REACTIONS OF THE NITRIDOCARBONYL CLUSTER ANION [RH6N(CO)15]-WITH STRONG BASES - SYNTHESIS AND CRYSTAL-STRUCTURE OF THE HYDRIDIC DIANION [RH6(MU-H)N(CO)14]2-

The reaction of the nitridocarbonyl anion [Rh6N(CO)15]-, as its K+ sal t, in water or alcoholic solution with alkali metal hydroxides afforde d the novel hydridic species [Rh6(mu-H)N(CO)14]2-, isolated as the cae sium (2a) and the, bis(triphenylphosphine)iminium (2b) salts. Both spe cies have been investigated by X-ray structural analysis. Compound 2a crystallizes in the hexagonal system, space group P6(3)/mmc (no. 194), with a = b = 11.089(2), c = 12.308(4) angstrom, Z = 2. Compound 2b gi ves monoclinic crystals, space group C2/c (no. 15), with a = 26.896(3) , b = 17.143(6), c = 20.250(2) angstrom, beta = 118.80(1)degrees, Z = 4. The structures were refined on the basis of 355 (2a) and 2170 (2b) significant independent reflections to final R values of 0.0427 and 0. 0491 for 2a and 2b, respectively. The anion contains a trigonal prisma tic cluster centred by the nitrido ligand. The hydrido ligand bridges an interbasal Rh-Rh edge replacing a bridging CO group of the parent a nion [Rh6N(CO)15]-. This substitution causes some stereochemical effec ts which are discussed for 2b; in 2a the anion has essentially the sam e stereochemistry but the interbasal ligands (two CO and one H) are di sordered, due to the presence of a three-fold crystallographic axis.