Borylene Transfer under Thermal Conditions: Synthesis and Structure of a Tetrarhodium Bisborylene Complex

All good things come in fours: Thermal metal–metal borylene transfer from the terminal borylene complexes [(OC)5MBN(SiMe3)2] (M=Cr, W) leads to the new tetranuclear rhodium complex [Rh4{μ-BN(SiMe3)2}2(μ-Cl)4(μ-CO)(CO)4] (see structure), which is the first doubly borylene-bridged transition-metal complex. In the solid state, the tetranuclear units aggregate (dashed lines), giving a rare example of a neutral chain of rhodium atoms.