Synthesis, Structural, Spectroscopic, and Magnetic Characterization of Two-coordinate Cobalt (II) Aryloxides with Bent or Linear Coordination

Abstract

Treatment of the cobalt(II) amide, [Co{N(SiMe3)2}2]2, with four equivalents of the sterically crowded terphenyl phenols, HOArMe6 (ArMe6 = C6H3-2,6(C6H2-2,4,6-Me3)2) or HOAriPr4 (AriPr4 = C6H3-2,6(C6H3-2,6-Pri2)2), produced the first well-characterized, monomeric two-coordinate cobalt(II) bisaryloxides, Co(OArMe6)2 (1) and Co(OAriPr4)2 (2a and 2b), as red solids in good yields with elimination of HN(SiMe3)2. The compounds were characterized by electronic spectroscopy, X-ray crystallography, and direct current magnetization measurements. The O–Co–O interligand angles in 2a and 2b are 180°, whereas the O–Co–O angle in 1 is bent at 130.12(8)° and its cobalt(II) ion has a highly distorted pseudotetrahedral geometry with close interactions to the ipso-carbons of the two flanking aryl rings. The Co–O distances in 1, 2a, and 2b are 1.858(2), 1.841(1), and 1.836(2) Å respectively. Structural refinement revealed that 1, 2a, and 2b have different fractional occupations of the cobalt site in their crystal structures: 1, 95.0%, 2a, 93.5%, and 2b, 84.6%. Correction of the magnetic data for the different cobalt(II) occupancies showed that the magnetization of 2a and 2b was virtually identical. The effective magnetic moments for 1, 2a, and 2b, 5.646(5), 5.754(5), and 5.636(3) B respectively, were indicative of significant spin–orbit coupling. The differences in magnetic properties between 1 and 2a/2b are attributed to their different cobalt coordination geometries.

Department(s)

Chemistry

Sponsor(s)

National Science Foundation (U.S.)

Comments

Financial support by National Science Foundation (U.S.), Grant Nos. CHE-1263760 and DBIO-722538; National Science Foundation (U.S.) Graduate Research Fellowship Program (Grant No. DGE-1148897)

International Standard Serial Number (ISSN)

0020-1669

Electronic OCLC #

37637103

Print OCLC #

1753164

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2014 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Mar 2014

Link to Full Text

Share

 
COinS