Roderick D. Cannon

Vibrational spectra of carboxylato complexes—III. Trinuclear ‘basic’ acetates and formates of chromium(III), iron(III) and other transition metals

Abstract The i.r. and Raman spectra of a series of complexes [M III 3 O(OOCR) 6 L 3 ]X· x H 2 O (M = Cr, Fe, Mn, Ru, Rh; L = H 2 O, pyridine, γ-picoline; X = Cl, Br, I, NO 3 , ClO 3 , ClO 4 , BF 4 ) have been analysed in detail. The vibrational modes of the central M 3 O and the three surrounding MO 4 units, are identified. The metal—nitrogen stretching vibrations and the MOH 2 modes are assigned. The ‘basic’ chromium(III) formate is shown to be [Cr 3 O(OOCH) 6 (OH 2 ) 2 (OOCH)] x H 2 O, containing monodentate, inner-sphere coordinated formate ion. The use of the symmetric and asymmetric OCO stretching frequencies in characterizing bridging carboxylate ions is discussed.

Solvent effects on intervalence charge transfer

Abstract The solvent reorganisation energies associated with charge transfer spectroscopic transitions in molecules of ellipsoidal shape are calculated by a novel adaptation of the Kirkwood-Westheimer equations, and compared with experimental data for (i) mixed-valence ruthenium(II)-ruthenium(III), complexes, and (ii) outer-sphere rutheium(III)-halide complexes.

Vibrational spectra of carboxylato complexes—I. Infrared and Raman spectra of beryllium(II) acetate and formate and of zinc(II) acetate and zinc(II) acetate dihydrate

Abstract The spectra of the title compounds have been recorded and interpreted. On this basis, the structures of the anhydrous compounds Be(OOCH) 2 , Be(OOCMe) 2 , Zn(OOCMe) 2 are predicted to have tetrahedral coordination with the carboxylate ions acting as bidentate ligands.

Vibrational spectra of carboxylato complexes—V. Vibrations of the bridging oxide ion in the trinuclear complex [Fe3O(OOCCH3)6(C5H5N)3]+

Abstract By isotopic substitution in the salt [Fe3O(OOCCH3)6(py)3] [FeCl4], the in-plane asymmetric vibration νas(Fe3O)and the out-of-plane vibration δs(Fe3O)have been identified at 600 cm−1 and 300 cm−1, respectively.

Vibrational spectra of carboxylato complexes—IV. Mixed-metal and mixed-valence oxo-trinuclear complexes

Abstract Infrared spectra of mixed-metal complexes [Cr 3- n Fe n O(OOCR) 6 L] + ( n = 1,2; R = H, CH 3 ; L = H 2 O, γ-picoline, pyridine), and of mixed-valence complexes [Fe III 2 Fe II O(OOCCH 3 ) 6 py 3 ], [Ru III 2 Ru II O(OOCCH 3 ) 6 L 3 ] (L = H 2 O, P(C 6 H 5 ) 3 ) are reported and compared with analogous symmetrical (Cr III ) 3 , (Fe III ) 3 and (Ru III ) 3 species. The effects of lowered symmetry are seen in the mixed-metal but not in the mixed-valence complexes.

Synthesis of ferrocene-based redox-active polymers via palladium-catalysed coupling reactions

Abstract 1,1′-Difunctionalised ferrocenes Fe(C 5 H 4 Z) 2 [Z = 4-BrC 6 H 4 ( 1 ), 4-BrC 6 H 4 CH 2 C(O)- ( 4a ), 4-BrC 6 H 4 CH=CH- ( 6a )] undergo cross-coupling reactions with the dizinc reagent (ClZnC 6 H 4 ) 2 COCH 2 CHC(Me)O ( 2 ) to give a series of conjugated and non-conjugated aromatic poly(ferrocenes) with ferrocenediyl moieties as part of the polymer backbone. Similar products are obtained by Heck-arylation of 1,1′-divinylferrocene with diiodoarenes I-R-I (R = 1,4-C 6 H 4 , 1,1′-C 6 H 4 -C 6 H 4 , 2,5-C 4 H 2 S, 1,1′-C 6 H 4 OC 6 H 4 ). The coupling products form orange to deep red solids, which are poorly soluble and oligometric in most cases. Cyclic voltammetry measurements in dichloromethane solution give redox potentials close to the parent ferrocenes, with apparently very little interaction between the widely spaced iron centres.

