Bridging allyl ligands

Reduction of ReCls with excess allylmagnesium halide produces orange Re2( r-C3H5)4 dimers . A D2d geometry and no bridging allyl ligands characterize this Rej unit ". A thorough treatment of related Re chemistry is available . 

The ditungsten complex, W2(C3H5)2(NMe2)4 (79), has Ci symmetry in the solid state with bridging allyl ligands that exhibit an unusual /n-jj i/j -Z-propenyl coordination mode, and the reaction of W2(OR)g with allene generates the... 

The reaction of [Ru6C(CO)1fiJ2 4 with allyl bromide at 85°C affords [Ru6C(CO)15(Ja-C3H5)] 92 in 37% yield (Scheme 17).53 The solid-state structure of 92 shows that the allyl ligand bridges an edge of the cluster... 

The more elegant route—which we call for simplicity the method of [1 + l]-addition —may also be used to prepare other binuclear complexes containing either two allyl groups, or one allyl group and one halogen in the bridging positions. The results so far obtained are summarized in Eqs. (9) and (10). Compounds 45-47 are the first allyl-transition metal complexes in which not one metal atom but a dimetal unit is coordinated sandwich-like by two i73-bonded allylic ligands (75, 79). 

The presence of simple ir-allyl and ir-cyclopentadienyl ligands symmetrically coordinated to an M3 unit seems to be unique. Bridging allyl groups are found in [C3H5Pt(acac)]2 (42) and in the tetrameric [C3H5PtCl]4 (43), but they are linked differently to the platinum atoms, namely mono-hapto to one platinum and dihapto to the other. There is also no metal-metal bond formed in these complexes. 

Molybdenum(II) and molybdenum(III) form an extensive array of multiply bonded dimers, which contain Mo-Mo quadruple and triple bonds respectively. Much of the organometallic chemistry of this class of compound has come principally from the work of one research group. Homoleptic compounds suchas [Mo2Me8]" , [Mo() -allyl)4], which contains bridging and terminal allyl ligands (see Bridging Ligand), are readily synthesized from [Mo2(OAc)4]... 

A silyl-bridged bis(allyl)ligand made from the bis(allyl) silane Me2Si(CH2CHCHSiMe3)2 can be converted into its dilithium or dipotassium salt (i.e. K2[3-(C3H3SiMe3-l)2SiMe2]) (equation 1) it has been used in the synthesis of ans a-bis(allyl) complexes. ... 

Hegedus and Tamura (66) postulated that reactions of acyliron, acyl-nickel, and cobalt carbonyl anions with ij -allyl complexes of palladium proceed via unstable bimetallic intermediates with bridging o-,7r-alkenyl ligands, L (RC(0))M T7 T7--CH=CHR PdL . Products isolated from the acylation of rr-allyl ligands were a,/3- and a,y-unsaturated ketones. 

Trimetallic complexes with two identical cr,7r-bridging ring ligands having different ring sizes and numbers of tt attachments have been studied. The complexes with two bridging cyclohexadienyl (19a), cyclohepta-dienyl (19b), and cycloheptatrienyl (19c-f) ligands were synthesized by the nucleophilic addition reactions of dianionic carbonylmetallates, [M(C0)4]- (M = Os, Ru), and two equivalents of the appropriate cationic-metal allyl substrates (82). 

As far as we are aware, no examples of bimetallic complexes of the structural type G exist, where a C, allyl ligand acts as an bridging ligand with two transition metals but without metal-metal bonds. Methods for the preparation of such complexes are not obvious and may pose a synthetic challenge. In contrast, many examples of /A-allyl (B), p-... 

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