Copper chloro-bridged dimer

The structure of the Cu2(Et2Dtc)2Cl2 complex (315) consists of symmetrical chloro-bridged dimers weakly associated through intermolecular Cu-Cl [2.874(2) A] and Cu-S [2.882(2) A] interactions (Fig. 12). Each copper has a five-coordinate square pyramidal coordination not unlike that found in the structures of the Cu(R2Dtc)2 complexes (53, 507). 

The structure of 73 was substantiated spectroscopically (5 nB = 82.5 ppm) and confirmed crystallographically. A centrosymmetric chloro-bridged dimeric structure with tricoordinate copper centers was observed. The pendant character of the borane is apparent from the rather long the B- Cu (3.05 A) and B- Cl (4.06 A) distances associated with a trigonal planar geometry around boron. Compared to related mononuclear palladium and rhodium complexes (see Section IV.B), the presence of the chloro-bridge disfavors the formation of Cl-B interactions (coordination mode F) in 73. 

Several complexes have beeai found to be dimeric. Infrared spectroscopy shows that the CuNCS(L) complexes (L = py, 2- or 4-picoline, 3,5-lutidine, or quinoline) contain bridging thiocyanato groups (332). The mass spectra of CuX P(cyclohexyl)3 complexes (X = Cl, Br, I) show no peaks of higher mass than those corresponding to dimeric molecules, and the far-infrared spectrum of the chloro complex indicates that they are dimeric with halo bridges (248). Triphenylphosphine reacts with copper(I) trifluoroacetate in dichloromethane to give [Cu(02C CF3)(PPh3)]2 which is dimeric in chloroform but partially dissociated in dichlorobenzene (107). 

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