Metal complexes CpMo

Few quantitative data are available on the relative nucleophilicities of L toward various alkyl carbonyls. The rates of the reaction of CpMo(CO)3Me with L in toluene (Table II) decrease as a function of the latter reactant P( -Bu)3 > P( -OBu)j > PPhj > P(OPh)j, but the spread is relatively small (<8). The above order is that customarily observed for 8 2 reactions of low-valent transition metal complexes (J, 214). Interestingly, neither CpMo(CO)3Me nor CpFe(CO)2Me reacts with 1 or N, S, and As donor ligands 28, 79). This is in direct contrast to the insertion reactions of MeMn(CO)5 which manifest much less selectivity toward various L (see Section VI,B,C,D for details). 

In some instances the decarbonylation can be effected, under mild conditions, by using a stoichiometric amount of a CO-abstracting metal complex. This method has proved to be fruitful for several CpFe(CO)2COR compounds (7, 2, 2a) and for CpMo(CO)2(PPh3)COPh 189) in conjunction with Rh(PPh3)jCl. 

Reduction of the metal dimer [CpMo(NO)l2]2 with Na/Hg in the presence of a variety of acyclic dienes generates the (diene)MoCp(NO) complexes in moderate to low isolated yield (equation 8)12,31,89. For the majority of diene ligands, complexes 60 are formed exclusively as the s-trans isomers as evidenced by NMR spectroscopy and single-crystal X-ray diffraction analysis. In comparison, complexation of the 2,3-dimethyl-l,3-butadiene initially gives a separable mixture of the s-trans (60) and s-d.v-complex (61). The s-cis isomer isomerizes to the more thermodynamically stable s-trans isomer in solution (THF, 1/2 = 5 min C6H6, ti/2 = 24 h). 

The iodide complexes, [CpMo(CO)3 (CH2)3I ] [M = Mo (96) or W (97)], were originally prepared by Winter and co-workers (162). Both 96 and 97 react with excess iodide to form [CpMfCOJjIfCOfCH CHj ]. Winter and co-workers found that transition metal anions may induce similar cyclization reactions. Hence, reaction of excess Na[CpMo(CO)3] with Br(CH2)3Br yields 89, which reacts with further Na[CpMo(CO)3] to form an intermediate anionic acyl complex, which in turn undergoes elimination of Br- to form the carbene ligand in a manner similar to that... 

Although charge transfers generally involve organics, iodine adducts of metal complexes are known. An example is [CpMo(NB u ) (fi-S) I2]21 where there is an I—I—S bond similar to those found for organic sulfur compounds such as 1,4,7-trithiacyclononane.11... 

CO substitution in heteronuclear cobalt carbonyl complexes has also been studied. Several phosphines were used in exchange reactions with CO in the complex CpMo(CO)3-Co(CO)4. Both a CO dissociative pathway, leading to substitution, and a radical chain pathway, initiated by associative attack of the phosphine and subsequent disproportionation (see Disproportionation), were found depending on reaction conditions (thermal or photochemical treatment) and the basicity and sterics of the phosphine ligands. As seen in substitution reactions with Co2(CO)g, strongly basic phosphines add to the complex via disproportionation, while less basic phosphines add via substitution. However, the metal centers help determine where the phosphine adds because the rates of substitution on each metal center differ depending on which pathway, dissociative or radical chain, is operative. ... 

Typical examples of the half sandwich type Cp complex are anionic zerovalent metal complexes of the type [CpM(CO)3]" and their binuclear derivatives [Cp2M2(CO)e] [12, 19]. Starting from the anion [CpM(CO)3] , a variety of complexes have been derived, including the neutral hydrides, CpMo(H)(CO)3, alkyls, CpM(R)(CO)3, [12] and the cationic allyl or diene complexes, [CpMo( n -C3H5)(NO)(CO)] [20, 21] or [CpMo(r -C4H5)(CO)2] [21, 22]. The stereochemistries of nucleophilic attack on the last two complexes have been extensively studied [23]. Permethylcyclopentadienyl of these complexes, e.g. (Ti -C5Me5)Mo(H)(CO)3 [24], have also been extensively reported. 

Scheme 2 Boron- and metal-centred substitution chemistry reported for the diborane(4)yl complex CpMo(CO)3B(NMe2)B(NMe2)Br (6.4)...

Although the origins of the trends in acidity and basicity are currently being studied, in many cases the third-row metal complexes are more basic than the second, which are more basic than the first. As discussed in more detail in Chapter 3, Os(CO) (H)2 is less acidic than Ru(CO) (H)2, which is less acidic than Fe(CO) (H)2, and CpW(CO)3H is less acidic than CpMo(CO)3H, which is less acidic than CpCr(CO)3H. 

Treatment of Cp"Cr(Ti -Cot), Cp" = Cp, Cp with (EtCN)3M(CO)3, M = Mo, W and Fe2(CO)9 affords the complexes [(Cp Cr)(CO)3M][ i-Cot], M = Fe, Cr, W, Cp = Cp and I(Cp Cr)(CO)3Crl/i-Cot, Cot = Cyclooctatetrane, which have been spectroscopically characterised. Bimetallic complexes containing bis(tetramethylcyclopentadienyl) dimethylsilane bridges have been prepared from the reaction of arene tricarbonyl molybdenum complexes with the silyl substituted cyclopentadienyl derivative. The synthesis of pinanylcyclopentadienes followed by metallation and reaction with Mo(CO)s and Mel gives the chiral (-)-[(ii -C5Me4-3-pinanyl)(CO)3Me], which has been structurally characterised. The chiral methallyl complexes CpMo(NO)X(Ti -2-methallyl) X = camphorsulfonate have been resolved and the reactions of the... 

Copper-metal bonds have been synthesized by the condensation of (NHC)CuOFt with the acidic metal hydride CpMo(H)(CO)3 [171], or by halide displacement from (NHC)copper(l) using anions such as CpFe(CO)2 and CpMo(CO)3" (Cp = ri -CjHj Scheme 11.6) [172]. The net metal-metal interaction in these complexes is a a-bond In (lDipp)Cu-Fe(CO)2Cp, with a Cu-Fe distance of only 2.3462(5) A, the HOMO—1 and HOMO are Fe- Cu ic orbitals, and the LUMO is the a orbital. Natural population analysis indicates significant ionic character, consistent with unequal sharing of an... 

Treatment of methoxynitrido cluster [Ru3(CO)9(//3-CO)(//3-NOMe)] with stoichiometric amounts of the hydrido complex [CpMo(CO)3H] in THF afforded two trinuclear Ru-Mo clusters 160 and 161, in which metal exchange has occurred. However, the same methoxynitrido cluster when reacted with the organomercurial [ CpMo(CO)3 2Hg] resulted in the formation of a pentanuclear trimetallic species 162. Although [CpMo(CO)3H] and [ CpMo(CO)3 2Hg] possess the same isolobal CpMo(CO)3 fragment, their reactivity is rather different. 

Bismuth - In three papers Norman and coworkers describe the synthesis of transition metal-bismuth complexes from metathesis reactions. Thus complexes ((CpMo(CX))3)2(M-ECN)]... 

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