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Aryl bromides of the type BrCeHz(CHzNMez)z-2,6-R-4 (R = NHz, MeO, H, C1, MeC(0)) have been synthesized and have been used to prepare the corresponding organonickel(I1) complexes [NitCsHz(CHzNMez)z-2,6-R-4)Brl by an oxidative addition reaction to Nio(COD)2 (COD = cycloocta-1,5-diene). The effect that the para substituent of the monoanionic, N,C,N' terdentate, aryl ligand has on the electronic properties of the nickel complexes has been investigated by 13C NMR and UV/vis spectroscopy as well as by electrochemistry. The results show that para substitution on the aryl ligand markedly influences the nickel(I1) center; electron-donating substituents increase the ease of oxidation to NiIII, and direct correlations exist between chemical shift data for the carbon atom bonded to nickel and appropriate Hammett parameters.

in III, where it can be seen that because of the large phenyl substituents it is understandably disfavored here. IllIn conclusion, then, the introduction of the "stiffened backbone" in dppee, as contrasted with the flexible backbone in dppe, leads to certain changes in the conformational characteristics of these molecules. These conformational changes then have consequences with respect to the way in which the molecules are assembled in the complete crystal structure.Acknowledgment. Support from the National Science Foundation (Grant No. CHE85-14588 to F.A.C. and Grant No. 85-06702 to R.A.W.) is gratefully acknowledged.Registry No. a-Re2Cl4(dppee)2-«-PrOH, 114720-22-8; /3-Re2Cl4-(dppee)2, 110329-68-5; a-Re2Cl4(dppe)2, 114720-23-9; (n-Bu4N)2Re2Cls, 14023-10-0; [ReCl2(dppe)2]Cl, 15628-22-5; (zi-Bu4N)2Re2Br8, 14049-60-6; a-Re2Br4(dppe)2, 114720-24-0; a-[Re2Cl4(dppee)2]PF6, 114720-26-2; (Cp2Fe)PF6, 11077-24-0; a-[Re2Cl4(dppp)2]PF6, 114720-28-4; a-Re2Cl4(dppp)2, 86436-61-5; Re, 7440-15-5; a-Re2Cl4(dppee)2, 1 10329-67-4. Supplementary Material Available: Full tables of bond distances and bond angles and tables of anisotropic displacement parameters for a-Re2Cl4(dppee)2.«-PrOH and 0-Re2Cl4(dppee)2 and a table of torsional angles for the ß isomer (14 pages); listings of observed and calculated structure factors for both compounds (45 pages). Ordering information is given on any current masthead page.

Abstract:In order to construct bimetallic organometallic donor-acceptor complexes with nonlinear optical (NLO) properties, the bimetallic sesquifulvalene com-

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