SYNTHESIS, STRUCTURE, AND REACTIONS OF A BIMETALLACYCLIC CARBENE COMPLEX OF RUTHENIUM, RUBR2(CO)[=C(C6H4PPH2)2]

Reaction of Ru(CF3)Br(CO)2(PPh3)2 with an excess of BBr3 produces a red salt identified as [RuBr(CO)2C(C6H4PPh2)2]BBr4. Upon standing this solid loses CO and BBr3, to form RuBr2(CO)[C(C6H4PPh2)2], A, the structure of which has been determined by X-ray diffraction. The geometry about ruthenium is approximately octahedral, with the two phosphorus atoms of the tridentate biphosphinocarbene ligand mutually trans, and one bromide trans to the carbene carbon. The other bromide and the carbonyl ligand are statistically interchanged about a crystallographic diad axis which passes through the carbene carbon, the ruthenium, and the trans bromide. The RuP distance is 2.353(2) Å, the RuBr distances are 2.638(2) Å (trans to carbene) and 2.537(2) Å (trans to CO), and the RuC(carbene) distance is 1.941(12) Å. Bromide is removed from compound A by treatment with AgSbF6 in MeCN to give [RuBr(CO)(CH3CN)C(C6H4PPh2)2]SbF6, and this when treated with CO gives [RuBr(CO)2C(C6H4PPh2)2]SbF6. The dicarbonyl cation reacts with NaBH4 to give Rubr(CO)2[CH(C6H4PPh2)2], and with HNEt2 to give RuBr(CO)2[C(NEt2)(C6H4PPh2)2]. © 1990.