Abstract
The prepn. and structural investigation of the compds. M2(chp)4 (M = Cr, Mo, W; Hchp = 6-chloro-2-hydroxypridine) are reported. The Cr and Mo compds. were prepd. by the reaction of the corresponding acetates, M2(O2CR)4, with the Lli salt of Hchp. W2(chp)4 was obtained by reaction of W(CO)6 with Hchp in refluxing diglyme. The compds. form isomorphous crystals belonging to the orthorhombic space group Pbca. Unit cell dimensions for the Cr, Mo, and W compds., in that order, are the following: a 16.078(2), 16.247(3), 16.9210(2) \AA; b 18.570(2), 18.559(3), 18.583(3) \AA; c 15.573(2), 15.827(2), 15.802(2) \AA. The M-M bond lengths are Cr-Cr 1.955(2), Mo-Mo 2.085(1), and W-W 2.177(1) \AA. These distances are all longer than the corresponding distances in the related M2(mhp)4 compds. (Hmhp = 6-methyl-2-hydroxypyridine). The substitution of Cl for the Me group results in a significant increase in the M-M bond length with the greatest increase, 0.066 \AA, being found in the Cr compd. This observation leads us to suggest that inductive effects may play an important role in detg. the M-M bond distance. on SciFinder(R)
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