Versatile reactivity of half-sandwich Ir and Rh complexes toward carboranylamidinates and their derivatives: synthesis, structure, and catalytic activity for norbornene polymerization

Synthesis, structure, and reactivity of carboranylamidinate‐based half‐sandwich iridium and rhodium complexes are reported for the first time. Treatment of dimeric metal complexes {Cp*M(μ‐Cl)Cl}₂] (M=Ir, Rh; Cp*=η⁵‐C₅Me₅) with a solution of one equivalent of nBuLi and a carboranylamidine produces 18‐electron complexes Cp*IrCl(Cab^N‐DIC)] ( 1 a ; Cab^N‐DIC=iPrN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHiPr)]), Cp*RhCl(Cab^N‐DIC)] ( 1 b ), and Cp*RhCl(Cab^N‐DCC)] ( 1 c ; Cab^N‐DCC=CyN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHCy)]). A series of 16‐electron half‐sandwich Ir and Rh complexes Cp*Ir(Cab^N′‐DIC)] ( 2 a ; Cab^N′‐DIC=iPrN?C(closo‐1,2‐C₂B₁₀H₁₀)(NiPr)]), Cp*Ir(Cab^N′‐DCC)] ( 2 b , Cab^N′‐DCC=CyN?C(closo‐1,2‐C₂B₁₀H₁₀)(NCy)]), and Cp*Rh(Cab^N′‐DIC)] ( 2 c ) is also obtained when an excess of nBuLi is used. The unexpected products Cp*M(Cab^N,S‐DIC)], Cp*M(Cab^N,S‐DCC)] (M=Ir 3 a , 3 b ; Rh 3 c , 3 d ), formed through BH activation, are obtained by reaction of {Cp*MCl₂}₂] with carboranylamidinate sulfides RN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHR)]S^? (R=iPr, Cy), which can be prepared by inserting sulfur into the C? Li bond of lithium carboranylamidinates. Iridium complex 1 a shows catalytic activities of up to 2.69×10⁶ g_PNB ${{\rm{mol}}_{{\rm{Ir}}}^{ - {\rm{1}}} }Synthesis, structure, and reactivity of carboranylamidinate-based half-sandwich iridium and rhodium complexes are reported for the first time. Treatment of dimeric metal complexes {Cp*M(μ-Cl)Cl}(2)] (M = Ir, Rh; Cp* = η(5)-C(5)Me(5)) with a solution of one equivalent of nBuLi and a carboranylamidine produces 18-electron complexes Cp*IrCl(Cab(N)-DIC)] (1?a; Cab(N)-DIC = iPrN=C(closo-1,2-C(2)B(10)H(10))(NHiPr)]), Cp*RhCl(Cab(N)-DIC)] (1?b), and Cp*RhCl(Cab(N)-DCC)] (1?c; Cab(N)-DCC = CyN=C(closo-1,2-C(2)B(10)H(10))(NHCy)]). A series of 16-electron half-sandwich Ir and Rh complexes Cp*Ir(Cab(N')-DIC)] (2?a; Cab(N')-DIC = iPrN=C(closo-1,2-C(2)B(10)H(10))(NiPr)]), Cp*Ir(Cab(N')-DCC)] (2?b, Cab(N')-DCC = CyN=C(closo-1,2-C(2)B(10)H(10)(NCy)]), and Cp*Rh(Cab(N')-DIC)] (2?c) is also obtained when an excess of nBuLi is used. The unexpected products Cp*M(Cab(N,S)-DIC)], Cp*M(Cab(N,S)-DCC)] (M = Ir 3?a, 3?b; Rh 3?c, 3?d), formed through BH activation, are obtained by reaction of {Cp*MCl(2)}(2)] with carboranylamidinate sulfides RN=C(closo-1,2-C(2)B(10)H(10))(NHR)]S(-) (R = iPr, Cy), which can be prepared by inserting sulfur into the C-Li bond of lithium carboranylamidinates. Iridium complex 1?a shows catalytic activities of up to 2.69×10(6) g(PNB) mol(Ir)(-1) h(-1) for the polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst. Catalytic activities and the molecular weight of polynorbornene (PNB) were investigated under various reaction conditions. All complexes were fully characterized by elemental analysis and IR and NMR spectroscopy; the structures of 1?a-c, 2?a, b; and 3?a, b, d were further confirmed by single crystal X-ray diffraction.