Mono transition metals

Co2 +-Substitution at the addenda atoms gives catalysts for the epoxidation of olefins in the presence of aldehyde [293). PWM-Co is the most active among the mono-transition-metal-substituted polyanions the order of activity is PWn-Co > -Mn 2= -Fe 2= -Cu > -Ni. Here, PWll(M + )0(379", ) (M = Co2 +, Cu2+, Fe3 +, Ni2 +, Mn2 + ) is denoted by PWn M. The same order was observed for the oxidation of isobutyraldehyde, suggesting that the oxidation of aldehyde to give peracid is an important step in the reaction. It has been reported that substitution of V5+ for Mo6+ in PMo O3 gives a good catalyst for epoxidation and the Baeyer-Villiger reaction [294). 

A. Mono-Transition-Metal-Ion-Substituted Heteropolyanions as Inorganic Synzymes... 

The synthesis involves the nickel-catalyzed coupling of the mono-Grignard reagent derived from 3-alkyl-2,5-diiodothiophene (82,83). Also in that year, transition-metal hahdes, ie, FeCl, MoCl, and RuCl, were used for the chemical oxidative polymerization of 3-substituted thiophenes (84). Substantial decreases in conductivity were noted when branched side chains were present in the polymer stmcture (85). 

Returning briefly to CO2 as a ligand in addition to the various mono-C02 complexes referred to above, several bis(rj -CO2) transition-metal adducts are known, e.g. /ran -[Mo( ) -C02)2(PMe3)4] (5) and trans.mer-[Mo( 2-C02)2(PMc3)3(CNPr )].< 22 The first homo-bimetallic bridging-C02 complex has also been structurally characterized by X-ray analysis, viz. [(dppp)(CO)2Re(/x, j 0,0 j C)Re(CO)3(dppp)] (6) [dppp = l,3-bis(diphenyl-phosphino)propanc]. 0 3)... 

Inhibitors (Section 5.3), including transition metal complexes and nilroxides, may be used to prepare mono-end-functional polymers. If an appropriate initiator is employed, di-end-functional polymers are also possible. 

The scope of the present paper is limited to those cyclopentadienyl ligands that contain more than two bulky substituents and transition metal complexes derived thereof in order to be able to focus on the specific effects of these ligand systems. A selection of some mono-substituted cyclopentadienyl ligands will be treated also. Among the numerous reviews highlighting special aspects of cyclopentadienyl... 

Titanium imido complexes supported by amidinate ligands form an interesting and well-investigated class of early transition metal amidinato complexes. Metathetical reactions between the readily accessible titanium imide precursors Ti( = NR)Cl2(py)3 with lithium amidinates according to Scheme 84 afforded either terminal or bridging imido complexes depending on the steiic bulk of the amidinate anion. In solution, the mononuclear bis(pyridine) adducts exist in temperature-dependent, dynamic equilibrium with their mono(pyiidine) homologs and free pyridine. 

Anions of transition-metal carbonyls are prepared by reducing the carbonyl and react with derivatives of group-IIB metals to yield mono-, di- and even trisubstituted derivatives ... 

Application of small metal particles has attracted the attention of the scientists for a long time. As early as in the seventies Turkevich already prepared mono-dispersed gold particles [19], and later, using molecular transition metal carbonyl clusters [20], the importance of small nanoparticles increased considerably. One of the crucial points is whether turnover frequency measured for a given catalytic reaction increases or decreases as the particle size is diminished. 

Nilekar AU, Mavrikakis M. 2008. Improved oxygen reduction reactivity of platinum mono-layers on transition metal surfaces. Surf Sci 602 L89-L94. 

Figure 27 Oxidative addition of the organochalcogen compounds to low-valent transition metal centers most often resulting in the cleavage of the chalcogen-chalcogen bond and the formation of mono- or dinuclear complexes with anionic bridging or terminal RE- (E = Se, Te) ligands.

Well-characterized transition metal complexes of vitamin C (ascorbic acid) are rare, and a select number of these exhibit anticancer properties. Hollis et al. have described the first examples to be fully characterized by X-ray crystallography.316 Treatment of [Pt(H20)2L2]2+ (L = NH3, MeNH2 L2 = en, 1,2-chxn) with ascorbic acid gives either the mono- or bisascorbate species of the type cis-[PtL2(C2,Os-ascorbate)] (e.g., (125)) or m-[PtL2(C2-ascorbate)(03-ascorbate)], respectively. Interestingly, in both types of complexes, platinum(II) forms a bond with the C-2 atom of ascorbic... 

The 1 2 complex of Hg2+ with the tacn derivative mono-N-(4-vinylbenzyl)-l,4,7-triazacyclono-nane copolymerizes with p-divinylbenzene to give an Hg-templated polymer which, after deme-talation with 6N HC1, is a highly selective gathering material for Hg2+ in competition with other transition metals like Cd2+, Ag+, Pb2+, Cu, and Fe3+ at low pH values.211... 

Electron-rich olefins such as 36 have been used by Lappert in the synthesis of a great number of mono-, bis-, tris-, and tetrakiscarbene complexes from various transition metal species (62). Ru, Os, and Ir carbene complexes have been prepared from reactions with these olefins, e.g.,... 

In contrast to the vast number of mono- and multinuclear binary carbonyl complexes of the transition metals, no isolable binary carbonyls of titanium, zirconium, or hafnium have been reported. 

The participation of cations in redox reactions of metal hexacyanoferrates provides a unique opportunity for the development of chemical sensors for non-electroactive ions. The development of sensors for thallium (Tl+) [15], cesium (Cs+) [34], and potassium (K+) [35, 36] pioneered analytical applications of metal hexacyanoferrates (Table 13.1). Later, a number of cationic analytes were enlarged, including ammonium (NH4+) [37], rubidium (Rb+) [38], and even other mono- and divalent cations [39], In most cases the electrochemical techniques used were potentiometry and amperometry either under constant potential or in cyclic voltammetric regime. More recently, sensors for silver [29] and arsenite [40] on the basis of transition metal hexacyanoferrates were proposed. An apparent list of sensors for non-electroactive ions is presented in Table 13.1. 

One of the most interesting organometallic compounds of a transition metal is ferrocene (see Chapter 21). Butyllithium reacts with ferrocene to produce the mono and dilithiated compounds that have the following structures ... 

---