Transition metal complexes monosubstituted

Ammonium dithiocarbamates can be prepared through reaction (11). With HC1 or H2S04 at lower temperatures the free acids are formed. Only one transition metal complex (37) is known, with a pseudo-octahedral coordination of Ni four sulfur atoms of the dithiocarbamate in the equatorial plane and two pyridine solvent molecules at the apical positions. Sulfides can be eliminated from monosubstituted dithiocarbamates to give isothiocyanates.53... 

Organomercurials can also be used for the synthesis of alkyl complexes. Organomercurials have stable alkyl-mercury bonds, and the alkyl groups can be transferred to transition metal complexes (alkylation of the transition metal complexes). Thus diphenylmercury reacts with one equivalent of dichloroplat-inum complex to produce phenylmercuric chloride and monosubstituted platinum complex in good yield 73). 

The Lewis acid-mediated [4+2] cycloaddition of conjugated enynes with alkynes affords arenes however, it is limited to the intramolecular cycloaddition [44]. The use of transition metal complexes realizes the catalytic intermolecular variants. The first example was reported in the paUadium(O)-catalyzed homo-[4+2] cycloaddition of monosubstituted conjugated enynes giving substituted styrenes (Scheme 21.38) [45]. Importantly, this reaction proceeded with definite regioselectivity. 

Pyrazole and its C-methyl derivatives acting as 2-monohaptopyrazoles in a neutral or slightly acidic medium give M(HPz) X, complexes where M is a transition metal, X is the counterion and m is the valence of the transition metal, usually 2. The number of pyrazole molecules, n, for a given metal depends on the nature of X and on the steric effects of the pyrazole substituents, especially those at position 3. Complexes of 3(5)-methylpyrazole with salts of a number of divalent metals involve the less hindered tautomer, the 5-methylpyrazole (209). With pyrazole and 4- or 5-monosubstituted pyrazoles M(HPz)6X2... 

Because of n-electron donation by the heteroatom, these carbene complexes are generally less electrophilic at C than the corresponding non-heteroatom-substituted complexes (Chapter 3). This effect is even more pronounced in bis-heteroatom-substituted carbenes, which are very weak Tt-acceptors and towards low-valent transition metals show binding properties similar to those of phosphines or pyridine. Alkoxycarbenes, on the other hand, have electronic properties similar to those of carbon monoxide, and stable heteroatom-monosubstituted carbene complexes are also usually formed from metals which form stable carbonyl complexes. 

Complexes of Heavier Transition Metals Electrochemical Studies Luminescence Studies IV. Hydrogen Bonding and Other Weak Interactions in Complexes of Squaric Acid and Its Monosubstituted Derivatives References... 

Transition-metal 7i-cyclopentadienyl complexes are known for all of the naturally occurring transition and inner transition metals and representative examples are grouped below according to their positions in the periodic chart. For the sake of brevity, most of the work involving monosubstituted cyclopentadienyl and mixed-sandwich (i.e., cyclopentadienyl-metalloboranes ) complexes has been excluded. 

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