Organometallic Rhodium Complexes Containing Peralkylated Arsino(phosphino)methanes as Ligands

The peralkylated arsino(phosphino)methanes R2AsCH2PR2 (R = iPr, Cy) reacted with [{(eta(4)-C8H12)RhCl}(2)] by cleavage of the chloro bridges to give the mononuclear compounds [(RhCl-(eta(4)-C8H12)(kappa(2)-P-R2PCH2AsR2)] (1, 2). In contrast, treatment of the dimeric cyclooctadiene complex with the tBu-substituted derivative tBu(2)AsCH(2)PiPr(2) afforded dinuclear [{(Rh(eta(4)-C8H12)}{Rh(kappa(2)-As,P-tBu(2)AsCH(2)PiPr(2))}(mu-Cl)(2)] (3), the first example of a d(8) transition-metal compound containing a CH2-bridged As/P donor system as a chelating ligand. The X-ray crystal structure of 3 has been determined. Cationic complexes [Rh(eta(4)-C8H12)(kappa(2)-AS,P-R2AsCH2PR'(2))]PF6 (4a, 5a, 6a) were obtained from [{(eta(4)-C8H12)RhCl}(2)], R(2)ASCH(2)PR'(2), and MPF6(M = K, Ag). The corresponding BPh4 salts (4b,5b, 6b) were prepared from the PF6 salts upon metathesis with NaBPh4. The chelate compounds 4-6 reacted with CH2N2 by insertion of CH2 into the Rh-As bond to yield the complexes [Rh(eta(4)-C8H12)(kappa(2)-C,P-CH(2)AS- (R)(2)CH2PR'(2))]PF6 (7-9), which contain a five-membered metallacycle adopting an envelope conformation in the crystal. The reaction of the BPh4 salts 4b and 5b with H-2 gave the half-sandwich-type complexes [(eta 6-C6H5BPh3)Rh(kappa(2)-AS,P-R(2)ASCH(2)PR'(2))] (10;11), in which the tetraphenylborate is coordinated Like a substituted arene to the metal center. Treatment of the PF6 salt 6a with H-2 in the presence of CF3CO2H led to the formation of the unusual dinuclear hydride-bridged complex [{RhH(kappa(2)-As,P-Cy2AsCH2PCy2)}(2)(mu-H)(mu-O2CCF3)(2)]PF6 (12).