The structures of the large neutral boranes 2,2'-bi(nido-decaboranyl), 2,2'-(B10H13)2, m.p. 178 "C, and 2,6'bi(nido-decaboranyl), 2,6'-( B,0H13),, m.p. 154 "C, have been established by single-crystal X-ray diffraction.The 2,2' isomer is tetragonal, space group /4,cd, with a = 11.901 (3), c = 23.1 35(4) A, molecular symmetry Cz ; the 2,6' isomer is orthorhombic, space group Pbca, with a = 14.673(3), b = 19.765(4), and c = 11.580(3) A.The intercluster B-B bond lengths are respectively 1.692(3) and 1.679(3) A, and there is a lengthening of 0.01 5 A of the adjacent cluster B-B distances when compared with the corresponding distances in decaborane(l4) itself.The lH-{llB) and llB n.m.r. behaviour of the two isomeric conjuncto-boranes has been investigated and the results for the 2 2 ' isomer are discussed in some detail. Infrared and U.V. spectroscopic data are presented. The unambiguous determination of the structures permits a discussion of possible synthetic mechanisms. 1980 791 26 nimol) recovered by sublimation at ca. 60 "C (15 Pa).

The alkaline earth copper tetra-silicates, blue pigments, are interesting infrared phosphors. The Ca, Sr, and Ba variants fluoresce in the near-infrared (NIR) at 909, 914, and 948 nm, respectively, with spectral widths on the order of 120 nm. The highest quantum yield / reported thus far is ca. 10%. We use temperature measurements in sunlight to determine this parameter. The yield depends on the pigment loading (mass per unit area) x with values approaching 100% as x ! 0 for the Ca and Sr variants. Although maximum quantum yield occurs near x ¼ 0, maximum fluorescence occurs near x ¼ 70 g m À2 , at which / ¼ 0.7. The better samples show fluorescence decay times in the range of 130 to 160 ls. The absorbing impurity CuO is often present. Good phosphor performance requires long fluorescence decay times and very low levels of parasitic absorption. The strong fluorescence enhances prospects for energy applications such as cooling of sunlit surfaces (to reduce air conditioning requirements) and luminescent solar concentrators.

No abstract

The reaction of cis-[PtCI,( PMe,Ph)2] with an excess of [B,H14] gives 4,4-bis(dimethylphenylphosphine)arachno-4-platinanonaborane, [4,Ph),-4-PtB8Hl,],(I), in high yield. The pale yellow crystals aremonoclinic, space group C2/c, with a = 1.977 1 (8), b = 1.302 5(4), c = 1.977 3(4) nm, p = 110.99(3)", Z = 8, and the molecular structure is that of a nine-vertex arachno-platinanonaborane in which the B, unit shows trihaptobonding to the metal centre. The compound is also formed in lower yield from several other polyhedral borane derivatives. The 14-vertex bis(dimethylphenylphosphine)bis-~-(24-~-nido-hexaboranyl)-diplatinum(P?-P?), [Pt2(B6HB),(PMezPh),], is also formed in moderate yield from the [BBH14]-reaction, and this offers the most convenient route yet established for its preparation. Treatment of (I) with KH followed by cis-[PtCI,( PMe,Ph),]gives the very stable diplatinum compound 6,6,9,9-tetrakis(dimethylphenylphosphine)-arachno-6,9-diplatinadecaborane, [6,6,9,9-( PMe2Ph)4-6,9-Pt2BsH,,], (11). The colourless crystals are monoclinic, space group C2/c, with a = 1.376 2(3), b = 1.510 5(4), c = 1.921 O(3) nm, p = 92.59(2)', and Z = 4; the molecular structure is that of an arachno-diplatina-decaborane which features a bis(trihapt0) B, unit. It is topologically similar to, but not identical with, the arachna-decaborane anion [B10H14]2-. The 'H, l*B, 31P, and lssPt n.m.r. behaviour of both title compounds has been investigated in detail using both single and double resonance techniques, and a number of important structural correlations emerge. (iii)Phosphorus-carbon 184.8( 12) F[i{zi%) 188.1(13) P ( l ) -C ( l ) 182.8(9) ~~: ~> [ ~] 183.2(12) P(2)-C( 11) 183.1 (13) 185.4( 14) (iv) Other C-C(Ph) 136.6-mean 140.1 143.3 (1 8) C-C(Ph)TABLE 3 Angles (") between interatomic vectors for (I) with estimated standard deviations in parentheses(i) At t h e platinum atom P( l)-Pt(4)-P(2) 95.4( 1) P( 1)-Pt(4)-B( 1) 127.9(4) P(2)-Pt(4)-B( 1) 130.1(3) P( l)-Pt(4)-B(5) 91.1 (3) P( 2)-Pt (4)-B( 9) 8 7.6( 4) P( 1)-Pt (4)-B( 9) 1 75.5( 4) P( 2)-Pt (4)-B (5) 1 70.9 (4) B( l)-Pt(4)-B(5)