Date of Award

8-1985

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Dr. Lewis J. Radonovich

Abstract

The structures of five organonickel compounds were determined using x-ray diffraction techniques. This study was conducted to ascertain the relationships between the compound's structures, bonding, and chemical properties. The first structural evidence for discrete complexes containing Ni-SiX3 bonds is (h6-mesitylene)Ni(SiCl3)2 and presented. The compounds (h6-toluene)Ni(SiF3)2, crystallize in space group P21/c with Z = 2. The lattice constants at 23° C are: a = 9.056(2), b = 14.426(1), c = 13. 3 0 3 ( 2) ~, {J = 10 0. 6 9 ( 1 )0 , and a = 11. 3 5 5 ( 3) , b = 11.268(4), c = 14.326(8)~, and {J = 140.97(8)0 for the compounds, respectively. Both structures exhibit short Ni-Si bond distances and planar arenes, with other bond parameters similarly indicating significant Ni-to-SiX3 pi back-bonding. The SiF3 ligands are shown to be much better pi-acids than the SiCl3 groups. The most striking evidence for this is the unprecidented short Ni-SiF3 bond distance of 2.154(3)~ and the predictably short nickel to arene distance of 1.643(3)~ in (h6-toluene)Ni(SiF3)2. The analogous Ni-SiCl3 bond distance in (h6-mesitylene)Ni(SiCl3)2 is 2.194(1)~ while the nickel to arene-plane distance is 1.697(1)~.

Analysis of (C0)3Ni(SiCl3)2 revealed a long axial Ni-Si bond distance of 2.286(3)~ in the trigonal bipyramidal complex. The compound crystallizes in space group P21/c with Z = 2, with lattice constants at 25°C of: a= 9.709(8), b = 22.65(2), c = 6.731(5)~, and {J = 75.76(5)0 • The compound (H9C4S)2Ni(C6F5)2, crystallizes in space group P21/c with z = 2, with the Ni residing on a crystallographic center of inversion. The lattice constants at 23°C are: a= 10.698(3), b = 11.246(3), c = 9.561(2)~, and {J = 106.78(2). The Ni-C6F5 bond distance of 2.196(3)A indicates a reasonably strong bonding interaction without any appreciable Ni-to-C6F5 pi back-bonding. The compound [(h5-C5H5)Ni(C6F5)2] [(H5C2)4N] crystallizes with two formula units per unit cell in space group Pl, with lattice constants at 23° C of: a = 14.306(2), b = 0.930<1>, c = l0.599(2>A, a = 96.s1, and ry = 90.61(1)0 • The pi-Cp has a significant non-planar deformation attributable to electronic factors. -

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