Synthesis and Characterization of Bis(sigma)borate and Bis–zwitterionic Complexes of Rhodium and Iridium

Abstract

Building upon the chemistry of Rh–N,S‐heterocyclic carbene complex, [(Cp*Rh)(L2)(1‐benzothiazol‐2‐ylidene)], 2 (Cp*=η5‐C5Me5; L=C7H4NS2) with various monoboranes‐Lewis adducts, we explored the chemistry of 2 with BH3⋅thf at elevated temperature. As a result, mild thermolysis of 2 with BH3⋅thf led to the formation of bis(sigma)borate [(η4‐C5Me5H)Rh(η2‐H3BL)], 3 and a bis‐zwitterionic species [Cp*RhS(BH2L2)], 4 with the concomitant release of BH3⋅bt (bt=benzothiazole). The RhS3C2N2B2 atoms in 4 generates two six membered rings fused by a common Rh−S bond, which may be considered as a bicycle [4.4.0] cage at the rhodium center. In an effort to generate the iridium analogue of 3, reaction of [Cp*IrCl2]2 with Na[H3B(mbt)] (mbt=2‐mercaptobenzothiazole) was carried out that produced bis(sigma)borate complex [(η4‐C5Me5H)Ir(η2‐H3BL)], 1. The solid state X‐ray structures of 1 and 3 showed that the Cp*H ligand coordinated to the metal center in a η4‐fashion. In compound 3, the methyl group is oriented towards rhodium center, whereas it is away from Ir center in 1. In addition, the DFT computations were performed to shed light on the bonding and electronic structures of these compounds.

Coordination and Hydroboration of Ru(II)‐Borate Complexes: Dihydridoborate vs. Bis(dihydridoborate)

“…The 11 B{ 1 H} NMR shows upfield peak at δ =−0.4 ppm and the 1 H{ 11 B} NMR spectrum showed peaks at δ =5.33 and –3.10 ppm that correspond to BH t and Ir‐ H ‐B protons, respectively. The solid‐state X‐ray structure of 6 , shown in Figure 2b, [ 26 ] displays a κ 3 ‐H,H,S type of coordination of the borate ligand to Ir, very similar to that of 4 , 5 and iridium dihydridoborate species [( η 4 ‐C 5 Me 5 H)Ir( η 2 ‐H 3 Bmbt)] (mbt=2‐mercaptobenzothiazole) [27] …”

“…The solidstate X-ray structure of 6, shown in Figure 2b, [26] displays a k 3 -H,H,S type of coordination of the borate ligand to Ir, very similar to that of 4, 5 and iridium dihydridoborate species [(η 4 -C 5 Me 5 H)Ir(η 2 -H 3 Bmbt)] (mbt = 2-mercaptobenzothiazole). [27] The natural bond orbital (NBO) analyses of 4 and 5 at B3LYP/def2-TZVP level of theory show enhanced BÀ H σdonation on moving from L 1 to L 2 . As a result, the Ru•••H•••B interaction was found to be stronger in 5.…”

Adding to the Family of Copper Complexes Featuring Borohydride Ligands Based on 2-Mercaptopyridyl Units

“…It was this greater flexibility within the ligand structure that opened up the potential for activation at the boron bridgehead and formation of metal-borane (metallaboratrane) complexes [17][18][19][20][24][25][26][27], giving rise to reactivity not observed in the analogous polypyrazolylborate ligands [10][11][12][13][14][15][16]. Over the following twenty years since the first report of hydride migration from the boron center of a scorpionate ligand, a number of research groups have focused on new, more flexible borohydride ligands containing a range of supporting units based on nitrogen [28][29][30][31] and other sulfur heterocycles [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. As part of our research, we have focused on providing new derivative ligand systems.…”

“…The first of the more flexible scorpionate ligands was [Tm] − [hydrotris(methylimidazolyl)borate] (Figure 1; middle) [23]. This new ligand had two major Over the following twenty years since the first report of hydride migration from the boron center of a scorpionate ligand, a number of research groups have focused on new, more flexible borohydride ligands containing a range of supporting units based on nitrogen [28][29][30][31] and other sulfur heterocycles [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. As part of our research, we have focused on providing new derivative ligand systems.…”

Synthesis of Trithia-Borinane Complexes Stabilized in Diruthenium Core: [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3BR}] (R = H or SMe)

“…However, there is still little understanding of how a transition metal can be used to vary the chemistry of metallaborane compounds. In this regard, our group was actively involved in the synthesis of various electron-precise transition metal-boron complexes such as σ-borane [26][27][28][29][30][31], boryl [32,33], triply-bridged trimetallic borylene [34][35][36][37][38], diborane [39], B-agostic [26,27,[40][41][42], and metallaboratrane [26,27,43,44] complexes using of different synthetic precursors. An important aspect is the incorporation of transition metals into the chemistry of p-block elements other than carbon [45][46][47].…”