SYNTHESIS, STRUCTURE AND ELECTROCHEMISTRY OF PH2PCH2PPH2- BRIDGED, HETEROMETALLIC COMPLEXES CONTAINING A (ETA-C5H4ME)MN(CO)2 FRAGMENT

Heterometallic complexes and clusters were prepared by using the new m etallophosphine [Mn(eta-C5H4Me)(CO)2(dppm-P)] 1 obtained from [Mn(eta- C5H4Me)(CO)3] and Ph2PCH2PPh2 (dppm). The dark green complexes [(OC)2( eta-C5H4Me)Mn(mu-dppm)PdCl2] and [{(eta-C5H4Me)-Mn(mu-CO)2(mu-dppm)Rh( mu-Cl)}2], which contain metal-metal bonds, have been obtained by the reactions of 1 with [PdCl2(NCPh)2] and [{Rh(cod)(mu-Cl)}2] (cod = cycl oocta-1,5-diene), respectively. Starting from [Pt(cod)2], the trimetal lic complex [Pt{(mu-dppm)Mn(eta-C5H4Me)(CO)2}2] was formed and a rever sible Mn-Pt bond formation has been observed by variable-temperature P -31-{H-1} NMR spectroscopy. Reactions of 1 with [PtCl2(NCPh)2], [{Re(C O)3(thf)(mu-Br)}2] (thf = tetrahydrofuran), [{RuCl(CO)3(mu-Cl))2] and [{Ir(cod)(mu-Cl)}2] led in high yields to complexes of the type Mn-dpp m-M-dppm-Mn (M = Pt, Re, Ru or Ir) having no metal-metal interaction. With [Mn(eta-C5H4Me)(CO)2(thf)], [{Pd(eta3-C3H4Me)(mu-Cl)}2] or [AuBr( tht)] (tht = tetrahydrothiophene) bimetallic complexes of the type Mn- dppm-M' (M' = Mn, Pd or Au) were obtained again with no metal-metal in teraction. Another route to this type of bimetallic complexes consists of the reaction of [(OC)2(eta-C5H4Me)Mn(mu-dppm)PdCl2] with two-elect ron donor ligands such as isocyanides RNC (R = 2,6-xylyl or Bu(t)), wh ich yielded [(OC)2(eta-C5H4Me)Mn(mu-dppm)Pd(CNR)Cl2]. Reaction of the isocyanide complexes with azetidine did not lead to the expected carbe ne complexes, instead the isocyanide ligand was substituted by azetidi ne, yielding [(OC)2(eta-C5H4Me)Mn(mu-dppm)Pd(NHC3H6)Cl2]. The structur es of the xylyl isocyanide and azetidine complexes have been determine d by X-ray diffraction. Reaction of [(OC)2(eta-C5H4Me)Mn(mu-dppm)AuBr] with the metalate K[Fe{Si(OMe)3}(CO)3(PPh3)] gave in high yield the h eterotrimetallic chain complex eta-C5H4Me)Mn(mu-dppm)-AuFe{Si(OMe)3}(C O)3(PPh3)]. Reaction of 1 with trans-[Pt{W(eta-C5H4Me)(CO)3}2(NCPh)2] afforded the cluster (mu3-CO)2(mu-CO)4{(mu-dppm)Mn(eta-C5H4Me)(CO)2}2] . An electrochemical study of some of the complexes has provided evide nce for possible electronic communication between the metal centres.