Reactions and properties of the dinuclear molybdenum complex [(η5-C5H3)2(CMe2)(SiMe2)]Mo2(CO)6

Abstract Reactions of the title complex ( 1 ), which features the rigid doubly-bridged biscyclopentadienyl ligand and the unusually long Mo–Mo bond in the structure, with a variety of classic substrates are explored. Complex 1 reacts with I 2 in CH 2 Cl 2 to give the expected Mo–Mo cleaved product [( η 5 -C 5 H 3 ) 2 (CMe 2 )(SiMe 2 )]Mo 2 (CO) 6 I 2 ( 2A ) with a Mo–Mo distance of 5.329 A. While the same reaction in benzene forms the product 2B , which has the same structural formula as 2A but a different conformation, in which the Mo–Mo distance is 6.442 A. Reaction of 1 with Ph 2 E 2 (E = S, Se) in refluxing toluene or under UV irradiation yields products with the carbonyls completely removed, [( η 5 -C 5 H 3 ) 2 (CMe 2 )(SiMe 2 )]Mo 2 (EPh) 2 ( μ -EPh) 2 ( 3a – b ). Reaction of 1 with [Et 2 NC(S)S] 2 results in the di-substituted product [( η 5 -C 5 H 3 ) 2 (CMe 2 )(SiMe 2 )]Mo 2 (CO) 4 (Et 2 NC(S)S) 2 ( 4 ). Reaction of 1 with C 2 Ph 2 affords the acetylene-bridged derivative [( η 5 -C 5 H 3 ) 2 (CMe 2 )(SiMe 2 )]Mo 2 (CO) 4 ( μ -C 2 Ph 2 ) ( 5 ). Reaction of 1 with an excess of PPh 3 in refluxing toluene only provides the mono-substituted derivative [( η 5 -C 5 H 3 ) 2 (CMe 2 )(SiMe 2 )]Mo 2 (CO) 5 (PPh 3 ) ( 6 ), while the reaction of 1 with excess P(OPh) 3 under the same conditions produces not only the mono-substituted derivative [( η 5 -C 5 H 3 ) 2 (CMe 2 )(SiMe 2 )]Mo 2 (CO) 5 (P(OPh) 3 ) ( 7 ), but also the di-substituted derivative [( η 5 -C 5 H 3 ) 2 (CMe 2 )(SiMe 2 )]Mo 2 (CO) 4 (P(OPh) 3 ) 2 ( 8 ). The reactivity and properties of the doubly-bridged molybdenum complex 1 and the corresponding non-bridged and singly-bridged analogs are compared. The molecular structures of 2A , 2B , 3a , 5 and 8 have been determined by single crystal X-ray diffraction.