Dialkyl complexes

Figure 3.56 A rigid t/wis-dialkyl complex that is particularly stable to thermal elimination.

In a related study, sterically bulky amidinate ligands containing terphenyl substituents on the backbone carbon atoms have been utilized in organoalumi-num chemistry. Mono(amidinate) dialkyl complexes were generated as shown in... 

In a systematic study, it was demonstrated that, using a specially designed bulky benzamidinate ligand, it is possible to isolate mono(amidinato) dialkyl complexes over the full size range of the Group 3 and lanthanide metals, i.e., from scandium to lanthanum. The synthetic methods leading to the neutral and cationic bis(alkyls) are summarized in Scheme 56. Figure 18 displays the molecular structures of the cations obtained with Sc, Gd, and La. ... 

The first organometallic zirconium complexes to be prepared all contained Zr( 1V) and were reported almost contemporaneously. The reaction of Zr(TPP)-(OAc)2 with RLi or RMgBr produced the dialkyl complexes Zr(TPP)R2 (R = Me, Et, n-Bu or Ph), characterized by. spectroscopy. The development of the chlorozirconium complexes opened up the chemistry further, with... 

The first ruthenium porphyrin alkyls to be reported were prepared from the zerovalent dianion, [Ru(Por)] with iodomethane or iodocthane, giving the ruthe-nium(lV) dialkyl complexes Ru(Por)Me2 or Ru(Por)Et2 (Por = OEP, TTP). Alternatively, the Ru(lV) precursors Ru(Por)X2 react with MeLi or ArLi to produce Ru(Por)Mc2 or Ru(Por)Ar2 (Ar = / -C(,H4X where X = H, Me, OMe, F or Cl) 147-149 The osmium analogues can be prepared by both methods, and Os(Por)R2 where R = Me, Ph and CH2SiMe2 have been reported.Some representative structures are shown in Fig. 5, and the preparation and interconversion of ruthenium porphyrin alkyl and aryl complexes are shown in Scheme 10. 

Attempts to exploit the reaction of the dianion with alkyl halides to produce a c/.v-dialkyl complex by using 1,2- or 1,3-dihaloalkanes did not indeed give this result. The reaction of Ru(Por) " with 1,2-dibromoethane was sucessful, but the resulting metallacyclopropane product is better formulated as a /r-complex of ethene, and will be discussed below in the section on alkenc and alkyne complexes. The corresponding reaction of the diiinion with 1,3-dichloropropane gave no evidence for a metallacyclobutane. but instead free cyclopropane was detected by GC analysis and the porphyrin product was Ru(TTP)(THF)2. ... 

Mo and W alkylidene complexes usually are prepared from M(VI) dialkyl complexes by some variant of the a hydrogen abstraction reaction (Eq. 7 other ligands omitted) [5,41]. 

The source of the alkyls is usually some main group alkylating agent, and the groups that are replaced on M to form a dialkyl complex usually are halides. When the alkyl group contains one or more (3 protons, then the predominant re-... 

Unsymmetrical vicinal diols can be prepared from a three-component reaction of aldehydes, CO, and aminotroponiminate-ligated titanium dialkyl complexes. Solutions of Me2TiL,2 (L = N -dimethylaminolroponiminalc) react rapidly with CO at room temperature. Double methyl migration to CO produces an 2-acclonc complex which inserts the aldehyde to afford a titana-dioxolane and releases the unsymmetrical diol upon hydrolysis [65]. 

Alkylation of a complex such as L2PdCl2 will in many instances lead to double alkylation or a mixture of monoalkyl and dialkyl complexes. A convenient alkylating agent giving purely monomethylpalladium turned out to be tetramethyltin, which has been widely used [12,14], reaction (7), Figure... 

ROH (CFjl MeCOH generated by hv-induced elimination of IMS from the dialkyl complex... 

Further reaction of U[CH2(CsH4)2]Cl2 with various alkyl Htium reagents results in the isolation of stable dialkyl complexes. 

The Mn(II) dialkyl complex [Mn(-CH2- Bu)2(Me2NCH2CH2NMe2)j reacts with silica Si02 7oo to yield mostly the monosiloxy complex ](=SiO)Mn(-CH2- Bu) (Me2NCH2CH2NMe2)j, while reaction with less dehydroxylated silica (Si02 5oo and... 

Addition of triphenylphosphine or t-butylisocyanide to 101 affords the analogous five-coordinate complexes 102b and 102c. These species represent rare examples of stable five-coordinate ds-dialkyl complexes of Ni(II), although stable trigonal-bipyramidal trans-dialkyls of nickel are well known (176-178), and they provide a structural model for a putative square-pyramidal intermediate in reductive elimination reactions of ds-dialkyl... 

Amino-7,8-benzoquinoline, in trinuclear Ru clusters, 6, 729 Amino-bisphenoxo ligands, in Ti(IV) dialkyl complexes,... 

Aminocyclopropanations, via Ti(IV) complexes, 4, 655 Amino-diamido ligands, in Ti(IV) dialkyl complexes, 4, 349 Aminodiolates, with Zr(IV), 4, 805 /3-Aminoenonate, liquid crystals, 12, 259 Aminoethyl side chains, on bis-Cp titanium halides, 4, 524 Amino glycal reagents, via rhodium(II)-catalyzed... 

Dialkylborinic acids, amination reactions, 9, 188 Dialkylborinic esters, amination reactions, 9, 188 Dialkyl complexes... 

Imido dialkyl complexes, with tantalum, 5, 120 Imido-dicarbenes, with palladium, 8, 228-229 Imido groups, in Ru-Os mixed-metal clusters, 6, 1078 Imido hydrocarbyl complexes, with Re(VII), 5, 945 Imido ligands... 

A rare example of isospecific 3,4-polymerization of isoprene mediated by a constrained-geometry rare-earth metal initiator was reported by Z. Hou [270]. Binuclear silyl-linked cyclopentadienyl phosphido lanthanide dialkyl complexes were synthesized in good yields and activated with an equimolar amount of [Ph3C] [B(C6Fs)4] (Scheme 68). Cationic alkyl species were proposed as intermediates and an activation scenario was presented based on DFT calculations [270]. 

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