James F. Wishart, Christopher Ceccarelli, Richard L. Lintvedt, Jeremy M. Berg, David P. Foley, Tom Frey, James E. Hahn, Keith O. Hodgson and Robert Weis
Inorg. Chem. 22, 1667-1671 (1983)
Abstract:
The title compounds have been crystallized and examined by X-ray diffraction techniques. The structure of Cu2(PAAan)2°C6H6 consists of stacks of alternating bis[2,2-dimethyl-7-(phenylimino)-3,5,7-octanetrionato]dicopper(II), Cu2(PAAan)2, and benzene molecules in an ADAD... pattern. Crystal data are as follows: C2/m, a = 19.001 (9) Å, b = 6.516 (3) Å, c = 15.802 (6) Å, beta = 113.36 (3)°, R1 = 0.044, R2 = 0.058. The structure of Cu2(PAApnan)2°2C6H6 consists of benzenes positioned directly above and below the center of the bis[2,2-dimethyl-7-((4-nitrophenyl)phenylimino)-3,5,7-octanetrionato]dicopper(II) molecule. These units are stacked in a DADDAD... pattern. Crystal data are as follows: C2/c, a = 15.312 (3) Å, b = 10.399 (2) Å, c = 23.743 (4) Å, beta = 91.82 (1)°, R1 = 0.039, R2 = 0.048. In Cu2(PAAan)2°C6H6 the planes of the alternating benzenes and metal complexes are parallel and separated by 3.258 (2) Å. In Cu2(PAApnan)2°2C6H6 the two benzenes and each complex are effectively parallel (dihedral angle 1.4°) and separated by 3.262 (8) Å. The interplanar spacing between benzene molecules associated with different binuclear chelates within the same stack is 3.860 (8) Å. These values are consistent with those found in a great many organic pi-molecular complexes and are indicative of a weak donor-acceptor interaction between the benzene and binuclear Cu(II) complex. In both compounds the copper atoms and the donor atoms are coplanar, and both compounds are diamagnetic at room temperature. These results support the conclusion that coplanarity is a structural prerequesite for optimal antiferromagnetic exchange.