Structure of the Nitrosoguanidine Complexes of Nickel(II) and Copper(II) by X-ray Crystallography and Computational Analysis


Using the X-ray structure of solid nitrosoguanidine (ngH), potential structures of its complex with aqueous nickel(II) were surmised. A single-crystal X-ray diffraction determination of the Ni(II) complex confirmed one of these configurations. The X-ray structural parameters were compared with the most stable gaseous configurations derived from ab initio-MO calculations. The lowest energy calculated configuration of the nickel(II) complex and the X-ray crystal structure are in excellent agreement. The neutral diamagnetic, planar, red-colored [bis(nitrosoguanidate)nickel(II)] complex, [Ni(ng)2]°, is nitrogen coordinated in the trans configuration. It is highly insoluble in all solvents investigated, and has essentially the same crystal symmetry and unit-cell dimensions as the free ligand. In ligand crystals, two molecules have four nitrogen atoms aligned in a plane such that they are suitable for coordination to a nickel ion (1.945, 2.064 Å), when it is at the 1/2, 1/2, 1/2 unit-cell position. Furthermore, the complexes stack, as in [Ni(dmg)2]°, placing the nickel ions in nearly perfect positions for weak metal-metal bonding between adjacent layers at the near optimum distance of 3.65(1) Å. This results in a tight, linear macromolecule having low volatility and the extremely low solubility observed. As far as we are aware this is the first instance in which a ligand crystal structure is essentially the same as the complex it forms, with minor differences in bond distances, angles and torsion angles, and suggests some potentially unique properties and applications for this material.



Keywords and Phrases

Complex; Copper(II); Gaussian98; Nickel(II); Nitrosoguanidine

International Standard Serial Number (ISSN)

0095-8972; 1029-0389

Document Type

Article - Journal

Document Version


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© 2005 Taylor & Francis, All rights reserved.

Publication Date

01 Feb 2005