, 5, 82 fj3-complexes, 5, 87... 

In the reaction of the salts 3 with Li organic compounds two different types of products are formed simultaneously because LiR attacks cyclopentadienyl carbonyl cat-... 

In this case (compare with Ref. 268), the Te — Te bond remains. This bond is not destroyed also under interaction of diphenylditellurides with cyclopentadienyl-carbonyl complexes of manganese (3.99a) [272] and iron (3.99b) [273] ... 

In 1971 we succeeded, again for the first time, in transferring a carbene ligand from one metal atom to another (26, 47). For example, if one irradiates a solution of cyclopentadienyl(carbonyl) [methoxy (phenyl) carbene]-nitrosylmolybdenum(O) in the presence of an excess of pentacarbonyliron, one obtains tetracarbonyl[methoxy (phenyl) carbene]iron(0) with the simultaneous formation of cyclopentadienyl (dicarbonyl) nitrosylmolyb-denum ... 

Carbonylation of bis(cyclopentadienyl)vanadium(n) gives deep-brown paramagnetic Cp2VC0347fl whose low v(CO) of 1881cm-1 is quite common for bent bis(cyclopentadienyl)carbonyls of d2-dA metals. Cp2V(I)CO has v(CO) 1953 cm-1 in accord with the metal s increased oxidation state. 

---