The preparation and characterisation of hetero- and homobimetallic complexes containing bridging naphthalene-1,8-dithiolato ligands

Homo- and heterobimetallic complexes of the form [(PPh3)(2)(mu(2)-1,8- S-2-nap)[MLn}] (in which (1,8-S-2-nap)= naphth o-1,8-dithiol ate and {MLn} = {PtCl2} (1), {PtClMe} (2), {PtClPh} (3), {Ptme(2)} (4), {PtlMe(3)} (5) and {Mo(CO)(4)} (6)) were obtained by the addition of [PtCl2(NCPh)(2)], [PtClMe-(cod)] (cod = 1,5-cyclooctadiene), (PtClPn(cod)], [PtMe2(cod)], [{PtIMe3}(4)] and [Mo(CO)(4)(nbd)] (nbd=norbornadiene), respectively, to [Pt(PPn(3))(2)(1,8-S-2-nap)]. Synthesis of cationic complexes was achieved by the addition of one or two equivalents of a halide abstractor, Ag[BF4] or Ag[ClO4] to [{Pt(mu-Cl)(mu-eta(2):eta(1)-C3H5)}(4)], [{Pd(mu-Cl)(eta(3)-C3H5)}(2)], [{IrCl(mu-Cl)(eta(5)- C5Me5)}(2)] (in which C5Me5=Cp*=1,2,3,4, 5-pentamethylcyclopentadienyl), [{RhCl(mu-Cl)(eta(5)-C5Me5)}(2)]. [PtCl2-(PMe2Ph)(2)] and [{Rh(mu-Cl)(cod)}(2)] to give the appropriate coordinatively unsaturated species that, upon treatment with [(PPh3)(2)Pt(1,8-S-2-nap)], gave complexes of the form [(PPh3)(2)(mu(2)-1,8-S-2- nap){MLn][X] (in which {MLn}[X]= {Pt(eta(3)-C3H5)}[ClO4] (7), {Pd(eta(3)-C3H5)}- [ClO4] (8), (IrCl(eta(5)-C5Me5)}[ClO4] (9), (RhCl(eta(5)-C5Me5)}[BF4] (10), (Pt-(PMe2Ph)(2)}[ClO4](2) (11), (Rh(cod)-[CIO4] (12); the carbonyl complex jRh(CO)(2))[ClO4] (13) was formed by bubbling gaseous CO through a solution of 12. In all cases the naphtho-1,8-dithiolate ligand acts as a bridge between two metal centres to give a four-membered PtMS2 ring (M=transition metal). All compounds were characterised spectroscopically. The X-ray structures of 5, 6, 7, 8, 10 and 12 reveal a binuclear PtMS2 core with Pt...M distances ranging from 2.9630(8)-3.438(1) angstrom for 8 and 5, respectively. The napS(2) mean plane is tilted with respect to the PtP2S2 coordination plane, with dihedral angles in the range 49.7-76.1 degrees and the degree of tilting being related to the Pt...M distance and the coordination number of M. The sum of the Pt(1) coordination plane/napS(2) angle, a, and the Pt(1)coordination plane/ M(2)coordination plane angle, b, a+b, is close to 120 degrees in nearly all cases. This suggests that electronic effects play a significant role in these binuclear systems.