Coordination Features of a Hybrid Scorpionate/Phosphane Ligand Exemplified with Iridium

Abstract

Although the pentacoordinated complex [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(cod)] (1; pz=pyrazolyl, cod=1,5-cyclooctadiene), isolated from the reaction of [{Ir(mu-Cl)(cod)}(2)] with [Li(tmen)][B(allyl)(CH(2)PPh(2))- (pz)(2)] (tmen=N,N,N',N'-tetramethylethane-1,2-diamine), shows behavior similar to that of the related hydridotris(pyrazolyl)borate complex, the carbonyl derivatives behave in a quite different way. On carbonylation of 1, the metal--metal-bonded complex [(Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}CO)(2)(mu-CO)] (2) that results has a single ketonic carbonyl bridge. This bridging carbonyl is labile such that upon treatment of 2 with PMe(3) the pentacoordinated Ir(I) complex [Ir(CO){(pz)B(eta(2)-CH(2)CH=CH(2))(CH(2)PPh(2))(pz)}(PMe(3))] (3) was isolated. Complex 3 shows a unique fac coordination of the hybrid ligand with the allyl group eta(2)-bonded to the metal in the equatorial plane of a distorted trigonal bipyramid with one pyrazolate group remaining uncoordinated. This unusual feature can be rationalized on the basis of the electron-rich nature of the metal center. The related complex [Ir(CO){(pz)B(eta(2)-CH(2)CH=CH(2))(CH(2)PPh(2))(pz)}(PPh(3))] (4) was found to exist in solution as a temperature-dependent equilibrium between the cis-pentacoordinated and trans square planar isomers with respect to the phosphorus donor atoms. Protonation of 3 with different acids is selective at the iridium center and gives the cationic hydrides [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(CO)H(PMe(3))]X (X=BF(4) (5), MeCO(2) (6), and Cl (7)). Complex 7 further reacts with HCl to generate the unexpected product [Ir(CO)Cl{(Hpz)B(CH(2)PPh(2))(pz)CH(2)CH(Me)}(PMe(3))]Cl (9; Hpz=protonated pyrazolyl group) formed by the insertion of the hydride into the Ir-(eta(2)-allyl) bond. In contrast, protonation of complex 4 with HCl stops at the hydrido complex [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(CO)H(PPh(3))]Cl (8). X-ray diffraction studies carried out on complexes 2, 3, and 9 show the versatility of the hybrid scorpionate ligand in its coordination.

Rhodium and Iridium Complexes with a New Scorpionate Phosphane Ligand

“…The new ligand [(allyl) 18 The ligand brings together hard N-donor and soft P-and C-donor groups, which makes the study of its coordination chemistry to transition metals very attractive, since it can accommodate metallic fragments in different ways. The ligand has been synthesized as the Hydrogen atoms and solvent of crystallization have been removed and only the ipso carbon atoms of the phenyl groups are shown for clarity.…”

Palladium and iridium complexes with a N,P,N-bis(pyridine)phenylphosphine ligand

“…Moreover, although the chemistry of iridium complexes containing tridentate ligands such as P,C,Ppincer 27 or tris(pyrazolyl)borate ligands 26 characterized iridium compounds bearing a chelated N,P,Nligand have been reported to date. 29, 37 The 1 : 2 reaction between the iridium(I) precursor [Ir(m-Cl)(cod)] 2 and N py PN py afforded an air-sensitive orange compound in high yield. Although the attempts to get crystals suitable for X-ray diffraction failed, the formation of a new complex of formula [IrCl(cod)(N py PN py )] ( 6) was inferred from spectroscopic and elemental analysis data.…”

Copper Complexes of Mono‐ and Ditopic [(Methylthio)methyl]borates: Missing Links and Linked Systems En Route to Copper Enzyme Models

“…Treatment of the monotopic tripod [5] À with CuCl and CuBr 2 results in the formation of complexes K[Cu (5) ((N 2 P), [13,14] (NP 2 ) [15] ) or nitrogen and sulfur donors ((N 2 S), [16] (NS 2 ) [17][18][19][20][21][22] ). These derivatives are most interesting, because they allow a smooth modulation of the coordination environment between the extremes (N 3 ) and (P 3 )/(S 3 ).…”