The crystal and molecular structure of the compound azZe/M-^-oxo)(hemiporphyrazinato)iron(IV), [FeON8C26H14]", has been determined from single-crystal, three-dimensional X-ray diffraction counter data. The compound crystallizes as blue-black needles in space group P2/n with Z = 2 and unit cell dimensions (at 210 K) a = 16.090 (3) k, b = 3.975 (2) Á, c = 16.070(3) Á, and ß = 92.97 (1)°. The structure was refined by full-matrix least-squares techniques to a conventional R value of 0.045. Distorted (hemiporphyrazinato)iron units stack along the b axis and are linked into polymeric, uniformly spaced, linear
M-N distances in d°transition-metal nitrides parallel C-C bond lengths in linear and cyclic hydrocarbon polyenes. The structural similarity can be traced to the similar ir systems of the known nitrides and their polyene analogues: allyl and pentadienyl cations, as well as polyacetylene and cyclooctatetraene. We find that cyclic delocalization of its in-plane ir electrons should stabilize the as yet unknown benzene analogue (L"MoN)3. However, it is not certain that this system will have all equal MN bond lengths. The tendency in cyclic (L"MoN)4 to localize bonds or alternate bond lengths can be traced to a heteromorphic in-plane ir system and the efficient operation of a second-order Jahn-Teller mixing of its nondegenerate, nonbonding ir orbitals. In the corresponding tetrameric cyclic phosphazene the relevant in-plane P-and N-based orbitals are much more split in energy, and the driving force for localization is much diminished.
T h e cis-cyclooctene a n d norbornene complexes of AuCl, AuC1(cis-CgH14) (1) a n d AuCl (C,H,,) (2), respectively, have been prepared from t h e reaction of AuCl(C0) with t h e corresponding olefin a t room temperature by a CO displacement reaction. Gas volumetric equilibrium data on t h e reaction between AuCl(C0) and norbornene show that the formation of the olefin complex is favored at atmospheric pressure of carbon monoxide. T h e constant of t h e equilibrium AuCl(C0) + norbornene s AuCl(norbornene) + CO is K = 4 f 1 at 21.5 "C. No CO was found t o be displaced from AuCl(C0) with cyanoolefins. T h e crystal structure of 1 has been solved by X-ray diffraction methods. For 2, only t h e crystal d a t a and a structure with insufficient resolution were obtained. T h e crystal data at 190 K are as follows: 1, a = 23.115 (4) A, b = 5.419 (3) A, c = 7.356 (2) A, 2 = 4, orthorhombic, space group P c~2~, R = 0.037; 2, a = 5.697 (2) A, b = 20.24 (1) A, c = 6.620 (2) A, 2 = 4, orthorhombic, space group Ama2, R = 0.085. T h e gold atom presents t h e expected linear geometry, considering t h e olefin as a monodentate ligand.
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