Group 12 metals Dialkyl derivatives

Secondary amines synthesized by catalytic reductive alkylation of primary amines are used in a variety of fine and specialty chemical indnstries. For example, derivatives of cyclohexylamine are used as corrosion inhibitors, N-(l,3-dimethylbntyl)-N -phenyl-p-phenylenediamine (6-PPD) is nsed as an anti-oxidant in rabber indnstiy, several dialkylated diamines are used in the coatings indnstiy, while they are nsed in the pharmacentical industry as pharmacophores (1-7). Harold Greenfield and co-workers have examined the ability of platinum group metals (PGM), base metals, and their snlfides to catalyze rednctive alkylation of primary and secotrdary amines (8-11). They found that different catalysts are optimal for the... 

Dialkyl derivatives of elements of the Second sub-Group, namely, zinc, cadmium, and mercury, contain an almost completely covalent metal-carbon bond. These compounds are normal, unassociated liquids with low boiling points e.g., the dimethyl derivative of zinc boils at 46°, that of cadmium at 105.5°, and that of mercury at 92°. 

When the preparation of alkali metal enolates derived from alkanoylphosphonates was attempted by treatment with strong anhydrous bases such as lithium diisopropylamide or sodium hydride, the formation of phosphate phosphonate-type products was observed. This was interpreted in terms of fragmentation of the enolate formed in the first step to ketene and dialkyl phosphite anion (equation 75), and addition of the latter to the carbonyl group of an unreacted acylphosphonate molecules to form a bisphosphonate. Such molecules are known to rearrange to phosphate phosphonates ... 

Structure and bonding in the gaseous dihalides and dialkyl derivatives of the Group 2 and Group 12 metals... 

The gas phase structures of the dimethylderivatives M(CH3)2, M = Be, Zn, Cd or Hg and of bis(neo-pentyl)magnesium have been determined by gas electron diffraction. All have valence angles of 180 at the metal atom. The dialkyl derivatives of the Group 12 metals are volatile liquids and are believed to be monomeric in the crystalline phase. Dimethylberyl-lium and bis(neo-pentyl)-magnesium are solid at room temperature. The crystal structure of dimethylberyllium will be discussed in Chapter 12. 

Solvent extraction is proposed as a suitable method for PGMs (platinum group metals) recovery from low concentrated sources. Several extractants have been studied and proposed, e.g., hydroxyoximes, alkyl derivatives of 8-hydroxyquinoline, dialkyl sulphides, hydrophobic amines and quaternary ammonium salts, derivatives of pyridine and pyridinecarboxamides. However, the problems of a slow extraction rate or low metal separation remain to be solved. Looking for extractants permitting possibly fastest extraction of Pd, two phosphonium ionic liquids, i.e., [QP][C1] and [QP][Bis], have been used (Cieszynska et al., 2007 Cieszynska, 2010 Cieszynska Wisniewski, 2010, 2011). To overcome problems caused by the high viscosity of ILs, the mixtures with toluene have been used for extraction, similarly as for extraction of Zrf+. 

Dialkyl peroxides have the stmctural formula R—OO—R/ where R and R are the same or different primary, secondary, or tertiary alkyl, cycloalkyl, and aralkyl hydrocarbon or hetero-substituted hydrocarbon radicals. Organomineral peroxides have the formulas R Q(OOR) and R QOOQR, where at least one of the peroxygens is bonded directly to the organo-substituted metal or metalloid, Q. Dialkyl peroxides include cyclic and bicycflc peroxides where the R and R groups are linked, eg, endoperoxides and derivatives of 1,2-dioxane. Also included are polymeric peroxides, which usually are called poly(alkylene peroxides) or alkylene—oxygen copolymers, and poly(organomineral peroxides) (44), where Q = As or Sb. 

Alkyl and aryl derivatives of poly(dichlorophosphazene) are not efficiently synthesized by nucleophilic reaction of LXXXIV with metal alkyls or aryls. The halogen substitution reaction occurs but is accompanied by polymer chain cleavage. Use of poly(difluorophosphazene) or introduction of aryl and alkyl groups at the monomer stage offer some improvement, but neither method is fully satisfactory. The best route to alkyl and aryl derivatives is polymerization of A-(trimethylsilyl)-/).P-dialkyl-.P-halophosphoranimines at moderate temperatures (25-60°C) in the presence of a Lewis acid [Allcock et al., 1996, 2000, 2001a,b Neilson and Wisian-Neilson, 1988]. The reaction proceeds as a cationic chain polymerization ... 

Imaizumi et al. studied the hydrogenation of l,4-dialkyl-l,3-cyclohexadienes over the nine group VIII (groups 8-10) metals and copper in ethanol at room temperature and atmospheric pressure.122 The selectivity for monoenes formation at 50% conversion increased in the order Os-C, Ir-C < Ru-C, Rh-C, Pt < Pd-C, Raney Fe, Raney Co, Raney Ni, Raney Cu (= 100%). The selectivity for 1,4-addition product increased in the order Os-C, Ir-C < Ru-C, Rh-C, Raney Cu, Raney Fe, Raney Ni < Raney Co, Pd-C, Pt. Extensive formation of 1,4-dialkylbenzenes (more than 50% with the 1,3-dimethyl derivative) was observed over Raney Ni and Pd-C, while they were not formed over Raney Cu, Os-C, and Ir-C. In the hydrogenation of 4-methyl-1,3-pen -tadiene (39) (Scheme 3.15) over group VIII metals in cyclohexane at room temperature and atmospheric pressure, high selectivity to monoenes was obtained with iron, nickel, cobalt, and palladium catalysts where the amounts of the saturate 2-methylpen-... 

Stork and Danheiser have developed a highly useful procedure for the synthesis of 4-alkylcyclohex-2-enones, which involves a -alkylations of cross-conjugated lithium dienolates of 3-alkoxycyclohex-2-enones, followed by metal hydride reduction of the carbonyl group and hydrolysis (Scheme 30). Numerous applications of this procedure have been reported.Two different alkyl groups may be introduced at the 6-position of a cyclohex-2-enone derivative without difficulty. While dialkylation is generally not a problem in alkylations of cross-conjugated dienolates of cyclohex-2-enones, it was observed when relatively acidic 3-chlorocyclohex-2-enones were employed. ... 

Bulky amido groups as ancillary ligands have been used as alternative to the Cp rings for the stabilization of a wide range of alkyltitanium derivatives and group 4 metal diamido dialkyl complexes are receiving special attention as potential catalysts for olefin polymerizations. 

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