Synthesis and ligand substitution of tri-metallic triply bridging borylene complexes.

To build upon our earlier results of heterometallic metallaboranes employing metal carbonyls, we performed the reaction of nido -[(Cp*Rh) 2 B 3 H 7 ] ( 1 ) ( nido - 1 ) with [M(CO) 5 ·THF] (M = Mo or W) that yielded the trimetallic metallaborane clusters [(Cp*Rh) 2 M(CO) 3 (μ-CO)(μ 3 -BH)(B 2 H 4 )] ( 3 : M = Mo; 4 : M = W) having a capped borylene fragment and trimetallic triply bridging borylene complexes [(Cp*Rh) 2 (μ 3 -BH)(μ-CO)M(CO) 5 ] ( 5 : M = Mo; 6 : M = W). The chemistry of trimetallic triply bridging borylene complexes ( 5 and 6 ) were explored with Lewis bases such as tert- butyl isocyanide and bisphosphine ligands. Photolysis of 5 and 6 with tert -butyl isocyanide yielded [(Cp*Rh) 2 (μ 3 -BH)(μ-CO)M(CO) 4 (CN- t Bu)] ( 7 : M = Mo; 8 : M = W) and with phosphines, PPh 2 (CH 2 ) n PPh 2 (n = 1, 2) they resulted in the formation of [(Cp*Rh) 2 (μ 3 -BH)(μ-CO)M(CO) 4 ((PPh 2 ) 2 (CH 2 ) n )] ( 9 : n = 1, M = Mo; 10 : n = 1, M = W; 11 : n = 2, M = Mo; 12 : n = 2, M = W). All the new compounds have been characterized in solution by mass spectrometry and NMR spectroscopic techniques. The structural aspects were unambiguously established by X-ray crystallographic analysis of 3 – 4 and 7 – 10 . [ABSTRACT FROM AUTHOR]