REACTIONS OF GROUP-6 FISCHER CARBENE COMPLEXES WITH ALKYNES - EFFECT OF THE METAL ON THE PRODUCT DISTRIBUTION AND THE ISOLATION OF A NONTAUTOMERIZED CYCLOHEXADIENONE COMPLEX
Wd. Wulff et al., REACTIONS OF GROUP-6 FISCHER CARBENE COMPLEXES WITH ALKYNES - EFFECT OF THE METAL ON THE PRODUCT DISTRIBUTION AND THE ISOLATION OF A NONTAUTOMERIZED CYCLOHEXADIENONE COMPLEX, Organometallics, 13(1), 1994, pp. 102-126
The first comparative study on the effect of the nature of the metal o
n the reactions of unsaturated group 6 Fischer carbene complexes with
alkynes is reported. The scope of the study includes both aryl- and al
kenylcarbene complexes of chromium, molybdenum, and tungsten for both
internal and terminal alkynes. Twenty-one different organic structural
types have been isolated and characterized from these reactions, but
in most instances phenols and indene (cyclopentadiene) products are th
e two most frequently observed. The general observation made is that p
henol formation is favored over indene (cyclopentadiene) formation in
the order chromium > tungsten > molybdenum. The effect of the concentr
ation of the alkyne on the distribution between phenol and indene (cyc
lopentadiene) was also examined and was found to be most prevalent in
the order molybdenum > chromium > tungsten. The bis(alkyne)(eta4-cyclo
hexadienone)molybdenum complex 107 has been isolated in which the fina
l tautomerization to the phenol product has not occurred. This complex
has been characterized by X-ray diffraction and provides support for
the previous interpretations of the concentration effects for the reac
tions of chromium complexes. This complex is the first example of the
long-proposed ultimate intermediate in these reactions. Crystal data f
or 107: space group P2(1)/c, Z = 4, a = 19.088(4) angstrom, b = 10.101
(1) angstrom c = 14.578(3) angstrom, a = 90.0-degrees, beta = 109.917(
13)-degrees, gamma = 90.0-degrees, R = 0.0598, and R(w) = 0.0788 for t
he 2405 reflections observed.