Unexpectedly different reactions of [(arene)Mn(CO)3]+ cations (arene = trindane, indane, tetralin, or dibenzosuberane) with potassium t-butoxide C-H insertions, haptotropic shifts, dimerization, or elimination

[(η 6 -Trindane)Mn(CO) 3 ][BF 4 ] ( 1 ) reacts with tert-BuOK in THF in the presence of alkyl halides (CH 2 =CHCH 2 Br, CH 3 I) to yield the corresponding (η 6 -C 15 H 18 )Mn(CO) 2 X, where X = Br ( 3 ) or I ( 4 ). In contrast, 1 and tert-BuOK react, in the presence of a donor ligand, to generate (η 5 -C 15 H 15 )Mn(CO) 2 L, where L = CO ( 7 ), P(OMe) 3 ( 8 ), or PPh 3 ( 9 ), in which the metal has migrated from the central ring onto a peripheral ring that has lost three hydrogens; [(η 6 -indane)Mn(CO) 3 ][BF 4 ] behaves similarly. A mechanism is proposed in which the initially formed (η 6 -trindane)Mn(CO) 2 CO 2 -tert-Bu suffers the loss of CO 2 and isobutene to yield the hydride, (η 6 -trindane)Mn(CO) 2 H, that in turn undergoes three successive C-H insertions with concomitant loss of two molecules of dihydrogen. In contrast, [(η 6 -tetralin)Mn(CO) 3 ][PF 6 ] ( 17 ) and [(η 6 -dibenzosuberane)Mn(CO) 3 ][BF 4 ] ( 23 ) each suffer deprotonation at a benzylic site. In the first case, the zwitterion formed attacks its progenitor to yield a tetralenyl-substituted (η 5 -cyclohexadienyl)Mn(CO) 3 complex ( 21 ); however, for the dibenzosuberane complex ( 23 ) the elimination product ( 28 ) is stable. X-ray crystal structures are reported for 3 , 4 , 7 , 8 , 23 , 28 , and for the phosphite complexes [(η 6 -trindane)Mn(CO){P(OMe) 3 } 2 ][BF 4 ] ( 15 ) and [(η 6 -tetralin)Mn(CO) 2 {P(OMe) 3 }][PF 6 ] ( 20 ).Key words: arene-manganese, organometallic cations, deprotonations, X-ray crystallography.