Synthesis and characterization of novel dinuclear and cationic cyclobutadiene platinum complexes

Reactions of the cyclobutadiene platinum complexes [PtCl2(C4R4)](R = Me 1a, R = Et 1b) with diphosphines (Ph2PPPh2)-P-boolean AND ((boolean AND) = -c-=c- (dppa), -CH2- (dppm), -(CH2)(2)- (dppe), -(CH2)(3)- (dppp), -(CH2)(4)- (dppb)) in a 2:1 molar ratio result in formation of novel binuclear cyclobutadiene platinum complexes [{PtCl2(C4R4)}(mu-(Ph2PPPh2)-P-boolean AND)] (R = Me 2, Et 3). In contrast, reactions in equimolar ratio lead to formation of cationic complexes with dppe, dppp and dppb [PtCl(C4R4){Ph2P(CH2)(n)PPh2}]Cl (n = 2-4, R = Me 5, Et 6). Complexes 2, 3 and 5, 6 were fully characterized by microanalysis and by NMR and IR spectroscopies. Structural characterization of [{PtCl2(C4Me4)}(2)(mu-Ph2PCH2PPh2)] (2b) reveals a piano-stool coordination at each platinum center defined by the mu(4)-C4Me4 ligand, two Cl atoms and one P atom. The P-C-P angle of 131.0(4)degrees is larger than that expected for tetrahedral geometry. The X-ray structure of [PtCl(C4Me4){Ph2P(CH2)(3)PPh2}]Cl . CH2Cl2 (5b . CH2Cl2) reveals a Pt atom coordinated by the eta(4)-C4Me4 ligand, chloride and the two phosphorus donors in a piano-stool conformation. In the solid state, these cations are arranged to form channels with a diameter of 13.8 Angstrom in which solvent molecules (CH2Cl2) are embedded. (C) 1998 Elsevier Science S.A. All rights reserved.