Transition series complexes

All other considerations aside, transition metal complex spectra should contain only bands of the same multiplicity as that of the ground term. In practice, certainly the dominant bands in the spectra are of that type, but bands of intensity some 102 or 103 times lower are present, usually restricted to those corresponding to AS = 1 relative to the ground term, in the first transition series complexes. 

Wight C A and Armentrout P B 1993 Laser photoionization probes of ligand-binding effects in multiphoton dissociation of gas-phase transition-metal complexes ACS Symposium Series 530 61-74... 

The preparation of a series of transition metal complexes (Co. Ni. Pd. Pt, Ir. Au. Cu. Ag) with ambident anion (70) and phosphines as ligands has been reported recently (885). According to the infrared and NMR spectra the thiazoline-2-thione anion is bounded through the exocyclic sulfur atom to the metal. The copper and silver complexes have been found to be dimeric. 

Compared to later elements in their respective transition series, scandium, yttrium and lanthanum have rather poorly developed coordination chemistries and form weaker coordinate bonds, lanthanum generally being even less inclined to form strong coordinate bonds than scandium. This is reflected in the stability constants of a number of relevant 1 1 metal-edta complexes ... 

Pyridine 1-oxide, like pyridine, can act as a ligand in transition metal complexes, but unfortunately good stability constants are not known. However, Shupack and Orchin have found that the C===C stretching frequency of the ethylene ligand in trans-ethylene pyridine 1-oxide dichloroplatinum(II) varies linearly with the pA and hence with the C7-value (ct+ or a, respectively) of substituents in the pyridine oxide. The data for the above reaction series are included in Table V. 

Complex ions are commonly formed by transition metals, particularly those toward die right of a transition series (MCr — 3oZn in the first transition series). Nontransition metals, including Al, Sn, and Pb, form a more limited number of stable complex ions. 

The electronic spectra of the hexafluoro-complexes of the first row transition series. G. C. Allen and K. D. Warren, Struct. Bonding (Berlin), 1971, 9, 50-138 (137). 

Interactions between non-halogen-containing IIIB compounds and transition-metal complexes are found in 6.5.3. Most of these IIIB compounds are boron-containing heterocycles. A series of interesting sandwich compounds, including triple- and tetradecked complexes, are synthesized by methods in 6.5.2.1-6.5.3. 

The six-membered 1,4-diborines (1,4-diaboracyclohexadienes) are prepared by cocondensing alkynes with monomeric BF or by the tin route . They form a series of transition-metal complexes VIII-XIV by reaction with various complex... 

Allen GC, Warren KD (1971) The Electronic Spectra of the Hexafluoro Complexes of the First Transition Series. 9 49-138... 

Allen GC, Warren KD (1974) The Electronic Spectra of the Hexafluoro Complexes of the Second and Third Transition Series. 19 105-165 Alonso JA, Baibas LC (1993) Hardness of Metallic Clusters. 80 229-258 Alonso JA, Baibas LC (1987) Simple Density Functional Theory of the Electronegativity and Other Related Properties of Atoms and Ions. 66 41-78 Andersson LA, Dawson JH (1991) EXAFS Spectroscopy of Heme-Containing Oxygenases and Peroxidases. 74 1-40 Antanaitis BC, see Doi K (1988) 70 1-26... 

Zeijden [112] used chiral M-functionalized cyclopentadiene ligands to prepare a series of transition metal complexes. The zirconium derivative (82 in Scheme 46), as a moderate Lewis acid, catalyzed the Diels-Alder reaction between methacroleine and cyclopentadiene, with 72% de but no measurable enantiomeric excess. Nakagawa [113] reported l,T-(2,2 -bis-acylamino)binaphthalene (83 in Scheme 46) to be effective in the ytterbium-catalyzed asymmetric Diels-Alder reaction between cyclopentadiene and crotonyl-l,3-oxazolidin-2-one. The adduct was obtained with high yield and enantioselectivity (97% yield, endo/exo = 91/9, > 98% ee for the endo adduct). The addition of diisopropylethylamine was necessary to afford high enantioselectivities, since without this additive, the product was essentially... 

Table 1.3 contains values for two 3d cases. At KsCuFg, ATreplirreg) contributes about 40% of the total stabilization, but at Ni (aq) only 15%. This is because in the first transition series, the nephelauxetic effect increases substantially when the oxidation state increases from -i-2 to -e3. The relatively small contribution for the M (aq) ion explains why text books use this example to explain the double bowl shapes AErep(irreg) is almost exactly cancelled by the sum of AEso and ATrix, so the total stabilization is nearly equal to the orbital stabilization energy. In most other cases, A rep(irreg) is much more important and may play an important role in sustaining the Irving-WilUams rule in complex-ing reactions [32, 33]. 

Abstract Over the past decade significant advances have been made in the fields of polymerisation, oligomerisation and telomerisation with metal-NHC catalysts. Complexes from across the transition series, as well as lanthanide examples, have been employed as catalysts for these reactions. Recent developments in the use of metal-NHC complexes in a-olefin polymerisation and oligomerisation, CO/olefm copolymerisation, atom-transfer radical polymerisation (ATRP) and diene telomerisation are discnssed in subsequent sections. 

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