Organometallic chemistry of group 4 metals containing nitrogen ligands
The room-temperature carbonylation (600-1000 psi) of solutions containing (ArO)[sub 2]-MR[sub 2], (ArO = 2,6-di-tert-butylphenoxide; M=Zr, Hf; R= methyl, benzyl) in the presence of pyridines (1 equiv.) leads to the formation of a series of [alpha], [alpha]'-disubstituted-2,6-pyridinedimethoxide compounds of formula (ArO)[sub 2]M[OCH (R)-pyr-CH(R)O], (pyr = NC[sub 5]H[sub 3], NC[sub 5]H[sub 2]-4Me, Nc[sub 5]H[sub 2]-4Ph). NMR studies of the latter show an approximate 50/50 mixture of the diastereomers meso and threo to be present. The mechanism for the reaction appears to involve sequential nucleophilic attack on the ortho-position of a pyridine ligand by an [eta][sup 2]-acyl group, initially formed by migratory insertion of CO into the metal-alkyl bond. Hydrolysis of these compounds allows the isolation of the corresponding [alpha][alpha]'-disubstituted pyridinedimethanols in good yields. The arylamido complexes (ArO)[sub 2]Zr(NHC[sub 6]H[sub 4]-4X)[sub 2] and M(NH-Ar')[sub 4], (M=Zr, Hf; X=H, F, CH[sub 3], OCH[sub 3], Br; Ar'=2,6-diisopropylphenoyl) were also prepared by reactions of (ArO)[sub 2]M(CH[sub 3])[sub 2] and M(CH[sub 2]Ph)[sub 4] with the corresponding arylamines. The arylamido compounds can be readily converted into five-coordinate terminal imido derivatives by pyridine induced elimination of arylamine. In formation of the phenyl-imidos (ArO)[sub 2]Zr(=NC[sub 6]H[sub 4]-4X)(py)[sub 2] from (ArO)[sub 2]Zr(NHC[sub 6]H[sub 4]-4X)[sub 2], four possible mechanisms were proposed in which the initial step is the formation of the five-coordinate monopyridine adduct (ArO)[sub 2] M(NHAr[sup X])[sub 2](py). Addition of more basic pyridines, as well as using electron withdrawing substituents on the phenyl rings of the arylamido precursors, favor the formation of the arylimido products.
- Research Organization:
- Purdue Univ., Lafayette, IN (United States)
- OSTI ID:
- 7205393
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKOXIDES
CARBONYLATION
AMIDES
CHEMICAL PREPARATION
HAFNIUM COMPLEXES
IMIDES
PYRIDINES
ZIRCONIUM COMPLEXES
ORGANOMETALLIC COMPOUNDS
AZINES
CHEMICAL REACTIONS
COMPLEXES
HETEROCYCLIC COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties