Polynuclear Magnesium and Magnesium−Titanium Species. Syntheses and Crystal Structures of [Mg\\r <sub/>4sub>\\r (μ\\r <sub/>3sub>\\r ,η\\r <sup>2sup>\\r -ddbfo)\\r <sub/>2sub>\\r (μ,η\\r <sup>2sup>\\r -ddbfo)\\r <sub/>2sub>\\r (μ,η\\r <sup>1sup>\\r -ddbfo)\\r <sub/>2sub>\\r (η\\r <sup>1sup>\\r -ddbfo)\\r <sub/>2sub>\\r ], [Mg\\r <sub/>4sub>\\r (μ\\r <sub/>3sub>\\r -OMe)\\r <sub/>2sub>\\r (μ,η\\r <sup>2sup>\\r -ddbfo)\\r <sub/>2sub>\\r (μ,η\\r <sup>1sup>\\r -ddbfo)\\r <sub/>2sub>\\r (η\\r <sup>1sup>\\r -ddbfo)\\r <sub/>2sub>\\r (CH\\r <sub/>3sub>\\r OH)\\r <sub/>5sub>\\r ], and [Mg\\r <sub/>4sub>\\r (μ\\r <sub/>3sub>\\r ,η\\r <sup>2sup>\\r -thffo)\\r <sub/>2sub>\\r (μ,η\\r <sup>2sup>\\r -thffo)\\r <sub/>2sub>\\r (μ,η\\r <sup>1sup>\\r -thffo)\\r <sub/>2sub>\\r {μ-OTi(DIPP)\\r <sub/>3sub>\\r }\\r <sub/>2sub>\\r ] Aggregates