REACTIONS OF PRIMARY AND SECONDARY SILANES WITH BINUCLEAR RHODIUM COMPLEXES - FORMATION OF MU-SILYLENE COMPLEXES AND P-SI BONDS WITH FACILE P-C BOND-CLEAVAGE

A series of bis(¼-SiRH) complexes Rh2(¼-SiRH)2(CO)2(dpEm)2 (E = P: 3a, R = Ph; 3b, R = Et; 3c, R = n-C6H13; and E = As: 6a, R = Ph; 6b, R = Et; 6c, R = n-C6H13) has been synthesized from the reaction of the corresponding primary silane RSiH3 and Rh2(¼-H)2(CO)2(dpEm)2 (1, E = P; 4, E = As). The bis ¼-SiRH complexes 3 and 6 are characterized by 1H and 31P{1H} NMR and IR spectroscopies and for the Et and Ph derivatives, 3b and 3a, respectively, by X-ray crystallography. Crystallographic data for 3b: C2/c; a = 24.184 (5) Å, b = 9.948 (3) Å, c = 24.059 (5) Å; β = 114.49 (2)° Z = 4; dcalcd = 1.45 g/cm3 R = 0.034, Rw = 0.045. The structure determination of 3b shows it to be a “cradle-like” structure with a Rh-Rh bond of 2.814 (1) Å and bridging SiEtH ligands. Each Rh center posesses an approximately square pyramidal coordination geometry ignoring the stereochemical influence of the Rh-Rh bond. In the reaction of 1 with RSiH3, an intermediate has been identified as Rh2(μ-SiRH)(H)2(CO)2(dppm)2 (2a, R = Ph; 2b, R = Et; 2c, R = n-C6H13) on the basis of spectroscopic data. This intermediate isfluxional with exchange occurring between Si-H and Rh-protons, presumably by facile reductive elimination/oxidative addition of Si-H bonds to the Rh centers. For the dpam system 4, different intermediates of the type Rh2(μ-SiRH)(SiRH2)(H)3(CO)2(dpam)2 (5a, R = Ph; 5b, R = Et; 5c, R = n-C6H13) are observed in the reaction with RSiH3. Secondary silanes RR'SiH2 react with 1 to produce initially the μ-SiRR' dihydride intermediates Rh2(μ-SiRR')(H)2(CO)2(dppm)2 (9a, R = R' = Me; 9b, R = R' = Et; 9c, R = Me, R' = Ph) but ultimately givea new type of complex in which P-C cleavage and P-Si bond formation have occurred. These complexes are of the formula Rh2(μ-H)(CO)2(dppm)(Ph2PCH2PPhSiRR')(10a, R = R' = Me; 10b, R = R' = Et; 10c, R = Me, R' = Ph)and have been characterized by 1H and 31P{1H) NMR and IR spectroscopies, and for 10b by X-ray crystallography. X-ray data for 10b: P21; a = 11.387 (2) Å, b = 18.959 (3) Å, c = 13.354 (2) Å β = 112.50 (1)°; Z = 2; dcalcd = 1.30 g/cm3; R = 0.029, Rw = 0.041. In a related reaction, the tricarbonyl complex Rh2(CO)3(dppm)2 (7) reacts with RSiH3 leading initially to the formation of 2 followed by conversion to the μ-CO complex Rh2(μ-SiRH)(μ-CO)(CO)2(dppm)2 (8) which can also form by placing a solution of 2 under CO. © 1990, American Chemical Society. All rights reserved.