Alkyl and Aryl Compounds of Rhodium(III) and Iridium(III) Supported by 4,4‘-Di-tert-butyl-2,2‘-bipyridyl

Abstract

Alkylation of Rh(dtbpy)Cl3(DMF) (1) (dtbpy = 4,4‘-di-tert-butyl-2,2‘-bipyridyl, DMF = N,N-dimethylformamide) with PhMe2CCH2MgCl afforded the cyclometalated neophyl compound (2), which reacted with CO to give the adduct (3). The solid-state structure of 2 shows an agostic interaction between Rh and an ortho phenyl C−H group of the neophyl ligand. Alkylation of 1 with Me3SiCH2MgCl gave the dialkyl compound Rh(dtbpy)(CH2SiMe3)2Cl (4), which reacted with PPh3 to give Rh(dtbpy)(CH2SiMe3)2(Cl)(PPh3) (5). Transmetalation of M(dtbpy)Cl3(DMF) with C8H9MgBr (C8H9 = 2,5-dimethylphenyl) afforded the triaryl compounds M(dtbpy)(C8H9)3 (M = Rh (6), Ir (7)), which have pseudo-square-pyramidal geometry with one aryl group at the apical position. Reaction of 7 with 2,6-dimethylphenyl isocyanide (xylNC) afforded six-coordinated Ir(dtbpy)(C8H9)3(xylNC) (8). The cyclic voltammogram of 7 in CH2Cl2 shows a reversible couple at ca. 0.18 V versus ferrocenium−ferrocene that is tentatively assigned as the Ir(IV/III) couple. Treatment of 7 with Ag(OTf) (OTf- = triflate) in tetrahydrofuran (THF) afforded [Ir(dtbpy)(C8H9)3{Ag(OTf)(THF)}{Ag2(OTf)2}3]∞ (9), which has a double-chain polymeric structure in the solid state. Transmetalation of Ir(dtbpy)Cl3(DMF) with (ArF)MgBr (ArF = 3,5-bis(trifluoromethyl)phenyl) afforded the mono-aryl compound Ir(dtbpy)(ArF)(DMF)Cl1.4Br0.6 (10), which reacted with xylNC to give Ir(dtbpy)(ArF)(DMF)Cl1.4Br0.6(xylNC) (11). The crystal structures of 2, 6−9, and 11 have been determined.