Synthesis and Characterization of Functionalized N,N'-Diphenylformamidinate Silver(I) Dimers: Solid-State Structures and Solution Properties.
Functionalized N,N'-diphenylformamidines and their deprotonated silver(I) complexes have been synthesized: silver(I) N,N'-di(4-alkyl)phenylformamidinate (alkyl = methyl, ethyl, n-butyl, and n-hexadecyl) 1-4; silver(I) N,N'-di(4-trifluoromethyl)phenylformamidinate 5, silver(I) N,N'-di(3-methoxy)phenylformamidinate 6, silver(I) N,N'-di(3-methylmercapto)phenylformamidinate 7, silver(I) N,N'-di(2-methoxy)phenylformamidinate 8, silver(I) N,N'-di(2-methylmercapto)phenylformamidinate 9. The effects of increasing the coordination number of the silver(I) centers by donor substituents on the phenyl groups have been investigated by solution and solid-state studies. Variable-temperature proton NMR (223-303 K) for 1-4 shows coupling between the proton attached to the amidinate carbon and the (107/109)Ag centers at room temperature which is unaffected by cooling (2). For the four-coordinate complexes, 8 and 9, such coupling is only observed on cooling. Molecular weight measurements recorded in solution by vapor pressure osmometry at 310 K show some aggregation to higher molecular weight species than simple dimers for 1-4 and 6, but 8 and 9 exist as discrete dimeric species. Measurement of thermal stability shows the expected increase in stability with increasing coordination number. Compounds 8 and 9 were structurally characterized by X-ray methods. Both show four-coordinate silver dimers bridged by two amidinate ligands with additional longer interactions with the ether oxygens or thioether sulfurs.
Archibald
Stephen J.
SJ
Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, Department of Chemistry, University of Warwick, Coventry, CV4 7AL, United Kingdom, and Dry Media Systems Laboratory, Imation Corporation, St. Paul, Minnesota 55144.
Alcock
Nathaniel W.
NW
Busch
Daryle H.
DH
Whitcomb
David R.
DR