J. Appl. Cryst.の発刊に際して

N-Heterocyclic Carbenes in Late Transition Metal Catalysis

The chemistry of heterocyclic carbenes has experienced a rapid development over the last years. In addition to the imidazolin-2-ylidenes, a large number of cyclic diaminocarbenes with different ring sizes have been described. Aside from diaminocarbenes, P-heterocyclic carbenes, and derivatives with only one, or even no heteroatom within the carbene ring are known. New methods for the synthesis of complexes with N-heterocyclic carbene ligands such as the oxidative addition or the metal atom template controlled cyclization of β-functionalized isocyanides have been developed recently. This review summarizes the new developments regarding the synthesis of N-heterocyclic carbenes and their metal complexes.

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

Linear and Nonlinear Optical Properties of Photochromic Molecules and Materials.

Damascene copper electroplating for on-chip interconnections, a process that we conceived and developed in the early 1990s, makes it possible to fill submicron trenches and vias with copper without creating a void or a seam and has thus proven superior to other technologies of copper deposition. We discuss here the relationship of additives in the plating bath to superfilling, the phenomenon that results in superconformal coverage, and we present a numerical model which accounts for the experimentally observed profile evolution of the plated metal.

Damascene copper electroplating for chip interconnections

Metal complexes with ‘pincer’-type ligands incorporating N-heterocyclic carbene functionalities

A version of the CNDO/S method has been re-parametrized by correlating computed and measured dipole moments and transition wavelengths for a range of organic conjugated molecules. The method has then been used to calculate the hyperpolarizability tensor, βijk, in the form related to second-harmonic generation, for an extended set of molecules of similar type. A good correlation between theory and experiment has been found. The convergence of the excited-state perturbation expansion used in the calculation of the tensor has been extensively investigated.

Calculation of the second-order electronic polarizabilities of some organic molecules. Part 1

The calculated hyperpolarisabilities of the symmetrical polyphenyls, containing an electron-donating dimethylamino group and an electron-attracting nitro group positioned at opposite ends of the conjugated system, slowly increase with an increasing number of phenyl units, but the effect per unit volume is a maximum for 4-dimethylamino-4′-nitroterphenyl. In contrast, the calculated values for polyenes containing the same donor and attractor increase rapidly with an increasing number of ethenyl units, and the effect per unit volume is a maximum for 20 units. Overall, the polyene system shows an effect which is at least 20 times that of the polyphenyl system and 10 times that of any other known system. A similar effect is also found in the dimethylaminopolyenals, though a comparison between calculated and experimental dipole moments and electronic transition energies suggests that their hyperpolarisabilities may be somewhat overestimated at the CNDO level of approximation.

Non-linear optical properties of organic molecules. Part 2. Effect of conjugation length and molecular volume on the calculated hyperpolarisabilities of polyphenyls and polyenes

The complexes [(C–N–C)MXn(thf)m] with the ‘pincer’ 2,6-bis(imidazolylidene)pyridine, (C–N–C) = 2,6-bis(arylimidazol-2-ylidene)pyridine, aryl = 2,6-Pri2C6H3, M = V, X = Cl, n = 2, m = 1 1a; M = Cr, X = Cl, n = 2, m = 0, 2a, X = Br, 2b; M = Mn, X = Br, n = 2, m = 0, 3; M = Nb, X = Cl, n = 3, m = 0, 4; and M = U, X = Cl, n = 4, m = 0, 5, were synthesised by (a) substitution of labile tmed (1a), thf (2a, 3, 5) or dme (4) by free (C–N–C) or by (b) reaction of the bisimidazolium salt (CH–N–CH)Br2 with {Cr[N(SiMe3)2]2(thf)2} followed by amine elimination (2b). Attempted alkylation of 1a, 2, 3a and 4 with Grignard or alkyl lithiums gave intractable mixtures, and in one case [reaction of 1a with (mesityl)MgBr] resulted in exchange of Cl by Br (1b). Oxidation of 1a or [(C–N–C)VCl3] with 4-methylmorpholine N-oxide afforded the trans-V(C–N–C)(O)Cl2, 6, which by reaction with AgBF4 in MeCN gave trans-[V(C–N–C)(O)(MeCN)2][BF4]2, 7. Reaction of 1a with p-tolyl azide gave trans-V(C–N–C)(N-p-tolyl)Cl28. The complex trans-Ti(C–N–C)(NBut)Cl2, 9, was prepared by substitution of the pyridine ligands in Ti(NBut)Cl2(py)3 by C–N–C.

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David Pugh

Papers

Metal complexes with ‘pincer’-type ligands incorporating N-heterocyclic carbene functionalities

Calculation of the second-order electronic polarizabilities of some organic molecules. Part 1

Non-linear optical properties of organic molecules. Part 2. Effect of conjugation length and molecular volume on the calculated hyperpolarisabilities of polyphenyls and polyenes

‘Pincer’ dicarbene complexes of some early transition metals and uranium

Indenyl- and Fluorenyl-Functionalized N-Heterocyclic Carbene Complexes of Titanium, Zirconium, Vanadium, Chromium, and Yttrium