Rhodium(I) and Rhodium(III) Complexes Formed by Coordination and CH Activation of Bulky Functionalized Phosphanes

Abstract

Abstract The reaction of [{RhCl(C 8 H 14 ) 2 } 2 ] ( 2 ) with i Pr 2 PCH 2 CH 2 C 6 H 5 (L 1 ) led, via the isolated dimer [{RhCl(C 8 H 14 )(L 1 )} 2 ] ( 3 ), to a mixture of three products 4 a – c , of which the dinuclear complex [{RhCl(L 1 ) 2 } 2 ] ( 4 a ) was characterized by Xray crystallography. The mixture of 4a – c reacts with CO, ethene, and phenylacetylene to give the square‐planar compounds trans ‐[RhCl(L)(L 1 ) 2 ] (L=CO ( 5 ), C 2 H 4 ( 6 ), CCHPh ( 9 )). The corresponding allenylidene(chloro) complex trans ‐[RhCl(CCCPh 2 )(L 1 ) 2 ] ( 11 ), obtained from 4 a – c and HCCC(OH)Ph 2 via trans ‐[RhCl{CCHC(OH)Ph 2 }(L 1 ) 2 ] ( 10 ), could be converted stepwise to the related hydroxo, cationic aqua, and cationic acetone derivatives 12 — 14 , respectively. Treatment of 2 and [{RhCl(C 2 H 4 ) 2 } 2 ] ( 7 ) with two equivalents of t Bu 2 PCH 2 CH 2 C 6 H 5 (L 2 ) gave the dimers [{RhCl(C 8 H 14 )(L 2 )} 2 ] ( 15 ) and [{RhCl(C 2 H 4 )(L 2 )} 2 ] ( 16 ), which both react with L 2 in the molar ratio of 1:2 to afford the five‐coordinate aryl(hydrido)rhodium( III ) complex [RhHCl(C 6 H 4 CH 2 CH 2 P t Bu 2 ‐ κ 2 C , P )(L 2 )] ( 17 ) by CH activation. The course of the reactions of 17 with CO, H 2 , PhCCH, HCl, and AgPF 6 , leading to the compounds 19–21, 24 , and 25 a , respectively, indicate that the coordinatively unsaturated isomer of 17 with the supposed composition [RhCl(L 2 ) 2 ] is the reactive species. Labeling experiments using D 2 , DCl, and PhCCD support this proposal. With either [Rh(C 8 H 14 )( η 6 ‐L 2 ‐ κP ]PF 6 or [Rh(C 2 H 4 )( η 6 ‐L n ‐ κP ]PF 6 ( n =1 and 2) as the starting materials, the corresponding halfsandwich‐type complexes 27, 28 , and 32 were obtained. The nonchelating counterpart of the dihydrido compound 32 with the composition [RhH 2 (P i Pr 3 )( η 6 ‐C 6 H 6 )]PF 6 ( 35 ) was prepared stepwise from [Rh(C 2 H 4 )(P i Pr 3 )( η 6 ‐C 6 H 6 )]PF 6 and H 2 in acetone via the tris(solvato) species [RhH 2 (P i Pr 3 )(acetone) 3 ]PF 6 ( 34 ) as intermediate. The synthesis of the bis(chelate) complex [Rh( η 4 ‐C 8 H 12 )(C 6 H 5 OCH 2 CH 2 P t Bu 2 ‐ κ 2 O , P )]BF 4 ( 39 ) is also described. Besides 4 a , the compounds 17, 25 a , and 39 have been characterized by Xray crystal structure analysis.