Work on recovery of the (NH4)2B10H~0 from the double salt by use of other solvents is in progress. With large excesses of HC1 the reaction gives some free NH4C1 and correspondingly higher quantities of B10H12-(Et2S)2. Several samples have been allowed to react with propargyl bromide, and the expected bromomethylcarborane derivative was ~b t a i n e d .~Muetterties has reported obtaining a bridge-hydrogen structure from the BloHlo2-i o n 6 Dehydration of an aqueous solution of (H30)2B10H10 gave a white solid from which a material could be sublimed. The sublimate showed evidence for bridge hydrogens in its infrared pattern. The unknown had the approximate composition of BloH120H2. He concluded that the solid belonged to the BloH12(base) or B10H13-structural class. A referee has pointed out that the formation of Bl8H22 from B20H18'-plus acid involves opening BloHlo cages. However, degradation with loss of boron also obviously occurred.'Mechanistically the synthesis of BloH12(Et2S)2 from (NH4)2B10H10 can be pictured as just the reverse of the BloHlz(base)z conversion to BloHlo2-derivatives. Hawthorne suggests that this latter conversion occurs by the removal of protons from the bridge positions in the BloH12(base)2 structure, and that the resulting filled two-center orbitals undergo a nucleophilic displacement of the coordinated bases. In our reaction, protons which are presumably supplied via the ethylsulfonium ion, Et2SH+, probably attack in the apex region of the BloHlo2-cage. Nmr studies with deuterium chloride have established that hydrogen exchange occurs at the apex borons.6,8*9 Single crystal X-ray space group is Pbca, with a = 16.9, b = 18.9, c = 14.7 A. The formula weight from these data and the observed density is 61 1 (f 1 %) (calcd for [PtCl(CO)-(P(C2H6)3)2]SiF5: 618; calcd for O.S[PtCl(CO)(P-(C~H&)ZIZS~FB : 566).Although the previous conclusions are now known to be incorrect, the reactions described above are remarkable in several ways. (a) The formation of a platinum carbonyl and BF4-under such mild conditions, presumably by interaction of GF4 with the glass surface in contact with the hydride, is remarkable. It can be related to, but is more extreme than, the ability of the isoelectronic Ir(1) and Rh(1) systems to abstract carbon monoxide from oxygen-containing organic solvents.2t6 (b) The cation is isoelectronic with Vaska's compound2 and may show similar properties. These are being investigated. (c) This is the first reported isolation of the SiF5-ion. Further detailed studies of this species are currently in progress.Acknowledgment.The preparations of BloH12(base)2 derivatives have been reported from reactions of decaborane with soft bases.1v2 These have been converted further to the BloHlo2-structure by action of more or harder base.a We wish to report the synthesis of B10H12(Et2S)2 from (NH4)2B10H10, which is the first time, to our knowledge, that the BloHlo2-cage has been opened to clearly reestablish the decaborane skeleton.This reaction takes on further significance with the recent preparation...

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