Simon Aldridge

The coordination chemistry of boryl and borate substituted cyclopentadienyl ligands

Abstract In this article a summary is given of developments in the synthetic, structural and reaction chemistry of complexes containing boryl- and borate-substituted cyclopentadienyl ligands [(η 5 -C 5 R 4 BX 2 ) − and (η 5 -C 5 R 4 BX 3 ) 2− ].

Carbonyl analogues? Analysis of Fe–E (E = B, Al, Ga) bonding in cationic terminal diyl complexes by density functional theory

A series of DFT calculations has been carried out with the aim of characterizing the metal-group 13 element interaction in the novel cationic borylene complex [(eta5-C2Me5)Fe(CO)2(BMes)]+ (1) and related species of the type [eta5-C5R5)M(L)2(EX)]n+. In addition, comparisons have been made with charge neutral borylene complexes and with related group 14 based ligand systems (e.g. cationic metal carbonyls, carbenes and vinylidenes) for which models of bonding have previously been established. In this regard particular attention has been focused on the interpretation of (i) molecular orbital composition; (ii) bond dissociation energies (BDEs) and the ratio of ionic to covalent contributions (DeltaEelstat/DeltaEorb); and (iii) sigma and pi symmetry covalent contributions. The molecular orbital compositions for the prototype borylene complex 1 and for related cationic and neutral systems [e.g.[(eta5-C5H5)Fe(PMe3)2(BMes)]+ and (eta5-C5H5)Mn(CO2(BMes)]] are consistent with the presence of bonding interactions between metal and borylene fragments of both sigma and pi symmetry. Furthermore, on the basis of BDEs, DeltaEorb values and sigma/pi covalent ratios, the bonding in cationic terminal borylene complexes such as 1 appears to have as much right to be termed a M=E double bond as does that in archetypal Fischer carbene and related complexes such as [(eta5-C5R5)Fe(CO)2(CCMe2)]+ and [(eta5-C5R5)Fe(CO)2(CH2)]+.

Synthetic and reaction chemistry of heteroatom stabilized boryl and cationic borylene complexes

The synthesis, spectroscopic and structural characterization of the aryloxy and amino functionalized chloroboryl complexes (eta(5)-C(5)R(5))Fe(CO)(2)B(OMes)Cl (R = H, 2a ; R = Me, 3a) and (eta(5)-C(5)H(5))Fe(CO)(2)B(N(i)Pr(2))Cl (7a) are reported. Compound 2ais shown to be a versatile substrate for further boron-centred substitution chemistry leading to the asymmetric boryl complexes (eta(5)-C(5)H(5))Fe(CO)(2)B(OMes)ER(n) [ER(n) = OC(6)H(4)(t)Bu-4, 2c; ER(n) = SPh, 2d] with retention of the metal-boron bond. The reactivities of 2a, 3a and 7a towards the halide abstraction agent Na[BAr(f)(4)] have also been examined, in order to investigate the potential for the generation of cationic heteroatom-stabilized terminal borylene complexes. The application of this methodology to the mesityloxy derivatives and gives rise to B-F containing products, presumably via fluoride abstraction from the [BAr(f)(4)](-) counter-ion. By contrast, amino-functionalized complex 7a is more amenable to this approach, and the thermally robust terminal aminoborylene complex [(eta(5)-C(5)H(5))Fe(CO)(2)B(N(i)Pr(2))][BAr(f)(4)] (9) can be isolated in ca. 50% yield. The reactivity of 9towards a range of nucleophilic and/or unsaturated reagents has been examined, with examples of addition, protonolysis and metathesis chemistries having been established.

Synthesis and reactivity of transition metal complexes containing halogenated boryl ligands

The synthesis and characterization of iron and manganese complexes containing the tetrachlorocatecholboryl (BO2C6Cl4) ligand are reported. Crystallographic study of the methylcyclopentadienyl derivative (eta(5)-C5H4Me)Fe(CO)(2)BO2C6Cl4 allows comparison of structure and bonding with related complexes of the type (eta(5)-C5R5)Fe(CO)(2)B(OR)(2) and reveals that the relative orientation of (eta(5)-C5H4Me)Fe(CO)(2) and BO2C6Cl4 moieties is influenced by intramolecular C---H...O hydrogen bonding. Additionally, an alternative route to catecholboryl complexes from dilithiocatechol is reported.

