The crystal and molecular structures of formyl-, cyano-, and amino-cyclopentadienyldicarbonylnitrosylchromium

The x-ray crystallographic structures of (η5-C5H4CHO)Cr(CO)2NO (I), (η5-C5H4CN)Cr(CO)2NO (II), and (η5-C5H4NH2)Cr(CO)2NO (III) are described. The formyl and amino derivatives were obtained from a literature preparation (Macomber and Rausch, 1983). The cyano derivative (II) was obtained by conversion of (η5-C5H4COOH)Cr(CO)2NO into [(η5-C5H4C(O)NH2]Cr(CO)2NO, followed by dehydration of the amide in acetic anhydride. (I) crystallizes in the monoclinic space groupP21/n witha=8.028(3),b=11.605(4),c=9.730(3)A,β=90.04(2)°, andDcalc=1.69 g cm−3 forZ=4. Refinement led to anR value of 0.031 based on 1279 observed reflections ([I>-3σ(I)]). (II) belongs to the triclinicP¯1 witha=6.838(3),b=6.879(3),c=10.130(3)A,α=92.23(2),β=92.98(2), γ=107.65(3)°, andDcalc=1.67 g cm−3 forZ=2. Refinement gaveR=0.042 for 1543 observed reflections. (III) was found to be orthorhombicPbca witha=7.259(3),b=13.449(3),c=18.090(5)A, andDcalc=1.64 g cmsu−3 forZ=8. Refinement producedR=0.026 for 767 observed reflections. In (I) the electron-withdrawing formyl group is foundtrans to the nitrosyl. The same holds for the cyano group in (II), but the amino function in (III) is nottrans to any of the tripod ligands.