In search for new bonding modes of the methylenedithiolato ligand: novel tri- and tetra-metallic clusters

Abstract

Building upon our earlier results on the chemistry of diruthenium analogue of pentaborane (9) with heterocumulenes, we continued to investigate the reactivity of arachno-[(Cp*Ru)₂(B₃H₈)(CS₂H)], 1, (Cp* = η⁵-C₅Me₅) towards group 7 and 8 transition metal carbonyl compounds under photolytic and thermolytic conditions. The metal carbonyl compounds show diverse reactivity pattern with arachno-1. For example, the photolysis of arachno-1 with [Re₂(CO)₁₀] yielded [(Cp*Ru)₂B₃H₅ (CH₂S₂){Re(CO)₄}₂], 2, [(Cp*RuCO)₂ (μ-H)₂(CH₂S₂){Re(CO)₄}{Re(CO)₃}], 3 and [(Cp*Ru)₂(μ-CO)(μ-H)(CH₂S₂){Re(CO)₃}], 4. The geometry of 2 with a nearly planar eight-membered ring containing heavier transition metals rhenium, ruthenium is unprecedented. Compounds 3 and 4 can be considered as M₄-quadrilateral and M₃-triangle with a methylenedithiolato ligand attached to the metal centres, respectively. [Mn₂(CO)₁₀], on the other hand, reacts with arachno-1 to yield heterometallic binuclear [(Cp*RuCO){Mn(CO)₄}(μ-H)(SCH₃)], 5 and homocubane [(Cp*Ru)₂{Mn(CO)₃}-(CS₂H₂)B₃H₄], 6. In an attempt to generate group 8 analogues of 2–5, we performed the reaction of arachno-1 with [Fe₂(CO)₉] and [Ru₃(CO)₁₂]. Although, the objective of isolating analogous compounds was not achieved, the reaction with [Fe₂(CO)₉] led to novel tetrahedral cluster [(Cp*RuCO){(Fe(CO)₃}₂S(μ-H)], 7. [Ru₃(CO)₁₂], in contrast, yielded known compounds [{Cp*Ru(CO)}₂B₂H₆], 9 and [Cp*Ru(CO)₂]₂, 10. All the cluster compounds have been characterized by mass spectrometry, IR, and ¹H, ¹¹B and ¹³C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis of 2–5 and 7.