Metal‐Rich Metallaboranes: Structures and Geometries of Heterometallic µ 9 ‐Boride Clusters

Treatment of a dirhodium analogue of pentaborane(9), [(Cp*Rh) 2 B 3 H 7 ] ( nido ‐ 1 ; Cp* = η 5 ‐C 5 Me 5 ), with [Fe 2 (CO) 9 ] at room temperature led to the formation of [(Cp*Rh) 2 Fe(CO) 3 (µ‐CO)B 3 H 2 Cl] ( 2 ) and the metal‐rich metallaborane [(Cp*Rh) 2 Fe(CO) 3 Fe(CO) 2 (µ‐CO) 2 B 2 H 2 ] ( 3 ). When the same reaction was carried out at moderate temperature, two metal‐rich metallaboranes, [(Cp*Rh) 3 Fe(CO) 2 (µ 3 ‐CO) 2 B 2 HX] 4 (X = H) and 5 (X = Cl), and a heterometallic µ 9 ‐boride cluster, [(Cp*Rh) 3 (RhCO) 3 Fe(CO) 3 (µ‐CO) 3 B 3 H 2 ] ( 6 ), were obtained. Compounds 4 and 5 can be viewed as cubane clusters with 62 cluster valence electrons (cves) and five metal–metal bonds. In another reaction, the treatment of nido ‐ 1 with [Mn 2 (CO) 10 ] yielded the heterometallic µ 9 ‐boride cluster [(Cp*Rh) 3 Rh(CO) 2 {Mn(CO) 3 } 2 B 4 H 3 ] ( 7 ). The cluster cores of both 6 and 7 are comprised of tricapped trigonal prisms containing a µ 9 ‐B atom bonded to seven/six metals and two/three boron atoms, respectively. All the new compounds have been characterized by mass spectrometry, IR, 1 H, 11 B{ 1 H}, and 13 C{ 1 H} NMR spectroscopy, and X‐ray crystallographic analysis.