Vibrational spectra of carboxylato complexes—VI. Isotopic substitution in the mixed-metal trinuclear complexes [FeIII2NiIIO(OOCCH3)6L3]

Abstract Infrared and Raman spectra of the complexes [Fe III 2 Ni II O(OOCCH 3 ) 6 L 3 ], L = C 5 H 5 N and H 2 O, are reported. Assignments in the region 800 to 200 cm −1 are made on the basis of substitution of 18 O for 16 O (central oxygen) and deuteration. In particular, the two components of the in-plane asymmetric vibration ν as (Fe 2 NiO) are identified at 722 and 565 cm −1 .

Vibrational spectra of carboxylato complexes—II. Some oxo-tetranuclear complexes ☆

Abstract The i.r. and Raman spectra of the compounds Be 4 O(OOCCH 3 ) 6 , Be 4 O(OOCCD 3 ) 6 , Be 4 O(OOCH) 6 and Zn 4 O(OOCCH 3 ) 6 have been analysed and assigned in detail. In particular, the vibrational modes of the O(MO 3 ) 4 subunits, and their interactions with the carboxylate ligand vibrations, have been identified. The compound Zn 4 O(OOCC 2 H 5 ) 6 has the same oxo-centred structure as the others.

Exchange interactions in trinuclear basic chromium(III) clusters : direct observation of the magnetic spectrum by inelastic neutron scattering

Incoherent inelastic neutron scattering spectra are reported for salts of the complex [Cr3O(OOCCH3)6(OH2)3]+. The data are consistent with predominantly antiferromagnetic coupling between pairs of chromium ions. The complete spectrum of transitions between successive states with total spin S=1/2, 3/2, 5/2, 7/2, and 9/2 has been observed for the first time. Splittings of the ground state S=1/2 have been observed directly and attributed to lowering of symmetry of the triangular cluster. For the chloride salt the data confirm that two sets of complex cations with different degrees of symmetry lowering are present in the crystal, at least at the lowest temperatures used (T=1.4 to 50 K). In principle, the relationship of J values for the symmetry‐lowered case could be described as ‘‘isosceles,’’ with Jab≳Jbc=Jac or Jab<Jbc=Jac; or as ‘‘scalene,’’ with all three J values different. We find that, for at least one of the two sets of metal ion clusters, the scalene case applies, with J values of −11.5±0.2, −10.5±0...

Kinetic and mechanism of alkene polymerization

Triphenylmethyl salts of the very weakly-coordinating borate anions [CN{B(C6F5)3}2]− (1), [H2N{(C6F5)3}2]− and [M{CNB(C6F5)3}4]2− (M = Ni, Pd) have been prepared in simple one-pot reactions. Mixtures of (SBI)ZrMe2/1/AlBu3i (SBI = rac-Me2Si(Ind)2) are 30–40 times more active in ethylene polymerizations at 60–100°C than (SBI)ZrCl2/MAO. The quantification of anion effects on propene polymerization activity at 20°C gives the order [CN{B(C6F5)3}2]− > [H2N{(C6F5)3}2]− ≈ B(C6F5)4− ≫ [MeB(C6F5)3]−. The highest productivities were of the order of ca. 3.0 × 108 g PP (mol Zr)−1 h−1 [C3H6]−1, about 1.3–1.5 times higher than with B(C6F5)4− as the counter anion. The titanium system CGCTiMe2/1/AlBu3i gave activities that were very similar to the zirconocene catalyst. The concentration of active species [C*] as determined by quenched-flow kinetic techniques indicates typical values of around 10%, independent of the counter anion, for both the borate and MAO systems. Pulsed field-gradient spin echo and nuclear Overhauser effect NMR experiments on systems designed to be more realistic models for active species with longer polymeryl chains, (SBI)M(CH2SiMe3)(μ-Me)B(C6F5)3 and [(SBI)MCH2SiMe3+...B(C6F5)4−] (M = Zr, Hf), demonstrated the influence of bulky alkyl chains on the ion pair solution structures: while the MeB(C6F5)3 compound exists as a simple inner-sphere ion-pair, the B(C6F5)4− compound is an outer-sphere ion pair (OSIP), a consequence of the relegation of the anion into the second coordination sphere by the γ-agostic interaction with the alkyl ligand. The OSIP aggregates to ion hextuples (10 mM) or quadruples (2 mM). Implications for the polymerization mechanism are discussed; the process follows an associative interchange (Ia) pathway.