Preparation of (1,4,7-triazacyclollonane)Rh(hydrocarbyl)(3) compounds and their derivatives. Strong donor labilization of RhCl bonds toward alkylation and preparation of unusually stable alkyl hydride complexes of rhodium

(tacn)Rh(R)(3) compounds (tacn = 1,4,7-triazacyclononane; R = Me, Et, Ph, vinyl)have been prepared in 65-86% yields by treatment of(tacn)RhCl3 . H2O with more than a 7-fold molar quantity of RLi in THF, followed by protonation by methanol. The product before protonation is (Li(3)tacn)RhR(3) (Li(3)tacn = 1,4,7-trilithio-1,4,7-triazacyclononane) which can be isolated. The alkylation is complete in a few minutes to a couple of hours, depending on R, which compares with 3-4 days for CnRhCl(3) with MeLi (Cn = 1,4,7-trimethyl-1,4,7-triazacyclononane) and suggests that the presumably first-formed (Li(3)tacn)RhCl3 is highly activated toward Cl- dissociation by the strong donor effect of the three LiNR(2) groups in the rhodium coordination sphere. Protonation of(Li(3)tacn)RhR(3) by methanol gives the neutral products (tacn)RhR(3). X-ray structure determinations of (tacn)RhEt(3) and (tacn)RhPh(3) have been carried out. Protonolysis of(tacn)RhR(3) (R = Me, Et, Ph) by 2 HSO3CF3 (HOTf) affords (tacn)RhR(OTf)(2). Dissolution of the latter in D2O gives [(tacn)RhR(D2O)(2)](OTf)(2), which on standing for up to 2 days undergoes H/D exchange of the two NH groups trans to the aqua ligands. Treatment of (tacn)RhR(OTf)(2) with 1 equiv of PMe(3) followed by NaBH4 or KBH4 yields a mixture of [(tacn)Rh(H)R(PMe(3))](OTf) and [(tacn)Rh(H)(2)(PMe(3))](OTf) which is separated by benzene extraction. Counterion exchange has been carried out where R = Me and Et with Na{B[C6H3-3,5-(CF3)(2)](4)} (NaBAr4F) yielding [(tacn)Rh(H)R(PMe(3))](BAr4F). Heating of [CnRh(H)Et(PMe(3))]X (X = OTf or BAr4F), [(tacn)Rh(H)Et(PMe(3))]X, and [(tacn)Rh(H)Me(PMe(3))]X in C6D6 leads to formation of [(Cn/tacn)Rh(D)(C6D5)(L)]X in high yield in all cases. The half-lives of these cleanly first-order reactions at 80 degrees C are 1 min, 1.2 h, and 7.3 h, respectively, illustrating alkyl hydride thermal stabilities unprecedented in rhodium chemistry.