The coordination of low-valent group 13 organyls E I R [E = Al, Ga, In; R = Cp*, C(SiMe 3 ) 3 ] to transition metals has attracted increasing interest over the past decade. Complexes and cluster compounds of these new ligands with a number of transition metals have been isolated and characterised. The E I R moiety is formally isolobal with CO and PR 3 (R = alkyl, Cp*) or carbenes (R = chelating group) with varying σ-donor and π-acceptor properties depending on the organic group R

The synthesis and structural characterization of the novel homoleptic cluster complexes [Pd2(GaCp*)2(mu2-GaCp*)3] (1c), [Pd3(GaCp*)4(mu2-GaCp*)4] (2b) and [Pd3(AlCp*)2(mu2-AlCp*)2(mu3-AlCp*)2] (3) (Cp*=C5Me5) are presented. Furthermore, ligand exchange reactions of these cluster complexes are explored. In contrast to the electronically and sterically saturated complexes [M(ECp*)4] (M=Ni, Pd, Pt), the new unsaturated analogues [M(a)(ER)b] (E=Al, Ga, In) react with a variety of typical ligands (Cp*Al, CO, phosphines, isonitriles) to give new di- and tri-substituted compounds like [Pt2(GaCp*)2(mu2-AlCp*)3] (1d), [PdPt(GaCp*)(PPh3)(mu2-GaCp*)3] (4b), or [Pd3(PPh3)3(mu2-InCp*)(mu3-InCp*)2] (8). The trends of the reactivity of [M(a)(ER)b] as well as their fluxional behavior in solution has been elucidated by NMR spectroscopy, resulting in a mechanistic rationale for the ligand exchange reactions as well as the fluxional processes.

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The monomeric homoleptic Pt(0) complex [Pt(GaCp*)4] (1) has been synthesized by reaction of [Pt(COD)2] with GaCp* in hexane. The monomeric homoleptic Pd(0) complexes [Pd(GaCp*)4] (2) and [Pd{InC(SiMe3)3}4] (3) are accessible by reaction of [Pd(tmeda)(CH3)2] with GaCp* and [InC(SiMe3)3], respectively. These reactions were shown to proceed via methyl group transfer from palladium to indium or gallium, respectively. Complexes 1 and 2 can be used as building blocks for the synthesis of dinuclear cluster compounds. Thus, reaction of [Pt(COD)2] with 1 or 2 and subsequent addition of GaCp* yields [Pt2(GaCp*)2(μ2-GaCp*)3] (4a) and [PtPd(GaCp*)(μ2-GaCp*)3] (5a). Intermediates of this dimerization reactions, i.e., [Pt2(GaCp*)(μ2-GaCp*)3(η2-COD)] (4b) and [PtPd(GaCp*)(μ2-GaCp*)3(η2-COD)] (5b), were isolated and characterized by means of variable-temperature NMR spectroscopy.

The preparation of a di-o-phenylene-bridged tridentate PCP donor set is described starting with t-BOCaniline followed by a series of steps that include lithiation, quenching with Pr i 2 PCl, conversion to the phosphine sulfide, and assembling the unsaturated N-heterocyclic carbene unit. After desulfurization, the imidazolinium unit flanked by two phosphine units, represented as [(PCP)H]PF 6 is obtained. Subsequent reaction with group 10 M(0) reagents (Ni(COD) 2 , Pd(PPh 3 ) 4 , and Pt(PPh 3 ) 4 ) generates good yields of the corresponding metal hydride complexes, [(PCP)MH]PF 6 salts (where M ) Ni(II), Pd(II), and Pt(II)). Each of these species has been characterized by elemental analyses, NMR spectroscopy, and X-ray crystallography. All of the structures show that the PCP unit is twisted with respect to the square plane of the d 8 metal complex.Supporting Information Available: Crystallographic data for 3, 7a, 7b, and 7c (CIF files); experimental details for X-ray structure determinations. This information is available free of charge via the Internet at http://pubs.acs.org. OM9000764 (45) Gilbertson, S. R.; Wang, X.