Design, Synthesis, and Chemistry of Bis(σ)borate and Agostic Complexes of Group 7 Metals. Issue 41 (9th June 2017) - Saha, Koushik
Abstract: A series of new bis(σ)borate and agostic complexes of group 7 metals have been synthesized and structurally characterized from various borate ligands, such as trihydrobis(benzothiazol‐2‐yl)amideborate (Na[(H3 B)bbza]), trihydro(2‐aminobenzothiazolyl)borate (Na[(H3 B)abz]), and dihydrobis(2‐mercaptopyridyl)borate (Na[(H2 B)mp2 ]) (bbza=bis(benzothiazol‐2‐yl)amine, abz=2‐aminobenzothiazolyl, and mp=2‐mercaptopyridyl). Photolysis of [Mn2 (CO)10 ] with Na[(H3 B)bbza] formed bis(σ)borate complex [Mn(CO)3 (μ‐H)2 BHNCSC6 H4 (NR)] (1 ; R=NCSC6 H4 ). Octahedral complex [Re(CO)2 (N3 C2 S2 C12 H8 )2 ] (2 ) was generated under similar reaction conditions with [Re2 (CO)10 ]. Similarly, when [Mn2 (CO)10 ] was treated with Na[(H3 B)abz], bis(σ)borate complex [Mn(CO)3 (μ‐H)2 BH(HN2 CSC6 H4 )] (3 ) and the agostic complex [Mn(CO)3 (μ‐H)BH(HN2 CSC6 H4 )2 ] (4 ) were formed. To probe the potential formation of agostic complexes of the heavier group 7 metals, we carried out the photolysis of [M2 (CO)10 ] with Na[(H2 B)mp2 ] and found that [M(CO)3 (μ‐H)BH(C5 H4 NS)2 ] (5 : M=Re;6 : M=Mn) was formed in moderate yield. Complexes1 and3 feature a (κ 3 ‐H, H, N) coordination mode, whereas4, 5, and6 display both (κ 3 ‐H, N, N) and (κ 3 ‐H, S, S) modes of the corresponding ligands. To investigate the lability of the CO ligands of1 and3, we treated the complexes with phosphine ligands that generated novel bis(σ)borate complexes [Mn(μ‐H)2 (BHNCSC6 H4 )(NR)(CO)2 PL2 L'] (R=NCSC6 H4 ;7 a : L=L'=Ph;7 b : L=Ph, L'=Me) and [Mn(μ‐H)2 BHN(NCSC6 H4 )R(CO)2 PL2 L'] (R=NCSC6 H4 ;8 a : L=L'=Ph;8 b : L=Ph, L'=Me). Complexes7 and8 are structural isomers with different coordination modes of the bbza ligand. In addition, DFT calculations were performed to shed some light on the bonding and electronic structures of these complexes. Abstract : Let it B : Several borate ligands with group 7 metals that show novel structures, bonding, and reactivities were synthesized. In addition, some bis(σ)borate complexes reacted with phosphines and led to the isolation of isomeric borate complexes (see scheme).