Oxidative addition of different electrophiles with rhodium(I) carbonyl complexes of unsymmetrical phosphine–phosphine monoselenide ligands

Dimeric chlorobridge complex [Rh(CO) 2 Cl] 2 reacts with two equivalents of a series of unsymmetrical phosphine–phosphine monoselenide ligands, Ph 2 P(CH 2 ) n P(Se)Ph 2 { n = 1( a ), 2( b ), 3( c ), 4( d )}to form chelate complex [Rh(CO)Cl(P∩Se)] ( 1a ) {P∩Se = η 2 ‐(P,Se) coordinated} and non‐chelate complexes [Rh(CO) 2 Cl(P∼Se)] ( 1b–d ) {P∼Se = η 1 ‐(P) coordinated}. The complexes 1 undergo oxidative addition reactions with different electrophiles such as CH 3 I, C 2 H 5 I, C 6 H 5 CH 2 Cl and I 2 to produce Rh(III) complexes of the type [Rh(COR)ClX(P∩Se)] {where R = C 2 H 5 ( 2a ), X = I; R = CH 2 C 6 H 5 ( 3a ), X = Cl}, [Rh(CO)ClI 2 (P∩Se)] ( 4a ), [Rh(CO)(COCH 3 )ClI(P∼Se)] ( 5b–d ), [Rh(CO)(COH 5 )ClI‐(P∼Se)] ( 6b–d ), [Rh(CO)(COCH 2 C 6 H 5 )Cl 2 (P∼Se)] ( 7b–d ) and [Rh(CO)ClI 2 (P∼Se)] ( 8b–d ). The kinetic study of the oxidative addition (OA) reactions of the complexes 1 with CH 3 I and C 2 H 5 I reveals a single stage kinetics. The rate of OA of the complexes varies with the length of the ligand backbone and follows the order 1a > 1b > 1c > 1d . The CH 3 I reacts with the different complexes at a rate 10–100 times faster than the C 2 H 5 I. The catalytic activity of complexes 1b–d for carbonylation of methanol is evaluated and a higher turnover number (TON) is obtained compared with that of the well‐known commercial species [Rh(CO) 2 I 2 ] − . Copyright © 2006 John Wiley & Sons, Ltd.