Ruthenium (II) complexes of the chelating phosphine borane H 2 ClB Æ dppm Nicolas Merle, Christopher G. Frost, Gabriele Kociok-Ko ¨hn, Michael C. Willis, Andrew S. Weller * Department of Chemistry, University of Bath, Bath BA2 7AY, UK Received 11 November 2004; accepted 24 January 2005 Available online 17 March 2005 Abstract Reaction of H 2 ClB Æ PPh 2 CH 2 PPh 2 (H 2 ClB Æ dppm) with ½RuCp  ðNCMeÞ 3 ½BAr F 4 ðBAr F 4 ¼½Bf3; 5-ðCF 3 Þ 2 C 6 H 3 g 4   Þ results in displacement of all three acetonitrile ligands and the formation of ½RuCp  ðg 2 -H 2 ClB  dppmÞ½BAr F 4  (1), which has been character- ised crystallographically. Reaction with carbon monoxide results in a change from g 2 to g 1 of the borane ligand to afford ½RuCp  ðCOÞðg 1 -H 2 ClB  dppmÞ½BAr F 4  (2). Compound 1 undergoes H/D exchange under a D 2 atmosphere to afford ½RuCp  ðg 2 -D 2 ClB  dppmÞ½BAr F 4 , while 2 does not. Ó 2005 Elsevier B.V. All rights reserved. Keywords: Ruthenium; Borane; Hemi-labile; Co-ordinatively unsaturated 1. Introduction Phosphine boranes, such as H 3 B Æ PR 3 , are valance isoelectronic with alkanes [1]. This relationship has been elegantly exploited by Shimoi in the isolation of ana- logues of elusive transition metal alkane complexes. For example, r-alkane complexes such as Cr(CO) 5 (al- kane) [2] and ReCp(CO) 2 (C 5 H 10 ) [3] have a limited life- time and have only been characterised spectroscopically; while the related phosphine borane complexes, such as Cr(CO) 5 (H 3 B Æ PMe 3 ) [4] and MnCp(CO) 2 (H 3 B Æ PMe 3 ) [5] (structural type A, Scheme 1), are relatively stable at room temperature allowing them to be crystallo- graphically characterised. However, these latter com- plexes are not completely robust and suffer from spontaneous decomposition, removal of the borane un- der a vacuum or substitution by another ligand, e.g. CO liberated in the initial synthesis [4]. Incorporating the borane into a bidentate, chelating ligand has the effect of stabilising the resulting complex towards loss of borane, in a similar manner to the stabil- isation afforded to the MH 3 C linkage in agostic com- plexes compared with intermolecular r-complexes [6]. Thus, the chelating phosphine borane H 3 B Æ PPh 2 - CH 2 PPh 2 (H 3 B Æ dppm) [7] (structure B Scheme 1) forms stable complexes that do not suffer from spontaneous decomposition or facile displacement of the M HB interaction. Nido-Rh(g 2 -H 3 B Æ dppm)(SB 9 H 10 ) [8] Cr(CO) 4 (g 1 -H 3 B Æ dppm) [9], [Rh(cod)(g 2 -H 3 B Æ dppm)]- [PF 6 ] [10] are examples of such complexes. 1 Coordina- tion compounds of the chelating diborane ligand B 2 H 4 Æ (PMe 3 ) 2 (C) have also been reported, and this li- gand can either adopt a monodentate or a bidentate binding mode such as Cr(CO) 5 {g 1 -B 2 H 4 Æ (PMe 3 ) 2 } [1,11] and [Cu{g 2 -B 2 H 4 Æ (PMe 3 ) 2 } 2 ](I) [12]. We have 0022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2005.01.048 * Corresponding author. E-mail address: a.s.weller@bath.ac.uk (A.S. Weller). 1 ‘‘g x ’’ refers to the coordination mode of the phosphine–borane fragment with the metal centre. Implicit is that the other phosphine is always bound to the metal centre. Journal of Organometallic Chemistry 690 (2005) 2829–2834 www.elsevier.com/locate/jorganchem