Synthesis and structure of the diynyl complexes [Mo(CCCCR)L2(η-C7H7)], L2 = chelate N- or P-donor ligand, R = SiMe3 or H:: X-ray crystal structures of [Mo(CCCCSiMe3)(2,2′-bipyridine)(η-C7H7)] and [Mo(CCCCH)(Ph2PCH2CH2PPh2)(η-C7H7)]

The reaction of LiC CC CSiMe3 with [MoBr(N-N)(eta-C7H7)] in thf affords the diynyl complexes [Mo(C CC CSiMe3)(N-N)-(eta-C7H7)), (1, N-N=2,2'-bipyridine (bipy); 2, N-N=1,4-Bu-2(t)-1,3-diazabutadiene (Bu-t-dab)]; an analogous procedure yields 2 [Mo(C CC CSiMe3)(CO)(PPh3)(eta-C7H7)], 3 starting from [MoBr(CO)(PPh3)(eta-C7H7)]. Replacement of bipy in complex I with Ph2PCH2CH2PPh2 (dppe) in refluxing toluene gives [Mo(C CSiMe3)(dppc)(eta(7))], 4. Proto-desilylation of 2 and 4 leads to eta-C7H7 formation of the unsubstituted diynyls [Mo(C CC CH)L-2(T-1-C7H7)] (5, L-2 = Bu-t-dab; 6, L2 = dppe). Cyclic-voltammetric studies in CH2Cl2, reveal that each of complexes 1, 2 and 4-6 undergo reversible one-electron oxidation processes on the electrochemical time-scale. The X-ray crystal structures of complexes I and 6 are reported; the bipyridine complex 1, exhibits a pi-pi stacking interaction between the bipy ligands of adjacent molecules leading to a head-to-head interaction between diynyl ligands and a resultant substantial bending of the diynyl chain. (c) 2006 Elsevier B.V. All rights reserved.