Fe–Ga multiple bonding? Synthesis, spectroscopic and structural characterization of a transition metal complex containing a cationic two-coordinate gallium centre

This communication reports the synthesis and characterization of the cationic iron complex [((eta5-C5Me5)Fe(CO)2))2Ga]+[BAr(f)4]- [Ar(f) = C6H3(CF3)2-3,5] containing a symmetrically bridging two-coordinate gallium atom and a delocalised Fe-Ga-Fe pi system incorporating partial Fe-Ga multiple bond character.

Intramolecular base-stabilised adducts of main group halides

The coordination chemistry of alkoxo and amido ligands bearing pendant nitrogen or sulfur donors has been developed to include examples of main group complexes. The structural implications of amido ligand coordination augmented by a tethered pyridyl base have been investigated for group 13 and 14 derivatives {[6-(Me3SiN)-2-Me-C5H3N]SnCl3 and [6-(Me3SiN)-2-Me-C5H3N]BBr2}. Furthermore, the scope, kinetics and mechanism of the synthesis of alkoxo and amido derivatives from trimethylsilyl substituted precursors have been investigated in depth. The methodology is found to be applicable to a range of ligand frameworks of varying flexibility, stabilised by one or two “tether” arms.

Reactions of a phosphavinyl Grignard reagent with main group mono-halide compounds

Abstract The reactions of a phosphavinyl Grignard reagent, [CyPC(But)MgCl(OEt2)] Cy=cyclohexyl, with a variety of main group 13, 14 and 16 mono-halide compounds have been investigated. When the Grignard reagent is reacted with bromocatecholborane the terminal phosphavinyl complex, [(C6H4O2)B{C(But)PCy}], is formed. Related terminal phosphavinyl tin and gallium complexes, [R3Sn{C(But)PCy}], R=Me or Bun and [IGa{C(But)PCy}2], have been prepared by similar routes. The reaction of the Grignard reagent with PhSeCl has afforded a new λ5,λ5-diphosphete, [{(But)CP(Cy)(SePh)}2], the mechanism of formation of which is discussed. The preparation of a phosphavinyl selenium compound, [(C8H4O2N)PC(But)(SePh)], is also described. All compounds have been spectroscopically characterised and several have been crystallographically authenticated.

Migratory insertion of [B(C6F5)2] into C–H bonds: CO promoted transfer of the boryl fragment

The reaction of (eta(5)-C5H5)Fe(CO)2B(C6F5)2 with CO has been shown to proceed via ligand substitution at the metal with accompanying transfer of the boryl fragment (via C-H insertion) to the Cp ring, thereby generating the zwitterion [eta(5)-C5H4B(C6F5)2H]Fe(CO)3 in quantitative yield.

Hydro­gen‐bonding motifs in the solid‐state structure of ferroceneboronic acid

At 180 K, the crystal structure of ferroceneboronic acid, [Fe(C5H5)(C5H6BO2)], consists of centrosymmetric [FcB(OH)2]2 dimers [Fc is (η5-C5H5)Fe(η5-C5H4)], formed by a pair of complementary O—H⋯O hydrogen-bonding interactions [O⋯H 1.97 A and O⋯O 2.806 (3) A]. The remaining two O-bound H atoms per [FcB(OH)2]2 moiety serve to link the dimeric units to adjacent dimers in a criss-cross fashion, very similar to that between hydrogen-bonded chains in solid Fe[η5-C5H4B(OH)2]2.

[(η5-C5H5)Fe(CO)2]2B(2,4,6-Me3C6H2): synthesis, spectroscopic and structural characterization of a transition metal complex containing an unsupported bridging borylene ligand

The synthesis and characterisation of the dinuclear iron complex [(eta 5-C5H5)Fe(CO)2]2B(2,4,6-Me3C6H2) containing an unsupported bridging borylene ligand are reported.