Bi- and tri-metallic Rh and Ir complexes containing click derived bis- and tris-(pyrazolyl-1,2,3-triazolyl) N-N' donor ligands and their application as catalysts for the dihydroalkoxylation of alkynes.

摘要: A series of bi-topic and tri-topic pyrazolyl-1,2,3-triazolyl donor ligands (1a–d; 1a–c = 1,X-bis((4-((1H-pyrazol-1-yl)methyl)-1H-1,2,3-triazol-1-yl)methyl)benzene (X 2, 3 4; o-C6H4(PyT)2, m-C6H4(PyT)2 p-C6H4(PyT)2) 1d 1,3,5-tris((4-((1H-pyrazol-1-yl)methyl)-1H-1,2,3-triazol-1-yl)methyl)benzene, 1,3,5-C6H3(PyT)3) were conveniently synthesised in ‘one pot’ reactions using the Cu(I) catalysed ‘click’ reaction. Rh(I), Ir(I), Rh(III) Ir(III) complexes with 1a–d general formulae C6H6−n[(PyT)M(CO)2]n[BArF4]n (M Rh, Ir; n 3; 2a–d; 3a–d) C6H6−n[(PyT)MCp*Cl]n[BArF4]n 4a–d; 5a–d) fully characterised. In solution each bi- or tri-metallic 4a–d 5a–d exists as a mixture two (4a–c, 5a–c) three (4d 5d) diastereomers due to presence chiral centre at metal these complexes. The solid state structures 2b–c 4a determined by single crystal X-ray crystallography showed that bidentate arm multitopic coordinates Rh Ir fashion via pyrazolyl-N2 1,2,3-triazolyl N3′ donors. intermetallic distances vary from 8.66 15.17 A. These assessed catalysts for dihydroalkoxylation alkynes cyclisation 2-(5-hydroxypent-1-ynyl)benzyl alcohol, S, spiroketals, 2,3,4,5-tetrahydro-spirol[furan-2,3′-isochroman], P1, 3′,4′,5′,6′-tetrahydro-spiro[isobenzofuran-1(3H),2′(2H)pyran], P2, model Rh(I) (2a–d), highest TOF 2052 h−1 complex 2d, most active when compared other under investigation here. Ir(I) (3a–d) moderately same transformation. No significant enhancement catalytic reactivity was observed trimetallic (2a–d) their monometallic analogues. much more efficient this transformation than analogues, suggesting some cooperativity. Rh(III), 4a–d, Ir(III), 5a–d, not