A Paramagnetic Diniobium Complex with a Very Short Nb−Nb Distance: Evidence for a Pseudo Nb−Nb Triple Bond?
✍ Scribed by Maryam Tayebani; Khalil Feghali; Sandro Gambarotta; Glenn P. A. Yap; Laurence K. Thompson
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 98 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0044-8249
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✦ Synopsis
Low-valent second-and third-row transition metals typically form significant and robust MÀM bonds. [1, 2] Divalent Group 5 metals provide a puzzling exception. In principle, the d 3 electronic configuration makes them good candidates for the formation of triple bonds. Exceedingly short VV triple bonds were indeed observed in a few dinuclear V II complexes, [3] although these bonds seem to display the same paradoxical weakness [4] that was previously observed for quadruply bonded dichromium compounds. [5] Conversely, for the heavier Nb and Ta homologues no such information is Experimental Section 1: Method A: A solution of potassium diphenylmethyldipyrrolide (1.3 g, 3.4 mmol) in THF (100 mL) was treated under N 2 with [SmI 2 (thf) 2 ] (1.8 g, 3.4 mmol). The color immediately changed to dark purple-brown. Stirring was continued for 12 h after which the solution was filtered to eliminate a small amount of insoluble material. The filtrate was concentrated to 50 mL and layered with toluene (50 mL). After the mixture had been left to stand at room temperature for 24 h, large, red-brown crystals of 1 (1.3 g, 0.66 mmol, 78 %) were obtained. Elemental analysis (%) calcd for