Synthesis, structure, electrochemistry and reactivity of the bis(mu-sigma-stannanediyl)dinickel butterfly cluster [{{(SiMe3)(2)CH}(2)Sn-Ni(eta(5)-Cp)}(2)](Ni-2-Sn-2)

Addition of stannylene [{(SiMe3)(2)CH}(2)Sn:] (2) to the unbridged homobime tallic Ni-Ni bond of [{PEt3Ni(eta(5)-Cp)}(2)] (1) gives the heterobimetalli c, tetranuclear compound [{{(SiMe3)(2)CH}(2)Sn-Ni(eta(5)-Cp)}(2)] (3) with a butterfly arrangement and leaves the Ni-Ni bond of 1 intact. Elimination of both PEt3 ligands from the starting material 1 is observed, probably due to steric restraints. Compound 3 is formally related to the hypothetical c loso-borane B4H42-, The Ni-Ni bond in 3 is only slightly elongated [2.454(3 ) Angstrom] when compared to the starting material 3. [2.41(1) A]. Compound 3 displays a butterfly arrangement with a hinge angle of 62.5 degrees. An alternative route to 3 is by a direct reaction between nickelocene (5) and Lappert's stannylene [{(SiMe3)(2)CH}(2)Sn:] in 63% yield. Treating 3 with w ater results in the cleavage of an Ni-Sn bond and subsequent opening of the cluster cage of 3 to form the trinuclear compound [(eta 5-Cp)Ni{Sn(CH(SiMe 3)(2)}(2)OH] (6) having an Sn-OH-Sn bridge. The hydroxy proton in 6 can be exchanged by deuterium within a few minutes, as determined by H-1-NMR spect roscopy, giving the monodeuterio product, [D-1]-6. Compound 6 is reactive t owards acetonitrile, leading to cleavage of one Ni-Sn bond, elimination of one [{(SiMe3)(2)CH}(2),Sn:] unit, and formation of the organotin hydroxo co mplex [{(SiMe3)(2)CH}(2)(OH)Sn-Ni(eta(5)-Cp)(CH3CN)] (7). In this complex, acetonitrile is coordinated to Ni via its sigma lone pair, bearing the OH l igand in a terminal bonding mode to tin.