J. Takacs et Rg. Cavell, SYNTHESIS AND CHARACTERIZATION OF NEW D0 TUNGSTEN AND MOLYBDENUM IMIDO COMPLEXES WITH HETEROATOMIC BIFUNCTIONAL O-N CHELATE LIGANDS, Inorganic chemistry, 33(12), 1994, pp. 2635-2638
New tungsten d0 bis(imido) compounds of formula W(NCMe3)2(O-N)2 (2a-e)
(HO-N = 2-hydroxypyridine, 2-pyridinecarboxylic acid, 8-hydroxyquinol
ine, 8-hydroxyquinaldine, 2-(2-hydroxyphenyl)benzothiazole, and 2-(2-h
ydroxyphenyl)benzoxazole) have been prepared from the bis(amido) bis(i
mido) compound W(NCMe3)2(NHCMe3)2 (1) by protonation and subsequent re
placement of the amido groups with heteroatomic chelate ligands of the
type HO-N which are weak acids and strong nitrogen bases. Solution sp
ectroscopic data suggest that the new hexacoordinate tungsten(VI) imid
o complexes are monomeric and six-coordinate with equivalent imido lig
ands. The four-coordinate molybdenum bis(imido) complex Mo(NCMe3)2(OSi
Me3)2 (3) reacts with 1,2-dihydroxybenzene (CatH-2) in the presence of
pyridine, yielding the six-coordinate compound of formula Mo(NCMe3)(C
at)(OSiMe3)2(PY) (4), while the reaction with 2 equiv of the heteroato
mic chelate ligand 8-hydroxyquinoline yields the six-coordinate mixed
oxo imido compound of formula Mo(NCMe3)(O)(N-O)2 (5) (HO-N = 8-hydroxy
quinoline) by elimination of tert-butylamine and hexamethyldisiloxane.
In a different manner, the protonation of the isoelectronic organomol
ybdenum species Mo(NCMe3)2(Mes)2 (6) (Mes = 2,4,6-trimethylphenyl) wit
h 1 equiv of 8-hydroxyquinoline or 8-hydroxyquinaldine results in the
cleavage of one mesityl group, leading to the formation of five-coordi
nate compounds of formula Mo(NCMe3)2(Mes)(O-N) (7a,b).