Iron complex boryl

The first ruthenium dihaloboryl Cp/Ru(CO)2BCl2 (8.102) has recently been spectroscopically characterized, although no structural data were reported [60]. As with the related iron complex CpFe(CO)2BCl2 (8.35), 8.102 exhibits the relatively downfield-shifted 11B resonance (5b 81.0) and high frequency carbonyl stretching bands (2012, 1958 cm-1), expected for a boryl system featuring poorly 7r-donating substituents. The ferrocenyl(bromo)boryl complex Cp/Ru(CO)2B(Fc)Br (8.101) has also been synthesized recently and has spectroscopic properties similar to those of the closely related iron systems 8.63 and 8.64 [92]. 

The proposed mechanism for Fe-catalyzed 1,4-hydroboration is shown in Scheme 28. The FeCl2 is initially reduced by magnesium and then the 1,3-diene coordinates to the iron center (I II). The oxidative addition of the B-D bond of pinacolborane-tfi to II yields the iron hydride complex III. This species III undergoes a migratory insertion of the coordinated 1,3-diene into either the Fe-B bond to produce 7i-allyl hydride complex IV or the Fe-D bond to produce 7i-allyl boryl complex V. The ti-c rearrangement takes place (IV VI, V VII). Subsequently, reductive elimination to give the C-D bond from VI or to give the C-B bond from VII yields the deuterated hydroboration product and reinstalls an intermediate II to complete the catalytic cycle. However, up to date it has not been possible to confirm which pathway is correct. 

Heteroalkenes, with iron, 6, 132 Heteroannulation, allylic benzylamines, 10, 156 Heteroarene chromium carbonyls, preparation and characteristics, 5, 260 Heteroarenes borylation, 10, 242 C—H functionalizations, 10, 127 as metal vapor synthesis milestone, 1, 237 with titanium, 4, 246 vanadium complexes, 5, 48 7]6-Heteroarenes, with platinum, 8, 664 Heteroaromatic compounds... 

Table 4 Selected spectroscopic and structural parameters for iron boryl complexes... 

First reported in 2002, aryl(halo)boryl complexes of iron represent versatile precursors for a number of related ligand systems via boron-centred reactions which proceed with retention of the Fe-B bond [62,88-90]. Complexes bearing differing aryl substituents have been synthesized via the general route shown in Scheme 8, allowing for varying degrees of steric bulk at the boron centre. 

Given the structural and reaction studies carried out on iron amino- and aryl(halo)boryl complexes, research effort has also been directed at analogous aryloxy(halo)boryl systems. The complexes ( 5-C5R5)Fe(CO)2B(OMes)X (R = H, X = Cl, 8.55 R = H, X = Br, 8.56 R = Me, X = Cl, 8.57) have been synthesized from the reaction of the corresponding haloborane with one equivalent of Na[( 5-C5R5)Fe(CO)2] (Fig. 22) [75]. Boryl complexes 8.55 and 8.57 both feature relatively short Fe-B distances [1.977(4) A for each] with the torsion angle (0) for 8.57 [87.6°] being consistent with the possibility for tc overlap between the boron-centred p orbital and the metal-based HOMO-2. 

Hartwig showed in 1997 that an iron boryl complex can cleave the C-H bond of a simple alkane under photochemical conditions [83, 84], but this reactivity was not exploited for C-C bond formation to date. 

Iron, Ruthenium, and Osmium - In this section of work Fp = Fe(CO)2Cp - and Rp = Ru(CO)2Cp is used throughout. The inclusion compounds of aromatic ruthenium complexes, e.g. (Bn)Ru(Cp) PF in a-cyclodextrin has been investigated and die mentioned example has been crystallographically characterised. Two transition m boryl complexes, FpB(OCeH40) and FpBPh2 have been reported the reaction of the former complex with Et2NH results in the formation of FpH and die aminoborane. Gas phase and solution studies have been carried out on the first pentafluorocyclopentadienyl complex ICp Rufn-CsFs)]. The redox chemistry of this complex is not unusual in any way. ... 

Transition-metal-catalyzed ring-opening functionalizations of donor - acceptor cyclopropanes have also been developed (Table 2.2). Addition of carbon nucleophiles to activated VCPs 69b and 69c in the presence of iron catalysts induced ring opening of the three-membered ring [81, 82]. A palladium pincer complex catalyzed ring-opening borylation of VCP 69c with 62(011)4 to produce... 

Iron carbonyl fragments have been incorporated into many heterometallic borane and carborane compounds. Those compounds are covered in Chapter 3.05 and will not be discussed here. Simple boryl adducts have been reported from the reaction of Na2Fe(CO)4 and ClBCat" (Cat = catecholate or a Bu-substituted derivative. Equation (8)). The same products can be obtained upon irradiating Fe(CO)s and Cat B-BCat" in toluene at 0°C. Reaction of the diboryl 6 with 1 equiv. of lithium bis(trimethylsilyl)amide in toluene solvent leads to removal of one boryl unit and the formation of an anionic iron boryl complex (Equation (9)). The anionic species can also be obtained by stoichiometric addition of the ClBCat complex to Na2Fe(CO)4. Reaction of [Fe(CO)4 B(3,5-/-Bu2-Cat) ] with ClSnMes gives the stannylated derivative Fe(CO)4 B(3,5-/-Bu2-Cat) (SnMe3). 

The resonance between 55 and 56 (R = H, alkyl, aryl, ferrocenyl) in ferrocenyl-methyl cations including the diferrocenylmethyl cation has been used by Cais to explain the similar bending of the exocyclic C,C bonds toward the iron atom (Scheme 10.20) [65].Thefieldhas recently been reviewedbyGleiteref a/. [62],who included related isoelectronic boryl substituted systems. Wagner et al. [66] have prepared compounds of this type, and the authors proposed attractive interactions between the iron and boron atoms, because the C-B bonds are bent toward the iron atom. The analogy does not only apply to ferrocenes but also to isoelectronic (cyclobutadiene)(cyclopentadienyl)cobalt complexes and other related compounds [62]. 

He X, Hartwig JF. Boryls bound to iron carbonyl. Stmcture of a rare bis(boryl) complex, synthesis of the first anionic boryl, and reaction chemistry that includes the synthetic equivalent of horyl anion transfer. Organometallics. 1996 15 400-407. 

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