Preparation of (1,4,7-triazacyclononane)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)RhCl 3 ·H 2 O 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)RhCl 3 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 HSO 3 CF 3 (HOTf) affords (tacn)RhR(OTf) 2 . Dissolution of the latter in D 2 O gives [(tacn)RhR(D 2 O) 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 NaBH 4 or KBH 4 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[C 6 H 3 -3,5-(CF 3 ) 2 ] 4 } (NaBAr F 4 ) yielding [(tacn)Rh(H)R(PMe 3 )](BAr F 4 ). Heating of [CnRh(H)Et(PMe 3 )]X (X = OTf or BAr F 4 ), [(tacn)Rh(H)Et(PMe 3 )]X, and [(tacn)Rh(H)Me(PMe 3 )]X in C 6 D 6 leads to formation of [(Cn/tacn)Rh(D)(C 6 D 5 )(L)]X in high yield in all cases. The half-lives of these cleanly first-order reactions at 80 °C are 1 min, 1.2 h, and 7.3 h, respectively, illustrating alkyl hydride thermal stabilities unprecedented in rhodium chemistry.