No abstract

Crystals of the title compound are orthorhombic, a = 7*265(2), b = 7-325(2), c = 13.286(5) 8, Z = 4, space group Pnma. The structure was determined from X-ray counter data and refined by full-matrix least-squares calculations to R 0.040 for 527 observed reflections. The six-co-ordinate indium lies on a mirror plane and is bonded to two approximately trans-methyl groups, which also lie in the mirror plane, and four oxygen atoms. A bidentate acetate group lies across the mirror plane, with In-0 2-371 (5) A, while two weaker bridging contacts from different adjacent acetate groups with In-0 2.600(5) A, serve to link the structure as a linear polymer. These bond length differences are unexpected since in a compound of this type the bridge bonds would be expected to be shorter than those of the bidentate acetate.

The crystal structure of tris(cyclopentadienyl)indium(III), InOCsHs^, has been determined at -100°u sing X-ray counter data. The compound is orthorhombic with space group P2,2,2,; the cell dimensions are a = 9.616 (1) Á, b = 9.702 (1) Á, c = 13.407 (2) A, dm = 1.6 (1) g/cm8, and Z = 4. The structure was solved using the Patterson function and refined by full-matrix least-squares techniques to give a value of R = 0.036 and wR = 0.039 for the 1587 observed reflections. The structure consists of infinite polymeric chains with each chain unit comprised of an indium atom linked to two terminal and two bridging cyclopentadienyl groups. These cyclopentadienyl groups give rise to a slightly distorted In-C, tetrahedral environment around the indium atom. Each bridging group is shared between two indium atoms related by a twofold screw axis along b. The indium-carbon bond lengths are 2.24 (1) Á for the terminal groups and 2.37 (1) and 2.47 (1) Á for the two contacts with the bridging groups. * y z U In 0.13432(5) 0.17170(5) 0.21570(4)** Ci (a) -0.0577 (8) 0.3252 (10) 0.2097 (8) ** C2(a) 0.0259 (9) 0.4372 (9) 0.2305(8) ** C3(a) 0.0122 (10) 0.4732 (9) 0.3308(7) ** C4(a) -0.0815(12) 0.3788(10) 0.3745(8) ** Ce(a) -0.1265(11) 0.2915(8) 0.3022 (10) ** Ci(b) 0.2659(9) 0.1958(9) 0.0787 (7) ** C2(b) 0.1649 (11) 0.2258 (10) 0.0062 (7) ** C3(b) 0.1677 (10) 0.3620 (11) -0.0119 (6) ** C4(b) 0.2741 (10) 0.4223 (10) 0.0461 (7) ** C5(b) 0.3356 (8) 0.3224(12) 0.0992 (6) ** Ci(c) 0.2398(10) 0.1412 (11) 0.3628 (7) ** C2(c) 0.3441(11) 0.0498 (8) 0.3265(8) ** C3(c) 0.4646 (11) 0.1231 (11) 0.3144(8) ** C4(c) 0.4419 (11) 0.2597(11) 0.3467 (10) ** C=(c) 0.3093 (12) 0.2703 (11) 0.3757(9) ** Notes Contribution from the Department of Chemistry,

BS8 I TS Cyclic voltammetry shows that [Rh,(CO),(p-L'),] [l, L' = RNNNR, R = p-tolyl; 2, L' = R'NC(Me)NR', R' = Ph], [Rh,(CO),b(p-RNNNR),] (3, L = PPh, or CNBut), [Rh,(CO),(PPh,)L{p-R'NC(Me)NR'},] (4, L = CO), [Rh,(q4-diene),(p-RNNNR),] [5, diene = nbd (norborna-2,5-diene) or cod (cyclo-octa-lr5-diene)], and [Rh,(CO),(CNBut)(p-RNNNR),] (6) undergo at least t w o diff usion-controlled one-electron oxidations at a platinum bead electrode in CH,CI,. The first process is reversible for all of the complexes and corresponds to the formation of a monocation with a [Rh,I3+ core. The second step is fully reversible only for ( l ) , (3, L = PPh,), and (5, diene = nbd), and for the first two of these complexes a third reversible oxidation wave is also observed. The paramagnetic monocations (3+, L = PPh, or CNBut), (4+, L = CO), and ( 5 + , diene = nbd) have been isolated as stable hexafluorophosphate salts via the oxidation of the appropriate neutral complex with either [N,C,H,F-p] [PF,] or [Fe(q-C,H,),] [PF,] in CH,CI,. The related complex [Rh,(CO),(p-dppm)(p-RNNNR),] [PF,] ( 7 + , dppm = Ph,PCH,PPh,) was also prepared, by the [Fe(q-C,H,),] [PF,] oxidation of a mixture of (1) and dppm. The tricarbonyl (4', L = CO) undergoes substitution with Lewis bases, L, to give the cationic dicarbonyls [4+, L = PPh,, AsPh, or P(OPh),] which are readily reduced by "Bun4] [BH,] in CH,CI, to give the otherwise inaccessible neutral species [4, L = PPh,, AsPh,, or P(OPh),]. The chemistry of dirhodium complexes continues to attract considerable attention.,^^ The three basic structural types, (A)-* Throughout this paper, diffusion-controlled waves show i/vf constant for scan rates 50 < v < 500 mV s-'; reversibility is characterised by iol/ired = 1 (over the same range of scan rates). Numerical data are given only when necessary.

As(C6Hs)4] 3 [In(NCS)6], M= 1613, monoclin-