BIMETALLIC COMPLEXES - V - SYNTHESIS AND REACTIONS OF C5H4PPH2-BRIDGED ZIRCONIUM-RHENIUM COMPLEXES

Bimetallic Zr-Re complexes with bridging C5H4PPh2 ligands (henceforth abbreviated as Cp') are accessible from the mononuclear zirconocene di chloride Cp-2'ZrCl2, (1) and reactive rhenium complexes. The attempted synthesis of a cationic complex from 1 and [Re(CO)(3)(NCMe)(3)]BF4 re sulted in the formation of the zirconium-free compound [ReCl(CO)(3)(C1 0H10(PPh2)(2))] (2). 2 is apparently formed by cleavage of the Cp'-Zr bonds followed by intramolecular Diels-Alder addition. The compound wa s fully characterized including an X-ray crystal structure determinati on of the CDCl3 solvate (triclinic, space group P (1) over bar (No. 2) , a = 945.1(5) pm, b = 1113.9(6) pm, c = 1855.5(10) pm, alpha = 92.36( 3)degrees, beta = 89.98(3)degrees, gamma = 113.49(2)degrees, V = 1.821 (2) x 10(9) pm(3), Z = 2). 1 and the highly reactive 'salt' [Re(CO)(5) FBF3] give the mono-bridged ionic complex [Cp'Cl2Zr(mu-Cp')Re(CO)(5)]B F4 (3). The doubly Cp'-bridged complex [Cp-2'Cl2ZrReCl(CO)(3)] (4) may be obtained from 1 and either [Re(CO)(5)Cl] or, more cleanly, [Re-2(m u-Cl)(2)(CO)(6)(THF)(2)]. Reaction of 4 with a stoichiometric amount o f LiAlH4 gives the bridging hydride complex [Cp-2'ClZr(mu-H)ReH(CO)(3) ] (5). From 5 and NaSMe the analogous methyl thiolate complex 6 was ob tained in an NMR tube experiment. Reduction of 4 using sodium amalgam produces the dark blue-green complex [Cp-2'ClZr-Re(CO)(3)] (7) which c ontains a direct Zr-Re bond. Addition of HCl across this polar metal-m etal bond gives two isomeric hydrides [Cp-2'Cl2ZrReH(CO)(3)] (8a, b) i n a 1:1 ratio and with fac and mer coordination geometries around rhen ium, respectively. (C) 1998 Elsevier Science S.A.