A Basis Set of Re6Se8 Cluster Building Blocks and Demonstration of Their Linking Capability: Directed Synthesis of an Re12Se16 Dicluster

A previously developed solid-state route (dimensional reduction) has led to the first molecular clusters containing the face-capped octahedral [Re6(μ3-Q)8]2+ core (Q = S, Se). Among these is the protonated cluster [Re6Se7(SeH)I6]3-, whose substitution reactions have been examined in an effort to create a set of site-differentiated precursors for forming multicluster assemblies. Reaction with Et3P under reflux with different conditions of reactant mole ratio and time affords the clusters fac-[Re6Se8(PEt3)3I3]1- (2), trans- (3) and cis-[Re6Se8(PEt3)4I2] (4), [Re6Se8(PEt3)5I]1+ (5), and [Re6Se8(PEt3)6]2+ (6). The synthesis of fully substituted 6 in quantitative yield required the forcing conditions of 20 equiv of phosphine in refluxing DMF for 3 days. Reaction of 4 with AgBF4 in dichloromethane/acetonitrile gave cis-[Re6Se8(PEt3)4(MeCN)2]2+ (7); a similar reaction of 5 yielded [Re6Se8(PEt3)5(MeCN)]2+ (8) and that of [Re6Se7(SeH)I6]3- led to fully substituted [Re6Se8(MeCN)6]2+ (9). The structures of clusters ...