ISSN:
0009-2940
Keywords:
Metallocene complexes, bent
;
Titanium complexes
;
Vinylidene complexes
;
Transition metal complexes
;
Heterodinuclear complexes
;
Carbene complexes
;
Early-Late heterodinuclear complexes
;
Metallacycles
;
Oxatitanacyclobutane complexes
;
Oxatitanacyclopentene complexes
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Cyclic Isomeric Four- and Five-Membered Heterodinculear Carbene Complexes - Formed from a Titanocene Vinylidene Fragment and Metal CarbonylsThe four-membered heterodimetallic carbene complexes Cp*2 16 [LnM: Cr(CO)5 (a), Mo(CO)5 (b), W(CO)5 (c), CpRe(CO)2 (f), Mn2(CO)9(g), Re2(CO)9 (h), Fe(CO)4 (i), Rh(acac)(CO) (i)] are easily prepared by trapping the vinylidenetitanocene [Cp*2Ti=C=CH2] fragment 6 with the corresponding metal carbonyls. The vinylidenetitanocene 6 is generated in a favourable manner from Cp*2Ti(CH3)CH=CH2 (13) or Cp * (Fv)TiCH = CH2 (14) [Fv: C5(CH3)4CH2] by a 1,3-H shift (α elimination) at room temperature. The formation of 16 is characterized by a preferred suprafacial [2 + 2] cycloaddition. Starting from Cp*2 (5) or 14 and transition metal carbonyls unexpected isomeric five-membered titanacycles Cp*2 8 [MLn = a-c, MnCp(CO)2 (d), MnCp′(CO)2 (e), f-i] are obtained at higher temperatures (70-100°C). These oxatitanacyclopentenes 8 are formed also upon heating via the kinetic product 16 with high yield, as a result of a 1,2-hydrogen shift, proved for c, g, h. From the spectroscopic data an η1-vinylcarbene structure is deduced, exhibiting a cis- (16) or trans-configurated (8) LnM=C—C=C sequence. An X-ray structure analysis shows the importance of the acyl resonance form in 8a, typically observed for such heterodimetallic carbene complexes. The reversible liberation of the metal carbonyl is a remarkable property of complexes 16 in solution, whereas the thermodynamic product 8 shows the typical properties of Fischer carbene complexes.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19941270607
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