Structure of an “Isodiimine” Complex: Bis(trimethylsilyl)isodiazenebis(cyclopentadienyl)vanadium

✍ Scribed by Dr. Michael Veith

• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: English
• Weight: 225 KB
• Volume: 15
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.197603871

✦ Synopsis

The action of methanol on the reddish brown compound does not lead to liberation of trimethylsilyl groups but instead, according to

to loss of cyclopentadienyl groups with formation of a brown diamagnetic complex of unknown structure which can be vacuum sublimed at 110°C. Its 'H-NMR spectrum contains only one signal for the trimethylsilyl protons and one for the methoxy protons at 6= -22 and -128 Hz (TMS internal standard, C6H6) respectively. The course of reaction can be interpreted by assuming that the vanadium central atom, which formally possesses an "excess" electron (i. e. 19 valence electrons)["] in the complex C P ~V N N ( S ~M ~~) ~, confers negative partial charges upon the two Cp ligands, thus facilitating attack of the cyclopentadienyl ring by a proton.

Procedure:

A mixture of CuCl(lO.1 mmol) and (Me3Si)2N2[31 in diethyl ether (50ml) is stirred with exclusion of oxygen and moisture at -50°C until all the CuCl has dissolved (ca. 3h). During this process, the initially yellow, then reddish brown, and finally colorless solution precipitates reddish brown fine crystals of [ ( 2 a ) . 2 CuCl], which is purified by repeated washing with ether.

Combination of Cp2V (5.0mmol) in diethyl ether (25ml) at -78°C with (Me3Si)2N2[31 in ether (10ml) under similar conditions immediately yields a dark green solution which deposits blackish green crystals on concentration. Above -20°C they transform into the dark brown ismeric product C P ~V = N N ( S ~M ~~) ~, m. p. 76-78 "C, which can be recrystallized from ether.