TY - JOUR
T1 - Isomerism in rhodium(I) N,S-donor heteroscorpionates
T2 - Ring substituent and ancillary ligand effects
AU - Blagg, Robin J.
AU - Connelly, Neil G.
AU - Haddow, Mairi F.
AU - Hamilton, Alex
AU - Lusi, Matteo
AU - Orpen, A. Guy
AU - Ridgway, Benjamin M.
PY - 2010/12/28
Y1 - 2010/12/28
N2 - The heteroscorpionate ligands [HB(taz)2(pzR)] - (pzR = pz, pzMe2, pzPh) and [HB(taz)(pz)2]-, synthesised from the appropriate potassium hydrotris(pyrazolyl)borate salt and 4-ethyl-3-methyl-5-thioxo-1,2,4- triazole (Htaz), react with [{Rh(cod)(μ-Cl)}2] to give [Rh(cod)Tx] {Tx = HB(taz)2(pz), HB(taz)2(pzMe2), HB(taz)2(pzPh), HB(taz)(pz)2}; the heteroscorpionate rhodaboratrane [Rh{B(taz)2(pzMe2)} {HB(taz)2(pzMe2)}] is the only isolable product from the reaction of [{Rh(nbd)(μ-Cl)}2] with K[HB(taz)2(pz Me2)]. Carbonylation of the cod complexes gave a mixture of [Rh(CO)2Tx] and [(RhTx)2(μ-CO)3] which reacts with PR3 to give [Rh(CO)(PR3)Tx] (R = Cy, NMe 2, Ph, OPh). In the solid state the complexes are square planar with the particular structure dependent on the steric and/or electronic properties of the scorpionate and ancillary ligands. The complex [Rh(cod){HB(taz)(pz) 2}] has the heteroscorpionate κ2[N 2]-coordinated to rhodium with the B-H bond directed away from the rhodium square plane while [Rh(cod){HB(taz)2(pzMe2)}] is κ2[SN]-coordinated, with the B-H bond directed towards the metal. The complexes [Rh(CO)(PPh3){HB(taz)2(pz)}] and [Rh(CO)(PPh3){HB(taz)2(pzMe2)}] are also κ2[SN]-coordinated but with the pyrazolyl ring cis to PPh 3; in the former the B-H bond is directed towards rhodium while in the latter the ring is pseudo-parallel to the rhodium square plane, as also found for [Rh(CO)2{HB(taz)2(pzMe2)}]. The analogues [Rh(CO)(PR3){HB(taz)2(pzMe2)}] (R = Cy, NMe2) have the phosphines trans to the pyrazolyl ring. Uniquely, [Rh(CO)(PPh3){HB(taz)2(pzPh)}] is κ2[S2]-coordinated. A qualitative mechanism is given for the rapid ring-exchange, and hence isomerisation, observed in solution.
AB - The heteroscorpionate ligands [HB(taz)2(pzR)] - (pzR = pz, pzMe2, pzPh) and [HB(taz)(pz)2]-, synthesised from the appropriate potassium hydrotris(pyrazolyl)borate salt and 4-ethyl-3-methyl-5-thioxo-1,2,4- triazole (Htaz), react with [{Rh(cod)(μ-Cl)}2] to give [Rh(cod)Tx] {Tx = HB(taz)2(pz), HB(taz)2(pzMe2), HB(taz)2(pzPh), HB(taz)(pz)2}; the heteroscorpionate rhodaboratrane [Rh{B(taz)2(pzMe2)} {HB(taz)2(pzMe2)}] is the only isolable product from the reaction of [{Rh(nbd)(μ-Cl)}2] with K[HB(taz)2(pz Me2)]. Carbonylation of the cod complexes gave a mixture of [Rh(CO)2Tx] and [(RhTx)2(μ-CO)3] which reacts with PR3 to give [Rh(CO)(PR3)Tx] (R = Cy, NMe 2, Ph, OPh). In the solid state the complexes are square planar with the particular structure dependent on the steric and/or electronic properties of the scorpionate and ancillary ligands. The complex [Rh(cod){HB(taz)(pz) 2}] has the heteroscorpionate κ2[N 2]-coordinated to rhodium with the B-H bond directed away from the rhodium square plane while [Rh(cod){HB(taz)2(pzMe2)}] is κ2[SN]-coordinated, with the B-H bond directed towards the metal. The complexes [Rh(CO)(PPh3){HB(taz)2(pz)}] and [Rh(CO)(PPh3){HB(taz)2(pzMe2)}] are also κ2[SN]-coordinated but with the pyrazolyl ring cis to PPh 3; in the former the B-H bond is directed towards rhodium while in the latter the ring is pseudo-parallel to the rhodium square plane, as also found for [Rh(CO)2{HB(taz)2(pzMe2)}]. The analogues [Rh(CO)(PR3){HB(taz)2(pzMe2)}] (R = Cy, NMe2) have the phosphines trans to the pyrazolyl ring. Uniquely, [Rh(CO)(PPh3){HB(taz)2(pzPh)}] is κ2[S2]-coordinated. A qualitative mechanism is given for the rapid ring-exchange, and hence isomerisation, observed in solution.
UR - http://www.scopus.com/inward/record.url?scp=78649693009&partnerID=8YFLogxK
U2 - 10.1039/c0dt00774a
DO - 10.1039/c0dt00774a
M3 - Article
AN - SCOPUS:78649693009
SN - 1477-9226
VL - 39
SP - 11616
EP - 11627
JO - Dalton Transactions
JF - Dalton Transactions
IS - 48
ER -