1423actual dissociation (AD2 -AD + D) in which the leaving molecule carries away the excess energy. SummaryThe emission properties of jet-cooled adducts between ethers and some aromatic hydrocarbons may be accounted for by assuming an excited state that is a superposition of a van der Waals locally excited (LE) state and a charge-transfer (CT) state. The direct optical transition from the ground state to the C T state is forbidden by either symmetry or Franck-Condon considerations. Thus, the excitation spectrum is dominated by the LE state, and emission from the CT state has a longer decay time. The C T character of the excited state is more prominent in anthracene and its derivatives than in perylene. This is particularly so when a hydrogen atom is bound to a C-9 or C-IO carbon. It is therefore proposed that this atom may serve as a bridge in transmitting the charge from the oxygen lone pair orbital of the ether. Geometric factors appear to be decisive in determining the interaction as shown by the fact that tetrahydrofuran, in which the oxygen atom is constrained to be away from the 9-or 10-position, does not show exciplex-type emission with anthracene. Abstract:The reaction between W(C-t-Bu)(dme)CI, and ArNH(TMS) (Ar = 2,6-C,H3-i-Pr2) yields W(C-t-Bu)(NHAr)(dme)CI,.

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Dinuclear ~helatesfac-L~Re(CO)~[M(CO)~] (L2 = 2-pyridyl dimethylphosphinite, 2, M = Re; 3, M = Mn) rearranged in benzene at 80 OC to provide the corresponding (CO),Re(p-OPYR)(p-PMe,)M(C0)4 derivatives 5 (M = Re) and 6 (M = Mn) in 95 and 94% yield, respectively. The rearrangements exhibited first-order kinetics to >3 half-lives and displayed the following kinetic parameters: M = Re, AH* = 24.2 i 1.8 kcal/mol and pS* = -10 i 5 eu; M = Mn, AH* = 22.2 f 0.7 kcal/mol and AS" = -1 1 i 2 eu. The reaction rates and the products formed were unaffected by added CO, methylating agents, or triphenylphosphine. In the presence of carbon tetrachloride, the rearrangements afforded mixtures of the P-O cleavage products (5 or 6 ) andfac-(CO),L,ReCl. Crossover studies showed the rearrangements of 2 and 3 to occur with statistically significant inter-and intramolecular components. The results are discussed in light of mechanisms involving CO dissociation, homo-and heterolytic metal-metal bond cleavage, and a novel dyotropic rearrangement.Reports of the cleavage of phosphorus-carbon bonds by transition metals have received considerable attention recently because of their potential roles in the deactivation of homogeneous catalysts.' In contrast, the corresponding cleavages of phosphorusoxygen bonds in transition-metal phosphite complexes have been detailed on only a few occasions.2 Presumably this derives, in part, from the large ( 1 8 0 kcal/mol) P-0 bond e n e r g i e~.~ Nonetheless, we recently reported a notably facile cleavage of the P-0 bond of 2-pyridyl dimethylphosphinite (1) by CpCo-(CH2=CH2)2.4 In this paper we describe mechanistic studies of similar cleavages occurring on group 7 dinuclear frameworks. ResultsStarting Materials and Products. During studies of the chemistry of complexes of ligand 1,5 we prepared dinuclear complexes 2 and 3 as follows. Heating (C0)5ReBr6 with 1 .O equiv of ligand 1 in toluene for 15 min at 1 IO O C afforded fac isomeric complex 4 in an 88% yield after recrystallization. The fac stereochemistry was evident from the distinct resonances in the I3C and 'H NMR spectra of 4 for the diastereotopic methyl groups. When 4 was treated with NaRe(CO)S7 in T H F at 25 O C , dirhenium chelate 2 could be isolated in a 49% yield after recrystallization. Again, diastereotopic methyl resonances demonstrated the retention of the fac stereochemistry. The 3'P N M R spectrum of 2 showed a single resonance at 139.6 ppm. Heterodinuclear chelate 3 could be prepared in a 44% yield after recrystallization by treatment of 4 with (CO),MnNa8 in THF. The spectroscopic analysis of 3 proceeded analogously to 2. (9) Jones, R. A.; Wright, T. C.; Atwood, J. L.; Hunter, W. E. Organometallics 1983, 2, 470. Rosen, R. P.; Hoke, J. B.; Whittle, R. R.; Geoffroy, G. L.; Hutchinson, J. P.; Zubieta, J.Abstract The abstraction of benzylic hydrogen by bromine atom from toluene and 4-chlorotoluene has been studied by measuring the relative rates at 45.0,25.0 10.0, 0.0, -18.5, -32.0, and -50.0 "C. The rates of 3-chloro-, Cbrome, 4-methyl-, ...