Polynuclear Magnesium and Magnesium−Titanium Species. Syntheses and Crystal Structures of [Mg\\r sub/4sub\\r (μ\\r sub/3sub\\r ,η\\r sup2sup\\r -ddbfo)\\r sub/2sub\\r (μ,η\\r sup2sup\\r -ddbfo)\\r sub/2sub\\r (μ,η\\r sup1sup\\r -ddbfo)\\r sub/2sub\\r (η\\r sup1sup\\r -ddbfo)\\r sub/2sub\\r ], [Mg\\r sub/4sub\\r (μ\\r sub/3sub\\r -OMe)\\r sub/2sub\\r (μ,η\\r sup2sup\\r -ddbfo)\\r sub/2sub\\r (μ,η\\r sup1sup\\r -ddbfo)\\r sub/2sub\\r (η\\r sup1sup\\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 sup2sup\\r -thffo)\\r sub/2sub\\r (μ,η\\r sup2sup\\r -thffo)\\r sub/2sub\\r (μ,η\\r sup1sup\\r -thffo)\\r sub/2sub\\r {μ-OTi(DIPP)\\r sub/3sub\\r }\\r sub/2sub\\r ] Aggregates