Chemistry of Triple‐Decker Sandwich Complexes Containing Four‐Membered Open B2E2 Rings (E = S or Se). Issue 19 (17th May 2018) - Joseph, Benson
Abstract : Building upon our earlier studies of cobaltaheteroboranes, we explore the chemistry with heavier group 9 metals. Reaction of [Cp*M(µ‐Cl)Cl x ]2 (Cp* = η 5 ‐C5 Me5 ; M = Co, x = 0; M = Rh or Ir, x = 1) with [LiBH4 · THF], followed by thermolysis with an excess of chalcogen powders (S or Se), affords dimetallaheteroboranes nido ‐[(Cp*M)2 B2 H2 E2 ], 1 –4 (1 : E = S;2 : E = Se, M = Co;3 and4 : E = Se, M = Rh and Ir, respectively) in moderate‐to‐good yields. The solid‐state structures of these compounds show open‐cage triple‐decker clusters. Attempts to isolate the Te analogue have failed; however, in the case of cobalt, we have isolated an 11 skeletal‐electron‐pair nido ‐[(Cp*Co)2 B5 H5 Te2 ], 5 . The X‐ray diffraction structure of5 shows monocapped square antiprismatic geometry, with two Te atoms in the core. To close the central four‐membered B2 E2 open ring of nido ‐1 and nido ‐2, we have performed a reaction with [Ru3 (CO)12 ], which leads to the formation of closo ‐[(Cp*Co){µ‐η 5 :η 5 ‐B2 H2 E2 M}M{µ‐Ru(CO)4 }], 6 and7 [6 : E = S;7 : E = Se; M = Ru(CO)2 ]. In contrast, the reactions of nido ‐2 and nido ‐3 with [Fe2 (CO)9 ] result in heterometallic clusters nido ‐[(Cp*M)Fe(CO)3 B2 H2 Se2 ], 8 and9 (8 : M = Co;9 : M = Rh), [(Cp*Co)Fe3 (CO)8 Se2 ], 10, and [(Cp*Co)Fe2 (CO)7 Se], 11 . As nido ‐8 also contains a four‐membered open ring B2 Se2, we have treated this with [Ru3 (CO)12 ], which yields closo ‐[(Cp*Co){µ‐η 5 :η 5 ‐B2 H2 Se2 M}M{µ‐Fe(CO)4 }], 12 [M = Ru(CO)2 ], which is analogous to that of7 . In addition, we have analyzed the divergence in the reactivity of nido ‐[(Cp*M)2 B2 H2 E2 ], 2 –4, with the help of density functional theory calculations. Abstract : The synthesis of group 9 triple‐decker‐sandwich metallaheteroboranes containing four‐membered open B2 E2 central rings (E = S or Se) is described. Further, the reactivity of these molecules with group 8 metal–carbonyl compounds is carried out, yielding closo‐polyhedral metallaheteroboranes.