Pyrrolyl complex

Diboracyclopentadioiyl Complexes.—MO calculations have been performed for the isoelectronic series [CpFefCOa], [ M13-dibora-2-thiacyclopentadienyl)]-Fe(CO)s, and [ -(l,3-diaza-2-boracyclopentadienyl)]Cr(CO)3. New ri -(l,3-dimethyl-4,5-diethyl-l,3-dibora-2-thiacyclopentadienyl) complexes (L) of the type LaM(CO)a (M = Cr and Mo) and poly-decker complexes of the types CpFe(L)Mn(CO)a, [( -PhH)Fe(L)Mn(CO)3]+/ and (OC)sMn(L)Fe(L)-Mn(CO)s have been prepared. Related complexes of the type CpNiL and [CpNi(L)NiCp] [ = 0 and 1 L = j -(2-methyl-l,3,4,5-tetraethyl-l,3-diboracyclopentadienyl)] have also been synthesized.  

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Cobalt complex 83 was obtained by the reaction of [CpCo(SMe2)3l2(BF4)2 with pentamethylpyrrole [88AG(E)579]. Full cobalt sandwich of 2,5-di-terr-butyl-pyrrole is also known [91JCS(CC)1368]. Meanwhile, attempts to synthesize other pyrrolyl complexes of cobalt, (Ti -2,5-dimethylpyrrole)cobalttricarbonyl and the 3,4-dimethyl analog, have been unsuccessful [87JOM(330)231]. 

A model similar to that of the iron complex 31 was proposed for the cobalt species synthesized as a result of co-condensation of cobalt vapors with pyrrole in vacuum. A frozen matrix formed is subsequently warmed to room temperature (89JA3881). An oligomer or a polymer results, in which a- and ir-donor functions are realized simultaneously. The model proposed differs from that for the iron pyrrolyl complex by inclusion of the Co—Co bonds to attain the 18-electron configuration. 

Notably, similar reactivity is also observed with diphenylamido or pyrrolyl complexes, which give the corresponding monosiloxy surface complexes, as evidenced by mass balance analyze, IR and NMR data [74]. 

The 7T-pyrrolyl complex C5H5FeC4H4N shows four fragmentation paths of the molecular ion, all of which are confirmed by observation of the appropriate metastable peaks. Thus M+ fragments either by loss of C2H2, HCN, C2H2N, or the entire C4H4N unit. Further fragmentations are as expected for cyclopentadienyl compounds (117). 

N-Bonded pyrrolyl complex 392 is prepared from the reaction of (PMe2Ph)3ReCl3 with excess pyrrolyllithium in ether at room temperature [243]. The reaction of 392 with DMAD (169) is the first Michael type reaction observed for the N-bonded pyrrole complex. The reaction proceeds at room temperature in the presence of a catalytic amount of acetic acid in toluene for 3 days (Scheme 80). 

Iridium pyrrolyl complex 247, derived from sodium pyrrolide and Ir(CO)Cl(PPh3)2 248 (see also Section 3.02.2.2.1), reacts with a variety of Si-, Sn-, B-containing substrates ultimately to produce N-substituted pyrroles 249-252 (Scheme 51) <19980M1134>. 

To close this review, it seems appropriate to mention azametallocenes. These 7 -pyrrolyl complexes have been known for a long time and their chemistry has been recently reviewed This chemistry appears to be radically different from that of phospha-, arsa-and stibametallocenes. We can briefly summarize the comparison by the following statements ... 

The reaction of Mn2(CO)jo with pyrrole in petroleum ether at 130°C affords bright orange crystals (m.p. 40.5°C) of a Tr-pyrrolyl complex (C4H4N)Mn(CO)3 (321). 

SCHEME E Synthesis of the anionic and neutral palladium pyrrolyl complexes and their reactivities... 

The syntheses and structures of similar dipyrrolylmethane complexes have been reported. Alkynes are rapidly hydroaminated by primary amines catalyzed by these Ti derivatives.711 Hydroamination of enynes to generate a,/ -unsaturated imines can be produced using titanium pyrrolyl complexes.712... 

Metal complexes containing the anionic pyn olyl ligands are much more frequent throughout the periodic table, and the Tj N and Tj binding modes are dominant in the coordination chemistry of such anions [1, 13]. ri N-Pyrrolyl complexes may be synthesized by in situ N-H activation of Pyr by a low-valent metal fragment as in Eq. 

Tf s-pyrrolyl complexes are stable due to the polyhapto binding mode, but they are less stable than iq -cyclopentadienyl compounds. It remains controversial whether this difference in stability stems from a thermodynamic or kinetic effect.Nevertheless, the high stability of ri -pyrrolyl complexes allows several chemical modifications to be performed directly on the five-membered ring. ° Lithiation and alkylation of the resulting anion is shown in Equation 4.29. ... 

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