Andrew S. Weller

Sterically encumbered charge-compensated carbaboranes: Synthesis and reactivity molecular structures of 7-Ph-11-SMe2-7,8-nido-C2B9H10 and 1-Ph-3,3-(CO) 2-7-SMe2-3,1,2-closo-RhC2B9H8

Abstract Reaction between K[7-Ph-7,8-nido-C2B9H11] and dmso in H2SO4 affords a mixture of the isomers 7-Ph-9-SMe2-7,8-nido-C2B9H10 (1a) and 7-Ph-11-SMe2-7,8-nido-C2B9H10 (1b). Similarly, starting from K[7,8-Ph2-7,8-nido-C2B9H10], the diphenyl analogue 7,8-Ph2-9-SMe2-7,8-nido-C2B9H9 (2) was produced. These three new nido carbaboranes have been characterised spectroscopically, including 11B-11B COSY and 1H-1H NOESY experiments, and by a single crystal diffraction study on 1b. Deprotonation of 1a followed by addition of [RhCl(CO)2]2 affords the carbametallaborane 1-Ph-3,3-(CO)2-7-SMe2-3,1,2-closo-RhC2B9H9 (3), characterised by IR and 1H and 11B NMR spectroscopies and by a crystallographic study.

FERROCENYL SUBSTITUTED CARBORANES : SYNTHESIS AND CHARACTERISATION

Abstract The reaction between ethynyl ferrocene and decaborane affords the new ferrocenyl substituted carborane 1-{Fc}-1,2-closo-C2B10H11 1 [Fc=(η5-C5H4)Fe(η5-C5H5)]. Deboronation of 1 gives K[7-{Fc}-7,8-nido-C2B9H11] 2, and subsequent metallation, using the {Ru(p-cym)} fragment, affords the novel ferrocenyl substituted ruthenacarborane 1-{Fc}-3-(p-cym)-3,1,2-closo-RuC2B9H10 3 (p-cym=1-Me–C4H4-4-iPr). Reaction between bis(methylethynyl)ferrocene and decaborane affords the bis carborane substituted ferrocene 1,1′-{Fc′}-{2-Me-1,2-closo-C2B10H10}2, 4 [Fc′=(η5-C5H4)Fe(η5-C5H4)]. Deboronation of 4 results in the formation [HNMe3]2[7,7′-{Fc′}-{7-Me-7,8-nido-C2B9H10}2], 5, isolated as a syn and anti diastereoisomeric pair. Metallation of 5 affords the trimetallic ruthenacarborane 1,1-{Fc′}-{2-Me-3-(p-cym)-3,1,2-closo-RuC2B9H9}2 3, as a mixture of syn and anti diastereoisomers. All the new complexes have been fully characterised by multinuclear NMR and micro-analysis, and for compounds 1, 3, 4 and anti-6 by a single crystal X-ray study.

Reversible on/off switching of CH ⇀ Rh interactions in rhodathiaboranes with "anomalous" electron counts. Synthesis and molecular structure of [(Ph3P) 2N][1-dppe-1,2-closo-RhSB9H9]

Abstract Reconsideration of the “rule-breaking” rhodathiaborane 8,8-(Ph 3 P) 2 -8,7- nido -RhSB 9 H 10 , its 9-OEt and dppe analogues, reveals the existence of agostic CH ⇀ Rh (from PPh 3 ) bonding which accounts for its molecular structure. Deprotonation [H(9, 10) bridging proton] “switches off” this agostic bonding and affords a closo cluster. This structural change is fully reversible on reprotonation.

Charge-compensated carbarhodaboranes. Synthesis and molecular structures of 3-L-3,3- (I) 24-SMe2-3,1,2-closo-RhC2B9H10, L = CO or PPh3

Abstract Reaction of 3,3- (CO) 2-4-SMe2-3,1,2-closo-RhC2B9H10 with iodine results in the formation of 3- (CO) -3,3- (I) 2-4-SMe2-3,1,2-closo-RhC2B9H10, 1. Reaction between 1 and PPh3 results in substitution of the carbonyl group to afford 3-PPh3-3,3- (I) 2-4-SMe2-3,1,2-closo-RhC2B9H10, 2. Both new compounds have been fully characterised by multinuclear NMR spectroscopy and also by a single crystal X-ray diffraction studies.

8-[1,2-bis(diphenylphosphino)ethane]9,10-μ-hydrido-8-rhoda-7-thia-nido-undecaborane(10)dichloromethane (2/1)

The solid-state structure of the title compound, [Rh(B 9 H 10 S)(C 26 H 24 P 2 )].0.5CH 2 Cl 2 , has a nido cluster geometry but, apparently, only a close electron count. This anomaly is rationalized in terms of long range ortho-phenyl agostic C-H...Rh interactions.