Activation of SOF₂ at Rh Pincer Complexes: Ligand Backbone Versus Metal Centred Reactivity

Deprotonation of the complexes [Rh(P H NNEP t Bu )X] ( 1 , a: E = N, X = Cl; b : E = O, X = Cl; c : E = O, X = I) (P H NNNP t Bu = {2,6‐( t Bu 2 P NH)( t Bu 2 P NH)(C 5 N H 3 )‐ κ 3 P,N,P}, P H NNOP t Bu = {2‐( t Bu 2 P O)‐6‐( t Bu 2 P NH)(C 5 N H 3 )‐ κ 3 P, N,P}), led to the formation of the anionic Rh species [Rh(P * NNEP t Bu )(KX)] ( 2a–c ) (P * NNNP t Bu = {2‐( t Bu 2 P N=)‐6‐( t Bu 2 P NH)(C 5 N H 3 )‐ κ 3 P,N,P}, P * NNOP t Bu = {2‐( t Bu 2 P O)‐6‐( t Bu 2 P N=)(C 5 N H 3 )‐ κ 3 P,N,P}), which are stabilized by a K + ion. On employing a crown ether [Rh(P * NNOP t Bu )(Cl)][K(18‐crown‐6)] 2b’ can be isolated, which is characterized by single crystal X‐ray diffraction studies. Treatment of 2a–c with SOF 2 resulted in S─F bond activation either via a ligand cooperated mechanism forming [Rh(P SOF NNEP t Bu )X] ( 3a–c ) (P SOF NNNP t Bu = {2‐( t Bu 2 P N(SOF))‐6‐( t Bu 2 P NH)(C 5 N H 3 )‐ κ 3 P,N,P}, P SOF NNOP t Bu = {2‐( t Bu 2 P O)‐6‐( t Bu 2 P N(SOF))(C 5 N H 3 )‐ κ 3 P,N,P}) where the S(O)F group is stabilized at the ligand backbone, or alternatively to give two structural isomers of [Rh(P * NNEP t Bu )(SOF)X] ( 4a–c ) via oxidative addition at the metal center under elimination of KF. The also generated minor products are identified as hydrolysis products and their derivatives. At low temperatures, the complex 3b is formed as the exclusive product when 2b is treated with SOF 2 . The transformation of 3b into the structural isomers of 4b is achieved in the presence of free SOF 2 and is monitored via nuclear magnetic resonance spectroscopy. Treatment of 3b with HF recovered the SOF 2 and gave 1b , while addition of CO to 3b led to the formation of [Rh(P * NNOP t Bu )(CO)] ( 8 ) through elimination of SOClF.